Highly asymmetric optical properties of b-Ga2O3 are investigated by polarization-dependent photoluminescence (PL) excitation spectroscopy for assessing its potential use for a novel ultraviolet emitter and nonlinear optical material. Based on power-dependent excitation and two-photon depth scan, it is demonstrated that the underlying mechanism for the PL occurring far below the bandgap is not caused by intrinsic polaron effects, but by excitonic recombination at extrinsic defect sites.
Highly asymmetric optical properties of \b{eta}-Ga2O3 as probed by linear and nonlinear optical excitation spectroscopy