23 research outputs found
Design of broadband high-efficiency superconducting-nanowire single photon detectors
In this paper several designs to maximize the absorption efficiency of
superconducting-nanowire single-photon detectors are investigated. Using a
simple optical cavity consisting of a gold mirror and a SiO2 layer, the
absorption efficiency can be boosted to over 97%: this result is confirmed
experimentally by the realization of an NbTiN-based detector having an overall
system detection efficiency of 85% at 1.31 micrometers. Calculations show that
by sandwiching the nanowire between two dielectric Bragg reflectors, unity
absorption (> 99.9%) could be reached at the peak wavelength for optimized
structures. To achieve broadband high efficiency, a different approach is
considered: a waveguide-coupled detector. The calculations performed in this
work show that, by correctly dimensioning the waveguide and the nanowire,
polarization-insensitive detectors absorbing more than 95% of the injected
photons over a wavelength range of several hundred nm can be designed. We
propose a detector design making use of GaN/AlN waveguides, since these
materials allow lattice-matched epitaxial deposition of Nb(Ti)N films and are
transparent on a very wide wavelength range
Avalanche amplification of a single exciton in a semiconductor nanowire
Interfacing single photons and electrons is a crucial ingredient for sharing
quantum information between remote solid-state qubits. Semiconductor nanowires
offer the unique possibility to combine optical quantum dots with avalanche
photodiodes, thus enabling the conversion of an incoming single photon into a
macroscopic current for efficient electrical detection. Currently, millions of
excitation events are required to perform electrical read-out of an exciton
qubit state. Here we demonstrate multiplication of carriers from only a single
exciton generated in a quantum dot after tunneling into a nanowire avalanche
photodiode. Due to the large amplification of both electrons and holes (>
10^4), we reduce by four orders of magnitude the number of excitation events
required to electrically detect a single exciton generated in a quantum dot.
This work represents a significant step towards single-shot electrical read-out
and offers a new functionality for on-chip quantum information circuits
High absorption efficiency and polarization-insensitivity in superconducting-nanowire single-photon detectors
International audienceThe performance of superconducting-nanowire single-photon detectors depends on the efficiency of light absorption in the ultrathin (3-8 nm) superconducting nanowire. In this work, we will discuss two approaches to boost light absorption: coupling the nanowire to the evanescent field propagating in a waveguide and enclosing the nanowire in an optical cavity. The latter method is the most widely used, but it is intrinsically very sensitive to the polarization of light. To overcome this issue, we propose some innovative cavity designs which make use of high-index (n >2) dielectrics. With this technique, highly-efficient polarization-insensitive devices can be easily implemented
Ultraclean emission from InAsP quantum dots in defect-free wurtzite InP nanowires
We report on the ultraclean emission from single quantum dots embedded in pure wurtzite nanowires. Using a two-step growth process combining selective-area and vapor\u2013liquid\u2013solid epitaxy, we grow defect-free wurtzite InP nanowires with embedded InAsP quantum dots, which are clad to diameters sufficient for waveguiding at \u3bb 950 nm. The absence of nearby traps, at both the nanowire surface and along its length in the vicinity of the quantum dot, manifests in excitonic transitions of high spectral purity. Narrow emission line widths (30 \u3bceV) and very-pure single photon emission with a probability of multiphoton emission below 1% are achieved, both of which were not possible in previous work where stacking fault densities were significantly higher.Peer reviewed: YesNRC publication: Ye
Single-photon detectors combining high efficiency, high detection rates, and ultra-high timing resolution
Single-photon detection with high efficiency, high time resolution, low dark counts, and
high photon detection rates is crucial for a wide range of optical measurements. Although
efficient detectors have been reported before, combining all performance parameters in a
single device remains a challenge. Here, we show a broadband NbTiN superconducting
nanowire detector with an efficiency exceeding 92%, over 150 MHz photon detection rate,
and a dark count rate below 130 Hz operated in a Gifford-McMahon cryostat. Furthermore,
with careful optimization of the detector design and readout electronics, we reach an
ultra-low system timing jitter of 14.80 ps (13.95 ps decoupled) while maintaining high
detection efficiencies (>75%)