High-Efficiency Orbital Angular Momentum Beams Multiplexing System With Compact Shaper and Transformation Optics

In recent years, mode-division multiplexing (MDM) has been intensively proposed to cope with the information capacity crisis. However, how to multiplex a large number of OAM modes efficiently with low insertion loss and broad bandwidth is still a crucial issue. To solve this problem, we design a multiplexing system in which we make two functional blocks including a compactable shaper and a pair of free-form refractive optical elements. In one block, a self-designed compactable shaper is used to turn the Gaussian beam output from a single mode fiber into the elongated beams with tilted plane wave so that it can meet the phase requirement for the subsequently transformation. In the other block, a pair of free-form refractive optical elements is reversely used to multiplex multi modes based on coordinate transformations. Based on these structures, OAM multiple modes multiplexing experiment has been successfully performed in C+L band and the insertion losses of all modes are less than 1.6 dB. Furthermore, in the limited number of modes, the energy insertion loss does not increase with the increase of the number of OAM modes. The scheme offers a great potential for the integration in the next platform of MDM.

Automated summary

The study presents a multiplexing system designed to efficiently multiplex a large number of OAM modes. The system includes a compactable shaper and a pair of free-form refractive optical elements. Experimental results demonstrate the successful multiplexing of OAM multiple modes in the C+L band.