TUD01
FEL/Duke University, Durham, North Carolina, USA
JLab, Newport News, Virginia, USA
Coherent vortices have been generated with several schemes using a single-pass FEL. This work reports the first experimental demonstration of coherent vortice generation using an oscillator FEL. With the storage ring FEL at Duke University, we have established fundamental harmonic FEL lasing in a variety of coherently mixed orbital angular momentum (OAM) modes, with photons in the |l> and |-l> superposition states (l = 1, 2, 3) and with each eigenstate carrying lh OAM. Spatially organized in Laguerre Gaussian modes, stable FEL lasing of these OAM beams has been achieved with reasonable power. Optical techniques have been developed to characterize these beams. The operation of such an OAM FEL paves the way for the generation of OAM gamma-ray beams via Compton scattering.
