Optical Loss and Lasing Characteristics of AlGaAs Microdisk Cavities with Embedded Quantum Dots

For future experiments in cavity QED with self-assembled quantum dots, the GaAs/AlGaAs system is the most appropriate choice of material, due to the relative maturity of the growth of InAs/InGaAs quantum dots [138, 139, 140] within this system. As the refractive index of GaAs and its alloys is relatively close to that of Si (n GaAs ∼ 3.5 and n AlAs ∼ 2.9 at λ ∼ 1.25 µm), the PC cavity design of chapter 2 remains applicable. Similarly, the high refractive index difference between GaAs/AlGaAs and air suggests that the radiation-limited Qs for microdisk cavities would be quite high for all but the smallest diameter disks. At the start of the work described in this chapter, what remained to be seen was whether the fabrication processes and material losses within this new system would be adequate to achieve a sufficiently high Q and small V eff for strong coupling experiments. Recently, multiple research groups have demonstrated vacuum Rabi splitting in a semiconductor system consisting of a single quantum dot (QD) exciton embedded in an optical microcavity [70, 71, 72]. These experiments have in many ways confirmed the potential of semiconductor microcavities for chip-based cavity quantum electrodynamics (cQED) experiments. For future experiments, such as those involving quantum state transfer in quantum networks [141], it will be important to further improve upon the parameters of such QD-microcavity systems over what was demonstrated in the above references. One clear improvement required is to move the system further within the regime of strong coupling. In particular, the ratio of g (the QD-photon coupling rate) to the larger of κ (the cavity decay rate) and γ ⊥ (the QD decay rate) approximately represents the number of Rabi