In a photonic free-electron laser (pFEL), the longitudinal periodicity of a photonic structure is used to slow down the phase velocity of an electromagnetic (EM) wave, such that it moves synchronously with a copropagating electron beam. The interaction of the EM wave with the electrons results in bunching of the electrons and consequently coherent amplification of the EM wave.
The photonic structure is chosen to allow multiple electron beams to propagate through the structure. The transverse periodicity of the photonic crystal results in the establishment of a single transversely coherent EM wave (the transverse scattering allows the electron beams to ‘communicate’ with each other through the EM wave, so that they become phase locked). The output power of such an device can be scaled by increasing the number of electron beams propagating in parallel and simultaneously increasing the transverse dimension of the photonic crystal.
In this research program, we investigate various aspects of this novel type of laser.