Characterizations of the nonlinear optical properties for (010) and (2¯01) beta-phase gallium oxide

Abstract

We report, for the first time, the characterizations on optical nonlinearities of beta-phase gallium oxide (β-GaO), where both (010) β-GaO and (2¯01) β-GaO were examined for two-photon absorption coefficient, Kerr nonlinear refractive index, and their polarization dependence. The wavelength dependence of two-photo absorption coefficient and Kerr nonlinear refractive index were also estimated by a widely used analytical model. β-GaO exhibits a two photon absorption (TPA) coefficient of 1.2 cm/GW for (010) β-GaO and 0.6 cm/GW for (2¯01) β-GaO. The Kerr nonlinear refractive index is -2.1 × 10 cm/W for (010) β-GaO and -2.9 × 10 cm/W for (2¯01) β-GaO. In addition, β-GaO shows stronger in-plane nonlinear optical anisotropy on (2¯01) plane than on (010) plane. Compared with GaN, TPA coefficient of β-GaO is 20 times smaller, and the Kerr nonlinear refractive index of β-GaO is also found to be 4-5 times smaller. These results indicate that β-GaO have the potential for ultra-low loss waveguides and ultra-stable resonators and integrated photonics, especially in UV and visible wavelength spectral range.

Nonlinear nanophotonic devices in the ultraviolet to visible wavelength range

“…The Kerr refractive indexes (n 2 ) of GaN were identified to be n 2 = 1.15-1.4 × 10 −14 cm 2 W −1 at λ = 800 nm [127]. However, because the growth of GaN is usually accompanied with large amount of threading dislocations, the two-photon absorption coefficient of GaN is relatively large in comparison with other wide bandgap semiconductors [128].…”

“…Preliminary efforts have been paid towards the fundamental optical properties as well as device performance of β-Ga 2 O 3 . H. Chen et al characterized the optical nonlinearity of β-Ga 2 O 3 , where a TPA coefficient of 0.6-3.2 cm/GW, and an n 2 in the range of −2.1 × 10 −15 cm 2 W −1 to −2.9 × 10 −15 cm 2 W −1 were obtained at 404 nm [128]. It's noteworthy that bulk crystalline β-Ga 2 O 3 was obtained using the floating zone growth method [241], which leads to much superior crystal quality with less defect density on β-Ga 2 O 3 compared to GaN bulk crystals.…”

“…(a) The schematic of β-Ga 2 O 3 crystal structures showing (010) and (2 01) crystal planes[128]. (b) The estimated wavelength dependence of TPA coefficient for (010) and (2 01) β-Ga 2 O 3 samples.…”

“…"E⊥" indicates that the electrical field intensity is perpendicular to[102] direction, while "E " indicates that field intensity is parallel to[102] direction. Reprinted with permission from[128]. Copyright 2018 by the Optical Society of America.…”

Thermal lensing‐induced soliton molecules in β‐phase gallium oxide

“…Optical properties of have been characterized in several recent experiments 3,13–18 and it is known that this material is a transparent semiconducting oxide. Experimental measurements of two‐photon absorption coefficient and Kerr nonlinear coefficient, as well as their polarization dependence along (010), have been carried out 14 and the wavelength dependence of two‐photon absorption coefficient together with the Kerr nonlinear refractive index were estimated 14 . Results suggest that exhibits a two‐photon absorption coefficient of 1.2 cm/GW, and a Kerr nonlinear refractive index of along (010).…”