Optimization Design Of Fast THz-TDS Signal Detection System

Since the 1980 s,Terahertz(THz)technology has been developing rapidly,and its academic and application value has attracted worldwide attention.Research institutes and universities have carried out research work in the field of THz.Terahertz time-domain spectroscopy(THz-TDS)is of great significance in the development of THz technology.THz-TDS can detect amplitude and phase information at the same time,and has wide application prospect in material detection and object imaging.The THz-TDS system signal detection and acquisition rate restricts the THz-TDS application technology development,whether can realize the fast scan is the THz-TDS technology urgently to solve one of the problems,and THz-TDS systematic instrumentation and miniaturization is the future development Direction.In order to realize the fast THz-TDS system and improve the signal detection and acquisition rate of Hz-TDS system,the optical delay line device and signal detection system in THz-TDS system are optimized.The main work and innovation of this paper are as follows:1.According to THz-TDS photoconductive method to generate and detect the principle of THz signal,the THz-TDS signal detection system was optimized.The optimized lock-in amplifier circuit realizes the center frequency,Q value and the reference signal phase adjustable.For the data acquisition part of the data acquisition system design of the overall program,including data acquisition system hardware and software design.2.The basic principle of the delay line device,the assembling error of the mechanical device and the output spot error of the delay line device are analyzed.Based on the analysis result,the assembly and adjustment method of the delay line device is summarized to realize the optimization of the fast optical delay line device.3.The simulation of THz-TDS signal detection system is carried out.The simulation results show that the lock-in amplifier can adjust the phase-lock parameters.The signal detection system can detect the weak low-frequency signal,detection signal SNR 90 db or more.4.Experimental measurement of high-speed and high-stability delay line devices.The experimental results show that the size and position of the exit spot are small,and the adjustment accuracy of the delay line device is high,which is in accordance with the theoretical analysis.At the same time,the delay line device can achieve scanning frequency 100 Hz,delay time 167.45 ps,stationary error of 0.25%,linearity error of 0.05%,can achieve high-speed and high-stability scanning.