The intensity-dependent nonlinear absorption and refraction characteristics of crystalline InSb thin films are investigated by z-scan method at 405 nm laser wavelength. Results show that the nonlinear absorption coefficient of crystalline InSb thin films is in the order of ~ + 10−2 m W−1, and the nonlinear refractive index is in the order of ~ + 10−9 m2 W−1. Variable-temperature ellipsometric spectroscopy measurements and electronic process analyses as well as theoretical calculations are employed to discuss the internal mechanisms responsible for the giant optical nonlinearity. Analysis results indicate that the nonlinear absorption mainly stems from the laser-induced free-carrier absorption effect, whereas the nonlinear refraction is mainly from thermal effect due to band gap shrinking and carrier effect due to the transition process of electrons, respectively. These characteristics may be responsible for the super-resolution effect in nano-optical information storage.
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