Second-order optical nonlinearity of GeS₂-Ga₂S₃-PbI₂ chalcohalide glass under electrical poling

Utilizing Maker fringe method, second-harmonic generation (SHG) was observed from electrically poled chalcohalide glass in a GeS₂-Ga₂S₃-PbI₂ pseudo-ternary system for the first time. The 70GeS₂·15Ga₂S₃·15PbI₂ composition glass was poled by applying various high dc voltages at various temperatures for different poling durations. SHG was observable from 190℃ under 4.0 kV, and the second harmonic (SH) intensity increased with the enhancement of applied voltage and poling duration until reached saturation. When conducted under 6 kV for 40 min, with increasing poling temperature the SH intensity gradually increased, experienced a maximum, and then decreased. A maximum second-order nonlinearity susceptibility, χ⁽²⁾, value of 4 pm·V^-1 was obtained under the optimal poling condition of an applied voltage of 6 kV, a temperature of 250℃ and a poling duration of 40 min. The SHG phenomenon is considered to be the result of the breakage of glassy macroscopic isotropy originated from reorientation of dipoles during electrical poling treatment and the dependence of poling parameters on the SH intensity is also discussed.