Ultra-broadband on-chip twisted light emitter for optical communications

Zhenwei Xie,Luping Du,Haodong Qiu,Hong Wang,Zhaohui Li,Zecen Zhang,Ting Lei,Xiaocong Yuan,Changjun Min,Fan Li

doi:10.1038/lsa.2018.1

Abstract

On-chip twisted light emitters are essential components of orbital angular momentum (OAM) communication devices1, 2. These devices address the growing demand for high-capacity communication systems by providing an additional degree of freedom for wavelength/frequency division multiplexing (WDM/FDM). Although whispering-gallery-mode-enabled OAM emitters have been shown to possess some advantages3, 4, 5, such as compactness and phase accuracy, their inherent narrow bandwidths prevent them from being compatible with WDM/FDM techniques. Here, we demonstrate an ultra-broadband multiplexed OAM emitter that utilizes a novel joint path-resonance phase control concept. The emitter has a micron-sized radius and nanometer-sized features. Coaxial OAM beams are emitted across the entire telecommunication band from 1,450 to 1,650 nm. We applied the emitter to an OAM communication with a data rate of 1.2 Tbit/s assisted by 30-channel optical frequency combs (OFCs). The emitter provides a new solution to further increase capacity in the OFC communication scenario.

Highlights

On-chip twisted light emitters are essential components of orbital angular momentum (OAM) communication devices[1,2]
We applied the emitter to an OAM communication with a data rate of 1.2 Tbit/s assisted by 30-channel optical frequency combs (OFCs)
OAM has attracted considerable attention for use in mode division multiplexing in free space and in fiber applications for both classical and quantum communication systems[1,2,14,15,16,17]; the infinite number of orthogonal states of OAM provide an additional degree of freedom to the conventional multiplexing techniques[18]

Summary

Δc Silicon

Structures were around 100 nm in size (Supplementary Section 2). Figure 1b shows the detailed structures and the phase modulation scheme of the OAM emitter. The intensity profiles demonstrate asymmetry at some wavelengths, the relatively small phase deviations still ensure the high mode purity of the OAM (Supplementary Section 3). This demonstrates that the generated OAM modes possess the desired phase distribution across the entire 200-nm-wide telecommunication band. To verify that the proposed approach can be adapted to a device design for simultaneously emitting a large number of OAM modes, we designed and demonstrated a four-port OAM emitter with FDTD simulations (see Supplementary Information, Section 3.3). The BER curves for the back-to-back doi:10.1038/lsa.2018.1

BER BER BER

Fabrication process of the OAM emitter