Microwave resonator-enabled broadband on-chip electro-optic frequency comb generation

TL;DR

This paper introduces a power-efficient, on-chip electro-optic frequency comb generator using microwave resonator electrodes on a lithium niobate platform, achieving broadband combs with reduced power and no isolators.

Contribution

The authors develop a microwave resonator-enabled electro-optic comb generator with over three times power reduction and broadband span, improving practicality for integrated photonics applications.

Findings

Achieved >85 nm comb span at 740 mW power.

Reduced electrical power consumption by over three times.

Demonstrated broadband comb generation without RF isolators.

Abstract

Optical frequency combs play a crucial role in optical communications, time-frequency metrology, precise ranging, and sensing. Among various generation schemes, resonant electro-optic combs are particularly attractive for its excellent stability, flexibility and broad bandwidths. In this approach, an optical pump undergoes multiple electro-optic modulation processes in a high-Q optical resonator, resulting in cascaded spectral sidebands. However, most resonant electro-optic combs to date make use of lumped-capacitor electrodes with relatively inefficient utilization of the input electrical power. This design also reflects most electrical power back to the driving circuits and necessitates costly RF isolators in between, presenting substantial challenges in practical applications. To address these issues, we present an RF circuit friendly electro-optic frequency comb generator incorporated with on-chip coplanar microwave resonator electrodes, based on a thin-film lithium niobate platform. Our design achieves more than three times electrical power reduction with minimal reflection at the designed comb repetition rate of ~ 25 GHz. We experimentally demonstrate broadband electro-optic frequency comb generation with a comb span of >85 nm at a moderate electrical driving power of 740 mW (28.7 dBm). Our power-efficient and isolator-free electro-optic comb source could offer compact, low-cost and simple-to-design solution for applications in spectroscopy, high-precise metrology, optical communications.