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 rate equations. In the Limit of short times, the photon statistics for small laser devices such as typical semiconductor laser diodes show thermal characteristics, even above threshold. In the limit of long-time averages represented 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 squeezed light generated by regularly pumped semiconductor laser diodes is qualitatively different from single-mode squeezed light. In particular, no entanglement between photons can be generated by use of this type of collective multimode squeezing. (C) 2000 Optical Society of America [S0740-3224(00)00511-7].