If stimulated emission could be turned off then only uncorrelated photons
would be emitted from black bodies and the photon counting statistics would be
Poissonian. Through the process of stimulated emission, some fraction of the
photons emitted from a black body are correlated and thus emitted in clusters.
This photon clustering can be calculated by semi-classical means. The
corresponding results are in agreement with quantum theory.Comment: 10 pages, 2 figures, 1 table. Added proof that stimulated-emission
produced photon clustering at the source leads to the Hanbury Brown and Twiss
effect without invoking photon-photon interference. Fixed unit mistakes in
the left hand side of Eqs (4), (6), (7), and (9