Correlated self-heterodyne method for ultra-low-noise laser linewidth measurements

TL;DR

The paper introduces a correlated self-heterodyne method that enables ultra-low-noise laser linewidth measurements with high precision, low power, and fast data acquisition, advancing laser characterization techniques.

Contribution

A novel correlated self-heterodyne approach for measuring extremely low laser frequency noise with improved sensitivity and efficiency.

Findings

Achieved measurement of frequency noise as low as 0.01 Hz$^2$/Hz at 1 MHz offset

Demonstrated the method's effectiveness with commercial and lab-built lasers

Features include low optical power, rapid acquisition, and high noise rejection

Abstract

Narrow-linewidth lasers are important to many applications spanning precision metrology to sensing systems. Characterization of these lasers requires precise measurements of their frequency noise spectra. Here we demonstrate a correlated self-heterodyne (COSH) method capable of measuring frequency noise as low as 0.01 Hz$^2$/Hz at 1 MHz offset frequency. The measurement setup is characterized by both commercial and lab-built lasers, and features low optical power requirements, fast acquisition time and high intensity noise rejection.