Low Dimensional Polariton Systmes in Subwavelength-Grating Based Microcavities.

Abstract

Semiconductor microcavity exciton-polaritons have recently emerged as a unique, open system for studying non-equilibrium quantum order. Macroscopic quantum phenomenon, Bose-Einstein condensation, has been realized and observed in two dimensional polariton systems utilizing the traditional distributed-Bragg-reflector based samples. Such foundational work on two-dimensional systems has inspired theoretical schemes for polariton-based quantum circuits, quantum light sources and novel quantum phases. Experimental implementation of these schemes requires the control, confinement and coupling of polariton systems, which still remain challenging in conventional microcavity structures. In this thesis, we use the sub-wavelength grating-based microcavities to demonstrate confinement and coupling for the polariton systems.

We demonstrated a zero-dimensional polariton device in the sub-wavelength grating-based microcavity. Efficient confinement has been realized in such unconventional microcavity. These confinement features have also been observed in the spectroscopic characterization with discretized energy levels from the device. In addition, the polaritons are highly linear polarized, which is unique to the sub-wavelength grating based devices. The establishment of the polariton lasing/condensation was with non-linear increase of the emission intensity, line-width narrowing and continuous energy shift. Single-mode lasing of polaritons was also demonstrated for the first time.

Following the work of single zero-dimensional polariton device, we demonstrated that the coupling among multiple zero-dimensional polariton quantum devices could be readily achieved, leading to de-coupled, coupled and quasi-one-dimensional polariton systems. These coupling effects were controlled and realized by design of the tethering patterns around the sub-wavelength grating based devices. Such devices enable advanced mode engineering and provide the building blocks for polariton-based quantum simulator and quantum circuits.