Photoluminescence Measurements of Quantum-Dot-Containing Microdisks Using Optical Fiber Tapers

The ability to efficiently couple light into and out of semiconductor microcavities is an important aspect of many microphotonic technologies [153], and plays a vital role in chip-based implementations of cavity quantum electrodynamics (cQED) for quantum networking and cryptography [60, 9, 154]. While some geometries, such as micropillar cavities, exhibit highly directional emission that can be effectively collected [16, 109], coupling to wavelength-scale semiconductor microcavities is in general non-trivial [120, 155, 156, 154], due to a number of factors. These include the size disparity between the modes of the microcavity and those of standard free-space and fiber optics, the refractive index difference between semiconductors and glass or air, and the potentially complicated cavity mode profiles sustained by these devices. In this thesis, we have presented evanescent coupling through optical fiber tapers as a way to couple efficiently to semiconductor microcavities. As we have already discussed, such fiber tapers have been used as near-ideal coupling channels for glass-to-glass coupling with silica-based microcavities such as microspheres [32, 157, 20, 55] and microtoroids [56]. In addition, as described in chapters 4 and 5, our recent experiments have indicated that they can also serve as efficient couplers to high-refractive index semiconductor-based devices, such as photonic crystal waveguides [39], photonic crystal cavities [52, 57] and microdisks [64, 69]. While the work described in the previous chapter primarily utilized fiber tapers for passive measurements such as the characterization of cavity quality factors, in this chapter, which is largely based on ref. [75], we focus on using the fiber taper as an efficient coupler for injecting pump light into and extracting the light emitted by semiconductor quantum dots into microdisk whispering gallery modes. The immediate device application that we study