LT-GaAs Thin film antenna based on the asynchronous optical sampling system

Abstract

Using a photoconductive antenna to generate terahertz (THz) waves is a common method, and the material of the antenna is usually low-temperature gallium arsenide (LT-GaAs). A LT-GaAs epitaxial wafer with four layers structure is prepared in this paper, and then the LT-GaAs thin film is obtained by etching the aluminium arsenide (AlAs) with dilute hydrochloric acid and transferring it to the silicon wafer to make a thin film photoconductive antenna. The performance of the antenna is evaluated using an asynchronous optical sampling (AOS) terahertz time-domain spectroscopy (THz-TDS) system with variable repetition frequency. The system uses the spectral coherence method of two lasers to obtain trigger signals and generates THz signals with high signal-to-noise ratio. This also confirms that the system has the advantages of high spectral resolution and fast detection speed. It has incomparable advantages over the traditional THz-TDS system in the environment requiring rapid measurement.