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本文提出了一种设计极化无关光栅耦合器的新方法。阐明了利用光学等离子体模式实现相位匹配的基本原理;从严格的模式匹配法出发,将求解光栅中的电磁波传播问题归结为一个传输线模型。通过解边值问题,及利用横向谐振原理,求出光栅的色散特性及其与结构尺寸的关系。这种方法物理概念清楚,特别适合计算机作数值计算。数值计算结果表明,采用这种方法设计的极化无关光栅耦合器,不但使相反极化模式在相位上匹配,而且具有相同的损耗系数。这就为设计高效率的耦合器提供了一种优选设计方法。
This paper presents a new method for designing polarization-independent grating couplers. The principle of phase matching using optical plasmas is expounded. Based on the strict pattern matching method, the problem of electromagnetic wave propagation in the grating is reduced to a transmission line model. By solving the boundary value problem and using the principle of transverse resonance, the dispersion characteristics of the grating and its relationship with the size of the structure are obtained. The physical concept of this method is clear, especially for computer numerical calculation. The numerical results show that the polarization-independent grating couplers designed in this way not only match the phase of the opposite polarization modes but also have the same loss coefficient. This provides a preferred design method for designing an efficient coupler.