体全息波分复用器件波长选择性实验

Experiment of Wavelength Selectivity of Volume Holographic Wavelength Division Multiplexing Filter

为了研究体全息光栅波分复用器件的波长选择性,采用532 nm绿光透射式记录的方法在一块双掺铟铁立方型铌酸锂晶体中先后记录了具有不同光栅尺寸比的有限尺寸体全息光栅,用光通信波段红外可调谐激光器对这些光栅分别进行了正交式读出。光栅尺寸比为4:3.4:2和5:2时得到的波长选择性曲线的3 dB带宽分别为0.48 nm,0.45 nm和0.43 nm,对应的布拉格中心波长均与理论预测值吻合得很好。表明在用通信波长对体全息光栅进行读出时,随着光栅尺寸比的增大,波长选择性曲线的3 dB带宽会减小。通过选择合适的光栅尺寸比可以明显改进体全息光栅波分复用器件的波长选择性,从而达到密集波分复用的需求。

In order to investigate the wavelength selectivity of volume holographic gratings, applied as wavelength division multiplexing （WDM） filter, a 532 nm laser was used to record volume holographic gratings with finite size in doubly doped cubic lithium niobate crystal. Gratings of different size ratio were recorded in transmission configuration one by one and read in orthogonal scheme with a tunable infrared laser working in the optical communication band. The 3 dB bandwidth of wavelength selectivity curves corresponding to the grating size ratio of 4 ： 3, 4 ： 2 and 5 ： 2 were 0.48 nm, 0.45 nm and 0.43 nm respectively. The Bragg central wavelength of each grating is almost the same as theoretical prediction. This indicated that with larger gratings size ratio one can obtain narrower 3 dB bandwidth in the readout of volume holographic gratings. The wavelength selectivity of volume holographic WDM filter can be obviously improved by choosing a suitable grating size ratio and it is possible to meet the requirement of dense WDM.