In this study, we achieved sub-nanometer precision approaching the standard quantum limit in distance measurements using an optical-comb-based spectral-domain interferometer. Concretely, the measurement precision was 0.67 nm for an average measurement time of 25 μs, and the measurement sensitivity was 4.5×10⁻¹² m/√Hz, which corresponds to a level close to the quantum limit. These results can be applied to precise observation of physical phenomena; as one example presented in the paper, we demonstrated remote detection and reconstruction of acoustic signals in the audible frequency band by measuring minute vibrations induced in a thin film by acoustic waves. Such outcomes are expected to serve as an important stepping stone toward practical implementation of next-generation length standards.
The spectral interferometer implemented in this work used Meter-Lab’s commercially available near-infrared ultra-precise high-speed spectrometer s-Nova-1550. The s-Nova-1550’s strengths—maximum measurement speed (40 kHz) and high wavelength resolution (0.1 nm)—played a key role in enabling nanometer-scale absolute distance measurements for audible-band acoustic wave detection (typically 20 Hz–20 kHz), which was presented as a practical example in the paper. Notably, achieving distance-measurement precision close to the quantum limit also confirmed the s-Nova-1550’s measurement stability during high-speed operation.
Detection and reconstruction results for acoustic signals exhibiting sub-nanometer vibrations (source: Laser & Photonics Reviews, January 2025)
