Observation of noise reduction in spatially coupled microchip lasers

We report on the observation of noise-correlated light beams emitted from a pair of spatially coupled microchip lasers. We study in particular, both experimentally and theoretically, the noise reduction induced in the intensity difference fluctuations, by examining the spectral density ratio between the difference and the sum of the two laser intensities in different frequency domains. The noise in the intensity difference is strongly reduced in the spectral domain of the relaxation oscillations of the coupled lasers. The agreement between experiment and the theoretical model findings is very good.