Design, fabrication, and characterization of 3D photonic crystals constructed from low-index polymers

Abstract

We theoretically investigate the superprism effect in a polymer "woodpile" photonic crystal structure. We find that the common degeneracy problem caused by low index contrast can be avoided at certain frequency range. As a result, polymer materials such like photoresist manifest their potential for high performance superprism. We study the superprism effect for 3^rd and 4^th bands at frequency 0.94c/a using plane wave expansion method. In both cases, the wave propagation direction changes rapidly responding to variation of incident angle. Up to 30 degree of output angle variation for 1 degree of incident angle increment has been observed. We also find an average of 10 degrees shift of output angle for 1% variation of the incident wavelength. We fabricated the proposed "woodpile" structure based on multilayer 3D photolithography. This method, which uses commercially available photoresist, allows batch fabrication of 3D photonic crystals (PhCs), possesses the flexibility to create a variety of different lattice arrangements and the scalability for different operation wavelengths. We describe in this paper how to achieve 3D confined exposure and multiple resist application. We show the fabricated devices for both mid-infrared and telecom applications.