Lithium Tantalate Pyroelectric Terahertz Detector Readout Circuit Design

Terahertz radiation(THz)has been usually defined as a kind of electromagnetic radiation with the frequency between 0.1 and 10THz(wavelengths between 3?m and 3 mm),which lacks enough research and explorations in electromagnetic spectrum recently.THz has many unique and special properties,such as low energy,high penetration for many materials,spectral resolution and so on.These characteristics have promoted great applications of THz science and technology in the field of Nondestructive Testing,THz communication,Military radar,Explosives and Weapons detection,etc.THz detection technology has been one of the important directions in the development of THz science and technology.The pyroelectric detector has become the research hotspot of THz detection technology in recent years,owing to its special properties of simple structure,flexible system,smaller,uncooled and easier integration,etc.The paper has done deep and detailed analysis on the detection principle of pyroelectric THz detector and the design of signal processing circuit,and explored the related performance tests and readout circuit of the pyroelectric terahertz detector,of which the main content is introduced as follow:Firstly,we analyzed detection mechanism of pyroelectric THz detector,on the other hand,the theoretical deduction and calculation were carried out considering sine-wave and squared-wave modulated THz sources.Besides,the process of detection mechanism of pyroelectric THz detector and the respond signal waveform was discussed.Secondly,Lithium tantalate(LiTaO3/LT)pyroelectric detector,as the detection module of THz detector,was designed and produced.Based on the produced LT detector,we designed the matched and automatically adjustable preamplifier gain circuit.Then,we set up the test platform and measured the related performance parameters of the detector.The results of measurement show that the circuit can achieve the circuit function of automatic gain adjustment and detect THz radiation energy as low as 1?J,which can keep low noise,high gain and S/N ratio at the same time.It can also realize the detecting goal that THz radiation energy varies in a large dynamic range change from 1?J to 1000?J(60dB),which can keep the responsivity higher than 1000V/J.Thirdly,based on the detailed analysis of the measurement method of pyroelectric coefficient,the test system including software and hardware modules was designed out.The system was composed of pyroelectric current acquisition module,temperature collect module,MCU controller and upper computer module.Besides that,the test platform and measured pyroelectric coefficient of lithium tantalate crystal were set up.The graph that showed how pyroelectric coefficient changed with temperature was plotted,and the average of coefficient around 223.75?C/K·m2 was calculated.At last,we analyzed the results and compared the value with others literature.