Research On Room Temperature Terahertz Focal Plane Detector Testing And Imaging System

The terahertz(THz)wave is a type of electromagnetic wave with the frequency of 0.1~10 THz and the wavelength of 30μm~3mm.Compared with other electromagnetic waves,THz wave has many unique properties,such as high penetration,wide broadband,lower energy and spectral identification capability.THz detection technology has been widely used,not only in the field of military communication and aerospace vehicle nondestructive testing,but also in civilian are such as security inspection,biomedical science,explosive detection,spectrum analysis,etc.THz technology has been paid more and more attention to currently in the world as a promising technology.In the past 20 years,with the rapid development of THz technology,there is higher requirement for the THz detection and the detector’s performance.In order to meet this requirement,it is essential to carry out the research on the room temperature THz detector and its test verification imaging.This study focuses on THz devices and detection at room temperature based on vanadium oxide(VOX)micro-bolometer,with detailed research on the design and simulation of micro-bolometer,enhancement of THz absorption,THz detection unit and detector testing,and THz wave imaging.This study showed certain break-through in the key technologies such as enhanced absorption,testing and imaging verification of THz wave,by manufacturing THz detection with a 320×240 array detection device at room temperature,setting up related testing system,and achieving the detection of THz wave inspired by THz radiation source at room temperature.The main research contents and results are as follows:1.Optimization design of THz micro-bolometer with a micro-bridge structure.As the traditional micro-bolometer had lower absorption rate and smaller response,a layer of metal film was applied on the top-level of the micro-bridge structure as the THz radiation absorbing layer.The simulation results of this metal film demonstrates that it was effective in absorption of THz radiation,and achieved the maximum absorption through optimization of those parameters,such as conductivity and the thickness of the metal absorption layer.The optical simulation results of the unit membrane structure showes the absorption rate increasement of THz radiation through elevating the height of the optical resonator.Based on the DOE method,the residual stress simulationusing Intelli Suite software showes a minimum deformation of micro-bridge unit which was 0.0385 μm,when the stresses on the support layer,the passivation layer,the electrode layer,the sensitive layer and the absorption layer were optimized to 200 Mpa,200 Mpa,200Mpa,0Mpa,-400 Mpa,respectively.2.As the THz radiation absorption layer had inefficiency in radiation resorption,the thickness of Ni Cr film was optimized to achieve the maximum absorption of THz radiation at different frequencies.The surface micro-structure of Ni Cr film modified by RIE technology increased the effective absorption area and enhanced the THz absorption rate.High resonant cavity was designed to increase the THz micro-bridge resonator,when matching the 1/4 wavelength.All these studies provids a simple and effective method for THz devices at room temperature,which are compatible with MEMS preparation technology.3.We manufactured the micro-bolometer pixel,finished assembling of micro-bolometer in high vacuum dewa and fabricated the 320×240 room temperature THz detector.4.THz detection unit and detector testing system was established using high power THz laser as the radiation source.The testing of THz micro-bolometer unit showes that noise equivalent power(NEP)was higher than 140.98pw/Hz1/2,and the average response time was 4.96 ms.The performance testing of the packaged THz devices showes that the RMS noise was 615μV and NEP was 144.3p W/Hz1/2.5.A THz imaging system was established based on a 320×240 THz focal plane detector at room temperature,which included the THz radiation source,the optical system and the detection system.The detection system with monolithic FPGA integrated hardware structures had parameter calibration and real-time imaging integration.Meanwhile,this paper proposes a blind algorithm based on Newton interpolation,which can effectively restore the image details in the blind pixels.Compared with the traditional algorithm,a novel image enhancement algorithm based on the weight distribution has been proposed,which overcome the tensile distortion owing to the changes of detector status.We have verified the feasibility of THz imaging by the imaging of the clip,banknote,pencil,leaves,circular gasket and metal plate,which lay a solid foundation for the practical application of THz technology.