Bleuse, J.

Claudon, J.

Dalga, A.

Gregersen, Niels

Gérard, J. M.

Munsch, M.

Mørk, Jesper

Within the emerging field of optical quantum information processing, the current challenge is to construct the basic building blocks for the quantum computing and communication systems. A key component is the singlephoton source (SPS) capable of emitting single photons on demand. Ideally, the SPS must feature near-unity efficiency, where the efficiency is defined as the number of detected photons per trigger, the probability g(2)(τ=0) of multi-photon emission events should be 0 and the emitted photons are required to be indistinguishable. An optically or electrically triggered quantum light emitter, e.g. a nitrogen-vacancy center or a semiconductor quantum dot (QD), embedded in a solid-state semiconductor host material appears as an attractive platform for generating such single photons. However, for a QD in bulk material, the large index contrast at the semiconductor-air interface leads to a collection efficiency of only 1-2 %, and efficient light extraction thus poses a major challenge in SPS engineering. Initial efforts to improve the efficiency have exploited cavity quantum electrodynamics (cQED) to efficiently couple the emitted photons to the optical cavity mode. An alternative approach based on QDs in a photonic nanowire (Fig. 1a) was recently proposed, and the first experimental demonstration featured an efficiency of 0.72. [1] This geometry does not employ a cavity but instead relies on a geometrical screening effect to efficiently couple the emitted photons to the optical mode of interest. [2] The photonic nanowire “trumpet” design based on an inverted taper and compatible with metal contacts, shown in Fig. 1(b), very recently resulted in an efficiency of 0.75 under optical pumping. [3] These designs do not employ a cavity and do not rely on resonant cQED effects to ensure a high  factor, meaning that efficient coupling from the QD to the guided mode is obtained over a broad spectral range of ~ 50-100 nm. [4] This means that spectral alignment between the emitter line and a narrow cavity line is not required, which represents a huge practical advantage in the fabrication. Furthermore, for a given dot density, the smaller area of the nanowire QD layer compared to that of e.g. micropillars means that fewer dots are present, and very pure photon emission with a measured g(2)(τ=0) as low as 0.008 [1] has been obtained.</p

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Downloaded from orbit.dtu.dk on: Dec 19, 2017Highly efficient photonic nanowire single-photon sources for quantum informationapplicationsGregersen, Niels; Claudon, J.; Munsch, M.; Bleuse, J.; Dalga, A.; Mørk, Jesper; Gérard, J. M.Published in:Single Photon Workshop 2013Publication date:2013Link back to DTU OrbitCitation (APA):Gregersen, N., Claudon, J., Munsch, M., Bleuse, J., Dalga, A., Mørk, J., & Gérard, J. M. (2013). Highly efficientphotonic nanowire single-photon sources for quantum information applications. In Single Photon Workshop 2013(pp. 76)  Highly efficient photonic nanowire single-photon sources  for quantum information applications N. Gregersen1, J. Claudon2, M. Munsch2, J. Bleuse2, A. Delga2, J. Mørk1 and J. M. Gérard2 1DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark  Kongens Lyngby, Denmark 2CEA-CNRS-UJF Joint Group ‘Nanophysique et SemiConducteurs’ CEA, INAC, SP2M Grenoble, France ngre@fotonik.dtu.dk  Within the emerging field of optical quantum information processing, the current challenge is to construct the basic building blocks for the quantum computing and communication systems. A key component is the single-photon source (SPS) capable of emitting single photons on demand. Ideally, the SPS must feature near-unity efficiency, where the efficiency is defined as the number of detected photons per trigger, the probability g(2)(=0) of multi-photon emission events should be 0 and the emitted photons are required to be indistinguishable. An optically or electrically triggered quantum light emitter, e.g. a nitrogen-vacancy center or a semiconductor quantum dot (QD), embedded in a solid-state semiconductor host material appears as an attractive platform for generating such single photons. However, for a QD in  bulk material, the large index contrast at the semiconductor-air interface leads to a collection efficiency of only 1-2 %, and efficient light extraction thus poses a major challenge in SPS engineering. Initial efforts to improve the efficiency have exploited cavity quantum electrodynamics (cQED) to efficiently couple the emitted photons to the optical cavity mode. An alternative approach based on QDs in a photonic nanowire (Fig. 1a) was recently proposed, and the first experimental demonstration featured an efficiency of 0.72. [1] This geometry does not employ a cavity but instead relies on a geometrical screening effect to efficiently couple the emitted photons to the optical mode of interest. [2] The photonic nanowire “trumpet” design based on an inverted taper and compatible with metal contacts, shown in Fig. 1(b), very recently resulted in an efficiency of 0.75 under optical pumping. [3] These designs do not employ a cavity and do not rely on resonant cQED effects to ensure a high  factor, meaning that efficient coupling from the QD to the guided mode is obtained over a broad spectral range of ~ 50-100 nm. [4] This means that spectral alignment between the emitter line and a narrow cavity line is not required, which represents a huge practical advantage in the fabrication. Furthermore, for a given dot density, the smaller area of the nanowire QD layer compared to that of e.g. micropillars means that fewer dots are present, and very pure photon emission with a measured g(2)(=0) as low as 0.008 [1] has been obtained.    Fig. 1. Schematics and scanning electron micrographs of photonic nanowire single-photon sources  based on a regular (a) and an inverted (b) conical tapering.  This research is conducted within the EURAMET joint research project SIQUTE [5] which receives funding from the European Community's Seventh Framework Programme, ERA-NET Plus, under Grant Agreement No. 912/2009/EC. References [1] J. Claudon et al., “A highly efficient single-photon source based on a quantum dot in a photonic nanowire,” Nat. Photonics 4, 174-177 (2010). [2] J. Claudon, N. Gregersen, P. Lalanne and J. M. Gérard, “Harnessing Light with Photonic Nanowires: Fundamentals and Applications to Quantum Optics,” Chem. Phys. Chem. 14, 2393-2402 (2013). [3] M. Munsch et al., "Dielectric GaAs Antenna Ensuring an Efficient Broadband Coupling between an InAs Quantum Dot and a Gaussian Optical Beam," Phys. Rev. Lett. 110, 177402 (2013). [4] N. Gregersen, P. Kaer and J. Mørk, "Modeling and Design of High-Efficiency Single-Photon Sources," IEEE J. Sel. Top. Quantum Electron. 19, 9000516 (2013). [5] http://www.ptb.de/emrp/siqute-home.html 

Highly efficient photonic nanowire single-photon sources for quantum information applications

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Highly efficient photonic nanowire single-photon sources for quantum information applications

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