Linear and nonlinear optical properties of GeSe2-xSnx (0 ≤ x ≤ 0.8) thin films for optoelectronic applications

The linear optical properties of amorphous GeSe2-xSnx (where 0 ≤ x ≤ 0.8) films were studied using spectrophotometric measurements of transmittance (T) and reflectance (R) at typical frequencies of light in the wavelength range of 200-2500 nm. Structural properties affirm the amorphous nature of these films. Our investigations of the linear optical properties showed that the optical band gap decreases and the refractive index increases with an increase in Sn content in the Ge-Se system. It was found that the third-order nonlinear optical susceptibility is a function of Sn in the Ge-Se system. The values of the third-order nonlinear optical susceptibility increased with an increase in Sn content. The enhancement in the susceptibility of GeSe2-xSnx films (0 ≤ x ≤ 0.8) with an increase in Sn content could be explained in terms of the absorption edge.