High-speed tunable microwave-rate soliton microcomb

TL;DR

This paper introduces a high-speed tunable microwave-rate soliton microcomb with rapid frequency modulation capabilities, significantly advancing microcomb technology for microwave photonics and related applications.

Contribution

It demonstrates the first microcomb with a tunable repetition rate at microwave speeds using electro-optic modulation in lithium niobate, achieving unprecedented modulation bandwidth and rate.

Findings

Achieved a modulation bandwidth of up to 75 MHz.

Realized a continuous frequency modulation rate of 5.0 x 10^14 Hz/s.

Enabled microwave signal rate tuning across X - W bands.

Abstract

Microwave signal generation with fast frequency tuning underlies many applications including sensing, imaging, ranging, time keeping, wireless communication, and high-speed electronics. Soliton microcombs are a promising new approach for photonic-based microwave signal synthesis. To date, however, tuning rate has been limited in microcombs (and in frequency combs generally). Here, we demonstrate the first microwave-rate soliton microcomb whose repetition rate can be tuned at a high speed. By integrating an electro-optic tuning/modulation element into a lithium niobate comb microresonator, a modulation bandwidth up to 75 MHz and a continuous frequency modulation rate up to 5.0 * 10^14 Hz/s are achieved, several orders-of-magnitude faster than existing microcomb technology. These features are especially useful for disciplining an optical VCO to a long-term reference such as an optical clock or for tight phase lock in dual-microcomb clocks or synthesizers. Moreover, the microwave signal rate can be set to any X - W band rate. Besides its positive impact on microwave photonics, fast repetition rate control is generally important in all applications of frequency combs.