Temperature-Insensitive Second-Harmonic Generation at 0.5321 µm in YCa4O(BO3)3

YCa4O(BO3)3 has been found to have the phase-matching points where the temperature variation of the phase-matching angle (dθobs/dT) becomes zero for type-1 second-harmonic generation at 0.5321 µm at θ=30.8° and =180°. We also found that the temperature sensitivity of the phase-matching angle in the zx plane differs between the =0° and =180° propagation directions in this material. In addition, the thermo-optic dispersion formula of YCa4O(BO3)3 is presented.