Effect of Swift Heavy Ions Irradiation on Third Order Nonlinear Optical Properties of As₂S₃ Chalcogenide Films

Third order nonlinear optical response and optical switching in Ge irradiated As₂S₃ thin film at room temperature [As₂S₃/Ge(RT)], Ge and Ni irradiated As₂S₃ thin films at liquid nitrogen temperature [As₂S₃/Ge(RT)], [As₂S₃/Ni(LNT)] have been observed using single beam z-scan technique at second harmonic of Nd: YAG laser (532nm). Nonlinear refractive index (n₂), nonlinear absorption coefficient (β) and third order nonlinear susceptibility (χ³) of As₂S₃/Ge(RT), As₂S₃/Ge(LNT) and As₂S₃/Ni(LNT) thin films have been estimated. Self defocusing (n<0) in As₂S₃/Ge(LNT), self focusing (n>0) in As₂S₃/Ge(RT) and As₂S₃/Ni(LNT) have been observed. The results have been interpreted in terms of electrostriction effect and variation in band gap with heavy ion effect. Further optical switching behavior has been As₂S₃essed as a function of input intensity. Higher nonlinearity has been observed in As₂S₃/Ge(LNT) and it has been found that the swift heavy ion irradiated films are much more promising materials for nonlinear optics, functional optical fibers and ultrafast optical switching.