Nonlinear Optical Properties of Lithium Gallium Oxide

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Abstract
The crystal symmetry (point group mm2) and refractive indices of LiGaO2 show that it can be phase matched for second‐harmonic generation (SHG) of laser fundamentals in the near infrared. Furthermore, these data suggest that LiGaO2 might be a useful nonlinear medium for a 1.06‐μ pumped near‐infrared optical parametric oscillator in which the pump, signal, and idler waves all travel along a principal index direction. The magnitudes and relative signs of the nonlinear optical coefficients that determine SHG and optical parametric interactions in LiGaO2 have been measured using a 1.06‐μ fundamental. It is found that these coefficients relative to d36 for KH2PO4 are: d33=±1.45±0.15, d31=±0.17±0.02, and d32=∓0.37±0.04. The small magnitudes of these coefficients would seem to preclude the use of LiGaO2 in efficient nonlinear optical devices. A discussion of a simple experimental method for the determination of the relative signs of the nonlinear optical coefficients of a given crystal is also included.