# Quantum-limited measurements of intensity noise levels in Yb-doped fiber amplifiers

## TL;DR

This paper measures the intensity noise spectrum of Yb-doped fiber amplifiers near the quantum noise limit, revealing high noise levels and the influence of seed laser characteristics, with implications for optimizing high-power fiber amplifiers.

## Contribution

It provides the first detailed frequency-resolved noise measurements of Yb-doped fiber amplifiers near the quantum limit, highlighting seed source impact and optimization opportunities.

## Key findings

- Intensity noise exceeds 60 dB above shot noise at certain frequencies
- Seed laser noise characteristics significantly affect amplifier noise performance
- Potential for noise reduction and optimization in high-power fiber amplifiers

## Abstract

We investigate the frequency-resolved intensity noise spectrum of an Yb-doped fiber amplifier down to the fundamental limit of quantum noise. We focus on the kHz and low MHz frequency regime with special interest in the region between 1 and 10 kHz. Intensity noise levels up to >60 dB above the shot noise limit are found, revealing great optimization potential. Additionally, two seed lasers with different noise characteristics were amplified, showing that the seed source has a significant impact and should be considered in the design of high power fiber amplifiers.