An optical horn structure for single-photon source using quantum dots at telecommunication wavelength

We succeeded in efficiently generating single-photon pulses from an InAs/InP quantum dot at a wavelength of 1.5 μm. Our optical structure, named a single photon horn, can propagate over 95% photon pulses in InP substrate. We extracted the photon pulses through an anti-reflection coating on a substrate, and then we injected them into an objective lens. Total extraction efficiency from the quantum dot to the lens reached ∼11%, which was estimated using a photon correlation measurement. Furthermore we directly observed the single-photon pulse width ∼1.6 ns as an exciton lifetime in the quantum dot, which opens up the possibility of operating the single photon horn over 100 MHz.