Gupta M C, Li L
Appl Opt. 1991 Oct 20;30(30):4402-5. doi: 10.1364/AO.30.004402.
Results of theoretical calculations and experimental measurements of variation of grating coupling efficiency with beam-defocus position are presented. Our results indicate that (1) coupling efficiency is not necessarily maximum at the beam waist, (2) coupling efficiency as a function of defocus position shows oscillatory behavior particularly for a tightly focused beam. The effect of beam size alone cannot account for the observed behavior of variation of coupling efficiency with defocus position. The results of measured angular dependence of coupling efficiency for various defocus conditions are also presented.
给出了光栅耦合效率随光束离焦位置变化的理论计算和实验测量结果。我们的结果表明：（1）耦合效率不一定在束腰处最大；（2）耦合效率作为离焦位置的函数呈现出振荡行为，特别是对于紧聚焦光束。仅光束尺寸的影响无法解释所观察到的耦合效率随离焦位置变化的行为。还给出了各种离焦条件下耦合效率的测量角度依赖性结果。
