Measurement Of The Pyroelectric Coefficient And Detector Performance Based On LiTaO₃ Crystals

Terahertz(THz) wave has certain properties, compared to other wave band, due to the special position in the electromagnetic spectrum, thus it has broad prospects for development and become a hotspot of international scholars. Pyroelectric THz detection belongs to the non-coherent detection technology, which has a simple system structure, wide operating frequency range, and the detector can work at room temperature without refrigeration.For the pyroelectric THz detection technology, the improvement of the response rate of the system and anti-jamming ability, is the key to the development of THz pyroelectric detector. To solve this problem, a pyroelectric coefficient test platform is designed to test the performance of pyroelectric material. Thus it can provide basis for the selection of the pyroelectric detector. In addition, the current model and voltage model prefix-operation amplification circuit was designed to amplify weak pyroelectric detector signal, and filtering. Finally, a kind of pyroelectric detector unit was designed. The performance of the pyroelectric detector unit was tested. Details are as follows:Pyroelectric coefficient test platform, which consists of high-low temperature test chamber, MCU minimum system, A/D conversion module, temperature testing module, amplification circuit module, serial communication module and display module, was based on a direct method. The pyroelectric coefficient of LiTaO3 was tested with temperature range from 37°C-48°C, the result shows that pyroelectric coefficient rang from 1.65 10-8C/cm2°C~3.08 10-8C/cm2°C. The results were conformed to related reports, verifying the feasibility of pyroelectric coefficient test platform.High-gain, low-noise, high-input impedance amplification circuit was designed. Voltage model amplification circuit(including the impedance matched circuit of PN4117 and amplification circuit of CA3140), current model(including AD549 and CA3140 amplification circuit) were designed in this paper. After testing their performance, filter modules were added to them. Within the scope of the pass band, the magnification of CA3140 amplification circuit is 4030, the attenuation of 50 Hz is-43 dB. The magnification of AD549 secondary amplifying circuit is 10~210. Current model circuit can give maximum linear distortion of current outputs.Pyroelectric THz detector unit was designed. Utilizing a high precision THz source as 2.52 THz output, the performance of the pyroelectric detector unit combined with voltage model amplification circuit was tested. The results were as follows: when the chopper was 5Hz, the detection of THz voltage response of the detector unit was 1.56 V, the noise was 530 uV, the noise equivalent power(NEP) was 6.8 10-9W/Hz1/2.