Planar chalcogenide quarter wave stack filter for near-infrared

A quarter wave stack dielectric filter with normal incidence pass band in near-infrared range was prepared from alternating high index contrast chalcogenide films. The prepared filter consists of a low index Ge-S spacer layer surrounded by two 4.0 pairs Sb-Se/Ge-S reflectors. Films were deposited using flash and thermal evaporation techniques. After deposition, the filter was annealed at 165 °C for 1 h. Optical reflectivity measurements of the annealed filter revealed a ∼63% normal incidence passband near 1540 nm. An ∼80% passband was recorded after illumination of the filter by the light with s-polarization at angles 35°, 45° and 55°, while its position shifted to 1451, 1476 and 1505 nm, respectively. A ∼75% passband appeared near 1436, 1467 and 1498 nm in response to illumination of the filter by the light with p-polarization at the same angles. The angular dependence of the reflectivity of dielectric multilayer can be exploited for filtering of incident light.