# Passive, broadband and low-frequency suppression of laser amplitude noise to the shot-noise limit using hollow-core fibre

## TL;DR

This paper demonstrates a hollow-core fibre-based method to passively suppress laser amplitude noise across broad frequency ranges, achieving near shot-noise limit performance for fibre laser systems.

## Contribution

It introduces an enhanced CBD scheme with concatenated circuits for broad and multi-frequency noise suppression in fibre lasers.

## Key findings

- Suppressed 2.6 dB of amplitude noise at MHz frequencies.
- Reduced excess amplitude noise by 85% between 2-6 MHz.
- Achieved near shot-noise limit in fibre laser amplitude noise.

## Abstract

We use hollow-core fibre to preserve the spectrum and temporal profile of picosecond laser pulses in CBD to suppress 2.6 dB of amplitude noise at MHz noise frequencies, to within 0.01 dB of the shot-noise limit. We provide an enhanced version of the CBD scheme that concatenates circuits to suppress over multiple frequencies and over broad frequency ranges --- we perform a first demonstration that reduces total excess amplitude noise, between 2 - 6 MHz, by 85%. These demonstrations enable passive, broad-band, all-guided fibre laser technology operating at the shot-noise limit.