text:
|Publication number
|Publication type
|Application number
|Publication date
|Oct 11, 1994
|Filing date
|Mar 30, 1993
|Priority date
|Mar 30, 1993
|Fee status
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|Publication number
|Robert L. Byer, Martin M. Fejer, Leslie A. Gordon
|Original Assignee
|The Board Of Trustees Of The Leland Stanford, Jr. University
|Export Citation
|BiBTeX, EndNote, RefMan
|Patent Citations (8), Non-Patent Citations (38), Referenced by (38), Classifications (11), Legal Events (5)
|External Links: USPTO, USPTO Assignment, Espacenet
The research from which this invention emanated was supported wholly or partly by the United States government, and such government may have rights in and to this invention.
The present invention relates to nonlinear optics and, more particularly, to a method using a monolithic monocrystalline material for producing radiation of a selected frequency by quasi-phase-matching, a monolithic monocrystalline material which optimizes nonlinear interactions by quasi-phase-matching, and a method of fabricating the same. It also relates to an optical generator utilizing such material.
The properties of nonlinear materials have many different applications; the invention uses these properties for frequency conversion. That is, nonlinear monocrystalline materials can interact with input radiation to generate output radiation of a frequency different than that of the input radiation. The input and output radiation typically is optical radiation, i.e., radiation having frequencies in the visible range or of other adjacent frequency ranges such as ultraviolet, and infrared. It encompasses the ultraviolet, visible, and near, mid and far infrared frequencies. (The term "crystalline" as used herein without a modifier means "monocrystalline" unless the context indicates otherwise.)
Second harmonic generation is an example of one of the interactions possible in a nonlinear crystalline material. In second harmonic generation, the frequency (ω) of input optical radiation is converted into optical radiation of twice such frequency (2 ω). A sum frequency generator also relies on frequency conversion in a nonlinear crystalline material. In such an arrangement, input beams of two different frequencies (ω1 and ω2) are summed by a nonlinear material to generate optical radiation whose frequency (ω3) is the sum of the frequencies of the two input beams (ω1 +ω2 =ω3). Other common devices utilizing a nonlinear monocrystalline material are optical parametric oscillators, optical parametric amplifiers and difference frequency generators.
Nonlinear frequency conversion in crystalline materials is used to provide a desired frequency which is not conveniently available from an existing source such as an existing laser. For example, it is used to "frequency double" the 10.6 μm radiation (approximately 30 THZ) generated by a CO2 laser, to 5.3 μm (approximately 60 THZ). Currently there is no efficient or high power laser capable of generating the latter frequency. This frequency, however, is highly desirable because the atmosphere is transparent in the 3-7 μm spectral range. Application examples are remote sensing, laser radar and laser countermeasure systems.
Efficient nonlinear frequency conversion requires phase matching as will be described in some detail below. Because the frequency range in conventionally phase-matched crystals is limited by the birefringence available, consideration has been given to quasi-phase-matching as also described below. Reference is made, for example, to the papers entitled "Interactions Between Light Waves in a Nonlinear Dielectric" by J. A. Armstrong et al., Physical Review, Vol. 127, 1962, pp. 1918-1939; "Optical Harmonics and Nonlinear Phenomena" by A. Franken et al., Review of Modern Physics, Vol. 35, 1963, pp. 23-39; "A Quasi-Phase-Matching Technique for Efficient Optical Mixing and Frequency Doubling" by A. Szilagyi et al., J. Appl. Physics, Vol. 47, No. 5, May 1976, pp. 2025-2032; and "Second-Harmonic Generation in GaAs `Stack of Plates` Using High-Power CO2 Laser Radiation" by D. E. Thompson et al., Appl. Phys. Lett., Vol. 29, No. 2, 15 Jul. 1976, pp. 113-115.
Quasi-phase-matching has been successfully achieved in ferroelectric nonlinear crystals in which domains can be inverted. (See "Quasi Phase Matched Second Harmonic Generation of Blue Light in Periodically Poled LiNbO3 " by G. A. Magel et al., Appl. Phys. Lett., Vol. 56, 1990, pp. 108-110; and "Second Harmonic Generation of Green Light in Periodically Poled Planar Lithium Niobate Waveguide" by E. J. Lim et al., Electronic Letters, Vol. 25, 1989, pp. 174-175.) While this approach has been widely used for manufacturing waveguides in lithium niobate and other poleable materials, it is limited in that the technique is not possible in non-poleable materials. That is, a different approach is necessary to alternate the sign of the optical nonlinear coefficient in a non-poleable crystal.
Earlier approaches that have been considered for non-poleable materials required a multitude of thin slices of crystal. (See "A Quasi-Phase-Matching Technique for Efficient Optical Mixing and Frequency Doubling" by A. Szilagyi et al., J. Appl. Physics, Vol. 47, No. 5, May 1976, pp. 2025-2032; and "Second-Harmonic Generation in GaAs `Stack of Plates` Using High-Power CO2 Laser Radiation" by D. E. Thompson et al., Appl. Phys. Lett., Vol. 29, No. 2, 15 Jul. 1976, pp. 113-115.) While good agreement was found between theory and experiment, the work was not continued for several reasons, including excessive reflection, scattering, and absorption losses caused by dust, surface quality and alignment tolerances. Thus, the number of air/material interfaces made this technique impractical. Because of this lack of practicality, those in the art have generally abandoned quasi-phase-matching as a general approach to bulk nonlinear conversion in non-poleable materials.
The present invention relates to a method of using quasi-phase-matching for frequency conversion in a practical way in all bulk nonlinear monocrystalline structures. The invention also provides a monolithic nonlinear monocrystalline material which is especially designed for quasi-phase-matching. In its broad aspects, the method includes providing a material made up of a plurality of adjacent wafers of one or more nonlinear monocrystalline materials that individually are transparent to the frequencies between which it is desired to transfer energy. (As used herein with respect to a material, the terms "transparent" and "low loss" means a material in which absorption of the radiation frequencies in question is not large enough to prevent nonlinear interactions from taking place with useful efficiency.)
Each of the wafers has a dimension along an expected optical path through it, which is selected to provide a desired conversion of energy from input radiation(s) to one or more selected frequencies of output radiation. Most desirably, such dimension of each of the wafers is generally equal to an odd multiple of the coherence length (lc as defined below) in the wafer for the desired energy conversion. Such wafers are bonded together by diffusion bonding to form a single (monolithic) monocrystalline material. Diffusion bonding is the permanent bonding together of adjacent surfaces where generally no foreign substance is present between such surfaces and there is a meaningful exchange or sharing of electrons, atoms, ions or molecules. It is achieved by mating the opposed adjacent faces of the wafers together, applying pressure between the same, and raising the temperature of the resulting stack to a temperature which will cause the meaningful migration between the wafers, and yet not be sufficiently high that the monocrystalline nature of the wafers is destroyed.
The temperature and pressure are maintained while the wafers are mated to one another for a sufficiently long period of time to have the migration occur. The pressure is necessary to prevent an air layer from remaining between the plates.
The method of the invention also includes the step of passing through the resulting material, radiation which will interact with the same nonlinearily to provide the desired output radiation. The invention includes an optical parametric oscillator method based on diffusion bonding quasi-phase-matching, the materials themselves and a method of fabricating the same. An optical generator for producing radiation of about 5.3 μm in wavelength is also provided as part of the invention.
The invention enables the practical use of nonlinear frequency conversion with non-poleable crystals. Thus, with it one can obtain new frequencies and yet take advantage of the many years of development of laser technology already spent. The costly process of inventing and perfecting new laser technology is avoided.
Other features and advantages of the invention either will become apparent or will be described in connection with the following, more detailed description of preferred embodiments of the invention.
With reference to the accompanying drawing:
FIG. 1 is a graph illustrating no phase matching, birefringent phase matching, and 1st and 3rd order quasi-phase-matching;
FIG. 2 is a graph similar to that of FIG. 1 illustrating even order and first order on-off quasi-phase-matching;
FIG. 3 is an enlarged schematic, elevational view of a preferred embodiment of the invention;
FIG. 4 is an optical generator of the invention;
FIGS. 5A and 5B are alternate preferred embodiments of the invention;
FIG. 6 is a graphical view of a tuning curve for a diffusion bonded, quasi-phase-matched (DB-QPM) wedge structure of the invention; and
FIG. 7 is an enlarged schematic view showing a preferred embodiment of the invention, including the combination of both a monolithic monocrystalline material and another optical device.
The following relatively detailed description is provided to satisfy the patent statutes. However, it will be appreciated by those skilled in the art that various changes and modifications can be made without departing from the invention.
The discussion below is fairly complex, and the following definitions and understandings are used to circumvent confusion:
When an interaction is referred to in this application, the interaction of two or more waves with a crystal is meant. For example, first order interaction is the linear response to light i.e. absorption, scattering; the frequency in equals the frequency out. (ω1)in =(ω2)out
A second order interaction involves three waves, either two frequencies in and one out, or one frequency in and two out. (ω1 +ω2)in =(ω3)out or (ω1)in =(ω2 +ω3)out The interaction coefficient is called the second order nonlinear coefficient, and determines how efficiently radiation is converted from the initial frequencies to the final frequencies. An example is second harmonic generation, or doubling the frequency where the two frequencies of the radiation beams in are identical, and the frequency of the radiation out is double the initial frequency of each of the input beams.
A third order interaction involves four waves: three frequencies in and one out, two in and two out, or one in and three out. (ω1 +ω2 +ω3)in =(ω4)out or (ω1 +ω2)in =(ω3 +ω4)out or (ω1)in =(ω2 +ω3 +ω4)out The interaction coefficient is called the third order nonlinear coefficient, and once again determines conversion efficiency.
Conservation of energy determines the interactions possible; the sum of the frequencies before the interaction equals the sum of the frequencies after the interaction. Conservation of momentum, or phase velocity matching, determines which one of those interactions dominates. When it is said that an interaction is phase matched it means that the sum of the wave vectors defined by the interaction equals zero. There is a wave vector, k, for each frequency in the interaction,
where k.sub.ω =ωn.sub.ω /c
for ω: frequency of the light in rad/sec
n: index of refraction of the crystal at the frequency ω
c: speed of light in a vacuum
To efficiently convert from initial frequencies to the final, an interaction must be phase matched as identified below. Without phase matching, the initial and final waves dephase by π radians after propagation through some length of the crystal. At this point, the flow of energy reverses, with the final frequencies depleted and the initial increased. The length of the crystal over which the initial and final waves dephase by π radians is called the coherence length, lc, in this application. The coherence length depends on the crystal properties and the frequencies of the interaction. This situation is illustrated in FIG. 1 for the non-phase-matched curve in the case of second harmonic generation. Every lc the flow of energy reverses between the initial and the final frequencies; therefore, the maximum conversion possible in a non phase matched crystal is obtained in one coherence length, which is the half period of the growth and decay cycle of the final frequencies.
lc =π/Δk
where Δk is the difference between the sum of wave vectors (k) of the initial frequencies and the final frequencies. In the case of very high conversion per layer the optimal thickness of the layer can vary from the above.
The following table provides examples of Δk for different nonlinear interactions. (Each wave vector, k, conserves the sign of the frequency that it represents.)
______________________________________interaction Δk device1______________________________________(ω1 + ω2)in = (ω3)out k3 - k2 - k1 SFG(ω1 + ω1)in = (ω2)out k2 - k1 - k1 SHG(ω1)in = (ω2 + ω3)out k3 + k2 - k1 OPO(ω1 - ω2)in = (ω3)out k3 + k2 - k1 DFG(ω1 + ω2)in = (ω3+ ω4)out k4 + k3 - k2 - k1(ω1)in = (ω2 + ω.sub. 3+ ω4)out k4 + k3 + k2 - k1(ω1 + ω2 + ω3)in = (ω4).sub.out k4 - k3 - k2 - k1______________________________________ 1 SFG = sum frequency generator SHG = second harmonic generator OPO = optical parametric oscillator DFG = difference frequency generator
The subscripts on the k's in the above correspond to the subscripts of the interaction frequencies (ω). The first four examples are second order nonlinear interactions (three wave interactions) and the last three examples are third order nonlinear interactions involving four waves.
If the index of refraction was constant in a crystal, the same for all frequencies, then all interactions would be phase matched; however, the crystal exhibits dispersion and index of refraction does vary as a function of frequency, temperature, and other physical parameters. To offset the effects of dispersion, phase matching can be accomplished one of two ways: birefringent phase matching or quasi-phase matching.
Some crystals are not isotropic; they have different indices of refractions along different crystal axes, and are called birefringent. In this situation, frequencies of different polarizations will experience different indices of refraction. Tuning, or choosing the interaction can be accomplished by varying the temperature of the crystal and, therefore, changing the birefringence and the dispersion, or by changing the angle of propagation of one or more of the frequencies with respect to the crystal axes.
There are limitations to this type of phase matching. If tuning is accomplished by varying the angle of propagation with respect to the crystal axis, it is called "critical" phase matching; this type of phase matching is very sensitive to any angular deviation; therefore, has a very small angular acceptance, and the frequencies experience walk-off: where the electric fields of the initial and the final frequencies slowly separate, gradually reducing conversion efficiency. "Non-critical" phase matching is accomplished by propagating the frequencies at 90� to the optical axis. Tuning is accomplished by varying the temperature. The working range of frequencies of non-critical phase matching is much smaller than critical; however, it is always preferable when possible since it has a much larger angular acceptance and has no birefringent walk-off.
While some technology may be transferred from existing crystals, typically at least 15 years must be invested into developing growth techniques to produce quality crystals. For a crystal to be usable it must, among other properties: a) be low loss over the interaction wavelengths; b) have a sufficiently high optical nonlinear coefficient, and c) have an adequate birefringence to permit phase matching. Since conversion is dependent on the intensity, an ideal crystal must also have good thermal properties: a high damage threshold for high peak powers and high thermal conduction, and small absorption and scattering losses for high average powers.
Only a few crystals can be used for standard birefringent phase matching. For example, second harmonic generation of the output of a CO2 laser has been shown for Te, AgGaSe2, AgGaS2, TlAsSe, Proustite, ZnGeP2, and CdGeAs2. Nonlinear crystals having a single index of refraction, such as GaAs or ZnSe, are not useful for standard phase matching due to their lack of birefringence. However, these crystals can be used, as well as those with birefringence, for harmonic conversion using quasi-phase-matching.
The major constraint for conventional phase matching is birefringence since a birefringent crystal must possess adequate birefringence for the given interactions. Cubic nonlinear crystals, such as GaAs, can not be used for efficient bulk infrared frequency conversion because they do not have birefringence, and, therefore, do not allow birefringent phase matching. However, quasi-phase-matching (QPM) can overcome this limitation.
By periodically modifying the nonlinear coefficient, we introduce an additional wave vector, Km. Conservation of momentum now gives us Δk=Δk-Km where Δk depends on the interaction and was defined previously. We see from this equation that by providing a Km that is equal to the Δk of the interaction, we can achieve a Δk=0. This is quasi-phase-matching.
It is possible to quasi-phase-match a crystal by changing the nonlinear coefficient every lc or odd multiple of lc. This may be accomplished by either reversing the sign of the nonlinear coefficient of the alternating layers, or by alternating layers of material which possess a nonlinear coefficient with layers which have a different (preferably little or no) nonlinear coefficient. Such an alternate layer is inoperative--it could be of a polycrystalline material, but its thickness dimension remains relevant.
We will define the order of the quasi-phase-matched structure (m) as the average modulation with period 2mlc, where m is an integer. (The order of quasi-phase-matching is different than the order of interaction discussed previously.) Modulation is defined here as a complete growth and decay cycle of the final frequency. In this way, a structure composed of layers all one coherence length thick will be referred to as a first order (m=1) quasi-phase-matched (QPM) crystal. Similarly, if it is composed of layers three coherence lengths thick, it will be a third order (m=3) QPM structure. See FIG. i for a comparison of the conversion efficiency of first and third order QPM structures to phase matched and non-phase-matched crystals. While a length of crystal equal to an exact even number of coherence lengths would provide no net energy transfer between the initial and the final frequencies, it is possible to make even (or odd) order composite quasi-phase-matched structures, by alternating layers of one nonlinear coefficient with layers of a different or opposite nonlinear coefficient. If the repeatable period is equal to 2mlc where m is an integer, there always will be a net increase in conversion per layer; the quasi-phase-matched order is m. FIG. 2 illustrates two different approaches used to obtain an effective second order quasi-phase-matched structure--a first and third order mix, which is second order, and a first order (m=1) on-off structure which increases at the same rate as the second order structure.
While it is optimal to change the nonlinear coefficient at odd intervals of the coherence length, this is not the only way to achieve conversion. As long as the domain is not exactly equal to an even multiple of the coherence length, there will be some conversion. Domain sizes can be adjusted at the expense of peak conversion efficiency to increase the bandwidth. Aperiodic modulation can also be used for high conversion efficiency.
In this way, we may build a quasi-phase-matched (QPM) structure specifically for the desired interaction. By using GaAs, or other well known crystals, we can capitalize on twenty years of crystal development. QPM can be used to manufacture crystals structures that are useful throughout any range of the electromagnetic spectrum. The main requirements are that the crystals be transparent over the range of the interaction, the crystals have a sufficiently high nonlinear coefficient and damage threshold, and that there be a way to alter the sign of the nonlinear coefficient in a periodic manner at some odd multiple of coherence lengths. Among the benefits of quasi-phase-matching over birefringent phase matching are: large acceptance angles, large temperature and frequency bandwidths, adaptable to any interactions with frequencies in the transparency ranges of the QPM crystal, no birefringence and therefore, no birefringent walk off.
A preferred embodiment of the invention is generally referred to in FIG. 3 by the reference numeral 11. The monolithic body 11 includes a plurality of adjacent wafers 12 and 13 of a nonlinear monocrystalline material, a material which exhibits the well known second order (χ2) or third order nonlinear (χ3) interactions with input radiation. A second order interaction response (first order quasi-phase-matching) will be used in this description, although the scope of the invention of course is meant to encompass higher order responses, e.g., third harmonic generation, as discussed above. Due to crystal symmetry, the amplitude of χ3 is not inverted by a 180� rotation.
The monocrystalline material of each of the wafers preferably is selected to provide indices of refraction having the same or similar numerical values to reduce reflection losses. Diffusion bonded quasi-phase-matching can be achieved, in principle, in any nonlinear crystal. The linear properties of the material may be isotropic or anisotropic. The appropriate crystal must be transparent for the frequencies, preferably is fabricarable into individual plates having thicknesses equal to an odd multiple of coherence lengths for the interaction, and must be diffusion bondable. Some potentially useful materials are certain III-V semiconductors such as GaAs, GaP and InP; II-VI semiconductors for the infrared such as ZnSe, ZnS, CdTe and ZnTe; and I-VII semiconductors such as CuCl and CuBr for use in the ultraviolet. Like materials do not have to be joined to like materials, although to minimize the optical loss and problems due to differential thermal expansion, it is best to join similar materials; however, there are applications where it would be useful to diffusion bond a quasi-phase-matched structure to a substrate of another material for structural integrity, heat dissipation or other reasons.
Gallium arsenide (GaAs) has been found to be a quite suitable material for both wafers 12 and wafers 13. Large diameter, high quality crystals of it can be obtained. Moreover, the characteristics of GaAs are well known and it has a high damage threshold.
Each of the wafers 12 and 13 has a dimension along the expected optical path of the radiation through the same, to optimize the conversion of energy from the input radiation to the desired frequency of output radiation. To provide the requisite quasi-phase-matching component Km for frequency doubling 10.6 μm radiation, the thickness of each of the gallium arsenide wafers 12 and 13 is selected to be nominally equal to one coherence length (106 μm) for input 10.6 μm radiation which is generally orthogonal to the completed body. In general, though, as mentioned previously, it is the dimension of each of the wafers along the direction of propagation which is to be optimized or, preferably, made equal to an appropriate multiple of the coherence length of the radiation for the desired conversion. This dimension will depend largely on the angle at which the input radiation impinges on the body. Further, the radiation may be focused into the interaction region so as to increase or optimize the nonlinear process according to well known principles of nonlinear optics.
Adjacent wafers 12 and 13 are oriented relative to one another to provide the optimum conversion in accordance with standard quasi-phase-matching techniques. That is, each of the wafers is oriented to change the sign of the nonlinear coefficient. Since the sign is tied to crystal symmetry, in gallium arsenide for a (110) crystal wafer, the layers are oriented relative to one another so that the nonlinear coefficients of adjacent wafers are of opposite sign. That portion of each cycle in which there is an undesired energy transfer will be replaced by a portion of a new cycle with which there is a desired energy transfer.
In keeping with the invention, the mating faces, or in other words, the opposed faces, of adjacent wafers are diffusion bonded together. As stated above, diffusion bonding is the permanent bonding together of opposed surfaces ideally with no foreign substance between them--there is an exchange or sharing of electrons, atoms, ions or molecules. Once diffusion bonded, the resultant structure assumes the physical properties of the bulk material(s). There is no noticeable difference in properties between the bond and the bulk material(s).
Diffusion bonding has been developed and researched in the field of metals, especially steels. Only very recently has there been any work on diffusion bonding in semiconductors: either in silicon and silicon like materials, or GaAs and similar materials (III-V semiconductors). Two papers have been published on the bonding of III-V materials--Z. L. Liau, et al., "Wafer Fusion: A Novel Technique for Optoelectronic Device Fabrication and Monolithic Integration", Appl. Phys. Lett., Vol. 56, No. 8, 19 Feb. 1990; and Y. O. Lo, et al., "Bonding by Atomic Rearrangement in InP/InGaAsP 1.5 mm Wavelength Lasers on GaAs Substrates", Appl. Phys. Lett., Vol. 58, No. 18, 6 May 1991. In both cases, only two wafers were bonded together with the intent of forming optoelectronic devices. Electronic measurements were important to these studies, while the optical properties of the structures were not explored. There certainly is no disclosure in these papers regarding the dimension of adjacent wafers and the combination of diffusion bonding with quasi-phase-matching. Diffusion bonding also has been studied for Nd:YAG crystals. (See "Performance of Composite Glass Slab Laser" by Tajima et al. appearing in the IEEE J. Quantum Electronics, Vol. 28, No. 6, Jun. 1992, pp. 1562-1569.) Success has been achieved in building large laser crystals from smaller ones, and the bonding has held up under high power conditions in a laser cavity, demonstrating the high thermal mechanical strength of this type of bonding.
Recently there has been much interest in diffusion bonding between ceramics and metals for industrial and automotive applications. Theory of diffusion bonding has also been extensively treated in this field.
Diffusion bonding is in contrast to the temporary bond which can be achieved via optical contacting commonly used for many purposes in optics. It is superior to optical contacting for quasi-phase-matching for three reasons: a) because it forms a permanent bond, b) because it has no air layer, minimizing any reflection at the interface, and c) because a diffusion bond retains the thermal mechanical properties of the bulk material.
Surface preparation/cleaning and oven atmosphere are important for diffusion bonding. There are four additional important and inter-related parameters: surface flatness, temperature, pressure and time. The better the surface flatness of the layers being joined, the lower the temperature or pressure necessary for the bonding, or the shorter the time it will take to develop an effective bond. To achieve diffusion bonding, adjacent wafers are stacked together, pressure is applied to the stack and the temperature is increased. The increase in temperature must be sufficiently high to cause meaningful migration across the interface while remaining below the melting temperature, i.e., the temperature at which the material being heated will lose its crystalline structure and become a liquid. In the implementation of the instant invention discussed previously with gallium arsenide wafers, the faces of the wafers were first cleaned. That is, the faces were subjected to a hot microdetergent and deionized water solution for 0.5 hours, to hot trichloroethane for 10 minutes, hot acetone for 10 minutes, and then hot methanol for 10 minutes. (A "hot" solution refers to one just under boiling temperature for such solution.) At each stage the faces were scrubbed to remove any residue. After the wafers were blown dry they were packed together with the faces in contact with one another. They were then placed in a boron nitride holder with an additional tungsten weight of 900 grams. The holder with the stack was placed in an oven with a 5% hydrogen atmosphere to inhibit oxidation, with a nitrogen flow of 1 liter per minute to transport any particulate matter. The oven interior was raised to a temperature greater than 500� C., i.e., 820� C. over a period of one hour. It was kept fixed at 820� C. for at least two hours and then allowed to cool for eight hours.
Returning to FIG. 3, the body also included a pair of substrates 19 and 21 at the opposite sides of the wafer structure. A principal purpose of such substrates is to provide end plates whose thicknesses are not important, thus permitting polishing of final surfaces. These substrates can also provide meaningful width dimensions to the final structure and additional mechanical strength. In this connection, the stacked wafers themselves only provide a thickness of about 1 mm for the case of an 10 wafer structure, second harmonic generator for 10.6 μm radiation. Most desirably each of the substrate structures 19 and 21 has a thickness of at least 0.5 mm and is oriented to avoid nonlinear interaction. Each also is of gallium arsenide and is adhered to the faces of adjacent wafers by diffusion bonding as described above. This will assure that the inclusion of the same will not result in scattering loss at the interface to the remainder of the body. In the implementation of diffusion bonding set forth above, substrates 19 and 21 were included with the stack of wafers when it was subjected to heat and pressure. The resulting structure is a monolithic body of gallium arsenide for transforming input optical radiation to a desired frequency of output optical radiation.
The invention also includes a generator for producing 5.3 μm infrared radiation of significant power. With reference to FIG. 4, the generator includes a standard CO2 laser represented at 22 which generates radiation of 10.6 μm wavelength as represented at 23. This radiation is directed into a monolithic nonlinear crystalline material body 24 meeting the characteristics described above, to convert the same by second harmonic generation to an output radiation having a wavelength of generally 5.3 μm. This radiation is represented by the arrow 26.
Although the above is an external generator for producing the desired radiation, the invention also includes a generator for internally doubling radiation, e.g., the radiation of a CO2 laser. That is, the monolithic nonlinear crystalline material body may be incorporated directly into the laser cavity. Desirably, it is diffusion bonded in the cavity to the output coupler. The coupler may be highly reflecting for the radiation which would be output except for the invention, i.e., 10.6 μm radiation in a CO2 laser, but transmitting for the radiation which is desired.
This invention also includes a sum frequency generator for the infrared. Doubled CO2 radiation at 5.3 μm (30 THZ) is mixed with CO2 radiation at 10.6 μm (60 THZ). Both frequencies are directed collinearly into a monolithic nonlinear crystalline material body. The input frequencies are converted into an output frequency of wavelength 3.3 μm (90 THZ).
As mentioned previously, the dimension of each of the wafers is tailored dependent upon the expected path length of the radiation of interest therethrough. FIGS. 5A and 5B illustrate embodiments of the invention in which this dimension is changeable relative to the input radiation direction in order to allow output tuning. As will be discussed, the embodiments of these figures are particularly important in that they show configurations suitable for 2 micron pumped optical parametric oscillators (OPOs) that can be tuned. Previously, wedged domains have been built in QPM waveguides to compensate for design uncertainties and fabrication errors, but they have not been considered for a bulk structure.
With reference to FIG. 5A, each of the wafers 12' and 13' is wedge shaped, i.e., it varies uniformly in thickness in the direction of the expected path length. Moreover, the wafers are oriented together to match the variations and thereby provide a wedge configuration for the body, which body is generally referred to in the figure by the reference numeral 41. Means are also included for translating the wedge configuration relative to input optical radiation. That is, the body 41 is connected axially to a micrometer at 32 so that it can be selectively translated in the directions represented by arrow 33. Thus, if the angle and position of the input radiation is maintained static, the width of the material can be varied to match the radiation as desired. Although a micrometer is included for moving the wedge configuration, it will be appreciated that the means for translating the wedge configuration relative to the input radiation could move the source of the input radiation instead. The arrangement in FIG. 5B differs from the arrangement shown in FIG. 5A only in that substrates 19' and 21' are included.
This invention also includes a tunable optical parametric oscillator, built using the wedged diffusion bonded, quasi-phase-matched (DB-QPM) structure. The oscillator includes a standard source (laser or OPO) which generates radiation at about 150 THZ (2 μm wavelength). This radiation is directed into the wedged monolithic nonlinear crystalline material body, to convert the input radiation into output radiation of two frequencies such that (ω1)in =(ω2 +ω3)out. The frequency pairs, ω2 and ω3, are chosen/tuned by translating the oscillator perpendicularly relative to the direction of propagation. A tuning curve for the oscillator is shown in FIG. 6. The device is made by varying the thickness of the wafer from 70 μm to 120 μm over a possible translation range of 60 mm. This corresponds to third order quasi-phase-matching for this interaction.
In some instances it is practical to provide the monolithic nonlinear crystalline body of the invention directly on, or as a part of, another optical device to which the radiation is subjected. One advantage of doing so is that there is at least one interface which is eliminated. FIG. 7 illustrates an arrangement in which the substrate 19 is replaced by an output coupler 36 of a laser or the like which generates the optical radiation. Thus, the output coupler integrates the nonlinear device into the laser itself. Most desirably, the wafer structure is bonded to the output coupler or other optical device by diffusion bonding. This will eliminate the interfaces which normally would separate the body of the invention from other optical devices within the optic path and will provide mechanical support and a thermal conduction path for high average power applications. As discussed above, the monolithic nonlinear crystalline body of the invention can be placed on an optical coupler internally of a laser cavity, rather than externally as shown in FIG. 7.
Below is a divided table comparing the performance of two diffusion bonded, quasi-phase-matched (DB-QPM) materials, GaAs and ZnSe, to two birefringently phase matched materials, ZnGeP2 and AgGaSe2. They were all compared for doubling CO2 radiation at 10.6 μm (30 THZ) to 5.3 μm (60 THZ). The constants for these calculations were taken from a wide variety of sources and were selected as deemed appropriate. Because measurement techniques are being continually improved, the table is not meant as a source of absolutes but rather as an indicator of comparable trends. AgGaSe2 is critically phase matched, while ZnGeP2 is non-critically phase matched. Both DP-QPM materials are non-critically phase matched. The much wider acceptance bandwidths are apparent in the DB-QPM materials. The four figures of merit demonstrate usability in different situations. The first two show the performance for continuous and pulsed operation, respectively; the third shows optical distortion; and the fourth, a figure of merit for high average power conversion.
__________________________________________________________________________Second Harmonic Generation of 10.6 μm Radiation for a 1 cm LongCrystal DB-QPM DB-QPMcrystal GaAs ZnSe ZnGeP2 AgGaSe2__________________________________________________________________________transmission range 0.9-12 0.5-14 0.7-12 0.7-12(μm)d 83 50 70 33(pm/V)α 0.01 0.0005 1 0.01(cm-1)Ktherm 52 18 35 1(W/mK)dn/dT � 106 149 64 ddo /dT = 150 ddo /dT = 70(K-1) dne /dT = 170 dne /dT = 40dΔn/dT � 106 1.6 0.7 20 30(K-1)n.sub.ω 3.271 2.403 3.125 2.592n2ω 3.296 2.429 3.125 2.592 -- -- -- 0.68(degrees)θpm -- -- 90 @ 55(degrees) T = 92� C.deff 61 37 70 27(pm/V)Δλ 0.48 0.2 0.06 0.12(μm)ΔΘint 16 15 12 0.8(degrees)ΔT 270 < 500 16 15(K)FOMcw 6500 2400000 1 2600FOMp 2.5 2.3 3.8 1FOMod 160 2400 no axis = 1.1 no = 6.9 ne axis = 1.0 ne = 12FOMhp 44600 27500 1 14__________________________________________________________________________ d = nonlinear coefficient of the crystal α = absorption coefficient of the crystal Ktherm = thermal conductivity of the crystal dn/dT = change in index of refraction as a function of temperature; the birefringent crystals have two different indices of refraction dΔn/dT = Δn = n2 - n1 ; change in the difference of index of refraction as a function of temperture n.sub.ω = index of refraction at 10.6 μm n2ω = index of refraction at 5.3 μm = walkoff angle Θpm = phase matching angle measured from the optical axis. DBQPM structures have no optical axis deff = effective nonlinear coefficient taking into account the angl of propagation and quasi phase matching Δλ = the acceptance bandwidth for wavelengths ΔΘint = the acceptance bandwidth for angles (this is the internal angle in the crystal) ΔT = the acceptance bandwidth for temperatures NB. for Figures of Merit. They have all been normalized to the lowest value. FOMcw = Figure of Merit for a continuous laser: FOMcw = deff 2 /n3 α2 FOMp = Figure of Merit for a pulsed laser: FOMp = deff 2 /n3 FOMod = Figure of Merit for optical distortion: FOMod = Ktherm /αdn/dT NB For birefringent crystals, we indicate the optical distortion Figure o Merit for the two different axes. FOMhp = Figure of Merit for high average power performance: FOMhp = deff 2 Ktherm /αn2 dΔn/dT
A diffusion bonded quasi-phase matched structure has many advantages for high average power application. This is important for high average power nonlinear devices especially in the infrared region. Currently there is no acceptable high power second harmonic generator, or other mid-infrared nonlinear optic device for CO2 lasers. There is a great deal of interest in developing mid infrared sources, between 3 to 5 microns, either by doubling CO2 lasers or by pumping an optical parametric oscillator (OPO) with 2 microns. Both of these goals can be accomplished with diffusion bonded quasi-phase-matched GaAs structures.
Some of the qualities which make these structures interesting for high average power applications are: a) the possibility of using high average power, low absorption crystals which have little or no birefringence, b) the thin size of the structure itself, and c) the thermal mechanical strength of the diffusion bond which will be identical to that of the bulk material. A diffusion bonded quasi-phase-matched GaAs structure with a conversion efficiency of greater than 50% can be built with a total thickness of approximately 1 mm. This thinness has a twofold benefit; it is more easily cooled and has a much lower absorption than a similar thicker sample. Birefringently phase matched crystals such as AgGaSe2 and AgGaS2 which are currently used for mid infrared devices have poor thermal conductivity and, therefore, do not handle high average power well.
Because of the nature of the structure, there are a few special properties that are worthy of mention. There is a large bandwidth of acceptance; this permits the same device to be used for similar but slightly different frequencies. This also means that the device can track frequency fluctuations in one source. Diffusion bonded structures for quasi-phase-matching (DB-QPM structures) also have a large temperature and a angular acceptance. This provides a built-in tolerance of temperature fluctuations and alignment. If there is no birefringence in the basic crystal, then there will be no birefringence walkoff.
As mentioned at the beginning of the detailed description, applicant are not limited to the specific embodiments described above. Various changes and modifications can be made. For example, although the preferred embodiments of the invention have been described as if the angle of the input optical radiation relative to the monolithic body is static, it is contemplated that in many instances it will be desirable to vary the angle for tuning and/or to make a single body applicable to optical radiation of differing wavelengths. Variations of this nature can be combined, for example, with the embodiments of FIGS. 5A and 5B. It also should be noted that in some instances the change of frequency can include a change in bandwidth. The claims, their equivalents and their equivalent language define the scope of protection.
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|U.S. Classification
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|International Classification
|Cooperative Classification
|European Classification
|Jul 6, 1993
Owner name: BOARD OF TRUSTEES OF THE LELAND STANFORD, JR. UNIV
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text:
K-State Seeks to Slow Sooners
K-State Seeks to Slow Sooners
Nov. 18, 2010
Complete Release in PDF Format
MANHATTAN, Kan. - Kansas State closes its week on Saturday when the Wildcats travel south to take on the Oklahoma Sooners. First serve is set for 3 p.m. from McCasland Field House where the Sooners have only lost three times this season, twice to ranked opponents. The Sooners currently stand tied for third in the Big 12 Conference standings with an 11-6 league record and are receiving votes in the latest AVCA Coaches Poll.
In the first meeting between these two teams this season, the Sooners got the sweep that started K-State's eight-match losing streak. The Sooners had three players reach double digits in kills in the match and hit .282 as a team while K-State's offense could not keep pace. Kaitlynn Pelger tallied 14 kills and hit .571. This time around the Wildcats will look to give the Sooner their first loss to K-State since 2008 after OU won both matches last year.
Pelger is coming off another solid performance as she put together one of her most complete matches of the season on Wednesday night despite the loss to Texas A&M. The freshman middle blocker posted a career-high 18 kills and had her highest hitting efficiency of the season with a .577 clip. Pelger also kept the Aggies off balance with her serve as she nailed three aces. At the net, Pelger was a force defensively as well leading the team with five block assists.
On The Airwaves
Saturday's match can be heard tape delayed on KMAN 1350 with Rob Voelker calling the action. The match will be available live through 1350kman.com and kstatesports.com with live audio streaming.
Live stats will be available through kstatesports.com for fans wanting to track the action live on the web. Live audio of KMAN's broadcast will also be provided through kstatesports.com.
The Series
Oklahoma leads the all-time series against the Wildcats with a record of 47-25. K-State leads the series since the inception of the Big 12, however, winning 19 of the 29 matches. The Sooners have held the advantage of late winning seven of the last nine meetings sweeping the series in 2006, 2007 and 2009. Suzie Fritz is 12-7 against OU.
The Coaches
Kansas State: Suzie Fritz (Florida Atlantic '94) is in her 10th year as head coach of the Wildcats she is the winningest coach in the program's history in terms of wins (193) and is not far off of the best winning percentage in school history as well at .629.
Oklahoma: Santiago Restrepo (East Stroudsburg '86) is in his seventh year coaching the Sooners where he has energized the program back into an NCAA Tournament caliber team. He has taken OU to the postseason three of the last four years.
Scouting the Sooners
The Sooners just went through a tough stretch in their schedule facing No. 14 Iowa State and No. 5 Nebraska back-to-back. Oklahoma was able to get the upset over Iowa State, however, in Norman in four tightly contested sets. Seven of Oklahoma's nine losses have come to ranked opponents this season.
Oklahoma is led by junior right side hitter Suzy Boulavsky averaging 3.53 kills a set. Her hitting percentage is .284 as she takes the majority of the swings for the Sooners, but is not alone as the team's only scoring threat. Three more Sooners averaged at least 2.00 kills a set. Freshman sensation Sallie McLaurin is averaging 2.17 kills and is hitting over .300 on the year. She also ranks fourth in the conference in blocks with 1.25 stuffs a set. McLaurin has claimed three Big 12 Rookie of the Week awads this season as well. Sarah Freudenrich leads the team in hitting percentage and is averaging 2.13 kills while Caitlyn Higgins holds steady at an even 2.00 kills. Higgins led the Sooners in kills with 12 in the first meeting this season with K-State.
The Sooners rank among the middle of the pack in most statistical categories in the Big 12 with the only glaring abnormality coming in service aces. Oklahoma ranks 10th in the league in aces per set as the Sooners average just 0.76 in each stanza.
Setter Brianne Barker is one of the most consistent in the conference and averages more than 10 assists per set. Barker has an offensive flare as she averages 1.11 kills a set to keep defenses off balance with a number of dump attacks. She also is third on the team in digs averaging 2.57 a set.
Catching up with the 'Cats
Kansas State dropped a heartbreaker to Texas A&M on Wednesday night after fight its way back into the match dropping the first two sets. The Wildcats dominated the third set to take the momentum into the fourth, but fell behind early by seven points. K-State chipped away at the lead and eventually reclaimed it and led late 21-19 only to see the Aggies score five straight points backing the Wildcats into a corner before losing the match 16-25, 21-25, 25-18, 22-25.
Freshman middle blocker Kaitlynn Pelger had arguably the best match of her short career on Wednesday night as she put together a complete effort for the Wildcats. Pelger posted career-highs in kills with 18 and hitting percentage as she hit for a .577 clip. Those were not her only two strong stats on the night, however, as she assisted on five stuff blocks, had eight digs and tallied three aces in the 3-1 loss to Texas A&M.
Senior libero Lauren Mathewson is inching closer to moving up in the K-State record books again. Mathewson needs just five digs to move past Angie Lastra's junior season total of 474 digs to rank eighth in school history for a single season. The Kansas City product has three seasons ranked on the top 10 list and now has her eyes set on becoming the first player in school history with three 500-dig seasons.
Senior Night Ticket Special
The final home match of the season is fast approaching and fans are being offered a special discounted price when they purchase tickets online. Tickets to Senior Night are just $3 when bought online at kstatesports.com and fans use the promotional code V14FUN. November 27th will be the final match of JuliAnne Chisholm's and Lauren Mathewson's careers. Come send them off with a strong showing and buy your tickets today as the special price expires on November 24.
Packed with Purple
Ahearn Field House has been rocking this season with an average attendance of nearly 2,100 fans. K-State fans have always been loyal to their Wildcats when it comes to volleyball with the fans ranking in the Top 30 in national attendance regularly. This season K-State is currently 14th in the nation in attendance and third in the Big 12 Conference behind only Nebraska (2) and Texas (9). Missouri (17), Iowa State (19), Texas A&M (22), Colorado (42), Oklahoma (43), Kansas (45) and Baylor (48) all rank among the schools averaging more than 800 in attendance as of matches played through November 14 as tracked by Diane Nordstrom of Wisconsin.
After recent renovations to the seating were completed, the fans have come to watch the Wildcats play in droves with all but one home match reaching 1,300 in attendance. In the Big 12 Conference opener against Kansas, the Wildcat faithful filled the rafters with 3,160 fans to cheer the team to victory. K-Staters then packed 3,695 fans into Ahearn for the match against Missouri (9/25). That is the third largest attendance for a home match since the 2003 season and is among the most attended matches in the nation to date this season.
Mathewson Among Big 12 Elite
Senior libero Lauren Mathewson has put her name in the record book a number of times during her career at K-State, and she now has solidified her place in Big 12 Conference history. Mathewson's 1,685 career digs rank second in K-State history and she is now fifth in Big 12 history.
With four current liberos in the conference starting for three and some four years at their respective schools the career Top 10 list in the Big 12 had quite a bit of shuffling this season. Iowa State's Ashley Mass surpassed K-State's Angie Lastra for first on the list, and Missouri's Caitlyn Vann stands fourth with 1,863. Mathewson is fifth, and Nebraska's Kayla Banwarth is sixth with 1,628.
Mathewson posted her seventh 20-dig match of the season against Baylor (11/13) to tie her for seventh in a single season in school history in the category. It also gives her 22 for her career to stand in second alone over Laura Downey. She also has had four matches with 19 digs -- all of which came in three-set matches. Mathewson currently ranks fifth in the conference averaging 4.75 digs a set and has 470 digs on the year to rank ninth in school history for a single season. Her dig total in conference play only gets better as she is digging 4.93 balls a set in league action to rank third behind only Mass (5.31) and Vann (5.22).
Two Wildcats Named Academic All-District
The Kansas State volleyball team has a long history of combining success on the court with success in the classroom. This year's senior captains JuliAnne Chisholm and Lauren Mathewson added to that list of classroom achievements as they were each selected to the CoSIDA/ESPN Academic All-District VII Team.
Chisholm was named to the first team for the second consecutive year making her eligible for Academic All-America voting. She currently has a cumulative GPA of 3.97 in athletic training/pre-med and life sciences with a secondary major in gerontology.
Mathewson was voted to the third team for her first Academic All-District honor of her career. She holds a 3.84 GPA majoring in business administration and will graduate in December. Mathewson also has a pair of Academic All-Big 12 First Team awards on her list of academic accolades receiving the award each year she has been eligible.
The Wildcats have now had 16 Academic All-District selections under head coach Suzie Fritz in her 10 seasons leading the program.
"Por"ing it on
Freshman outside hitter Lilla Porubek has emerged as a go-to player for the Wildcats late this season. Her kill production has seen significant improvement, and she recently pounded out a new career-high nine kills at No. 5 Nebraska last week. In the loss to Nebraska, Porubek had nine kills and led the team with 27 attempts. She has posted five or more kills in five of K-State's last six matches with seven against No. 12 Iowa State (10/27), six in the win over Texas Tech (11/3), five against Baylor (11/13) and eight versus Texas A&M (11/17).
The native of Budapest, Hungary, missed the first two weeks of the season to represent her country on the Hungarian Junior National Team at the 2010 European Championships.

subset: commoncrawl


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To support the start of the UK's "Get Safe Online Week", part of Cyber Security Awareness Month, GlobalSign, the enterprise SaaS Certificate Authority (CA), is publishing some useful information to benefit today's ever increasing online consumer community.
With advancements in technology, many consumers no longer need to leave the comfort of home to go shopping. Falling broadband costs and increasing usage of handheld devices, along with the many online savings to be made have diminished the need to go out to the high street to shop. In fact, according to a recent survey, a fifth (20%) of Brits now spend more on items purchased online than they do in store, while recent predictions in the US suggest that by 2017 10% of all sales will be made online, with mobiles devices accounting for 25% of those retail sales.
October marks the month for cyber security awareness and educational campaigns, and GlobalSign is providing the following top five tips that will not only help to ensure a safer online shopping experience, but also offer the consumer some helpful hints when it comes to online purchasing.
* Look for "secure site" indicators: Shoppers should always look for the yellow padlock in browsers that indicates a website is using SSL – an encryption technology ensuring that the data sent to the retailer is encrypted and secure. A site using an SSL Certificate can also be identified by a website URL that commences with "https", as opposed to the standard "http" of a non-secured site.
* Protect your privacy and identity: Your privacy is important; protect it at all times to minimise the chance of identity theft. For sites requiring a user name and password to be set up as part of the buying process, try to use different combinations to the ones you use for banking, web mail and other accounts. If they start asking for details you think are irrelevant to the purchase, such as bank account details and date of birth, start questioning why. These details are not needed for a simple online purchase.
* Be on the lookout for scams: Beware of unbelievable offers sent by email – regardless of whether you know of the retailer "offering" them. Phishers (fraudsters masquerading as known companies) send millions of emails daily and place thousands of online ads offering the best 'cannot miss' deals. If you receive an email or see an online advertisement, be sure to check the URL in the browser address bar. Be extra wary of IP addresses (such as http://245.123.123.1/special-offer) and email addresses or websites containing a well-known brand name in conjunction with other lettering or numbers (e.g. www.globalsign-1.com).
* Use a safe method of payment: Most credit cards offer protection on purchases, so use them wherever possible. Debit cards and other methods of payment usually offer a lower level of protection and may leave the consumer out-of-pocket while a claim is processed. If the merchant does not accept credit cards, or you do not have one, look for other methods of safe payment such as PayPal.
* Get the details, keep the records: Make sure you know the merchant's full address, especially if it's outside of your own country, and double check the delivery costs and refund terms. This information will help you in case you run into any problems with delivery of items purchased.
People shop online because they view it as quicker, easier and they can find better bargains. By following this practical advice from GlobalSign, online shoppers can rest assured that their personal information remains safe and they can stay one step ahead of today's ever increasing number of scammers.


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2004 Ford Ranger Problems
RepairPal has identified the most common problems with the 2004 Ford Ranger based on complaints from actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.
The engine may misfire and/or buck while driving at freeway speeds with no fault code stored in the powertrain control module (PCM). This can be caused by an intermittent fault with the camshaft synchronizer assembly. This condition can be diagnosed by monitoring knock sensor data as per Ford service bulletin #05-22-12. Replacement of the synchronizer assembly will be required to correct this concern.
The Ford Ranger V6 is known for a rough idle, engine stalling, loss of power, and misfires, accompanied by the check engine light.
The intake manifold O-ring gaskets commonly leak, which creates a large vacuum leak. This vacuum leak causes unmetered air to enter the engine, and the fuel system becomes insufficient to compensate for the large amount of air reaching the engine.
Replacing the intake manifold gaskets corrects this concern.
The magnet for the camshaft position sensor may fall out of its mount and damage the synchronizers. This causes long crank times when starting the engine and may cause the Check Engine Light to illuminate. If this happens, both the magnets and the synchronizers need to be replaced.
Bogging, hesitation or stalling may be experienced during moderate to heavy acceleration. This can be caused by a failing of many sensors or modules in the fuel injection system. It is recommended to have an experienced shop perform diagnosis to find the root of the problem.
Many customers state that whule driving their vehicle, the engine will hesitate, stumble, or lose power. In more severe cases, the EGR valve can be physically damaged. In all cases, the check engine light will be illuminated, and diagnostic trouble codes will be stored in the PCM.
Diagnosis of the issue has concluded the differential pressure feedback EGR sensor (DPFE) is at fault many times, and incorrectly measures exhaust gas re-circulation (EGR) pressure.
Correction of the issue requires a diagnostic scan, identification of the faulty sensor, and, ultimately, the sensor and EGR valve may require replacement. In some models, the DPFE sensor is integrated into the EGR valve, and must be replaced together.
If a noise from the rear end is heard when going around turns or after driving at highway speed for an extended period, this could be caused by a failing deferential clutch kit. An updated differential clutch kit available.
The synchronizer shaft for the camshaft position sensor can cause a loud squeak or chirping noise due to failure of the upper bushing. The noise may be erratic and is usually present when the engine is warm.
A buzzing type noise may be noted from upper engine area at about 1900 RPM, under light acceleration. Our technicians tell us this can be caused by loose ignition coil bracket bolts. Coil bracket bolts should be checked for the correct torque before further diagnoses is performed.


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We've fallen head over heels for these dreamy wedding decor and food ideas.
11 Unique Tablescape Ideas for a Baby Shower
We've fallen head over heels for these dreamy wedding decor and food ideas.More
We love Terrain's perfectly curated selection of home and garden goods, so it's no surprise that we're just as smitten with the brand's special events space in Glen Mills, PA. Since opening its doors, the charming greenhouse, lodge, and terrace have hosted dozens of Pinterest-worthy shindigs. Here, we've rounded up a few ideas from some of our favorites. The best part? It's easy to borrow from these ideas for your own wedding day.
In this photo: Stashed inside a vintage apothecary bottle, a single stem of allium or other top-heavy bloom makes for an easy-to-arrange statement centerpiece. Other unexpected additions? Fern fronds, which add plenty of texture.
A coat of chalkboard paint transforms any surface into a display space for seating information. Enlist a bridesmaid with pretty penmanship to make the chart, then doodle some blossoms in the corners.
RELATED: 8 Great Wedding Place Card Ideas
10 Whimsical Ideas for an Alice in Wonderland-Themed Valentine's Day Tea Party


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Please enter your email address and password below.
Texas Children's Toys values its customers and respects their privacy. We collect customer information in an effort to improve your shopping experience and our delivery of services to you. Texas Children's Toys recognizes it must maintain and use customer information responsibly. We do not sell, trade or rent to third parties information you provide.
This policy describes the personal information Texas Children's Toys collects about you, why we collect it, and how we use it.
If our information practices change in the future, we will let you know by posting the policy changes on our Web site.
We collect information (such as your name, e-mail address, mailing address and phone and credit card numbers) from you when you place an order.
We use your information to process your order. We also send you e-mail to confirm your order, and we might contact you via phone, postal mail or e-mail if we have questions regarding your order. Your credit card number is securely transmitted to the bank processor and is not stored on the Texas Children's Web site.
If you are ordering a gift for delivery to a patient at Texas Children's Hospital, you will need to provide us with the patient's name. Texas Children's Toys shall protect patient-identifiable information in accordance with Texas Children's Hospital's policies relating to confidentiality and all applicable federal and state laws.
We use Secure Sockets Layer (SSL) software, the industry standard and among the best software available for secure online commerce transactions, to ensure your information is protected. It encrypts all personal information, including name, address and credit card number, so it cannot be read as it travels over the Internet.
Like you, Texas Children's Toys is concerned about the safety of children when they use the Internet. Consistent with the Children's Online Privacy Protection Act of 1998, we will never knowingly request personally-identifiable information from anyone under the age of 13 without prior verifiable parental consent.
Security relating to credit card information collected by Texas Children's Toys is provided by Cybercash. Additional information about this company can be found at www.cybercash.com.
By ordering items from Texas Children's Toys Web site, you will be purchasing these items and will be charged accordingly. You will receive your purchased items via delivery at the address you specify in your information or you may have your items delivered to a patient who has been admitted to Texas Children's Hospital if you specify the patient's name. It is crucial that you review the information you send us for proper spelling and typing errors so that we can process your order correctly. Texas Children's is not responsible for problems relating to incorrect or false information that is provided to Texas Children's Toys. Texas Children's Toys retains the right, in its sole discretion, to deny access to the services provided herein to anyone at any time. By ordering from Texas Children's Toys, you agree to be bound by all the terms and conditions herein.
Privacy Policy and Legal Statement Shipping Policy Return Policy
©2010 Texas Children's Hospital I Texas Children's is affiliated with Baylor College of Medicine


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U.S. crude oil futures rose more than 2 per cent Thursday, to the highest settlement in 2-1/2 years, and the global economic recovery also sent cotton, silver and gasoline soaring in the first three months of 2011.
Benchmark West Texas Intermediate crude rose $2.45, more than 2 per cent, to settle at $106.72 a barrel (U.S.) on the New York Mercantile Exchange. At one point it hit $106.83, the highest it's been since September, 2008. In London, Brent crude rose $2.25 to settle at $117.20 per barrel.
The Reuters-Jefferies CRB index of 19 mostly U.S.-traded commodities rallied 8 per cent for the quarter and was up 1.6 per cent for the day at a level last seen Sept. 2008.
Threats to oil supplies posed by the conflict in Libya and unrest in the Middle East put upward pressure on prices, as did positive U.S. economic data. Japan's nuclear crisis and well as rising interest rates in top raw materials user China weighed on sentiment.
Worries mounted about Syria, where more than 60 people have been killed in protests. President Bashar al-Assad defied calls to lift a decades-old emergency law, despite hundreds marching in Latakia chanting "freedom" on Wednesday.
Earlier, oil prices firmed along with other commodities, like metals and grains, when a U.S. government report showed jobless claims fell last week. The report arrived a day before the closely watched March nonfarm payrolls report is due.
Adding support, the Institute for Supply Management-Chicago reported its employment index in March hit the highest level since December 1983, though its overall business barometer dipped in February.
Investors are preparing for Friday's monthly U.S. employment report and expectations point to a sixth consecutive increase in the number of workers on non-farm payrolls, the longest stretch of gains since late 2006.
The data gave a boost to copper , which closed slightly higher but ended the first quarter of 2011 with a 2.4 per cent loss, its first quarterly decline since the second quarter of 2010. Concerns about softer Chinese demand and rising warehouse stocks weighed on sentiment.
Among precious metals, global economic growth combined with geopolitical risk could keep boosting silver , which gained 22 per cent in the first quarter, its ninth consecutive quarterly increase that took the price to 31-year highs above $37.00 an ounce.
With the price of gold near record highs, silver has been a major beneficiary of demand from investors seeking cheaper safe-haven alternatives.
"Silver's seen a perfect storm with a combination of a positive economic outlook to boost its industrial demand, together with inflation risks, geopolitical unrest and natural disasters. Little wonder it jumped so much," said a Singapore-based bullion trader.
Spot silver was up 0.9 per cent at $37.78.
Gold also rose, posting its 10th consecutive quarterly increase, although the 0.9 per cent gain was its slowest since late 2008.
Gold touched a record $1,447.40 last week. It has since retreated to $1,428,90, but the expectation among analysts is for the price to remain well supported by the prospect of safe-haven demand stemming from the violence in the Middle East and concern over the euro zone's debt problems.
"Until we see a substantial decrease in liquidity or a rise in real interest rates, you would look for an upward trend, and all these other factors like the euro zone debt and Middle East, North Africa issues are also a short-term support," said Standard Bank analyst Walter de Wet.
Grains surged, with corn rallying 4.5 per cent as strong demand whittled down stocks even as farmers geared up to plant the second-largest area since 1944.
Soybeans soared to a seven-week high after the U.S. Agriculture Department reported lower-than-anticipated stocks and spring seedings that were below expectations.
Wheat rose 5 per cent, following soaring corn and soybeans despite a bearish stocks estimate and a larger-than-expected jump in the USDA's spring wheat seedings forecast.
"Even though we've seen food inflation and everything else that has taken place, the demand has not backed away. Even at these lofty prices, we're still seeing strong demand in the U.S. and in world markets for agricultural commodities," said Shawn McCambridge, analyst with Prudential Bache Commodities.
The potential threat to supply pushed cotton futures up by about 35 per cent in the first three months of the year,in their eighth consecutive quarterly gain, after having nearly doubled in price last year.
A U.S. government crop report is expected to show sowings at a 5-year high, which could cool the market, but with prices close to record highs, this offered consumers little relief.Report Typo/Error
Follow us on Twitter: @GlobeBusiness
- Crude Oil Front Month Futures$47.75-0.76(-1.57%)
- Copper High Grade Front Month Futures$3.00+0.06(+1.89%)
- Silver Front Month Futures$16.980.00(0.00%)
- Gold Front Month Futures$1,290.20+4.50(+0.35%)
- Updated August 17 7:01 PM CDT. Delayed by at least 15 minutes.


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Arachnophobias - Can't Feel the Pain (Ethereal Remix 2012) MP3
Arachnophobias - Can't Feel the Pain (Ethereal Remix 2012) Unete a Sonido Manchester https://www.facebook.com/sonido.manchester.
Iggy Azalea - Black Widow (Delay Remix) MP3
Support Trap Nation ♫ ♢http://twitter.com/alltrapnation ♢http://facebook.com/alltrapnation ♢http://soundcloud.com/alltrapnation ♢http://alltrapnation.com/ ♫ Support ...
eyenine - arachnophobia MP3
eyenine - arachnophobia from the album "the insomnia sessions" it's time to be honest, so let me crack this open i'm a self-absorbed nihilist and i'm ...
Arachnophobia 2014 - Official Aftermovie MP3
Arachnophobia 2014 - Official Aftermovie Party took place @ Boeretang (Mol, Be) on nov 14 2015. More info? Visit www.arachnophobia.be.
Disco Dance Remix 80-90 vol.1 by PianetaTv MP3
I grandi successi degli anni 80-90 remixati da Duran Duran a Europe da Sabrina Salerno a Toto e tanti successi ancora.
PIMPLEJUICE24 - ARACHNOPHOBIA - Elise game play 16/5/12 MP3
Hope you enjoyed the video! if you have show some support and feedback by adding this to your favorites, clicking the like button, subscribing to my channel, ...
Future Bass Mix Vol.2 - Experimental Trap Mix for August 2015 [ Futurebass ] MP3
A new trap remix of popular songs with a tracklist. This mix of trap and bass boosted songs is very sick with heavy drops ! If You like it - like, share and subscribe.
Arachnophobias "Hybrid" MP3
Arachnophobias "Hybrid" Arachnophobias senaste video "Hybrid" Kolla gärna in deras myspace sida! http://www.myspace.com/arachnophobias Producerad av ...
東方 [Instrumental/Metal] Kokuyasou - Arachnophobia MP3
Number: 0343 Title: Arachnophobia Artist: Setsuna Circle: Kokuyasou (aka Black Funeral) Album: Catharsis Original: 暗闇の風穴 | The Dark Blowhole (Touhou ...
Squat PR & Arachnophobia MP3
in this video i show you my deepest fears & my deepest squats. as well as some squat warmup work =) DIRECT ALL QUESTIONS TO: ...
[Trap] Dextek - Arachnophobia MP3
Sweg m8... I tried trap. Started off good, but it fell apart at the drop imo. I guess trap's just not my thing. I can't make legit sub kicks and stuff. Future stuff is gonna ...
Shimon & Sparfunk - Cold Killa (Sub Focus Remix) UNRELEASED TRACK MP3
Check out the UNRELEASED Shimon & Sparfunk - Cold Killa (Sub Focus Remix)
Teknique - Life of Lies (Tour de Force Remix) MP3
The album was recorded far back in the 1992, but something went wrong and Nightfall was left for the future. Today Teknique are prepearing new remastered ...
Freestylers feat pendulum & sirreal Painkiller Noisia Remix MP3
Freestylers feat pendulum & sirreal - Painkiller (Noisia Remix) of Stadium drum and bass CD2.
baron - squelch (sub focus remix) MP3
enjoy ;)
Arachnophobia!!! The itsy bitsy spider guard, Trailor MP3
Spider Guard Seminar.
Boys Noize - What You Want (Meaux Green Remix) HD MP3
Boys Noize - What You Want (Meaux Green Remix) Free Download: https://www.facebook.com/meauxgreenmusic/app_182222305144028 About the artists: ...
mr iron lung sketchman chat to me iron lung dubplate remix MP3
mr iron lung sketchman chat to me iron lung dubplate remix.


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Two years and out: Sandbox mag of Winnipeg publishes final issue
Sandbox, a Winnipeg-based online and print magazine about local art, fashion and lifestyle, will publish its final issue January 30. The magazine only last summer was named best new magazine of the year at the Western Magazine Awards.
"In just two years, Sandbox has become more than just a magazine," said editor Jeffrey Vallis in a Facebook post. "It's become a community of talented and creative local artists that will live on far beyond the final issue.
The final issue will be available exclusively at McNally Robinson Booksellers in the Grant Park Shopping Centre and a farewell party is being held at the Winnipeg Art Gallery January 28.
According to a post on the blog ChrisD Sandbox was launched in 2010 by Vallis and Braden Alexander and funded by newsstand sales, ads and proceeds from magazine release parties. To celebrate its first anniversary last December, the publishers put out a mammoth 108-page special print issue (shown). Sandbox appeared four times a year in print and 8 times online.
"Our dream was to see the magazine in print –– just once –– even if it meant maxing out our student loans to do it," [said Vallis] "But when that day finally came, we weren't ready to stop at just one and, thankfully, neither were our readers. Considering we did it all with no money, minimal time and a makeshift office in our parents' basements, we couldn't be more proud."
Labels: closures


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General DLC server bug reporting. (Downloading issues only!)
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To start preparing your thesis consider the following generic checklist. Yes, sounds a bit daunting, I know, but it is not really, once you start, as you end up making your own work better and you might get published as many of my students have.
- Reduce it to these subheadings: background, method, results, conclusion. Use 2-3 sentences for each of these subheadings. Some journals want to see these subheadings but for others just make sure they are covered in the abstract in that order, you don't have to type them.
- Check word count against journal guidelines and reduce further if needed.
- Cut by about 50% by staying only focused on material that is related to building a case for the hypotheses.
- Remove duplication.
- Update citations (e.g., new up-to-date citations).
- Cite previous work by your co-authors and their colleagues as appropriate.
- Remove assumption testing sections.
- Move the "Statistical Analysis" section (where you talk about what software you used, any transformation or outlier issues etc.) to the end of the Method section.
- Reduce power analysis sections down to a sentence or two at most and put it in the "Statistical Analysis" section.
- Double check that the hypotheses are tested and reported in the order they are presented in at the end of the introduction.
- Remove subheadings unless absolutely necessary.
- Double check that all tables are needed.
- Double check that there is not too much overlap between what is reported in tables and text.
- Cut by about 30% to start with.
- Make sure there are sections called "Limitations" and "Conclusion".
- Put all tables and figures at the end of the document with tables first then figures.
To identify a journal to submit to
- Have a look at your reference list and note where similar articles are published and then check the journal "information for authors" in these journals.
- Make sure the journal is listed at http://www.scimagojr.com/journalsearch.php or https://doaj.org/
- Add doi to your reference list entries.
- Make sure to check the format requirments of the journal you are submitting to (e.g., citing, tables, figures, headings).
Other stuff
- Remember to check the comments you have got from your examiners to see if there is anything there that you need to address.
For how to collaborate on a document see http://einarbthorsteinsson.blogspot.com.au/2014/11/how-to-collaborate-on-document.html
Last but not least follow the APA manual.


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With WinHEC right around the corner (about two weeks away) people are starting to find out which build of Vista Microsoft will hand out to attendees. Paul Thurrott has said that Microsoft is going to hand out Vista 5381 and this will be branded as Beta 2. Here is what he had to say:
Microsoft continues work on Vista build 5381, which will be finalized as Beta 2 on May 22. Attendees of the Windows Hardware Engineering Conference (WinHEC) 2006 will receive Vista Beta 2 on DVD, and Microsoft plans to seed the build with testers, other partners, and millions of consumers via a widely distributed Community Preview Program (CPP) in the following days. If you've been waiting for a chance to get your hands on Vista, that day is finally coming.
The recent builds of Vista have definitely been getting progressively better. With the release of Beta 2 we might see an operating system that will be usable on a daily basis. I have heard many people talk about incompatible drivers which either causes the system to frequently crash or not even install. I am sure that these issues will be quickly addressed since Vista should have all of their features implemented by this point.
News Source: WindowsIT Pro


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Mikko Hirvonen moved into the World Rally Championship lead as he claimed his first victory for the Citroen team in Portugal.
The Finn ended up dominating an extroardinarily difficult rally, on a weekend when all the other usual frontrunners made mistakes.
Hirvonen's team-mate Sebastien Loeb had crashed out on the opening night on Thursday, and Ford duo Jari-Matti Latvala and Petter Solberg then slid out of the lead on consecutive stage amid torrential rain on Friday.
That left Hirvonen to control the rest of the weekend. His final margin of victory was 1m51.8s over Adapta Ford's Mads Ostberg, as Russian Evgeny Novikov (M-Sport Ford) secured his maiden WRC podium in third. Both independent Ford drivers survived final day scares - Ostberg's car developing a misfire on Sunday morning, and Novikov driving most of the final loop with a broken throttle pedal.
Despite this issue, Novikov managed to hang on just ahead of Solberg - who surged back up the order under Rally 2 to take fourth, even though a power steering failure cost him more time on Saturday afternoon. Team-mate Latvala had a fuel pressure problem on leg three and lost 12 more minutes on top of his Friday crash delay, and had to settle for 14th place and two power stage bonus points.
Nasser Al-Attiyah recovered from a late puncture on his Qatar Citroen to win a close fight for fifth with Czech National Ford driver Martin Prokop, as both celebrated career-best WRC finishes.
Dennis Kuipers took seventh on his first appearance of 2012 in an M-Sport Ford, despite Sebastien Ogier's best efforts to catch him in the giant-killing Volkswagen-entered S2000 Skoda.
Thierry Neuville was in the top five for Citroen Junior until his car overheated on Friday morning. The Belgian recovered to ninth - although he must get back to service on a damaged tyre to secure the result after two punctures on the final loop.
Jari Ketomaa scored a point in 10th at the end of an issue packed weekend in the Autotek Ford, taking the place on the last stage when Peter van Merksteijn Jr's private Citroen broke a driveshaft.
None of the Minis made it into the top 10. Local hero Armindo Araujo's weekend went awry early when he crashed on Thursday night, and Prodrive's Patrik Sandell lost fourth place to damaged suspension on Saturday afternoon. Sandell's team-mate Dani Sordo took a number of stage wins as he flew under Rally 2 following Thursday evening electrical issues, although a later exhaust problem and punctures limited him to 12th at the finish. Sordo did at least get three points for winning the power stage.
Leading results: Pos Driver Team/Car Time/Gap 1. Mikko Hirvonen Citroen 4h19m24.3s 2. Mads Ostberg Adapta Ford + 1m51.8s 3. Evgeny Novikov M-Sport Ford + 3m25.0s 4. Petter Solberg Ford + 3m47.4s 5. Nasser Al-Attiyah Qatar Citroen + 7m57.6s 6. Martin Prokop Czech Ford + 8m01.0s 7. Dennis Kuipers M-Sport Ford + 8m39.1s 8. Sebastien Ogier VW Skoda + 9m00.8s 9. Thierry Neuville Citroen Junior + 10m29.7s 10. Jari Ketomaa Autotek Ford + 11m44.6s Other WRC finishers: 11. Peter van Merksteijn Jr van Merksteijn Citroen + 12m02.8s 12. Dani Sordo Prodrive Mini + 14m15.5s 13. Daniel Oliveira Brazil Ford + 16m54.1s 14. Jari-Matti Latvala Ford + 18m54.4s 15. Ott Tanak M-Sport Ford + 19m06.9s 16. Armindo Araujo Portugal Mini + 22m55.7s WRC retirements: Patrik Sandell Prodrive Mini SS21 Sebastien Loeb Citroen SS3 Leading power stage results: 1. Dani Sordo Prodrive Mini 3m10.4s 2. Jari-Matti Latvala Ford + 0.3s 3. Ott Tanak M-Sport Ford + 2.1s 4. Jari Ketomaa Autotek Ford + 8.8s 5. Petter Solberg Ford + 10.3s
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In today's complex financial world, many savvy shoppers can no longer afford to assume they know which methods of global money transfer really offer the best deals. Constantly evolving regulations, increasingly hidden fees and fluctuating currency exchange rates require real strategy to negotiate a good balance between convenience and price. In some circumstances, the most cost-effective method may involve stuffing an international money order into a courier envelope and sending it on an overseas voyage.
Taking Stock
The first important step is to ask a series of logistical questions: Is this a one time payment or might you need send more later? How soon does the money need to get there? Do you have a bank account or bank card? Does the recipient have a bank account or bank card? Does the recipient have access to online services? What currency will the recipient need? Are you concerned only with front-end costs or those of the whole process?
Finding and Comparing Fees
In order to understand and compare all applicable fees, break each money transfer option down according to user and recipient fees. These options include mail/courier, bank account transfer, money transfer services, bankcard transfers and some combination thereof.
Although initially only an issue for travelers abroad, currency conversion costs are an increasingly important factor all bankcard purchases . According to the "Ecommerce Journal," the definition given by financial services companies of "foreign transaction fees" has been expanding since 2006. These fees can appear as hidden charges on credit card transactions and have been surprising many customers when their bills arrive. They are subject to appear anytime currency conversion is linked to bank card activity even if the purchaser is in the U.S.
A general rule of thumb is that any time a bankcard is involved in the process, the fees climb exorbitantly. One surprising exception, especially when the purchaser does not have a bank account, may be a pre-paid or load card.
Who Are The Money Transfer Companies?
The major money transfer companies in the United States are MoneyGram, Western Union and PayPal. All three have wonderful websites that allow you to see what countries you can send funds to and compare rates. There are still some countries, especially in Africa, not served by the big three. If you don't find the destination you are looking for on these provider sites, check with online alternatives such as Ikobo and Xoom.
Special Considerations
Many customers without bank accounts use agent offices for sending funds because they need to pay in cash. This is not necessarily the best option available, nor is it the cheapest. If both sender and recipient have Internet access, a combination of a pre-paid card offered by green dot MoneyPak and PayPal international transfer service might be the best bargain. PayPal does require that the recipient sign up for a PayPal account and the rules for recipient access to funds varies in many countries.


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By being different I mean by I'm different in my group... All of my friends love soccer playing soccer and I dont like soccer. I like riding the bicycle and going to gym. None of my friends play musical instruments, I play the guitar. These are some examples. So... Is being different a good thing or a bad thing?
Most Helpful Girl
I guess I'd go with neutral. I mean, it's totally not a bad thing don't get me wrong. Just be yourself, be unique. Being the same is way too mainstream.10|10|0
Thank you 😊


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The Campfire range of stainless steel Whistling Kettles will bring style and colour to your camp or on-the-road kitchen. They are of a stylish and modern design ideal for home, caravan and camping.
• Made of rustproof stainless steel which will stand up to high temperatures and constant use
• Features a whistling Bakelite nozzle and an encapsulated base to reduce boiling time
• Also a compact folding handle to enable easy storage in limited space
• Cool to touch Bakelite handle
• Available in two sizes: 2.5L and 4.0L and various colours
In particular, the base diameter
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