光栅光谱衍射效率测量新技术的误差分析与校正方法研究

Error Analysis of the New Measurement Technique for Obtaining the Spectral Diffraction Efficiencies of a Grating

衍射光栅是非常重要的色散元件,在光谱分析领域中有着广泛的应用,光栅光谱衍射效率的测量对于评估光栅性能和改进光栅制备工艺有着重要的作用。在目前常见光栅光谱衍射效率的测量技术中,由于存在两种需要重复数百次的机械运动,因而光栅光谱衍射效率的测量速度比较缓慢,如获取700~900 nm波段范围内的光谱衍射效率,大约需要5~8 min的时间。在之前的研究中,报道了一种快速测量光栅光谱衍射效率的新方法,新方法采用声光可调谐滤波器、积分球探测器和高速数据采集系统,可以完全消除现有测量方法中存在的两种耗时的机械运动,由于测量过程中没有任何机械运动的参与,新方法能在10 ms量级获得700~900 nm波段范围内的光谱衍射效率。首先对光栅光谱衍射效率测量新方法的主要误差来源进行了系统分析,发现新方法一个比较明显的误差来源是凸透镜的透过率与入射角相关;然后结合光学模拟,得到了激光光束以不同入射角度传播通过凸透镜时的透过率,并提出了相应的误差校正方法;最后结合实验测量数据,我们对光栅光谱衍射效率新测量技术的误差校正方法进行了实验验证。数据分析结果表明,在550~750 nm波段范围内测得的光栅光谱衍射效率,经过误差校正后,新方法与传统测量方法之间绝对误差的平均值从校正前的0.207%降低到校正后的0.099%,由于传统光栅光谱衍射效率测量方法的测量精度约为0.1%,结果表明,提出的误差校准方法能成功消除光栅光谱衍射效率新测量方法的主要误差来源。

Diffraction grating is a very important dispersive element,and it has been commonly used in the field of spectral analysis,the measurement of a diffraction grating’s spectral diffraction efficiencies is essential for evaluating its performance in practical applications and improving its manufacturing technique.In the currently popular measurement technique for obtaining the spectral diffractionefficiencies of a plane grating,because of the hundreds of repetitions of two kinds of time-consuming mechanical movements during the measuring process,the major drawback of this technique is the slow measuring speed,for example,approximately 5-8 minutes are needed to obtain the spectral diffraction efficiencies of a broad band pulse compression gratings from 700 to 900 nm(in sampling steps of 1 nm).In our earlier research,we presented a motionless and fast measurement technique for obtaining the spectral diffraction efficiencies of a plane grating,and the new method was based on the employment of an acousto-optical tunable filter,an integrating sphere and a fast data acquisition system,the new methodcan measure the plane grating’s spectral diffraction efficiencies(in the wave range of 700~900 nm)successfullyon a milli second time scale without the involvement of mechanical movements.In this paper,firstly,we analyze the error source of the new measurement method,and we find that the major error source is that the transmittance of the convex lens is a function of the incident angle;then,based on optical simulation,we obtain the relationship of the convex lens’s optical transmittance versus the incident angle,and meanwhile propose the method to correctthe error;finally,based on the experimental result,the error correction method is experimentally tested.Data analysis result demonstrates that,in the wave range of 700~900 nm,the mean absolute error between the two measured spectral diffraction efficiencies by using the new and the currently popular methods has been decreased from 0.207%(before error correction)to 0.099%(after error correction),considering the measurement accuracyof the currently popular method is around 0.1%,we think the error correction method provided in this paper can successfully eliminate the main error source of the new measurement technique for obtaining the spectral diffraction efficiencies of a grating.