Structural and optical characterization of Ag photo-doped thin As₄₀S_{60 −x}Se_xfilms for non-linear applications

Abstract

This paper deals with the structure and the optical properties of thin As40S60 − xSex films doped with silver. The refractive index n and the optical band gap Egopt were calculated from the transmittance and reflectance spectra. The results showed that the photo-doping leads to increase in the refractive index by about 0.25–0.27. An effect of thickness expansion was observed in the photo-doped layers. The non-linear refractive index, γ, and the two-photon absorption coefficient, β, were evaluated by applying a formula developed by Sheik-Bahae. Each of the films studied exhibits a highly non-linear refractive index at the telecommunication wavelength, 70–850 times higher than that measured for fused silica. From the Raman spectra of thin As40S30Se30 it might be concluded that under dissolution, the silver interacts with both sulfur and selenium. The surface of the thin films was investigated by using a white light interferometric profiler. It was found that the increase in the thickness of the silver layer results in roughening of the surface of the photo-doped films.

Absorption Edge and Optical Band Gap of Ag-As40S30Se30Amorphous Samples

“…However, it is a common phenomenon with chalcogenide glassy semiconductors that many properties of bulks are dierent from those of the lms of the same composition. A similar value of the band gap for the lm of the glass As 40 S 30 Se 30 was also reported by some other authors (2.01 eV) [6,7] and (2.08 eV) [8]. The same trend of the change in the value of E g with silver doping was also found in some other systems such as AgAsSe [9], AgAsS [10] and AgAsSSe [1,11].…”

Compositional dependence of optical parameters in Se–Bi–Te–Ag thin films

“…It is observed that for the entire spectral range, the refractive index increases with the increasing Ag concentration. Similar results for Ag doped ternary thin films are reported [31][32][33] in the literature. The accuracy of the refractive index may be increased by calculating the film thickness using basic interference equation…”

Thin Chalcogenide Films for Photonic Applications

“…Compositional variation of the refractive index and optical band-gap of chalcogenide glass thin films. The data depicted is taken from own studies and published elsewhere (Todorov et al, 2001(Todorov et al, , 2003Tasseva et al, 2005Tasseva et al, , 2007Tasseva et al, , 2010Kincl et al, 2009;Knotek et al, 2009;Petkov et al , 2009). …”