Progress on femtosecond laser-based system-materials: three-dimensional monolithic electrostatic micro-actuator for optomechanics

Femtosecond laser-dielectric interaction in a three-dimensional (3D) manner defines a capable platform for integrated 3D micro-devices fabricated out of a single piece of system-material. Here, we add a new function to femtosecond laser-based single monolith in amorphous fused silica by demonstrating a transparent 3D micro-actuator using non-ablative femtosecond laser micromachining with subsequent chemical etching. The actuation principle is based on dielectrophoresis (DEP), defined as the unbalanced electrostatic action on dielectrics, due to an induced dipole moment under a non-uniform electric field. An analytical model of this actuation scheme is proposed, which is capable of performance prediction, design parameter optimization and motion instability analysis. Furthermore, the static and dynamic performances are experimentally characterized using optical measurement methods. An actuation range of 30 mu m is well attainable; resonances and the settling time in transient responses are measured; the quality factor and the bandwidth for the primary vertical resonance are also evaluated. Experimental results are in good consistence with theoretical analyses. The proposed actuation principle suppresses the need for electrodes on the mobile, non-conductive component and is particularly interesting for moving transparent elements. Thanks to the flexibility of femtosecond laser manufacturing process, this actuation scheme can be integrated in other functionalities within monolithic transparent Micro-Electro-Mechanical Systems (MEMS) for applications like resonators, adaptive lenses and integrated photonics circuits.