Current Researche Area

 

Atmosphereic Pressure Plasma and Its Applications :

 

Atmospheric Pressure Plasma Jet (APPJ). 

Large Gap Discharge Phenomena and Its Applications :

 

The positive column discharge characteristics in the long gap (440m) are investigated based on the voltage distribution among three electrodes. In particular, the effects of the amplitude and width of the short pulse applied to the address electrode on the positive column discharge characteristics are examined intensively. By proper controlling of the amplitude and width of the address short pulse, it is found that the positive column discharge in the long gap is well constructed. As a result, under the stable static voltage margin condition, the firing and sustaining voltages are as low as those of conventional short gap (60m) discharge and the color purity is improved. Moreover, the luminous efficiency increases up to 60% in comparison with the conventional case. 


Image Sticking Phenomena and Reducing techniques :

 

 The image sticking needs to be solved urgently for the realization of a high image quality in AC-PDP. However, the image sticking phenomenon has not been exactly understood so far. In conventional ramp-reset discharge, as the voltage slope during a ramp-up period becomes slower, the luminance difference between the image sticking and no image sticking cells is decreased. Accordingly, the ramp-reset waveform with a slow voltage slope is preferable for reducing the dark image sticking. The facing reset discharge waveform is newly designed and proposed to reduce a dark image sticking in AC-PDP. 


Fast Addressing Driving Schemes :

 

A new bipolar scan waveform is proposed to increase the light emission duty factor by chieving the fast address in AC-PDP. The new bipolar scan waveform consists of two-step scan pulse, which can separate the address discharge mode into two different discharge modes: a space charge generation mode and a wall charge accumulation mode, By adopting the new bipolar scan waveform, the light emission duty factor is increased considerably under the single can ADS driving scheme due to the reduction of address time per single subfield.


Novel PDP Structure and Its Driving Scheme :

 

The discharge characteristics of the new cross-shaped cell structure are compared with those of the conventional stripe-type cell structure under monochrome green phosphor 6-inch test panel with various pressure and Xe contents at a driving frequency of 30 kHz. The new cross-shaped cell structure shows a higher luminous efficiency (2.2lm/W at 180V, Xe10%, and 600Torr) than the conventional stripe-type cell structure (1.5lm/W at 150V, Xe4%, and 400Torr). In addition, the luminous efficiency were measured in various condition, such as Xe partial pressure (Xe 4%, Xe 7%, Xe 10%), total gas pressure (300 Torr, 400 Torr, 500 Torr, 600 Torr). This increase in the luminous efficiency of the new crossed-shaped cell structure is due to the increase in the effective phosphor area.


Physics of Left-Handed Metamaterial Guiding and Radiating Structures :

 

Metamaterials are artificial structures that can be designed to exhibit specific electromagnetic properties not commonly found in nature. Recently, metamaterials with simultaneously negative permittivity and permeability, more commonly referred to as left-handed materials, have received substantial attention in the scientific and engineering communities. Our research group has focused on fundamental physics and their applications of the planar and nonplanar left-handed metamaterial guiding and radiating structures such as superslow waves, superluminal and negative group velocities, plasmonic nano-electomegnetic / nano-optical circuits, and subwavelength resonators, as well as photonic crystals and artificial magnetic conductors.