Strong light-matter coupling in the presence of lasing

Abstract

The regime of strong light-matter coupling is typically associated with weak excitation. With current realizations of cavity-QED systems, strong coupling may persevere even at elevated excitation levels sufficient to cross the threshold to lasing. In the presence of stimulated emission, the vacuumRabi doublet in the emission spectrum is modified and the established criterion for strong coupling no longer applies. We provide a generalized criterion for strong coupling and the corresponding emission spectrum, which includes the influence of higher Jaynes-Cummings states. The applicability is demonstrated in a theory-experiment comparison of a few-emitter quantum-dot-micropillar laser as a particular realization of the driven dissipative Jaynes-Cummings model. Furthermore, we address the question if and for which parameters true single-emitter lasing can be achieved, and provide evidence for the coexistence of strong coupling and lasing in our system in the presence of background emitter contributions.

Controlling the gain contribution of background emitters in few-quantum-dot microlasers

“…This proves that only a single QD is feeding the cavity as intended. However, this single QD does not provide enough gain to drive the system into lasing as shown also previously for similar system [10]. This has important consequences for the interpretation of figure 3(b) in the main text.…”

“…The gain medium consists of a single layer of self-assembled InGaAs QDs, with an Indium content of about 40% and an areal density of -10 cm 10 2 in the center of a GaAs λ-cavity. These QDs feature a large oscillator strength, which in combination with the low mode-volume micropillar ensures pronounced light-matter interaction that facilitates reaching the strong coupling regime [24] with pronounced single QD lasing effects [10]. On top (bottom) of the central GaAs cavity 26 (30) pairs of AlAs/GaAs layers acting as high reflective distributed Bragg reflectors (DBR) were grown.…”

“…In this context, a better understanding of the influence of individual in-and off-resonant QDs on the lasing behavior is needed and will be crucial for the design and operation of future micro-and nano-lasers. This information is also an important contribution to the ongoing very active discussion in the semiconductor community about the possibility for a single QD to provide enough gain to initiate and sustain lasing [10,[29][30][31][32][33]. Interestingly, and in spite of their central role, the influence of offresonantly coupled QDs on the lasing behavior has not been described in a controlled and comprehensive way so far.…”

“…So far, self-assembled QDs in semiconductor microcavities feature the highest optical quality in terms of oscillator strength, quantum efficiency and coherence properties [8], giving a chance to eventually approach the single-emitter lasing regime. However, in the presently available QD-cavity systems non-negligible gain contribution by non-resonant transitions is still necessary to overcome the laser threshold [5,9,10]. To better control the coupling behavior and the gain contribution of a single resonant emitter, integrating a single self-assembled QD into a high-quality microcavity will be interesting in further optimizations.…”

“…Even for a spontaneous emission factor (β-factor) close to unity, in which case spontaneous emission of the resonant emitter is almost solely directed into the laser mode, the light-matter coupling rate has to overcome the cavity loss rate at least by a factor of two [21]. In practice, it requires to combine cavities with a high quality factor (Q) and strong light-matter interaction, leading towards the coherent strong coupling regime [10,22]. In this case the required high Q-factor microresonators with small mode volumes foster the illumination of the cavity mode by off-resonant QDs [23,24] which in turn has significant impact on the transition to lasing.…”