# Performing MHz-Level Repetition Rate Tuning for Coherent Dual-Microcomb Interferometry

## TL;DR

This paper introduces a new method to tune microcombs for high-precision measurements, making it easier to integrate and use in applications like gas detection.

## Contribution

A hybrid tuning method combining SSB modulation and thermal control enables MHz-level repetition rate tuning in dual-microcomb interferometry.

## Key findings

- A hybrid tuning method achieves continuous repetition rate tuning across a 4.34 MHz range.
- The repetition rate shows a linear dependence on pump modulation frequency with a coefficient of 143.58 kHz/GHz.
- The method reduces the need for precise microresonator pairing, improving practicality for spectroscopy and ranging.

## Abstract

The high-repetition-rate dual-microcomb interferometry, characterized by its high precision, rapid measurement speed, and ease of integration, shows significant promise in applications such as precision spectroscopy and high-speed precision ranging. As dual-microcomb interferometry usually requires a specific difference in repetition rates, tuning the repetition rate of the microcomb is crucial for integrating dual-microcomb sources and enhancing the measurement performance, including the precision and the update rate. This work demonstrates a coherent dual-microcomb system driven by a single continuous-wave fiber laser at 1560.49 nm. The system employs a hybrid tuning method combing single-sideband (SSB) modulation for precision pump frequency control (enabling continuous repetition rate tuning across a 4.34 MHz range) with thermal control for coarse tuning. The linear dependence between the repetition rate and pump modulation frequency shows a measured coefficient of 143.58 kHz/GHz. This method enables dual microcombs with MHz-level repetition rate tuning, significantly relaxing the fabrication and pairing requirements for microresonators. The advancement is particularly valuable for dual-comb spectroscopy and ranging applications, including gas detection and satellite formation flying.