On-chip generation and control of the vortex beam

TL;DR

This paper introduces a robust on-chip holographic grating method for generating and controlling optical vortex beams with high fidelity and bandwidth, enabling advanced integrated optical devices for various applications.

Contribution

The work presents a novel microscale holographic grating design for on-chip vortex beam generation with high fidelity and bandwidth, including a multi-grating system for flexible modulation.

Findings

Fidelity of 0.93 in vortex beam generation

Bandwidth of about 175 nm with high fidelity

Effective modulation using dual gratings controlling input phase

Abstract

A new method to generate and control the amplitude and phase distributions of a optical vortex beam is proposed. By introducing a holographic grating on top of the dielectric waveguide, the free space vortex beam and the in-plane guiding wave can be converted to each other. This microscale holographic grating is very robust against the variation of geometry parameters. The designed vortex beam generator can produce the target beam with a fidelity up to 0.93, and the working bandwidth is about 175 nm with the fidelity larger than 0.80. In addition, a multiple generator composed of two holographic gratings on two parallel waveguides are studied, which can perform an effective and flexible modulation on the vortex beam by controlling the phase of the input light. Our work opens a new avenue towards the integrated OAM devices with multiple degrees of optical freedom, which can be used for optical tweezers, micronano imaging, information processing, and so on.