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We demonstrate a novel method to measure Nth-order (N=1,2,3,4) interferometric autocorrelation with high sensitivity and temporal resolution. It is based on the combination of linear absorption and nonlinear detection in a superconducting nanodetector, providing much higher efficiency than methods based on all-optical nonlinearities. Its temporal resolution is only limited by the quasiparticle energy relaxation time, which is directly measured to be in the 20 ps range for the NbN films used in this work. We present a general model of interferometric autocorrelation with these nonlinear detectors and discuss the comparison with other approaches and possible improvements. [ABSTRACT FROM AUTHOR]

A novel light-emitting-diode structure is demonstrated, which relies on nanoscale current injection through an oxide aperture to achieve selective excitation of single InAs/GaAs quantum dots. Low-temperature electroluminescence spectra evidence discrete narrow lines around 1300 nm (line width ≈ 75 μeV) at ultralow currents, which are assigned to the emission from single excitons and multiexcitons. This approach, which enables the fabrication of efficient nanoscale active devices at 1300 nm, can provide single-photon-emitting diodes for fiber-based quantum cryptography. [ABSTRACT FROM AUTHOR]

We report a systematic study of the In-assisted deoxidation (IAD) of epitaxial GaAs(100) substrates. Optimized IAD conditions resulting in a pit-free and smooth GaAs surface are found. Photoluminescence lines from single quantum dots (QDs) with linewidths in the range of 250–400 μeV are observed from low-density InAs QDs grown at a distance of 10 nm from a GaAs surface deoxidized under an optimized condition. Our study shows that IAD is very promising for application in the growth of nanostructures on patterned GaAs substrates. [ABSTRACT FROM AUTHOR]

In recent years, photon-number-resolving (PNR) detectors have attracted great interest, mainly because they can play a key role in diverse application fields. A PNR detector with a large dynamic range would represent an ideal photon detector, bringing the linear response of conventional analogue detectors down to the single-photon level. Several technologies, such as InGaAs single photon avalanche detectors (SPADs), arrays of silicon photomultipliers, InGaAs SPADs with self-differencing circuits and transition edge sensors have shown photon number resolving capability. Superconducting nanowires provide free-running single-photon sensitivity from visible to mid-infrared frequencies, low dark counts, excellent timing resolution (<60 ps) and short dead time (∼10 ns), at an easily accessible temperature (2–3 K), but they do not inherently resolve the photon number. In this framework, PNR detectors based on arrays of superconducting nanowires have been proposed. In this article we describe a number of methods and device configurations that have been pursued to obtain PNR capability using superconducting nanowire detectors. [ABSTRACT FROM AUTHOR]

We report a systematic study of the In-assisted deoxidation (IAD) of epitaxial GaAs(100) substrates. Optimized IAD conditions resulting in a pit-free and smooth GaAs surface are found. Photoluminescence lines from single quantum dots (QDs) with linewidths in the range of 250–400 μeV are observed from low-density InAs QDs grown at a distance of 10 nm from a GaAs surface deoxidized under an optimized condition. Our study shows that IAD is very promising for application in the growth of nanostructures on patterned GaAs substrates. [ABSTRACT FROM AUTHOR]

A very promising way to increase the detection efficiency of nanowire superconducting single-photon detectors (SSPDs) consists in integrating them with advanced optical structures such as distributed Bragg reflectors (DBRs) and optical waveguides. This requires transferring the challenging SSPD technology from the usual substrates, i.e. sapphire and MgO, to an optical substrate like GaAs, on which DBRs and waveguides can be easily obtained. Therefore, we optimized the deposition process of few-nm thick superconducting NbN films on GaAs and AlAs/GaAs-based DBRs at low temperatures (substrate temperature TS = 400 degC), in order to prevent As evaporation. NbN films ranging from 150 to 3 nm in thickness were then deposited on single-crystal MgO, GaAs, MgO-buffered GaAs and DBRs by current-controlled DC magnetron sputtering (planar, circular, balanced configuration) of Nb in an Ar+N2 plasma. 5.5 nm thick NbN films on GaAs exhibit TC = 10.7 K, DTC = 1.1 K and RRR = 0.7. The growth of such high quality thin NbN films on GaAs and DBRs has never been reported before. [ABSTRACT FROM AUTHOR]