Yu-Ju Hung

Active tuning on a plasmonic structure is discussed in this report. We examined the transient transmission effects of an azo-dye-doped liquid crystal cell on a metallic surface grating. The transition between isotropic and nematic phases in liquid crystal generated micro-domains was shown to induce the dynamic scattering of light from a He-Ne laser, thereby allowing transmission through a non-transparent aluminum film overlaying a dielectric grating. Various grating pitches were tested in terms of transmission effects. The patterned gratings include stripe ones and circular forms. Our results indicate that surface plasmon polariton waves are involved in the transmission process. We also demonstrated how momentum diagrams of gratings and Surface Plasmon Polariton (SPP) modes combined with Mie scattering effects could explain the broadband coupling phenomenon. This noteworthy transition process could be applied to the development of spatially broadband surface plasmon polariton coupli...

This paper describes the derivation of surface plasmon polariton modes associated with the generalized three-dimensional rotation of liquid crystal molecules on a metal film. The calculated dispersion relation was verified by coupling laser light into surface plasmon polariton waves in a one-dimensional grating device. The grating-assisted plasmon coupling condition was consistent with the formulated k(spp) value. This provides a general rule for the design of liquid-crystal tunable plasmonic devices.

Surgery for advanced hepatocellular carcinoma with inferior vena cava or right atrium extension represents challenging procedures for hepatobiliary surgeons. Regardless of the surgical approach chosen, the liver parenchyma inevitably has to suffer from ischemia during the total hepatic vascular exclusion period. We report our novel technique for resection of a huge hepatocellular carcinoma extending to the right atrium. During the total hepatic vascular exclusion period, in-situ cold perfusion of the liver was performed in order to minimize the ischemic insults. The 53-year-old male patient with chronic hepatitis B was diagnosed to have a huge right lobe hepatocellular carcinoma, besides which the tumor had invaded the right hepatic vein and right atrium. With the help of cardio-pulmonary bypass and in-situ cold perfusion of the liver, the tumor was removed en-bloc. The operating time was 458 minutes. The cold ischemia time of the liver was 53 minutes 30 seconds. The cardio-pulmonar...

ABSTRACT Fourier expansions are used to express the fields radiated from a thin gold film with periodic nanoholes. The polariton fields inside the nanoholes are analyzed. The optical transmission is calculated by imposing field boundary conditions.

Renal interstitial fibrosis is characterized by increased extracellular matrix (ECM) synthesis. Epithelial-mesenchymal transition (EMT) in kidneys is driven by regulated expression of fibrogenic cytokines such as transforming growth factor-beta (TGF-β). Yam, or Dioscorea alata (DA) is an important herb in Chinese medicine widely used for the treatment of clinical diabetes mellitus. However, the fibrosis regulatory effect of DA is unclear. Thus, we examined TGF-β signaling mechanisms against EMT in rat fibroblast cells (NRK-49F). The characterization of DA water-extracts used various methods; after inducing cellular fibrosis in NRK-49F cells by treatment with β-hydroxybutyrate (β-HB) (10 mM), we used Western blotting to examine the protein expression in the TGF-β-related signal protein type I and type II TGF-β receptors, Smads2 and Smad3 (Smad2/3), pSmad2 and Smad3 (pSmad2/3), Smads4, Smads7, and EMT markers. These markers included E-cadherin, alpha-smooth muscle actin (α-SMA), and matrix metalloproteinase-2 (MMP-2). Bioactive TGF-β and fibronectin levels in the culture media were determined using ELISA. Expressions of fibronectin and Snail transcription factor, an EMT-regulatory transcription factor, were assessed by immunofluorescence staining. DA extract dose-dependently (50-200 µg/mL) suppressed β-HB-induced expression of fibronectin in NRK-49F cells concomitantly with the inhibition of Smad2/3, pSmad2/3, and Smad4. By contrast, Smad7 expression was significantly increased. DA extract caused a decrease in α-SMA (α-smooth muscle actin) and MMP-2 levels, and an increase in E-cadherin expression. We propose that DA extract might act as a novel fibrosis antagonist, which acts partly by down regulating the TGF-β/smad signaling pathway and modulating EMT expression.

ABSTRACT Minkowski domain walls are being actively considered in gravitation theory. They may form during a vacuum phase transition, or as a result of braneworld collision. Despite having interesting physical properties, Minkowski domain walls had remained in the theoretical domain only since their first introduction a few decades ago. Here we demonstrate how to make an electromagnetic analogue of a Minkowski domain wall using hyperbolic metamaterials. We analyze electromagnetic field behavior at the wall, and present a simple experimental model of “Minkowski domain wall” formation due to “collision” of two Minkowski spaces.

... Citation Mohammed Nadhim Abbas, Shih-Hsin Hsu, Yia-Chung Chang, and Yu-Ju Hung, "Using off-specular ellipsometry spectra of dielectric grating-coupled plasmon mode for biosensing," J. Opt. Soc. Am. ... Phys. Lett. 75, 3917–3919 (1999). [CrossRef]; IR Hooper and JR ...

Summary form only given. Compared with unidirectional transmission, bidirectional transmission reduces the required number of fibers. The efficiency of bandwidth usage can be further doubly by using the identical wavelength (i.e. wavelength reuse) from both directions. Because the identical wavelengths are reused in the reverse direction, the signals generate from the counter-propagating signals is difficult to be eliminated by filtering. This noise degrades the signal-to-noise ratio (SNR) and system performance. We present the experimental setup to measure the BER performance of a bidirectional wavelength-reuse system. One distributed feedback (DFB) laser was externally modulated by 10 Gbit/s signal.

... Shien-Kuei Liaw Corresponding Author Contact Information , E-mail The Corresponding Author , a , Horn-Yi Tseng b , Sien Chi b , Yu-Ju Hung b and Kuang-Yu Hsu c. ... c ChynOptics Communication Inc., Science-Based Industrial Park, Hsin-Chu 300, Taiwan, ROC. ...

Fabrication of three-dimensional photonic metamaterials faces numerous technological challenges. On the other hand, many new concepts and ideas in the optics of metamaterials may be tested much easier in two spatial dimensions using planar optics of surface plasmon polaritons. In this talk we will describe applications of plasmonic negative index metamaterials in various novel microscopy, waveguiding and switching devices.

We have observed enhanced transmission of light through a gold film due to excitation of standing surface plasmon Bloch waves in a surface Fabry-Perot resonator. Our experimental results strongly contradict the recently suggested model of light transmission via excitation of a composite diffractive evanescent wave.

We discuss various designs of two-dimensional dielectric optical elements, which enable efficient coupling of external light to surface plasmon polaritons, and allow us to guide and redistribute surface plasmon energy in the plane of propagation. Examples of these 2D dielectric optical elements include lenses, mirrors, waveguides, 2D plasmonic crystals, etc. The effective refractive index of the plasmonic crystals may be either positive or negative. These simple elements enable us to create compound 2D optical devices, such as microscopes and waveguide couplers. These devices exhibit diffraction-limited resolution, which is considerably better than the resolution of usual three-dimensional light optics.

Negative refraction of surface plasmon polaritons at the dielectric edge has been studied using near-field and far-field optical microscopy techniques. Edge plasmon polariton state has been observed. Magnified negative index imaging has been demonstrated using a far-field optical microscope. Good agreement between theoretically calculated and experimentally measured images has been demonstrated.

We have observed experimentally the anomalously large light transmission through a continuous gold film with various PMMA surface dielectric gratings deposited on top of the film. The spectra of these samples have been measured for different incident and scattered angles. Enhanced transmission through the film is attributed to the excitation of various surface plasmon modes. Both symmetrical and anti-symmetrical surface plasmon dispersion relations have been applied to analyze the transmission spectrum. Similar anomalous transmission effects have been observed in light transmission through gold-chalcogenide glass (As2S3) interfaces after grating formation in the chalcogenide glass using two-beam interference with strong pump light. Enhanced transmission is demonstrated using a weak probe beam. These observations demonstrate the possibility of all-optical signal processing using enhanced anomalous light transmission through metal films.

We demonstrate that surface plasmon polaritons can be guided by nanometer scale dielectric waveguides. In a test experiment plasmons were coupled to a curved 3 micrometer radius dielectric stripe, which was 200 nm wide and 138 nm thick using a parabolic surface coupler. This experiment demonstrates that using surface plasmon polaritons the scale of optoelectronic devices based on dielectric waveguides can be shrunk by at least an order of magnitude.

Various properties of Surface Plasmon Polaritons (SPPs) at the interface between a layer of PMMA (polymethyl methacrylate) gratings and a 50 nm thick gold film have been studied. Gold has a negative dielectric constant at visible wavelength range which results in negative refraction phenomenon without medium of both permittivity (epsilon) and permeability (mu) constants negative. A direct observation of negative refraction has been demonstrated. It verifies our assumption that in the 1-D stripe PMMA gratings on top of a gold film, SPPs experience negative group velocity and positive phase velocity. With this criterion, negative refraction is the natural choice in Snell's Law. Correspondingly, it was previously claimed that with a highly anisotropic layered structure (metal/dielectric stack), the high spatial frequency k vectors scattered from an object can be preserved in an imaging system and the conventional diffraction limit is defeated. In this dissertation, this kind of layered structure, a so-called "hyperlens" or "superlens", has been experimentally demonstrated and the results verify theoretical predictions. A proof of concept on corner resonators has also been demonstrated. Four squares with PMMA/Au and Air/Au are arranged so that SPPs are trapped in the corner. It shows the possibility of making a tiny resonator with zero phase paths in the cavity. An experiment utilizing the field enhancement of SPPs is designed. A surface field is excited on R6G(Rhodamine 6G, fluorophore)/PMMA gratings/Au substrate. The enhanced pumping light pushes up the emission intensity 10-fold or higher compared to a sample with a R6G/PMMA gratings/Glass platform, a transparent substrate. This device with a R6G/PMMA gratings/Au platform has the advantage that the emission light is converted to the normal direction; the collection efficiency is high and the directivity makes the examination easy under a commercial fluorescence optical microscope. This device shows the potential of R6G/PMMA/Au platforms in gene chip industry.

In this paper we introduce a new design for the magnifying superlens and demonstrate it in experiments. Our design has some common features with the recently proposed "optical hyperlens", "metamaterial crystal lens", and the plasmon-assisted microscopy technique. The internal structure of the magnifying superlens consists of concentric rings of polymethyl methacrylate (PMMA) deposited on a gold film surface.

Metamaterials have been already used to model various exotic "optical spaces". Here we demonstrate that mapping of monochromatic extraordinary light distribution in a hyperbolic metamaterial along some spatial direction may model the "flow of time". This idea is illustrated in experiments performed with plasmonic hyperbolic metamaterials. Appearance of the "statistical arrow of time" is examined in an experimental scenario which emulates a Big Bang-like event.

We report the experimental observation of photoinduced resonant transmission of light through a gold film deposited on a chalcogenide glass surface. This effect is caused by the formation of a photoinduced diffraction grating in the chalcogenide glass near the gold film surface by an optical pump beam. The transmittance of a probe beam is resonantly enhanced due to grating-induced coupling to surface electromagnetic excitations on the gold film surface. This observation demonstrates the feasibility of all-optical signal processing using the extraordinary light transmission of thin metal films.

Fluorescence from a layer of Rhodamine 6G (R6G) is observed to be enhanced strongly if a dielectric grating deposited onto a gold film is used as a substrate. The fluorescence enhancement has been studied as a function of the grating periodicity and the angle of incidence of the excitation light. The enhancement mechanism is consistent with excitation of surface-plasmon-polaritons on the metal film surface. The observed phenomenon may be promising in sensing applications.

ABSTRACT Imaging and focusing devices based on negative refractive index behavior of surface plasmon polaritons are described. These devices are based on two-dimensional plasmonic metamaterials consisting of alternating layers of positive and negative refractive indices, which are arranged in either layered or checkerboard fashion on the surface of a gold film.

Fabrication of three-dimensional negative refractive index materials in the visible range faces numerous technological challenges. On the other hand, many new concepts and device ideas in the optics of metamaterials may be demonstrated much easier in two spatial dimensions using surface plasmon polaritons. Here we demonstrate these concepts and devices using novel multilayer two-dimensional photonic materials consisting of alternating layers of positive and negative refractive index. By changing composition and geometry of the layers, the effective anisotropic refractive index of the material may be continuously varied locally from large negative to large positive values. This approach may find applications in many novel nanophotonic devices, which enable efficient control of light propagation on submicrometer scale. This becomes possible because of the considerably improved figure of merit of the plasmonic metamaterials compared to the typical figures of merit of their three-dimensional counterparts.

In our experimental geometry a layer of fluorescent material, either quantum dots or R6G has been spin-coated onto a PMMA grating. 40 nm thick PMMA nano-stripe gratings have been formed by E-beam lithography on top of two kinds of substrates: an ITO/Glass and an Au/Glass substrates. The thickness of the Au layer was about 50 nm. A typical periodicity of the PMMA stripe gratings was 500nm. The fluorescence coming from the PMMA gratings formed on top of the gold film was observed to be the brightest. Compared to the grating on the ITO substrate the fluorescence is enhanced by at least a factor of 10. In order to understand how the fluorescence signal is affected by the periodicity and angular rotation of the gratings, we made a sample with regions of different periodicity varying from 400nm to 1mum, and studied how fluorescence enhancement depends on the grating periodicity and sample rotation angle. It appears that the experimental conditions for maximum enhancement of fluorescence correspond to excitation of surface plasmon polaritons on the sample surface.

Fabrication of three-dimensional photonic metamaterials faces numerous technological challenges. On the other hand, many new concepts and ideas in the optics of metamaterials may be tested much easier in two spatial dimensions using planar optics of surface plasmon polaritons. In this talk we will describe applications of plasmonic negative index metamaterials in various novel microscopy, waveguiding and switching devices.

We have observed enhanced transmission of light through a gold film due to excitation of standing surface plasmon Bloch waves in a surface Fabry-Perot resonator. Our experimental results strongly contradict the recently suggested model of light transmission via excitation of a composite diffractive evanescent wave.

We discuss various designs of two-dimensional dielectric optical elements, which enable efficient coupling of external light to surface plasmon polaritons, and allow us to guide and redistribute surface plasmon energy in the plane of propagation. Examples of these 2D dielectric optical elements include lenses, mirrors, waveguides, 2D plasmonic crystals, etc. The effective refractive index of the plasmonic crystals may be either positive or negative. These simple elements enable us to create compound 2D optical devices, such as microscopes and waveguide couplers. These devices exhibit diffraction-limited resolution, which is considerably better than the resolution of usual three-dimensional light optics.

Negative refraction of surface plasmon polaritons at the dielectric edge has been studied using near-field and far-field optical microscopy techniques. Edge plasmon polariton state has been observed. Magnified negative index imaging has been demonstrated using a far-field optical microscope. Good agreement between theoretically calculated and experimentally measured images has been demonstrated.