A technique of enhancing terahertz (THz) wave radiation from large aperture photoconductive (PC)
antenna is presented in this paper. In this technique, the PC antenna is excited by both the optical and
previously-generated THz pulses by a laser induced air plasma created in front of PC antenna, an
enhanced THz wave signal is obtained. The technique shown in this paper can be very useful for THz
imaging and spectroscopy.
In this paper, the growth of ZnO/MgZnO composite structures with a larger number of periods by pulsed laser deposition
is presented. The structural and physical properties are quantitatively characterized by field-emission scanning electron
microscopy, transmission electronic microscopy, X-ray diffraction, and photoluminescence. It is demonstrated that the
quantum confinement effect has been observed from the composite structures at room temperature. The applications of
this unique ZnO/MgZnO composite structure are also discussed.
In this paper, recent works of buried chemical detection system by stimulating and enhancing spectroscopic
signatures with multi-frequency excitations are discussed. In this detection system, those multiple excitations,
including DC electric field, microwave, CO2 laser illumination and infrared radiation, are utilized and each of
them plays a unique role. The Microwave could effectively increase the buried chemicals' evaporation rate from
the source. The gradient DC electric field, generated by a Van De Graaff generator, not only serves as a vapor
accelerator for efficiently expediting the transportation process of the vapor release from the buried chemicals,
but also acts as a vapor concentrator for increasing the chemical concentrations in the detection area, which
enables the trace level chemical detection. Similarly, CO2 laser illumination, which behaves as another type
vapor accelerator, could also help to release the vapors adsorbed on the soil surface to the air rapidly. Finally, the
stimulated and enhanced vapors released into the air are detected by the infrared (IR) spectroscopic fingerprints.
Our theoretical and experimental results demonstrate that more than 20-fold increase of detection signal can be
achieved by using those proposed technology.
In this paper, some of our recent works on the design of different types of nanostructured surfaces, the
terahertz generation, terahertz lenses, and terahertz metamaterials are reviewed and discussed. The
mechanism behind the terahertz radiation is the photoelectric emission effect, which leads to the
oscillating motions of emitted electrons and are affected by the electric field inside the metal.
Furthermore, by using those nanostructured surfaces, terahertz lenses, which are due to the excitation
of surface plasmons, and terahertz metamaterials, which results from the effective inductor-capacitor
resonator, are also presented.