Light control and microcavity lasers based on quantum wires integrated in photonic-crystal cavities

Novel light-emitting devices and micro-optical-circuit elements will rely upon understanding and control of light-matter interaction at the nanoscale. Recent advances in nanofabrication and micro-processing make it possible to develop integrable solid-state structures where the optical- and quantum-confinement effects determine the density and distribution of the energy states, allowing for mastering the output characteristics. In semiconductor nanostructures, such as quantum wires or quantum dots (sometimes referred even to as "artificial atoms") produced by epitaxy, with characteristic dimensions of 10÷20 nm, the quantization determines light absorbtion and emission spectra. Unlike the bulk matter, these important properties depend on the size and shape of the object, which is designed by nanotechnology. In photonic crystals and photonic-crystal micro-resonators, on the other hand, due to pronounced bandgap effects acting on light, unprecedented control over reflectivity, transmission and such a fundamental quantum-mechanical property as the density of electromagnetic vacuum-field fluctuations is achieved, the latter defining the rates of spontaneous emission of an embedded source. Based on these ideas, a number of passive and active optical and optoelectronic devices is anticipated practically, in particular, semiconductor microlasers with extremely low threshold pump-powers and ultimate conversion efficiency. Within the framework of this thesis we successfully integrated site-controlled quantum wires (QWRs) in 2D photonic-crystal (PhC) microcavities, examined the basic spectral and dynamics properties of the system, implemented the QWRs as a testing light source and probed interesting cavity configurations, and finally achieved stimulated emission and lasing. Starting from the previous studies of the QWR nanostructures, we, first, designed the geometry patterns adapted for implementation in the PhC-cavity system. Crystal growth (by metal-organic vapor-phase epitaxy) of InGaAs/GaAs QWRs on such patterns was verified; single and triple vertically stacked identical wires were obtained integrated within a 260-nm thin GaAs membrane. The basic properties of such QWRs were checked by photoluminescence spectroscopy. Spectra, power-dependent blueshift and temperature dependence consistent with previous studies were evidenced. Relatively long radiative lifetimes were found (at low – 20K – temperature) in transient spectroscopy, suggesting exciton localization effects and the effective dimensionality in between 0D and 1D. Identified as the most practically feasible way of exploiting the PhC bandgap effects for achieving high-Q truly single-mode resonators, the membrane approach in 2D photonic crystals was then implemented. In our nanofabrication effort we succeeded in incorporating the QWRs into such PhC cavities with very good site-control. The site control is apparently crucial, as light-matter coupling in an optical cavity and the spontaneous-emissio