Noise Properties of Wavelength-Converted Light Generated in Periodically-Poled Lithium Niobate Waveguide

●研究了利用准相位匹配非线性波导和周期极化锂离子晶体（PPLN）实现的光学和频（SFG）。将2.1mW的1.55 μm探测光与36 mW的0.976 μ m泵浦光混合，获得了2 mW的0.6 μm和频光功率。2，600%/W的频率转换效率非常高，这与理论计算结果吻合得很好。●还研究了使用PPLN波导的二次谐波产生（SHG）。在1.064 μm泵浦光为66.7mW时，获得了24.6mW的0.532 μm倍频光，总转换效率为37%。倍频光功率随泵浦功率的平方线性增加。这些特性对于单模泵浦光和多模泵浦光几乎是相同的。●为了精确测量噪声，必须使用单模激光而不是多模激光作为二次谐波的泵浦光源。利用Si-APD单探测器技术测量了倍频光的噪声特性。SHG光被揭示为散粒噪声限制的，没有任何多余的噪声。●为了证明SHG中的噪声抑制机制，重要的是实现更有效的SHG并提高SHG光的检测效率。

● I investigated optical sum frequency generation (SFG) using quasi-phase-matched (QPM) nonlinear waveguide by means of periodically poled lithium niobathe (PPLN). Sum frequency light power of 2 mW at 0.6 μm wavelength was successfully demonstrated by mixing the 2.1 mW probe light at 1.55 μm and the 36 mW pump light at 0.976 μm. This frequency conversion efficiency of 2,600%/W is extremely high, which is well duplicated by the theoretical calculations.● Second harmonic generation (SHG) was also investigated using PPLN waveguide. The SHG light power of 24.6 mW at 0.532 μm wavelength was successfully demonstrated from 66.7 mW pump light at 1.064 μm wavelength, which corresponds to the total conversion efficiency of 37%. The SHG light power linearly increases with the square of the pump power. These characteristics are almost the same both for the single-mode pump light and the multi-mode pump light.● For the precise noise measurement, it is essential to use the single-mode laser light instead of the multi-mode one for the pump light source in the SHG. The noise characteristic of the SHG light was measured by the single detector technique using the Si-APD. The SHG light is revealed to be the shot-noise-limited without any excess noise.● In order to demonstrate the noise suppression mechanism in the SHG, it is important to achieve the more efficient SHG and to improve the detection efficiency of the SHG light.