Nonlinear optical properties of ZnS with different laser pulse Chang Qing, Li Yalei

Based on Z-scan technique, the nonlinear absorption and nonlinear refraction characteristics of ZnS crystal were researched in the case of wavelength of 532 nm picosecond laser pulses and wavelength of 800 nm femtosecond laser pulses. Experimental results are as follows. The absorption of ZnS crystal is two-photon absorption and the nonlinear absorption coefficient is 5.310-11 m/W in the case of wavelength of 532 nm picosecond laser pulses. The absorption of ZnS crystal is three-photon absorption and the nonlinear absorption coefficient is 0.5910-21 m2/W2 in the case of wavelength of 800 nm femtosecond laser pulses. Under the effect of 532 nm picosecond laser pulses, the nonlinear refractive index sign of ZnS crystal is negative and the change of nonlinear index of refraction generated by free carrier is the dominant factor. But under the effect of 800 nm femtosecond laser pulses, the nonlinear refractive index sign of ZnS crystal is positive and dominant factor is the change of nonlinear index of refraction generated by bound electron.