In this study we report the first on the terahertz (THz) transmission characteristics of a guided-mode resonance (GMR) filter made of all-dielectric material. Two strong transverse electric (TE) resonance modes, TE0,1 and TE1,1, and one strong transverse magnetic (TM) resonance mode, TM0,1, were detected. The measured resonances can be explained by diffraction from the grating surface of the GMR filter, and by guiding along the inside of the filter (slab waveguide). Because two identical GMR filters were employed to overcome limited grating numbers, the measured Q-factors of the TM0,1, TE1,1, and TM0,1 modes were as high as 62.9, 71.0, and 74.4 respectively. Also, we obtained polarization efficiencies of up to 96.9, 96.3, and 92.9% for the TM0,1, TM1,1, and TM0,1 modes, respectively, when the GMR filter was rotated to 90°. By increasing the incident THz beam angle, one TE resonance can be divided into two TE resonances, and the resonant frequency can be adjusted like a THz tunable resonance filter. Furthermore, when the GMR filters were inserted between Teflon plates, only the TM1,1 mode was perfectly removed. The designed GMR filter has a high Q-factor, tunable filter, good polarizer, and good modulator characteristics. These experimental results were in good agreement with simulation results.

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We present experimental and simulation studies of enhanced terahertz (THz) guiding properties of curved two-wire lines for several surface conditions. When a THz-wave propagates through curved two-wire lines, a rough wire surface with dielectric coating contributes to a lower bending loss compared to a smooth or rough wire surface without coating. Dielectric coating and rough surface confine the THz field to the wire surface making the bending loss low. The guiding property at a curve depth of 30 mm of a rough wire surface with 25-μm-thick coating is improved by 34% compared to that of a smooth wire without coating. Furthermore, computer simulation technology (CST) software visually shows the bending loss as same as the experimental studies.

The effect of the plasma density structure on the electron energy in laser wakefield acceleration is studied. Using a simple rotatable supersonic nozzle, the plasma density structure is controlled. Two dimension particle in cell simulation indicates that due to the decrease of the size of the acceleration field cavity with increasing density structure, the electron energy is enhanced. Using 20 TW laser system, the laser wakefield acceleration with density increment structure was conducted. The results show the enhancement of the electron energy with the density increment structure.