| Micro Fabry - Perot tunable filter based on MEMS technology will be widely used in the area of hyperspectral imaging and DWDM optical communication system. Compared with other tunable filters, it has the advantages of small volume, easy to integrate with lasers, detectors or modulators, large tunable spectral range, high spectral resolution, and low cost because of batch manufacturing. This paper presents the research of this filter. From theory research, structural design, simulation analysis to final fabrication process, are all explored. The main contents are as follow:Firstly, this article introduces the conventional theory of the F-P tunable filter. Then according to the practical requirement, the author designs the optical structure of F-P cavity. In the whole 3-5μm spectral tuning range, the peak transmittance rate is between 88% - 96%, and the full width at half maximum (FWHM) is between 107-147nm. Some characteristics of the device result from short cavity are also discussed.Secondly, the author has chosen one micro F - P bridge structure from several common designs. The driving performance of this micro bridge structure, as well as the parallelism and stability of the device is simulated by using finite element analysis method. The simulation result shows that this micro bridge can achieve 542.9nm tuning range under the driving voltage of 29V.Thirdly, the whole device is fabricated by using surface MEMS technology. In the fabrication process, polyimide is used as a sacrifice layer material, and is flatten by spinning another phtotoresist on the chip and followed with a reactive ion etching (RIE). Experiment results show that the flatness of filter's effective area is less than 20nm.Finally, the performance of the device is tested. Results show that a suspended micro bridge has been successfully fabricated, and the peak transmittance rate is 53.8%, FWHM is 254nm. The author has analyzed the causes of some existing problems, and put forward the further improvement scheme. |
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