Chapter 18 Femtosecond fabrication of photonic crystals inside a bulk polymer material

5. Summary Previous work on the generation of voids inside transparent material by ultrashort pulsed light has solely been from a data storage point of view, where only single void bits were generated. Here we have presented void channels inside a bulk polymer material and have used them in the application of two and three-dimensional photonic crystal structures. This work involved the characterisation of the response of a specific polymer material, NOA63 optical adhesive to a scanned femtosecond pulsed high repetition rate light beam. The size of individual void channels as well as the overall structure of woodpile type photonic crystals was controlled accurately. The high degree of perfection of these photonic crystals allowed for the observation of the fundamental as well as higher-order stop gaps. The benefits of fabricating photonic crystals based on void channels are numerous. Unlike other techniques the time to fabricate a structure is on the order of minutes. Polymer shrinkage has no effect and wash out or other chemical post etching is not required, unless higher dielectric contrasts for complete bandgaps are desired. In conclusion, this method is a fast, one step, and highly accurate technique suitable to fabricate a large variety of photonic crystals and micro-devices in polymers.