Quantum noise of laser diodes

Single-mode laser theory for semiconductor lasers predicts sub-Poissonian l ight generation for a laser quietly driven far above threshold. Experiments have shown however that only few laser diodes exhibits such reduced intens ity noise. We present a review of different mechanisms that have been propo sed to explain the excess noise observed in semiconductor lasers, including imperfect anticorrelations in multimode lasers, and Petermann excess noise factor in single-mode lasers.