Intensity evolution characteristics of square super-Gaussian beam in Kerr medium
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摘要: 基于非线性薛定谔方程，采用分步傅里叶算法模拟了方形超高斯光束在Kerr介质中的传输情况，重点分析了方形超高斯光束轴向中心强度与对角方向强度的演化特性，同时还分析了其在Kerr介质中的自聚焦特性、峰值光强变化情况以及B积分变化情况。研究结果表明：方形超高斯光束通过Kerr介质后，距光束中心不同距离处有不同程度的强度增强和凹陷，光束中心附近的强度增强和凹陷较弱，光束边缘以及四角处的强度增强和凹陷较强，且对角方向上的强度增强和凹陷程度要强于轴向中心方向；减小阶数可以减缓光束的边缘强度增强，并可以减缓B积分的增长；减少Kerr介质厚度可以降低光束边缘强度增强程度，并可以减小B积分的大小。提出了光束边缘强度起伏的主要原因可能是光束的相干叠加。Abstract: Based on the nonlinear Schrödinger equation, the step FFT is used to simulate the propagation of the square super-Gaussian beam in Kerr medium, and the evolution characteristics of the axial center and diagonal intensity of the square super-Gaussian beam are analyzed. At the same time, the self-focusing characteristics, the variation of peak intensity and B-integral in Kerr medium are also analyzed. The research results show that after the square super-Gaussian beam passes through the Kerr medium, there are different degrees of intensity enhancement and depression at different distances from the center of the beam, the intensity enhancement and depression are weak near the beam center, strong at the edge and four corners of the beam, and they are stronger in the diagonal direction than in the axial center direction. Reducing the order can slow down the edge intensity enhancement of the beam and the growth of the B-integral. Reducing the thickness of the Kerr medium can reduce the intensity enhancement of the beam edge and the size of the B-integral. It is proposed that the main reason for the fluctuation of the edge intensity of the beam probably be the coherent superposition of the beam.
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Key words:
- nonlinear optics /
- super-Gaussian beam /
- Kerr medium /
- self-focusing /
- B-integral
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图 1 方形超高斯光束在Kerr介质的前表面和后表面的归一化光场分布
Figure 1. Normalized field distribution of square super-Gaussian beams on the front and back surfaces of Kerr medium
图 2 方形超高斯光束轴向中心强度演化过程与对角强度演化过程
Figure 2. Axial center intensity evolution process and diagonal intensity evolution process of a square super-Gaussian beam
图 3 方形超高斯光束在Kerr介质后表面的轴向中心强度与对角强度对比图
Figure 3. Comparison of axial central intensity and diagonal intensity of square super-Gaussian beam on the back surface of Kerr medium
图 4 方形超高斯光束在Kerr介质中的B积分变化情况
Figure 4. B-integral variation of square super-Gaussian beams in Kerr medium
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