# A high-gain Quantum free-electron laser: emergence & exponential gain

## TL;DR

This paper develops a quantum model for free-electron lasers, demonstrating exponential gain and high-gain operation potential, while analyzing the super-Poissonian intensity fluctuations of the emitted radiation.

## Contribution

It introduces an effective Dicke model in momentum space to describe quantum collective effects in FELs, enabling high-gain operation without X-ray FEL oscillators.

## Key findings

- Exponential gain achievable in quantum FELs from a single electron passage
- High-gain mode operation possible without X-ray FEL oscillators
- Intensity fluctuations are super-Poissonian

## Abstract

We derive an effective Dicke model in momentum space to describe collective effects in the quantum regime of a free-electron laser (FEL). The resulting exponential gain from a single passage of electrons allows the operation of a Quantum FEL in the high-gain mode and avoids the experimental challenges of an X-ray FEL oscillator. Moreover, we study the intensity fluctuations of the emitted radiation which turn out to be super-Poissonian.