We studied the performance of hot-electron bolometers (HEBs) operating at THz optical frequencies based on superconducting niobium nitride films. We report on large optical bandwidth measurement of the voltage response of the detector carried out with different THz sources. We show that the impulse response of the fully packaged HEB at 7.5 K has a 3 dB cut-off around 2 GHz, but a considerable detection capability is also observed above 30 GHz recorded in mixing mode operation by using a THz frequency comb quantum cascade laser
The quest to enlarge the capabilities of quantum information experiments based on non-classical states of light has directed the research toward an integrated approach. Thanks to integrated photonics circuits, photons can be efficiently generated, manipulated and detected within the same integrated chip. SNSPDs are the unique detectors that showed an integration compatibility with standard PICs. Nowadays the increasing complexity of integrated quantum optics experiments requires the manipulation of many modes and the simultaneous readout of an increasing number (N) of integrated detectors, thus posing new challenges regarding the simultaneous readout of different channels. In this presentation, we will discuss the advantages and drawbacks of our approach based on the amplitude multiplexing of N active pixels, each one consisting of a SNSPD with in parallel an on-chip AuPd resistor (Ri), to read (measure) simultaneously the output of several optical modes using only one coax cable.
KEYWORDS: Single photon detectors, Superconductors, Quantum communications, Quantum optics, Metrology, Signal to noise ratio, Photon counting, Nanowires, Current controlled current source
Superconducting nanowire single-photon detectors (SNSPDs) have shown to be promising in applications such as quantum communication and computation, quantum optics, imaging, metrology and sensing. They offer the advantages of a low dark count rate, high efficiency, a broadband response, a short time jitter, a high repetition rate, and no need for gated-mode operation. Several SNSPD designs have been proposed in literature. Here, we discuss the so-called parallel nanowires configurations. They were introduced with the aim of improving some SNSPD property like detection efficiency, speed, signal-to-noise ratio, or photon number resolution. Although apparently similar, the various parallel designs are not the same. There is no one design that can improve the mentioned properties all together. In fact, each design presents its own characteristics with specific advantages and drawbacks. In this work, we will discuss the various designs outlining peculiarities and possible improvements.
We will report our recent results using ultrathin NbN films (4-5 nm) for developing both conventional antenna-coupled hot-electron-bolometers (AC-HEBs) and of a novel type of phonon cooled HEB electrically-coupled to a metamaterial acting as a resonant absorber at THz frequencies (MM-HEB), optically-coupled through arrays of split ring resonators (metadevices). In a phonon-cooled HEB, being the active layer an ultrathin film of superconducting NbN, we have an ultrafast thermal direct detector that is also frequency selective thanks to the integration with the resonant metamaterial. We characterized both the AC-HEB and the MM-HEB by electro optical measurements using as a sources both the black body emission and terahertz quantum cascade lasers (THz-QCLs) and we compared their performances.
A Nth-order (N=1, 2, 3, 4, 5, 6) interferometric autocorrelator based on superconducting nanodetectors is presented. It provides much higher sensitivity as compared to the conventional autocorrelators using all-optical nonlinearities and a temporal resolution of about 20 ps, which is limited by the quasi-particle energy relaxation time in the superconducting films. A semiclassical model is introduced to explain the nonlinear photodetection process. A comparison of sensitivity to conventional autocorrelators is also presented.
We present our progress in the development of an integrated technology suitable for the photonic quantum information processing, showing the first autocorrelator based on two separated detectors integrated on top of the same ridge waveguide. An efficiency of ~1% at 1300 nm for both detectors and independent of the polarization of the incoming photons, is reported. This ultracompact device enables the on-chip measurement of the second-order correlation function g(2)(τ) . We will further discuss ongoing work on the integration of detectors with single-photon sources.
We report a novel component for integrated quantum photonic applications, a waveguide single-photon autocorrelator. It is based on two superconducting nanowire detectors patterned onto the same GaAs ridge waveguide. Combining the electrical output of the two detectors in a correlation card enables the measurement of the second-order correlation function g(2) (τ), which realizes the functionality of a Hanbury-Brown and Twiss experiment in a very compact integrated device. Each detector shows a polarization-independent quantum efficiency of ~0.5-1% at 1300 nm. This autocorrelator represents a key building block for quantum photonic integrated circuits including single-photon sources and linear optics.
We present a novel configuration for a photon number resolving detector based on a series array of shunted
superconducting nanowires, which has the potential to provide a high dynamic range. The first prototype of the detector
consisting of four series elements is demonstrated with the ability to resolve up to four photons in an incident optical
pulse at the telecommunication wavelength window.
The implementation of single-photon detectors in waveguide photonic circuits will open the possibility of experiments in
quantum regime that would otherwise be impossible to be implemented using bulk optics. Nanowire superconducting
single-photon detectors (SSPDs) are good candidates for integration due to their relative ease of fabrication on top of
GaAs heterostructures. In this paper we show the experimental demonstration of single-photon detectors, based on
superconducting nanowires, fully integrated with GaAs/AlGaAs ridge waveguides. We will discuss all the major
challenges surmounted and all the steps necessary to achieve these results.
KEYWORDS: Inductance, Switches, Superconductors, Single photon detectors, Sensors, Signal to noise ratio, Switching, Solids, Scanning electron microscopy, Nanowires
Ultrathin NbN nanowires is the material of choice for superconducting single photon detectors (SSPD) due to the good
efficiency, dark count rate and timing jitter at 1550 nm wavelength obtained. These performance parameters are achieved
using nanowires a few nanometers thick and 100 nm wide patterned into a meander shape in order to achieve area
coverage. The meander shape effectively makes the SSPD of a single very long nanowire in turn giving it a significant
inductance which limits the maximum count rate of the detector. Recently, we demonstrated how one can exploit a
cascade switch to the normal state of nanowires connected in parallel to significantly reduce the SSPD inductance and
increase the signal amplitude. Here we present how one can configure SSPDs that uses multiple cascade switches to the
normal state. We show how this principle can be used to expand the SSPD coverage area with a very limited increase in
detector inductance with area. Finally we discuss our first results obtained with SSPD based on the multiple cascade
switch principle, showing correct operation.
KEYWORDS: Switches, Inductance, Superconductors, Sensors, Photodetectors, Single photon detectors, Signal to noise ratio, Signal processing, Electron beam lithography, Nanowires
Ultrathin NbN nanowires is the material of choice for superconducting single photon detectors (SSPD) due to the good
efficiency, dark count rate and timing jitter at 1550 nm wavelength obtained. These performance parameters are achieved
using nanowires a few nanometers thick and 100 nm wide patterned into a meander shape in order to achieve area
coverage. The meander shape effectively makes the SSPD of a single very long nanowire in turn giving it a significant
inductance which limits the maximum count rate of the detector. Recently, we demonstrated how one can exploit a
cascade switch to the normal state of nanowires connected in parallel to significantly reduce the SSPD inductance and
increase the signal amplitude. Here we present how one can configure SSPDs that uses multiple cascade switches to the
normal state. We show how this principle can be used to expand the SSPD coverage area with a very limited increase in
detector inductance with area. Finally we discuss our first results obtained with SSPD based on the multiple cascade
switch principle, showing correct operation, increased operational bias range and increased signal pulse amplitudes.
We present a novel concept of photon number resolving detector based on 120-nm-wide superconducting stripes made of
4-nm-thick NbN film and connected in parallel (PNR-SSPD). The detector consisting of 5 strips demonstrate a capability
to resolve up to 4 photons absorbed simultaneously with the single-photon quantum efficiency of 2.5% and negligibly
low dark count rate.
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