Influence of the spontaneous optical emission factor β on the first-order coherence of a semiconductor microcavity laser

A systematic experimental and theoretical study of first-order coherence properties of high-β quantum-dot micropillar lasers is presented. A nonlinear increase in the coherence length is found in the transition regime from spontaneous to dominantly stimulated emission. This increase is accompanied by a qualitative change in the first-order field-correlation function g⁽¹⁾(τ) from a Gaussian-type profile to an exponential behavior, which is in excellent agreement with a microscopic semiconductor laser theory. Our results also demonstrate a decreasing coherence length with increasing spontaneous emission coupling β, thus raising questions about the practicability of high-β lasers for device applications.