基于体全息光栅的谱合成器件优化设计研究

Optimization Design Research on Spectrum Synthesis Device Based on Volume Holographic Bragg Gratings

为了在有限带宽内增加参与谱合成的光束数目,研究了光栅结构参数对光栅波长选择特性和串扰的影响,给出了相应的优化设计方法。研究结果表明,相比于透射式体全息光栅,反射式体全息光栅的波长选择性曲线主瓣具有接近方波的形态,更适合作为合束器件。为抑制串扰,设计体光栅时应该增加光栅厚度,减小折射率调制度和光栅周期,并选用较小折射率的光栅介质。切趾技术可以进一步抑制串扰,但会增加波长选择宽度,实际中兼顾制作工艺的难度,选用线性切趾体全息光栅是较为理想的方案。

To increase the number of light beams which contribute to the spectrum synthesis light beam, the ef-fect of grating structures on the wavelength selectivity and crosstalk are researched, and corresponding optimizationmethods are proposed. Research results show that compared to transmission type, reflective volume holographicgrating＇s wavelength selectivity curve is closer to the square wave form and more suitable for beam synthesis devic-es. To restrain crosstalk, the gratings with larger thickness must be designed, smaller refractive index modulationand grating period, as well as the grating medium must be used with smaller refractive index. Furthermore, apodiza-tion technology can restrain crosstalk more but increase wavelength selective width, so considering of fabricating dif-ficulties in practice, the linear-apodized volume holographic gratings are better scheme.