The recent advent of robust, refractory (having a high melting point and chemical stability at temperatures above 2000°C) photonic materials such as plasmonic ceramics, specifically, transition metal nitrides (TMNs), MXenes and transparent conducting oxides (TCOs) is currently driving the development of durable, compact, chip-compatible devices for sustainable energy, harsh-environment sensing, defense and intelligence, information technology, aerospace, chemical and oil & gas industries. These materials offer high-temperature and chemical stability, great tailorability of their optical properties, strong plasmonic behavior, optical nonlinearities, and high photothermal conversion efficiencies. This lecture will discuss advanced machine-learning-assisted photonic designs, materials optimization, and fabrication approaches for the development of efficient thermophotovoltaic (TPV) systems, lightsail spacecrafts, and high-T sensors utilizing TMN metasurfaces. We also explore the potential of TMNs (titanium nitride, zirconium nitride) and TCOs for switchable photonics, high-harmonic-based XUV generation, refractory metasurfaces for energy conversion, high-power applications, photodynamic therapy and photochemistry/photocatalysis. The development of environmentally-friendly, large-scale fabrication techniques will be discussed, and the emphasis will be put on novel machine-learning-driven design frameworks that leverage the emerging quantum solvers for meta-device optimization and bridge the areas of materials engineering, photonic design, and quantum technologies.

Meta-devices, which are advanced optical elements composed of meta-atoms engineered at the sub-wavelength scale, have garnered significant attention from researchers due to their ability to manipulate the characteristics of incident electromagnetic waves. However, conventional meta-devices, primarily consisting of a single type of meta-atom, suffer from an intrinsic lack of freedom, which in turn restricts their performance and limits their application potential. An integrated resonant unit (IRU) has emerged as a promising solution. It combines multiple meta-atoms, resonant modes, and functionalities into a supercell, can achieve responses and functionalities that exceed those of conventional meta-atoms. This talk will first illustrate the concept of IRUs and then employ two different types of IRUs, plasmonic and dielectric, to demonstrate their ability that break through the phase compensation limitations and improve working efficiency for enhancing achromatic focused beam generation. (Din Ping Tsai's Advanced Photonics review paper on integrated-resonant metadevices is the winner of a 2023 Advanced Photonics EIC’s Choice Award)

While numerous applications of plasmonic metamaterials to sensing and imaging the living matter are well-established, the effects of such photonic structures on the living matter itself are less explored. I will describe the concept of a designer bio-photonic metamaterial that can be used to (a) elicit specific responses from the living cells cultured atop of it, and (b) transduce such responses to optical signals. I will concentrate on several types of three-dimensional mixed-materials metasurfaces comprising plasmonic nano-antennas fabricated atop of tall high aspect ratio dielectric pillars. Cellular dynamics in aqueous environment is probed by illuminating the structures from below through an infrared-transparent substrate and collecting the reflected spectrum. By appropriately choosing the geometry of such elevated nano-antennas, we can induce the cells to wrap around them, thus enhancing the resulting reflected mid-infrared signal. We demonstrate that by increasing the height of the dielectric pillars, the penetration depth of the mid-infrared signal into the cell is also increased.

Two emerging material classes, namely, two-dimensional transition-metal carbides and nitrides (MXenes) and Weyl Semimetals (WSMs) offer exciting opportunities for tailorable photonic devices. The designer-like characteristics of MXenes, achievable with the choice of composition, stoichiometry and surface termination, and tunable properties of single crystalline WSMs, realized through the manipulation of surface conditions, lead to impressive tunability of optical properties in both systems. MXenes exhibit diverse optical properties ranging from plasmonic behavior to dielectric-to-metallic transition as well as strong nonlinear response useful for ultrafast applications. In turn, WSMs such as TaAs show high photocurrent generation and strong second-harmonic generation while WTe2 holds a promise for chiral anomaly applications. The manipulation of linear and nonlinear optical response including the epsilon near zero (ENZ) behavior as well as investigation of hybrid plasmonic-MXene and plasmonic-WSM structures open a broad range of applications for these materials in emerging photonics.

Three-dimensional metamaterial absorbers were applied for ultra-sensitive infrared spectroscopic molecular detection devices. Various types of 3D MIM metamaterial absorbers have been proposed for solid, liquid, and gas samples. Owing to their strong resonant absorption, unwanted background in IR spectroscopy was suppressed, and the signal-to-background ratios has been improved. For gas detection, a 3D co-axial double-cylinder structure is introduced as the unit structure of the metasurface absorber.

Light emission from single emitters, such as organic molecules, quantum dots, or nitrogen vacancies in nanocrystals strongly depends on the electromagnetic environment surrounding the emitter. The interaction of the emitter with strong local electromagnetic fields gives rise to an acceleration of the total decay rate (Purcell effect) which usually results in a broader emission line of the emitter, as well as an energy shift of the emission (Lamb shift). Plasmonic nanoantennas are versatile building blocks which localize light below the diffraction limit thanks to the extremely small effective mode volumes of localized surface plasmons, triggering out the possibility to tailor and exploit both the Purcell factor and the Lamb shift of nearby emitters, even reaching the strong coupling regime with polariton splitting in light emission. We theoretically describe light emission from a variety of nanoantenna-emitter configurations and reveal the potential of plasmonic nanogaps to tailor and engineering the Purcell factor and Lamb shift of light emitted from single nearby emitters, in agreement with experimental evidence.

Here, I'll cover two applications of nanophotonic metasurfaces in reflection. Firstly, we propose actively modulating the polarization state of lasing emissions at the source using a metasurface-engaged microcavity. This enhances interactions between light and metasurface atoms, resulting in highly pure and controllable polarized lasing emissions. Secondly, we introduce a compact snapshot hyperspectral imaging system integrating meta-optics and small-data deep learning. Operating in the visible window, our system using a single metasurface chip, demonstrates exceptional fidelity in generating hyperspectral data cubes. This integration promises low-profile advanced instruments for scientific studies and laser physics, bridging the gap between metasurfaces and real-world applications.

Metasurfaces are composed of sub-wavelength periodically arranged resonant structures that can manipulate wave-matter interactions in manners not observed in nature. All-optical and all-acoustic metasurfaces have separately demonstrated versatile capabilities such as lensing, beam steering or wavefront control. Here, we study a new class of acoustoplasmonic metasurfaces. By combining the physics of light and sound in previously unexplored ways, this platform enables entirely new avenues to harness the power of wave-matter interactions. This work paves the way toward versatile societal imaging applications ranging from environmental science to biomedical devices or industrial imaging.

High-resolution spatial light modulators are key elements in augmented and virtual reality systems, as well as in advanced LIDAR and angle-dependent sensors as well as advanced imaging systems. Hybrid devices containing liquid crystals, polymers, in combination with plasmonic or dielectric nanoantennas are state of the art. We pursue a different avenue which utilizes conductive polymers, consisting of PEDOT:PSS nanoantennas, who undergo a metal-to-insulator phase transition upon electrical switching in CMOS compatible voltage ranges. In order to reach the required spatial resolution for holograms with high fields of view, we directly pattern PEDOT:PSS by electron beam lithography. This way, 250 nm line widths in metasurface structures have been obtained. By using planar technologies, high-resolution active PEDOT metasurface switching is also attainable. Finally, we are going to demonstrate switching of optical metasurface resonances by a metal-to-insulator transition in inorganic materials.

Hybrid metasurfaces that combine plasmonic metals with dielectrics provide access to both electric and magnetic effects, as well as their combination. This is especially useful when quantum emitters, such as fluorescent molecules, are combined with the metasurface. On the one side, the strong field enhancement provided by the plasmonic metal can be used to excite the molecule, while the dielectric resonator can prevent fluorescence quenching, limit absorption and enhance radiation. In this presentation, we review the design and fabrication of such metasurfaces and characterize experimentally their interaction with fluorescent molecules. We also show how a location-specific position of the emitters can control the overall optical response.

Metamaterial absorbers are artificial materials that satisfy optical thicknesses and geometrical thinness simultaneously. By leveraging the characteristics of these metamaterials, we can artificially control the direction of heat flow on spaces or objects. For instance, we demonstrated the ability to generate artificial heat flow across an object or space by controlling the metamaterial arrangement, thereby achieving thermoelectric power generation in a uniform thermal radiation environment. This technology allows us to achieve energy harvesting while simultaneously achieving environmental cooling through non-radiative cooling. Additionally, we introduce the application of this metamaterial thermoelectric conversion technology to optical wireless powering.

In this talk, we will highlight our recent work on ultrathin metal films, epsilon-near-zero (ENZ) substrates, and 2D magnetic materials to engineer quantum phenomena. By exploiting ENZ properties, we manipulate quantum emitters' spontaneous emission rates, create radiative energy band gaps for nanoparticles, and utilize the Casimir effect to generate mechanical motion. Further, we show how ultrathin and 2D magnetic materials could allow for quantum levitation through the generation of nanoscale repulsive forces. Our work reveals the potential for novel device architectures harnessing these effects, offering insights into the intricate interplay between ENZ and 2D magnetic materials with quantum photonic phenomena.

Plasmonic hot carriers open new opportunities for light energy storage and conversion devices. Using monocrystalline gold, we report unprecedented details on hot-carrier dynamics and photoluminescence emission as well as hot carrier driven chemistry.

The surface of a gateless AlGaN/GaN high-electron-mobility transistor (HEMT) is very sensitive to the attachment of electric charges which can greatly affect its channel conductance. For near two decades, HEMT has been researched as a possible sensor for chemical and bio-spices. In this study, we demonstrate the ability of an AlGaN/GaN HEMT to detect surface plasmon via the plasmonic generated hot-carrier injection. A theoretical model explaining the detecting mechanism will be introduced and verified by several experimental results. We will also discuss several possible applications of HEMT devices in the field of Plasmonics.

Reconfigurable optical devices are key for enhancing optical interconnects, switching, and memory. Achieving high modulation depth with low voltage in the near-infrared (NIR) range remains challenging. This study introduces an electrically switchable device combining Tamm plasmon and PEDOT:PSS, achieving over 88% optical modulation across the NIR range with just ±1 V, compatible with CMOS technology. It works by adjusting charge carrier density through electrochemical doping/dedoping. This device also supports non-volatile multi-memory states, enabling rewritable optical memory and showing neuromorphic behavior, promising for free-space communication and imaging.

We first discuss all-optical modulation with single photons using electron avalanche, resulting in record-high nonlinearities. Then we show that transparent conducting oxides (TCOs) operating in the near-zero index (NZI) regime can provide strong single-cycle modulation, thus enabling novel photonic time crystals.

Transient photonics [1] encompass optical devices that can vanish on demand, after stable operation. In this talk, I will present a platform for transient photonics based on Mg and MgO, materials that dissolve in water at ambient environment [2]. We show vivid color pixels covering a large portion of the sRGB [3] and multi-wavelength absorbers [4], important for applications ranging from encryption to eco-friendly displays. Refs: [1] ACS Photonics 6, 272 (2019). [2] Optical Materials Express 11, 1555 (2021). [3] Adv. Optical Materials 10, 2200159 (2022). [4] ACS Applied Optical Materials 1, 825 (2023).

We will discuss the magneto-optical effects in indium tin oxide (ITO) thin films possessing the epsilon-near-zero (ENZ) wavelength in the telecommunication band. The Faraday rotation angle and the polar Kerr rotation angle of the ITO films are increased at around the corresponding ENZ and EN-one wavelengths, respectively, demonstrating enhanced MO effects in continuous ENZ materials. We also discuss some potential applications of ENZ-MO materials.

I will introduce two very different chalcogenide thin films that exhibit plasmonic or plasmonic-like behaviour in the visible spectrum. The first film is elemental tellurium and we argue that this plasmonic-like behaviour is due to partially delocalised p-orbital electrons that are readily polarized at frequencies in the visible spectrum.The Te films can support surface plasmon polariton-like modes and Te nanodiscs can support local surface plasmon resonances.We believe these results might pave the way for elemental Te-programmable photonics. I will also show how chalcogenide films can be used to grow silver nanoparticles over large areas. In particular, I will show how co-depositing Sb2S3 with Ag results in a perfect absorber material consiting of self-organised nanoresonators. We call this material Black Silver, and we have used it to detect femtomolar concentrations of streptavidin.

Keynote: It is now well understood from works on the topology of light, that complex optical fields (e.g. superoscillatory fields) can be structured at deeply subwavelength scales. Point-like singularities, zones of energy back-flow and strong variations of phase and intensity can be orders of magnitude smaller than the wavelength. As such, scattering of light on nanoscale objects can strongly depend on exactly where the object is actually located in the structured field. This is the foundational idea of metrology with topologically structured light. Moreover, in localization metrology the use of artificial intelligence in the analysis of scattered light allows for instrumental fluctuations and drifts in the whole sample position to be distinguished from the displacements of the nanoscale object with respect to its immediate environment. Furthermore, we demonstrate that ultrafast cameras allow atomic level metrology with a rate of one million measurements per second which gives access to the studies of dynamical processes such as driven or thermal motion in nanostructures.

Efficient optical coupling between propagating light and confined surface polaritons is crucial for nanophotonic device design. However, coupling efficiency diminishes significantly with increased mode confinement due to wavelength mismatch. Despite various proposed mechanisms, achieving flexible and efficient light-to-polariton coupling remains challenging. Our experimental demonstration showcases efficient light-to-surface-plasmon polariton coupling with engineered dipolar scatterers placed optimally from the surface. Gold disks separated by silica spacers from a planar gold surface exhibit perfect coupling conditions, achieved by tuning spacer thickness for a given scatterer geometry resonating at a specific optical frequency. We measure maximum coupling cross section close to the square of light wavelength at optimal distance, facilitated by strong particle-surface interaction and minimal surface-driven particle-dipole quenching, favored at small separations. Our findings, supported by analytical theory and electromagnetic simulations, advocate distant engineered scatterers as a disruptive solution for in/out-coupling challenges in nanophotonics.

Dynamic control over various properties of thermal emission can be achieved through sophisticated engineering of optical states without altering the object's temperature. This presentation introduces our recent study on the dynamic steering of thermal emission using a graphene-based metasurface device. We employ a laterally delocalized Fabry-Perot mode, whose phase condition can be actively tuned by adjusting the graphene's carrier density via electrostatic gating. We experimentally demonstrate that the device can steer thermal emission across a 16-degree range at a wavelength of 6.61 microns, while maintaining high emissivity.

The remarkable turnability with many degrees of freedom of metasurface has allowed for significant advancements in the field of optics. The direction and polarization of photon emission may be adjusted by coupling the geometric plasmonic metasurfaces with the dielectric Si cavity mode. Maintaining the Purcell factor, the hybrid structure with the designed configuration exhibits the highest electric field and best cross-polarization conversion efficiency. Through simulation, the Pancharatnam-Berry (PB) phase structure is effectively used to control the emission wavefront of both chiral and dipole emitters. One key characteristic for sensing applications is the enantiomeric interaction between chiral molecules and circularly polarized light. We use silicon disk metamaterials in conjunction with the P-B phase antenna to provide higher selectivity for real-time chiral sensing. It is also possible to enhance Circular Dichroism (CD) measurement. Experimental demonstration is conducted using L- and D-glucose.

Ultrafast nonlinearity which results in modulation of linear optical response is a basis for development of time-varying media, in particular those operating in the epsilon-near-zero regime. Here, we demonstrate that the intraband excitation of hot electrons in the epsilon-near-zero media results in the strong second-harmonic modification while the changes in linear transmission are negligible. We also show that nonlinear response of anisotropic epsilon-near-zero materials can be controlled by coupling to vibrational modes and influences the polarisation of the reflected light.

Nonlinear optical interactions are of fundamental significance for advanced photonic applications, but often the nonlinearity magnitude is insufficient. In the past decade, we apply laser scanning confocal microscopy, which is a routine tool in biology but unusual with nanomaterials, to inspect single metallic and semiconductor nanostructures. Via the combination of Mie resonance and coupled photothermal/thermo-optic effects, we discovered 1000- to 100000-fold enhanced nonlinear optical indices over bulk materials. The potential applications include all-optical switch and label-free super-resolution microscopy, based on suppression of scattering, saturation (sub-linearity) and reverse saturation (super-linearity). More recently, we uncovered novel light-matter interactions, such as optical bistability in nano-silicon with record-low Q-factor and footprint, as well as displacement resonance. The latter features that linear scattering efficiency is maximal when the focus is misaligned, thus showcasing a significant reduction of nonlinear response threshold, sign flip in all-optical switching, and spatial resolution enhancement.

Transition metal dichalcogenide (TMDC) monolayers are quantum materials with unusual optoelectronic properties. Strongly bound excitons in the material are particularly sensitive to many-body interactions in the atomically thin monolayer, dominating their optical nonlinearity. Hybridization of these excitons with light-like excitations, such as surface plasmon polaritons (SPPs), allows to dramatically alter the optical response and to tailor material properties on the nano scale . The role of excitonic many-body interactions for the new hybridized polariton states is of crucial importance. The ideal tool to investigate these interactions and their coherent dynamics is ultrafast two-dimensional electronic spectroscopy (2DES). Here, we report the first ultrafast 2DES spectra of a TMDC monolayer coupled to plasmonic nanoresonator array. We show that the coupling between excitons and plasmons large enhances the nonlinearity of the hybrid system, exceeding that of the individual exciton and plasmon subsystems by more than an order of magnitude. Our results demonstrate that many-body effects on the two-quantum excitations play a crucial role for this nonlinearity enhancement.

Polaritons are half-wave half-matter particles that emerge in resonant materials strongly coupled to electromagnetic waves. Their responses can provide highly effective tools to engineer light at the nanoscale, enhance nonlinearities and unveil new wave phenomena. Of particular interest is the role that they can play in the context of metamaterials and metasurfaces, as polaritons can provide new knobs to enhance light-matter interactions, and at the same time engineered metastructures can provide new opportunities to engage polaritons and make them useful for applications. In this talk, I will discuss our recent progress in the area of polaritonic metasurfaces, with an emphasis on polaritonics and its role in advancing the field of metamaterials and metasurfaces. Tailored material resonances, based on plasmons, excitons, phonons and/or electronic transitions, can be strongly coupled to electromagnetic waves in engineered metasurfaces, unveiling new degrees of freedom for the control of light-matter interactions, paving the way towards technological advances.

Mid-infrared (MIR) vibrational spectroscopy is a non-invasive and label-free analytical method; thus, it has become an essential technique for examining biological samples and tissues. Research has shown that this method, MIR spectral imaging (MIRSI), can identify various diseases with implications for enhanced biomedical tissue diagnostics. Nonetheless, the diverse chemical makeup of tissues and their spatial heterogeneity, combined with the innately weak interaction between infrared light and biological molecules, limit the efficacy of conventional MIRSI. We introduce a new chemical tissue analysis method that uses plasmonic metasurfaces enabling the detailed molecular mapping of tissue sections. The proposed surface-enhanced chemical imaging method using plasmonic metasurfaces has excellent potential for translational biomedical research and clinical histopathology.

We fabricated titanium oxide electrodes with nanocavity functionality and supported gold nanoparticles on them to form a strong coupling between localized surface plasmon resonance (LSPR) mode of the gold nanoparticles and the nanocavity mode. This resulted in successful absorption of a broad range of visible wavelengths. When using the electrodes with modal strong coupling, we observed an increased internal quantum yield of photocurrent generation using water as an electron source compared to plasmonic electrodes without nanocavity. Furthermore, we elucidated that the mechanism behind this enhancement involves quantum coherent interactions of multiple LSPRs via the nanocavity. Here, we report the use of metallic titanium as an adhesion layer between the nanocavity and gold nanoparticles, leading to an increase in electron injection into titanium oxide and provide further insights into the underlying mechanism.

Controlling the physical and electronic properties of materials through optics holds significant appeal for both foundational scientific exploration and the advancement of optoelectronic technologies. A natural progression involves scaling down devices to the nanoscale, necessitating a reduction in the volume of optical interactions to the nanoscale. Optical antennas, though capable of confining light, fall short due to the requirement of illuminating them with a diffraction-limited focal spot, resulting in unintentional illumination of the sample over a larger volume. In contrast, plasmon nanofocusing physically separates the illumination and the nano-light generation sites, enabling background-free and truly confined nano-light. Furthermore, being a non-resonant phenomenon, plasmon nanofocusing is wavelength-independent, allowing for the generation of nano-light across a broad spectrum of wavelengths or even a white nano-light, suitable for nanoscale multi-sensing and optical switching applications. This talk will cover the generation of background-free, wavelength-independent nano-light and its potential applications in nanoscale sensing and optical switching.

Bound States in the Continuum (BIC) refers to a class of exotic states that exist within the continuum energy spectrum but behave as if they were confined or bound. In this study, an electrically wavelength tunable BIC metasurface laser integrated with liquid crystal is demonstrated. The demonstration of this work can be used in various applications, such as optical communications, optical sensing and spatial light modulator device.

This talk explores the transformative power of deep learning (DL) in metasurface-based imaging systems. We will showcase how DL algorithms are pushing the boundaries of performance in different applications, including endo-microscopy, meta-miniscopy, and confocal microscopy. In endo-microscopy, we achieve high-resolution brain images with detailed vasculature within 0.1 seconds (50x faster) by combining DL networks with existing endoscopes. This significantly reduces image acquisition time and system complexity. For DL assisted meta-miniscope, the integration of DL models with a meta-miniscope facilitates the transformation of conventional bright-field images into edge-enhanced images with high contrast accuracy. This novel approach not only enhances image quality but also minimizes system complexity and processing times, thus opening new avenues for improved microscopy techniques. This talk will be of interest to researchers and developers in optics, bioimaging, and deep learning, to highlight significant advancements through metasurfaces with deep learning.

We develop a simple approach for designing high-quality quasi-bound states in the continuum (quasi-BICs) using all-dielectric asymmetry kite-shaped nanopillar arrays and investigated their third-harmonic generation (THG). By manipulating the asymmetric of the kite-shaped meta-atoms, the symmetry-protected quasi-BICs was excited showing a tunable resonant spectral profile between Fano and Lorentzian-lineshapes due to the interplay with the broadband magnetic dipole (MD) mode. The high quality-factor quasi-BICs renders a four order of magnitude THG enhancement in calculation and 46.4-fold THG in experiment. In addition, a hybrid system incorporating amorphous-silicon nanocubes and Indium-Tin-Oxide (ITO) film was developed to study the interplay among electric dipolar, quasi-BICs, and Epsilon-Near-Zero (ENZ) modes. The strong coupling between these resonances results in a Rabi splitting energy of 137 meV and also achieves a broadband THG enhancement in the fundamental wavelength range of 1100 to 1600 nm.

We showcase plasmonic metasurfaces employing silicon (Si) nanostructures tailored for deep ultraviolet (DUV) spectroscopy. Si exhibits plasmonic resonance owing to the photon-doping effect originating from interband transitions in the DUV range. Through careful design adjustments, our metasurface achieves strong field enhancement at ~260nm. We investigate potential applications of the reported Si void metasurfaces for surface-enhanced spectroscopy by leveraging the unique properties of our Si metasurface. This study expands the range of materials employed in DUV nanophotonics, unlocking opportunities across diverse fields such as biomedical analysis and nonlinear optics.

Using subdiffracted light from a nanoplasmonic resonator we demonstrate hot-spot nanoheating control of quantum operations at elevated temperatures via temperature-induced shifts of the transition energies of the individual qubits in and out of resonance with the near-field. This introduces a dynamical switch for optical quantum control, significantly elevating solid-state quantum information processing technologies towards higher temperatures.

Harnessing the unprecedented spatiotemporal resolution capability of light to detect electrophysiological signals has been the goal of neuroscientists for nearly 50 years. Yet, progress towards that goal remains elusive due to the lack of electro-optic translators that can efficiently convert bioelectronic activity to high photon-count optical signals. In this talk, I will introduce a novel active plasmonic approach for translating tiny electric field oscillations to large optical signals that can be wirelessly detected in the far field. Our nanoscale electrochromically-loaded plasmonic (nano-electro-plasmonic) antenna overcome the fundamental limitations of state-of-art microelectrode array technologies and enable massively multiplexed measurement of electrophysiological signals with single synapse resolution. We recently demonstrated multimillion-plex, high SNR, and subcellular resolution recordings of cell electrogenic activity, reflecting a technical capability well beyond the theoretical limits of state-of-the-art neuroelectrodes well into the 22nd century.

The control of heat at the nanoscale has attracted significant interest over the last decade due to its impact on the function and performance of nanophotonic devices with nanometric footprints. Here, we present a conceptually new approach whereby plasmon resonances in plasmonic nanostructures can be leveraged to create ultrafast nanoscale electric fields, arising from transient thermoelectric effects due to the presence of substantial temperature gradients across the nanostructures. We consider both metallic nanoparticles and nanostructured graphene as suitable platforms to engineer such ultrafast thermoelectric phenomena, and provide designing rules to generate and probe the associated ultrafast electric fields. Our work opens an enticing new direction for understanding photo-electron-phonon interactions and manipulating heat at the nanoscale.

Nanoparticles (NPs) of coinage metals such as Au, Ag, and Cu, have been predominantly researched for their intrinsic exhibition of localized surface plasmon resonance (LSPR) in the visible region. Alloy NPs containing these coinage metals have been used to control the LSPR wavelength, but most of them have face-centered cubic (fcc)-based crystal structures. Recently, we have achieved LSPR in the visible region with intermetallic compound NPs that do not contain coinage metals. The colloidal PtIn2 NPs with a C1 (CaF2-type) crystal structure can be synthesized by the liquid phase method. These NPs show LSPR at wavelengths akin to fcc-Au NPs. These findings dramatically expand the plasmonic nanomaterials library and will contribute to our understanding of the LSPR properties of intermetallic NPs.

Recent strides in plasmonics and nanophotonics have markedly advanced light emission technologies, effectively addressing the "green gap" in LEDs and enhancing UV emissions. Innovations like SiO2 thin film deposition on InGaN/GaN quantum wells and UV irradiation have repaired defects and significantly improved green light efficiency by reducing the quantum-confined Stark effect (QCSE). Similarly, employing surface plasmon resonance (SPR) on semi-polar GaN substrates has boosted internal quantum efficiencies, presenting a solution to the green gap by enhancing photoluminescence. Additionally, SPR-induced photoluminescence enhancement in CdSe/ZnS quantum dots points to potential advancements in RGB display technologies. In UV emission, techniques such as nanostructuring and localized SPR have led to notable enhancements, especially with Ga2O3 and ZnO structures treated with metal films, showcasing the effectiveness of plasmonic effects in emission enhancement. These developments signal significant progress in semiconductor optics, promising more efficient, powerful, and versatile optoelectronic devices for a range of applications, from lighting to advanced displays.

This talk will discuss three routes to realizing nanoscale chiral structures. The first part will discuss controlling circularly polarized photoluminescence from patterned light emitters near plasmonic nanostructures, and how the spatial position of the pattern affects polarization state and photoluminescence intensity. The second part will discuss large-area, scalable, additive patterning techniques for metamaterials that are roll-to-roll compatible. The third will discuss plasmonic structures formed from block copolymer templates, and processing routes that lead to tunable circular dichroism.

A conventional quantum eraser involves physical double slits or virtual paths, such as orbital angular momentum, and has been demonstrated to probe the wave-particle duality of light in the quantum optical regime. Here, we extend the concept of the quantum eraser to holographic applications through a geometric-phase metasurface. In this case, we mark hologram paths with polarization using an entangled photon pair. As a result of a quantum holographic eraser, we demonstrate selective erasure of specific hologram regions with various inserted erasers as a visual manifestation of restoring interference. Our work extends the application of metasurfaces in investigating fundamental concepts, including entanglement, non-locality, and the role of information in quantum optics.

Organic-inorganic metal-halide perovskites have gained significant prominence in the fields of photovoltaics, light-emitting devices, and sensors, attributed to their exceptional optical properties and superior semiconductor characteristics. Furthermore, their versatile nature has recently unveiled a new dimension of functionality - piezoelectricity. This intriguing property allows these materials to convert mechanical deformation into an electrical response and vice versa, presenting promising opportunities in diverse applications such as miniaturized self-powered sensors and energy harvesting systems.

In this work, we designed and fabricated high aspect ratio vertical plasmonic nanostructures geared towards gas sensing using infrared absorption. The structures have inner and out Au walls with an aspect ratio of 18.3 and 16.7, respectively. The gap between the walls is partially filled with SiO2. From finite-difference time-domain simulations, we found that the initial resonance frequency of the entire structure is dictated by the overall height of the inner Au walls, while the SiO2/air ratio at the gap can further tune the resonance frequency. This is experimentally demonstrated through the observed Fourier transform infrared measurements.

Optical and acoustic metasurfaces have been extensively studied for wavefront shaping, including lensing, beam steering, and holography. This work aims to explore a new field of acoustoplasmonic metasurfaces that utilize the photoacoustic effect in gold nanoparticles to generate high-frequency acoustic waves via optical excitation. We leverage the extreme polarization-dependence of absorption efficiency in nanoellipsoids to introduce acoustic wavefront tunability, which opens the door to applications in super-resolution acoustic imaging.

Selective modulation of both visible and near-infrared (NIR) radiations are looked for advanced energy efficiency fenestration solutions. Smart windows made of highly doped metal oxides (ITO, AZO, or WO3-x vacancies) are of peculiar interest due to the possible electrochemical modulation of the localized surface plasmon resonance (LSPR) of the associated nanocrystal in the NIR. In this context, oxygen-deficient molybdenum-tungsten hybrid oxides (MoWOx) displaying a very strong LSPR signal astride visible and NIR regions [1] are good candidates for novel electrochromic formulation. The goal of this presentation is twofold: on one hand present two MoWOx formulations compared to their respective parents WOx oxides via comparative TEM, EDX, XRD, XPS and spectroelectrochemical characterizations and on the other hand analyze the plasmonic character of those emerging oxides. For the latter, we thoroughly investigated the use of the Kubelka-Munk formalism in plasmonic configurations. We derived an analytical model respecting all the required hypotheses of the formalism. Our model fully describes the plasmonic properties of metal oxides, consistently with experiments on ITO and MoWOx.

Meta-lenses are advanced flat optical devices composed of artificial nanoantenna arrays. It manipulates the wavefront of light with the advantages of ultrathin, compact, and no spherical aberration. We have developed a series of intelligent machine vision systems with binocular meta-lens for the novel applications of particle image velocimetry (PIV), underwater stereo vision, edge-enhanced depth perception for ill-posed regions, and assisted driving vision. Meta-lens PIV demonstrates a new development trend for the PIV technique for rejuvenating traditional flow diagnostic tools toward a more compact, easy-to-deploy technique. A novel stereo-matching neural network, H-Net, was proposed to derive the disparity information, which incorporates the cross-pixel and cross-view interaction operations. The developed machine vision systems facilitated underwater imaging and assisted driving vision. With binocular meta-lens, multimodal perceptions are provided for machine vision systems in various novel applications.

We show spontaneous symmetry breaking (SSB) in a nonlocal metasurface laser. The system is a hexagonal plasmonic distributed feedback laser that lases at the six K-points in momentum space, or more exactly at the K and K’ modes. A unique properties is that these modes are exactly degenerate in both spatial distribution and energy. By simultaneous real-space and Fourier-space measurements, we map both the relative amplitude (parity symmetry breaking) and phase (rotational symmetry breaking ) of the two symmetry-broken modes. Our results open new perspectives on studying SSB and emergence of spatial coherence in photonic systems.

Photothermal PCR, which exploits the photothermal conversion effect based on the plasmonic absorption resonance of metal nanoparticles, has garnered significant attention for its capacity to enable rapid diagnosis. Through the addition of gold nanoshells, known for their high photothermal conversion efficiency in the near-infrared region, to the PCR mixture, we achieved photothermal quantitative PCR while simultaneously conducting fluorescence measurements during the photothermal PCR cycle. Our photothermal quantitative PCR method expeditiously amplifies Lambda DNA while preserving its detection sensitivity, successfully amplifying the target DNA within just 25 minutes and detecting a minimum of 50 picograms of DNA. Furthermore, we demonstrated the versatility of photothermal quantitative PCR by applying it to genomic DNA extracted from Salmonella, showcasing its effectiveness with long base pairs. By leveraging the photothermal properties of gold nanoshells, our innovative approach to photothermal qPCR will pave the way for point-of-care diagnostics of nucleic acid biomarkers.

Surface lattice resonance (SLR) lasers are promising for optical communication, optical computing, sensing and LiDAR applications. They have previously shown large-area single-mode emission with low threshold as well as tuneable spectral and angular emission using plasmonic nanoparticles embedded in thin film gain media. We demonstrate a novel device architecture with solid-state epitaxial InP gain medium that coupled to a gold nanoparticle array via a thin SiO2 layer. These plasmonic nanoparticles form SLRs that weakly couple to the InP waveguide mode forming a plasmonic-photonic hybrid mode supporting single-mode lasing with low thresholds. We experimentally and theoretically characterise the system. Our devices show no photobleaching. Combining plasmonic SLRs with epitaxial gain media paves the way for large-area on-chip integration of SLR lasers.

Glass matrices doped with rare earths and Cu were synthesized using copper concentration as the control parameter. The amorphous phase of lithium borate was corroborated by X-Ray diffraction (XRD) while size distribution of Nanoparticles was obtained by transmittance electron microscopy (TEM) and crystal phase of Cu nanoparticles was obtained by high resolution transmittance electron microscopy (HRTEM). For photoluminescence, characterizations used were absorbance, photoluminescence emission (PL) and experimental decay times; from the data obtained we performed Judd–Ofelt analysis. With absorbance and PL characterizations in conjunction with CIE 1931, efficiency and shift to white light emission were evaluated. The insights gained from this study have significant implications for future research focused on enhancing the photoluminescence properties of rare earth-doped systems. A comprehensive understanding of the underlying mechanisms behind these phenomena enables us to leverage plasmon effects in similar systems, leading to diverse applications such as color tuning emission.