All-chalcogenide middle infrared dielectric reflector and filter

We have fabricated a dielectric reflector and a passband filter, both with first order photonic bandgaps in the middle-infrared region around lambda = 4 mu m. The devices were made from alternating amorphous Ge(25)S(75) and Ge(15)Te(85) chalcogenide films with high transparency in the middle infrared region stacked in multilayers. Due to high thickness accuracy and periodicity of prepared multilayers we also observed second order photonic bandgaps at lambda similar to 1.4 mu m. The experimental data were in good agreement with theoretical predictions. The work focused on investigation of compositional homogeneity. surface roughness, thermal and optical properties of individual amorphous Ge(25)S(75) and Ge(15)Te(85) films. We confirmed chalcogenide materials as being of suitable choice for designing middle-infrared quarter wave stack devices. FT-IR reflectance spectra confirmed occurrence of 99.4% stopband near X = 4 mu m for fabricated reflector and narrow similar to 50% passband of prepared filter near lambda = 3.934 mu m. (C) 2010 Elsevier B.V. All rights reserved.