This PDF file contains the front matter associated with SPIE Proceedings Volume 11194, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Absorption of light is critical to light-trapping devices such as photovoltaics, biosensors, photodetectors, etc. Naturally occurring materials have weak absorption, while perfect absorbers based on metamaterials are developed to solve the weak light absorption of light-harvesting devices. This presentation will provide an overview of metamaterial absorber enhanced light harvesting devices and our recent research progress on metamaterial absorbers.

Highly dispersed and uniform α-NaYF₄ micron flowers with about 500nm size was synthesized by a simple wet-chemical at a low temperature, then NaYF₄:Eu³⁺@Au hybrid structures with various amount Au nanoparticles (Au NPs) are prepared and single NaYF₄:Eu³⁺@Au hybrid particle is taken to investigate the influence of noble metal nanoparticle on the luminescence emission and present corresponding mechanism. It is found that luminescence emissions of NaYF₄:Eu³⁺ was quenched by introducing Au nanoparticles, and with increase of Au nanoparticles, the fluorescence quenching was more and more serous while emission intensity ratio of electric dipole to magnetic dipole transition of Eu³⁺ gradually become larger.

A gap mode plasmon induced photocatalytic oxidation of p-alkyl thiophenol (p-AlTP), encompassing methyl, iso-propyl and tert-butyl groups, to p-mercaptobenzoic acid (p-MBA), for which excitation 532 nm laser (<1 μW/μm²) impinged on a sample of silver (Ag) nanoparticles/p-AlTP/Ag films/BK-7 prism. Apparently, the oxidation of p-AlTP yielded p-MBA without leaving any signs of the intermediated species like p-mercaptobenzyl-aldehyde or -alcohol (p-MBAl) in the air. In contrast to p-AlTP, o-methyl TP and m-methyl TP were not oxidized, indicating preferential reactivity of the para position in TP molecules. Nonetheless, the site selectivity is not always valid in this type of photocatalytic reactions, as o-, m-, and p-MBAl molecules were oxidized to corresponding o-, m- and p-MBA. Similarly, all of o-, m-, and p-MBA molecules were decarboxylated to TP in the air. With respect to the reaction mechanism, we confirmed that the oxidation of p-MeTP is not induced by thermal heating of the samples up to 373 K. Subtle temperature increase (<10 K) during the gap mode-induced oxidation was also corroborated by the observed Stokes and anti-Stokes scattering intensity of p-MeTP. Oxygen molecules accelerated the oxidation of p-MeTP at room temperature, whereas nitrogen atmosphere generated an intermediate species attributable to p-mercaptobenzyl radical.

Graphene has been proposed as an advanced plasmonic material spanning from infrared to terahertz (THz) bandwidth due to its advantages, such as electrical tunability, high carrier mobility, and low energy loss, etc. Therefore, plasmonic devices based on graphene have great potential in active tuning of the plasmon resonances through electrical doping. However, a major drawback of the electrically tuning is that the metal electrodes used in this scheme may increase the complexity of device fabrication and decrease the effective area for wave-graphene interaction. Optically tuning is an alternative to resolve this problem. Here we present a theoretical study on the THz responses and plasmonic properties of graphene-based heterostructures (GBHSs) in the presence of visible irradiation. More concretely, by combining classical electromagnetic theory with the dynamic graphene conductivity under optical pumping, we establish analytical models to describe the THz basic/plasmonic responses of GBHSs including graphene/substrate, cavity with graphene, and graphene/dielectric/dimple-array systems. Meanwhile, the effects of the power of the modulation/pumping light on the plasmonic resonances are also illustrated. The results obtained here are expected to help us to explore the potential applications in new type of graphene-based plasmonic devices, such as all-optical modulators, sensors, and filters.

Rare-earth doped NaLaF₄ nanocrystals were synthesized by solvothermal method in ethanol/oleic acid/water reaction system. The structure and porphology of samples were characterized by X-ray diffraction(XRD), scanning electron microscopy (SEM) and transmission electron microscopy(TEM). By adjusting the amount of NaOH in the precursor, we obtained NaLaF₄:Er³⁺/Yb³⁺/Gd³⁺nanocrystals with a rich variety of morphologies, including nanoprisms, nano-dumbbells, nanorods and nanowires. A possible mechanism of formation of the NaLaF4 nanocrystals was proposed based on the time dependent experiments. The upconversion luminescence properties of rare-earth doped NaLaF₄ nanocrystals with different morphology was discussed. The experimental results demonstrated that the NaLaF₄:Er³⁺/Yb³⁺/Gd₃₊ nanocrystals with different morphologies exhibited similar up-conversion luminescence, with sharp emission peaks near 540 nm and 650 nm, and red color stronger than green light.

Trivalent rare-earth (RE)-doped upconversion photoluminescence (UCPL) materials are promising in solar cell, anti-fake printing, and displays. However, the intensity of UCPL is often not high enough for practical applications, because of very weak absorption cross-section at the pump wavelength due to the parity forbidden intra-4f shell transitions of RE ions. One promising approach for the enhancement of UCPL efficiency is exploiting the coupling of RE-doped upconverters with surface plasmon resonance of a metal nanostructure. In this paper, we report lithographically fabricated two-dimensional square lattice of Al nanocylinders combined with nanoparticles layer of CaF₂ codoped with Er^3+,Yb³⁺ that shows enhanced UCPL. We systematically vary the periodicity of the lattice and examine the UCPL enhancement. The maximum UCPL enhancement is observed at a period of 750 nm, showing 22 and 13.3-fold enhancements for green and red emission branches, respectively. Moreover, we observe enhancement of downconversion emission at 1540 nm. A comparison between the experiment and simulation suggests that enlarged light absorption at the pump wavelength is a dominant factor for UCPL and downconversion enhancements.

This paper perform the results of studies on the development of a simple methodology for creating hydrosol-modified silver and gold nanoparticles with a size of 44 nm (silver) and 54 nm (gold) quartz surfaces for sensory purposes. Proposed surfaces is able to perform the effect of Surface-enhanced Raman scattering (SERS) of light by dye molecules of Rhodamine 6G. It was shown that the order of amplification of the Raman signal by surface plasmons of silver and gold nanoparticles for Rhodamine 6G dye molecules can reach orders of magnitude 10² times. A method for the controlled synthesis of silver hydrosols by methods of reducing sodium salt AgNO₃ with sodium citrate and femtosecond laser ablation for gold is proposed. The prospects of such systems for obtaining spectra of the molecular structure of dyes are shown. The results of this work, in the future, can be used to analyze chemical compounds of low concentrations, macroscopic biological objects like bacterial cells and blood components.

The precise understanding of the spatiotemporal characteristics of ultrafast surface plasmons is a prerequisite for applications of plasmonics. Here, we report on the investigation of near-field imaging and dynamics of propagating and localized surface plasmons (PSPs and LSPs) using photoemission electron microscopy (PEEM) of the trench on the silver film and gold bowtie nanostructure. The actual propagation direction of PSPs is directly obtained by reading PEEM images via the non-collinear exciting method by the trench. The results have demonstrated that the trench structure is potential as a 2D plasmonic dispersion element. Moreover, we experimentally obtain different LSPs dephasing times in the tips of the bowtie nanostructure by interferometric time-resolved PEEM. Experimental result reveals the dynamics of the LSP field initially oscillate at the laser field frequency and finally develop into its eigenfrequency after experiencing a few periods of frequency fluctuation.

Arising from condensed-matter excitations, epsilon-near-zero (ENZ) modes are a new path for enhancing light-matter interactions at nanoscale with their unique and interesting optical properties when probed at wavelengths corresponding to their zero permittivity crossing points. In this work, a highly efficient tunable absorber can be achieved by integrating an ultra-thin indium tin oxide (ITO) film into the periodically patterned metal-insulator-metal (MIM) structure. Particularly strong absorption modulation could be achieved when the ITO is operated in the ENZ spectral range. This work can make a significant contribution to direct application in a range of optoelectronic devices that require active control over light absorption and energy conversion.

Machine learning has been received considerable attention in various research fields, because the processing power of general-purpose computers has improved. The design of optical materials using neural network (NN) may revolutionize the methodology of nanophotonics research. In this paper, we introduce NN methods to solve the problems of scattering cross-section of multi-layered cylinder (forward calculation). The NN calculation is 3500 times faster than that based on the Mie theory.