Design And Fabrication Of The F-P Cavity Tunable Infrared Filter With 128×128 Array Based On MEMS Technology

Hyperspectral infrared images are getting attentions widely from both the domestic and aboard due to their high spectral resolution. Hyperspectral imager is leading edge and special topic of the spectral imaging technique field. The conventional prismatic way uses dispersive optics(gratings or prisms) or fourier transform spectrometer(FTS) to generate the spectral information. The disadvantages of conventional hyperspectral sensors include their size, weight, and computational requirements. In this thesis, we have successfully developed the micro-bridge structure of tunable 128×128 large array F-P air cavity filter by MEMS technology. The major research achievements and contributions of the dissertation are summarized as follows:Firstly, base on MEMS technology, development of 128×128 large array F-P air cavity tunable filter for hyperspectral imaging system. The advantage is that the novel chip scale dispersion element can be easily to integrate with focal plane array(FPA) detector. It has miniaturization and light-weight trend. The filter arrays have the potential to replace the traditional dispersive element for hyperspectral imaging.Secondly, optimization of the F-P cavity architecture design based on electrostatic actuation. Optimization of F-P cavity filter element model. Design of the four types F-P cavity structure. We have simulated the mechanical characteristics and optimized the F-P filter structures by multi-physics FEM COMSOL software. Analyze of the parallel structure, displacement changes, Von Mises stress, and fill factor. A conclusion is drawn that fold arm supporting structures are important to mechanical performance optimization. It can provide the theoretical foundation optimization design to the device.Thirdly, optimization of optical design for the F-P cavity optical mirrors. Design of the DBR mirrors for the F-P cavity by TFCale software. On the spectral range 3~5?m, considering the F-P cavity microbridge structure cantilever bearing capacity, 3 layers membrane system with Ge/Al2O3/Ge is designed, which realize combinational optimization of both optical performance and mechanical properties.Fourthly, development of the fabrication process. Based on the characteristics to a 128×128 F-P cavity filter array structure and surface micro machining technology, magnetron sputtering method is appled for structure layer growth, electron beam evaporation is used for preparation of DBR mirror, and pattern fabrication is obtained by the lift-off process. The fabrication process studies are mainly focused on the micro-bridge structure, sacrificial layer technology, DBR mirror process. Through a large number of experiments to fabricate the ideal microbridge structure and high reflectivity mirrors. The developed process can be easily compatible with conventional CMOS process.Fifthly, characterization of the developed F-P filter, electrical properties, mechanical properties, and optical properties were tested. The scanning electron microscope(SEM) pictures of the filter array were shown that the filter array is uniform and complete structure, and a suspended microbridge has been successfully fabricated. A testing platform was setup for performance testing, the F-P array filter was powered by direct current and voltage change is 0V~10V~0V. The test results show that F-P cavity microbridge structure has excellent parallelism and flexibility, and are in consistent with the simulation results. The new filter can realize large tuning range, low driving voltage, and high transmittance spectrum.