| As an important part of infrared gas sensor,Fabry-Perot tunable filter(FPTF)has a wide range of application scenarios in the field of gas detection.In recent years,air pollution has become increasingly serious,and there is an increasing demand for gas sensors with good portability,high stability,and low prices.FPTF can be manufactured using micro-electromechanical system(MEMS)technology,which has huge advantages in terms of miniaturization and high integration.This thesis takes FPTF as the research object,and carries out cantilever structural design and membrane system design,and carries out experimental verification.The main findings are as follows:First,the structure of FPTF is designed.In this thesis,a movable mirror structure supported by a double-folded cantilever is designed.Using finite element software for simulation,the influence of double-folded cantilever with different geometric shape grooves on the performance of the movable mirror was analyzed.The results show that the mirror supported by the rectangular double-folded cantilever has the maximum displacement at 8 V,which is 0.88 ?m,it is higher than the displacement of the mirror supported by the trenchless double-folded cantilever at the same voltage by 95%.Moreover,when the displacement of the mirror is 0.5 ?m,the flatness of the mirror supported by the rectangular double-folded cantilever is the best during the tuning process,and the value of flatness is 0.0032°.Secondly,the optical design software was used to simulate the FPTF membrane system,and the effects of different membrane materials,periodic repetition times and incident angle on the highly reflective membrane system in the filter were studied.The results show that the higher the refractive index ratio of the high refractive index membrane materials to low refractive index membrane materials,the greater the number of periodic repetitions,and the smaller the incident angle will lead to the higher the reflectivity of the high reflective membrane system.The effect of the incident angle on the performance of the anti-reflection coating is also studied.The results show that,as the reflection angle increases,the minimal reflectivity of the anti-reflection coating shifts to the short wavelength region.After determining the influencing factors such as membrane materials and multilayer structure,the overall simulation of FPTF was performed.The results show that when the center wavelength was 4 ?m,the peak transmittance of FPTF was 99.7%,and the full width of half maximum was 5 nm.Analyze the error of the whole membrane system,and set a random error of 0.1% for each membrane layer.The results show that in 10 simulations,the center wavelength of the filter does not change more than 0.5 nm,and the transmittance curve does not change significantly.Finally,combining the displacement results of the mirror under different voltages in the structural design and the membrane design of the filter,the optical performance of the FPTF under different tuning voltages is analyzed.The results show that the actual tunable range of the FPTF of this design is 3.48 ~ 4.69 ?m.During the tuning process of the filter,the full width of half maximum varies from 5 to 12 nm,and the peak transmittance varies from 92% to 97%.And when the center wavelength is close to 4 ?m,the peak transmittance of the filter is the largest and the full width of half maximum is the smallest.The high reflection membrane of FPTF was fabricated to verify the simulation results,and the experimental results show that the average reflection rate of the prepared high reflection membrane in the range of 3.3 ~ 6 ?m reached more than 99%.An FPTF with a cavity length of 2 ?m was prepared with a center wavelength of 4 ?m,and its filter performance was tested.The results show that the center wavelength of the filter is 4150 nm,the peak transmittance is 64.2%,and the full width of half maximum is 100 nm. |
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