Fabrication of Ge-ZnS multilayered optical filters for mid-infrared applications

Germanium/Zinc Sulphide (Ge/ZnS) single and multilayers are deposited by ion assisted electron beam deposition on Silicon substrates for applications in the 2-15 mu m wavelength region. Refractive indices of Ge and ZnS thin films are extracted from measured reflectance and transmittance spectra. Several types of mid-infrared filters (high-, anti-reflection coatings and dichroic filters) with a number of layers ranging from 3 to 29 are then designed and deposited. The optical responses of fabricated mid-infrared filters show a good agreement between experimental spectra and simulation in the case of highand anti-reflection coatings in the long-wave infrared but also for dichroic filters with a low transmittance in the mid-wave infrared and broadband bandpass in the long-wave infrared.

Automated summary

Germanium/Zinc Sulphide (Ge/ZnS) single and multilayers were deposited on Silicon substrates using ion assisted electron beam deposition for applications in the 2-15 μm wavelength region. Refractive indices of Ge and ZnS films were determined from measured reflectance and transmittance spectra. Mid-infrared filters with designs ranging from 3 to 29 layers, including high-, anti-reflection coatings and dichroic filters, were successfully fabricated, with experimental spectra showing good agreement with simulations, particularly in the long-wave infrared region.