Abstract
We investigate the switching of the coherent emission mode of a bimodal microcavity device, occurring when the pump power is varied. We compare experimental data to theoretical results and identify the underlying mechanism to be based on the competition between the effective gain on the one hand and the intermode kinetics on the other. When the pumping is ramped up, above a threshold the mode with the largest effective gain starts to emit coherent light, corresponding to lasing. In contrast, in the limit of strong pumping it is the intermode kinetics that determines which mode acquires a large occupation and shows coherent emission. We point out that this latter mechanism is akin to the equilibrium Bose-Einstein condensation of massive bosons. Thus, the mode switching in our microcavity device can be viewed as a minimal instance of Bose-Einstein condensation of photons. We, moreover, show that the switching from one cavity mode to the other occurs always via an intermediate phase where both modes are emitting coherent light and that it is associated with both superthermal intensity fluctuations and strong anticorrelations between both modes.
Highlights
The development of optical cavities [1,2,3,4] has led to devices with an almost vanishing lasing threshold [5,6]
We investigate the switching of the coherent emission mode of a bimodal microcavity device, occurring when the pump power is varied
We study the switching of the coherent emission mode in bimodal micropillar lasers occurring when the pump power is ramped up
Summary
The development of optical cavities [1,2,3,4] has led to (laser) devices with an almost vanishing lasing threshold [5,6]. The starting point for our theoretical description of a bimodal micropillar is a generic phenomenological master equation describing the relevant processes of the system [10,35]: the coupling between the pumped medium and the cavity modes, loss, and the intermode kinetics (Fig. 1) Such birth-death models have been used to study (analogs of Bose-Einstein condensation in) population dynamics [36,37], transport [38,39], and networks [40], as well as quantum gases of massive bosons [41,42]. In the situation where mode switching occurs, we find that the superthermal intensity fluctuations of the nonselected mode and strong anticorrelations occur whenever a mode starts or ceases to be selected We show that these experimentally observed statistical properties can be described theoretically by an effective reduction of the spontaneous intermode transitions caused by mode interactions.
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