nonlinear dispersive terms are ubiquitous to nature. Studies involving an additional nonlinear term have shown that such terms have a profound effect on wave packet, including amongst other things, a self-steepening of the wave packet. The non-linear aspects eventually lead to optical solitons. Despite being rather common, the SVEA is not required to formulate a simple wave equation describing the propagation of optical pulses. In fact, as shown in, even a very general form of the electromagnetic second order wave equation can be factorized into directional components, providing access to a single first order wave equation for the field itself, rather than an envelope. This requires only an assumption that the field evolution is slow on the scale of a wavelength, and does not restrict the bandwidth of the pulse at all—as demonstrated vividly by. High harmonics High energy ultrashort pulses can be generated through high harmonic generation in a nonlinear medium. A high intensity ultrashort pulse will generate an array of harmonics in the medium; a particular harmonic of interest is then selected with a monochromator. This technique has been used to produce ultrashort pulses in the extreme ultraviolet and soft-X-ray regimes from near infrared Ti-sapphire laser pulses. Applications Advanced material 3D micro-/nano-processing The ability of femtosecond lasers to efficiently fabricate complex structures and devices for a wide variety of applications has been extensively studied during the last decade. State-of-the-art laser processing techniques with ultrashort light pulses can be used to structure materials with a sub-micrometer resolution. Direct laser writing (DLW) of suitable photoresists and other transparent media can create intricate three-dimensional photonic crystals (PhC), micro-optical components, gratings, tissue engineering (TE) scaffolds and optical waveguides. Such structures are potentially useful for empowering next-generation applications in telecommunications and bioengineering that rely on the creation of increasingly sophisticated miniature parts. The precision, fabrication speed and versatility of ultrafast laser processing make it well placed to become a vital industrial tool for manufacturing. Micro-machining Among the applications of femtosecond laser, the microtexturization of implant surfaces have been experimented for the enhancement of the bone formation around zirconia dental implants. The technique demonstrated to be precise with a very low thermal damage and with the reduction of the surface contaminants. Posterior animal studies demonstrated that the increase on the oxygen layer and the micro and nanofeatures created by the microtexturing with femtosecond laser resulted in higher rates of bone formation, higher bone density