Approaching the quantum-limited precision in frequency-comb-based spectral interferometry for length measurements

TL;DR

This paper demonstrates near-quantum-limited precision in frequency-comb-based spectral interferometry for length measurements, achieving sub-nanometer accuracy and practical applications like vibration and eavesdropping detection.

Contribution

It reports the first measurement of spectral interferometry approaching the quantum limit with sub-nanometer precision, advancing length metrology technology.

Findings

Achieved 0.67 nm measurement precision at 25 us averaging time

Measured sensitivity of 4.5×10^-12 m/Hz^1/2 close to quantum limit

Demonstrated practical applications in vibration and eavesdropping detection

Abstract

Over the last two decades, frequency combs have brought breakthroughs in length metrology with traceability to length standards. In particular, frequency-comb-based spectral interferometry is regarded as a promising technology for next-generation length standards. However, to achieve this, the nanometer-level precision inherent in laser interferometer is required. Here, we report distance measurements by a frequency-comb-based spectral interferometry with sub-nm precision close to a standard quantum limit. The measurement precision was confirmed as 0.67 nm at an averaging time of 25 us. The measurement sensitivity was found to be 4.5 10-12m/Hz1/2, close to the quantum-limit. As a practical example of observing precise physical phenomena, we demonstrated measurements of acoustic-wave-induced vibration and laser eavesdropping. Our study will be an important step toward the practical realization of upcoming length standards.