Receiving Properties of Thin-Film Slot Antenna Arrays for 28-THz-CO₂ Laser Radiation

抄録

The receiving properties of fabricated parasitic slot antenna arrays on ZnS dielectric substrates for 28-THz-CO₂ laser radiation were investigated. When the CO₂ laser beam was irradiated on the antennas directly (from the air-side), the E-plane antenna patterns of the parasitic slot antenna arrays became increasing sharper as the number of slots in the array increased from 1to 7. On the other hand, the H-plane antenna patterns did not change with the number of slots because the slot antennas were not arrayed in the H-plane. It was found that the antenna theory based on the transmission line model was applicable at 28 THz. When the CO₂ laser beam was irradiated through the substrate (from the substrate-side), rippled antenna patterns were observed due to multiple reflection in the substrate because the thickness of the substrate was much longer than the dielectric wavelength of the CO₂ laser. It was also found that the antenna receiving properties were affected by the thickness of the substrate. Furthermore, as expected from the theory, the power gain of the 7-parasitic slot antenna array improved by approximately 7 dB compared to that of the single-slot antenna at 28 THz.