Influence of electro-chemical etching parameters on the reflectance spectra of porous silicon rugate filters

Today the porous silicon photonic crystals are widely used as components of the optical sensors. The structures with the resonance properties, e.g. a narrow reflection band, which provides high sensitivity of the device, generate considerable interest. One of the most interesting structures of this type are rugate filters. Rugate filter is a photonic crystal with a gradually varying under harmonic law index of refraction and narrow spectral reflection band. In this paper, we present our results of the optimization of silicon electrochemical etching parameters, in order to fabricate filters in a visible spectral range with reflection bandwidth of less than 30 nm and a reflectance higher than 80%.