Polarization Dependences of Two-Photon Absorption in Si and GaAs Photodiodes at a Wavelength of 1.55 µm

Photocurrents induced by two-photon absorption (TPA) at a wavelength of 1.55 µm in GaAs and Si photodiodes (PDs) were measured and compared. The photocurrent generated by a GaAs PD depends strongly on the linear polarization direction, which is consistent with the anisotropic nature of TPA in GaAs. In contrast, the photocurrent of a Si PD has a negligible dependence on the polarization direction, indicating that TPA is isotropic in this PD at a wavelength of 1.55 µm. The photocurrents generated by GaAs and Si PDs by elliptically polarized light are consistent with analysis based on the third-order nonlinear susceptibility tensor.