M. Reischle

Electrically pumped single-photon emission in the visible spectral range up to 80 K

We present an electrically pumped single-photon emitter in the visible spectral range, working up to 80 K, realized using a self-assembled single InP quantum dot. We confirm that the electroluminescense is emitted from a single quantum dot by performing second-order autocorrelation measurements and show that the deviation from perfect single-photon emission is entirely related to detector limitations and background signal. Emission from both neutral and charged exciton complexes was observed with their relative intensites depending on the injection current and temperature.

Triggered single-photon emission from electrically excited quantum dots in the red spectral range

Pulsed electrical excitation was used to excite single InP/Ga0.51In0.49P quantum dots and obtain triggered single-photon emission in the red spectral range at an excitation repetition rate of up to 200 MHz. Increased repetition rates are prevented by the finite decay-time, and autocorrelation measurements look similar to what is expected for dc injection above 1 GHz. Finally, it is shown that negative voltage pulses can increase the decay-rate considerably such that 1 GHz excitation rates should be possible.

Room-temperature lasing of electrically pumped red-emitting InP/(Al0.20Ga0.80)0.51In0.49P quantum dots embedded in a vertical microcavity

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.

Red single-photon emission from an InP∕GaInP quantum dot embedded in a planar monolithic microcavity

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 130μeV at 5K 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 1.5MHz (8.1MHz into the first lens, with an extraction efficiency of 4.1%) were observed.

Influence of the oxide aperture radius on the mode spectra of (Al,Ga)As vertical microcavities with electrically excited InP quantum dots

In this letter, we report about mode characteristics of microcavity lasers with red-emitting InP quantum dots. The mode spectra and the quality factor of devices with different oxide aperture sizes are analyzed. The lateral mode confinement in the electrical devices is defined via oxide apertures. We found a good agreement between a simple analytical modeling of the mode structure and measurements, which allows to adjust the design of future devices. The quality factors show an analogous behavior as etched micropillars. The enhanced intensity of the higher order modes compared to the fundamental mode can be explained with the current density distribution within the device favoring higher order modes.

InP‐quantum dots in Al0.20Ga0.80InP with different barrier configurations

Systematic ensemble photoluminescence studies have been performed on type-I InP-quantum dots in Al 0.20 Ga 0.80 InP barriers, emitting at approximately 1.85 eV at 5 K. The influence of different barrier configurations as well as the incorporation of additional tunnel barriers on the optical properties has been investigated. The confinement energy between the dot barrier and the surrounding barrier layers, which is the sum of the band discontinuities for the valence and the conduction bands, was chosen to be approximately 190 meV by using Al 0.50 Ga 0.50 InP. In combination with 2 nm thick AllnP tunnel barriers, the internal quantum efficiency of these barrier configurations can be increased by up to a factor of 20 at elevated temperatures with respect to quantum dots without such layers. Ensemble-transient (inset) and temperature dependent decay times of InP-QDs in Al 0.20 GaInP-barriers with surrounding Al 0.50 GaInP layers and AlInP tunnel barriers (sketch). formula graph.

Photons on demand from an electrically driven single quantum dot under pulsed excitation

For a single quantum dot under excitation with short electrical pulses the dependence of the photon anti-bunching on pulse width and excitation strength is studied in a theory-experiment collaboration.

High-frequency electrically driven quantum dot single-photon source

Compact and efficient single-photon sources are key components for several future applications, e.g in quantum cryptography, random number generators, and for a future standard of optical brightness. To date, commercial single-photon detectors provide highest sensitivity in the red spectral range and single-photon based technologies such as quantum communication benefit from their low detector dark count rates. Thus, the red spectral range is suited for free space communication or via polymer optical fibers in last mile networks.

High‐frequency Triggered Single—Photon Emission From Electrically Driven InP/(Al,Ga)InP Quantum Dots

We used sub‐nanosecond electrical pulses to excite single InP/GaInP quantum dots to realize triggered single‐photon emission in the red spectral range. The electroluminescence of different quantum dots was investigated and the successful injection of short voltage pulses was verified by time—resolved and autocorrelation measurements.

Electrically pumped single‐photon emission up to 80 K—Towards a commercial single‐photon emitting device

We report electically pumped single‐photon emission in the visible spectral range up to 80 K using InP quantum dots embedded in AlGaInP barriers. In order to confirm that the emission is from a single quantum dot we performed second‐order autocorrelation measurements and observed strong antibunching at zero time delay. Deviations from a perfect single‐photon emitter could be explained by detector limitations and background signal.