Direct Writing in Polymers with Femtosecond Laser Pulses: Physics and Applications

Nonlinear optical phenomena in the optical spectral range followed by the invention of laser in early 1960’s directed the generation of optical pulses using Q switching and mode locking techniques. Ultrafast lasers with extremely short pulse duration (<100 fs) opened a new avenue towards fabrication of integrated photonic and signal processing devices in a variety of transparent materials. A new approach for the local modification of transparent materials through nonlinear optical processes has been investigated due to extraordinarily high peak intensities of short pulses. A variety of materials including metals, dielectrics, polymers, and semiconductors have been successfully processed by the use of fs pulses [1-14]. Bulk refractive index change in transparent materials is found to be useful in applications of waveguides. Various applications resulting from fs laser writing of different materials, especially in polymers, have been successfully demonstrated in the fields of micro-fluidics, bio-photonics, and photonics etc. [15-32]. The minimal damage arising from the generation of stress waves, thermal conduction, or melting has proved to be one of the main responsible mechanisms for various applications demonstrated using fs laser micromachining. In the present chapter we discuss the formation of free radicals and defects which are responsible for emission in polymer systems. The impact of fs lasers pulses causing minimal damage can be utilized to fabricate emissive micro-craters, especially in polymers. These emissive microcraters find prospective applications in memory based devices.