# Phase-multiplied interferometry via cavity dynamics for resolution-enhanced coherent ranging

## TL;DR

This paper introduces a new LiDAR technique that improves resolution without increasing system complexity.

## Contribution

A cavity dynamics-based method is proposed to enhance ranging resolution through phase multiplication without physical modulation.

## Key findings

- Up to the 13th-order harmonic was experimentally excited with effective phase multiplication.
- The system achieved resolution enhancement by more than 10 times with micrometer-level precision.
- Low photon consumption and improved signal-to-noise ratio were observed.

## Abstract

Coherent light detection and ranging (LiDAR) has become an indispensable tool in autonomous systems, offering exceptional precision and ambient-light immunity. Recently, applications spanning from scientific research to advanced manufacturing have increasingly required resolution that exceeds current capabilities, which faces a fundamental trade-off between improved performance and system complexity. In this study, we overcome the intrinsic limitation and present a cavity dynamics-enabled approach that actively enhances the ranging resolution through phase multiplication. By injecting target-scattered light into the optical resonator, the operating frequency of the laser undergoes periodic modulation, generating interference harmonics that multiply the phase sensitivity. Experimentally, we observe the excitation of up to the 13th-order harmonic and effective phase multiplication without physical modulation extensions, which enables more than 10 times resolution enhancement for ranging. Owing to the intrinsic phase correlation between the fundamental wave and harmonic waves, the phase noise is effectively controlled, resulting in high-precision ranging with a standard deviation on the order of tens of micrometers. The system concurrently leverages laser feedback sensitivity, achieving significant signal-to-noise ratio (SNR) improvement. With its enhanced resolution, low photon consumption, and low-cost implementation, this technology demonstrates new capabilities that promise to enable a wide range of applications.