Quantum dot-based broadband optical antenna for efficient extraction of single photons in the telecom O-band

Abstract

Long-distance fiber-based quantum communication relies on efficient non-classical light sources operating at telecommunication wavelengths. Semiconductor quantum dots are promising candidates for on-demand generation of single photons and entangled photon pairs for such applications. However, their brightness is strongly limited due to total internal reflection at the semiconductor/vacuum interface. Here we overcome this limitation using a dielectric antenna structure. The non-classical light source consists of a gallium phosphide solid immersion lens in combination with a quantum dot nanomembrane emitting single photons in the telecom O-band. With this device, the photon extraction is strongly increased in a broad spectral range. A brightness of 17 % (numerical aperture of 0.6) is obtained experimentally, with a single photon purity of g ( 2 ) ( 0 ) = 0.049 ± 0.02 at saturation power. This brings the practical implementation of quantum communication networks one step closer.

Dual-resonance enhanced quantum light-matter interactions in deterministically coupled quantum-dot-micropillars

“…In such a case, the high-energy carriers are generated in the GaAs within the laser spot and then relax into the QDs with low-energy levels via the interactions with phonons. During the relaxation process, the carriers could be recaptured by the middle-energy level defect states, which results in a significant background for the second-order correlation 42 – 44 . We note that although the excitations via other high-order cavity modes with energy below the GaAs bandgap or wetting lay can also significantly suppress the carrier recapturing process, only the HBT result obtained under dual-resonance enhanced intra-dot excitation (excited from neutral exciton (913.4 nm)) shows nearly perfect suppression of background at zero delay, as presented in Fig.…”

Limits for quantum networks with semiconductor entangled photon sources

“…Here we show how the statistical distribution of QD properties limits their practical application in distributed quantum networks. Two separate dielectric antenna devices are studied, which have been reported to significantly enhance the photon extraction efficiency of QDs emitting at near-infrared [29] and telecom wavelengths [30]. The distribution of QD properties in the bare wafer and the changes induced by the device fabrication process are investigated.…”

Bright Purcell enhanced single-photon source in the telecom O-band based on a quantum dot in a circular Bragg grating

“…30 This allowed for the demonstration of entangled photon pair emission with high brightness and indistinguishability for GaAs QDs emitting around 780 nm 31 as well as In(Ga)As QDs at 900 nm. 32 However, for the telecom regime, most of the results have been demonstrated in the InAs/InP material system [33][34][35][36][37][38] with approaches in the InGaAs/GaAs material system being limited to etched microlenses and mesas, 39,40 dielectric antennas 41 and micropillars. 42 The feasibility of circular Bragg gratings in the telecom regime was suggested with simulations 43 as a promising approach, however, the realization of such a structure was still outstanding.…”