Semiconductor optical microcavities for chip-based cavity QED.

摘要

Planar fabrication technology can be used to make optical structures that confine light to wavelength-scale dimensions, thereby creating strong enough electric fields that even a single photon can have an appreciable interaction with matter. When combined with the potential for integration and scalability inherent to chip-based microphotonics, these devices have enormous potential for future experiments in cavity QED and quantum networks.; This thesis is largely focused on the development of high quality factor (Q), small mode volume (Veff) semiconductor optical microcavities. In particular, we present work that addresses two major topics of relevance when trying to observe coherent quantum interactions within these systems: (1) the demonstration of low optical losses in a wavelength-scale microcavity, and (2) the development of an efficient optical channel through which the sub-micron-scale microcavity field can be accessed. The two microcavities of interest are planar photonic crystal defect resonators and microdisk resonators.; The first part of this thesis details the development of photonic crystal microcavities. A momentum space analysis is used to design structures that sustain high Qs and small Veffs and are relatively robust to imperfections. These designs are implemented in InP-based multi-quantum-well lasers and passive Si resonators. For the latter, optical fiber taper waveguides are used to couple light into and out of the cavities, and Qs of 4 x 104 are demonstrated for devices with Veff ∼ 0.9(lambda/ n)3.; In the second part of this thesis, we describe experiments in a GaAs/AlGaAs material containing self-assembled InAs quantum dots. Small diameter microdisks are fabricated with Q ∼ 3.6 x 105 and Veff ∼ 6(lambda/n) 3, and Q ∼ 1.2 x 105 and Veff ∼ 2(lambda/n)3. These devices are used to create room temperature, continuous-wave, optically-pumped lasers with thresholds of 1 muW of absorbed pump power. Fiber tapers are used to efficiently collect the emission, and a laser differential efficiency of 16 % is demonstrated. Furthermore, these microdisks have the requisite combination of high Q and small Veff to enable 'strong coupling', where the coupling rate between a single quantum dot and a single photon in the cavity exceeds the system decay rates. Quantum master equation simulations of the expected behavior of such fiber-coupled devices are presented, and progress towards cavity QED experiments is described.