Coexistence of thermal noise and squeezing in the intensity fluctuations of small laser diodes

The intensity fluctuations of laser light are derived from photon number ra te equations. In the Limit of short times, the photon statistics for small laser devices such as typical semiconductor laser diodes show thermal chara cteristics, even above threshold. In the limit of long-time averages repres ented by the low-frequency component of the noise, the same devices exhibit squeezing. It is shown that squeezing and thermal noise can coexist in the multimode output field of laser diodes. This result implies that the squee zed light generated by regularly pumped semiconductor laser diodes is quali tatively different from single-mode squeezed light. In particular, no entan glement between photons can be generated by use of this type of collective multimode squeezing. (C) 2000 Optical Society of America [S0740-3224(00)005 11-7].