Thallium indium germanium sulphide (TlInGe2S6) as efficient material for nonlinear optical application

Abstract

Article reports design and synthesis, technology, crystal structure determination and results of photoinduced nonlinear optical investigations of novel TlInGe2S6 crystals. We have discovered TlInGe2S6 as a new type of laser induced nonlinear optical materials. Following the performed measurements we can use the titled crystals for laser operated coherent wavelength transformations. It was shown, that thin, photoinduced nanolayers formed by laser energies above the energy gap as well a near the phonon resonances possess promising nonlinear optical properties. Different types of cw lasers with the same powers of the photoinduced beams were used: SHG of the Nd:YAG laser (532 nm), fundamental Nd:YAG laser (1064 nm), and IR CO2 laser with wavelength of 9400 nm.The crystal structure of novel quaternary thallium indium germanium sulphide TlInGe2S6 determined by X-ray powder method possesses trigonal space group R3. The as-derived TlInGe2S6 crystalline alloy was probed employing the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. Particularly, for the TlInGe2S6 alloy surface, both pristine and 3.0 keV Ar+ ion-irradiated, we have monitored the XPS valence-band and core-level spectra. These measurements indicate that the TlInGe2S6 surface is rather stable with respect to Ar+ ion-irradiation, which does not induce significantly near the surface layers sub-stoichiometry. Matching on a common energy scale of the XPS valence-band spectrum and the XES S Kβ1,3 and Ge Kβ2 bands indicates that main contributions of the S 3p and Ge 4p states are located in the upper and central portions of the valence band of TlInGe2S6, respectively, with significant contributions of these states in other valence-band parts as well.