This PDF file contains the front matter associated with SPIE Proceedings Volume 12648, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Laser processing technology provides an effective means of controlling the colors of plasmonic metamaterials across large areas with micrometer resolution, allowing for the printing of images with structural colors that are visible to the naked eye. Despite the inhomogeneity in size and spatial distribution of metallic nano-objects inherent to the laser process, the colors generated are highly reproducible and can exhibit unique visual properties due to collective resonances that add to the localized surface plasmon resonances (LSPR). Here we investigate the effect of inhomogeneity in size and position on the surface lattice resonances that strongly contribute to the strong dichroism observed in laser-induced sself-organized metasurfaces. By exploiting the dichroic properties of these structures, we have successfully implemented two- and three-image multiplexing using direct laser printing techniques. These results demonstrate the potential of nanosecond laser processing for high-end anticounterfeiting applications. By combining our experimental findings with advanced computational approaches, we aim to advance the creation of even more complex and sophisticated images with enhanced optical properties.

A periodic array of nanoparticles scatters electromagnetic waves in different diffraction orders, and such periodic arrangements of nanoparticles result in significant field enhancements compared to a single nanoparticle. We investigate multipole Mie resonances in MXene antennas, uncovering absorption enhancement, reflection suppression, and phase variation through analytical models, simulations, and experiments. We study lattice resonances of lossy materials, such as transition metals nickel, titanium, and tungsten, as well as metalloid germanium. We study the impact of substrate and superstrate on Rayleigh anomaly dependency, showing that the resonance peak shifts according to the surrounding medium refractive index. Exploiting these resonances can enable metasurfaces for efficient, broad-spectrum light absorption in large-scale sensing, photodetectors, and energy harvesting applications.

In this work, Au nanoparticle clusters are formed at nanoscale, covered by a polymer shell and decorated with CdS/CdSe QDs. The polymer layer serves as an insulator to prevent the fluorescence quenching. The variations in the density of photon states in similar disordered structures are analyzed through changes in the transition rates of the light emitters interacting with the hotspot regions. The localized surface plasmon modes are demonstrated to significantly alter the density of electromagnetic states with their unique characteristics at nanoscale, offering an alternative to sophisticated plasmonic devices to alter light-matter interaction.

In this study, we design a vertical split-ring resonator for an active plasmonic polarizer. By using E-beam lithography, we can define the arm length and arm width of the VSRR. Then we deposited Ni and Au bilayer and do the lift-off process. Further, we utilized CF4-assisted inductively coupled plasma reactive ion etching (ICP-RIE) to isotropically etch the sacrificial layer below. The arms of the pattern were then simultaneously released and self-folded because of the residual stress in the metal film. Due to the vertical anisotropic structure, we can achieve different phase accumulation along the x and y-axis. When we illuminate linear polarized light at a certain polarization angle, we can achieve a reflective circular polarized light. By applying current on the device, the joule heat would lead the vertical structure to bend toward the substrate. The resonance changes as the curvature of the arm, then we will again get a linear polarized light. By the simulation, now we can get a full change in the reflection light from circularly polarized light to linear polarized light at 55 THz. This VSRR polarizer can also be applied in the transmittance mode. The transmittance can also get a full change from circular to linear polarized light at 37 THz. Overall, this method of fabricating VSRR can easily tune the structure to fit into different resonance frequencies, and the design can achieve a high-efficiency polarizer both in reflection and transmittance modes.

We present a novel depth sensing system applying metasurface holograms and photonic crystal surface-emitting lasers (PCSELs). Our lens-free, single-shot system projects 9,500 infrared dots in a 0^th order of holographic image from a compact ~300² μm² sample area, offering a wide 56.7° field-of-view (FOV) with low power consumption. Our metasurface area is 55 times smaller than that of diffractive optical elements (DOEs) in commercial dot projectors. And our PCSEL has up to 10 times less power consumption than that of vertical-cavity surface-emitting laser (VCSEL) array in commercial dot projectors. The GaAs-based metasurface hologram and simple optical architecture make it lighter and more energy-efficient, suitable for wearable devices. This technology overcomes limitations of bulky dot projectors, paving the way for integration into compact wearable devices.

In this study, we demonstrated rapid microfluidic mixing using the photothermal properties of gold nanoisland films. By focusing laser beams on a gold nanoisland film, bubbles were successfully generated in a 100-μm-thick fluid chamber filled with non-degassed water. Air-rich and water vapor-rich bubbles were generated by simultaneously irradiating two laser spots. Although water was not degassed, the water vapor-rich bubble was held next to the air-rich bubble for more than 10s, during which time a strong flow was generated. As a result, an area with a diameter of 1.5-2mm around the laser spot was stirred for approximately 3s. This method requires only a laser and thin film and does not require fluid degassing, making the method a promising active micromixer with a simple structure.

Surveillance of population immunity against infectious diseases is critical for pandemic management and risk assessment of future outbreaks. However, current serological tests fall short in accurately identifying immunity profiles from diverse populations. We present a label-free, rapid, multiplexed, and variant-sensitive nanoplasmonic biosensor to quantify antibodies against multiple SARS-CoV-2 antigens from small human blood samples. We combined a machine learning model with antigen-specific antibody patterns measured from four different cohorts with known COVID-19 immunity. Subsequently, we tested our model on 100 blind human samples and determine that our findings are consistent with public epidemiological data showing that our nanobiosensor can help monitor population health during a pandemic.

Two-dimensional (2D) materials such as Indium Selenide (InSe) is promising for next-generation optoelectronics due to its high carrier mobility and narrow direct band gap (1.26 eV). However, such devices suffer from low responsivity due to low absorption of atomically thin structure. Combining 2D materials with plasmonic nanostructure is an alternative solution for increasing light-matter interaction. Conventionally, researchers utilized metal for plasmonic nanostructure which unfortunately exhibit low quality resonances due to the inherent Ohmic losses. On the other hand, bulk transition metal dichalcogenides possess high refractive index (n > 4) from visible to near-infrared (NIR) region, which make them suitable for making sub-wavelength optical resonators. Herein, we report a MoS₂ plasmonic grating enhanced Indium Selenide (InSe) photodetector in near infrared (NIR) with inherent low loss compared to metallic grating. Such MoS₂ grating can not only form a n-n heterojunctions with InSe, but also act as a resonator to excite surface plasmon resonance (SPR) resulting in remarkably enhanced light absorption and photoresponsivity in InSe. In this work, by integrating InSe with anisotropic MoS₂ grating, we achieved a multi-band resonance in NIR region that are sensitive to either TE or TM polarized light due to different resonance mode. The responsivity of our device shows a 310-fold enhancement compared to pristine device at the resonance wavelength of 870 nm and the maximum detectivity reach 1.02 x 10¹⁴ Jones, which is the highest value reported for InSe device applied in NIR. This study provides a novel approach for designing high-performance InSe-based polarization-sensitive multi-band photodetectors.

Wastewater quality monitoring is essential as an effective pandemic management tool. Domestic water is one of the leading causes of wastewater pollution. Domestic water originates from urban centers and contains substances from human activity consisting of organic matter such as food remains, feces, oils, detergents, and soaps. Different ways of sensing are used to maintain the water quality, like pH, conductivity, and turbidity sensors. Alternative methods are optical sensors because these offer great potential for wastewater monitoring, allowing massive, easy and low-cost acquisitions of a wide range of measures in real-time, at any flow conditions, and with high spatial resolution. Plasmonic sensors are optical sensors used for detection, which could realize rapid recognition, real-time analysis, and sensitive and selecting sensing. These devices exploit the interaction of light with matter using the SPR as a method based on the optoelectronic phenomenon. When light hits a metal surface (typically a gold surface) at a certain angle, part of the light energy pairs through the metal coating with the electrons in the metal surface layer, which then move due to excitation, called surface plasmon resonance. We use the Kretschmann configuration and the matrix transfer method to analyze the performance numerically to achieve the optime parameters of design for the sensor’s performance. In this work, we design and build a plasmonic sensor for house wastewater monitoring by tracking contaminants along a continuous flow of artisanal water.

Materials characterization is essential since it is the basis for understanding materials’ physical and chemical properties before being used in any application. Nowadays, expensive equipment such as scanning electron microscopy and X-ray diffraction for thin film characterization at atomic layers are used. Atomic layer deposition (ALD) is a technique for growing thin films with a wide range of applications. The film thickness range is usually 1-500 nm. Plasmonic sensors are a low-cost technique for material characterization, including inorganic and organic thin films. The thickness resolution ranges from a fraction of a nanometer (monolayers) to several micrometers. These devices exploit the interaction of light with matter using surface plasmon resonance as a method based on the optoelectronic phenomenon. Kretschmann geometry continues to be a configuration widely used as an experimental setup to excite surface plasmon resonance in the characterization of different materials. It consists of a coupler prism with a thin metal film. The incident light in the total internal reflection at a specific angle, the evanescent wave transfers the energy to the electrons plasma of metal giving place surface plasmon resonance (SPR). The SPR effect in metals is highly sensitive to variations in the optical properties of the interface. We use the Kretschmann configuration and the matrix transfer method to analyze the performance numerically to achieve the optime parameters of design for the sensor’s performance. In this work, we developed a protocol to design and build a plasmonic sensor for the characterization of materials at the atomic layer level.

Hydrogen has garnered widespread attention as a pivotal indicator for future sustainable development. Current research aims to utilize clean energy for hydrogen production, thereby minimizing the generation of by-products such as hydrocarbons. Two-dimensional molybdenum disulfide (2D-MoS₂) has demonstrated outstanding photoelectrocatalytic (PEC) performance and shows promise as a material for photocatalytic (PC) hydrogen evolution (HER). However, its atomic-scale thickness limits light absorption. Therefore, the introduction of plasmonic metal nanoparticles to enhance light-matter interactions through the plasmonic resonance effect can substantially improve the overall catalytic efficiency. Conventional single-element noble metal nanoparticles exhibit relatively poor catalytic effects, while multi-element alloys have emerged as excellent catalysts due to their high entropy effect. In this study, we designed a heterostructure (SiNW/MoS₂/HEANP) by combining silicon nanowires, molybdenum disulfide, and a novel high-entropy alloy nanoparticle to demonstrate outstanding photocatalytic hydrogen evolution performance. The silicon nanowire structure, exploiting light-trapping effects, exhibited high anti-reflection properties, achieving over 97% absorption of visible light and providing abundant reaction sites. Moreover, the mixed-phase structure of 1T and 2H MoS₂, synthesized via thermal pyrolysis, contributed to the enhanced HER performance of the material. The HEA(AgAlCuNiTi) nanoparticles, synthesized through sputtering and annealing, exhibited a significant synergistic effect with MoS₂ through its decent plasmonic resonance and excellent HER activity, resulting in a substantially improved overall catalytic efficiency. The SiNW/MoS₂/HEANP heterostructure demonstrated a remarkable hydrogen generation rate of 475.5 mmol g-1 h-1. This study presents a strategy for utilizing HEAs as promising materials for photocatalytic hydrogen evolution with tremendous potential.

This paper reports on the giant circular dichroic second-harmonic generation (CD-SHG) behavior of double SP resonant chiral Al nanorod (AlNR) dimer structures. The two AlNRs are aligned in a straight line. It becomes chiral, when one of the AlNRs is shifted laterally from it. We obtained CD-SHG signals up to 0.5 for the corresponding amount of the shift. Additionally, the sign of the CD-SHG was reversed, when the sign of the shift was reversed. The amount of the CD-SHG was flexibly tunable by changing the amount of the shift, which was the uniqueness of the present chiral plasmonic nanostructure.

In this study, we investigate the phenomenon of nearly zero reflectance and associated phase singularity in a random array of gold nanoislands (Au NI) both theoretically and experimentally. The Au NI were produced via solid-state thermal dewetting of ultrathin gold films, which were magnetron sputtered onto a glass substrate. The morphology of the nanoislands was characterized using scanning electron microscopy and atomic force microscopy. To understand the plasmonic response of the random array of Au NI, we conducted reflectance measurements for both s and p polarized beams demonstrating the p. These measurements were performed using the attenuated total internal reflectance configuration. A partial state of topological darkness in a random array of Au NI was demonstrated by showing nearly zero reflection for the p polarization component. Additionally, we employed a common path spectral interferometer to measure the differential phase spectra. Our findings revealed that the differential phase spectra exhibited abrupt ±π phase jumps, indicating the presence of a phase singularity regime. Moreover, we demonstrated high bulk reflectance index sensitivity (RIS) within this regime. To validate our experimental results, we compared them with analytical reflectance and phase spectra obtained through the application of island film theory. The agreement between the experimental and theoretical predictions provided strong confirmation of our measurement technique.

Microscopy is an essential tool for biomedical research and clinical diagnosis. Nevertheless, conventional wide-field imaging system lacks optical sectioning ability, restricting applications in thick tissues. Recently, HiLo microscopy improved sectioning efficiency but still requires axial movement. Here, we propose the Moiré metalens to develop the varifocal metalens based fluorescence optical sectioning microscopy. It leveraging metasurfaces capabilities to control optical properties. Our system enables optical sectioning and 3D imaging capability. We demonstrate multiplane HiLo optically sectioned images of fluorescent microspheres and ex-vivo mouse brain tissues. This technique opens new possibilities for high-contrast microscopy in biomedical research and clinical diagnosis.

In this work, we have developed a refractive index change sensing system utilizing localized surface plasmon resonance (LSPR) transduction, combined with a position-sensitive photodetector (PSPD). As the transducers, we utilized gold nano-islands formed through thermal annealing of an Au film with a nominal thickness of 13 nm. The LSPR was excited by evanescent wave in an attenuated total reflectance configuration. Refractive index changes result in modifications across the angular spectrum of LSPR, giving rise to variations in the differential signal detected between the two quadrants of the photodetector. We determined the refractive index resolution of our sensing system at different wavelengths and performed a comparative analysis with traditional surface plasmon resonance (SPR) transducers and available literature data. While LSPR transducers demonstrate a lower refractive index resolution (RIR) compared to SPR, the approach presented in this work stands out when compared to other LSPR sensing methods. Notably, at a wavelength of 785 nm, it achieves a remarkable RIR of 1.4 × 10⁻⁶ RIU.

In this work, we investigate the plasmonic response of a random metasurface based on gold nano-islands (AuNI) in an attenuated total reflectance (ATR) configuration. AuNI structures were obtained by thermal annealing of an ultrathin gold film deposited on a glass substrate. The samples exhibited a wide range of sizes and particle densities, varying the nominal gold thickness. For p polarization, a well-defined localized surface plasmon resonance (LSPR) dip was observed in all samples, while for s polarization, only AuNI with the smallest radii showed this dip. Some samples exhibited nearly zero reflection at the resonance wavelength. The highest sensitivity among all tested samples was achieved in these samples, providing potential for optimizing LSPR transducers in sensing applications. Notably, the resonance wavelength exhibited a nonlinear dependence on the refractive index in sensitivity measurements displaying a blue shift.

This work introduces an interesting configuration for exciting structured surface plasmon-polaritons (SSPP) by analyzing wave propagation on a composite dielectric-metal surface. In particular, we focus on the coupling of interfered evanescent waves with structured SPP. This innovative approach unlocks new avenues for enhancing plasmon optics models, encompassing diffraction, interference, and focalization. By exploring the potential of this configuration, we improved the understanding and application of structured SPP in various optical phenomena.

We fabricated dielectric nanoantenna stickers comprising a periodic array of TiO₂ nanoparticles embedded inside the polydimethylsiloxane (PDMS). For the fabrication, we first used a nanoimprint to make a square lattice of TiO₂ nanoparticles on the SiO₂ glass substrate, and then covered it with a PDMS film. Finally, the nanoantenna was transferred from the substrate to the PDMS by dissolving the sacrifice layer between the nanoantenna and the substrate. We found that poly(sodium-4-styrene sulfonate) was suitable as the water-soluble sacrifice layer for the transfer of TiO₂ nanoantenna. As a demonstration, we placed the TiO₂ nanoantenna sticker on top of the light-emitting layer. The emission from the emitter layer was enhanced directionally following the dispersion of lattice resonances excited in the sticker.

We show that graphene decorated with Ag nanodisks realizes spectrally selective thermal emission by means of acoustic graphene plasmons (AGPs) localized between graphene and the Ag nanodisks inside a dielectric material. Our finite-difference time domain (FDTD) calculations show that the spectrally selective thermal radiation emission can be tuned by means of a gate voltage into two different wavelength regimes, namely the atmospherically opaque regime between λ = 5 μm and λ = 8 μm or the atmospherically transparent regime between λ = 8 μm and λ = 12 μm. This allows for electrical switching between a radiative heat trapping mode for the former regime and a radiative cooling mode for the latter regime.