Sinc切趾反射体布拉格光栅衍射特性分析

Diffraction Characteristic Analysis of Sinc-Apodized Reflective Volume Bragg Grating

基于sinc切趾反射体布拉格光栅的谱合成技术是获得高功率谱合成输出的有效方法。考虑到入射单色平面波光束的偏振状态,采用传输矩阵法,分析了光栅参数对衍射效率、波长选择性和角度选择性的影响。计算结果表明,入射角度对不同偏振状态入射光束的衍射效率影响较大。sinc切趾反射体布拉格光栅的衍射效率近似由光栅厚度和折射率调制幅值的乘积决定,当折射率调制幅值与光栅厚度的乘积大于1.7028×10-6时,不同偏振态在小角度入射时的衍射效率高于99%。sinc切趾反射体布拉格光栅的波长选择性带宽和角度选择性带宽随折射率调制幅值的增加而增大,随衍射效率的增加而减小。通过优化光栅参数,利用sinc切趾体布拉格光栅可实现光谱间距低于200 pm的多光束谱合成。

It is an effective approach to obtain high power laser output by spectral beam combining technology based on the sinc-apodized reflective volume Bragg grating. Considering the polarization of the monochromatic plane wave incident beam, the effects of the grating parameters on the diffraction efficiency, spectral selectivity and angular selectivity of the grating are analyzed by using the chain matrix method. The results show that the incident angle affects the diffraction efficiency greatly when the incident beams have different polarizations. The diffraction efficiency of the sinc-apodized reflective volume Bragg grating increases with the increase of the grating thickness and/or refractive index modulation, and it can be achieved higher than 99% with different polarizations at small incident angle when the product of the grating thickness and refractive index modulation is larger than 1. 7028 × 10 6. The spectral selectivity and angular selectivity of the sinc-apodized reflective volume Bragg grating increase with the increase of the refractive index modulation, but decrease with the increase of the diffraction efficiency. By optimizing the grating parameters of the sinc-apodized reflective volume Bragg grating, the channel spectral separation lower than 200 pm can be achieved.