Photoinduced Split of the Cavity Mode in Photonic Crystals Based on Porous Silicon Filled with Photochromic Azobenzene-Containing Substances

Abstract

Phototunable photonic structures based on electrochemically etched silicon filled with four photochromic azobenzene-containing compounds, a bent-shaped low-molar-mass substance and side-chain polymethacrylates and a copolyacrylate, were prepared, and their photo-optical properties were studied. It was found that irradiation of these composites with polarized blue light results in spectral changes in the photonic band gap (split of the cavity mode) associated with cooperative photo-orientation of azobenzene moieties inside silicon pores in the direction perpendicular to the polarization plane of the incident light. Kinetics of the photoinduced split is studied. The observed photoinduced split is completely reversible, and heating of the composites to temperatures above isotropization or glass transitions fully recovers the initial spectral shape of the photonic band gap. Thermal and temporal stabilities of the obtained photoinduced split were comparatively studied, and it was found that for composites with a bent-shaped substance and polymethacrylate shape of the reflectance spectra do not change over time at room temperature. The prepared composites have a high potential for the different applications in photonics.