Terahertz time-domain spectroscopy (THz-TDS) is one of the main research platforms for terahertz (THz) science and technology. However, a traditional system is not only bulky but also has some limitations in detecting micro and liquid samples because of the large THz beam spot dimensions and the strong THz-wave absorption by water. We have developed a THz-TDS measurement chip by directly fabricating THz transmission lines and photoconductive antenna electrodes on a low-temperature GaAs epitaxial wafer. This chip integrates THz-waves generation device, detection device, and the transmission line in the size of 1 mm × 20 μm and uses the between the THz evanescent field sample interaction near the transmission line to obtain the spectral information from the trace or liquid samples. Using a self-built measurement beam path, we tested the chip with 1550-nm femtosecond laser and obtained THz spectroscopy in the 0.1 to 0.7 THz range, thereby verifying the feasibility of the chip.
Terahertz on-chip system integrates the generation of terahertz, detection devices and transmission lines on the same substrate. It has the characteristics of small size, high measurement stability and easy operation. This paper is devoted to the study of the electrode of the photoconductive antenna necessary for the generation and detection of terahertz. HFSS software is used to simulate seven types of antennas with two types, large aperture and small aperture. The S11 images and VSWR images of each structure are obtained, and the emission efficiency of the optimal antenna electrode structure is obtained by comparison. For small aperture antenna, rectangular antenna has the highest transmitting efficiency; for large aperture antenna, dipole antenna and dish antenna have higher efficiency. But in the butterfly antenna, when the antenna spacing and the antenna length are both 50μm, the reflection power is the smallest and the performance is the best. These simulation results provide a parameter basis for the subsequent fabrication of chips.