Guided-wave micro-electro-mechanical systems (MEMS) optical switches for telecommunication applications

The present thesis deals with Micro-Electro-Mechanical Systems (MEMS) optical switches for telecommunication applications. The aim is to study new type of microsystems for guided-wave optical switching applications. Two projects have been investigated. The first part addresses a novel technological and design study of N×N optical switch integration with planar waveguides and vertical displacement micro-mirrors. Novel suspended MEMS mechanical platform on SOI wafer were designed and realized and technological processes for optimization of micro-mirrors quality have been developed. The motivation of this study was related to initial collaboration with the company Memscap S.A. which was looking for compact and fast N×N optical switches based on planar waveguides. One of the key issue being waveguide integration, a concept of a hermetic packaging with two wafers assembly where a waveguide wafer is placed face down on top of MEMS electrostatic devices with vertical micro-mirrors has been developed. Vertical micro-mirrors have been fabricated in SU8 photopolymer or in single crystalline silicon. For integration of silicon mirrors, a new simple two-steps DRIE pattern transfer that allow simultaneous fabrication of good quality silicon mirrors and of recessed mechanical platform has been demonstrated. The platform has been analysed through its resonance behaviour. The strong effect of mechanical non-linearity which was observed in clamped suspension can be exploited to increase the control range of the electrostatic actuator. During the first part of this work on MEMS optical switches based on planar waveguides, a totally new approach that use hollow waveguide instead of solid core waveguide has been developed. The primary motivation was whether it was possible to integrate a micromechanical switch composed of a vertical silicon cantilever beam mechanism inside the air core of the hollow waveguide. Silicon Planar Hollow Waveguides (PHW) have been designed, realized and tested with different optical coatings: a metallic gold coating, dielectric bilayers based on the principle of AntiResonant Reflective Optical Waveguide (ARROW) and bare silicon. The influence of ARROW layers on hollow planar waveguides has been investigated. The very first PHW with integrated 1×2 optical switching have been manufactured and characterized. Switching times better than 10 μs were measured with the produced devices. The switching speed was about 100 times higher to other MEMS optical switches based on micro-mirrors.