Three-photon absorption and Kerr nonlinearity in undoped bulk GaP excited by a femtosecond laser at 1040 nm

A modified Z-scan method was used to achieve polarization-resolved measurement of nonlinear properties of undoped bulk GaP excited by a femtosecond laser at 1040 nm. The optical Kerr nonlinearities of < 100 >-, < 110 >- and < 111 >-cut GaP slabs were characterized experimentally at room temperature. The open aperture Z-scan curves demonstrate that three-photon absorption in GaP dominates the nonlinear absorption processes under the experimental conditions. In addition, experimental results show that both three-photon absorption and Kerr nonlinearity of undoped GaP possess the same anisotropy and crystal orientation dependence.