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。

With ultra-high index contrast and ultra-small cross sections, silicon nanometer optical waveguides have super light field limit ability and provide a very promising way to realize nano-photonic integrated circuits with high integration density. It is well-known that mode conversion and coupling play an important role for realizing various functionality elements in photonic integrated circuits. The theory of mode conversion and coupling new structures and devices in silicon photonics integrated circuits are analyzed and discussed in detail. The mode transmission and evolution process of silicon nanometer optical waveguide tapered structure are studied, and the unique polarization-dependent mode conversion mechanism is revealed. The results show that when asymmetry exists in the cross section of the optical waveguide, it is possible to produce polarization mode miscellaneous in some specific waveguide widths. Which provide a convenient method for realizing polarization rotation. By adjusting the phase matching conditions of mode conversion and coupling in asymmetric directional coupled structures, important approaches for realizing ultra-small polarization-beam splitters as well as broadband mode multiplexers/demultiplexers are provided.