Measurement of polarization dependence of two-photon absorption co-efficient β in InP using extended Z-scan technique for thick materials

Two-photon absorption coefficient β in InP has been measured in the wavelength range of 1640 to 1800 nm by means of the Z-scan technique in relatively thick films. The values of β for the polarization direction parallel to [110] are evaluated to be 22.33 ± 0.05, 15.40 ± 0.07 and 4.34 ± 0.07 cm/GW at wavelengths of 1640, 1700 and 1800 nm, respectively, from the fitting to the equation including the spatial and temporal profiles of the focused Gaussian beam. The polarization dependence of β has been also measured. The dependence has been able to be expressed very well by the expression of β with the imaginary part of the third-order nonlinear susceptibility tensor χ
⁽³⁾
. These results also indicate that our derived equation of the transmittance is appropriate for the analysis of the two-photon absorption in the thick materials.