Large area three-dimensional photonic crystals with embedded waveguides

Abstract

Three-dimensional photonic crystals are attractive for very compact waveguide devices. A novel interferometric lithography technique for fabricating three-dimensional photonic crystals is presented, which allows for independent dimensional control of each axis of the crystal. Previous interferometric approaches using 3, 4, 5, or more beams have inherent constraints between the lattice constants and the exposure wavelength. With this new technique, it is possible to control each individual crystal lattice constant largely independent of the exposure wavelength, vastly increasing the available parameter space. Both mathematical models and experimentally realized three-dimensional photonic crystals, over 2 cm2 in size and up to 12 μm, are presented. Photonic crystals with integrated waveguides are of particular significance. A new approach to fabricating waveguides embedded in a three-dimensional photonic crystal is also presented. This approach uses multiple-exposure wavelengths, with one longer wavelength propagating throughout the photoresist for the photonic crystal fabrication and another shorter highly absorptive wavelength for the waveguide fabrication. This new approach to waveguide fabrication leads itself to scalable manufacturing using standard semiconductor lithography equipment.