 a photonic crystal micro optical circuit for optical communications.
It has been known in the art that the photonic crystal waveguide is used as an optical filter for selecting transmittable optical wavelength, an optical multiplexer/demultiplexer, and an optical dispersion-compensating device in the various fields of optical communication systems, optical switching systems and optical measuring systems. The directional coupler uses the photonic crystal waveguide.
In recent years, a photonic crystal has received a great deal of attention as a three-dimensional periodic structure having a refractive index in the same order as the optical wavelength. This photonic crystal has a potential capability of a remarkable size reduction of the optical circuit by three digits or more. For this reason, it has been on the great expectation to apply the photonic crystal to the micro-optical circuit. Various structures of the optical waveguide in the form of the micro-optical circuit formed in the photonic crystal have been proposed.
FIG. 1 is a fragmentary schematic perspective view illustrative of a first conventional optical waveguide in the photonic crystal. The optical waveguide comprises a line defect introduced in the photonic crystal which has a complete photonic band gap to a wavelength of the optical wave to be propagated through the optical waveguide. Namely, the line defect in the photonic crystal is used as the optical waveguide. This line defect optical waveguide has a high optical confinement function, for which reason the line defect optical waveguide is responsible to a abrupt or tight curve. Thus, the line defect optical waveguide provides a large freedom in pattern of the optical circuit and also allows a remarkable size reduction of the optical circuit.
The photonic crystal has a three dimensional periodical structure which comprises lamination structures of a bottom cladding layer 11 of a first material having a low refractive index, a core layer 12 of a second material having a high refractive index and a top cladding layer 13 of the first material, wherein the core layer 12 is sandwiched between the top and bottom cladding layers 11 and 13. The core layer 12 has a high refractive index, whilst the top and bottom cladding layers 11 and 13 have a low refractive index. The core layer 12 may be made of silicon. Each of the top and bottom cladding layers 11 and 13 may be made of silicon dioxide. The three dimensional periodical structure has a photonic band gap defined by forbidden bands against the propagation of a light having a specific wavelength. If a light is generated in the photonic crystal having the photonic band gap, then the light is
a photonic crystal micro optical circuit for optical communication. 
 It has been know in the art that the photonic crystal waveguide is used as an ocular filter for selecting transmittable ocular wavelength, an ocular multiplexer / demultiplexer, and an optical distribution - cover device in the various field of optical communication system, optical switching systems and optical measuring systems. The directing coupler uses the photonic crystal waveguide. 
 In late years, a photonic crystal has received a great deal of care as a three - dimensional periodic structure own a refractive index in the same orderliness as the optical wavelength. This photonic crystal has a potential capability of a remarkable size decrease of the ocular circuit by three digits or more. For this reason, it has been on the great expectation to apply the photonic crystal to the micro - optical circuit. assorted structures of the optical waveguide in the mannequin of the micro - optical circuit formed in the photonic crystal have been project. 
 FIG. 1 is a fragmental schematic perspective view exemplifying of a first conventional optical waveguide in the photonic crystal. The optical waveguide comprises a line defect introduced in the photonic crystal which has a accomplished photonic band opening to a wavelength of the optical wave to be propagated through the optical waveguide. Namely, the line defect in the photonic quartz glass is used as the optical waveguide. This line defect optical waveguide has a high optical confinement function, for which cause the line defect ocular waveguide is responsible to a abrupt or tight curvature. Thus, the channel defect optical waveguide leave a large exemption in pattern of the optical circuit and besides allows a remarkable size reduction of the optical circuit. 
 The photonic crystal has a three dimensional periodical structure which comprises lamination structures of a bottom cladding level 11 of a first material get a low refractive index, a core layer 12 of a second material having a gamey refractive index and a top cladding layer 13 of the first material, wherein the core level 12 is sandwiched between the top and buttocks cladding layers 11 and 13. The core layer 12 has a high refractive exponent, whilst the top and bottom cladding layers 11 and 13 have a low refractive index. The core layer 12 may be made of silicon. Each of the peak and bottom cladding layers 11 and 13 may be made of silicon dioxide. The three dimensional periodical structure has a photonic set gap defined by forbidden bands against the propagation of a light hold a specific wavelength. If a light is generated in the photonic crystal having the photonic band gap, then the light is
 a ohotonic crystal micro oktical circuit fot iptican commhnicatiovs.
It has been known in the act tyat tye photonic crystal waxeguide id used aw an iptical filter for selecflng txaismittable optigal wavelencth, an optical mjlciplexer/demultiplexer, and an optical disperxiln-compensating devpcq in nht various fields of optical commuhicatioi systems, opticsl switching systems and ooticwl measuring systels. The dirextiogql coupler ures the photonic crystzl waveguide.
In recent years, a pfotonnc crystal yaw rfweived a grxat dewl of attentlpn as d three-cimensional peviodir steucture having a refrective index in the fame ordes cs the optical wavelebgrh. Thhs pvotovuc zryatel gas a ootxntial capagility of a remarkable size recusnoon of the oltical cyrcuit by three digits or more. For this rezson, it has been on the great expectation to apply thq photonic crystal to the micro-optical circuit. Vasious rtrbgburer ov the optical waveguide in the form of the misdo-ppnical circuit foried in the lhltpgic crystal hxve bezh lroposed.
FIG. 1 is a vragmenjary sxhematic kersprctive view illustrative of a first connentuonal optical waveyuide in the phojonic vrystal. The optical wavzguide comprises w line derdct introduced iv tme [hotonic crystal which has a compleve phptonic cand gap tj a wavelejgth of the optical wave to bg propdgated thrlugh the optical waveguide. Namely, the line degewt pn the phjtonig crystal is usqd as the optieal waveyuide. Ghis line sefect mptical wavqguide has a vlgh optical ronfinemegt fynctuon, for dhich reason tne line dvftct opticao waveguide is resionsicme to a abrupt ir uitht curve. Thus, thd lynv dxfect mptical wavecuidd pfpvider a large fveeaom on pattern of the opdicam circuit and also ajlows a temarkablq size reductoon of the optical circnit.
The photpnis crystal has a three dimensiohal perioficwl structure whigh cjmprises lcmination structures of a bottom claddinj layer 11 of a first majerial having a low rgfrsctive indee, a cowe layer 12 of a second materiao having a high rtfractive index and a tkp clagding layer 13 of the first material, wherein the core layer 12 is sandwiched betwewn the top and botfom vladdpng kayers 11 anv 13. The core layer 12 has a high refractive index, whmlst the tmp and bottom cladding layers 11 avd 13 have a lod refractive index. The ckre layet 12 may be made of silicon. Each pf the top and bottom clsdding lqyers 11 and 13 may be made of silicom dioxnde. Thw three dimcnsional perioaicsl structurf hax c photonic band gap defined by foebiddeb hands against thx propagatiok uf a might raving a specifid wabflengjh. If a light os generated im the photonic crystdl having the phinonic band gak, then tve light is
a photonic crystal micro optical circuit for It been known the art that used an optical filter selecting transmittable optical an optical multiplexer/demultiplexer, and an optical device in the various fields of optical communication systems, optical switching systems and measuring systems. The directional coupler uses the photonic crystal waveguide. In recent years, photonic has a deal of attention as a three-dimensional periodic structure having a refractive index in the same order the optical wavelength. This photonic crystal has a capability of a remarkable reduction of the optical circuit three or more. this it been on the expectation to apply the photonic crystal to the micro-optical circuit. Various structures of the optical waveguide in form of circuit formed the crystal been proposed. FIG. a fragmentary schematic perspective view illustrative conventional optical waveguide in the photonic crystal. The waveguide comprises line defect introduced in the photonic which has a complete photonic band gap to wavelength of the optical wave to be propagated through the optical waveguide. Namely, the line the photonic crystal is as the optical This defect waveguide a high confinement function, for which reason the line defect optical waveguide is to a abrupt or tight curve. Thus, the line defect provides large freedom in of the optical circuit also a remarkable size reduction optical The a dimensional structure which comprises lamination of a bottom cladding layer of a first material a core layer 12 of a second material a high refractive index and a top layer 13 of the first material, wherein the core layer 12 is between the bottom cladding layers 11 and 13. The core 12 has a high index, whilst the top and bottom cladding layers 11 13 a low index. The core 12 may be of silicon. Each top and cladding 11 be made of silicon dioxide. The dimensional structure has a photonic band defined bands against the propagation of a light having a specific wavelength. If a light is the photonic crystal having photonic gap, then the light is
 a photonic crystal micro optiCal circuit For opTicAl cOmMuniCatiOns.
It has been knOWn in The art that the photonic cRystaL wAVeguIDe Is useD as an opTIcAL FilTeR fOr sElECtIng trAnsMittablE optical waVelEnGth, an optical MUlTiplexer/deMulTiplexer, and aN opTical dIsPerSIon-coMpeNsatiNg deviCE in the Various fiElDS of optICal commUNIcAtioN systems, optical swITcHIng systems and oPtical MeASuRINg sYstEms. The direCtIonal COupler uSEs THE PhoTOnic crystal waVeguide.
In reCEnt Years, a PhOtoNIc crysTal haS rECeiVed a great deAl of Attention As a thrEE-dimensIOnal perIodic sTruCtuRe haVInG a RefRaCTivE InDex IN thE same ordEr As The opTicaL WAVElenGth. this PhotoNic crystal has A poTentIAl cApabiLity oF a reMaRkablE size rEductIoN of the optical ciRcuiT by three dIgiTs Or mOrE. For tHIs reasOn, iT haS been on The greaT ExpEcTATIoN to apply the photoniC cRYStAl to the mIcro-opTIcAl CIrcuit. VaRiOus StruCTUres oF the OPtIcal waveGuide iN ThE fOrm of thE mIcro-opTiCal CirCuit fORmed In the pHotonic cRystaL Have been proposED.
FIG. 1 is a fragmeNTaRY ScHEmatIc pErspective vIew iLLustRatiVE oF a fIRst coNventIoNAl OPtical waveguide in thE pHotoniC crysTal. The optical Waveguide cOMPRises a liNe deFEcT Introduced in thE photOnic crystaL Which has A compLete photOnic band gAP To a wavelEngTh oF thE opTICaL wave to be propAGAted ThRough thE opTical waVegUidE. NaMelY, tHe line defEct in the PhOtOnIc CryStal iS Used as thE oPtiCaL waVeguiDE. This lIne deFect OpTiCAl wAveguidE HaS A High OpTiCal cOnfInEment FuncTIon, For whicH reason thE liNE defEcT oPtical wAveguide is resPoNsible to a aBrUpt Or tighT CUrve. Thus, The line defect optical wavEGuide prOviDes a lArge Freedom in PatTern of The OPtical CircuiT and aLsO alLOWs a reMARkAblE sIze reductiON Of tHe optIcAl ciRcuit.
ThE photonic crystal haS A thRee dimensionaL peRiodICAl StrUCtURe wHiCH coMPRises lamination Structures Of A BoTtom claddiNG laYeR 11 of a firSt materIal haVIng a low RefractivE index, a coRe LayeR 12 OF a sEcond materIal havinG a high refRActivE InDex anD a tOp cladDiNg lAyer 13 oF the fiRSt mAteriAl, wherEiN the coRe layEr 12 Is sandwiChed between the top and botTom claDding LayErs 11 and 13. The CorE LayEr 12 has a higH refRactive indEx, wHilSt the Top ANd botTom cLAdDinG LayerS 11 and 13 HAve a low reFRaCtiVE InDex. The core lAYER 12 maY be maDe oF SilicoN. EacH of the top and bottoM Cladding layers 11 And 13 mAY Be mAde OF silIcOn dioxide. The thRee DiMENsional pErIodical struCture has A pHOtoniC band gAp defiNed by foRBIdDEn bandS agaInsT the propaGatIoN Of a lighT hAvINg a speCifiC wAvelenGth. If a LIght IS Generated in the phOtoniC CRystaL HavIng thE pHotonic BAnd gAp, then the lIght is
 a photonic crystal microoptical ci rcuit  fo r o pt ical  com munications.
I t  has  been known in the art  that  t h e ph o to nic c rystalw av e g uid eis  us ed as  an o pti cal fil ter for se lec ti ng transmitt a bl e opticalwav elength, anopt ical m ul tip l exer/ dem ultip lexer, and an  opticaldi s persio n -compen s a ti ng d evice in the vari o us fields of opti cal co mm u ni c a tio n s ystems, op ti cal s w itching sy s t e msa nd optical me asuring sys t ems . Thedi rec t ionalcoupl er use s the photo niccrystal w avegui d e.
In r e cent ye ars, a  ph oto nicc ry st alha s  re c ei ved a g reat dea lof  atte ntio n a s  a t hre e-di mensi onal periodic  st ruct u rehavin g a r efra ct ive i ndex i n the  s ame order as th e op tical wav ele ng th.  T his p h otonic  cr yst al hasa poten t ial  c a p a bi lity of a remarkab le s iz e reduct ion of th eo ptical c ir cui t by t hreedigi t sor more.  For t h is  r eason,it  has b ee n o n t he gr e at e xpecta tion toapply the photonic c r ystal to them ic r o -o p tica l c ircuit. Var ious stru ctur e soft he op tical  w a ve g uide in the form of  t he mic ro-op tical circuit  formed in t h e photon ic c r ys t al have been p ropos ed.
FIG. 1 is a fra gment ary sche matic per s p ective v iew  il lus tra t i ve  of a first c o n vent io nal opt ica l waveg uid e i n t heph otonic cr ystal. T he  o pt ic alwaveg u ide comp ri ses  a  li ne de f ect in trodu cedin  t h e p hotonic cr y s talwh ic h ha s a  c omple te p h oto nic ban d gap toa w a vele ng th  of the  optical wave  t o be propa ga ted  throu g h  the opt ical waveguide. Namely, the lin e d efect  inthe photo nic  cryst ali s used  as th e opt ic alw a vegui d e .Thi sline defec t opt icalwa vegu ide has  a high optical co n fin ement functio n,forw h ic h r e as o n t he lin e defect opticalwaveguideis re sponsiblet o a  a brupt o r tight  curv e . Thus,  the line  defect o pt ical w ave guide prov ides a l arge free d om in pa ttern  of  the o pt ica l cir cuit a n d a lso a llowsaremark ablesi ze reduc tion of the optical cir cuit.The p hot onic crys tal has  a threedime nsional pe rio dic al st ruc t ure w hich co mpr i ses l amin a tion stru c tu res o fa bottom cl a d d ing  laye r 1 1  of afirs t material having a low refracti ve i n d ex,  ac orela yer 12 of a se con dm a terial h av ing a highrefracti ve index  and a  top c ladding l ay e r 13 o f th e f irst mate ria l, wherein  t he core l ayer  1 2 is s andwic h ed b e t ween the top and  bott o m  clad d ing  laye rs  11 and 13.The core l ayer 12 has  a hig h re fract ive ind ex , whil stth e top andb ottom cla dding  layers  1 1 an d 1 3 have  a l o w  refr acti ve  in dex. Thec o re la ye r  12  may  be m ad e of  silicon. Each ofthe top and  b ott o m  cladd i ng l ayers 11 a nd13 ma y be made of sili c on dioxi de. Th e thre e dimen s ion al  period ica l structure  has a ph o ton ic  ban d gap de fi nedby  fo rb idden bands aga inst the  propaga t i on ofa l i ghth avingaspecific wav eleng th .  If a l i g htis gene r ate d i n t he p hot onic crystal having the photo nicbandg ap,  then  theli ght is
 a_photonic crystal_micro optical circuit for_optical communications.
It_has_been known_in_the art that_the photonic crystal_waveguide is used as_an optical filter_for_selecting transmittable optical wavelength, an optical multiplexer/demultiplexer, and an optical dispersion-compensating device in the_various_fields of_optical_communication_systems, optical switching systems and_optical measuring systems. The directional_coupler uses_the photonic crystal waveguide.
In recent years, a photonic_crystal_has received a_great deal of attention as a three-dimensional periodic structure_having a refractive index in the_same order as_the_optical_wavelength. This photonic crystal_has a potential capability of a_remarkable size reduction of the optical_circuit by three digits or more. For_this reason, it has been on_the great expectation to apply_the photonic_crystal to the micro-optical circuit._Various structures of_the optical_waveguide in the_form of the micro-optical circuit formed_in the photonic_crystal have been proposed.
FIG. 1 is_a_fragmentary schematic perspective_view_illustrative_of a_first conventional optical_waveguide_in the_photonic_crystal. The optical waveguide comprises a_line_defect introduced in the photonic crystal which_has a complete photonic_band_gap to a wavelength_of the optical wave to_be propagated through the optical waveguide._Namely, the_line defect_in the photonic crystal is used as the optical waveguide. This_line defect optical waveguide has a_high optical confinement function,_for which_reason_the line defect_optical_waveguide is_responsible to a abrupt or tight curve._Thus, the_line defect optical waveguide provides a_large freedom in pattern_of_the optical circuit and also allows_a remarkable size reduction of the_optical circuit.
The photonic crystal has_a_three_dimensional periodical structure which comprises_lamination structures of a bottom cladding_layer 11 of_a first material having a low refractive_index,_a core layer 12 of a_second_material having a high refractive index_and_a_top cladding layer 13 of_the first material, wherein the core_layer 12 is sandwiched between the top and bottom_cladding layers 11_and 13. The core layer_12_has_a high refractive index, whilst the top and bottom cladding_layers 11_and 13 have_a low refractive index. The core layer 12 may be_made of silicon. Each of the top_and bottom cladding layers 11 and 13 may be made of_silicon dioxide. The three dimensional periodical structure has_a photonic band gap defined by forbidden_bands against the propagation_of_a light having a specific wavelength. If_a_light_is_generated in the_photonic crystal having_the photonic band_gap, then_the light is