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The demand for miniaturized tactile sensing devices have greatly increased ever since the introduction of minimally invasive surgical (MIS) procedures. In this work, a tactile sensor is presented that provides essential artificial fingertip perception during such procedures. The proposed sensor can measure tactile information under various static/dynamic loading conditions by precisely measuring the quantity and position of a concentrated force, the local variation in force distribution, relative hardness and local discontinuities in the hardness of soft objects. The sensor, which is fabricated using fiber-optics and microsystems technology, can be used for most MIS tasks since it meets the necessary requirements of being electrically passive and magnetic resonance compatible. [ABSTRACT FROM AUTHOR]

The measurement of shearing force is increasingly important in the detection of slipping and the measurement of friction. In this paper, we propose a promising shearing force measurement device that is 16.3 mm × 2.9 mm × 6.0 mm, using an integrated micro displacement sensor and a trapezoidal external metallic frame. The optoelectronic subsection of the sensor is 6.5 mm × 6.5 mm, and is 1.6 mm thick. This subsection is used to measure the tilt angle of a mirror on the ceiling of the frame caused by the shearing force applied to the upper surface of the frame. We have been able to successfully obtain a linear output change for a single axis shearing force, and determined that the measurement sensitivity differs largely due to the material and shape of the frame. Therefore, if these factors are known this device can be embedded in various applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present the design and fabrication of a 1D beam steering device based on planar electro-optic thermal-plastic prisms and a collimator lens array. With the elimination of moving parts, the proposed device is able to overcome the mechanical limitations of present scanning devices, such as fatigue and low operating frequency, while maintaining a small system footprint (∼0.5mm×0.5mm). From experimental data, our prototype device is able to achieve a maximum deflection angle of 5.6° for a single stage prism design and 29.2° for a cascaded three prisms stage design. The lens array shows a 4μm collimated beam diameter. [Copyright &y& Elsevier]

Abstract: A silicon micromirror driven by piezoelectric Pb(Zr,Ti)O3 cantilever actuator has been demonstrated for 2-D scanning applications. Two different PZT actuator designs have been fabricated and characterized to investigate the effects of the dimensions and number of S-shaped PZT cantilever actuator folds on the 2-D scanning performances of the micromirror. Three modes of operation have also been investigated for both devices. Device A, which is driven by single S-shaped PZT cantilever actuator, performs better in both dc and ac laser scanning compared to device B, which is driven by double S-shaped PZT actuator. At 10Vdc, static ODA of 4.6° and 3.3° are obtained for devices A and B respectively. In the ac actuation regime, device A achieved ±9.0° at resonant frequency of 27Hz, 1Vpp while device B achieved ±7.2° at 20Hz, 1Vpp for bending mode. In torsional mode, dynamic ODA peaks of ±1.8° and ±1.2° are observed at 70Hz and 156Hz for devices A and B respectively. Lissajous scan patterns for both devices have been successfully demonstrated by superimposing two ac sinusoidal signals of different frequencies into one signal to be used to actuate the mirror. [Copyright &y& Elsevier]

Abstract: A silicon micromirror driven by piezoelectric Pb(Zr,Ti)O3 beam actuators has been demonstrated for two-dimensional (2D) scanning mirror applications. Two devices of similar design with different dimensions have been fabricated. The Si mirror is micromachined from the device layer of an SOI wafer, while the piezoelectric beam actuator contains multilayers of Pt/Ti/PZT/Pt/Ti/SiO2/Si which is deposited and released from a SOI wafer. A 1×10 PZT arrayed actuator are separately arranged in parallel on a Si beam released from the SOI substrate after the micromachining process. The 10 PZT actuators are electrically connected in series. For the large micromirror device with mirror size of 5mm×5mm, the first resonant frequency for bending mode was measured at 34Hz, while the second mode, i.e., a twist mode or torsional mode, is measured at a resonant frequency of 198Hz. For the small micromirror device with mirror size of 3mm×3mm, the bending and torsional modes were observed at 122Hz and 2.46kHz respectively. 2D raster scanning patterns were illustrated for both micromirrors. dc superimposed bias effect was also investigated for both mirror sizes. With increased dc bias, larger deflection angles were obtained. [ABSTRACT FROM AUTHOR]

Abstract: A simple numerical method based on MATLAB (The MathWorks, Inc.) is presented for studying the far-field diffraction of some optical MEMS devices with a large array and complex element geometry. The method avoids the theoretical solution by defining the working surfaces according to different apertures. Through a practical example of a grating optical modulator, the experimental tests are in good agreement with the simulation performed by using the proposed method. Then, some other optical MEMS devices with different structure configurations are also simulated. All these results reveal that the method proposed is efficient and effective, yet easy to operate. It is extremely suitable for simulating and analyzing such optical MEMS devices with planar reflective or transmissive optical working surfaces. [Copyright &y& Elsevier]

Abstract: This paper reports on the design and implementation of high efficiency, nonmetallic reflectors integrated on the sidewalls of micromachined cavities. Due to shadowing from deposition within a cavity, significant variation in the thicknesses of the dielectric thin films composing the reflectors are encountered when the layers are deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). These gradients in thickness limit the performance of the reflector at the intended design wavelength. An optimized design procedure is described to maximize the performance of the reflector at the absorption wavelength of of 795nm for use in micromachined atomic vapor cells. The reflector design is based on multiple shifted quarter wave Bragg reflectors in series, which extends the reflective bandwidth for increased robustness to film thickness gradients. The extended reflectance range maintains high reflection at the design wavelength despite greater than 70% decrease in film thickness across the reflector surface. The reflector technology is ideally suited for use in atomic MEMS vapor cell applications by achieving high reflectance while maintaining light polarization. We demonstrate less than 2dB of return loss with circular polarization ellipticity maintained to . [Copyright &y& Elsevier]

Abstract: This paper reports on a method for improving the optical efficiency of micromachined reflectors integrated in rubidium vapor cells for application in atomic MEMS sensors. A hybrid bulk micromachining and multilayer PECVD thin film process is used to form the Bragg reflectors on angled sidewalls, which redirect laser light through the vapor cell and back toward the plane of the source with reduced optical power loss. Integrated thin film Bragg reflectors are shown to improve the reflectance of the micromachined surface by almost three times, resulting in an optical return efficiency of two paired dielectric reflectors that is as much as eight times higher then uncoated silicon reflectors. Absorption of the absorption line at a wavelength of 795nm in a 1 vapor cell is demonstrated experimentally by use of two integrated thin film reflectors with a total optical return efficiency approaching 40%. [Copyright &y& Elsevier]

Abstract: We have developed a wavelength tunable fiber optic filter by using a hybrid-assembly technique of glass reflector cubes (volume 1mm3) onto a bulk-micromachined electrostatic translation stage (4mm×5mm). More than 0.6-μm-change of the Fabry-Pérot interferometer gap could be electrostatically controlled with a tuning voltage upwards of 4V with the aid of a DC bias voltage of 64V. A wide tuning range from 1479 to 1590nm was achieved with a bandwidth of 1.3–1.2nm and insertion loss of 1.59–1.76dB. [Copyright &y& Elsevier]

Abstract: The present study has employed the phase-locked loop control method to ensure the operating of MEMS actuators at their resonant frequency. In this study, the control algorism was simulated by the MATLAB. Further, the digital signal processing (DSP) technique was adopted to implement the concept of phase-locked loop control algorithm. Thus, a wide VCO lock-in dynamic range was achieved. In applications, the optical scanners fabricated using the SOI wafer and MOSBE process were respectively employed to demonstrate the present technique. The test show that the resonant frequency was tracked for various driving voltages, loop gains, and initial frequency offsets. Thus, the variation of the scanning angle resulted from the offset of the resonant frequency of the devices can be prevented. [Copyright &y& Elsevier]

Abstract: We present a miniaturized Fourier transform spectrometer implemented on a silicon optical bench platform. Both optical and opto-mechanical components of a Michelson interferometer, including a silicon beam splitter, micromirrors, MEMS actuators, and fiber U-grooves, are simultaneously fabricated by micromachining of the device layer of a silicon-on-insulator wafer. Our specialized bulk micromachining process combines the flexible definition capability of deep reactive ion etching with the good surface quality provided by anisotropic KOH wet etching. This integrated Fourier transform spectrometer has a measured spectral resolution of approximately 45nm near 1500nm wavelength. [Copyright &y& Elsevier]

Abstract: Monolithic-integrated variable optical attenuator (VOA) array devices with eight channels are realized and characterized in this study. This VOA array device is derived by DRIE micromachining process and is controlled by using electrostatic comb drive actuator. Both bright and dark types of VOA operations are presented with respect to in-line and reflection types of light attenuation configuration. This multi-channeled VOA device is potentially to be scaled up to 16 channels. Except to the state-of-the-art performance, the reported packaged devices have compact footprint of 18mm×18mm×5mm. [Copyright &y& Elsevier]

Abstract: A silicon resonant torsional micro-mirror excited by piezoelectric bimorph actuators is presented. The bimorph actuators consist of a single-crystal silicon flexible beam or membrane and a PZT thin film. The mechanical elements are etched in the 20μm thick superficial layer of a SOI substrate, thereby ensuring the flatness of the 500μm-diameter gold-coated mirror. This device achieves optical beam scanning with large angular deflection at high frequency. In air, we have measured scanning up to 19.8° at 1.8kHz, 99.1° at 10.6kHz and 40.8° at 25.4kHz. The applied driving voltage is sinusoidal with an amplitude under 42VPP and with a 6VDC bias voltage. At large oscillation amplitude, a non-linear hard-spring effect has been observed. In vacuum, a 78° optical scanning has been obtained with less than 1VPP. [Copyright &y& Elsevier]

Abstract: This paper presents a novel technological and design study of optical guided-wave MicroElectroMechanical Systems (MEMS) switch. We work on a concept of hermetic assembly in which a MEMS wafer is covered (top–down) by a crossing optical waveguide wafer. The mirrors are designed to be pulled up and inserted at waveguide intersection for N × N optical switching. Vertical micromirrors have been fabricated in SU8 photopolymer or in single crystalline silicon (on SOI substrate). The SU8 mirrors, coated with gold layer, exhibit vertical and smooth sidewalls that will be sufficient for optical use. For integration of silicon mirrors, we have developed a new simple two-step deep reactive ion etching (DRIE) pattern transfer that allow simultaneous fabrication of good quality silicon mirrors (20μm height and 2μm thickness) and of recessed mechanical platform (5μm thick). The platform has been analysed through its resonance behaviour. The strong effect of mechanical non-linearity which is observed in clamped suspension can be exploited to increase the control range of the electrostatic actuator. [Copyright &y& Elsevier]

A general theoretical model using the coupling effect between the torsion and bending is presented in this paper, which characterizes the static properties of the electrostatic torsional micromirror, especially its pull-in effect. A set of normalized equations governing the static actuation properties of the torsional micromirror based on the parallel plate capacitor model is derived to demonstrate the relationships between the parameters of static characteristics, such as torsion angle, vertical displacement, and applied voltage. Thereafter, the pull-in effect is investigated specifically to predict pull-in voltage, pull-in angle, and pull-in displacement, which highly depend on the electrode size and position, and ratio of the bending and torsion effect of the torsion beam. The ratio of the bending and torsion effect plays a key role in the pull-in phenomena. It also determines the instability mode of torsional micromirrors dominated by either the torsion or bending effect. Then, a group of torsional micromirrors is fabricated using three-layer-polysilicon micromachining process and measured using an optical projection method to verify the static actuation relation and pull-in effect respectively. The experimental data are processed and analyzed, and the theoretical analysis is in good agreement with the experimental results. [Copyright &y& Elsevier]

A high performance variable optical attenuator has been developed and its optical and mechanical models have also been established. The attenuator is fabricated by silicon surface micromachining technology and is then integrated with two single mode optical fibers that act as optical input and output. The attenuation is obtained by placing a 40 μm×40 μm gold-coated micromirror into the light path between two fibers. The attenuator has an overall layout size of 0.6 mm×1 mm (not including the fibers). It has 1.5 dB insertion loss and 45 dB attenuation range, and requires <8 V driving voltage to sweep the whole attenuation range. The specifications are promising for DWDM applications. The optical and mechanical models have been developed to fully characterize the VOA and therefore simplify the further design and optimization. [Copyright &y& Elsevier]

The microelectromechanical systems (MEMS) technology has been widely applied to develop the miniaturized external cavity tunable lasers. In this paper, two integrated MEMS tunable lasers using different configurations are presented and discussed. One uses a deep-etched circular mirror as the external converging reflector. It works in multiple longitudinal modes and has mode hopping. The other employs a deep-etched rotary blazed grating as the reflector and filter simultaneously. Single-longitudinal mode operation is achieved and mode hopping can be avoided. [Copyright &y& Elsevier]

We investigate mechanical properties of indium phosphide (InP) for optical micro-electro-mechanical systems (MEMS) applications. A material system and fabrication process for InP-based beam-type electrostatic actuators is presented. Strain gradient, intrinsic stress, Young’s modulus, and hardness are evaluated by beam profile measurements, nanoindentation, beam bending, and electrostatic testing methods. We measured an average strain gradient of δ&epsiv;0/δt=4.37×10−5 μm−1, with an average intrinsic stress of σ0=−5.4 MPa for [0 1 1] beams. The intrinsic stress results from arsenic contamination during molecular beam epitaxy and (MBE) can be minimized by careful MBE growth and through the use of stress compensating layers. Nanoindentation of (1 0 0) InP resulted in E=106.5 GPa and H=6.2 GPa, while beam bending of [0 1 1] doubly clamped beams resulted in E=80.4 GPa and σ0=−5.6 MPa. We discuss the discrepancy in Young’s modulus between the two measurements. In addition, we present a method for simultaneously measuring Young’s modulus and residual stress using beam bending. Electrostatic actuation in excess of 20 V is demonstrated without breakdown. [Copyright &y& Elsevier]

A miniaturized wavelength-tunable diode laser has been demonstrated in this paper for all optical network (AON) applications. Also, a medium feedback model has been developed to study the wavelength tuning characteristics of the micromachined tunable lasers. The miniaturized tunable laser with a size of 2 mm×1.5 mm is formed by a Fabry–Perot (FP) diode laser, a surface micromachined mirror and a butt-coupled optical fiber that can give a wavelength tuning range of 16 nm. [Copyright &y& Elsevier]