Suppression of self-pulsing instabilities in free-electron lasers using delayed optical feedback

Abstract

We show that the macropulse instability affecting storage ring free-electron laser (FEL) oscillators can be suppressed using a delayed optical feedback. The principle, known as coherent photon seeding, consists in reinjecting a very small part of the laser output in the laser cavity in order to create a new deterministic solution. The feedback is shown to be efficient over a large range of the detuning parameter of the FEL cavity, even with very small fractions of reinjected power (< 10 À8 here from inside to inside the cavity). The experiments have been performed on the UVSOR-II storage ring free-electron laser.

Three-Dimensional, Time-Dependent Analysis of High- and Low-Q Free-Electron Laser Oscillators

“…Techniques well known from laser physics have also been applied to FEL oscillators, either experimentally or in a conceptual study, such as injection seeding [150][151][152][153][154][155] and mode locking [133,151,152,156]. On the other hand, the unique nature of the gain process in FELs allows for the micro-structuring of the gain medium [157][158][159] to enhance the gain, which is not readily available for ordinary lasers.…”

Three-dimensional, time-dependent analysis of high- and low-Q free-electron laser oscillators

“…Techniques well known from laser physics have also been applied to FEL oscillators either experimentally or in a conceptual study, such as injection seeding [141][142][143][144][145][146] and mode locking [125,142,143,147]. On the other hand, the unique nature of the gain process in FELs allows for micro structuring of the gain medium [148][149][150] to enhance the gain, which is not readily available for ordinary lasers.…”