Void channel microstructures in resin solids as an efficient way to infrared photonic crystals

Microvoid channels were generated by local melting in a solidified polymer resin sample moving perpendicular to the focus of a high numerical-aperture objective under visible femtosecond-pulsed illumination. Channel size, surface quality, and high density channel vicinity depended on laser intensity and scanning speed. Electron microscope images revealed elliptical channel cross sections of 0.7-1.3 mum in lateral diameter and an elongation in the focusing direction of approximately 50%. A 20 layer woodpile-type photonic crystal structure with a 1.7 mum layer spacing and a 1.8 mum in-plane channel spacing provided a sharp peak in reflection and a suppression of infrared transmission in the stacking direction by 85% at wavelength 4.8 mum with a gap/midgap ratio of 0.11. (C) 2003 American Institute of Physics.