| With the rapid development of social economy and technology,the demand for infrared polarization detection is increasing day by day.And this technology has been penetrated into all aspects of national life and has shown important application value.Among the components of the infrared polarization detection system,the polarizer is a key component for sensing the polarization information which was carried by the measured object,and it plays an important role in the system.However,along with the continuous renewal of infrared technology,the polarization imaging detection system has been further developed,and the miniaturization,miniaturization and even integration of the system have become the development trend of the current era.Furthermore,facing with the size reduction of the polarization detection system or photosensitive area reducing of the corresponding photodetector,the traditional infrared polarizer has gradually failed to meet the current needs of the usage,thus it is urgent to find an optical equipment with small volume and good polarization performance as the alternatives.However,the nano-metal grating exhibits excellent polarization performance due to the characteristic of the period less than the operating wavelength,so that the device can be become a substitution to replace the conventional infrared polarizer.Based on these analyses,this paper is devoted to using micro-nano processing to fabricate the infrared nano-metal gratings which satisfy the performance requirements of polarization detection systems.Firstly,the effects of various parameters of single-layer infrared nano-metal grating with respect to its polarization characteristics were explored based on the finite difference time domain theory,such as metal material,grating period,duty ratio,metal layer thickness and grating cross-section structure.And the results were qualitatively explained in the physical sense through equivalent medium theory.Secondly,we studied the effects of various process parameters on the preparation of grating structure,such as cleaning and surface modification of base material,thermal nano-imprinting process,ultraviolet-thermal nano-imprinting process and metal film deposition process-vacuum thermal evaporation process,as well as we also optimized partial parameters.Combined with the above process,a multi-directional array infrared nano-metal grating was prepared.Its TM transmittance is greater than 70% in the 2.5-5?m,and its extinction ratio is more than 30 dB in the 2.7-5?m,especially it exceed 35 dB in 2.72-3.93?m wavelength range.Meanwhile,aiming at the defects of the nano-metal grating which is fabricated on hard substrate,such as poor compatibility with non-planar devices,through using IPS material with properties of deformation capacity and good transmittance,we fabricated the flexible infrared nano-metal grating,and further expanded its applicable occasions and scope.Finally,in order to improve the polarization performance of the grating,the principle of antireflection(AR)coating was researched and the transmittance calculation method was studied.We also compared the transmittance of the single-sided AR coating design and the double-sided AR coating design through using MATALB program.Based on the above simulation results,we adjusted and improved the fabrication process,and the infrared nano-metal grating with double-sided antireflection film was re-fabricated.The results of the test show that its TM polarization transmittance is over 80% in the 4.48-4.65?m,which is improved compared with the previous one. |
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