Synthesis Methods and Optical Sensing Applications of Plasmonic Metal Nanoparticles Made from Rhodium, Platinum, Gold, or Silver.

The purpose of this paper is to provide an in-depth review of plasmonic metal nanoparticles made from rhodium, platinum, gold, or silver. We describe fundamental concepts, synthesis methods, and optical sensing applications of these nanoparticles. Plasmonic metal nanoparticles have received a lot of interest due to various applications, such as optical sensors, single-molecule detection, single-cell detection, pathogen detection, environmental contaminant monitoring, cancer diagnostics, biomedicine, and food and health safety monitoring.

Efficient electron-mediated electrochemical biosensor of gold wire for the rapid detection of C-reactive protein: A predictive strategy for heart failure.

C-reactive protein (CRP) is considered a promising biomarker for the rapid and high-throughput real-time monitoring of cardiovascular disease and inflammation in unprocessed clinical samples. Implementation of this monitoring would enable various transformative biomedical applications. We have fabricated a highly specific sensor chip to detect CRP with a detection limit of 2.

Nanogap Engineering for Enhanced Transmission of Wire Grid Polarizers in Mid-Wavelength Infrared Region.

Wire-grid polarizers (WGPs) have been widely used in various fields, such as polarimetry, imaging, display, spectroscopy, and optical isolation. However, conventional WGPs used in diverse mid-wavelength infrared (MWIR) applications show high reflection losses, which intrinsically arise from high refractive indices of their IR-transmitting substrates, such as silicon (Si) and germanium (Ge). This study demonstrated the enhanced transmittance of a transverse magnetic (TM) wave that surpassed ~80% over the entire MWIR range from 3000 to 5000 nm in a narrow air gap of a WGP, where aluminum (Al) was selectively deposited on a nanopatterned Si substrate using an oblique angle deposition method.

General Strategy for Broadband Coherent Perfect Absorption and Multi-wavelength All-optical Switching Based on Epsilon-Near-Zero Multilayer Films.

We propose a general, easy-to-implement scheme for broadband coherent perfect absorption (CPA) using epsilon-near-zero (ENZ) multilayer films. Specifically, we employ indium tin oxide (ITO) as a tunable ENZ material, and theoretically investigate CPA in the near-infrared region. We first derive general CPA conditions using the scattering matrix and the admittance matching methods.

Broadband Epsilon-Near-Zero Perfect Absorption in the Near-Infrared.

Perfect absorption (PA) of incident light is important for both fundamental light-matter interaction studies and practical device applications. PA studies so far have mainly used resonant nanostructures that require delicate structural patterning. Here, we realize tunable and broadband PA in the near-infrared region using relatively simple thin film coatings.

Binary mask designs with single- and double-layer absorber stacks for extreme ultraviolet lithography and actinic inspection.

In this study, we propose binary mask (BIM) designs with single- and double-layer absorber stacks with high optical contrast at a wavelength of 13.5 nm for use in extreme ultraviolet lithography (EUVL) and actinic defect inspection. The optimum thickness of the absorber stack was estimated using a method based on the transfer matrix.

Optical properties of Ag hemisphere-like nanoparticles.

We investigated the optical properties of Ag hemisphere-like nanoparticles. The nanoparticles were prepared by using magnetron sputtering and post-thermal annealing. The scanning-electron microscopy images reveal that hemisphere-like nanoparticles were successfully produced.

Optical performance of extreme ultraviolet lithography mask with an indium tin oxide absorber.

In this study, we propose a new extreme ultraviolet (EUV) binary mask with an indium tin oxide (ITO) absorber. The optical constant of ITO film at 13.5 nm wavelength in the EUV regime was determined by means of X-ray reflectivity measurements and the chemical composition was determined using Rutherford backscattering spectrometry.

Effects of seed layers on structural, morphological, and optical properties of ZnO nanorods.

We studied the effects of seed layers on the structural and optical properties of ZnO nanorods. ZnO and Ag-doped ZnO (ZnO:Ag) seed layers were deposited on glass substrates by magnetron co-sputtering. ZnO nanorods were grown on these seed layers by the chemical bath deposition in an aqueous solution of Zn(NO3)2 and hexamethyltetramine.

Linear polarization-discriminatory state inverter fabricated by oblique angle deposition.

In this paper, we report a linear polarization-discriminatory state inverter made of three-layer sculpture thin film fabricated by oblique angle deposition technique. The first and third layers are quarter-wave plates of zigzag structure and the middle of them is a circular Bragg reflector of left-handed helical structure. It is found that the normal incidence of P-polarized light on this polarization-discriminatory state inverter becomes the S-polarized light at output, while the incident S-polarized light of wavelength lying in the Bragg regime is reflected.

Wideband circular polarization reflector fabricated by glancing angle deposition.

We demonstrate a wideband circular polarization reflector fabricated as cascades of helical films with different pitch thickness by using glancing angle deposition (GLAD) technique. The full-width-at-half-maximum bandwidth of this reflector is measured from the reflectance spectra and is found about 200 nm indicating the feasibility of wideband reflector. A helical TiO(2) film with three sections, each of different pitch thickness, is also studied.

Optical design of hybrid-type attenuated phase-shift masks for extreme-ultraviolet lithography by use of a Fabry-Perot interference filter.

We have designed what we believe to be new hybrid-type attenuated phase-shift masks for extreme-ultraviolet optical lithography by use of a Fabry-Perot interference filter. The designs for the attenuated phase-shift masks show a smaller step height for less geometric shadow effects than additive- and subtractive-type attenuated phase-shift masks, a contrast higher than 94% for both deep-ultraviolet and extreme-ultraviolet wavelength regimes, and a 180 degrees phase-shift in the extreme-ultraviolet wavelength regime.

Optical monitoring of nonquarterwave layers of dielectric multilayer filters using optical admittance.

The optical monitoring method is described to compensate for the thickness error of nonquarterwave layers of dielectric multilayer filters, using optical admittance during deposition. Stability is confirmed by computer simulation of random thickness error generation in layers. In addition, a band split filter consisting of 61 nonquarterwave and nonperiodic layers is deposited in the proposed method, resulting in high spectral performance, as the design requires.

Effects of annealing on the optical, structural, and chemical properties of TiO2 and MgF2 thin films prepared by plasma ion-assisted deposition.

Effects of thermal annealing at 400 degrees C on the optical, structural, and chemical properties of TiO2 single-layer, MgF2 single-layer, and TiO2/MgF2 narrow-bandpass filters deposited by conventional electron-beam evaporation (CE) and plasma ion-assisted deposition (PIAD) were investigated. In the case of TiO2 films, the results show that the annealing of both CE and PIAD TiO2 films increases the refractive index slightly and the extinction coefficient and surface roughness greatly. Annealing decreases the thickness of CE TiO2 films drastically, whereas it does not vary that of PIAD TiO2 films.

Derivation of the center-wavelength shift of narrow-bandpass filters under temperature change.

We derive a simple equation to predict the center-wavelength shift of a Fabry-Perot type narrow-bandpass filter by using the conventional characteristic matrix method and the elastic strain model as the temperature varies. We determine the thermal expansion coefficient of substrate from the zero-shift condition of the center wavelength of the filter. The calculated shifts are in a good agreement with the experimental ones, in which the narrow-bandpass filters are prepared by plasma ion-assisted deposition on four substrates with different thermal expansion coefficients.

Control of resonant wavelength from organic light-emitting materials by use of a Fabry-Perot microcavity structure.

We report the fabrication of Fabry-Perot microcavity structures with the organic light-emitting material tris-(8-hydroxyquinoline) aluminum (Alq3) and derive their optical properties by measuring their photoluminescence (PL) and absorption. Silver and a TiO2-SiO2 multilayer were used as metal and dielectric reflectors, respectively, in a Fabry-Perot microcavity structure. Three types of microcavity were prepared: type A consisted of [air[Ag[Alq3]Ag]glass]; type B, of [air[dielectric[Alq3]dielectric]glass]; and type C, of [air[Ag[Alq2]dielectric]glass].

Design of omnidirectional high reflectors with quarter-wave dielectric stacks for optical telecommunication bands.

A design for omnidirectional high reflectors with quarter-wave dielectric stacks in the optical telecommunication band that uses conventional optical thin-film design theory is described. The omnidirectional bandwidth is derived in units of wavelength and investigated as a function of its high- and low-refractive-index values in the near infrared. The results show that the high refractive index should be larger than 2.

Deposition of a conductive near-infrared cutoff filter by radio-frequency magnetron sputtering.

We have designed a conductive near-infrared (NIR) cutoff filter for display application, i.e., a modified low-emissivity filter based on the three periods of the basic design of [TiO2[Ti]Ag] TiO2] upon a glass substrate and investigated the optical, structural, chemical, and electrical properties of the conductive NIR cutoff filter prepared by a radio frequency magnetron sputtering system.