This PDF file contains the front matter associated with SPIE Proceedings Volume 9925, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

We present experimental studies of live cancer cells via microscopic imaging ellipsometry (MIE). The Rotating Compensator Ellipsometry (RCE) is used for our measurements. Ellipsometry spectra with signals integrated over a 20μm×20μm area in visible range (450nm to 750nm) are obtained with the Optrel MULTISKOP system for both specular reflection and off-specular scattering. The microscopic ellipsometry (ME) images at a few fixed wavelengths within the same range were also analyzed. Dielectric constants for glass slide, culture fluid, and glass cover plate were firstly characterized by spectroscopic ellipsometry measurements, which can be used in the simulation for MIE measurements of cancer cells embedded in the culture fluid and sandwiched between a glass slide and cover plate. The measured ME spectra and images of cancer cells before and after medicine injection are measured and analyzed.

In this letter, we present the principle behind nanoscale photoacoustic tomography (nPAT), in addition to simulation results demonstrating the thermal safety and the diagnostic potential of such a modality. Nanoscale photoacoustic tomography is a novel biomedical imaging modality that can allow for the 3D imaging of cells at nanometer resolutions. This modality also allows for the imaging of single red blood cells (RBCs) such that the hemoglobin concentration quantities can be visualized within the cell. As a result, we believe that nPAT can allow for diagnostic information at unprecedented resolutions and enable the visualization of previously unseen phenomenon in RBCs.

Near-field scanning optical microscopy (NSOM) offers subwavelength optical resolution beyond the diffraction limit, enabling practical applications in optical imaging, sensing and nanolithography. However, due to the sub-100 nm size of apertures, conventional NSOM aperture probes suffer from the constrains of the strong attenuation of the throughput and limited the spatial resolution. To solve the problem, we designed a novel scheme for apertureless plasmonic probes with radial internal illumination. Employing non-periodic multi-rings geometry for plasmonic excitations, surface plasmons adiabatically nanofocuse energy at tip and the full width at half maximum of the optimal design is ∼18 nm. The proposed probe was optimized with 2D finite-difference time-domain (FDTD) analysis and realistic parabolic probe geometries. Comprehensive electromagnetic simulation shows that the optimal probe feature obeys Fabry-Pérot condition on the plasmonic metallic wall, giving rise to substantial field enhancement up to 6 orders of magnitude greater than conventional aperture probes without degrading its spatial resolution. We fabricated the proposed probe which possesses apex angle (∼ 22 degree) and tip radius (∼ 30 nm). Finally, the proposed near field plasmonic probe effectively combining the high resolution of apertureless probes with high throughput can enable the proposed plasmonic NSOM probe as a practical tool for applications in near field optical microscopy.

We report results of TERS characterization of graphene oxide and the 2D semiconductors, MoS2 and WS2. The gap mode TERS signal of these 2D materials becomes dramatically enhanced over wrinkles and creases, as well as over nanopatterns imprinted into flakes using a sharp diamond probe. The resonant Raman signal of MoS2 contains additional peaks normally forbidden by selection rules. TERS maps of few-layer-flakes of this 2D semiconductor show that the spatial distribution of Raman intensity across the flake varies for different peaks, providing interesting insights into the structure of such 2D semiconductors with 10-20 nm spatial resolution.

We investigate the optical response of individual porphyrin (TPPS₃) nanoaggregates anchored onto a glass substrate by using a specific configuration of Polarization-Modulation Scanning Near-Field Optical Microscopy (PM-SNOM). Subdiffraction spatial resolution and sensitivity to the chiroptical properties of the material is reported. By demodulating the transmitted signal at the first and the second harmonics, the response of the nanoggregates to circular and linear polarization is simultaneously acquired in the same scan. In order to evaluate the relevant dichroic coefficients, we analyze a sample comprising several tens of individual nanoaggregates by using a model based on the Mueller matrix formalism. Circular dichroism in the nanoaggregates is demonstrated to stem from their molecular structure, whereas linear dichroism occurs as a consequence of the strongly anisotropic shape of the deposited nanoaggregates.

Accurate measurement of Rayleigh scattering is crucially important for fundamental understanding of the plasmonic properties of meltimeric (≥ 3) nanoparticles that can be served as efficient SERS sensing platforms and nanophotonic materials. Thus, using the laser-scanning assisted dark-field microscopy that enabled to precisely collect far-field (Rayleigh) scattering from the centers of individual trimeric nanoparticles, we monitored spectral redistributions of oscillating coupled plasmonic modes as a function of trimer symmetry. As a consequence of the precise measurement of the polarization-resolved Rayleigh scattering spectra obtained from triangular trimers to linear trimers via elongated triangular trimers, the in-phase horizontally oscillating plasmonic mode with the largest dipole moment is found to be greatly increased by 20-folds, whereas the axially oscillating plasmonic mode with the second-largest dipole moment is dramatically decreased by 70-folds. Consequently, the overall quantity of the far-field scattering, the total sum of the individual coupled plasmonic modes, was gradually increased by 2-folds. The precise polarization-resolved Rayleigh scattering measurement also visualizes directly the directions of the radiation fields of individual oscillating coupled plasmonic modes, which would be valuable information in systematic controlling the polarization direction of the scattered light from the trimers. Overall, we showed an exemplary quantitative and extensive study of the coupled plasmonic modes from nanoparticles, giving a simple but clear insight.

The excitation of surface phonon-polariton (SPhP) modes in polar materials using scattering type near-field optical microscopy (s-SNOM) has recently become an area of interest because of its potential for application as naturally occurring meta-materials and in low-loss energy transfer. Within this area, hexagonal boron nitride (h-BN) and boron nitride nanotubes (BNNTs) are the primary structures under investigation. Here we present pump-probe continuous wave (CW) scattering-type scanning near-field optical microscopy (s-SNOM) - a novel two color pump-probe infrared technique which uses two continuous wave tunable light sources and is based on s-SNOM. The technique allows us to spatially resolve coupling of the longitudinal optical and surface phonon polariton modes in BNNTs. However, no similar coupling is observed in two-dimensional h-BN crystals.

Electron energy-loss spectroscopy (EELS) has become an experimental method of choice for the investigation of localized surface plasmon resonances, allowing the simultaneous mapping of the associated field distributions and their resonant energies with a nanoscale spatial resolution. The experimental observations have been well-supported by numerical models based on the computation of the Lorentz force acting on the impinging electrons by the scattered field. However, in this framework, the influence of the intrinsic properties of the plasmonic nanostructures studied with the electron energy-loss (EEL) measurements is somehow hidden in the global response. To overcome this limitation, we propose to go beyond this standard, and well-established, electron perspective and instead to interpret the EELS data using directly the intrinsic properties of the nanostructures, without regard to the force acting on the electron. The proposed method is particularly well-suited for the description of coupled plasmonic systems, because the role played by each individual nanoparticle in the observed EEL spectrum can be clearly disentangled, enabling a more subtle understanding of the underlying physical processes. As examples, we consider different plasmonic geometries in order to emphasize the benefits of this new conceptual approach for interpreting experimental EELS data. In particular, we use it to describe results from samples made by traditional thin film patterning and by arranging colloidal nanostructures.

This study presents the synthesis, SERS properties in three dimensions, and an application of 3D symmetric nanoporous silver microparticles. The particles are synthesized by purely chemical process: controlled precipitation of AgCl to acquire highly symmetric AgCl microparticle, followed by in-place to convert AgCl into nanoporous silver. The particles display highly predictable SERS enhancement pattern in three dimensions, which resembles particle shape and retains symmetry. The highly regular enhancement pattern allows an application in the study of inhomogeneity in two-layer polymer system, by improving spatial resolution in Z axis.

Despite often illustrated as a perfect two-dimensional sheet, real graphene sample is not always flat. Nanostructures can be occurred on graphene sheet, especially for epitaxial graphene. The nanostructures alter the electrical and mechanical properties of graphene. This is crucial for epitaxial graphene since its main potential is in the electronics and optics application. This study investigates nanostructures on epitaxial graphene by tip-enhanced Raman spectroscopy, which is a technique that can provide Raman spectra with great spatial resolution, exceeding the diffraction limit of light. The results suggest that the compressive strain on nanoridges is weaker compared to neighbor flat area, supporting the ‘ridge as compressive strain relaxation’ mechanism. TERS measurement of nanoridges on epitaxial graphene microisland also indicates that the ‘Si vapor trapping’ mechanism for ridge formation is unlikely to occur.