Recirculating Light Phase Modulator

TL;DR

This paper introduces a recirculating light phase modulator that enhances modulation efficiency by looping light multiple times through a waveguide, reducing power requirements significantly.

Contribution

It proposes and demonstrates a novel recirculating phase modulator that increases efficiency by multiple light passes in a non-resonant waveguide structure.

Findings

Achieved ninefold reduction in power for the same modulation index.

Demonstrated experimental viability of the recirculating approach.

Potential applications in tunable optical frequency combs.

Abstract

High efficiency and a compact footprint are desired properties for electro-optic modulators. In this paper, we propose, theoretically investigate and experimentally demonstrate a recirculating phase modulator, which increases the modulation efficiency by modulating the optical field several times in a non-resonant waveguide structure. The 'recycling' of light is achieved by looping the optical path that exits the phase modulator back and coupling it to a higher order waveguide mode, which then repeats its passage through the phase modulator. By looping the light back twice, we were able to demonstrate a recirculating phase modulator that requires nine times lower power to generate the same modulation index of a single pass phase modulator. This approach of modulation efficiency enhancement is promising for the design of advanced tunable electro optical frequency comb generators and other electro-optical devices with defined operational frequency bandwidths.