Research On The Processing Technic Of 0.22THz Folded Waveguide

Terahertz wave refers to electromagnetic wave with frequency ranging from 0.1to 10 THz(wavelength ranging from 3mm to 30um).It has many unique properties.Terahertz wave has short wavelength and high spatial resolution.It also has good ability of penetrating dust,smoke and non-metallic materials.Low photon energy of and no ionization like X-ray are also the advantages of terahertz wave.It will not destroy the substance and so on.Based on these unique characteristics,terahertz technology has been widely used in radar,satellite communications,remote sensing,land security,anti-terrorism detection,medical diagnosis,environmental monitoring and other fields.As a hot topic of current research,terahertz has attracted wide attention because of its special physical properties.The development of terahertz devices has become the frontier research direction of many scientific research institutes.In the field of terahertz electro-vacuum devices,with the continuous improvement of the working frequency of TWT,the size of its components is smaller and smaller.And it is more and more sensitive to the processing accuracy.Small errors will have a great impact on the standing wave interaction,and then affect the output power of the whole TWT.When the frequency of vacuum electronic devices reaches 200 GHz,the traditional processing methods are no longer applicable.And the micro-fabrication method of MEMS in microelectronics technology is necessary.Generally practical manufacturing methods include Ultra-fine WEDM technology,LIGA technology,UV-LIGA technology and DRIE technology.Among them,UV-LIGA technology and DRIE technology have attracted widespread attention because they can be extended to the processing of structural sizes up to 1 THz or even dozens of THz.As one of the key devices,0.22 GTHz folded waveguide device has many special requirements,such as large depth-width ratio,high surface roughness requirement,all-metal structure and sealing.The symmetry between the internal electron beam channel and its shape will directly affect the flow rate of the electron beam.It is also the precondition of guaranteeing the performance of the whole pipe.All these conditions put forward stringent requirements for the processing accuracy of folded waveguides and higher requirements for the processing methods of folded waveguides.In this paper,the fabrication method of 0.22 GTHz folded waveguide is discussed and analyzed,which lays a foundation for the subsequent fabrication of folded waveguide in higher frequency band.The main research work and innovations of this paper can be summarized as follows.(1)The challenges and solutions faced by UV-LIGA in processing high aspect ratio,high surface roughness requirements and complex three-dimensional all-metal sealing structures were studied.(2)The advantages and disadvantages of UV-LIGA processing technology and mechanical processing technology in processing complex structures were compared.The essential difference between the two methods is presented objectively and clearly through the processing example of 0.22 THz folded waveguide slow wave structure.(3)By comparing the UV-LIGA processing technology with the mechanical processing technology,the two methods are combined to achieve wider processing capacity,shorter processing cycle and processing capacity oft more complex structure.