Ding, Tingting; Tang, Yongzhi; Li, Hao; Liu, Shijie; Zhang, Jing; Zheng, Yuanlin; Chen, Xianfeng Source: Optics Letters, v 49, n 5, p 1121-1124, March 1, 2024;

Lithium niobate on insulator (LNOI) holds great potential for frequency conversion, where a variety of highperformance nonlinear devices based on different structures has been demonstrated. Here, we report on second harmonic generation (SHG) in MgO-doped LNOI ridge microwaveguides for efficient green light emission, via an exact type-I noncritical birefringence phase matching (BPM). The LNOI micro-waveguide has a cross section of ~ 3 × 4 μm2, featuring low coupling loss with lens fiber. The normalized conversion efficiency from a continuous-wave (cw) pump to its second harmonic is measured to be37%/Wcm2 in a singlepass configuration. The device shows both relatively high efficiency and a void of periodic poling, offering a potential solution for efficient and scalable green light sources and frequency converters.

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