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基于薄膜光学的基本理论,利用几何光学的方法推导出一种计算垂直耦合型光探测器吸收层长度的新方法。与基于耦合模理论的设计方法相比,该设计方法更为直观,设计过程更为简单,且确定的光探测器长度与基于耦合模理论的设计方法得到的结果相一致。还利用该方法对垂直耦合型光探测器的结构进行了模拟分析,分析结果表明:波导与吸收层之间的折射率差决定了该类型光探测器的吸收长度,减小二者的折射率差可降低探测器吸收长度,在保证高耦合效率的同时进一步提高器件的高速响应特性。
Based on the basic theory of thin-film optics, a new method to calculate the absorption layer length of vertical-coupling photodetector is deduced by the method of geometrical optics. Compared with the design method based on coupled-mode theory, the design method is more intuitive and the design process is simpler. The length of the photodetector determined is consistent with the result obtained by the design method based on coupled-mode theory. This method is also used to simulate the structure of the vertical coupling type photodetector. The analysis results show that the refractive index difference between the waveguide and the absorber determines the absorption length of the photodetector and the refractive index Poor can reduce the detector absorption length, while ensuring high coupling efficiency and further improve the high-speed response characteristics of the device.