Experimental verification of the applicability of the homogenization approximation to rough one-dimensional photonic crystals using a holographically fabricated reflection grating

Abstract

The theoretical reflectance spectrum of a one-dimensional photonic crystal with large amounts of interfacial roughness has been calculated using a previously proposed method, and compared to the actual experimental reflectivity of the structure. The photonic crystal was fabricated using a simple and fast method involving the holographic exposure of a liquid crystal/photosensitive prepolymer syrup via the self-interference patterns from two laser beams. The calculated reflectance spectrum for this structure matched the experimental one extremely well, giving very similar reflectivity peak positions and intensities. Slight discrepancies between the two reflectance spectra are attributed to either small variations in the microstructure of the reflection grating beyond that which is captured in the transmission electron micrograph, or the dispersion of the polymer which was not taken into account. These results serve as experimental verification of the theory for rough photonic crystals reported previously.

Fabrication of Silicon Surface Grating Structures by Maskless Laser Beam Lithography

“…In recent years, development of high pulse-energy and high peak power lasers, particularly in the UV range, has led to resurgence of interest in direct writing of surface or subsurface gratings on variety of materials and development of very attractive alternative technology known as laser interference lithography or holography lithography. It is a preferred method to fabricate the periodic structures, as it is a relatively simple and mask-less method, utilizing the interference of two or more coherent beams, and ideal for low cost and large area exposure [5][6][7][8]. It has advantage over other techniques, provides flexibility in grating period and depth by changing the incident angles and irradiation time.…”