通过分析螺旋相位调制型携带轨道角动量 (OAM)光场的传播演化特性,提出一种以该光场演化波源为对象进行非线性效应研究的新途径。基于三波耦合模型和柯林斯路径积分理论,得到以OAM演化波源为基频光的二次谐波光场及衍射传播解析表达式。采用飞秒钛宝石激光器,基于4f相干成像系统,将OAM演化波源成像于倍频晶体处,实验研究了该波源产生的二次谐波的传播特性,测量了不同阶数OAM波源的倍频输出功率,并与演化后的OAM模式倍频结果进行了比较。研究表明,以演化波源附近为非线性作用区有望解决高维OAM模式光斑过大,以及光场交叠性不好导致的非线性效率低等问题,这也为高维OAM光场实现高效率非线性调控提供了重要依据。

By analyzing the propagation and evolution characteristics of a spiral phase modulated orbital angular momentum (OAM) light field, we propose a new approach to investigate the nonlinear effects of the evolutionary wave source of the optical field. Based on the three-wave coupling model and the Collins path integral theory, we obtain the analytical expressions of the frequency-doubled light and its diffraction propagation solutions of the OAM evolutionary wave source. We experimentally study the propagation property of the second harmonic wave by imaging the OAM evolutionary wave source in the frequency-doubling crystal based on a femtosecond Ti: Al2O3 laser and the 4f coherent system. The frequency-doubling output powers of OAM wave sources with different orders are measured and compared with those of OAM modes after evolution. The research results show that using the starting point of evolution as the nonlinear interaction area can solve the problems such as the low nonlinear interaction efficiency caused by light overlapping and the overlarge spot of a high-dimensional OAM beam. Simultaneously, it provides an important basis for the high-efficiency nonlinear manipulation and control of a high-dimensional OAM light field.