Keynote: Picophotonics is the emerging science of interactions of picometer-scale objects and events with light. We demonstrate dimensional metrology and detection of change in position over time with resolution on nanometric to picometric scales by analyzing scattering of electrons or topologically structured light from the nanostructures using artificial intelligence. We show how these techniques can be applied to characterization and optimization of nano-opto-mechanical metamaterials and to fundamental studies of the dynamics of thermal motion and the physics of phonons in photonic nanostructures.

We have studied dispersion of surface plasmon polaritons (SPPs) in the Kretcshmann’s geometry (prism/Ag/dye-doped polymer) in weak and strong exciton-plasmon coupling regimes. In reflection, the dispersion curves were in a good agreement with simple model predictions at small concentrations of the dye (R6G) in the polymer (PMMA). At the same time, highly unusual multi-segment ladder-like dispersion curves were observed at large dye concentrations. To describe this behavior, we upgraded the theoretical model taking into account strong exciton-plasmon coupling. The dispersion curves obtained in emission experiments were strongly different from those in reflection and did not seem to be affected by the strong coupling.

While multipoles expansions have become ubiquitous in the analysis of plasmonic and dielectric nanostructures and metasurfaces, their zoology remains quite complex. Depending on the physical system, it appears that different multipoles families – including somewhat exotic toroidal multipoles – are required to compute the response of the system. In this work, we present a facile derivation of the three multipoles families: the Cartesian primitive multipoles, the Cartesian irreducible multipoles and the spherical multipoles. We illustrate the links between them and demonstrate their utilization in practical situations to guide experiments.

We discuss about metallic and dielectric metamaterial for ultra-sensitive infrared spectroscopy. Experimental and theoretical studies of broadband metallic metamaterial absorber and its application for infrared spectroscopic molecules sensing are demonstrated. We made three-dimensional vertical-oriented metal-insulator-metal (v-MIM) metamaterial absorber and successfully detected 20 ppm concentration of carbon dioxide and butane molecules with negligible background noise. Besides metallic metamaterials, dielectric metamaterials have also attracted many attentions for spectrometer-less infrared absorption sensors. Owing to the lossless properties of transparent dielectric materials and its capability of confining and enhancing optical fields, it can create ultra-high Q-resonance and it enhances the molecular signals. However, due to the narrow band properties, multiple resonators array is necessary for the spectral measurements. In this talk, we would like to discuss advantage and disadvantage of metal and dielectric metamaterials for spectroscopic applications.

This talk will discuss our recent work on optical phenomena and electronic phenomena in 2D semiconductors when they are placed in close proximity on plasmonic substrates such as Au, Ag and Al. I will also show how using a plasmonic tip once can use near-field tip based micro-spectroscopy to probe defects, interfaces, strain and hybrid states in 2D excitonic semiconductors and junctions. If time permits, I will also present how 1D nanostructuring of MoS2, WS2, WSe2 etc. into nanophotonic dielectric gratings can enable exploration of new regimes of light-matter confinement including formation of hybrid exciton-plasmon-polariton states. I will extend this concept to 2D hybrid perovskites and superlattices.

Two all-optical, real-time approaches utilizing plasmonic metasurfaces for manipulating images to enhance phase contrast are presented here. One employs the phenomenon of directional light ‘routing’ in a waveguiding layer while the other relies on the inherent angular sensitivity of plasmonic resonant waveguide gratings. We show that by introducing an asymmetry into the optical transfer function by either controlling the coupling into the waveguide using circularly polarized light, or tilting the device relative to the optical axis produces pseudo-three-dimensional phase contrast images of unstained biological cells and wavefront phase variations.

Recent advances in wavefront shaping have enabled new classes of structured light, leading to new phenomena and applications. We review current progress in these areas with focus on meta-optics that exhibit a tunable response at the output by simply changing the properties of incident light; including input polarization, orbital angular momentum, angle of incidence, and/or wavelength. Multifunctional devices of this kind rely on intricate light-matter interaction at the level of meta-atoms which can be difficult to replicate using other wavefront shaping tools. In addition, we present a new class of holograms — dubbed holographic light sheets — for generating 3D structured light and discuss its potential use in AR/VR applications. Lastly, we highlight new directions in generating time-varying optical vortices using dispersion-engineered metasurfaces and discuss its future applications.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

The ability to monitor the effects of external stimuli, such as drugs and other compounds, on a living cell, is of great interest for life sciences. It is especially desirable to do this all-optically and without introducing any external labels. I will describe such an experimental technique developed in our lab – Metasurface-Enhanced Infrared Reflection Spectroscopy (MEIRS) of live cells – that we have used to interrogating the effects of various chemical compounds (including chemotherapeutics) on cellular membranes and cytoskeleton. The prospects for expanding the scope of MEIRS to high-throughput drug screening will be discussed.

Self-assembled monolayer composed of metal nanoparticles is regarded as a metasurface that has high refractive index and extinction coefficient due to collective excitation of coupled LSPR. This plasmonic metasurface which confines light at the nanointerface and enhanced fluorescence allows a high-speed interfacial imaging with high axial and lateral resolution down to theoretical limit. In this presentation, we will report unique cell dynamics as “early molecular events” at the cell attached nanointerface using this imaging method.

In this presentation, a new type of etalon for ultrafast colorimetric vapor sensor is introduced. The etalon consists of reflector, vapor-responsive hydrogel layer, and disordered plasmonic nanoparticles. This etalon presents dramatically fast gas-responsive time (~ 0.1s) because the disordered nanoparticles with certain ligand can form membrane pores smaller than the mean free path of penetrating gas. Among several candidates, thiocyanate ligand that provides optimized temporal and optical properties as effective medium is chosen. As a demonstration, the disordered nanoparticle-based etalon is applied to ultrafast humidity-responsive structural colors and an image sticker that instantaneously changes the displayed image to external humidity.

Photonic materials that derive their properties from periodicity can show analogous properties to their electronic counterparts. However, the special scattering properties of plasmonic nanoparticle lattices offer prospects for exceptional optical properties that cannot be found in electronic materials. This talk will describe two examples of extraordinary light scattering: (1) direct observation of photonic Brilluoin zone edges; and (2) ultra-long-range coupling between plasmonic nanoparticle lattices. Using dye molecules as local dipole emitters to excite and probe the optical modes, we will discuss how high-order Brilluoin edges, high-symmetry points, and moiré effects in plasmonic lattices can be revealed by directional lasing emission.

Squeezing light into deep sub-wavelength volumes or even into few-nanometer gaps has led to the investigation of interesting phenomena, including strong coupling, quantum plasmonics, nonlinearity enhancement, nonlocality, and molecular junctions. Bowtie nanoantennas, as a common configuration for plasmonic nanocavity, have been extensively studied owing to their great enhancement of the localized field. The enhancement rapidly increases as the tips become sharper and the gap becomes narrower. However, every effort paid to increase the extreme sharpness and nanometer precision of less than 10 nm gaps result in the downfall of fabrication throughput, since it relies on the probability of achieving one satisfactory piece out of the many fabricated. Here, an intuitive “fall-to-rise” schemes are proposed and experimentally validated using cascade domino lithography (CDL) and capillary-force-induced collapse lithography (CCL). In this report, we successfully establish a controllable lithography method of making extremely sharp bowtie-shaped plasmonic nanocavity with sub-1nm radius curvature reaching the size of a gold nanocluster as well as a single-digit-nanometer gap between such sharp tips. By controlling falling mechanisms of photoresist mask structures, a facile route to fabricate sub-10 nm plasmonic nanocavity with high yield is provided. In addition, a proof-of-concept application in surface enhanced Raman spectroscopy (SERS) is demonstrated. The numerically calculated intensity enhancement is over 2.2×10^4 with the confined mode volume below 7.14×10^-6 λ^3, the measured average Raman enhancement factor is of the order of 10^6 with the calculated local Raman enhancement factor over 10^8 promising for single-molecular level sensing applications. Furthermore, such sharp plasmonic nanocavity is used to probe and control localized excitons at room temperature, which offers new strategies for active quantum nano-optical devices. Atomically thin semiconductors, WSe2, are coated on top of plasmonic nanocavity and Au tip for tip-enhanced photoluminescence (TEPL) spectroscopy is added to induce tensile strain in the nanoscale region to create robust localized exciton at the hotspot region. Such an approach provides a systematic way to control localized quantum light. This controlling mechanism of nanostructures falling opens up an unexplored gateway towards conquering the limitations of exploring the realm of plasmonics down to the sub-nanometer regime.

The confinement and the enhancement of optical fields in the vicinity of metallic or dielectric nanostructures provide versatile applications in nanoscale devices and spectroscopies. It is therefore of great importance to investigate optical properties of nanostructures, such as the distribution of optical fields on the nanometer scale. In this work, we visualized the nanoscale distribution of optical fields induced by metallic and dielectric nanostructures in visible and infrared region, respectively. We utilized enhanced vibrational spectroscopies, such as a mid-infrared photothermal microscopy technique and a tip-enhanced Raman spectroscopy-based technique to study optical fields of nanostructures at the nanoscale.

Ultrafast modulation of the dielectric permittivity of materials has made great strides in the past decade, resulting in practical applications such as beam-steering, and the realization of novel physical phenomena such as time refraction. Control over the dynamics of permittivity modulation adds an additional degree of freedom in tunable optics, broadening the scope of applications. In this presentation, we report our work on controlling the dynamic optical properties of transparent conducting oxides for a wide array of nonlinear optical demonstrations. We show large changes in the epsilon-near-zero points in undoped zinc oxide, with 20ps response time, and utilize the permittivity modulation to enhance the third-harmonic generation, and develop optically controlled polarization switches. With TiN-AZO Berreman-metasurfaces, we demonstrate wide tuning of the switching times varying from picosecond to nanosecond timescales. Employing the rapid permittivity modulation in aluminum-doped zinc oxide, we demonstrate time refraction in ENZ films. Our work will develop a better understanding of nonlinear optics employing ultrafast permittivity modulation at adjustable speeds, heralding the way to further novel optical phenomena such as photonic time crystals.

Among all the platforms studied for integrating emitters in photonic devices, 2D materials are one of the most promising for on-demand single-photon sources (SPSs) because of their exceptional flexibility and unique optical response which has opened the way to employ mechanical deformation for engineering their physical properties. It has been theoretically proven that excitons can also be trapped by defect potentials as single-photon emitters in TMDCs monolayer, making defect engineering a promising approach to realize on-demand SPSs. Our findings reveal artificially engineering planar materials (metasurfaces) as the optimal electromagnetic environment to generate, control and manipulate SPSs from atomically thin layers.

Over the last two decades, the ability to achieve well-defined size, geometry, and distribution of plasmonic structures has extensively been studied. Here, we introduce a unique strained induced self-rolling fabrication technique suitable to fabricate three-dimensional multilayer thin film-based plasmonic devices. The photoresist-based technique enables the fabrication of nanohole arrays on SiO2/Au-based rolled-up tubes (RUTs). The curved nature of the tube allows the fabrication of an out-of-plane metasurface that can effectively control the light compared to the common planar counterparts.

Blackbody radiation is intrinsically isotropic, broadband and unpolarized. However, these properties can be strongly modified using appropriate nanostructures. Here we report about the design, fabrication and characterization of an incandescent metasurface, emitting circularly polarized light in the MWIR domain, around 4.7 microns. Our device consists of a three-layer structure, where the top surface is paved with a subwavelength metallic grating following a chiral pattern. The system geometry is engineered to optimize the circular dichroism in absorption. When heated by Joule effect, the grating acts as a thermal emitter providing circularly polarized light with a polarization degree around 35%.

Metal nanostructures are very lossy when they interact with light, which hinders their use in optics and photonics requiring sharp resonances. Here, we will show that employing the physics of bound states in the continuum (BICs) in all-plasmonic metasurfaces can significantly reduce/eliminate the dissipation/radiation loss in metal nanostructures, resulting in high quality-factor (Q-factor) resonances. Also, we will show that butterfly-wings-inspired plasmonic structures can support high-Q surface lattice resonances under focused light excitation. These results allow for various applications requiring compact footprint with strong-light matter interaction in nanoscales, such as lasing and quantum detection.

In this talk, I will present our recent development on the “Meta”-optical fiber integrated with optical metasurfaces and plasmonic nanostructures. I will present the development of ultrathin optical metalens cascaded on the facet of a photonic crystal optical fiber that enables light focusing in the telecommunication regime. The development of the ultrathin optical fiber metalens and color filter for potential laser surgery and medical imaging endoscope applications, excitation of ENZ and plasmonic resonances on holey optical fiber for advanced optical/bio sensing, novel in-fiber laser and tip-enhanced Raman molecular spectroscopy will be discussed. The integration of an metalens/plasmonic nanostructures and optical fiber will open the path to revolutionary ultracompact in-fiber optical devices for optical imaging, sensing, and fiber communication and laser applications. The authors acknowledge the supports partially by the Air Force Office of Scientific Research (AFOSR, Award number: FA9550-21-1-02204).

Optical vector field topologies will be discussed on the example of plasmonic systems and anisotropic metamaterials. An anisotropic metamaterial platform for local control of polarisation in complex vector beams, including radial and azimuthal beams, will be presented. The approach enables a flexible platform for tailoring complex vector beams and achieving required polarisation patterns on demand for harvesting functionalities and applications of complex light beams with complex polarisation and phase information in numerous photonic and quantum technologies, imaging and metrology.

Transition metal mononitrides (TMNs) like ZrN—which shows uniquely and drastically chemically tunable properties such as permittivity, carrier concentration, structure, hardness, and heat capacity—have arrived as frontrunner plasmonic and nonlinear optical material alternatives to Ag and Au. The influence of dopant atoms and defect states on the permittivity and structural properties in ZrN chemistries, as well as a broadband epsilon near zero (ENZ) regime spanning the visible wavelength range and into the near infrared are demonstrated. Reasons why progress in ZrN (despite its attractive features) lags that of TiN are discussed and related to defect and impurity states in precursor materials.

Optical metasurfaces – artificial materials composed of an array of subwavelength nanoresonators, have recently received extensive attention for their ability to enhance light-matter interaction and provide complete control of light at the nanoscale. In our work, we show how random Mie-resonant metasurfaces benefit the generation of nonlinear optical harmonics since they provide required electromagnetic field enhancement and potentially improve the nonlinear signal collection efficiency compared to the periodic metasurfaces with equivalent nanoresonator dimensions that guide newly generated light into diffraction orders.

In this talk, we report a large-scale fabrication of Mid-IR metasurfaces by using a newly developed method. The metasurfaces were produced on transparent alumina membranes. Functionalities such as quasi-bound-state-in-the-continuum (quasi-BIC) resonances, mid-IR focusing, and polarization control were realized in different dielectric metasurfaces. Metasurfaces comprising aluminum nanoantennas were also fabricated and integrated into microfluidic devices for biosensing. The reported fabrication method is CMOS compatible and able to produce metasurfaces over whole Si wafers with high precision and uniformity. This work serves as a significant step in the direction of practical applications and commercialization of Mid-IR metasurfaces [Adv. Mater. 33, 2102232 (2021)].

Two-dimensional hexagonal boron nitride (hBN) has emerged as a promising platform for quantum applications as a host of a plethora of quantum emitters (QEs), including optically active spin defects. It is critical to achieve position-controlled generation of these QEs and their integration with photonic/plasmonic structures. In this work, we demonstrate a novel method to deterministically create single QEs in hBN by nanoindentation with atomic force microscopy, with a yield of >30% for various indent sizes. Furthermore, we also demonstrate a route to enhance the brightness of spin defects in hBN up to 120 times by coupling them with nano-patch antennas.

Depositing energy into a target region deep inside an opaque system by controlling random wave scattering is essential in a wide range of applications. While multiple scattering of light results in a diffusive spread of the wave energy, controlling the incident wavefront of a coherent beam enables the suppression of wave diffusion and the delivery of energy deep inside disordered systems. We conduct experimental, numerical and theoretical studies to reveal the physical mechanisms contributing to energy deposition across an extended target inside a diffusive system, and also find the fundamental limit of energy enhancement using the wavefront control method.

We present a concrete proposal for such response directly from experimental measurements of electron energy-loss spectroscopy (EELS) and cathodoluminescence (CL). Our scheme exploits the ability of free-electron beams to produce deeply subwavelength near-fields and thus probe the optical response of metals at the nanoscale (i.e., where quantum effects can become important). Chiefly, we demonstrate how our theory can be employed towards a quantitative measurement of the quantum nonlocal response of metals [specifically, the surface-response functions d⊥(ω) and d∥(ω)] from the nonclassical features imprinted in the EELS and CL spectra. Notably, the quantitative knowledge of material’s quantum surface-response of metals is ought to be crucial for designing nanodevices with few-nm footprint and to engineer maximal light–matter interactions at the nanoscale.

Strong coupling between an atom and a cavity is the foundation of quantum photonic devices, which are hard to be integrated into a microchip due to the alignment. Here, DNA strands are used to construct a nanocavity and simultaneously integrate a few fluorophores to form a strong coupling unit. This method produces high cavity yield and strong coupling yield. Combination of this method with e-beam lithography can further position strong coupling units on a specific location of a microchip. The detuned polariton energy can fit into three sets of two-level systems, which means vibronic modes may involve the strong coupling.

A metamaterial is an artificial material that works as an antenna that absorbs thermal radiation emitted from the surrounding medium and a transducer that converts the absorbed energy into local heating. The metamaterial absorber surface has a ultra-thin structure comparing to that of the incident wavelength, while it shows extraordinary absorption properties. We demonstrated the conversion of thermal energy into electricity through metamaterial thermoelectric conversion technique based on thermal radiation absorption by the metamaterial. The metamaterial thermoelectric conversion is a technique that generates electricity by extracting thermal energies from the surrounding medium. The metamaterial thermoelectric devices will pave the way to recover waste heat existing in the medium, such as air and water. However, similar thermoelectric conversion might be realized by other broadband absorber such as the carbon black. Here, we compared the ability to generate local heating of the metamaterial and the carbon black film to clarify the superiority of the metamaterial as an absorber and a transducer.

Due to their tunable light absorption characteristics and ability to generate hot carriers, plasmonic-metal nanostructures offer unique opportunities for light energy harnessing and conversion devices, from photodetectors to photoelectrochemical cells. In this talk I will show the importance of highly controlled experiments and high-quality materials for understanding and realizing plasmonic hot carrier devices. In particular I will present our recent effort in the synthesis and applications of monocrystalline plasmonic structures.

We will present a selection of disordered and hybrid plasmonic systems for broadband energy harvesting and conversion in a context of photocatalysis. Firstly, disordered plasmonic nanoparticle arrays coupled to an underlying Fabry Perot cavity show a material-independent light harvesting response, enabling the decoupling of the far-field light collection behaviour and local near-field enhancement. Specifically we elucidate how cluster-deposited highly disordered systems made out of a variety of different metals (Au, Ag, Pt) show the same far-field reflection profile determined solely by the resonance wavelength of the underlying cavity, enabling efficient light harvesting in hybrid systems composed of plasmonic and catalytic metal nanoclusters. Secondly, we will examine hybrid plasmonic nanoparticle assemblies for efficient conversion of photon energy into energetic charge carriers for photocatalysis.

In this work, we studied the Raman spectra characteristics, strain distribution and carrier concentration of monolayer graphene wrinkles on a Au(111) crystal facet using tip-enhanced Raman spectroscopy (TERS) in ambient. G-band splitting was observed in certain areas of the wrinkle indicating the presence of anisotropic strain. A broad background was also observed in the near-field spectra that is hypothesized to be electronic Raman scattering originating from the graphene monolayer and the Au(111) substrate. Hence, careful spectral analysis must be done since this broad background potentially contains information on the sample.

To enhance the Raman scattering efficiency of light by molecules, various techniques relying on either stimulated or surface enhanced Raman scattering (SERS) have been developed. But they are either limited by the poor control of the scattered light, narrow bandwidth of the resonance frequency, or restricted area of field enhancement. Here we present a unique waveguide approach to achieve broadband enhanced Raman scattering of molecules with precisely controlled propagation direction. We demonstrated 99% of the Raman photons can be coupled into the waveguide. The near unity couple efficiency is due to the largely enhanced spontaneous Raman scattering rate in waveguide.

Various optical device applications of surface plasmon (SP) resonance have been reported, in particular, we have discovered that plasmonics can significantly improve the emission efficiencies, and applicable to high-efficiency light-emitting devices. In order to develop efficient plasmonic LEDs at a practical level, tuning the SP resonance wavelength is one of the most important issues as well as device development. We present a new plasmonic metamaterial based on random nanostructures that can be fabricated easily, inexpensively, and over a large area by a bottom-up approach and enable tuning of the SP resonance in the deep ultraviolet and near infrared wavelength regions.

Tip-enhanced Raman scattering (TERS) microscopy has been regarded as a promising application of plasmonics for nano-imaging and nano-analysis with a nanoscale spatial resolution far beyond the diffraction limit of light. However, TERS microscopy has been still limited to passive measurement of intrinsic molecular properties and functions. Here, we demonstrate active TERS microscopy in association with the local external stimuli, enabling to reversibly control chemical reactions in the vicinity of a plasmonic tip. The active function in TERS microscopy opens up a new approach to actively control molecular properties and functions at nanoscale.

We realize nanoantennas from metallic polymers which show well-pronounced plasmonic resonances and can be electrically switched fully off and back on at video-rate frequencies of 30 Hz by applying voltages of only ±1 V. Utilizing this concept, electrically switchable beam steering metasurfaces with 100% contrast ratio in transmission are demonstrated. Furthermore, electrically controllable metalenses with switchable focal length are presented.

Laser communications hold the potential to bring internet-like speeds (exceeding Gb/s) to data transmission in space. One of the major challenges of the laser communications is the necessity to accurately direct narrow beams. In the present talk, we discuss how electrically reconfigurable active metasurfaces can address this challenge. We perform an optical link budget analysis and discuss how the link range can be extended by increasing the aperture diameter or the input optical power. To assess maximal available output powers from realistic metasurface-based apertures, we experimentally probe the gate-tunable performance of indium tin oxide (ITO)-based active metasurfaces upon high-power illumination.

Photonic metasurfaces—two-dimensional arrangements of resonant nanoparticles with designer optical responses—have emerged as a game-changer in the field of flat optics. However, most metasurfaces exhibit fixed properties after fabrication, and adding tunability expands vastly the scope of the metasurface use scenarios. Here, we review our recent results in metasurfaces tunable at various time scales, from seconds to femtoseconds. We start by using liquid crystals as switching agents for metalenses with electrically actuated focal spots at low (< 10 V) voltages and high focal spot tunability. The second part of the talk demonstrates pico- and femtosecond-scale tuning in semiconductor metasurfaces that provide an ultrafast platform for all-optical information processing. Finally, we outline the potential use of tunable metasurfaces in polarization synthesizers, nonlinear and quantum optics, and frequency conversion on demand.

We report recent studies of integrated plasmonic devices for nano-focusing and nano-defocusing, capable of drastically enhancing interactions between light and matter. Our approach is based on gap plasmonic waveguides, which enable efficient photonic-to-plasmonic mode conversion. Here, we demonstrate metallic components that focus light to a 10 nm scale and explore how linear and nonlinear processes are enhanced. We will initially discuss how to achieve low-loss conversion from photonic-like states to plasmonic gap modes. We will then focus on new studies that evaluate the enhancement of nonlinear frequency mixing, spontaneous emission and Raman scattering, all occurring at the nanofocus in these devices.

Optical meta-devices using metasurfaces have shown preeminent capabilities to control the optical nonlinearity and enhancing the nonlinear efficiency by arrangements of meta-atoms. With the great advantages of relaxed phase-matching requirements and CMOS compatibility for mass production, nonlinear metasurfaces can flexibly manipulate the phase, amplitude and polarization of the nonlinear waves at subwavelength scale. Various nonlinear frequency conversion processes, such as second harmonic generation (SHG), third harmonic generation (THG), have been widely realized to short wavelength such as vacuum ultraviolet (VUV) light and applied in optical communication, imaging, photochemistry and biosensing. The design, fabrication and application of the novel nonlinear optical meta-devices are reported in this talk.

Recent advancement in the fabrication of metallic thin films allows for precise control of the surface crystallographic orientation and thickness, making them a great appeal in plasmonic devices. Considering such a crystalline quality and going towards smaller optical designs; surface, nonlocal, and quantum finite-size effects play a major role in metallic thin films when interacting with light. Here we explore various strategies to seek for the linear and nonlinear optical response manifested in multiple scenarios and configurations based on precise quantum-mechanical formalisms that describe the dynamics of electrons in such films, e.g., EELS, Feibelman d-parameters, periodic- and finite-systems, etc. We believe that our results can inspire future devices based on crystalline metal films as well as motivate further numerical implementation strategies.

Photon- and plasmon-induced hot carriers dominate the ultrafast response of metallic nano- and heterostructures and determine the efficiency of fundamental processes in photochemistry and light-harvesting. Here, we introduce our new approach to disentangle the dynamics of plasmon- and photon-induced hot carriers at metal surfaces by combining time-resolved two-photon photoemission electron microscopy and momentum microscopy. In this way, we can disentangle the momentum space signatures of plasmon- and photon-induced hot carriers of gold flakes by their respective spatial and temporal dynamics. In addition, we will discuss the tuneablity of the ultrafast photon-induced carrier dynamics of metallic bilayer systems in momentum space.

Scanning probe technology is advantageous in visualizing nanoscale light-matter interactions, however, this technology is limited by the slow raster scanning speed. In this talk, I will discuss how to visualize these ultrafast interactions beyond the conventional scanning speed. We develop a technique called decoupled optical force nanoscopy that can differentiate optical forces with different origins.

Miniaturization of optical spectrometers has recently drawn a lot of attention due to the increasing needs of portable characterization systems for scientific, industrial, and consumer applications. At the same time, smartphones have technically evolved to become an everyday, ubiquitous device that provides numerous useful applications to consumers. Combining optical spectrometer and smartphone could lead to an explosion of new applications, especially in healthcare, biometrics, and food inspections, and change our daily life, making it more convenient, independent, and hyper-personalized. In this work, we have developed a smartphone spectrometer in the visible and near infrared (NIR) ranges by directly integrating a 2 dimensional periodic array of band-pass filters on top of the smartphone’s image sensor. Each band pass filter is a silicon resonator consisting of a pair of Si/SiO₂ distributed Bragg reflectors (DBR), where each resonator’s transmitting wavelength is set by adjusting the thickness of the center Si layer. The DBR contains alternating, vertically-stacked TiO2 and SiN films with variable thicknesses while the top and bottom of the DBR were made of Al and Cu or Al reflectors for the visible and NIR ranges, respectively. The fabrication process was completely CMOS-compatible. Using this smartphone spectrometer, we have proposed the concept of artificial-intelligence-powered spectral barcode for material identification and successfully demonstrated its use in drug identification. The accuracy of correctly identifying the type of drugs was ~99%. In addition, the smartphone spectrometer has also proven to correctly distinguish beef into three different classes according to the freshness.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XX conference at SPIE Optics + Photonics 2022.