Mollow triplets under few-photon excitation

Abstract

Resonant excitation is an essential tool in the development of semiconductor quantum dots (QDs) for quantum information processing. One central challenge is to enable transparent access to the QD signal without post-selection information loss. A viable path is through cavity enhancement, which has successfully lifted the resonantly scattered field strength over the laser background under weak excitation. Here, we extend this success to the saturation regime using a QD-micropillar device with a Purcell factor of 10.9 and ultra-low background cavity reflectivity of just 0.0089±0.0001. We achieve a signal to background ratio of 55 and overall system responsivity of 3.01±0.08%, i.e., we detect on average 0.03 resonantly scattered single photons for every incident laser photon. Raising the excitation to the few-photon level, the QD response is brought into saturation where we observe Mollow triplets as well as the associated cascaded single photon emissions, without resorting to any laser background rejection technique. Our work offers a perspective on a QD cavity interface that is not restricted by the laser background.