In order to satisfy needs which are efficient detection and miniaturization of terahertz scanning imaging instrument, a rectangular wave-guide antenna with lengthwise slits on the broad face is designed. The antenna has the advantages which are high aperture efficiency, compact structure, small volume, light weight, low cost, low side-lobe performance, narrow beam scanning and so on. At first, these parameters include slit length, slit distance, slit width and slit offset along the central axial of the broad face are calculated with the aid of related theory, then the antenna is modeled and optimized in the software. The simulation results show that the antenna can directly transmit and receive the terahertz wave at 0.1THz, the gain of the main lobe is higher, the gain of the side lobe is lower and main lobe presents the pencil beam. The results can provide reference for the revised design of terahertz scanning imaging instrument.
Terahertz (THz) radiation, generated by ultra short laser pulses, occupies a broad band on electromagnetic spectrum chart. This radiation band belongs to far-infrared. It is a new research field of studying THz radiation interacting with materials especially with biomaterials. The paper shows experimental results of five plant oil samples from different kind of plants and two kinds of animal fat samples by using THz-TDS (THz time-domain spectroscopy) technology. The refraction indices and the absorption coefficients of these samples are measured in the range from 0.2 to 2.0 THz. The results show that different oils have different refraction indices. For oil samples, refraction indices decrease slowly while their coefficients of absorption increase with the increases of THz frequency. For the animal fat samples, the refraction indices show almost no change while the absorption coefficients increase with the increasing THz frequency. The absorption coefficients increase with the increasing temperature.