Soft-X-Ray Confined-Electron Laser

Arya Fallahi, Niels Kuster, and Lukas Novotny, Phys. Rev. A, Volume 107, Issue 6, Article No. L061504, online 28 June 2023; doi: 10.1103/PhysRevA.107.L061504

Illustration of a confined electron laser

 

A confined electron laser is a “wiggled” electron beam confined by the ponderomotive forces inside an electromagnetic cavity. The ponderomotive forces counteract the beam expansion due to space-charge forces, thereby enabling lasing at low energies. In this Letter, we show the possibility of lasing at a wavelength of approximately 4 nm in the soft-X-ray regime. We simulate various cavity parameters and show that electron-beam confinement and, consequently, the initiation of the lasing process are independent of the cavity resonance wavelength. We also show that ponderomotive confinement can compensate for the beam divergence due to nonzero emittance, thereby enabling lasing with large emittance values for which the free-electron lasing condition is violated. Our results support the feasibility of a few femtosecond, compact, and coherent soft-X-ray source.

The scientific and technical impact of the study can be summarized as:

• The findings demonstrate the possibility of a confined electron laser to radiate coherent light in the soft x-ray regime
• The simulations demonstrate that the wavelength of the confining light does not play a significant role in the overall performance of the confined electron laser
• Most importantly, the results indicate that a confined electron laser is not limited to the lasing condition required for electron-beam emittance in free-electron lasers