Electric field induced second harmonic generation in arsenic sulfide deposited by thermal evaporation

Electric field induced second harmonic (EFISH) measurements are performed on thin films of arsenic sulfide deposited on chromium coated fused silica substrates by thermal evaporation of amorphous As₂S₃ bulk material. EFISH allows to widely tune the second-order optical susceptibility (χ⁽²⁾). An observed shift of the minimum of the second harmonic generation (SHG) intensity away from 0 V reveals a non-EFISH bulk χ⁽²⁾, which is unexpected for amorphous materials. Additional SHG measurements on as-deposited films for investigation of the non-EFISH bulk χ⁽²⁾ show Maker fringe patterns. Analyzing them and calibrating the SHG response against beta barium borate (BBO) crystal allows us to extract the components of the χ⁽²⁾ tensor. The main component of this non-EFISH bulk χ⁽²⁾ has a value of ∼0.22 pm/V. By increasing the χ⁽²⁾ by applying the dc electric field a maximum value of 3.8 pm/V was achieved in EFISH measurements. This value is comparable to the χ⁽²⁾ of traditional nonlinear crystals, e.g., BBO, which makes arsenic sulfide an interesting candidate for nonlinear hybrid structures.