Optoelectronic nibbling of laser linewidth using a Brillouin-assisted optical phase-locked loop

TL;DR

This paper presents a method using a Brillouin-assisted optical phase-locked loop to significantly narrow the linewidth of a laser, achieving a reduction of over 90 dB at 100 Hz and an estimated linewidth below 2 Hz, applicable to various lasers.

Contribution

It introduces a wavelength-independent technique that dramatically reduces laser phase noise using a Brillouin-assisted phase-locked loop.

Findings

Over 90 dB noise reduction at 100 Hz

Laser linewidth narrowed to below 2 Hz

Method applicable to nearly any laser wavelength

Abstract

We demonstrate that the implementation of phase-locked loop forbidding multimode operation of a long Brillouin resonator also leads to a dramatic reduction of the optical phase noise of the pump itself. In the case of a continuous Er,Yb:glass laser, a reduction by more than 90 dB at 100 Hz of the carrier is observed. This yields an optical linewidth estimated narrower than 2 Hz for the pump laser. The method being independent of the laser wavelength, it can be applied to almost any laser.