This PDF file contains the front matter associated with SPIE Proceedings Volume 12197, including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

The unique optical properties of plasmonic nanostructures render them a great many promising applications. However, the challenge is how to rapidly and cost-effectively fabricate plasmonic nanostructures whose typical feature size is at the level of tens of nanometers. This paper presents an additive print technology that can directly print micro-patterns of gold/silver nanostructures for plasmonic devices and sensor fabrication. This technology allows one-step fabrication of large-area plasmonic substrates with size-controlled gold/silver nanoparticles. Further development of the additive printing technology for the fabrication of plasmonic metasurface structures with high-requirement geometry is also discussed.

Richard Feynman’s method of path integrals is based on the fundamental assumption that a system starting at a point 𝐴𝐴 and arriving at a point 𝐵𝐵 takes all possible paths from 𝐴𝐴 to 𝐵𝐵, with each path contributing its own (complex) probability amplitude. The sum of the amplitudes over all these paths then yields the overall probability amplitude that the system starting at 𝐴𝐴 would end up at 𝐵𝐵. We apply Feynman’s method to several optical systems of practical interest and discuss the nuances of the method as well as instances where the predicted outcomes agree or disagree with those of classical optical theory. Examples include the properties of beam-splitters, passage of single photons through Mach-Zehnder and Sagnac interferometers, electric and magnetic dipole scattering, reciprocity, time-reversal symmetry, the optical theorem, the Ewald-Oseen extinction theorem, far field diffraction, and the two-photon interference phenomenon known as the Hong-Ou-Mandel effect.

In this study, we successfully self-assembled a micropattern of gold thin films and used their photothermal conversion properties to generate five water vapor microbubbles in close proximity. An isolated microsphere array with a number density of approximately 1.2 × 10^-3 μm^-2 was fabricated using electrostatic adsorption and surface tension reduction and was ten times denser than the arrays prepared by the spin-coating method. The prepared microsphere array was used as a mask for shadow-sphere lithography to fabricate the petal-like gold micropatterns. One gold micropetal was created in the shadow of each sphere, with each petal having the ability to generate one water vapor microbubble photothermally. The sample was then immersed in degassed water and irradiated with a laser for heating. As a result, up to five water vapor microbubbles were successfully generated in the laser spot with a radius of 35 μm. The number of bubbles changed with time owing to their interaction, and the direction of the surrounding flow changed accordingly. These results contribute to our understanding of the generation of strong flows and the flow oscillations caused by multiple bubbles.

As a result of their ability to amplify input light, ultra-high quality factor (Q) whispering gallery mode optical resonators fabricated from silica have demonstrated extremely low threshold nonlinear behaviors (eg FWM, Raman). However, while the cavity Q may reduce the threshold, it is not able to improve the efficiency. By coating optical resonators with gold nanorods functionalized with small molecule coatings or magnetic nanoparticles, we are able to increase the nonlinearity of the material system and demonstrate an efficient frequency comb generator in the near-IR. Additional nonlinear behaviors, e.g. Anti-Stokes/Stokes generation, are also observed with low thresholds.

The macroscopic permittivity tensors of a film-shaped metamaterial medium are calculated for the case when the charge carrier concentration N₀ of each constituent of the composite metamaterial varies across the film thickness. The influence of an applied gate voltage on the surface plasmon resonances and on the optical properties of such a system are studied. Both homogeneous and perforated metallic slabs are investigated. Our simulations are based on Fourier series expansion of the electric potential which reduces the problem to a truncated system of complex linear equations. It is shown that the macroscopic effective permittivity tensor, as well as other optical properties of the metamaterial, are extremely sensitive to the applied gate voltage. This can be used to construct fast switches and other optical devices.

Plasmonic structures offer a unique capability to generate electromagnetic oscillation in a tightly confined space at the metal-dielectric interface. This localized intense field can be used to significantly enhance light-matter interaction in an active material. Here, we use a hyperbolic metamaterial resonator on a UV AlGaN multiple quantum well to demonstrate a UV plasmonic nanolaser. The hyperbolic metamaterial consists of metal/dielectric multiple layer structure, which has dielectric permittivity tensor of opposite signs in two orthogonal directions. By proper design, it has an indefinite hyperbolic dispersion. We will discuss the resonator dimension design using this unique hyperbolic dispersion to enhance quantum well radiation for laser operation.

The semi-shell structures are attractive composite nanomaterials with properties such as optical anisotropy and large absorption cross sections. In this study, to evaluate the optical characteristics for the optical geometry of the semi-shell structure, we analyzed the scattered light spectrum using the propagation type surface plasmon. As a result of the measurement, the difference of the spectrum was observed depending on the optical geometry of the semi-shell structures. In addition, we confirmed their structures by FE-SEM observation of the measured structures, and evaluated the optical properties related to the optical geometry of the structure by performing FDTD simulation. From the experimental and numerical results, we evaluated statistical data on the orientation of the structure within a certain range. We could show the positive effect of the surface modified substrate to control the orientation of the semi-shell structures.

Gold nanoparticles (AuNPs) were the basis for the earliest research in the field of surface enhanced Raman scattering (SERS). Coupling of their surface plasmon resonances creates hot-spots of high electromagnetic intensities found to be very useful for sensing applications. However, chemically synthesized AuNPs in suspension are usually polydisperse and when arranged on a SERS substrate, lack periodic spatial organization. This leads to large variations in the enhancement factor (EF) which is detrimental to the sensing capabilities of the SERS substrate. Here, we showcase reproducible fabrication of an array of spherical AuNPs at the apices of shell isolated silicon nanocones with a homogeneous EF for SERS. The AuNPs are produced through discrete rotation glancing angle deposition of Au on shell isolated silicon nanocones (SI-SiNC) with square lattice periodicity and 250 nm pitch. By tuning the substrate tilt angle, substrate rotation angle and deposition thickness, the location and the size of the AuNPs formed can be controlled. Using this method, we successfully fabricated 60 nm AuNPs positioned at the apices of the nanocone array. Finite-Difference Time-Domain (FDTD) simulations were performed to visualize the electric field enhancement and verify conditions such as tip radius and oxide shell thickness to optimize the same. The EF was then experimentally calculated by performing SERS measurements on benzenethiol (BT) functionalized AuNPs at 400 unique points over the SI-SiNC substrate and compared to measurements of pure BT solution. A homogeneous substrate EF of (2.05 ± 0.05) ∙10⁷ (99% confidence interval) at par with literature was calculated for the C-S in-plane deformation mode, δ_CS, of the BT molecule excited at 1077 cm^-1. Our work highlights the advantages of nanofabrication for homogeneous SERS EF substrates.

We investigate the method to analyze interferometric plasmonic microscopy (IPM) images using a deep learning approach. An IPM image was generated by employing an optical model: the image intensity was formed by reflected and scattered fields. Convolutional neural network was utilized for the classification of IPM images. Conventional detection method based on fourier filtering was taken for comparison with the proposed method. It was confirmed that deep learning improves the performance significantly, in particular, robustness to noise. These results suggested applicability of deep learning beyond IPM images with higher efficiency.