Cadmium telluride bulk crystal as an ultrafast nonlinear optical switch

A semiconductor bulk crystal has several advantages as a nonlinear optical material, such as low processing cost, long interaction length, and alleviation of the free-carrier absorption caused by two-photon absorption (TPA). We examine optical properties of semiconductor bulk crystals with different orientations at 1.55 μ m and find that CdTe[111] has favorable capabilities, such as nonlinear refractive index of 5.23 × 10 − 17 ( m 2 W ) , TPA coefficient of 18.3 ( mm GW ) , and consequent figure of merit of 0.54. Optical three-dimensional measurements of reflective material are carried out using CdTe[111] as ultrafast optical Kerr shutter and clear images corresponding to surface steps are obtained.