Characterizations of the Nonlinear Optical Properties for (010) and (-201) Beta-phase Gallium Oxide

TL;DR

This study characterizes the nonlinear optical properties of beta-phase gallium oxide, revealing low two-photon absorption and Kerr refractive index, with anisotropic behavior, indicating potential for UV-visible integrated photonics.

Contribution

First comprehensive characterization of nonlinear optical properties of (010) and (-201) beta-Ga2O3, including TPA coefficient and Kerr index, with polarization dependence analysis.

Findings

Beta-Ga2O3 exhibits low TPA coefficients compared to GaN.

Significant nonlinear optical anisotropy observed on the (-201) plane.

Potential for use in UV-visible integrated photonic devices.

Abstract

We report, for the first time, the characterizations on optical nonlinearities of beta-phase gallium oxide (\b{eta}-Ga2O3), where both (010) \b{eta}-Ga2O3 and (-201) \b{eta}-Ga2O3 were examined for two-photon absorption (TPA) coefficient, Kerr refractive index, and their polarization dependence. The wavelength dependence of the TPA coefficient and Kerr refractive index was estimated using a widely used analytical model. \b{eta}-Ga2O3 exhibits a TPA coefficient of 1.2 cm/GW for (010) \b{eta}-Ga2O3 and 0.58 cm/GW for (-201) \b{eta}-Ga2O3. The Kerr refractive index is -2.14*10^(15) cm2/W for (010) \b{eta}-Ga2O3 and -2.89*10^(15) cm2/W for (-201) \b{eta}-Ga2O3. In addition, \b{eta}-Ga2O3 shows stronger nonlinear optical anisotropy on the (-201) plane than on the (010) plane, possibly due to highly asymmetric crystal structure. Compared with that of gallium nitride (GaN), the TPA coefficient of \b{eta}-Ga2O3 is 20 times smaller, and the Kerr refractive index of \b{eta}-Ga2O3 is also found to be 4 to 5 times smaller. These results indicate that \b{eta}-Ga2O3 has the potential for use in ultra-low loss waveguides and ultra-stable resonators and integrated photonics, especially in the UV and visible wavelength spectral range.