Modeling, analysis and testing of an electrostatically actuated waveguide based optical MEMS device for variable optical attenuation
Electrostatic actuation is a promising solution for Micro Electro Mechanical Systems because of its good scaling properties in small dimensions, high-energy densities and relative ease of fabrication. Its low response time and compatibility with IC technologies make it even more suitable for the opt...
| Summary: | Electrostatic actuation is a promising solution for Micro Electro Mechanical Systems because of its good scaling properties in small dimensions, high-energy densities and relative ease of fabrication. Its low response time and compatibility with IC technologies make it even more suitable for the optical applications, such as, optical switching and Variable Optical Attenuators (VOAs) in telecommunications. Variable Optical Attenuators are very important components in fiber optic communication systems needed throughout the network to control optical power and prevent the saturation of receivers. This thesis describes the design of a novel and simple electrostatically actuated variable optical attenuator that uses the electrostatic actuation of a cylindrical waveguide. The proposed device stands out from the existing conventional optical attenuators by directly moving the input waveguide for creating misalignment and thus eliminating the need for extra optical components required in free space. This model has capability for a high dynamic range of attenuation and has other advantages of low wavelength dependent loss and low back reflection. The optical MEMS device consists of a metal coated cylindrical waveguide positioned in a V-groove and overhanging at the end to act as a free standing cantilever. This work presents modeling, analysis and testing of the proposed device. The system has been defined accurately using coupled electromechanical models that take into account the capacitance of the cylindrical electrode configuration. The static and dynamic analyses of the system have been performed using the Rayleigh Ritz energy method. The developed electromechanical model is generic and could be applied to any cylindrical electrostatic actuator. The generality of the method has been demonstrated in this work by performing static and dynamic analysis on a carbon nanotube actuator and nano resonator, respectively, using the above model. To verify the feasibility of the method for optical attenuation parametric study is presented and the resulting static deflections, pull-in voltages, natural frequencies and finally achieved attenuation have been presented. Testing is a very vital component in the synthesis of a microsystem. Experimental testing is carried out in this work using non contact optical methods. Both static testing using optical microscope and dynamic testing using Laser Doppler Velocimetry have been performed on a prototype representing the proposed device. The experimental results of deflection were found to be in good agreement with the theoretical results from the model. |
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