光折变全息光栅扭曲对波分复用应用的影响

Influence of the Tilting of the Photorefractive Hologram Grating on Wavelength Demultiplexer

介绍了光折变全息生成的布拉格光栅由于扭曲而对波分复用应用的影响,提供了一种在器件制作前预先了解光栅扭曲对器件性能影响大小的方法。使用傅里叶分析的方法,对布拉格光栅扭曲引起的相位改变做了修正计算。对修正了相位的光栅,采用严格耦合波分析,计算了光折变全息应用于波分复用的频谱响应。并用该方法计算了不同程度的光栅扭曲造成的频谱响应变化,证明光栅扭曲会直接造成器件衍射效率下降,旁瓣增大,从而使串扰增大,是光折变全息应用于波分复用必须考虑的重要因素之一。对光折变相位光栅衍射图像数据采集的过程作了介绍,并在此基础上将记录了光栅的晶体进行波分复用损耗和串扰特性的测试,实验结果证明提供的方法能够有效预知光折变全息光栅扭曲对器件综合性能的影响。

The influence of the tilting of the photorefractive hologram grating on wavelength demultiplexer is studied. An effective method, which can predict the influence of the grating tiling on the demultiplexing performance, is presented in order to avoid the unnecessary experimental spending. The phase error caused by the tilting of the Bragg grating is corrected with a Fourier analysis. The spectral response of the demultiplexer is calculated by using a rigorous coupled wave analysis method. The influence of the tilting of the Bragg grating on the spectral response is analyzed. It is shown that the phase difference due to the tilting of the grating can result in a large insertion loss and a large crosstalk. It is pointed out that the hologram tilting must be avoided as much as possible since it deteriorates the final performance seriously when a photorefractive hologram Bragg grating is used for wavelength demultiplexing. The experimental method of the grating image processing is also introduced in the paper. The experimental results accorded with theoretical computation commendably by testing the spectral responses of two demultiplexers with the tilting gratings.