# Multi‐Soliton Microcombs Enable Ultrafast Nanometric‐Precision Ranging and Photon‐Level Detection

## TL;DR

This paper introduces a new method using multi-soliton microcombs for ultrafast and highly precise optical measurements, achieving nanometer-level accuracy and enabling applications like vibration monitoring and drone tracking.

## Contribution

The first demonstration of dual-multi-soliton ranging, achieving nanometric precision and photon-level detection with improved speed and efficiency.

## Key findings

- Measurement uncertainty within ±17 nm and precision of 1.43 nm at 2 µs using three-soliton combs.
- Photon-level ranging achieves ±9.5 µm uncertainty and 202 nm precision at 50 s with femtowatt-level power.
- Outdoor measurements and non-line-of-sight imaging demonstrate practical applicability of the method.

## Abstract

Optical microcombs offer unprecedented capabilities in precision ranging due to their compact footprint, broad spectral bandwidth, and high repetition rates. However, practical deployment is limited by a fundamental compromise: single‐soliton states exhibit high coherence but low power conversion efficiency, whereas chaotic microcombs achieve higher efficiency at the expense of significant phase noise. Here, we overcome both limitations by implementing multi‐soliton microcombs in dual‐comb system. Multi‐soliton states provide higher efficiency and easier accessibility than single‐soliton states, while maintaining high coherence essential for nanometric precision compared to chaotic states. Experimental results indicate that utilizing three solitons in both combs, the measurement uncertainty is within ±17 nm and the precision reaches 1.43 nm at 2 µs and 3.42 pm at 500 µs. We also demonstrate vibration monitoring, spinning disk measurement, and unmanned aerial vehicle tracking. Moreover, with the five‐soliton signal comb and single‐soliton local comb, photon‐level ranging at femtowatt‐level power exhibits the uncertainty below ±9.5 µm, achieving the precision of 3.57 µm at 1 s and 202 nm at 50 s. Additionally, we conduct outdoor measurements at ∼270 m and non‐line‐of‐sight imaging. Multi‐soliton ranging outperforms single‐soliton approaches in precision, speed and efficiency, creating new opportunities in communications, spectroscopy, and optical time transfer.

Our work first demonstrates dual‐multi‐soliton ranging and confirms its multifunctional capability. The method achieves ultrafast and nanometric‐precision measurement. For practical applications, we further extend the multi‐soliton states to photon‐level ranging. The proposed system surpasses the single‐soliton approaches in precision, speed, and efficiency, offering new opportunities for communications, spectroscopy, and optical time transfer.