A. Lyasota

Exciton dynamics in a site-controlled quantum dot coupled to a photonic crystal cavity

Exciton and cavity mode (CM) dynamics in site-controlled pyramidal quantum dots (QDs), integrated with linear photonic crystal membrane cavities, are investigated for a range of temperatures and photo-excitation power levels. The absence of spurious multi-excitonic effects, normally observed in similar structures based on self-assembled QDs, permits the observation of effects intrinsic to two-level systems embedded in a solid state matrix and interacting with optical cavity modes. The coupled exciton and CM dynamics follow the same trend, indicating that the CM is fed only by the exciton transition. The Purcell reduction of the QD and CM decay times is reproduced well by a theoretical model that includes exciton linewidth broadening and temperature dependent non-radiative processes, from which we extract a Purcell factor of 17 ± 5. For excitation powers above QD saturation, we show the influence of quantum wire barrier states at short delay time, and demonstrate the absence of multiexcitonic background emission.

Effect of Pure Dephasing and Phonon Scattering on the Coupling of Semiconductor Quantum Dots to Optical Cavities

We investigate the effect of decoherence mechanisms in semiconductor quantum dot-cavity systems by performing photoluminescence measurements of InGaAs/GaAs site-controlled quantum dots coupled to photonic crystal cavities and comparing the results to a theoretical model.

Propagation losses in photonic crystal waveguides: effects of band tail absorption and waveguide dispersion

Propagation losses in GaAs-based photonic crystal (PhC) waveguides are evaluated near the semiconductor band-edge by measuring the finesse of corresponding L-n cavities. This approach yields simultaneously the propagation losses and the mode reflectivity at the terminations of the cavities. We demonstrate that the propagation losses are dominated by band tail absorption for shorter wavelengths and by fabrication disorder related scattering, near the photonic band edge, for longer wavelengths. Strategies for minimizing losses in such elongated cavities and waveguides are discussed, which is important for the monolithic integration of light sources with such optical elements

Deterministic coupling of a system of multiple quantum dots to a single photonic cavity mode

We fabricated and studied a system comprising four site-controlled semiconductor quantum dots (QDs) embedded in a linear photonic crystal membrane cavity. The excellent position control and small spectral broadening permit coupling of the emission of all four QDs to the same photonic cavity modes. This is corroborated by co-polarization of the QD and cavity emission lines, as well as reduction in decay time, both with characteristic dependence on QD-cavity energy detuning. Scaling up to larger QD systems is discussed.

Probing disorder and mode localization in photonic crystal cavities using site-controlled quantum dots

The impact of optical disorder on photon propagation in long Ln photonic crystal cavities is investigated using spectrally resolved imaging, group index measurements, and selective mode excitation with site-controlled quantum dots. Mobility and diffusive edges, separating localized, diffusive, and dispersive regimes, are consistently identified. In situ probing of the photonic modes demonstrates the low impact of disorder in the dispersive regime and the transition to phase-distorted modes in the diffusive regime. The analysis yields criteria for designing photonic crystal waveguides for efficient single photon transport.

Single photon extraction and propagation in photonic crystal waveguides incorporating site-controlled quantum dots

Deterministic integration of site-controlled quantum dots with photonic crystal waveguides is demonstrated, which allows positioning the dots for optimal overlap with the waveguide modes. The coupling efficiency (β-factor) of quantum dot emission to propagating waveguide modes ranging from 0 to 88% is measured accounting for statistical variations of quantum dot properties. Using site controlled quantum dots permits us to distinguish between the spectral and spatial origins of fluctuations in β. The role of Fabry-Perot modes that prevent reaching a deterministic coupling between quantum dots and photonic crystal waveguides is revealed, and ways to overcome this problem are proposed. The results are useful for constructing high-flux single photon emitters based on multiplexed single photon sources.

Site-controlled quantum dots coupled to photonic crystal cavities and waveguides

We investigate the optical coupling of excitons confined in site-controlled semiconductor quantum dots (QDs) with the modes of photonic crystal (PhC) cavities membrane cavities and waveguides. The structures are fabricated by organometallic vapor phase epitaxy of InGaAs/GaAs heterostructures on patterned (111)B GaAs substrates combined with electron-beam-based nanolithography. We elucidate the role of pure dephasing and phonon interaction on the weak exciton-cavity mode coupling, and demonstrate the simultaneous coupling of several QDs to the same optical mode of various PhC cavity configurations. In addition, coupling of QD systems to PhC waveguides for implementing single photon transport in the face of optical disorder is studied. Implications on the potential of constructing integrated quantum photonic circuits for on-chip manipulation of quantum light will be discussed.

Effect of pure dephasing and phonon scattering on the coupling of semiconductor quantum dots to optical cavities

We investigate the effect of decoherence mechanisms in semiconductor quantum dot-cavity systems by performing photoluminescence measurements of InGaAs/GaAs site-controlled quantum dots coupled to photonic crystal cavities and comparing the results to a theoretical model.