Classical and quantum self amplified spontaneous emission in a high gain free electron laser

摘要

We describe the quantum theory and the photon statistics of self amplified spontaneous emission (SASE) in a high gain free electron laser (FEL) using Glanber's quantum theory of coherence. We generalize a previous theory by taking into account many-mode effects and the initiation process resulting from classical shot noise, quantum noise, an injected coherent field and coherent bunching. In particular, we define the concept of quantum SASE which is appropriate when the initial quantum fluctuations dominate over the classical shot noise. We also discuss the conditions for the observation. Quantum SASE is a new quantum phenomenon in which the single electron uncertainty flnctuations of the conjugate variables position and momentum produce exponential amplification of the vacuum field.