Microfabricated torsional actuator using self-aligned plastic deformation

We describe microfabricated torsional actuators that are made using self-aligned plastic deformation in a batch process. The microactuators are formed in single-crystal silicon and driven by vertical comb-drives. Structures have been built that resonate at frequencies between 1.90 and 5.33 kHz achieving scanning angles up to 19.2 degrees with driving voltages of 40 V_(dc) plus 13 V_(ac). After continuous testing of 5 billion cycles at the maximum scanning angle, there appears to be no observable degradation or fatigue of the plastically deformed silicon tors ion bars. We present measured results obtained with MEMS scanning mirrors; the actuators may be useful for many other MEMS applications

Microfabricated Torsional Actuators Using Self-Aligned Plastic Deformation of Silicon

In this paper, we describe angular vertical-comb-drive torsional microactuators made in a new process that induces residual plastic deformation of single-crystal-silicon torsion bars. Critical dimensions of the vertically interdigitated moving-and fixed-comb actuators are self-aligned in the fabrication process and processed devices operate stably over a range of actuation voltages. We demonstrate MEMS scanning mirrors that resonate at 2.95kHz and achieve optical scan angles up to 19.2 degrees with driving voltages of 40V_(dc) plus 13V_(pp). After continuous testing of five billion cycles at the maximum scanning angle, we do not observe any signs of degradation in the plastically deformed silicon torsion bars

MEMS micromirrors for imaging applications

Strathclyde theses - ask staff. Thesis no. : T13478Optical MEMS (microelectromechanical systems) are widely used in various applications. In this thesis, the design, simulation and characterisation of two optical MEMS devices for imaging applications, a varifocal micromirror and a 2D scanning micromirror, are introduced. Both devices have been fabricated using the commercial Silicon-on-Insulator multi-users MEMS processes (SOIMUMPs), in the 10 m thick Silicon-on-Insulator (SOI) wafer. Optical MEMS device with variable focal length is a critical component for imaging system miniaturisation. In this thesis, a thermally-actuated varifocal micromirror (VFM) with 1-mm-diameter aperture is introduced. The electrothermal actuation through Joule heating of the micromirror suspensions and the optothermal actuation using incident laser power absorption have been demonstrated as well as finite element method (FEM) simulation comparisons. Especially, the optical aberrations produced by this VFM have been statistically quantified to be negligible throughout the actuation range. A compact imaging system incorporating this VFM has been demonstrated with high quality imaging results. MEMS 2D scanners, or scanning micromirrors, are another type of optical MEMS which have been widely investigated for applications such as biomedical microscope imaging, projection, retinal display and optical switches for telecommunication network, etc. For large and fast scanning motions, the actuation scheme to scan a micromirror in two axes, the structural connections and arrangement are fundamental. The microscanner introduced utilises two types of actuators, electrothermal actuators and electrostatic comb-drives, to scan a 1.2-mm-diameter gold coated silicon micromirror in two orthogonal axes. With assistance of FEM software, CoventorWare, the structure optimisation of actuators and flexure connections are presented. The maximum optical scan angles in two axes by each type of actuator individually and by actuating the two at the same time have been characterised experimentally. By programming actuation signals, the microscanner has achieved a rectangular scan pattern with 7° 10° angular-scan-field at a line-scan rate of around 1656 Hz.Optical MEMS (microelectromechanical systems) are widely used in various applications. In this thesis, the design, simulation and characterisation of two optical MEMS devices for imaging applications, a varifocal micromirror and a 2D scanning micromirror, are introduced. Both devices have been fabricated using the commercial Silicon-on-Insulator multi-users MEMS processes (SOIMUMPs), in the 10 m thick Silicon-on-Insulator (SOI) wafer. Optical MEMS device with variable focal length is a critical component for imaging system miniaturisation. In this thesis, a thermally-actuated varifocal micromirror (VFM) with 1-mm-diameter aperture is introduced. The electrothermal actuation through Joule heating of the micromirror suspensions and the optothermal actuation using incident laser power absorption have been demonstrated as well as finite element method (FEM) simulation comparisons. Especially, the optical aberrations produced by this VFM have been statistically quantified to be negligible throughout the actuation range. A compact imaging system incorporating this VFM has been demonstrated with high quality imaging results. MEMS 2D scanners, or scanning micromirrors, are another type of optical MEMS which have been widely investigated for applications such as biomedical microscope imaging, projection, retinal display and optical switches for telecommunication network, etc. For large and fast scanning motions, the actuation scheme to scan a micromirror in two axes, the structural connections and arrangement are fundamental. The microscanner introduced utilises two types of actuators, electrothermal actuators and electrostatic comb-drives, to scan a 1.2-mm-diameter gold coated silicon micromirror in two orthogonal axes. With assistance of FEM software, CoventorWare, the structure optimisation of actuators and flexure connections are presented. The maximum optical scan angles in two axes by each type of actuator individually and by actuating the two at the same time have been characterised experimentally. By programming actuation signals, the microscanner has achieved a rectangular scan pattern with 7° 10° angular-scan-field at a line-scan rate of around 1656 Hz

MEMS based catheter for endoscopic optical coherence tomography

Ph.DDOCTOR OF PHILOSOPH

Applications of programmable MEMS micromirrors in laser systems

The use of optical microelectromechanical systems (MEMS) as enabling devices has been shown widely over the last decades, creating miniaturisation possibilities and added functionality for photonic systems. In the work presented in this thesis angular vertical offset comb-drive (AVC) actuated scanning micromirrors, and their use as intracavity active Q-switch elements in solid-state laser systems, are investigated. The AVC scanning micromirrors are created through a multi-user fabrication process, with theoretical and experimental investigations undertaken on the influence of the AVC initial conditions on the scanning micromirror dynamic resonant tilt movement behaviour. A novel actuator geometry is presented to experimentally investigate this influence, allowing a continuous variation of the initial AVC comb-offset angle through an integrated electrothermal actuator. The experimentally observed changes of the resonant movement with varying initial AVC offset are compared with an analytical model, simulating this varying resonant movement behaviour. In the second part of this work AVC scanning micromirrors are implemented as active intra-cavity Q-switch elements of a Nd:YAG solid-state laser system. The feasibility of achieving pulsed laser outputs with pulse durations limited by the laser cavity and not the MEMS Q-switch is shown, combined with a novel theoretical model for the Q-switch behaviour of the laser when using a bi-directional intra-cavity scanning micromirror. A detailed experimental investigation of the pulsed laser output behaviour for varying laser cavity geometries is presented, also discussing the influence of thin film coatings deposited on the mirror surfaces for further laser output power scaling. The MEMS Q-switch system is furthermore expanded using a micromirror array to create a novel Q-switched laser system with multiple individual controllable output beams using a common solid-state gain medium. Experimental results showing the simultaneous generation of two laser outputs are presented, with cavity limited pulse durations and excellent laser beam quality.The use of optical microelectromechanical systems (MEMS) as enabling devices has been shown widely over the last decades, creating miniaturisation possibilities and added functionality for photonic systems. In the work presented in this thesis angular vertical offset comb-drive (AVC) actuated scanning micromirrors, and their use as intracavity active Q-switch elements in solid-state laser systems, are investigated. The AVC scanning micromirrors are created through a multi-user fabrication process, with theoretical and experimental investigations undertaken on the influence of the AVC initial conditions on the scanning micromirror dynamic resonant tilt movement behaviour. A novel actuator geometry is presented to experimentally investigate this influence, allowing a continuous variation of the initial AVC comb-offset angle through an integrated electrothermal actuator. The experimentally observed changes of the resonant movement with varying initial AVC offset are compared with an analytical model, simulating this varying resonant movement behaviour. In the second part of this work AVC scanning micromirrors are implemented as active intra-cavity Q-switch elements of a Nd:YAG solid-state laser system. The feasibility of achieving pulsed laser outputs with pulse durations limited by the laser cavity and not the MEMS Q-switch is shown, combined with a novel theoretical model for the Q-switch behaviour of the laser when using a bi-directional intra-cavity scanning micromirror. A detailed experimental investigation of the pulsed laser output behaviour for varying laser cavity geometries is presented, also discussing the influence of thin film coatings deposited on the mirror surfaces for further laser output power scaling. The MEMS Q-switch system is furthermore expanded using a micromirror array to create a novel Q-switched laser system with multiple individual controllable output beams using a common solid-state gain medium. Experimental results showing the simultaneous generation of two laser outputs are presented, with cavity limited pulse durations and excellent laser beam quality

Design, modeling and fabrication of thermal actuated micromirror for fine-tracking mechanism of high-density optical data storage

Master'sMASTER OF ENGINEERIN