Classical bunching contribution in the photon statistics of a high-gain FEL

In a previous paper we have calculated quantum mechanically the photon statistics of a high-gain FEL in the exponential SASE regime started only by the quantum fluctuations. In this paper we extend the previous calculation to include the effect of a properly defined “classical bunching” and the presence of many coherence lengths in the electron bunch. The new concept of Quantum SASE is defined.