Arsenic sulfide layers for dielectric reflection mirrors prepared from solution

摘要

Chalcogenide materials due to high refractive indices, transparency in the mid-IR spectral region, nonlinear refractive indices, etc, have been employed as fibers and films in different photonic devices such as light amplifiers, optical regenerators, broadband radiation sources, etc. Chalcogenide films can be prepared by physical methods as well as by solution-based techniques in which solutions of chalcogenides in amines are used. This paper presents results on the solution-based fabrication and optical characterization of single arsenic sulfide layers and multilayer stacks consisting of alternating As_2S_3 layers and porous silica layers and coated on planar and fiber-optic substrates. Input As_2S_3 solutions for the layer fabrications were prepared by dissolving As_2S_3 powder in n-propylamine in a concentration of 0.50 mol/l. These solutions were applied on glass slides by dip-coating method and obtained layers were thermally treated at temperatures up to 180 °C. Similar procedure was used for As_2S_3 layers in multilayer stacks which were fabricated by repeating the application of one As_2S_3 layer and one porous silica layer onto glass slides by dip-coating method. The same approach was used for the preparation of the stack on a silica fiber (a diameter of 0.3 mm). It has been found that the thermal treatment of the applied layers has to be carefully controlled in order to obtain stacks with three pairs of such layers. Single arsenic and porous silica layers were characterized by optical microscopy, and by measuring their transmission spectra in a range of 200-2500 nm. Thicknesses and refractive indices were estimated from the spectra. Transmission spectra of planar multilayer stacks were measured, too. Interference bands in a spectral range of 400-900 nm have been observed in transmission spectra of the multilayer stacks with a minimum transmittance of about 50% which indicates the possibility of using such stacks as reflecting mirrors.