COLLECTIVE RESONANT COMPTON-SCATTERING BY 2-LEVEL PARTICLES

In this paper we provide a simple analytical demonstration that an unb unched beam of two-level particles coherently driven by a quasi-resona nt counterpropagating field can give rise to coherent Compton back sca ttering due to self bunching which occurs via an instability very simi lar to that of a high gain Free Electron Laser. Since the initially we ak scattering light is exponentially amplified and is Doppler upshifte d in frequency, this effect constitutes the basic physical principle o f a tunable source of coherent radiation: the Collective Atomic Recoil Laser (CARL). CARL extends the FEL bunching concept to any system of particles having two internal energy levels.