Temperature-insensitive second-harmonic generation based on noncollinear phase matching in a lithium triborate crystal

In high-average-power second-harmonic generation (SHG) devices, the unavoidable thermal distortion induces a nonuniform phase mismatch that poses an inherent limitation on the conversion efficiency. Here we introduce a temperature-insensitive noncollinear (TIN) phase-matching scheme, which can significantly improve the performance of high-power SHG devices and is versatile to a broad range of laser wavelengths. In the proof-of-principle experiment with a lithium triborate crystal and a 1053 nm nanosecond laser, we demonstrate a large temperature bandwidth of ∼50 K×cm1/2 and a high SHG efficiency of ∼56%. This temperature bandwidth is 13 times that of the conventional collinear phase matching. We also numerically investigate the performance of the proposed TIN phase-matching scheme in high-power lasers. The demonstrated large temperature bandwidth allows efficient SHG in the high-power regime of 5–10 kW. The simplicity, high efficiency, and wavelength versatility will make the TIN phase matching attractive for wide applications in high-power lasers.