Plug&Play Fiber‐Coupled 73 kHz Single‐Photon Source Operating in the Telecom O‐Band

Abstract

A user‐friendly, fiber‐coupled, single‐photon source operating at telecom wavelengths is a key component of photonic quantum networks providing long‐haul, ultra‐secure data exchange. To take full advantage of quantum‐mechanical data protection and to maximize the transmission rate and distance, a true quantum source providing single photons on demand is highly desirable. This great challenge is tackled by developing a ready‐to‐use semiconductor quantum‐dot‐based device that launches single photons at a wavelength of 1.3 µm directly into a single‐mode optical fiber. In the proposed approach, the quantum dot is deterministically integrated into a nanophotonic structure to ensure efficient on‐chip coupling into a fiber. The whole arrangement is integrated into a 19ʺ compatible housing to enable stand‐alone operation by cooling via a compact Stirling cryocooler. The realized source delivers single photons with a multiphoton events probability as low as 0.15 and a single‐photon emission rate of up to 73 kHz into a standard telecom single‐mode fiber.

Quantum Dot Single-Photon Emission Coupled into Single-Mode Fibers with 3D Printed Micro-Objectives

“…Very clean QD emission spectra are of particular interest for the use of the fibercoupled device in stand-alone applications, where for practical reasons, narrow fiber-coupled optical filters are used instead of bulky and expensive monochromators. 26 These filters have usually a higher bandwidth than the state of the art monochromators, which could increase multi-photon events.…”

“…In the past, multimode fibers 23 or SMF bundles 24 were used to realize the fiber-coupled single-photon sources. Only recent progress in nanofabrication techniques has paved the way for the single-modecoupling of semiconductor QDs integrated into Fabry-Perot optical microcavities, 25 cylindrical mesas, 26 photonic crystal nanobeams, 27 or waveguide-based devices. [28][29][30] In the present work, we take a different approach and want to combine the strength of the QDmicrolenses in terms of extraction efficiency 31 with the advantages of the precise and flexible 3D two-photon direct laser (TPL) patterning of photonic microstructures.…”

Thermal stability of emission from single InGaAs/GaAs quantum dots at the telecom O-band

“…Excitonic complexes in the QD were identified based on polarization-resolved and excitation-power-dependent µPL. The positive trion was found to be the thermally most stable excitonic complex, with its emission still visible at the temperature up to at least 80 K (liquid nitrogen accessible), and with single-photon emission purity of g (2) (0) = 0.13 at 50 K, what is particularly important in view of future applications due to applicability of cryogen-free cooling 23 , 24 . The positive trion emission intensity has a maximum around 30 K which is actually an ideal temperature when building a practical single-photon sources exploiting the Stirling cryocooling.…”

“…Reaching room temperature operation with QDs emitting at telecom wavelengths encounters fundamental limits of the quantum localization energy and inter-level spacing with the highest reported temperatures where the single-photon emission at telecom wavelengths is still observable at 120 K 35 . This is out of reach for thermoelectrical cooling, but on the contrary, the Stirling cryocooling can be successfully applied to reach temperatures as low as 27 K 23 , 24 and fulfils the requirements for compact, easy and relatively cheap operation without need for cryogenic liquids.…”

Photon-number squeezing in nano- and microlasers

“…Advanced nonlinear resonator concepts [19][20][21] now enable the realisation of interesting and flexible schemes which could find use in integrated devices. However, all previous schemes require rather complex experimental setups and recently interest is developing for sources where intensity noise can be reduced with simpler schemes 22,23 (and references therein). The device which we propose provides below-threshold squeezing and is based on a nanostructure.…”