We show that the reduction in photon-number fluctuations at laser threshold often cited as a fundamental laser property does not occur in small semiconductor lasers. The conventional theory of threshold noise is not valid in lasers with a spontaneous emission factor larger than ${10}^{-8}.$ If the spontaneous-emission factor is larger than ${10}^{-4},$ the photon-number statistics even remain thermal far above threshold. We therefore conclude that the reduction in photon-number fluctuations is not a fundamental laser property but rather a matter of size and the corresponding relative importance of quantum fluctuations above threshold.

• Received 22 October 1998

DOI:https://doi.org/10.1103/PhysRevA.62.063807