Coherent X-rays with Tunable Time-Dependent Polarization

TL;DR

This paper presents a method to generate high-power, coherent X-ray pulses with tunable, time-dependent polarization using a free electron laser, achieved through temporal intensity modulation and polarization switching techniques.

Contribution

It introduces a novel approach for producing femtosecond-scale, polarization-tunable X-ray pulses via self seeding and electron beam modulation, with detailed simulation results.

Findings

Successful simulation of polarization switching configurations

Demonstration of femtosecond temporal modulation of polarization

Feasibility of implementing this method at LCLS-II

Abstract

We describe a method for producing high power, coherent x-ray pulses from a free electron laser with femtosecond scale periodic temporal modulation of the polarization vector. This approach relies on the generation of a temporal intensity modulation after self seeding either by modulating the seed intensity or the beam current. After generating a coherent temporally modulated $s$-polarization pulse, the electron beam is delayed by half a modulation period and sent into a short orthogonally oriented undulator, serving as a $p$-polarization afterburner. We provide simulations of three configurations for realizing this polarization switching, namely, enhanced self seeding with an intensity modulation generated by 2 color self seeding, enhanced self seeding of a current modulated bunch, and regular self seeding of a current modulated bunch. Start to end simulations for the Linac Coherent Light Source-II are provided for the latter.