Brazas J C, Li L
Appl Opt. 1995 Jul 1;34(19):3786-92. doi: 10.1364/AO.34.003786.
Planar waveguide-grating couplers are analyzed to determine the effects of grating length, the incident beam size, and the coupling length of the grating on the input-coupling efficiency. The emphasis is to examine the effects of these finite lengths on the range of angles over which input coupling occurs and the shape of the efficiency curve. A general formula for normalized input-coupling efficiency is given to relate these lengths. When any one of these characteristic lengths is much smaller than the other two, both the angular width and angular dependence of the coupling efficiency for a scan of the incident beam angle will be mainly determined by that characteristic length. This is demonstrated experimentally for two cases: one has a relatively short grating length, and the other has a short coupling length.
对平面波导光栅耦合器进行分析，以确定光栅长度、入射光束尺寸和光栅耦合长度对输入耦合效率的影响。重点是研究这些有限长度对输入耦合发生的角度范围以及效率曲线形状的影响。给出了归一化输入耦合效率的通用公式，以关联这些长度。当这些特征长度中的任何一个远小于其他两个时，对于入射光束角度扫描，耦合效率的角宽度和角度依赖性将主要由该特征长度决定。针对两种情况进行了实验验证：一种情况是光栅长度相对较短，另一种情况是耦合长度较短。
