Tao Yang
The last few decades have witnessed exciting advances in micro-opto-electro-mechanical systems (MOEMS) including revolutionary development of fabrication processes and an ever increasing expansion of their domain of applications. In parallel, femtosecond laser processing of materials has emerged as a capable three-dimensional (3D) fabrication tool for producing various functional components, particularly interesting for microengineering applications. However, the investigation of 3D actuation principles remains largely unexplored despite their relevance. Moreover, for the particular applications of MOEMS, actuation principles combining optical functionalities with mechanical ones, and this over a broad optical spectral range - including the visible spectra, are of high interest as it would enable further miniaturization and integration in micro-devices. In this regard, this thesis work focuses on the realization of using femtosecond laser microprocessing for designing, fabricating, and modulating 3D transparent dielectric actuators and resonators. First, we demonstrate experimentally the design and fabrication of monolithic 3D cantilever actuators excited by dielectrophoresis force. The actuator requires no electrodes on the movable dielectric components and is particularly interesting for guiding light in broad visible and infrared spectra. Second, we investigate the use of non-ablative femtosecond laser irradiation to tune and modulate the nonlinear oscillation properties of double-clamped beam resonators. A remarkable tunability in the nonlinear stiffness, resonance frequency, and linear dynamic range is achieved, opening up a passage for developing tunable optomechanical devices. Third, we develop a complete theoretical framework for analyzing these systems, and in particular, the complex linear and nonlinear dynamical behavior of dielectrophoretically excited suspended beams. The results are generic and can be expanded to other actuation principles and constructions. Finally, we illustrate our findings with real 3D actuations, which are almost impossible to realize using traditional manufacturing techniques. This thesis work holds promise for both research and industrial applications. It enriches the functionalities of laser-machined devices and enables the creation of all transparent optomechanical systems of actuation and photonic functions. The development of tunable micro-resonators opens up new avenues for investigating advanced nonlinear dynamics.
EPFL2017
