Broadband Phase-Noise Suppression in a Yb-Fiber Frequency Comb

TL;DR

This paper demonstrates a simple active intensity noise servo technique to significantly suppress high-frequency phase noise in a Yb-fiber optical frequency comb, improving its stability for precision applications.

Contribution

The authors introduce a novel active intensity noise servo method that effectively reduces phase noise in a Yb-fiber frequency comb, leveraging the correlation between intensity and phase noise.

Findings

Phase noise suppressed by ≥7 dB up to 100 kHz

Suppression achieved with a unity-gain crossing of -700 kHz

Dominant noise sources identified as amplified spontaneous emission

Abstract

We report a simple technique to suppress high frequency phase noise of a Yb-based fiber optical frequency comb using an active intensity noise servo. Out-of-loop measurements of the phase noise using an optical heterodyne beat with a continuous wave (cw) laser show suppression of phase noise by \geq7 dB out to Fourier frequencies of 100 kHz with a unity-gain crossing of -700 kHz. These results are enabled by the strong correlation between the intensity and phase noise of the laser. Detailed measurements of intensity and phase noise spectra, as well as transfer functions, reveal that the dominant phase and intensity noise contribution above -100 kHz is due to amplified spontaneous emission (ASE) or other quantum noise sources.