Finite Element Analyses Of Some Photon And MEMS Devices

The rapid development of optical fiber communication network put forward a high demand on the performance of related photon devices. Meanwhile micro-electronic mechanic systems (MEMS) are getting more and more wide applications in such fields as microwave, automobile industry, biomedicine and environment monitoring. Using finite element method, the theses carried out a detailed study on such devices as wave-guide Mach-Zehnder thermal-optical switches, LiNbO₃ electro-optical modulators and cantilever type MEMS switches. The relationship of the performance of these devices with their structure parameters were simulated, which are very useful for their optimum design.Firstly, thermal dynamic analyses of the wave-guide Mach-Zehnder thermal-optical switches made of such material as silicon on insulator (SOI) and PMMA were conducted. As the numerical results shown, the energy consumption of a SOI switch is around 0.15 W, the rising and falling times of the switch are 120μs and 100μs respectively. While the energy consumption of a PMMA wave-guide Mach-Zehnder thermal-optical switch was found as low as 3.7mW, which is about two orders lower than that of a SOI switch. However the rising and falling times of the PMMA switch are 16ms and 19 ms.Secondly, static electrical analyses of the conventional and new LiNbO₃ electro-optical modulator were conducted. It was found that it is hardly possible to achieve simultaneous optimum phase and impedance match with a conventional LiNbO₃ electro-optical modulator. However with T-shape electrodes, ridged waveguides and air back pith, a new LiNbO₃ electro-optical modulator offers easy phase and impedance match. As a result an optimum structure was found which ensures a 3dB frequency band width as wide as 98GHz, a characteristic impedance of 52Ω, half wave voltage 7.13V, which is much better that that of a conventional LiNbO₃ electro-optical modulator.Finally, by means of iterative mechanic and static electro analyses the behavior of a cantilever type MEMS switch was investigated. The relation between the deformation and the applied voltage under various geometric parameters was studied and the minimum driven voltage was found to be as low as 5V.The numerical results were in accordance with existing theoretical and experimental results and could be used as a reference for the design of these devices. Simulation of many other devices using finite element method could be performed in a similar way.