There is an increasing demand for superconducting nanowire single photon detectors (SNSPDs) which combine high efficiency, low dark counts and fast response time. They play a crucial role in developing strategic application areas such as photon-based quantum computing and quantum key distribution. We demonstrate the fabrication of high crystalline quality NbN-based waveguide-integrated SNSPDs using a completely CMOS-compatible process on 200 mm SOI wafers. We achieve a detection efficiency over 80 % at 100 Hz dark count rate, a short decay time below 4 ns and a maximum count rate of 200 MHz.
We experimentally demonstrate phase encoding in SHG with transparent all-dielectric metasurfaces. While a similar task was previously achieved with plasmonic metasurfaces for THG beam shaping, here we obtain three-order-of-magnitude higher generation efficiency without thermal dissipation.
Tapered nanowire antennas have emerged as a versatile solid-state platform for quantum optics. These broadband photonic structures efficiently funnel the spontaneous emission of an embedded quantum dot into a directive free-space beam. They find application in the realization of bright sources of quantum light, and enable the implementation of giant optical non-linearities, at the single-photon level.
In this work, we discuss advances aiming at further optimizing this light-matter interface. In particular, recent measurements revealed that the thermal excitation of a single nanowire vibration mode can have a sizeable influence on the quantum dot optical linewidth. This motivated a comprehensive theoretical analysis, which shows that the thermally-driven vibrations of the nanowire have a major impact on the quantum dot light emission spectrum. Even at liquid helium temperatures, these prevent the emission of indistinguishable photons. To overcome this intrinsic limitation, we propose several designs that restore photon indistinguishability thanks to a specific engineering of the mechanical properties of the nanowire. We anticipate that such a mechanical optimization will also play a key role in the development of other high-performance light-matter interfaces based on nanostructures.
We demonstrate photon-pair generation via spontaneous parametric down-conversion (SPDC) from two types of metasurfaces composed by AlGaAs nanocylinders: 1) monolithically fabricated on a selectively oxidized layer of AlAs epitaxially grown on a GaAs wafer; 2) fabricated by reporting the AlGaAs nanostructures on a transparent wafer via wafer bonding. In these samples, we observed SPDC both in back- and forward-scattering configurations, under excitation with a CW pump around 775 nm and single-photon detection on the signal and idler channels. The Bragg modulation of Mie-resonances enables paraxial SPDC, which demonstrates the potential of all-dielectric metasurfaces for quantum applications like on-axis quantum imaging.
The 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.
The ability to control the temporal shape of single-photon pulses is highly desirable in quantum information processing. For instance, it has been shown that Gaussian pulses are best suited for linear optics quantum computing1. By mimicking the time-reversal of a spontaneous emission event, it also allows to optimize the absorption of the prepared photons by a quantum emitter. In this work we investigate the potential of using fast modifications of the detuning between an atomic system and a cavity mode during photon emission to reach this goal. We compare two approaches consisting of varying the emitter or cavity frequency. The latter, achievable by a fast modification of the refractive index of a solid state cavity, will be shown to have negligible influence on the photon spectrum. It allows to create Gaussian pulses interacting with a fidelity to the target photons of 99%, as well as time-reversed photons absorbed by an atom in a cavity with a probability of 93%.
Efficient coupling between a localized quantum emitter and a well defined optical channel represents a powerful route to
realize single-photon sources and spin-photon interfaces. The tailored fiber-like photonic nanowire embedding a single
quantum dot has recently demonstrated an appealing potential. However, the device requires a delicate, sharp needle-like
taper with performance sensitive to minute geometrical details. To overcome this limitation we demonstrate the photonic
trumpet, exploiting an opposite tapering strategy. The trumpet features a strongly Gaussian far-field emission. A first
implementation of this strategy has lead to an ultra-bright single-photon source with a first-lens external efficiency of
0.75 ± 0.1 and a predicted coupling to a Gaussian beam of 0.61 ± 0.08.
Photonic wires have recently demonstrated very attractive assets in the field of high-efficiency single photon sources. After presenting the basics of spontaneous emission control in photonic wires, we compare the two possible tapering strategies that can be applied to their output end so as to tailor their radiation diagram in the far-field. We highlight the novel “photonic trumpet” geometry, which provides a clean Gaussian beam, and is much less sensitive to fabrication imperfections than the more common needle-like taper geometry. S4Ps based on a single QD in a PW with integrated bottom mirror and tapered tip display jointly a record-high efficiency (0.75±0.1 photon per pulse) and excellent single photon purity. Beyond single photon sources, photonic wires and trumpets appear as a very attractive resource for solid-state quantum optics experiments.
Efficient coupling between a localized quantum emitter and a well defined optical channel represents a powerful route to realize single-photon sources and spin-photon interfaces. The tailored fiber-like photonic nanowire embedding a single quantum dot has recently demonstrated an appealing potential. However, the device requires a delicate, sharp needle-like taper with performance sensitive to minute geometrical details. To overcome this limitation we demonstrate the photonic trumpet, exploiting an opposite tapering strategy. The trumpet features a strongly Gaussian far-field emission. A first implementation of this strategy has lead to an ultra-bright single-photon source with a first-lens external efficiency of 0.75 ± 0.1 and a predicted coupling to a Gaussian beam of 0.61 ± 0.08.
We report on the design, fabrication and optical investigation of AlGaAs microcavities for THz Difference Frequency
Generation (DFG) between Whispering Gallery Modes (WGMs), where the pump and DFG wavelengths (λ ≈ 1.3 μm and λ ≈ 75-150 μm, respectively) lie on opposite sides of the Restrahlen band. For the pump modes, we demonstrate CW lasing of quantum-dot layers under electrical injection at room temperature. We control the number of lasing WGMs via vertical notches on the pillars sidewalls, providing a selection mechanism for funneling the power only to the modes contributing to DFG. In parallel with the optimization of the pump lasers and in order to validate design and material parameters before the DFG experiments, we have performed linear measurements on two sets of passive samples. For the telecom range, the micropillars have been integrated with waveguides for distributed coupling and characterized via transmission measurements. In the THz range we have measured reflectivity spectra on 2D arrays of identical cylinders. In both cases, we demonstrate a good agreement between experimental results and simulations. On a more speculative note, we numerically show that etching a hole along the pillar axis can facilitate phase matching, while single-lobe farfield pattern can be obtained for the THz mode by micro-structuring the metallic ground plane around the microcavity. Finally, we suggest a real-time fine-tuning mechanism for the forthcoming active devices.
Besides microcavities and photonic crystals, photonic nanowires have recently emerged as a novel resource for solidstate
quantum optics. We will review recent studies which demonstrate an excellent control over the spontaneous
emission of InAs quantum dots (QDs) embedded in single-mode GaAs photonic wires. On the basic side, we have
demonstrated a strong inhibition (x 1/16) of QD SpE in thin wires (d<λ/2n), a nearly perfect coupling of the SpE to the
guided mode (β>0.95 for d~λ/n), and polarization control in elliptical nanowires. A single QD in a photonic wire is thus
an attractive system to explore the physics of the "one-dimensional atom" and build novel quantum optoelectronic
devices. Quite amazingly, this approach has for instance permitted (unlike microcavity-based approaches) to combine for
the first time a record-high efficiency (72%) and a negligible g(2) in a QD single photon source.
We discuss the generation of THz radiation at room temperature by the exploitation of a nonlinear optical process taking
place in a high quality factor AlGaAs microcavity. The approach is grounded on 1) a novel quasi-phase-matching
scheme for parametric processes involving whispering-gallery modes circulating in nonlinear microcylinders; and 2)
recent advances concerning quantum dots microcylindrical lasers. After a brief summary of the theory used to describe
the nonlinear process, we present the results of our modeling in the case of a passive device pumped by two lasers at
wavelengths close to 1.3 μm. Finally, we conclude with preliminary measurements performed with a tapered fiber.
We propose a new electrically-pumped single-photon source design based on a quantum dot in a photonic nanowire. For
realistic parameters, the design features an efficiency of 89 % predicted by numerical simulations. Unlike cavity-based
designs, our approach allows for broadband spontaneous emission control and has high tolerance towards surface
roughness. In the nanowire, a geometrical effect ensures good coupling between the quantum dot and the optical mode,
and an inverted tapering section is introduced to adiabatically expand the mode waist and control the far field emission
profile while minimizing the relative modal overlap with the metal contacts.
In this article, we report our results on 1.3&mgr;m VCSELs for optical interconnection applications. Room
temperature continuous-wave lasing operation is demonstrated for top emitting oxide-confined devices with three
different active materials, highly strained InGaAs/GaAs(A) and GaInNAs/GaAs (B) multiple quantum wells (MQW) or
InAs/GaAs (C) quantum dots (QD). Conventional epitaxial structures grown respectively by Metal Organic Vapour
Phase Epitaxy (MOVPE), Molecular Beam Epitaxy (MBE) and MBE, contain fully doped GaAs/AlGaAs DBRs. All
three epilayers are processed in the same way. Current and optical confinement are realized by selective wet oxidation.
Circular apertures from 2 (micron)m to 16 (micron)m diameters are defined.
At room temperature and in continuous wave operation, all three systems exhibit lasing operation at
wavelengths above 1 275nm and reached 1 300nm for material (A). Typical threshold currents are in the range [1-
10]mA and are strongly dependent firstly on oxide diameter and secondly on temperature. Room temperature cw
maximum output power corresponds respectively to 1.77mW, 0.5mW and 0.6mW. By increasing driving current,
multimode operation occurs at different level depending on the oxide diameter. In case (A), non conventional modal
behaviors will be presented and explained by the presence of specific oxide modes.
Thermal behaviors of the different devices have been compared. In case (A) and (C) we obtain a negative T0.
We will conclude on the different active materials in terms of performances with respect to 1300nm VCSEL
applications.
In the context of optical interconnection applications, we report on results obtained on strained InGaAs quantum well Vertical Cavity Surface Emitting Lasers (VCSELs). Our devices are top p-type DBR oxide-confined VCSEL, grown by metalorganic vapour-phase epitaxy (MOVPE). These lasers exhibit low threshold currents and deliver up to 1.77 mW in continuous wave operation at room temperature. Fundamental mode continuous-wave lasing at wavelengths beyond 1300 nm at room temperature is reached for a 4 μm oxide diameter VCSEL. The particular design of the active layer based on a large detuning between the gain maximum and the cavity resonance gives our devices a very specific thermal and modal behaviour. Therefore, we study the spectral and spatial distributions of the transverse modes by near field scanning optical microscopy using a micropolymer tip at the end of an optical fibre.
We report results on strained InGaAs quantum well Vertical Cavity Surface Emitting Lasers (VCSELs) for optical interconnection applications. The structure was grown by metalorganic vapour-phase epitaxy (MOVPE) and processed as top p-type DBR oxide-confined device. Our VCSELs exhibit low threshold currents and deliver up to 1.77 mW in continuous wave operation at room temperature. Fundamental mode continuous-wave lasing at wavelengths beyond 1300 nm is demonstrated at room temperature. The thermal behaviour of our devices is explained through the threshold current-temperature characteristics. Furthermore, the effective index model is used to understand the modal behaviour.
In the past few years, many studies have been carried out to use the ability of light to transport information into silicon-based integrated photonic circuits. The realization of an efficient silicon-based light source is therefore necessary but however challenging. Lasing cannot be easily achieved from silicon emission because of its indirect bandgap. Therefore, one solution proposed is to use other efficient emitters, like rare earth, into silicon or Silicon On Insulator based microcavities. Silica microdisk has been demonstrated to support high-Q whispering-gallery modes, and can be upgraded to ultra-high-Q toroidal microcavities by a CO2 laser melting process. Microdisk high Q-factor balances the low gain generally obtained from the active medium. Thus, those microcavities may be good candidates
for silicon-based laser. In this paper, the fabrication and room
temperature operation of silica microdisk associated with Er-doped silicon rich oxide is presented. Er atoms are excited at the 351 nm wavelength via the silicon clusters, giving to the material a high photonic capture section, and therefore a good photoluminescence efficiency. We demonstrate efficient coupling of erbium atoms to high-Q whispering-gallery modes. The photoluminescence spectrum is then theoretically treated. The WGM resonances are thus identified. We also discuss the contribution of the spot excitation and the weak coupling to the higher radial order modes. Finally, the polarization dependence of the observed modes is investigated, and the experimental results are compared to our analytical model of disk-shape cavities. Those results give us to think that an integrated laser should be soon achieved.
We discuss the potential applications of single photon sources based on a single quantum dot, emphasizing the crucial importance of the efficiency parameter in view of applications in the field of quantum computing and quantum communications. By inserting the single quantum dot in a pillar microcavity, an efficiency as high as 44% has been obtained by using the Purcell effect. We show that this approach is limited in practice by extrinsic cavity losses, such as those related to the scattering by the sidewalls roughness. We present novel design rules for micropillars in view of this application and show that for the well-mastered GaAs/AlAs system more than 70% of the emission can be concentrated into the collimated emission beam associated with the fundamental cavity mode. We show finally that a novel design, based on a state-of-the-art 2D photonic crystal microcavity, could permit to reach efficiencies in excess of 0.95.
KEYWORDS: Multimedia, Manufacturing, Signal processing, Environmental management, Computing systems, Digital signal processing, Databases, Human-machine interfaces, Process control, Distributed computing
Along with the emergence of high-speed communications technologies and protocols, tools for multimedia applications are growing in terms of their variety and their performances, making multimedia data flows candidates to the integration in almost every computer system. We particularly focus on the case of the factory plant where sound and video equipments could soon take part in the control/monitoring of manufacturing processes. In this paper we propose a MMS-like multimedia application interface for such an environment.
The repartition ofnonradiative recombination centers density in a quantum well has been tested by timeresolved luminescence in samples containing an InAs plane inside a 16 nm wide GaAs well in Ga7AL3As. The results show unambiguously that more non radiative centers are located near the first grown interface. The non radiative carriers lifetime () vary between 4 ns when the InAs monolayer is close to the inverted interface and 8 ns when it is near the direct one.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.