[show abstract][hide abstract] ABSTRACT: Periodic structures in plasmas form unique dispersions of electromagnetic waves, which are examined in numerical calculation. Above electron plasma frequency, where waves equivalently propagate in dielectric media, plasma arrays with 2-D periodicity produce frequency regions of forbidden propagation, like band gaps in a photonic crystal. Below electron plasma frequency, where waves are usually forbidden to propagate due to cutoff phenomenon, bulk plasmas with periodic holes can become wave-propagating media in which localized surface modes play an important role. Such features give rise to concepts of dynamic wave controllers that change their inner electron density in time.
IEEE Transactions on Plasma Science 11/2007; · 0.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: Performances of microplasmas in unit discharge cells with grooved structures in the dielectric layer covering the coplanar electrodes were investigated in alternating current (ac)-type plasma display panels filled with Ne-Xe(10%) mixture at 450 torr. The diagnostics are based on a microscopic laser-absorption spectroscopy technique for the spatiotemporally resolved measurements of absolute densities of Xe<sup>*</sup>(1s<sub>5</sub>,1s<sub>4</sub>) atoms, from which the production rate and the efficiency of the vacuum ultraviolet photons were estimated. These results were compared with previously reported data obtained in conventional phosphor coated panels with the same structures for the dependences on the applied sustain voltages. As the result, the following conclusions were ascertained. The grooved structure does not help to improve the luminous efficiency but it helps to lower the firing and sustaining voltages by about 20 V if the electrode gap is kept constant. Therefore, it provides additional possibilities for the selection of other operating conditions such as the gas composition and pressure for the improvements of the luminance and the luminous efficiency.
IEEE Transactions on Plasma Science 05/2006; · 0.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: Millimeter plasmas were tailored to play a role as dynamic devices of microwave components, that is, to control electromagnetic wave propagation dynamically on a microstrip line. The generation of millimeter plasmas with their relatively long discharge channel (∼3 mm) was in high-pressure (20-200 torr) Ne, and they were successfully arranged near and on the conductor of microstrip lines. When such a plasma was set perpendicularly to the conductor to form a T junction, a significant reduction of electromagnetic wave transmission along the metal conductor was observed. The reduction rate depended on the discharge current and the number of T junctions. These experimental results are compared with the case of 2 MHz launching for crude electron density measurements and the numerical results of propagating electric fields in a two-dimensional model.
IEEE Transactions on Plasma Science 03/2006; · 0.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: A three-dimensional (3-D) observation cell with realistic AC-type structure and size was fabricated and measurements were done, for the first time, on the spatiotemporal behaviors of excited Xe atoms by using optical emission and laser absorption spectroscopic techniques. As a typical characteristic feature, it is seen that the discharge starts from the temporal anode edge, stretching toward the cathode, and a striated pattern of excited atoms appears on the anode side while a single broader peak distributes on the cathode side, traveling to its far end. In addition, the dependence on the applied voltage was clearly seen in the distribution of excited atoms, which shows the influence of the charge accumulation on the walls. With the two-dimensional projection images obtained from side and front views in both the emission and absorption measurements, an iterative method was tried preliminarily to derive the peak values of excited Xe atoms in the 3-D space.
IEEE Transactions on Plasma Science 03/2003; · 0.87 Impact Factor
[show abstract][hide abstract] ABSTRACT: It is a matter of importance to investigate the total number of excited Xe atoms and the production rate of Xe atoms of the surface-discharge plasma to improve the luminous efficiency of color AC PDPs. In order to understand the discharge mechanism in sustain periods, we have investigated phenomena caused by the addressing pulse to the microdischarge in an AC PDP unit cell.
[show abstract][hide abstract] ABSTRACT: We developed a microscopic laser-absorption method for the absolute measurement of excited Xe(1S<sub>4</sub>, 1s<sub>5</sub>) atoms, which lead to VUV emissions for the excitation of RGB phosphors, with a spatial and temporal resolution of 20 μm and 5 ns, respectively. For the measurement of higher lying excited Xe(2p) atoms and Ne(2p) atoms, the corresponding near IR and visible emissions were observed by a gated CCD camera equipped with appropriate optical band pass filters. For the simultaneous front and side view observations, we constructed a special panel, which had a realistic AC-type cell structure and sizes.
Plasma Science, 2002. ICOPS 2002. IEEE Conference Record - Abstracts. The 29th IEEE International Conference on; 02/2002
[show abstract][hide abstract] ABSTRACT: Two dimensional spatio-temporal behavior of excited Xe atoms in the 1s4 resonance state and the 1s5 metastable state have been measured in a unit cell of AC-type PDP by a laser absorption technique using an optical microscope. The measured density of Xe(1s_5) have two large peaks on both temporal anode and cathode sides. The peak at the anode has a narrower spatial distribution while the peak at cathode is distributed over the electrode area. In the temporal behavior, the anode peak rises slightly faster than the peak at the cathode and decays faster at the beginning of afterglow, but both the peaks tend to have the same decay rate in the later period. The behavior of Xe(1s_4) shows a similar feature, but the decay rate is much larger corresponding to the effective lifetime of imprisoned resonance radiation. The maximum densities of Xe(1s_5) and Xe(1s_4) are 5× 10^13 and 2× 10^13 cm-3, respectively. The emission from Xe(2p) atoms has also been observed, which nearly follows the current waveform.
[show abstract][hide abstract] ABSTRACT: For improving the luminous efficiency of plasma display panels (PDPs), characteristics of microdischarges depending on the cell structure and the operating conditions must be understood. We have developed special panels suitable for the front-view and side-view observations, and measured spatio-temporal behaviors of excited Xe atom densities in the 1s5 and 1s4 levels by a microscopic laser absorption technique. In the front observation, there appeared a sharp density peak on the temporal anode side and a broad peak on the temporal cathode side. From the side observation, it was seen that the distance of both peaks from the dielectric (MgO) electrode surface tended to increase as the gas pressure or the pulsed discharge period decreases. Similar measurements were also done on the optical emissions from several excited levels of Xe and Ne atoms by using a gated CCD camera. From these measurements, a three dimensional image of microdischarge phenomena in a PDP cell has been obtained on the characteristic behaviors of plasma parameters and the production rates of excited atoms leading to the VUV radiations.