Laser beam profile analysis of a hole coupled free-electron laser

Abstract

We present measurements and numerical simulations of the laser beam transverse profile of the CLIO infrared free-electron laser (FEL). This FEL uses a hole coupling extraction system, which introduces important perturbation on the intracavity optical mode. We show that this intracavity mode tends to avoid the extraction hole and that the output power optimization leads to an off-axis laser alignment inside the FEL cavity.