Accelerator Seminar:
- Accelerator Seminar:https://misportal.jlab.org/ul/calendar/show_single_event.cfm?id=5890ARC 231/2332020-03-02EST19:00:0012886
Seminar Speaker: Prof. Ying Wu, Duke University
ABSTRACTPhoton beams with special phase structures, known as optical vortices, generated using conventional lasers have been studied and explored for more than two decades. In these optical vortices, photons carry both spin and orbital angular momentum (OAM). Such OAM optical beams have a wide range of applications in both fundamental and applied sciences, from atomic physics to quantum information to optical communication. The Free-Electron Laser (FEL) is uniquely positioned to extend the generation of OAM photon beams to short-wavelength regions such as VUV, EUV, and X-ray, creating new and exciting research opportunities.
Coherent vortices have been successfully generated with several schemes using a single-pass FEL. This work reports the first experimental demonstration of the coherent vortice generation using an oscillator FEL. With the storage ring FEL at Duke University, we have established fundamental harmonic FEL lasing in the visible wavelength in a variety of coherently mixed OAM modes, with photons in the |l> and |-l> superposition states (l = 1, 2, 3, 4) and with each eigenstate carrying lh OAM. Observed as Laguerre Gaussian modes, stable FEL lasing of the OAM beams has been achieved with reasonable power. These beams have been measured and characterized using specially developed optical techniques. The operation of such an OAM FEL paves the way for the generation of OAM gamma-ray beams via Compton scattering. The opportunity offered by OAM gamma-ray beams in nuclear physics research is promising, but remains unexplored experimentally.
This work is partially supported by U.S. DOE Grant: DE-FG02-97ER41033.