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We report on in-lab free space quantum key distribution (QKD) experiments over 40 cm distance using highly efficient electrically driven quantum dot single-photon sources emitting in the red as well as near-infrared spectral range. In the case of infrared emitting devices, we achieve sifted key rates of 27.2 kbit s-1(35.4 kbit s-1) at a quantum bit error rate (QBER) of 3.9% (3.8%) and a g(2)(0) value of 0.35 (0.49) at moderate (high) excitation. The red emitting diodes generate sifted keys at a rate of 95.0 kbit s-1 at a QBER of 4.1% and a g(2)(0) value of 0.49. This first successful proof of principle QKD experiment based on electrically operated semiconductor single-photon sources can be considered as a major step toward practical and efficient quantum cryptography scenarios. [ABSTRACT FROM AUTHOR]

We present a method to reduce the intrinsically high InP quantum dot density embedded in a Ga0.51In0.49P barrier by introducing an InGaAs quantum dot seed layer. The additional strain reduces the total InP quantum dot density by around one order of magnitude from 2×1010 to 3×109 cm-2 but only ∼1% of the InP nanostructures seem to be optically active (107 cm-2). Therefore, microphotoluminescence measurements could be accomplished without masks. We found resolution-limited photoluminescence linewidths (ΔE<100 μeV), good signal-to-noise ratios (∼65), single-photon emission behavior [g(2)(τ=0)=0.3], and excitonic decay times of typically between 1 and 2 ns. Furthermore the structural quantum dot properties were investigated. [ABSTRACT FROM AUTHOR]

We demonstrate electrically pumped laser light emission in the visible (red) spectral range using self-assembled InP quantum dots embedded in a microcavity mesa realized by monolithically grown high-reflectivity AlGaAs distributed Bragg reflectors. We used common semiconductor laser processing steps to fabricate stand-alone index-guided vertical-cavity surface-emitting lasers with oxide apertures for optical wave-guiding and electrical current constriction. Ultra-low threshold of around 10 A/cm2 and room temperature lasing were demonstrated. Additionally, the temperature independence of the threshold current, which was predicted in theory for quantum dot lasers, is displayed. [ABSTRACT FROM AUTHOR]

Using micro-photoluminescence, we demonstrate single-photon emission in the visible (red) spectral range using self-assembled InP quantum dots embedded in a planar microcavity realized by monolithically grown high reflectivity AlGaAs distributed Bragg reflectors. A full width at half maximum of 130 μeV at 5 K was observed from a single quantum dot coupled to the fundamental cavity resonance. Photon correlation measurements performed under continuous wave excitation show a clear antibunching behavior [g(2)(0)=0.13] as expected for a single-photon emitter. Saturation count rates up to 1.5 MHz (8.1 MHz into the first lens, with an extraction efficiency of 4.1%) were observed. [ABSTRACT FROM AUTHOR]

Within this contribution, results for a laser structure consisting of InP quantum dots embedded in an (AlxGa1-x)0.51In0.49P matrix lattice matched to GaAs are presented. The structure was fabricated using metal–organic vapor-phase epitaxy, showing electrically pulsed laser operation at room temperature with a low threshold current density of 870 A/cm2 and a lasing wavelength of 638 nm for a 2000 µm long device with uncoated facets. Optical output powers of more than 55 mW per facet and lasing up to 313 K is demonstrated. [ABSTRACT FROM AUTHOR]