First-principles calculations of the frequency-dependent birefringence, second-harmonic generation, and linear electro-optic response are reported for LiGaO<sub>2</sub> (which is transparent to as small as 222 nm). Good agreement is obtained with available experimental data in the visible region of the spectrum. The calculated frequency-dependent nonlinear optical responses are surprisingly constant in the entire energy region below the gap and small in absolute value (of the order of 0.2–1.2 pm/V for the various structures considered). Although the birefringence is insufficient for second-harmonic generation into the ultraviolet, opportunities may exist for sum-frequency generation. Angular phase-matching tuning curves are provided. The reasons for the low values of χ<sup>(2)</sup> are discussed. It is found to be not very sensitive to the structure and to arise in part from a large degree of cancellation between pure interband and mixed intra- and interband contributions.
© 1999 Optical Society of America
(190.2620) Nonlinear optics : Harmonic generation and mixing
(190.4400) Nonlinear optics : Nonlinear optics, materials
(190.4720) Nonlinear optics : Optical nonlinearities of condensed matter
Sergey N. Rashkeev, Sukit Limpijumnong, and Walter R. L. Lambrecht, "Theoretical evaluation of LiGaO2 for frequency upconversion to ultraviolet," J. Opt. Soc. Am. B 16, 2217-2222 (1999)