Accurate Characterization of Free Carrier Refraction in InP

Using recently published results of intrinsic and free carrier nonlinear absorption coefficients in InP, nonlinear refraction was investigated at 1.064 μm using ns duration lasers to characterize refraction from generated free carriers. A phase retrieval algorithm was implemented to determine the amplitude and phase profiles of the incident beam. Accurate spatial and temporal profiles of the incident field were used to model nonlinear propagation through and beyond the sample. With the sample held fixed at focus and the incident energy increased, images of the transmitted beam a fixed distance away were recorded as a function of irradiance. Excellent agreement was observed between recorded beam images and those generated from the numerical model.