The performance of single photon sources based on single quantum dot emitters coupled to microcavities is analyzed with respect to different conditions of polarization. Electro-optic tuning is shown as a method to tune microcavities with distributed Bragg reflector mirrors into polarization degeneracy. Typically, for large cavity polarization splitting, excitation in the linearly polarized cavity modes is the only viable method for resonantly driving a single photon source. However, polarization degenerate cavities allow for arbitrary polarization conditions. A semi-classical model is used to analyze the performance of single photon sources under different polarization conditions. Further, the effect of residual cavity polarization splitting is analyzed under pulsed excitation.
Here we discuss the experimental characterization of the spatial far-field profiles for the confined modes in a
photonic crystal cavity of the L3 type, finding a good agreement with FDTD simulations. We then link the
far-field profiles to relevant features of the cavity mode near-fields, using a simple Fabry-Perot resonator model.
Finally, we describe a technique for independent all-electrical control of the wavelength of quantum dots in
separated L3 cavities, coupled by a waveguide, by electrical isolation via proton implantation
We describe quantum information schemes involving photon polarization and the spin of a single electron trapped
in a self-assembled quantum dot. Such schemes are based on spin-selective reflection in the weak-coupling regime
of cavity quantum electrodynamics. We discuss their practical implementation in oxide-apertured micropillar
cavities. We introduce a technique, based on the creation of small surface defects by means of a focused intense
laser beam, to permanently tune the optical properties of the microcavity without damaging the cavity quality.
This technique allows low-temperature polarization-selective tuning of the frequencies of the cavity modes and
the quantum dot optical transitions.
We study the influence of the mechanical deformation induced by a surface acoustic wave (SAW) on the resonance
frequency of a defect cavity in a 2D photonic crystal membrane. Using FDTD-simulations we determine the
resonance frequency and quality factor of a nanocavity of a GaAs based structure with embedded InAs quantum
dots. Under the influence of a SAW, we find a periodic modulation of the cavity resonance wavelength of Δλ >2
nm accompanied by only a weak < 0.5× reduction of the <i>Q</i>-factor. Initial experiments for a SAW wavelength of
~ 1.8μm show a pronounced broadening of the time-integrated cavity emission line corresponding to a shift of
≥ 1 nm.
Cavity quantum electrodynamic (QED) effects are studied in semiconductor microcavities embedded with InGaAs
quantum dots. Evidence of weak coupling in the form of lifetime enhancement (the Purcell effect) and inhibition is
found in both oxide-apertured micropillars and photonic crystals. In addition, high-efficiency, low-threshold lasing is
observed in the photonic crystal cavities where only 2-4 quantum dots exist within the cavity mode volume and are not
in general spectrally resonant. The transition to lasing in these soft turn-on devices is explored in a series of nanocavities
by observing the change in photon statistics of the cavity mode with increasing pump power near the threshold.
An oxide aperture is used to confine optical modes in a micropillar structure. This method overcomes the limitations due to sidewall scattering loss typical in semiconductor etched micropillars. High cavity quality factors (<i>Q</i>) up to 48 000 are determined by external Fabry-Perot cavity scanning measurements, a significantly higher value than prior work in III-V etched micropillars. Measured <i>Q</i> values and estimated mode volumes correspond to a maximum Purcell factor figure of merit value of 72. A Purcell Factor of 2.5 is experimentally observed from a single quantum dot emitter coupled to a high <i>Q</i> cavity mode.