Numerical Simulation Of Stable Free-electron Laser Oscillator Wavelength

Free-electron laser (hereby FEL) is produced by the interaction between the laser field and electrons. There are abundant nonlinear effects in this process and the wavelength of FEL can be easily changed by those effects. To stabilize the wavelength of FEL. in this paper, we modify the lD time-dependent FEL code, then use it to the Demo-IR FEL facility of Thomas Jefferson Lab for detailed studying the wavelength stabilization feedback system by the numerical simulation method. After our study, we got four new results. Firstly, it is feasible to use the wavelength stabilization feedback system to these high average power FELs. We can get stabilized wavelength lasers and the facilities can work stably. Secondly, the equivalent detuning caused by the electron energy changing has strong effects on the FEL. To some extend, it would destroy the interaction between the laser field and electrons and reduce the gain then let the FEL can not work. Thirdly, the effective time to add the wavelength stabilization feedback is the time when the FEL work steadily. Finally, the intrinsical feedback loop bandwidth does exist. We can successful achieve our aim only let the feedback loop bandwidth be around the intrinsical one. It is not necessary to pursue the ideal feedback loop bandwidth.