We compute the statistics of thermal emission from systems in which the radiation is scattered chaotically, by relating the photocount distribution to the scattering matrix—whose statistical properties are known from random-matrix theory. We find that the super-Poissonian noise is that of a blackbody with a reduced number of degrees of freedom. The general theory is applied to a disordered slab and to a chaotic cavity, and is extended to include amplifying as well as absorbing systems. We predict an excess noise of amplified spontaneous emission in a random laser below the laser threshold.

• Received 28 January 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.1829