Makoto Ohkado

Frequency-Tunable Microstrip Antenna With Liquid Actuator Using Gradually Widened Transmission Line

This letter reports on a mechanically reconfigurable frequency-tunable microstrip antenna that uses a liquid actuator as the dielectric layer to reduce the antenna size compared to the wavelength. By using direct polymer vacuum deposition on a liquid, the dielectric liquid can be encapsulated inside the polymer to form an actuator, which can change the liquid thickness. When the actuator is situated within the antenna, its resonant frequency can be changed by changing the liquid thickness. The liquid, which has higher permittivity than air, can decrease the antenna size. The resonant frequency of the fabricated antenna can be changed from 23.53 to 23.28 GHz via 37.6 μm of deformation.

Two-Directional CW THz Wave Generation System by Pumping With a Single Fiber Amplifier of Near-IR Lasers

We constructed a two-directional continuous-wave (CW) terahertz (THz) wave generation system with laser diode pumping. The generation method is based on difference frequency generation (DFG) of two near-infrared (NIR) lasers by excitation of phonon polaritons in a GaP crystal. The two NIR lasers for DFG are amplified simultaneously using one ytterbium-doped fiber amplifier (FA). Efficient beam overlapping of the NIR lasers was achieved on the GaP crystal surface. This system consists of a simple optical design with a single FA. Narrow linewidth CW THz waves, which are generated in two directions, can be applied to high-resolution spectroscopy.