Optical Properties of InAs/InP Planar Quantum Dot Microcavities

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E7.3.1

Optical Properties of InAs/InP Planar Quantum Dot Microcavities

Dan Dalacu, Daniel Poitras, Jacques Lefebvre, Philip J. Poole, Geoff C. Aers and Robin L. Williams. Institute for Microstructural Sciences, National Research Council, Ottawa, K1A 0R6, Canada

ABSTRACT Planar InAs/InP quantum dot microcavities using multi-layer SiO2/Ta2O5 Bragg reflectors have been studied in emission. The spectra exhibit collection optics-limited cavity linewidths of ~1meV with the occasional ~200µeV single-dot emission. Measurements as a function of incident power show quantum dot saturation behavior, with transfer of oscillator strength to the wetting layer outside the cavity stop band. Saturation behavior at fixed pump power is also observed as a function of decreasing temperature. Dispersion measurements as a function of emission angle show polarization splitting in qualitative agreement with theory.

INTRODUCTION Control of the light-matter interaction by placing a two-level electronic system into an optical cavity has been a topic of interest for some time [1]. From a semiconductor materials perspective, initial studies utilized quantum wells placed inside Fabry-Pérot cavities [2-5]. In such structures, the emission properties were influenced (enhanced / inhibited) by controlling the density of available optical modes. In addition to this weak coupling regime, where the emission characteristics are given by Fermi’s Golden rule, the strong coupling regime, where coherent energy transfer between the exciton and optical mode occurs, has also been observed [6]. More recently, efforts have been directed towards the placement of self-assembled quantum dots into various cavity geometries [7-14], with an emphasis on controlling the emission properties in the weak coupling regime. Although enhanced and inhibited spontaneous emission have been demonstrated, Rabi splitting in the optical emission spectra, indicative of strong coupling, has yet to be observed [15]. To optimize coupling between the photonic modes of a microcavity and the electronic levels of a quantum dot, it is important to be able to place the quantum dot at an anti-node of the electric field. To date, many studies in this area have utilized planar quantum dot samples, in which the self-assembled quantum dots are nucleated at random across the plane. Microcavity arrays are then constructed around these planar quantum dots with the hope that a small number of cavities can be found with a single quantum dot at an appropriate location within the cavity. As an alternative to this methodology we have begun an investigation of structures in which the quantum dots are nucleated at precisely chosen locations using patterned substrate growth techniques [16]. The microcavity can then be constructed around the quantum dot, so that coupling between the quantum dot and the optical mode can be optimized. In this paper we describe our preliminary experiments, which focus on the emission characteristics of InAs/InP dots in planar cavities utilizing multi-layer SiO2/Ta2O5 Bragg refl

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