Spatial quantum-interference landscapes of exciton polaritons with multi-site-controlled quantum dots in extended cavity modes

Abstract

Emission properties of quantum light source can be modified through tailored photonic cavities via Purcell effect or strong light-matter interactions with various applications in integrated quantum photonics. The interacting excitonic and photonic states are core elements in the framework of cavity quantum electrodynamics. Successful characterization of subwavelength features of photonic modes from photonic crystal cavities constitutes basic building blocks for engineering the quantum photonic circuits. Potential trapping of polaritonic states has made great progress towards realizing efficient polaritonic devices. However, spatially features of excitonic states are rarely explored because extended wavefunction of quantum well excitons in the conventional quantum well – distributed Bragg reflector cavity system cannot be spatially distinguished from the photonic states. In this work, interactions of site-controlled quantum dots with a high-order cavity mode of an L7-type photonic crystal cavity with extended photonic states are spatially- and spectrally-resolved. We observed the first detuning-dependent spatial avoided crossing of the exciton-polaritons by polarized-imaging of the microphotoluminescence. Interestingly, such phenomenon is observed to be dependent on the position of the quantum dot in the cavity, with our precise control of the four quantum dot sites in the microcavity. The observed effect arises due to a unique quantum interference feature and can facilitate a deeper understanding of the spatial extent of a localized strongly-coupled excitonic state interacting with an extended photonic mode pattern. Based on our results, incorporating site-controlled quantum dots at prescribed locations in a photonic structure with tailored spatial patterns of photonic states can enable new integrated photonic devices with functionalities such as single-photon transport to remote locations for quantum information processing, quantum engineering, and quantum metrology.