Quantum electrodynamics in a laser and the electron laser collision

Quantum electrodynamics in a laser is formulated, in which the electron–laser interaction is exactly considered, while the interaction of an electron and a single photon is considered by perturbation. The formulation is applied to the electron–laser collisions. The effect of coherence between photons in the laser is therefore fully considered in these collisions. The possibility of γ-ray laser generation by use of this kind of collision is discussed.