Amplitude squeezing of a multiple quantum-well distributed-feedback semiconductor laser operating at room temperature—Effect of reduction of spontaneous-emission noise by Interferometric method

We demonstrate 3.4-dB amplitude squeezing of a multiple quantum-well distributed-feedback semiconductor laser operating at room temperature. The spontaneous-emission noise is eliminated by using a Michelson interferometer, where the intensity noise due to spontaneous emission is cancelled by the intensity noise converted from the frequency noise. The spectral density of the remaining noise is 3.4 dB below the shot-noise level, which is limited by the differential quantum efficiency of the laser.