Kwang Geol Lee

Single gold nanoparticles can act as nanoantennas for enhancing the fluorescence of emitters in their near fields. Here we present experimental and theoretical studies of scanning antenna-based fluorescence microscopy as a function of the diameter of the gold nanoparticle. We examine the interplay between fluorescence enhancement and spatial resolution and discuss the requirements for deciphering single molecules in a dense sample. Resolutions better than 20 nm and fluorescence enhancement up to

Reducing the noise below the shot-noise limit in sensing devices is one of the key promises of quantum technologies. Here, we study quantum plasmonic sensing based on an attenuated total reflection configuration with single photons as input. Our sensor is the Kretschmann configuration with a gold film, and a blood protein in an aqueous solution with different concentrations serves as an analyte. The estimation of the refractive index is performed using heralded single photons. We also determine

We theoretically demonstrate spontaneous PT-symmetry breaking behavior of surface-plasmon polaritons (SPP) in coupled double-slab (DS) waveguides. By virtue of a flat-top field at critical wavelength, the imaginary index of a DS-SPP mode can be controlled via changing the core thickness, while the real index is kept constant. Therefore, a waveguide coupler that consists of a pair of DS-SPP waveguides with different core thicknesses can represent a passive PT-symmetric system, which always mainta

Single photons from single emitters are good candidates for a high-quality single-photon sourcewhich is essential in current quantum optical experiments and applications. Because the statisticsof emitted photons is mainly determined by the energy level structure of the system, knowing thecorrect level scheme and the transition rates between levels is of primary importance. In this work,the energy level scheme and the photon-emission statistics of a single terrylene molecule are studiedby measuri

We clarify the positive and the negative roles of a surface plasmon polariton in light transmission through metallic nanoslit/hole structures. While conventional surface plasmon polaritons suppress the transmission due to the equipartition of diffraction orders, we show. that "radiation dressed" surface plasmon polaritons (DSPP) mediate the extraordinary transmission. We determine the coupling strength of DSPP to radiation as a product of the geometric opening ratio, the apertu

We propose an optimal design for enhancing the external quantum efficiency of InGaN/GaN LEDs operating in the green spectral region, by mediating surface plasmons (SP), showing that there is plenty of potential for additional improvement in this area. Coupling the spontaneous emission from quantum wells into SP modes on metallic grating structures could enhance the internal quantum efficiency of conventional LEDs by more than twofold, and the relatively long propagating length of SPs in the gree

High modulation speed of light-emitting diodes (LEDs) is of primary importance for applications in optical communication. To this end, we experimentally investigated enhancement behaviors of the spontaneous emission rate (SER) of electronehole pairs in blue InGaN/GaN LEDs by mediating surface plasmons (SPs). The coupling strength of the electronehole recombination into SPs is controlled by etching the p-GaN layer between the active and metal layers to form thicknesses between 40 nm and 10 nm. Wh

Negative probability values have been widely employed as an indicator of the nonclassicality of quantum systems. Known as a quasiprobability distribution, they are regarded as a useful tool that provides significant insight into the underlying fundamentals of quantum theory when compared to the classical statistics. However, in this approach, an operational interpretation of these negative values with respect to the definition of probability---the relative frequency of occurred event---is missin

Coherence length (time) is a key parameter in many classical and quantum optical applications. Twointerferometers – Michelson and Young’s double-slit – are used to characterize the temporal coherenceof single photons emitted from single terrylene molecules. For quantitative analysis, a dispersion-relateddistortion in the interference pattern of a Michelson interferometer is carefully corrected by a simpledispersion compensation. Additionally, it has been demonstrated that Young’s interferometer

Photons emitted from a single emitter are promising candidates for an efficient single-photonsource, which is essential for many novel nano- and quantum-optical applications. As a photonsource having a larger flux and high reliability is highly desirable. In this paper, we quantitativelystudied the dependencies of the numbers of photons emitted and collected from single terrylenemolecules on different experimental conditions, the refractive index of the substrate and the numericalaperture of the

The negatively charged state of nitrogen vacancy centre (NV–) in diamond have been exploited in recent studies of magnetom etry and quantum information processing. Nevertheless, the useful signal of NV– for these applications can be deteriorated by the neutrally charged state (NV0) which acts as backgrounds. In recent studies, it has been reported that simultaneous excitation of green (532 nm) laser combined with infrared (1030, 1040, 1064 nm) laser can enhance the emission from NV– while suppre