Design And Fabrication Of Terahertz Antireflection Window

With the further development of large-scale integrated circuit technology,binary optical technology can be used to produce smaller and smaller graphics sizes and the more sophisticated lines.The subwavelength structure based on binary optical technology provides a new idea for the design of the transparent window,therefore attracts many scholars engaged in optical transmittance research.Subwavelength enhancement structure is a periodic relief structure.The characteristic dimensions of the structure is equal to or smaller than the wavele ngth of a specific working wave..Its most important feature is that the device only exists zero-order diffraction diffraction and transmission diffraction when its periodic structure size is small enough,so the diffraction efficiency is higher than the general diffraction optics.Another feature of this structure is that the transmittance and reflectivity can be changed by changing the size of the relief structure,the size of the duty cycle,and the size of the height.In this paper,the sub-wavelength enhancement structure is optimized by combining the effective medium theory(EMT)and the rigorous coupled-wave analysis(RCWA)theory,and the terahertz-increasing window is made by experiments,which effectively improve the window transmissivity-rate when the terahertz frequency is 1.7T.The main contents of this paper are as follows:(1)Introduced the concept of terahertz waves and terahertz sensors,as well as the development of binary optics.The theory of sub-wavelength enhancement structure is introduced,and it is pointed out that scalar diffraction theory is no longer suitable for subwavelength structure,and vector diffraction theory should be used.(2)Introduced the effective medium theory,and the zero-order equivalent refractive index and the second-order equivalent refractive index of one-dimensional and two-dimensional subwavelengths are deduced by this theory.The periodic thresholds for subwavelength diffraction are discussed.The rigorous coupled-wave analysis(RCWA)theory is introduced,and the transmittance and reflectivity of the two-dimensional subwavelength columnar structure are deduced by this theory.(3)Combined the effective medium theory(EMT)and the rigorous coupled-wave analysis(RCWA)theory,using MATLAB programming to simulate the double-sided terahertz-enhanced window structure with the lowest reflectivity in theory.Using L-Edit to draw the corresponding pattern and mak ing the mask.The whole calculation process provides a valuable reference for the future design of the terahertz window.(4)Described the lithography process and details of the terahertz window through the specific production steps and process.Due to the deep etching depth,the photoresist is not enough to act as a mask layer.It is suggested that a layer o f silicon nitride can be used as the mask layer for etching silicon,deep silicon etching with ICP,and silicon nitride Etching.The entire production process provides some reliable reference for the microfabrication process.(5)The transmittance test was performed on a well-formed single-sided,double-sided reinforced structure by using a terahertz time-domain spectrometer(THz-TDs).By analyzing the test results,the test results show that when the terahertz frequency is 1.7T,the transmittance of single-sided binary optical-enhanced structure is 57.52%,and the transmittance of double-sided binary optical structure is 68.15%,both of them have a certain increase when them are compared to the body of silicon.