Light-matter interaction at the atomic scale rules fundamental phenomena such as photoemission and lasing while enabling basic everyday technologies, including photovoltaics optical communications. In this context, plasmons, collective electron oscillations in conducting materials, are important because they allow manipulation of fields nanoscale. The advent graphene other two-dimensional crystals has pushed plasmons down to genuinely dimensions, displaying appealing properties a large...

Noble metal nanostructures are ubiquitous elements in nano-optics, supporting plasmon modes that can focus light down to length scales commensurate with nonlocal effects associated quantum confinement and spatial dispersion the underlying electron gas. Nonlocal naturally more prominent for crystalline noble metals, which potentially offer lower intrinsic loss than their amorphous counterparts, particular crystal facets giving rise distinct electronic surface states. Here, we employ a...

We present an analytic, Mie theory-based solution for the energy loss and photon-emission probabilities in interaction of spherical nanoparticles with electrons passing nearby through them, both cathodoluminescence electron energy-loss spectroscopies. In particular, we focus on case penetrating trajectories, which complete fully electrodynamic relativistic formalism has not been reported as yet. exhibit efficiency this method describing collective excitations matter calculations a dispersive...

Entangled photons are a key resource in quantum technologies. While intense laser light propagating nonlinear crystals is conventionally used to generate entangled photons, such schemes have low efficiency due the weak response of known materials and losses associated with in/out photon coupling. Here, we show how polariton pairs directly within optical waveguides using free electrons. The measured energy loss undeflected electrons heralds production counter-propagating emission direction....

Abstract Luminescence constitutes a unique source of insight into hot carrier processes in metals, including those plasmonic nanostructures used for sensing and energy applications. However, being weak nature, metal luminescence remains poorly understood, its microscopic origin strongly debated, potential unraveling nanoscale dynamics largely unexploited. Here, we reveal quantum-mechanical effects the emanating from thin monocrystalline gold flakes. Specifically, present experimental...

Swift electrons passing near or through metallic structures have proven to be an excellent tool for studying plasmons and other types of confined optical modes involving collective charge oscillations in the materials hybridized with electromagnetic fields. In this work, we provide a general analytical framework simulation electron energy-loss spectroscopy (EELS) infinite systems cylindrical symmetry, such as wires, holes, fibers. While EELS theory is well developed moving parallel direction...

Recent advances in nanofabrication technology now enable unprecedented control over 2D heterostructures, which single- or few-atom thick materials with synergetic opto-electronic properties can be combined to develop next-generation nanophotonic devices. Precise of light achieved at the interface between metal and dielectric layers, where surface plasmon polaritons strongly confine electromagnetic energy. Here we reveal quantum finite-size effects hybrid systems consisting graphene...

Promising applications in photonics are driven by the ability to fabricate crystal-quality metal thin films of controlled thickness down a few nanometers. In particular, these materials exhibit highly nonlinear response optical fields owing induced ultrafast electron dynamics, which is however poorly understood on such mesoscopic length scales. Here, we reveal new mechanism that controls metallic films, dominated electronic heat transport when sufficiently small. By experimentally and...

Plasmon-assisted harmonic generation in highly-doped graphene nanoribbons is strongly enhanced by the nonlocal optical response associated with large electromagnetic field gradients closely-spaced ribbons that have optimal size and position.

Nonlinear optics at the nanoscale is severely limited by small departure of available materials from linear behavior. Despite intense efforts placed into overcoming this problem using multiple strategies for enhancing near-field light intensity, all-optical active nanodevices remain a challenge. Here we introduce material-independent scheme quantifying enhancement nonlinear response in nanostructures assisted proximal metallic or dielectric nanoresonators. The proposed figures merit, which...

Noble metals with well-defined crystallographic orientation constitute an appealing class of materials for controlling light-matter interactions on the nanoscale. Nonlinear optical processes, being particularly sensitive to anisotropy, are a natural and versatile probe crystallinity in nano-optical devices. Here we study nonlinear response monocrystalline gold flakes, revealing polarization dependence second-harmonic generation from {111} surface that is markedly absent polycrystalline...

Abstract Entangled photons are pivotal elements in emerging quantum information technologies. While several schemes available for the production of entangled photons, they typically require assistance cumbersome optical to couple them other components involved logic operations. Here, we introduce a scheme by which photon pairs directly generated as guided mode states waveguides. The relies on intrinsic nonlinearity waveguide material, circumventing use bulky and their associated...

Nanoscale nonlinear optics is limited by the inherently weak response of conventional materials and small light-matter interaction volumes available in nanostructures. Plasmonic excitations can alleviate these limitations through subwavelength light focusing, boosting optical near fields that drive response, but also suffering from large inelastic losses are further aggravated fabrication imperfections. Here, we theoretically explore enhanced arising extremely confined plasmon polaritons...

In this paper, the authors explore band-structure and crystallographic-orientation effects in thin metal films through a tutorial theoretical description of electron energy-loss spectroscopy by treating response within random-phase approximation, including relevant details electronic band structure phenomenologically

Electron microscopy techniques such as electron energy-loss spectroscopy (EELS) facilitate the spatio-spectral characterization of plasmonic nanostructures. In this work, a time-dependent perspective is presented, which significantly enhances utility EELS. Specifically, silver nanowires offer material and geometric features for various high-quality excitations. This provides an ideal illustrative system combined experimental-theoretical analyses different excitations their real-time...

Recent advances in nanofabrication technology now enable unprecedented control over 2D heterostructures, which single-or few-atom-thick materials with synergetic optoelectronic properties can be combined to develop nextgeneration nanophotonic devices.Precise of light achieved at the interface between metal and dielectric layers, where surface plasmon polaritons strongly confine electromagnetic energy.Here we reveal quantum finite-size effects hybrid systems consisting graphene...

Luminescence constitutes a unique source of insight into hot carrier processes in metals, including those plasmonic nanostructures used for sensing and energy applications. However, being weak nature, metal luminescence remains poorly understood, its microscopic origin strongly debated, potential unravelling nanoscale dynamics largely unexploited. Here, we reveal quantum-mechanical effects emanating the from thin monocrystalline gold flakes. Specifically, present experimental evidence,...

We present an analytic, Mie theory-based solution for the energy-loss and photon-emission probabilities in interaction of spherical nanoparticles with electrons passing nearby through them, both cathodoluminescence electron spectroscopies. In particular, we focus on case penetrating trajectories, which complete fully electrodynamic relativistic formalism has not been reported as yet. exhibit efficiency this method describing collective excitations matter calculations a dispersive lossy...

Promising applications in photonics are driven by the ability to fabricate crystal-quality metal thin films of controlled thickness down a few nanometers. In particular, these materials exhibit highly nonlinear response optical fields owing induced ultrafast electron dynamics, which is however poorly understood on such mesoscopic length scales. Here, we reveal new mechanism that controls metallic films, dominated electronic heat transport when sufficiently small. By experimentally and...

We theoretically explore the enhancement in nonlinear response that can be achieved by interfacing multiple graphene nanostructures close proximity to trigger nonlocal effects associated with large gradients electromagnetic near-field. Our findings reveal importance of both passive and active tuning design atomically-thin for optical applications, particular emphasize role played generating an even-ordered may contribute other processes through a cascaded interaction.

Entangled photon pairs are a key resource in future quantum-optical communication and information technologies. While high-power laser light propagating bulk nonlinear optical crystals is conventionally used to generate entangled photons that routed into configurations, such schemes suffer from low efficiency due the weak intrinsic response of known materials losses associated with in- out-coupling. Here, we propose scheme polariton directly within waveguides using free electrons, whereby...

Thin films have attracted a great deal of attention within the nanophotonics community due to their ability strongly confine and manipulate light on extreme subwavelength scales. Recent advances in nanotechnology now enable fabrication with nanometer-scale thickness, which can potentially be used further miniaturize next generation electronic photonic devices. Nowadays, there exist many kinds materials that structured into thin films. Noble metals (Cu, Ag, Au, ...) are particularly...

Recent advances in nanofabrication technology now enable unprecedented control over 2D heterostructures, which single- or few-atom thick materials with synergetic opto-electronic properties can be combined to develop next-generation devices [1,2]. Precise of light achieved at the interface between metal and dielectric layers, where surface plasmon polaritons strongly confine electromagnetic energy. Here we reveal quantum finite-size effects hybrid systems consisting graphene few-atomic-layer...

The challenge of nonlinear optics stems from the negligible interaction among electromagnetic waves in free space, motivating substantial efforts to identify materials with sufficient anharmonic response as enable optical nonlinearities at low light powers [1]. On nanoscale, near-field intensity enhancement through resonators has been widely explored design active photonic devices operating on subwavelength scales [2]. Further interest nanoscale arisen isolation graphene and other...