Myung-Ki Kim

Characteristics and field emission of conducting poly (3,4-ethylenedioxythiophene) nanowires

Conducting poly (3,4-ethylenedioxythiophene) nanowires were synthesized by using an electrochemical polymerization method with a nanoporous template. Scanning and transmission electron microscopy confirmed the formation of conducting polymer nanowires (CPNWs) with an open end. The formation and the electrical properties of the CPNWs formed were dependent on synthetic conditions, such as the doping level, the polymerization time, and the applied current. The measured electrical conductivity of a single strand of CPNW was ∼3.4×10−3 S/cm at room temperature. From the ultraviolet and visible absorbance spectra, we observed a π–π* transition at ∼2.1 eV for the de-doped systems. A field emission cell of CPNW nanotips was fabricated. The turn-on field of the CPNWs was 3.5∼4 V/μm at 10 μA/cm2, and the current density increased up to 100 μA/cm2 at ∼4.5 V/μm. The field enhancement factor of CPNW nanotips was ∼1200, which is comparable to those of carbon nanotubes.

One-dimensional parabolic-beam photonic crystal laser

We report one-dimensional (1-D) parabolic-beam photonic crystal (PhC) lasers in which the width of the PhC slab waveguide is parabolically tapered. A few high-Q resonant modes are confirmed in the vicinity of the tapered region where Gaussian-shaped photonic well is formed. These resonant modes originate from the dielectric PhC guided mode and overlap with the gain medium efficiently. It is also shown that the far-field radiation profile is closely associated with the symmetry of the structural perturbation.

Plasmonic crystal defect nanolaser

Surface plasmons are widely interesting due to their ability to probe nanoscale dimensions. To create coherent plasmons, we demonstrate a nanolaser based on a plasmonic bandgap defect state inside a surface plasmonic crystal. A one-dimensional semiconductor-based plasmonic crystal is engineered to have stopbands in which surface plasmons are prohibited from travelling in the crystalline structure. We then confine surface plasmons using a three-hole defect in the periodic structure. Using conventional III-V semiconductors, we achieve lasing in mode volumes as small as V(eff) = 0.3(λ₀/n)³ at λ₀ = 1342 nm, which is 10 times smaller than similar modes in photonic crystals of the same size. This demonstration should pave the way for achieving engineered nanolasers with deep-subwavelength mode volumes and attractive nanophotonics integration capabilities while enabling the use of plasmonic crystals as an attractive platform for designing plasmons.

Conducting Polymer Nanotube and Nanowire Synthesized by Using Nanoporous Template: Synthesis, Characteristics, and Applications

We synthesized nanotubes and nanowires of conducting polypyrrole, poly(3,4-ethylenedioxythiophene), and polyaniline by using nanoporous template through electrochemical polymerization method. The DBSA, CSA, TBAPF 6 , or HClO 4 was used for dopant, and distilled water, acetonotrile, or NMP was used for solvent. From the SEM and TEM pictures, the formation of conducting polymer nanotube (CPNT) and nanowire (CPNW) was confirmed. The diameter and length of CPNT and CPNW were 200 nm and 10 40 μm. The length, nanotube, nanowire, and thickness of wall were determined from synthetic conditions such as polymerization time, current, and dopant. For structure, we investigated UV/Vis absorbance spectra and X-ray diffraction patterns. DC conductivity and I-V characteristic curve were measured for the systems prepared with various conditions of synthesis. For applications for CPNT and CPNW, we measured field emission characteristic curve for FED and capacitance.

Low-loss surface-plasmonic nanobeam cavities

One-dimensional surface-plasmonic nanobeam cavities are proposed as a means to confine surface plasmons to a subwavelength-scale mode volume, while maintaining a relatively high Q-factor. By bonding one-dimensional photonic-crystal nanobeam structures to a low-loss metallic substrate, a clear plasmonic TM bandgap can be formed. The introduction of a single-cell defect alongside the engineering of side-air-hole shifts to this plasmonic-crystal nanobeam provides subwavelength-scale plasmonic mode localization within the plasmonic TM bandgap. This suppresses radiation and scattering loss to render a maximum Q-factor of 413 and a modal volume of 3.67x10(-3) microm3 at room temperature. The possibility of further reduction in the intrinsic loss of the cavity is investigated by lowering the operating temperature and the Q-factor of 1.34x10(4) is predicted at a temperature of 20 K for the optimistic case.

A gain-scheduled L2 control to nuclear steam generator water level

Abstract This paper is concerned with the design of a gain-scheduled controller with guaranteed L 2 performance for the water level control of a nuclear steam generator which has parameter varying dynamics. The proposed controller guarantees both stability and a prescribed L 2 performance in the entire operating region. The systematical design method for the controller which is automatically adjusted along the reactor power, in terms of Linear Matrix Inequalities (LMIs), is shown. The main benefit of this method is to avoid most of difficulties such as gain-interpolation or griding technique in a classical gain scheduling control. The computer simulation demonstrates the effectiveness of the proposed controller in full operating range and its superiority to conventional PID controllers. ©

Fabrication of high-Q chalcogenide photonic crystal resonators by e-beam lithography

The authors thank the Endeavor Australian Cheungkong award for financial support and the support of the Australian Research Council through its Federation Fellow and Centers of Excellence Programs.

All-optical bistable switching in curved microfiber-coupled photonic crystal resonators

The authors report low-power optical bistability under continuous wave pumping conditions in five-cell photonic crystal linear resonators containing InGaAsP quantum wells, by employing the fiber-coupling technique. The threshold bistable power is measured to be 35μW at the normalized detuning of −1.724. Owing to the high band-edge nonlinearities of quantum wells and the efficient fiber coupling, minimal instability is observed. In addition, all-optical switching is demonstrated with switching energy less than 75.4fJ.

Squeezing Photons into a Point-Like Space.

Confining photons in the smallest possible volume has long been an objective of the nanophotonics community. In this Letter, we propose and demonstrate a three-dimensional (3D) gap-plasmon antenna that enables extreme photon squeezing in a 3D fashion with a modal volume of 1.3 × 10(-7) λ(3) (∼4 × 10 × 10 nm(3)) and an intensity enhancement of 400 000. A three-dimensionally tapered 4 nm air-gap is formed at the center of a complementary nanodiabolo structure by ion-milling 100 nm-thick gold film along all three dimensions using proximal milling techniques. From a 4 nm-gap antenna, a nonlinear second-harmonic signal more than 27 000-times stronger than that from a 100 nm-gap antenna is observed. In addition, scanning cathodoluminescence images confirm unambiguous photon confinement in a resolution-limited area 20 × 20 nm(2) on top of the nano gap.

Statistical PMD emulator using variable DGD elements

We report on a novel polarization-mode dispersion (PMD) emulator with exact Maxwellian statistics. The proposed PMD emulator was implemented by using variable differential group-delay elements and polarization controllers. Unlike the previous PMD emulators, the proposed PMD emulator could generate not only the first-order PMD with exact Maxwellian distribution, but also the second-order PMD.