Chasi-Guided Modes and Related Radiation Losses in Optical Dielectric Waveguides with External Higher Index Surroundings
Chasi-Guided Modes and Related Radiation Losses in Optical Dielectric Waveguides with External Higher Index Surroundings
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具有外部较高折射率环境的光学介质波导中的 Chasi 引导模式和相关辐射损耗
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发表时间：
1975
期刊：
影响因子：
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通讯作者：
K. Furuya
中科院分区：
文献类型：
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作者：
Y. Suematsu;K. Furuya
从理论上讲，在由一个核心和一个被外部高折射率区域进一步包围的薄包层组成的光介质波导中发现了模式滤波作用。通常被认为是截止模的传播波，在一定条件下可以以很小的损耗被引导。这些波在这里被定义为准导模。当包层厚度无限增大时，这些模态趋向于波导的导模。给出了一种估算损耗的方法。作为一个例子，给出了对称平板波导的辐射损耗公式，并发现其近似与准导模模数的立方成正比。因此，准导模的损耗与模数密切相关。建议在包层型多模光纤外覆盖高折射率环境，并合理选择参数，可将大芯径光纤用作准单模光纤。
Mode filter actions are found theoretically in an optical dielectric waveguide consisting of a core and a thin cladding layer which is further surrounded by an external higher index region. The propagating waves, which are usually considered to be cutoff modes, can be guided with a small amount of loss under a certain condition. These waves are defined here as quasi-guided modes. These modes tend to the guided modes of the guide when the cladding thickness increases infinitely. A method is given to estimate the losses. As an example, the radiation losses are formulated for a symmetric slab waveguide, and are found to be approximately proportional to the cube of the mode number of the quasi-guided mode. Therefore, losses of the quasi-guided modes depend strongly on the mode number. It is suggested that fibers with large core diameters can be used as quasi-single mode fibers by covering the clad-type multimode fibers with external higher index surroundings and choosing the parameters properly.