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硅纳米光波导具有超高折射率差与超小横截面,因而具有超强光场限制能力,为实现超高集成度纳米光子回路提供了一种极具吸引力的途径。众所周知,在光子集成回路中,模式转换与耦合是实现各种功能器件的重要基础。对硅光子集成回路中的模式转换与耦合原理、新结构与新器件进行了详细分析和讨论。研究了硅纳米光波导锥形结构中模式传输及演化过程,揭示了其特有的偏振相关模式转换机制。结果表明,当光波导横截面存在不对称性时,可能在某些特定波导宽度范围内产生偏振模杂化,为实现偏振旋转提供了一种方便的方法。通过调控非对称定向耦合结构中模式转换与耦合的相位匹配条件,为实现超小型偏振分束器、大带宽模式复用-解复用器等关键器件提供重要途径。
Silicon nano-optical waveguide with ultra-high refractive index difference and ultra-small cross-section, which has super-light field limiting capability for the realization of ultra-highly integrated nano-photonic circuit provides an attractive way. As we all know, in the photonic integrated circuit, mode conversion and coupling is to achieve an important basis for a variety of functional devices. The mode conversion and coupling principle, new structure and new device in the silicon photonic integrated circuit are analyzed and discussed in detail. The mode propagation and evolution in the tapered structure of silicon nano-optical waveguide were studied, and its unique polarization-dependent mode switching mechanism was revealed. The results show that when the cross section of optical waveguide is asymmetric, polarization mode hybridization may occur in some waveguide widths, which provides a convenient method for polarization rotation. By controlling the phase matching conditions of mode conversion and coupling in an asymmetric directional coupling structure, it provides an important approach for realizing the key components such as ultra-miniature polarization beam splitter and wideband mode multiplexer-demultiplexer.