Fang Xinyuan, Yang Guang, Wei Dunzhao, Wei Dan, Ni Rui, Ji Wei, Zhang Yong, Hu Xiaopeng, Hu Wei, Lu Y Q, Zhu S N, Xiao Min
Opt Lett. 2016 Mar 15;41(6):1169-72. doi: 10.1364/OL.41.001169.
We experimentally demonstrate the orbital angular momentum (OAM) conversion by the coupled nonlinear optical processes in a quasi-periodically poled LiTaO3 crystal. In such a crystal, third-harmonic generation (THG) is realized by the coupled second-harmonic generation (SHG) and sum-frequency generation (SFG) processes, i.e., SHG is dependent on SFG and vice versa. The OAMs of the interacting waves are proved to be conserved in such coupled nonlinear optical processes. As we increase the input OAM in the experiment, the conversion efficiency decreases because of the reduced fundamental power density. Our results provide better understanding for the OAM conversions, which can be used to efficiently produce an optical OAM state at a short wavelength.
我们通过准周期极化钽酸锂晶体中的耦合非线性光学过程，实验证明了轨道角动量（OAM）转换。在这种晶体中，三次谐波产生（THG）是通过耦合的二次谐波产生（SHG）和和频产生（SFG）过程实现的，即SHG依赖于SFG，反之亦然。在这种耦合非线性光学过程中，相互作用波的OAM被证明是守恒的。在实验中，当我们增加输入OAM时，由于基波功率密度降低，转换效率会下降。我们的结果为OAM转换提供了更好的理解，可用于在短波长下高效产生光学OAM态。
