Optimization design of mode-selective ring core photonic lantern based on coupled local mode theory

Abstract

In this paper, optical field transmission characteristics of a mode-selective ring core photonic lantern (MSRCPL) are theoretically analyzed and its optimization design is also investigated. This MSRCPL is based on a tapered fiber bundle of coreless fiber and glass capillary with low refractive index. Mode evolution characteristics in the taper region and mode coupling characteristics at the splicing point are analyzed. The coupled local mode theory (CLMT) is used to optimize the structure of a 3-port MSRCPL and a 5-port MSRCPL. The impact of taper length, taper shape, taper waist, and geometric arrangement on mode selectivity are calculated. Calculation results indicate that the mode selectivities of the optimized 3-port and 5-port MSRCPL are higher than 23 dB and 18 dB, respectively.