Study Of Fabry-Perot Tunable Optical Filter Employing MEMS Technology

Tunable optical filter is the key device of modern optical communication and sensor systems. With the advantages of small volume, high performance, and low cost, the Fabry-Perot (F-P) tunable filter employing the Micro-Electro-Mechanical systems (MEMS) technology is one of the most challenging among all optical tunable filter solutions. This thesis focused on the related theories of the MOEMS tunable filter as well as its fabrication techniques.The conventional theory of the F-P Interferometer was introduced firstly, and then the reflectivity and reflection phase shift of quite a few kinds of dielectric films consisting of quarter wave stacks were calculated. The influence of the reflection phase shift and its dispersion on the optical performance of the short-cavity (SC) F-P interferometer was analyzed in details. The free spectral range (FSR) shortening effect in the SCF-P interferometer was theoretically proved for the first time, which matched the experimental data very well.By combining with the precise and stabile characteristics of piezoelectric driving and the batch fabrication advantage of the MEMS technology, a novel F-P tunable filter was proposed and designed. The parallelism of the two F-P reflection mirrors can be well controlled by the proposed structure. Three fabrication processes, including (i) wet etching, (ii) the selective epitaxial growth (SEG) on silicon wafers, and (iii) using silicon on insulator (SOI) wafers, were studied.The F-P cavities employing the wet etching process was fabricated for the first time. The insertion loss were about 8dB, the full width at half maximum (FWHM) about 1.5-2 run, and the finesse more than 50. The high parallelism of the two reflection mirrors was automatically achieved without applying addition electrostatic control.The application of the SEG process on the MEMS field was explored and the effort to fabricate F-P based optical devices employing the SEG technology was made. The phenomenon appeared in the SEG experiments were summarized, some of which were firstABSTRACTobserved.A novel F-P tunable filter driven by using piezoelectrics was fabricated with the SOI material. By employing simple wet anisotropic etching process and metal sputtering (or evaporating) process, the electrical interconnect between the electrodes on both sides of the silicon wafer was realized for the first time.The measured results showed that the insertion loss of the tunable filter was about 8 dB, the FWHM about 5 nm, and the transmitted peak red shifted about 20 nm. The test results were analyzed. The further measures to improve the performance were also discussed in this thesis.