Use of quantum correlation for intensity noise reduction in semiconductor lasers

Abstract

The quantum correlation between junction voltage fluctuations1/frequency fluctuations2 and the intensity fluctuations of a semiconductor laser may be used to reduce the intensity noise. Here we address squeezed-state generation discussing both fundamental and practical limitations on noise reduction in conventional semiconductor lasers and microcavity lasers. In conventional semiconductor lasers, starting with intensity noise at the standard quantum limit, ideally a 3-dB amplitude squeezing is possible. This fundamental limit is set by spontaneous emission noise. Another fundamental limit is that noise reduction beyond the level set by optical losses and pump noise is not possible. It is also shown that the number-phase uncertainty in some conditions can reach the ultimate limit set by Heisenberg’s uncertainty principle. These conditions are clarified and a comparison made between junction voltage and frequency noise feedforward. Feedforward schemes realizing intensity noise reduction are discussed.