Metrology-grade mid-infrared spectroscopy for multi-dimensional perception
Abstract
The mid-infrared spectral window is essential for molecular fingerprinting and atmospheric sensing, yet unlocking its full potential is currently constrained by a fundamental instrumental trade-off: existing systems cannot simultaneously deliver broad bandwidth, high photon flux, and metrological frequency fidelity. Here, we resolve this bottleneck by demonstrating a metrology-grade spectroscopic system based on difference frequency generation, driven by widely tunable, near-infrared diode lasers traceable to atomic standards. Our system achieves continuous tunability across the 3-3.7 m atmospheric window and delivers output power exceeding 45 mW with an absolute frequency accuracy of 7.2 MHz. We harness this convergence to overcome a critical barrier in integrated photonics, unambiguously identifying and eliminating hydrogen-induced absorption in silicon nitride microresonators to achieve an 88-fold reduction in optical loss. We further reveal multi-phonon absorption in the silica cladding as the fundamental limit to mid-infrared integrated photonics. Finally, we demonstrate the system's versatility through scattering-resilient LiDAR capable of penetrating optically dense fog, and dual-modality sensing that simultaneously retrieves target distance and chemical composition. By unifying the rigor of frequency metrology with the versatility of broadband sensing, this architecture establishes a new paradigm for multi-dimensional perception in complex environments.
Cite
@article{arxiv.2602.00958,
title = {Metrology-grade mid-infrared spectroscopy for multi-dimensional perception},
author = {Baoqi Shi and Chenxi Zhang and Ming-Yang Zheng and Yue Hu and Zeying Zhong and Zhenyuan Shang and Wenbo Ma and Xiu-Ping Xie and Xue Bai and Yi-Han Luo and Anting Wang and Hairun Guo and Qiang Zhang and Junqiu Liu},
journal= {arXiv preprint arXiv:2602.00958},
year = {2026}
}