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Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection

The ability to perform simultaneous resonant excitation and fluorescence detection is important for quantum optical measurements of quantum dots (QDs). ...

West Virginia University

Using resonance fluorescence, we investigate how acoustic phonons mediate couplings between multiple electronic levels in a semiconductor quantum dot. We show the first direct evidence of population up-conversion in a single quantum dot, which we attribute to absorption of single acoustic phonons. Moreover, through a rate equation analysis, we find that below 20 K such single-phonon mediated couplings between the exciton ground state and the first excited state are primarily responsible for decoherence of the exciton quantum state.

Direct evidence of interlevel exciton transitions mediated by single phonons in a semiconductor quantum dot using resonance fluorescence spectroscopy.

We demonstrate and characterize interference between discrete photons emitted by two separate semiconductor quantum dot states in different samples excited by a pulsed laser. Their energies are tuned into resonance using strain. The photons have a total coalescence probability of 18.1% and the coincidence rate is below the classical limit. Postselection of coincidences within a narrow time window increases the coalescence probability to 47%. The probabilities are reduced from unity because of dephasing and the postselection value is also reduced by the detector time response.

Interference of single photons from two separate semiconductor quantum dots.

Ultralow-loss concave micromirrors with radius of curvature below 60 microm were fabricated by laser ablation and reflective coatings. A 10-microm-long microcavity with a mode volume of 40 microm(3) was set up with two such mirrors, and the cavity linewidth was measured both spectrally and temporally. The smallest linewidth obtained was 96 MHz, corresponding to a quality factor of 3.3x10(6) and a finesse in excess of 1.5x10(5). With these parameters, we estimate that a variety of solid-state quantum emitters coupled to the cavity may enter the strong coupling regime.

Ultrahigh-finesse, low-mode-volume Fabry-Perot microcavity.

Single photons produced by fundamentally dissimilar physical processes will in general not be indistinguishable. We show how photons produced from a quantum dot and by parametric down-conversion in a nonlinear crystal can be manipulated to be indistinguishable. The measured two-photon coalescence probability is 16%, and is limited by quantum-dot decoherence. Temporal filtering to the quantum-dot coherence time and accounting for detector time response increases this to 61% while retaining 25% of the events. This technique can connect different elements in a scalable quantum network.

Coalescence of single photons emitted by disparate single-photon sources: the example of InAs quantum dots and parametric down-conversion sources.

We measure the dynamics of a nonclassical optical field using two-time second-order correlations in conjunction with pulsed excitation. The technique quantifies single-photon purity and coherence during the excitation-decay cycle of an emitter, illustrated here using a quantum dot. We observe that for certain pump wavelengths, photons detected early in the cycle have reduced single-photon purity and coherence compared to those detected later. A model indicates that the single-photon purity dynamics are due to exciton recapture after initial emission and within the same pulse cycle.

Dynamics of nonclassical light from a single solid-state quantum emitter.

Resonant photoluminescence excitation (RPLE) spectra of a neutral InGaAs quantum dot show unconventional line shapes that depend on the detection polarization. We characterize this phenomenon by performing polarization-dependent RPLE measurements and simulating the measured spectra with a three-level quantum model. The spectra are explained by interference between fields coherently scattered from the two fine structure split exciton states, and the measurements enable extraction of the steady-state coherence between the two exciton states.

Edward B. Flagg

Department of Physics and Astronomy

West Virginia University

Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection

Edward B. Flagg

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Physics and Astronomy

West Virginia University

Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection

Department of Physics and Astronomy