Study Of Transmission Characteristics Of Water Vapor Based On Terahertz Time-Domain Spectroscopy

THz wave is a kind of electromagnetic wave whose frequency ranges from0.1 THz to 10 THz. The special properties of Terahertz make it have a broad application prospect in biomedicine, nondestructive testing, security testing and mobile communications,especially,the field of mobile communication.With the requirements on data transmission rate increasing,development of high frequency carrier is an inevitable trend to meet the large data transmission.However,the application of THz in communication and radar which are associated with data transmission are closely related to atmospheric transmission characteristic of terahertz radiation.The absorption and attenuation of THz in the atmosphere are mainly caused by water molecules.So investigating THz transmission effects of water vapor is an important basis for determining atmosphere window position and width. The experimental sets up transmissive THz-TDS system based on the terahertz time-domain spectroscopy Technology.The transmission distance is 0.5m, 1m,2m, 3m and humidity is in rang of 0-80% in closed environment.Equivalent time sampling principle is used to detect terahertz time-domain waveform. Lab View software is developed to collect and store experimental data. First, processing way of time- domain data is Fourier transforme transform, in order to extract the amplitude and phase information in the frequency domain.Calculation of absorption coefficient and transmissivity parameters in different humidity and different transmission distance uses the classic theory which is employed to extract the material optical parameters.This method is thought out by L.Duvillaret and T.D.Dorney.Through large amount of data analysis,terahertz time-domain spectroscopy peaks decrease, transmission rate of Atmosphere windows decreases and transmission window is compressed in intensity with increasing humidity.As terahertz transmission distance increases in the water vapor, transmission rate of each window is gradually decreased and transmission window is compressed.