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Physical Review A

Synchronization-induced noise reduction in spatially coupled microchip lasers

Carles Serrat, M. C. Torrent, Jordi García‐Ojalvo, Ramon A. Vilaseca

Published Sep 12, 2001• 13 citations
Publisher

Abstract

We investigate theoretically the intensity and phase correlations in the quantum-noise-driven dynamics of two spatially coupled microchip lasers. These correlations induce noise reduction phenomena for which simple analytic expressions are derived. We predict a complete suppression of the dominant relaxation oscillation peaks in the intensity difference noise spectrum, as well as photon statistics approaching the standard quantum limit. The correlations and consequent noise reduction effects are robust against frequency detuning and persist for pump powers well above threshold.

DOI
10.1103/physreva.64.041802

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We investigate theoretically the intensity and phase correlations in the quantum-noise-driven dynamics of two spatially coupled microchip lasers. These correlations induce noise reduction phenomena for which simple analytic expressions are derived. We predict a complete suppression of the dominant relaxation oscillation peaks in the intensity difference noise spectrum, as well as photon statistics approaching the standard quantum limit. The correlations and consequent noise reduction effects are robust against frequency detuning and persist for pump powers well above threshold.
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We consider the quantum dynamics of a pair of coupled quantum oscillators coupled to a common correlated dissipative environment. The resulting equations of motion for both the operator moments and covariances can be integrated analytically using the Lyapunov equations. We find that for fully correlated and fully anti-correlated environments, the oscillators relax into a phase-synchronized state that persists for long-times when the two oscillators are nearly resonant and (essentially) forever if the two oscillators are in resonance. We identify an exceptional point that indicates the onset of broken symmetry between an unsynchronized and synchronized dynamical phase of the system as correlations within the environment are increased. We also show that the environmental noise correlation leads to quantum entanglement, and all the correlations between the two oscillators are purely quantum mechanical in origin. This work provides a robust mathematical foundation for understanding how long-lived exciton coherences can be linked to vibronic correlation effects.
We study in detail the influence of pumping statistics on the laser dynamics. We apply the technique of quantum Langevin operators and generalize the corresponding noise operators to incorporate the statistical properties of the pump mechanism. These equations are then used to derive expressions for the phase and intensity fluctuations of lasers with various pump statistics. We find that a reduction of pump noise can lead to a significant squeezing of the photon number noise below the shot-noise limit. This is in complete agreement with our previous analysis, which used a density-operator approach.
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