Nonlinear Absorption at Optical Telecommunication Wavelengths of InN Films Deposited by RF Sputtering

We report on the nonlinear optical absorption of InN films deposited on GaN templates by radio-frequency (RF) sputtering. The layers are characterized through the pump-probe technique at 1.55 μm, by obtaining a nonlinear absorption coefficient of 167±30 cm/GW with a nonlinear response recovery time of 380 fs. This nonlinear behavior is attributed to a two-photon absorption process followed by a free carrier absorption by the photogenerated carriers. These results render InN films deposited by RF sputtering particularly suitable for ultrafast all-optical devices based on low-cost technology.