Lee Hong-gi

The prevalent uses of JavaScript in web programming have revealed security vulnerability issues of JavaScript applications, which emphasizes the need for JavaScript analyzers to detect such issues. Recently, researchers have proposed several analyzers of JavaScript programs and some web service companies have developed various JavaScript engines. However, unfortunately, most of the tools are not documented well, thus it is very hard to understand and modify them. Or, such tools are often not ope

We investigate label-free measurement of molecular distribution by super-resolved Raman microscopy using surface plasmon (SP) localization. Localized SP was formed with plasmonic nanopost arrays (PNAs) for measurement of the molecular distribution in HeLa cells. Compared with conventional Raman microscopy on gold thin films, PNAs induce a localized near-field, which allows for the enhancement of the peak signal-to-noise ratio by as much as 4.5 dB in the Raman shifts. Super-resolved distributions

In this article, we report the use of randomly structured light illumination for chemical imaging of molecular distribution based on Raman microscopy with improved image resolution. Random structured basis images generated from temporal and spectral characteristics of the measured Raman signatures were superposed to perform structured illumination microscopy (SIM) with the blind-SIM algorithm. For experimental validation, Raman signatures corresponding to Rhodamine 6G (R6G) in the waveband of 73

We report sensing of single nanoparticles using disordered metallic nanoisland substrates supporting surface plasmon polaritons (SPPs). Speckle patterns arising from leakage radiation of elastically scattered SPPs provide a unique fingerprint of the scattering microstructure at the sensor surface. Experimental measurements of the speckle decorrelation are presented and shown to enable detection of sorption of individual gold nanoparticles and polystyrene beads. Our approach is verified through b

Near-field localization by ultrashort femtosecond light pulses has been investigated using simple geometrical nanoapertures. The apertures employ circular, rhombic, and triangular shapes to localize the distribution of surface plasmon. To understand the geometrical effect on the localization, aperture length and period of the nanoapertures were varied. Aperture length was shown to affect the performance more than aperture period due mainly to intra-aperture coupling of near-fields. Triangular ap

Precise measurement and control of local heating in plasmonic nanostructures are vital for diverse nanophotonic devices. Despite significant efforts, challenges in understanding temperature-induced plasmonic nonlinearity persist, particularly in light absorption and near-field enhancement due to the absence of suitable measurement techniques. This study presents an approach allowing simultaneous measurements of light absorption and near-field enhancement through angle-resolved near-field scannin

A super-resolution Raman scattering microscopy technique is demonstrated by combining localized surface plasmon-based structured illumination microscopy with the blindSIM algorithm. This approach enables super-resolution Raman scattering imaging of dielectric nanoparticles with sub-100 nm resolution. The technique leverages the surface-enhanced Raman scattering effect of rough silver films to generate near-field speckle patterns, enabling subdiffraction-limited optical sampling and enhanced Rama

This study introduces an innovative nanophotonic biosensor system designed to explore exosome dynamics within the gut-brain axis, highlighting the bidirectional and biochemical communication between the gastrointestinal tract and the central nervous system. The proposed system incorporates coculture environments for various cell types, microfluidic control of exosomes, and super-resolution imaging capabilities for both exosomes and live cells. While enabling real-time observation of long-range e

The detection sensitivity of surface plasmon resonance (SPR) biosensors has been improved by employing colocalization of spatial distribution of electromagnetic near-fields and detection molecules. We have used plasmon nanolithography to achieve light-matter colocalization on triangular nanoaperture arrays and optimized array configurations to improve colocalization efficiency. Streptavidin-biotin interactions were measured to validate the concept. It was confirmed that colocalized distributions

We present structured illumination microscopy based on random nanospeckle distributions of light fields localized by plasmonic nanoislands. Images were acquired of exosomes on biochips for super-resolved reconstruction. The results confirm improved image resolution below the diffraction limit.

This chapter presents near-field and far-field characteristics of nanoantenna networks and showed that signal propagation can be performed using diverse architectures. Nanoantennas refer to nanoscale transducers that convert electric energy into electromagnetic (EM) wave propagation as a transmitting antenna in a communication channel, with low energy loss, working at optical frequencies. EM radiation from nanoantenna induces near-field distribution on a wavelength spatial scale, which undergoes

We have investigated the excitation of fluoresce molecules using nanoscale light confinement on the plasmonic nanostructures. We have fabricated gold nano-dimer arrays whose diameter and height were 100 and 20 nm respectively on 20-nm gold film with BK7 substrate with a period of 746 nm. We have calculated the field distribution by three dimensional finite-difference time-domain (FDTD) method and confirmed the field localization on the dimer’s gap whose size was 18 nm. The field confinement was

We demonstrated gold nanodimer arrays could improve the signal-to-noise ratio (SNR) of fluorescence correlation spectroscopy (FCS). In this research, we explore the feasibility of plasmon-enhanced FCS for biomolecular study using a nanodimer array whose gap size was 18 nm. Fluorescence nanobead with a diameter of 40 nm was first examined to verify if gold nanodimer arrays can enhance SNR of fluorescence and scattering intensities. We emphasize that plasmon-enhanced FCS can improve the precision