Free Electron Laser Undulator Based on Grating Structure (Invited)

Free electron laser light source is a new type of coherent light source. It has many advantages such as wide wavelength range, pure spectrum, high power and so on. It has significant application requirements in biology, materials, medicine and other fields. Therefore, since the invention of free electron laser theory in the 1970s, free electron laser technology has been developed rapidly. The principle of free electron laser is to make use of electron beam oscillation in periodic electromagnetic field to produce electromagnetic radiation. By controlling the oscillation period, the magnetic radiation light forms coherent radiation. The undulator is a key technical component of free electron laser, which is used to generate the periodic electromagnetic field that oscillates the electron beam. At present, the undulator is usually composed of magnets, and uses magnetic field to realize deflection oscillation of electron beam, coupling the energy of electron beam to the laser field. In 1988, researchers at the Institute of High Energy Physics of the Chinese Academy of Sciences proposed a free electron laser scheme based on ferroelectrics generating transverse deflecting electric fields. Nearly 30 years, laser technology and processing technology have obtained fast development, leading to a series of micro accelerator innovation, with many new accelerators constantly emerging, such as metal surface laser accelerators and medium- sized laser accelerators, and a large number of researchers around the world constantly promoting micro accelerator technology forward. Inspired by lateral deflection field free electron laser solutions, and benefit from the development of laser, micro-nano technology in recent years, this paper puts forward a kind of miniature undulator, based on the structure of grating with femtosecond laser pulses irradiation grating. The periodic transverse deflection electric field is formed on the surface of the grating, and the high energy electron beam is modulated by the periodic electric field, which generates periodic oscillation and radiates coherent electromagnetic wave to form a gain of free electron laser. In this paper, the free electron laser vibrator with grating structure is theoretically analyzed, the trajectory equation of electron beam is given, and the electric field simulation of the structure is carried out to obtain the transverse electric field distribution on the surface of the grating. Finally, a 10 MeV electron beam with 10 mA intensity is tracked, and the laser gain is calculated.