Shinnichi Hirose

Site-controlled photoluminescence at telecommunication wavelength from InAs∕InP quantum dots

We fabricated ordered InAs∕InP quantum-dot (QD) arrays using atomic-force-microscopic oxidation, wet etching, and regrowth by metalorganic chemical vapor deposition. The QDs exhibit single-dot photoluminescence peaking at wavelengths ranging from 1.22 to 1.45μm, mostly matching the telecommunication band of optical fibers. The site dependence of single peaks indicates the site controllability of single-dot light emitters, which might be useful in quantum information processing.

First Demonstration of Electrically Driven 1.55 µm Single-Photon Generator

We succeeded in demonstrating single-photon generation from a single InAs quantum dot (QD) at a 1.55 µm band by current injection. A p–i–n light-emitting diode (LED), which includes a quantum dot layer, was grown on an n-InP substrate and fabricated into a nano scaled mesa structure with electrodes. Electrical pulses of 80 ps width were injected in order to generate excitons in quantum dots. We directly determined the electroluminescence (EL) and radiative lifetime of a single exciton to be 1.59 ns. Hanbury-Brown and Twiss (HBT)-type photon correlation measurements proved the antibunching behavior of exciton recombination in a current-injected quantum dot at a wavelength of 1551.2 nm. These measurements demonstrate that our QD LEDs are sources of triggered single photons in the C-band by current injection.

Exciton dynamics in current-injected single quantum dot at 1.55μm

We investigate the exciton dynamics in a current-injected single InAs quantum dot (QD) which emits 1.55μm photons. Photon antibunching behavior is observed using a single electroluminescence line of a single QD. The radiative lifetime of this line determined by time-resolved measurement is 1.59ns. The single exciton recombination time agrees with the lifetime calculated with an eight-band kp model. We examine a high drive rate operation of the device by changing the delay time between two electrical pulses. These results demonstrate that our device has the potential to achieve telecommunication band subgigahertz single-photon emission with electrical pulses.

Sub-GHz operation of single-photon emitting diode at 1.55 μm

We demonstrated sub-GHz operation of a single-photon-emitting diode at 1.55 μm using 80-ps-wide electrical pulses. A light-emitting diode (LED) with a quantum dot (QD) layer was fabricated into a nanoscale mesa structure with electrodes. The electroluminescence (EL) and radiative lifetime of a single exciton in the QD was directly determined to be 1.59 ns by time-resolved EL measurement. The single-exciton recombination time agrees with the radiative lifetime calculated with an eight-band kp model. The antibunching behavior of exciton radiative recombination in a currentinjected quantum dot was demonstrated at 1551.2 nm by Hanbury-Brown and Twiss-type photon correlation measurements. Device examination at a high drive rate by changing the delay time between two electrical pulses demonstrated that a QD LED can be used as source of sub-GHz single photons in the C-band triggered by current injection.