FELIX free electron laser, image used with permission of FELIX facility.

UK Free Electron Laser Programme at FELIX

Prof Carl Pidgeon

Free electron lasers (FELs) represent a radical alternative to conventional lasers, being potentially the most flexible, high power and efficient generators of tunable coherent radiation from the ultra-violet to the infrared. A FEL does not have the restrictions of conventional lasers on operating wavelengths, and is constrained only by the phase-matching condition for strong interactions between the electrons and laser field - i.e. for a given periodic magnet (wiggler) structure, the wavelength is determined only by the energy of the electron beam and the strength of the magnetic field. The FEL has come of age and there are now ‘user facilities' in Europe and America. Professor B N Murdin (University of Surrey) and Professor C Pidgeon are in charge of the EPSRC funded UK research programme at the Dutch FEL (FELIX). In addition to its wide tuning range and high intensity, in time bandwith limited (ps) pulses, FELIX has coherent properties which we are now exploiting. Specifically we are studying the quantum optics of donors in Si through the coherent control of their Rydberg states. We have moved from studies of THz carrier dynamics utilising pump/probe semiconductor spectroscopy, to studies and utilization of coherence properties such as photon echoes, Rabii oscillations and Ramsey fringes; the ultimate objective is to achieve both ensemble and single donor quantum devices with relevance to, for example, quantum computing applications (analogous to the atoms in trap systems).