Free Electron Laser Gain with Harmonic Undulator Optical Klystron Scheme

In this paper, we discuss the harmonic undulator kl ystron free-electron laser to enhance the intensity and gain of a freeelectron laser. To incorporate this, we have introd uced a harmonic undulator field and compared the results with that of a standard optical klystron free-electron laser. With this method, we can easily control the modified fi eld and economically achieve higher harmonic free-electron laser gain.