High-precision laser spectrum analyzer via digital decoherence

TL;DR

This paper introduces a digital decoherence-based laser spectrum analyzer capable of high-precision noise spectrum measurement for ultra-stable lasers, with broad wavelength compatibility and ultra-low linewidth detection.

Contribution

The work presents a novel digital decoherence method for laser spectrum analysis, achieving sub-Hz linewidth measurement with broad wavelength adaptability.

Findings

Measured beta-line linewidth of 570 mHz at 10 seconds

Minimum observable linewidth of 133 mHz

System noise floor corresponds to 210 mHz beta-line linewidth at 25 seconds

Abstract

With the continuous advancement of laser technology, accurately evaluating the noise spectrum of high-performance lasers has become increasingly challenging. In this work, we demonstrate a high-precision laser spectrum analyzer based on the proposed digital decoherence method, which can precisely measure the frequency noise spectrum of sub-Hz linewidth lasers. In addition, it has broad wavelength compatibility, which enables convenient switching between lasers with different center wavelengths. Its performance is validated through measurements of ultra-stable lasers. Based on the measured frequency noise power spectral density, a beta-line linewidth is determined to be 570 mHz at 10-second observation time, and the minimum observable linewidth is calculated to be 133 mHz. The system's noise floor is evaluated to be 210 mHz beta-line linewidth at 25-second observation time, and a minimum observable linewidth of 39 mHz.