Complete leaky mode coupling in dual-core photonic crystal fibre based on the coupled-mode theory

This paper theoretically investigates the dependence of leaky mode coupling between inner core fundamental mode and outer core defect mode on phase and loss matching in pure silica dual-core photonic crystal fibres with the multi-pole method. The complete mode coupling can take place when both the phase and loss matching conditions are satisfied at the avoided anti-crossing wavelength. It shows the influences of cladding structure parameters including the diameters of cladding air holes d1, diameters of outer core holes d2 and hole to hole pitch Λ on the characteristics of leaky modes coupling. The coupled-mode theory is used to analyse the mode transition characteristics and the complete coupling can be clearly indicated by comparing the real and imaginary parts of propagation constant of the leaky modes.

本文利用多极法从理论上研究了纯二氧化硅双芯光子晶体光纤中内芯基模和外芯缺陷模之间的泄漏模耦合对相位和损耗匹配的依赖性。当在避免的反交叉波长处相位和损耗匹配条件都满足时，完全的模式耦合能够发生。文中展示了包层结构参数（包括包层空气孔直径\(d_1\)、外芯孔直径\(d_2\)以及孔间距\(\Lambda\)）对泄漏模耦合特性的影响。利用耦合模理论分析了模式转换特性，并且通过比较泄漏模传播常数的实部和虚部可以清晰地表明完全耦合。