# Modal analysis of noise propagation in a femtosecond oscillator

## TL;DR

This paper investigates how external pump noise affects a femtosecond oscillator by using a novel spectrally-resolved homodyne detection technique to analyze noise modes, revealing detailed noise distribution and propagation dynamics.

## Contribution

It introduces a modal analysis approach for noise in femtosecond oscillators, providing a more comprehensive understanding compared to traditional methods.

## Key findings

- Spectrally-resolved homodyne detection captures amplitude and phase noise simultaneously.
- Modal analysis reveals detailed noise distribution across spectral modes.
- The method outperforms conventional noise detection techniques in physical insight.

## Abstract

We study noise propagation dynamics in a femtosecond oscillator by injecting external noise on the pump intensity. We utilize a spectrally-resolved homodyne detection technique that enables simultaneous measurement of amplitude and phase quadrature noises of different spectral bands of the oscillator. To reveal the impact of added pump noise on the oscillator noise, we perform a modal analysis of the oscillator noise in which each mode corresponds to a particular temporal/spectral shape of the pulsed light. We compare this modal approach with the conventional noise detection methods and find the superiority of our method in particular unveiling a complete physical picture of noise distribution in femtosecond oscillator.