Optimization of thickness and uniformity of photonic structures fabricated by interference lithography

We study the influence of the absorption of materials used for holographic fabrication of photonic structures on their uniformity along the film thickness. We demonstrate theoretically and experimentally a strong dependence of structure thickness and uniformity on the exposure dose of the interference pattern. A novel technique is proposed to overcome the absorption effect and to fabricate thick two- and three-dimensional structures, which are uniform throughout the film thickness. It consists of exposing once again the sample by an additional and independent counterpropagating uniform beam, which allows to compensate the diminution of the light intensity of interference pattern. These results are very useful for the fabrication of high quality polymer-based photonic crystals.