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The enhancement of nonlinear optical effects via nanoscale engineering is a hot topic of research. Optical nanoantennas increase light-matter interaction and provide, simultaneously, a high throughput of the generated harmonics in the scattered light. However, nanoscale nonlinear optics has dealt so far with static or quasi-static configurations, whereas advanced applications would strongly benefit from high-speed reconfigurable nonlinear nanophotonic devices. Here we propose and experimentally demonstrate ultrafast all-optical modulation of the second harmonic (SH) from a single nanoantenna. Our design is based on a subwavelength AlGaAs nanopillar driven by a control femtosecond light pulse in the visible range. The control pulse photoinjects free carriers in the nanostructure, which in turn induce dramatic permittivity changes at the band edge of the semiconductor. This results in an efficient modulation of the SH signal generated at 775 nm by a second femtosecond pulse at the 1.55 ?m telecommunications (telecom) wavelength. Our results can lead to the development of ultrafast, all optically reconfigurable, nonlinear nanophotonic devices for a broad class of telecom and sensing applications.

Metasurfaces have recently gained extensive interest because of their extraordinary optical behavior as artificial material interfaces with ultrahigh compactness. In this framework, dielectric platforms have newly become very promising for nonlinear nanophotonics, providing opportunities, especially for ultrafast optical switching, and high harmonic generation, opening the research field of nonlinear metaoptics. Up to now, nonlinear metaoptics have been mostly explored using single metasurfaces. However, in a long-term vision, the stacking of optical metasurfaces, very challenging in terms of fabrication, is one key goal of this research field. Here, we demonstrate a three-layer metasurface in the AlGaAs-on-insulator platform, which improves the second harmonic generation efficiency by more than one order of magnitude with respect to its one-layer counterpart. Our achievement paves the way toward phase-shaping multilayer and multifunctional all-dielectric metasurfaces.

Photon-pair sources based on spontaneous parametric down-conversion (SPDC) are the backbone of a vast number of experimental implementations in quantum optics. Sub-wavelength-sized dielectric nanoresonators have recently emerged as a new platform for the implementation of SPDC sources [1] , that promise much potential in generating photons with engineered properties, as these nanoresonators offer a strong control over many parameters of the scattered light (directionality, polarization, …) However, the many degrees of freedom in these highly multi-modal and non-Hermitian systems makes design and formal description of pair-generation challenging.

A novel approach for resource recovery includes forward osmosis (FO) as a concentration step in municipal wastewater treatment. The current study investigates different pre-treatment strategies including biological treatment with a moving-bed bioreactor (MBBR) at different loading rates and particle removal by filtration and sedimentation. Membrane performance and recovery potential for energy and nutrients were investigated in laboratory-scale FO experiments in batch mode using pre-treated municipal wastewater as feed and 35 g/L NaCl as a draw solution. Initial water fluxes were in the range of 6.3 to 8.0 L/(m2·h). The baseline fluxes were modelled to account for flux decline due to concentration effects and to enable the prediction of flux decline due to membrane fouling. Fouling-related flux decline varied from 0 to 31%. Both organic fouling and precipitation of CaCO3 and CaHPO4 were identified by using SEM–EDS. High-rate flushing resulted in complete flux recovery under most conditions. Scaling could be avoided by lowering the pH. Two operation strategies were tested to achieve this: (1) applying a bioreactor with a low organic loading rate to achieve high nitrification, and (2) adding a strong acid. A low organic loading rate and the use of additional particle removal were efficient measures that reduced organic/particulate fouling. The recovery potentials for COD and phosphorous in FO concentrate were close to 100%.

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.

High refractive index dielectric nanostructures can be exploited to enhance nonlinear optical processes via the strong light confinement by their resonant modes. The sensitive dependence of these m...

The transient optical response of multiresonant all‐dielectric nanoantennas via a combination of broadband ultrafast reflectivity experiments and nonlinear optics nanoscale modeling is studied. Ultrafast all‐optical control of the reflectivity is demonstrated in variably sized Al.18Ga.82As nanoantennas over four distinct Mie resonances (including Fano‐like resonances), spanning a broad spectral range, from the red to the near‐infrared. A spatially inhomogeneous dynamical model, which accounts for diffusion of the photogenerated carriers inside the semiconductor, is introduced and exploited to isolate the physical phenomena leading to the overall transient response, namely, Drude plasma formation and Pauli blocking following band filling and thermo‐optical effect. The results pave the way to the development of multiwavelength all‐optically reconfigurable filters for next‐generation ultrafast add/drop multiplexing.

English Abstract: On 21 November 2017, the European Payments Council (EPC) introduced a new scheme for instant payments (SEPA Instant Credit Transfer- SCT Inst) in the Single Euro Payments Area (SEPA). The new scheme envisaged a maximum execution time of 10 seconds for the processing of each transaction and guaranteed service availability every day of the year, 24 hours a day. One year later, on 30 November 2018, Banca d’Italia – which had been commissioned by the Eurosystem to develop the system – delivered TIPS (TARGET Instant Payment Settlement), a new service for the settlement of instant payments in central bank money, which was also compliant with the SCT Inst scheme. Conceived as a multi-currency settlement platform, TIPS was developed with the aim, inter alia, of fostering the integration of retail payment services offered by the European financial community and of eliminating barriers due to lack of interoperability between different settlement platforms. The TIPS project is part of the Vision 2020 programme, which the Eurosystem has devised with the aim of providing new services to support financial markets, citizens, and businesses in Europe and to foster the innovation of market infrastructures and harmonization of financial services related to securities and cash. The Vision 2020 programme is part of the European Commission's Capital Markets Union project, aimed at achieving full integration of the European financial market. Building TIPS required the fulfilment of a number of particularly challenging technical requirements: virtually instant payment execution (with processing times per payment not exceeding 5 seconds); the capacity to handle a large volume of processed payments (over 43 million transactions per day); very high availability and resilience (reaching 99.9% service availability, and the capacity to restart within 15 minutes in a site disaster scenario); extreme scalability of the system from a performance viewpoint (the ability to sustain a doubling of the volume of payments over a year). About two years after the go-live, the number of payments settled in TIPS still falls short of these expectations and the potential of the service. However, albeit at different speeds in the various European countries, instant payment services are growing and it is reasonable to expect that this trend will only increase in the years to come. It is in this context that Banca d’Italia has already identified a series of actions that aim to prepare TIPS to become an essential component of the foreseeable spread of instant payment services in Europe. This paper is organized as follows: Chapters 1 and 2 illustrate the evolution of instant payment services in Europe and the fundamental principles of the TIPS service, respectively. Chapter 3 gives a detailed description of the TIPS system, outlining its functional perimeter (Section 3.1), presenting the technical characteristics of the platform on which it operates (Section 3.2), as well as the monitoring and management activities for the smooth operation of the service (Section 3.3). The governance of TIPS and the procedures for joining the service are then set out in Chapters 4 and 5. Finally, Chapter 6 outlines the main trends that Banca d’Italia, on the recommendation of the Eurosystem, has identified for TIPS for the years to come, both in terms of activities that are already in progress or being planned (Section 6.1), and with reference to other potential functionalities to be offered to the users in the near future (Section 6.2). Italian Abstract: [Il 21 novembre 2017, il Consiglio Europeo per i Pagamenti (European Payment Council – EPC) ha introdotto nell’area europea comune dei pagamenti (Single Euro Payments Area – SEPA) il nuovo schema per il pagamento di bonifici istantanei (SEPA Instant Credit Transfer – SCT Inst), che prevede un tempo massimo di esecuzione di ogni singola transazione non superiore ai 10 secondi e una disponibilita del servizio garantita tutti i giorni dell’anno, 24 ore al giorno. Un anno dopo, il 30 novembre 2018, la Banca d’Italia – che era stata incaricata dall’Eurosistema di sviluppare tale sistema – era gia in grado di avviare in esercizio il servizio TIPS (TARGET Instant Payment Settlement), che consente il regolamento immediato di singoli pagamenti istantanei in moneta di banca centrale, in linea con lo schema SCT Inst. Il servizio, concepito come piattaforma di regolamento multi-valutaria, e stato sviluppato con l’obiettivo, tra gli altri, di favorire l’integrazione dei servizi di pagamento al dettaglio offerti dalla comunita finanziaria europea e di eliminare le barriere dovute alla scarsa interoperabilita tra le piattaforme di regolamento preesistenti. Il progetto TIPS si inquadra nel piu generale contesto del programma Vision 2020, che l’Eurosistema ha elaborato allo scopo di fornire nuovi servizi a supporto dei mercati finanziari e dei cittadini e delle imprese in Europa e per favorire l’innovazione delle infrastrutture di mercato e l’armonizzazione dei servizi finanziari relativi ai titoli e al contante. Il programma Vision 2020 si inscrive nell’ambito del progetto Capital Markets Union della Commissione europea, volto a conseguire la piena integrazione del mercato finanziario europeo. La realizzazione di TIPS ha richiesto di soddisfare una serie di requisiti tecnici particolarmente sfidanti: una elevata velocita di elaborazione del singolo pagamento (tempo non superiore a 5 secondi1); un cospicuo volume di pagamenti regolabili (oltre 43 milioni di operazioni al giorno); un’altissima disponibilita e una solida resilienza del servizio (che deve essere costantemente attivo, con disponibilita del 99,9% e in grado di ripartire entro 15 minuti a seguito di eventi disastrosi); una estrema scalabilita del sistema dal punto di vista delle prestazioni (capacita di sostenere un raddoppio del volume dei pagamenti nell’arco di un anno). A circa due anni dalla partenza, il numero dei pagamenti regolati in TIPS resta ancora al di sotto delle aspettative e delle potenzialita del servizio. Tuttavia, pur se con velocita diverse nei diversi paesi europei, i servizi di pagamento istantanei si stanno diffondendo ed e lecito attendersi che tale tendenza si accentui negli anni a venire. E in tale contesto che la Banca d’Italia ha gia avviato una serie di interventi che si prefiggono l’obiettivo di preparare TIPS a sostenere la prevedibile diffusione dei servizi di pagamento istantanei in Europa e a diventarne una componente essenziale. Il presente lavoro e organizzato come segue: i capitoli 1 e 2 illustrano rispettivamente l’evoluzione dei servizi di pagamento istantaneo in Europa e i principi fondamentali del servizio TIPS. Il capitolo 3 descrive in dettaglio il sistema TIPS, delineando il perimetro delle funzionalita che esso offre all’utenza (§.3.1), presentando le caratteristiche tecniche della piattaforma su cui opera (§.3.2), nonche le attivita di monitoraggio e gestione dell’operativita del servizio (§.3.3). La governance di TIPS e le modalita di adesione al servizio vengono poi esposte nei capitoli 4 e 5. Il capitolo 6, infine, delinea le principali linee evolutive di TIPS che la Banca d’Italia, su indicazione dell’Eurosistema, ha tracciato per gli anni a venire, sia per quanto riguarda gli interventi gia in corso di realizzazione o in programma (§.6.1), sia con riferimento ad altre potenziali funzionalita da offrire all’utenza nel prossimo futuro (§.6.2).]

OBJECTIVE To identify urodynamic predictors for de novo overactive bladder (OAB) after single-incision sling implantation. METHODS This retrospective study analyzed women with pure, urodynamically proven stress urinary incontinence, without OAB, between 2008 and 2015, in a university hospital. De novo OAB was investigated during clinical interviews. RESULTS A total of 192 patients were analyzed; 21 patients with de novo OAB were considered as group A while 171 control patients formed group B. Univariate analysis demonstrated that patients with de novo OAB have the first desire to void at a lower bladder volume (124 mL versus 160 mL, P = 0.0052), smaller maximum cystometric capacity (357 mL versus 406 mL, P = 0.0061), lower maximum flow (17 mL/s versus 23 mL/s, P = 0.0006), and higher bladder outlet obstruction index (BOOI; -11 versus -23, P = 0.0022) compared with controls. According to multivariate analysis, maximum cystometric capacity (parameter estimate [PE] =0.008, P = 0.04) and BOOI (PE = -0.029, P = 0.01) were independent urodynamic predictors of de novo OAB. The final model showed good predictive accuracy (area under the curve =0.81). CONCLUSION The present study identified maximum cystometric capacity and BOOI as independent predictors of de novo overactive bladder after single-incision sling implantation. Therefore, preoperative urodynamics may be useful to improve preoperative counseling and to tailor surgical treatment.

Single-incision slings are not considered a first-choice surgical treatment owing to a lack of data about long-term outcomes. We aimed to assess the long-term results of urinary incontinence treatment after single-incision sling implantation at 10 years’ follow-up and to investigate possible deterioration over time. This retrospective study analyzed women with subjective and urodynamically proven stress urinary incontinence who underwent single-incision sling procedure. The objective cure rate was assessed with a 300-ml stress test. The subjective cure rate was determined by the Patient Global Impression of Improvement (PGI-I) questionnaire. International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) questionnaire scores and self-answered patient-satisfaction scales were collected to assess symptom severity. Findings were compared with short-term outcomes in the same patients, available through our previous database, in order to detect possible outcome deterioration over time. The records of 60 patients were analyzed. Nine patients (15%) were lost to follow-up. A total of 51 patients completed the evaluation, with a mean follow-up of 10.3 ± 0.7 years. Objective and subjective cure resulted 86.3% and 88.2% respectively. Mean PGI-I scores and ICIQ-SF were 1.5 ± 1.0 and 3.2 ± 4.8 respectively. Patients’ satisfaction scored 8.6 ± 2.6 out of 10. No long-term complications occurred. Comparison of short-term (2.6 ± 1.4 years after surgery) and long-term follow-up did not show a significant deterioration of outcome over time. Single-incision slings were shown to be a procedure with a great efficacy and safety profile at very long-term follow-up. Cure rates and functional outcomes did not show any deterioration over time compared with short-term results.

Nanoscale optical integration is nowadays a strategic technological challenge and the ability of generating and manipulating nonlinear optical processes in sub-wavelength volumes is pivotal to realize efficient sensing probes and photonic sources for the next-generation communication technologies. Yet, confining nonlinear processes below the diffraction limit remains a challenging task because phase-matching is not a viable approach at the nanoscale. The localized fields associated to the resonant modes of plasmonic and dielectric nanoantennas offer a route to enhance and control nonlinear processes in highly confined volumes. In my talk I will discuss two nonlinear platforms based on plasmonic and dielectric nanostructures. The first relies on a broken symmetry antenna design, which brings about an efficient second harmonic generation (SHG). We recently applied this concept to an extended array of non-centrosymmetric nanoantennas for sensing applications. I will also show the evidence of a cascaded second-order process in Third Harmonic Generation (THG) in these nanoantennas. Recently, dielectric nanoantennas emerged as an alternative to plasmonic nanostructures for nanophotonics applications, thanks to their sharp magnetic and electric Mie resonances along with the low ohmic losses in the visible/near-infrared region of the spectrum. I will present our most recent studies on the nonlinear properties of AlGaAs dielectric nanopillars. The strong localized modes along with the broken symmetry in the crystal structure of AlGaAs allow obtaining more than two orders of magnitude higher SHG efficiency with respect to plasmonic nanoantennas with similar spatial footprint and using the same pump power. I will also discuss a few key strategies we recently adopted to optically switch the SHG in these antennas even on the ultrafast time scale. Finally, I will show how to effectively engineer the sum frequency generation via the Mie resonances in these nanoantennas. These results draw a viable blueprint towards room-temperature all optical logic operation at the nanoscale.

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.

All-dielectric optical metasurfaces consist of 2D arrangements of nanoresonators and are of great importance for shaping polarization, phase and amplitude of both linear and harmonic fields. Here, we demonstrate the generation of second harmonic (SH) with zero-order diffraction from nonlinear AlGaAs metasurfaces with spatial period comparable with a pump wavelength in the near-IR. Upon normal incidence of the pump, we demonstrate paraxial SH light into the zero order. SH polarization is effectively controlled via either the meta-atom shape or the pump polarization, with potential applications for on-axis imaging and free-space communication systems.

We demonstrate that reshaping of electromagnetic fields in hyperbolic metamaterials with plasmonic components can be used to engineer strong tunable bulk second order nonlinear response in plasmonic composites with application in high resolution nonlinear tomography. In order to analyze nonlinear response of an anisotropic plasmonic metamaterial slab we compare numerical and analytical calculations with experimental results. The results open up possibilities to design tuneable frequency-doubling integratable metamaterials with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.

High-permittivity III-V semiconductor nanocavities have shown huge potential for enhanced nonlinear light-matter interactions at the nanoscale. In particular, Second Harmonic (SH) generation in AlGaAs nanoantennas can be extremely efficient; however, vertical emission is difficult to achieve, due to the zincblende χ(2) tensor and epitaxially growth on (100) substrates. Here, we demonstrate that we can shape the second harmonic radiation pattern from a single AlGaAs nanostructure by exploiting a geometrical symmetry breaking optimization approach. The optimized design allows to redirect the SH signal toward the normal direction and to increase the SH power collection efficiency by 2 orders of magnitude in a small numerical aperture of 0.1 with respect to the symmetrical counterpart structure.

We demonstrate an AlGaAs metasurface that implements second harmonic generation with engineered phase-front. Nonlinear holography is obtained, with three-order-of-magnitude higher conversion efficiency than in χ(3) plasmonic metasurfaces.

We propose a robust design for both second harmonic generation and its wavefront control in an AlGaAs-on-sapphire metasurface. In analogy with optical phased arrays, we achieve 0-2π phase modulation on the second harmonic.

High-permittivity semiconductor nanoresonators have shown great potential for enhanced nonlinear light–matter interactions at the nanoscale due to the availability of a rich variety of resonances combined with low optical losses and a strong bulk nonlinearity. Second-harmonic generation in AlGaAs nanoantennas can be extremely efficient and exhibits a complex radiation pattern. However, the complexity of this far-field profile imposes severe constraints on practical applications and detection efficiency. In this work, we demonstrate, both experimentally and numerically, the control over the angular distribution of the second-harmonic radiation pattern from a monolithic AlGaAs-on-AlOx nanodisk by varying the polarization and the angle of incidence of the pump beam. By tuning the angle of incidence of a beam with s-polarized light from 0 to 45°, the detected second-harmonic signal is monotonically increased up to over an order of magnitude due to the strong dependence of the nonlinear radiation pattern on th...

Carbon dioxide capture from cement plant flue gas can play an important role in mitigating CO2 emission that lead to climate change. Among all the technologies evaluated, membranes have potential to be one of the most energy-efficient and low-cost CO2 capture option. In this work, a novel membrane technology, Facilitated Transport Membranes (FTMs), is assessed to further reduce energy demand and cost for CO2 capture in a cement plant. A new process that employs FTMs is simulated and applied to a real clinker production plant in Italy (Colacem, Gubbio). The process is then compared with other carbon capture technologies. Results show that the FTM technology can be competitive with other technologies despite the need of steam to operate the membrane. Despite the benefit in terms of specific emission compared to more established absorption with liquid amines process, further improvements on membrane performances are needed to gain also an economic advantage for carbon capture in the cement industry.

Metal-less nanophotonics offers new opportunities for non-linear optics with respect to optical waveguides and microresonators, taking advantage of the progress within nanofabrication to boost the development of subwavelength Mie-type structures. Here, we review recent results on second harmonic generation with semiconductor nanoresonators, focusing on their scattering features in terms of efficiency and control over radiation patterns. First, two theoretical models are comparatively discussed with a view to possible improvements in analysis and design. Then, some relevant experiments are reported, and the origin of the χ(2) generation is discussed, outlining the main open topics to investigate in the near future and the advantages offered by these nanostructures to the development of novel photonic devices.

All-dielectric nanophotonics has recently raised an increasing interest because the optical response of high-permittivity dielectric nanoparticles exhibits negligible dissipative losses and strong magnetic multipole resonances [1–4] in the visible and near-IR. We recently reported a second harmonic generation (SHG) conversion efficiency higher than 10−5 at 2 = 1554 nm (pump intensity ≈ 1.6 GW/cm2; pulse width ≈ 150 fs; repetition rate = 80 MHz) in all-dielectric Al 0.18 Ga 0.82 As-on-AlOx nanodisks [5–7]. Such a remarkable efficiency is achieved thanks to the exploitation of magnetic and electric resonances emerging at coincidence with both the pump and SHG wavelength. In addition, the choice of both the pump and, consequently, the SHG (≈ 777 nm) wavelength, set below the energy of the material bandgap, allow minimizing the two-photon absorption of the pump and the re-absorption of the SHG.

All-dielectric optical metasurfaces consist of two-dimensional arrangements of nanoresonators and are of great importance for shaping polarization, phase and amplitude of both linear and harmonic light waves. Up to date, their reported nonlinear optical properties have been dominated by the local features of the individual nanoresonators [1–3]. However, collective responses typical of either Mie-resonant metamaterials or photonic crystals can potentially boost the control over such optical properties. In this work, we demonstrate the generation of second harmonic with zero-order diffraction from quadratically nonlinear metasurfaces, made out of AlGaAs-on-AlOx nanocylinders with spatial period comparable with a pump wavelength in the optical telecom range. Upon normal incidence of the pump beam, we demonstrate that the modulation of Mie-resonances via Bragg scattering at both fundamental and second harmonic frequencies enables paraxial second harmonic light diffraction back into the zero order, based on effective optical properties. This zero-order second harmonic (SH) diffraction results in a 50-fold increase of the detected harmonic power within a solid angle of 5° (see Figure 1). Moreover, 90% of the incident polarization is converted in the SH cross-polarized component, in contrast to around 40% measured previously for isolated nano-antennas [4–7]. This is achieved by a stronger coupling of the incident light with the metasurface resonances at both fundamental and harmonic frequencies with respect to the original Mie-resonances of the isolated constituents. In addition, upon pumping a polarization-gradient χ(2) metasurface with varying incident polarizations, highly horizontal and diagonal linear polarized zero-order SH states can be achieved. Our results demonstrate that higher control of polarization, phase, and amplitude of the harmonic wavefront can be achieved in diffractive all-dielectric nonlinear metasurfaces, with applications for on-axis optical imaging.

International audience; All-dielectric metasurfaces consist of two-dimensional arrangements of nanoresonators and are of paramount importance for shaping polarization, phase, and amplitude of both fundamental and harmonic optical waves. To date, their reported nonlinear optical properties have been dominated by local features of the individual nanoresonators. However, collective responses typical of either Mie-resonant metamaterials or photonic crystals can potentially boost the control over such optical properties. In this work we demonstrate the generation of a second harmonic optical wave with zero-order diffraction, from a metasurface made out of AlGaAs-on-AlOx nanocylinders arranged with spatial period comparable to the pump telecom wavelength. Upon normal incidence of the pump beam, the modulation of Mie resonances via Bragg scattering at both fundamental and second harmonic frequencies enables paraxial second harmonic light generation by diffraction into the zero order, with a 50-fold increase in detected power within a solid angle of 5°. Exquisite control of a higher harmonic wavefront can be thus achieved in all-dielectric nonlinear metasurfaces, with potential applications for on-axis optical systems.

This article discusses the most recent actions at international and European level for de-offshoring the world. From the automatic exchange of information to the sophisticated rules to fight money laundering and the use of the financial systems for terrorist financing, everything seems to go into the direction of a world tax transparency. However, there is a dark side of these international efforts that brings to re-offshoring again, in a never-ending story of States trying to eat the revenue from each other.

We experimentally demonstrate the capability of semiconductor monolithic metasurfaces to control the polarization state of optical second-harmonic generation. Based on the properties of single Mie-resonator scattering, we design and fabricate AlGaAs-on-insulator metasurfaces whose spatial periodicity allows us to decouple polarization and diffraction features. This enables collection of a polarization-engineered harmonic field in a small solid angle around the zero-diffraction order. Our metasurfaces rely on a AlGaAs/AlAs/GaAs metal-organic chemical vapor deposition structure, which makes them promising for optoelectronic integration.

We demonstrate the shaping of the second-harmonic (SH) radiation pattern from a single AlGaAs nanodisk antenna using coplanar holographic gratings. The SH radiation emitted from the antenna toward the-otherwise forbidden-normal direction can be effectively redirected by suitably shifting the phase of the grating pattern in the azimuthal direction. The use of such gratings allows increasing the SH power collection efficiency by 2 orders of magnitude with respect to an isolated antenna and demonstrates the possibility of intensity-tailoring for an arbitrary collection angle. Such reconstruction of the nonlinear emission from nanoscale antennas represents the first step toward the application of all-dielectric nanostructures for nonlinear holography.

Dielectric nanocavities are emerging as a versatile and powerful tool for the linear and nonlinear manipulation of light at the nanoscale. In this work, we exploit the effective coupling of electric and toroidal modes in AlGaAs nanodimers to locally enhance both electric and magnetic fields while minimizing the optical scattering, thereby optimizing their second-harmonic generation efficiency with respect to the case of a single isolated nanodisk. We also demonstrate that proper near-field coupling can provide further degrees of freedom to control the polarization state and the radiation diagram of the second-harmonic field.

All-dielectric nanoantennas enable the manipulation and confinement of light on the nanoscale through a variety of resonant excitations. Understanding and controlling the interactions among resonances at a level of individual nanoantennas is required for the development of appropriate design rules for their applications, especially with regard to nonlinear optics, where the nonlinear interaction depends on the resonant behavior in a superlinear manner. Here, cathodoluminescence imaging spectroscopy is used to experimentally investigate the electric and magnetic modes supported by single AlGaAs nanoantennas and their hybridization in a dimer configuration. An interplay is shown between the resonant modes of the nanostructures and interband emission of the semiconductor material, which contrasts with Si nanoantennas, where the bandgap effects are not significant. The measurements are in very good agreement with numerical simulations, which also provided further insight into the nature of the modes. The resonant modes of semiconductor nanoantennas are important for engineering linear and nonlinear metasurfaces, as well as for sensing applications and fluorescence control in nanophotonic environments.

We demonstrate a 5-fold enhancement of second harmonic generation efficiency and control on polarization of thereby generated photons exploiting the near-field coupling between electric and toroidal dipole modes in AlGaAs nanodimers.

© 2018 The Author(s). We demonstrate experimentally the generation of sum-frequency signal and heralded photons with non-classical correlations via spontaneous parametric down-conversion in AlGaAs nanodisks.

Background: Dielectric nanoantennas have recently emerged as an alternative solution to plasmonics for nonlinear light manipulation at the nanoscale, thanks to the magnetic and electric resonances, the strong nonlinearities, and the low ohmic losses characterizing high refractive-index materials in the visible/near-infrared (NIR) region of the spectrum. In this frame, AlGaAs nanoantennas demonstrated to be extremely efficient sources of second harmonic radiation. In particular, the nonlinear polarization of an optical system pumped at the anapole mode can be potentially boosted, due to both the strong dip in the scattering spectrum and the near-field enhancement, which are characteristic of this mode. Plasmonic nanostructures, on the other hand, remain the most promising solution to achieve strong local field confinement, especially in the NIR, where metals such as gold display relatively low losses.Results: We present a nonlinear hybrid antenna based on an AlGaAs nanopillar surrounded by a gold ring, which merges in a single platform the strong field confinement typically produced by plasmonic antennas with the high nonlinearity and low loss characteristics of dielectric nanoantennas. This platform allows enhancing the coupling of light to the nanopillar at coincidence with the anapole mode, hence boosting both second- and third-harmonic generation conversion efficiencies. More than one order of magnitude enhancement factors are measured for both processes with respect to the isolated structure.Conclusion: The present results reveal the possibility to achieve tuneable metamixers and higher resolution in nonlinear sensing and spectroscopy, by means of improved both pump coupling and emission efficiency due to the excitation of the anapole mode enhanced by the plasmonic nanoantenna.

All-dielectric and semiconductor nonlinear nanophotonics is an emerging field enabling efficient optical interactions between magnetic and electric resonances at sub-wavelength scales, thereby achieving high directionality and high figures of merit due to very low losses [1, 2]. It was shown that AlGaAs nanodisks with quadratic nonlinear susceptibility can provide second harmonic generation (SHG) with record-high efficiency of 10−4 [3], opening to a wide range of possible applications, including nonlinear microscopy and holography. In this work, we show experimentally that the strong quadratic nonlinearity in AlGaAs nano-disks allows efficient sum-frequency generation (SFG) with nontrivial polarization dependencies. By using the established classical-quantum analogy [4], we predict that these nano-resonators can facilitate efficient generation of quantum entangled photon pairs with higher than kHz biphoton rate and strong angular correlations.

All-dielectric and semiconductor nonlinear nanophotonics has recently provided unprecedentedly efficient optical interaction between magnetic and electric resonances due to very low losses [1, 2]. Fine-tuning of the sizes of single dielectric nanodisks allows for spectral control of their resonances. Additionally, dimers, which are composed of two dielectric nanodisks with a subwavelength gap, supporting both electric and magnetic multipoles, may act as more efficient light concentrators, exceeding the magnetic field intensity of single nanodisks by two order of magnitudes [3]. Dimers may also enhance the local density of states, and thus, for example, may modify magnetic transition rates in quantum emitters [4]. Silicon nanodisks and dimers, which are CMOS compatible, have been extensively studied [5]. However, recently AlGaAs-on-oxide monolithic nanoantennas that are compatible with nanophotonic technology have been developed [6, 7], paving the way for record high second order nonlinearities [8], and efficient generation of quantum entangled photon pairs through spontaneous parametric down-conversion.

We review recent achievements in the field of nanoscale nonlinear AlGaAs photonics based on all-dielectric optical antennas. After discussing the motivation and main technological challenges for the development of an AlGaAs monolithic platform for χ (2) nonlinear nanophotonics, we present numerical and experimental investigations of the second-order nonlinear response and physical reasons for high efficiency of second-order nonlinear interactions in the AlGaAs nano-antennas. In particular, we emphasize the role of the dipolar resonances at the fundamental frequency and the multipolar resonances at the second harmonic wavelength. We also discuss second-harmonic generation directionality and show possible strategies to engineer the radiation pattern of nonlinear antennas.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement Optical nanoantennas have shown a great capacity for efficient extraction of photons from the near to the far field, enabling directional emission from nanoscale single-photon sources. However, their potential for the generation and extraction of multi-photon quantum states remains unexplored. Here we experimentally demonstrate the nanoscale generation of two-photon quantum states at telecommunication wavelengths based on spontaneous parametric down-conversion in an optical nanoantenna. The antenna is a crystalline AlGaAs nanocylinder, possessing Mie-type resonances at both the pump and the bi-photon wavelengths, and when excited by a pump beam it generates photon pairs with a rate of 35 Hz. Normalized to the pump energy stored by the nanoantenna, this rate corresponds to 1.4 GHz/Wm, being 1 order of magnitude higher than conventional on-chip or bulk photon-pair sources. Our experiments open the way for multiplexing several antennas for coherent generation of multi-photon quantum states with complex spatial-mode entanglement and applications in free-space quantum communications and sensing.

Plasmonic nanowire metamaterials, arrays of aligned plasmonic nanowires grown inside an insulating substrate, have recently emerged as a flexible platform for engineering refraction, diffraction, and density of photonic states, as well as for applications in bio- and acoustic sensing. Majority of unique optical phenomena associated with nanowire metamaterials have been linked to the collective excitation of cylindrical surface plasmons propagating on individual nanowires. From the effective medium standpoint, this collective excitation can be described as an additional electromagnetic wave, emanating from nonlocal effective permittivity of metamaterial. The electromagnetic fields associated with such mode can are strongly inhomogeneous on the scale of the unit cell. In this work we analyze the effect of the strong field variation inside nanowire metamaterial on second harmonic generation (SHG). We show that second harmonic generation is strongly enhanced in the frequency region where metamaterial is nonlocal. Overall, the composite is predicted to outperform its homogeneous metal counterparts by several orders of magnitude. Quantitative description of SHG in nanowire medium is developed. The results suggest that bulk second harmonic polarizability emerges as result of collective surface-enhanced SHG by individual components of the composite.

In this talk, we numerically demonstrate the potential of a hyperbolic medium in the design of an efficient metamaterial antenna enhancing the second harmonic generation of a nano-object, with an otherwise hidden nonlinear signature through a metamaterial-assisted access to evanescent second-harmonic fields. In further discussion, we consider the second harmonic generation from the metamaterial itself and report the criterion of its efficiency.

Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. Here we report a full vectorial numerical model to study SHG in a plasmonic nanorod metamaterial slab. Our frequency-domain implementation of the hydrodynamic model of the metal permittivity for conduction electrons provided a full description of the nonlinear susceptibility in a broad spectral range. We show that the modal overlap of fundamental and second-harmonic light in the plasmonic metamaterial slab results in the frequency tuneable enhancement of radiated second-harmonic intensity by up to 2 orders of magnitudes for TM- and TE-polarized fundamental light, compared to a smooth Au film under TM-polarised illumination. A double-resonant condition with both the enhancement of fundamental field and the enhanced scattering of the second-harmonic field can be realised at multiple frequencies due to the mode structure of the metamaterial slab. The nanostructured geometry of the Au nanorod metamaterial provides a larger surface area compared to the centrosymmetric crystal lattice of gold, which is needed for exploiting the intrinsic surface nonlinearity of gold. The numerical model allows us to explain experimental investigations on the spectral behaviour and radiation diagram of the second harmonic signal. In the experiments SHG generated under femtosecond excitation with varying wavelength, polarization, and angle of incidence, was characterized in backward and forward directions. We show that the excitation of plasmonic modes in the array can remarkably enhance the nonlinear response of the system, as predicted by the model. The results open up wide ranging possibilities to design tuneable frequency-doubling metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.

Plasmonic metamaterials and metasurfaces open up possibility to design the enhanced second- and third-order nonlinear optical properties in a desired spectral range beyond nonlinear optical response of their constituents. Here we overview optical nonlinearities and optomechanical effects enabled by metamaterials.

We designed cylindrical AlGaAs-on-aluminium-oxide all-dielectric nanoantennas with magnetic dipole resonance at near-infrared wavelengths. Our choice of material system offers a few crucial advantages with respect to the silicon-oninsulator platform for operation around 1.55μm wavelength: absence of two-photon absorption, high χ(2) nonlinearity, and the perspective of a monolithic integration with a laser. We analyzed volume second-harmonic generation associated to a magnetic dipole resonance in these nanoantennas, and we predict a conversion efficiency exceeding 10-3 with 1GW/cm2 of pump intensity.

Purpose. This multicenter randomized study was designed to compare the clinical and functional results of stapled transanal rectal resection (STARR) performed with 2 staplers (PPH-01 vs. PPH-03) in the treatment of hemorrhoidal disease associated with a large internal rectal prolapse. Methods. From a total of 937 patients, referred for hemorrhoidal disease in the 20 centers involved in the study, 425 (45.3%) with prolapsed hemorrhoids associated with a large internal rectal prolapse were randomized to undergo STARR with PPH-01 or PPH-03. Postoperative evaluation was made at 3, 6, and 12 months. Results. The incidence of bleeding at the stapled line was significantly lower in the PPH-03 group than in the PPH-01 group (58/207 [28.0%] vs. 145/201 [72.1%]; P < .0001); the mean number of hemostatic stitches was significantly higher in the PPH-01 than in the PPH-03 group (3.2 ± 0.1 vs. 1.8 ± 0.8; P < .0001). The mean operative time was 25.1 ± 11.5 minutes in the PPH-03 group and 38.1 ± 15.7 minutes in the PPH-01 group ( P < .0001). No major complications occurred in either of the groups. At 12-month follow-up, the success rate in the 2 groups was 94.5% in the PPH01 group and 94.2% in the PPH03 group. Conclusion. STARR performed for the treatment of hemorrhoidal disease associated with a large rectal prolapse is a safe and effective procedure. The use of the PPH-03 stapler instead of the PPH-01 guarantees a statistically significant reduction of intraoperative bleeding and a significant decrease of the operative time.

Nonlinear processes are at the core of many optical technologies whose further development require optimized materials suitable for nanoscale integration. Here we demonstrate the emergence of a strong bulk second-order nonlinear response in a plasmonic nanorod composite comprised of centrosymmetric materials. We develop an effective-medium description of the underlying physics, compare its predictions to the experimental results, and analyze the limits of its applicability. We demonstrate strong tunable generation of the p-polarized second-harmonic light in response to either s-orp-polarized excitation. High second-harmonic enhancement is observed for fundamental frequencies in the epsilon-near-zero spectral range. The work demonstrates emergence of structurally tunable nonlinear optical response in plasmonic composites and presents a new nonlinear optical platform suitable for integrated nonlinear photonics.

Hyperbolic plasmonic metamaterials provide numerous opportunities for designing unusual linear and nonlinear optical properties. We show that the modal overlap of fundamental and second-harmonic light in an anisotropic plasmonic metamaterial slab results in the broadband enhancement of radiated second-harmonic intensity by up to 2 orders of magnitudes for TMand TE-polarized fundamental light compared to a smooth Au film under TM-polarised illumination. The results open up possibilities to design tuneable frequency-doubling metamaterial with the goal to overcome limitations associated with classical phase matching conditions in thick nonlinear crystals.

Wave interference is a fundamental manifestation of the superposition principle with numerous applications. Although in conventional optics, interference occurs between waves undergoing different phase advances during propagation, we show that the vectorial structure of the near field of an emitter is essential for controlling its radiation as it interferes with itself on interaction with a mediating object. We demonstrate that the near-field interference of a circularly polarized dipole results in the unidirectional excitation of guided electromagnetic modes in the near field, with no preferred far-field radiation direction. By mimicking the dipole with a single illuminated slit in a gold film, we measured unidirectional surface-plasmon excitation in a spatially symmetric structure. The surface wave direction is switchable with the polarization., This work has been supported in part by the Engineering and Physical Sciences Research Council (grant EP/H000917/2). F.J.R.-F. acknowledges support from grant FPI of Generalitat Valenciana. A. M. acknowledges financial support from the Spanish government (contracts Consolider EMET CSD2008-00066 and TEC2011-28664-C02-02). P. G. acknowledges the Royal Society for a Newton International Fellowship.

Surgical therapy guaranties satisfactory results, which are significantly better than those obtained with conservative therapies, especially for Grade III and IV hemorrhoids. In this review, we present and discuss the results of the most diffuse surgical techniques for hemorrhoids. Traditional surgery for hemorrhoids aims to remove the hemorrhoids, with closure (Fergusson’s technique) or without closure (Milligan–Morgan procedure) of the ensuing defect. This traditional approach is effective, but causes a significant postoperative pain because of wide external wounds in the innervated perianal skin. Stapled hemorrhoidopexy, proposed by Longo, has gained a vast acceptance because of less postoperative pain and faster return to normal activities. In the recent literature, a significant incidence of recurrence after stapled hemorrhoidopexy was reported, when compared with conventional hemorrhoidectomy. Double stapler hemorrhoidopexy may be an alternative to simple stapled hemorrhoidopexy to reduce the recurrence in advanced hemorrhoidal prolapse. Transanal hemorrhoidal deartertialization was showed to be as effective as stapled hemorrhoidopexy in terms of treatment success, complications, and incidence recurrence. However, further high-quality trials are recommended to assess the efficacy and safety of this technique.

Background Routine drainage after laparoscopic cholecystectomy is still debatable. The present study was designed to assess the role of drains in laparoscopic cholecystectomy performed for nonacutely inflamed gallbladder. Methods After laparoscopic gallbladder removal, 53 patients were randomized to have a suction drain positioned in the subhepatic space and 53 patients to have a sham drain. The primary outcome measure was the presence of subhepatic fluid collection at abdominal ultrasonography, performed 24 h after surgery. Secondary outcome measures were postoperative abdominal and shoulder tip pain, use of analgesics, nausea, vomiting, and morbidity. Results Subhepatic fluid collection was not found in 45 patients (84.9 %) in group A and in 46 patients (86.8 %) in group B (difference 1.9 (95 % confidence interval -11.37 to 15.17; P = 0.998). No significant difference in visual analogue scale scores with respect to abdominal and shoulder pain, use of parenteral ketorolac, nausea, and vomiting were found in either group. Two (1.9 %) significant hemorrhagic events occurred postoperatively. Wound infection was observed in three patients (5.7 %) in group A and two patients (3.8 %) in group B (difference 1.9 (95 % CI -6.19 to 9.99; P = 0.997). Conclusions The present study was unable to prove that the drain was useful in elective, uncomplicated LC.