The Telecom sector has driven until 2000 the development of micro-mirrors with subsystems like optical cross-connects and add/drop multiplexers for all-optical networks. Following the collapse of the telecom equipment market, much attention has been given to emerging applications in consumer electronics, IT, industry, and biomedical. WTC will give an overview on existing and emerging markets of micro-mirrors outside telecom. The various micro-mirror techniques and their respective applications from high value niches to mass markets will be presented. The supply chain will be analysed and a roadmap of implementation of micro-mirrors will be proposed.
It is important to know mechanical properties of micro structures fabricated as a micro machine component by micro-stereolithgraphy(mSL). We developed new measurement equipment and measured Young's modules of micro cantilevers fabricated by mSL. Sample micro cantilevers were formed by changing irradiation laser power of mSL system and postcure processing time. We put load on the sample cantilever, then measured the relation between load and deflection of the cantilever. The young's modules of samples were calculated from the gradient of measured Load-Defection relation and the formula of strength of material. As the result, the young's module of cantilever made by mSL is depended on irradiation laser power. And the value increases by postcure which makes progress of un-cured part polymerization in the cantilever. Although the increased values are also depended on irradiate laser power.
We report a 1xN rotary optical switching mirror actuated by an electrostatic comb-driver for the optical networking. A variety of MEMS optical switching mirrors have been recently proposed. Some of these devices utilize surface micromachined films as reflection micromirrors and result in optical degradation. Some of these devices fabricated by bulk micromachining highly rely on delicate assembly for the micromirrors to the top of the actuators. In this paper, we focus on developing a rotary optical switching micromirror with no need of delicate assembly. The rotary actuator and the switching micromirror are both fabricated by deep RIE in our design. We use the Spin-On-Glass (SOG), which is used as the intermediated layer in the low temperature boning, to fabricate a rotary MEMS optical switching mirror with self-assembly. We successfully assemble the micromirror on top of the rotor stage of the rotary actuator. Experimental results show that our rotary vertical micromirror rotates about 1.5° under 150 volts. The first vibration mode of this rotary switching MEMS mirror is a rotary mode and appears around 3.4 kHz, which is measured via a Polytec laser doppler vibrometer.
We propose a micromachined 2x2 optical switch with variable optical attenuation. The proposed optical switch features expandability and integration utilizing four 45° micromirrors driven by four electrostatic comb actuators. These four micromirrors can move independently to reflect and/or partially block the optical signal. In order to reduce the insertion loss caused by long optical path length, the optical module employed anti-reflection coated lensed fibers. Two pairs of optical fibers were aligned in each single trench at both sides for cost-effective packaging. The device was fabricated using SOI (Silicon-On-Insulator) process with one photo-mask, and its experimental IL (Insertion Loss) and attenuation range were less than 1.53 dB and over 60 dB, respectively. Also the PDL (Polarization Dependent Loss) was less than 0.25 dB in the range of 30 dB.
This paper describes the design of a novel electrostatically actuated optical attenuator that uses the electrostatic actuation of a cylindrical waveguide. The optical MEMS device consists of an electrostatically actuated waveguide positioned in a V-groove and overhanging at the end to act as a cantilever. The optical fiber waveguide can be sputtered with a thin film of gold that acts as a good electrode. The electrostatic force between the electrodes actuates the input fiber under the application of a voltage and causes misalignment between the input and output fibers and thereby attenuates the amount of light transmitted to the output fiber. Electrostatic modeling of the system presented in this paper is simple and sufficiently accurate. The proposed analytical model takes into consideration the geometry of the cylindrical electrodes. The geometrical relationship of the cantilever beam to the range of the biasing voltage is also discussed. The paper presents the variation of deflection of the waveguide and the variation of power loss with respect to the applied voltages. The obtained results clearly demonstrate the efficient use of the proposed method and modeling approach.
A simple and novel way of attenuation is presented to investigate the feasibility of affecting the coupling cylindrical waveguides. Piezoelectric polymers such as PVDF (Poly Vinyledene Fluoride) are very attractive for many applications as they exhibit good piezoelectric and pyroelectric responses and low acoustic impedance. Moreover, their properties can be tailored according to the desired requirements. PVDF actuators are proposed because of their low cost and simple process of fabrication. In this paper, cylindrical waveguides are actuated by means of a piezoelectric actuator using PVDF (Poly Vinylidene Fluoride) material. The presented results include the design and analysis of a new cylindrical waveguide based attenuator with PVDF actuation. The presented results include the influence of PVDF (Poly Vinylidene Fluoride) actuation on the optical coupling efficiency. The paper also includes the parametric study on the variation of the geometry of PVDF film with respect to the coupling efficiency. The results also include the variation of deflection and power loss through cylindrical waveguides for various applied voltages. The paper demonstrates a simple and novel application of PVDF film for optical microsystem.
There is a great need for techniques that will permit the evaluation of MEMS devices, in all stages of manufacturing, with respect to material and micromechanical properties. In this contribution we propose a new approach, based on the integrated optical read-out using a Mach-Zehnder interferometer, monolithically integrated into the PZT actuated membrane and electrostatically actuated torsional micromirror. The application of membrane-type structure is in the area of pressure sensors. The monolithically integrated MZI on movable torsional mirror seems to be an easy solution for monitoring mechanical performances during lifetime of micromirror.
Micro-Opto-Electro-Mechanical Systems (MOEMS) have found a variety of applications in fields such as telecommunications, spectroscopy and display technology. MOEMS-based optical switching is currently under investigation for the increased flexibility that such devices provide for reconfiguration of the I/O network for inter-chip communication applications. This potential not only adds an additional degree of freedom for adjustment of transmitter/receiver links but also allows for fine alignment of individual channels in the network link. Further, this use of diffractive arrays for specific applications combines beam steering/adjustment capabilities with the inherent wavelength dependence of the diffractive approach for channel separation and de-multiplexing. Research and development has been concentrated on the progression from single MOEMS components to parallel arrays integrated with optical source arrays for a successful feasibility demonstration. Successful development of such an approach will have a major impact of the next generation communication protocols.
This paper will focus on the current status of the MOEMS research program for Free Space Optical inter-chip communication at the College of NanoScale Science and Engineering, University at Albany-SUNY (CNSE). New versions of diffractive arrays stemming from the basic MEMS Compound Grating (MCG; patent #5,999,319) have been produced through various fabrication methods including the MUMPs process1. Most MEMS components relying on electrostatic actuation tend to require high actuation voltages (>20V) compared to the typical 5V levels prevalent in conventional integrated circuits. The specific goal is to yield improved performance while minimizing the power consumption of the components. Structural modifications through the variation in the ruling/electrode spacing distance and array wiring layout through individually addressable gratings have been studied to understand effects on the actuation voltage and cross talk, respectively. A detailed overview of the optical and mechanical properties will be included. Modeling results along with the mechanical and optical testing results have been detailed and compared with previously obtained results. Future work focuses on alternate material sets for a reduction in operational voltage, improvements in optical efficiency and technology demonstrators for verification of massively parallel I/O performance.
Micro scanning mirrors are quite versatile MEMS devices for the deflection of a laser beam or a shaped beam from another light source. The most exciting application is certainly in laser-scanned displays. Laser television, home cinema and data projectors will display the most brilliant colors exceeding even plasma, OLED and CRT. Devices for front and rear projection will have advantages in size, weight and price. These advantages will be even more important in near-eye virtual displays like head-mounted displays or viewfinders in digital cameras and potentially in UMTS handsets.
Optical pattern generation by scanning a modulated beam over an area can be used also in a number of other applications: laser printers, direct writing of photo resist for printed circuit boards or laser marking and with higher laser power laser ablation or material processing.
Scanning a continuous laser beam over a printed pattern and analyzing the scattered reflection is the principle of barcode reading in 1D and 2D. This principle works also for identification of signatures, coins, bank notes, vehicles and other objects. With a focused white-light or RGB beam even full color imaging with high resolution is possible from an amazingly small device. The form factor is also very interesting for the application in endoscopes.
Further applications are light curtains for intrusion control and the generation of arbitrary line patterns for triangulation. Scanning a measurement beam extends point measurements to 1D or 2D scans. Automotive LIDAR (laser RADAR) or scanning confocal microscopy are just two examples. Last but not least there is the field of beam steering. E.g. for all-optical fiber switches or positioning of read-/write heads in optical storage devices. The variety of possible applications also brings a variety of specifications. This publication discusses various applications and their requirements.
Infrared analysis is a well-established tool for measuring composition and purity of various materials in industrial-, medical- and environmental applications. Traditional spectrometers, for example Fourier Transform Infrared (FTIR) Instruments are mainly designed for laboratory use and are generally, too large, heavy, costly and delicate to handle for remote applications. With important advances in the miniaturization, ruggedness and cost efficiency we have designed and created a new type of a micromirror spectrometer that can operate in harsh temperature and vibrating environments This device is ideally suited for environmental monitoring, chemical and biological applications as well as detection of biological warfare agents and sensing in important security locations
In order to realize such compact, portable and field-deployable spectrometers we have applied MOEMS technology. Thus our novel dual detector micro mirror system is composed of a scanning micro mirror combined with a diffraction grating and other essential optical components in order to miniaturize the basic modular set-up. Especially it periodically disperses polychromatic radiation into its spectral components, which are measured by a combination of a visible (VIS) and near infrared (NIR) single element detector. By means of integrated preamplifiers high-precise measurements over a wide dynamic wavelength range are possible. In addition the spectrometer, including the radiation source, detectors and electronics can be coupled to a minimum-volume liquid or gas-flow cell. Furthermore a SMA connector as a fiber optical input allows easy attachment of fiber based probes. By utilizing rapid prototyping techniques, where all components are directly integrated, the micro mirror spectrometer is manufactured for the 700-1700 nm spectral range.
In this work the advanced optical design and integration of the electronic interface will be reviewed. Furthermore we will demonstrate the performance of the system and present characteristic measurement results. Finally advanced packaging issues and test results of the device will be discussed.
Micro-opto-electro-mechanical systems (MOEMS) typically require optical surfaces with high flatness and low roughness to be combined with high quality mechanical parts and low power, high force microactuators. In the past, attention has concentrated overwhelmingly on polysilicon surface micromachining, which allows an extremely flexible approach to the design of complex optical systems. However, polysilicon components typically suffer from poor surface flatness and high roughness, and lack the strength and rigidity to support and manipulate macroscopic optical components, which often have weights in the milligram range. Bonded silicon-on-insulator (BSOI) material provides an excellent alternative, allowing high optical quality to be combined with high mechanical strength. This paper will review a number of different approaches to BSOI MEMS, including deep reactive ion etching (for in-plane devices), double-sided processing (for through-wafer devices) and surface tension self-assembly (for 3D MOEMS). Applications ranging from variable optical attenuators to tunable laser systems will be described. Methods of mounting, aligning and fixing hybrid-integrated components will also be considered, together with appropriate high-force micro-actuators.
Our recent progress on the miniature bio-chemical analytical system is introduced in this paper. Experiments have been carried out to test the performance of our system. During these experiments, the absorption spectrums of different materials were obtained, which included NaNO2, protein, blood, Fe2+ ion and several medicine solutions. Comparison experiments were also adopted to compare the performance of the system with that of some exiting BCAS, such as the Shimaudzu UV-240 spectrometer and Australia GBC spectrometer. The results show that the experimental datum is compatible. Quantitative experiment is carried out by using the Fe2+ ion solutions with different concentration and the working curve of such ion is obtained which show that it is compatible with the Low of Lambert-Beer. All these show that the system can meet the requirement of practical use. Our research is one of the explorations to make the conventional analytical system portable by using the technology of MOEMS.
Unlike electronic devices, where for analysis only electrical parameters need to be tested, Micro and Nano Technology (MNT) devices require precise measurement of multi domain parameters for characterization. Furthermore, the sensitivities require other or improved technologies. For instance, for testing a MEMS device, a stable supply of physical energy is required and must be transferred to the product in a reproducible way. Also a sensitive measuring technology is necessary to detect the electrical signal produced as a response to the physical energy on the device. Sometimes interactions between input and output make measuring difficult. A third point is that handling of the devices is difficult due to their non-standard sizes and small dimension. Also MST including MEMS and MOEMS devices require new types of reliability testing addressing stiction, and other specific failure modes. Thus, the testing of MNT devices is much more complex than standard electronic components. Currently standardized tests are often not available, neither is there sufficient background information available about MNT testing, as most of the companies regard testing experience, and especially product testing, as company confidential information. However, the MNT industry can utilise existing testing equipment. This article addresses the available equipment for MNT testing in relation to the industry needs. Examples of the instruments discussed include optical profilers for dynamic measurement of MOEMS/MEMS devices, such as gyros and accelerometers, and wafer testers for optical products.
This paper presents high-resolution control of torsional electrostatic micromirrors beyond their inherent pull-in instability using robust sliding-mode control (SMC). The objectives of this paper are two-fold - firstly, to demonstrate the applicability of SMC for MEMS devices; secondly - to present a modified SMC algorithm that yields improved control accuracy. SMC enables compact realization of a robust controller tolerant of device characteristic variations and nonlinearities. Robustness of the control loop is demonstrated through extensive simulations and measurements on MEMS with a wide range in their characteristics. Control of two-axis gimbaled micromirrors beyond their pull-in instability with overall 10-bit pointing accuracy is confirmed experimentally. In addition, this paper presents an analysis of the sources of errors in discrete-time implementation of the control algorithm. To minimize these errors, we present an adaptive version of the SMC algorithm that yields substantial performance improvement without considerably increasing implementation complexity.
The design and fabrication of electrostatic actuators for micro-mirror systems in telecommunications, scanning, and display applications has advanced enormously over the past few years. These advances were largely stimulated by the telecommunication bubble of the early 2000's. Early micro-mirror systems utilized parallel plate actuation schemes that suffered from inherent pull-in stabilities and required high operation voltages of several hundred Volts. The continuous need for micro-mirror systems that deflect at high angles with low voltage drives (< 50 V) have resulted in a number of solutions. Innovative techniques such as the utilization of parametric analog torque amplification, raised side electrodes that suppress pull-in and magnify torque, high energy density vertical comb drives, and mechanical motion multiplication schemes all contribute toward these goals. This paper reviews recent progress in this area and discusses current technical challenges.
Three-dimensional imaging is achieved by optical coherence tomography (OCT) integrated with a two-axis MEMS scanner to enable noninvasive volume imaging of biological tissues. The longitudinal scan is obtained by optical coherence interferometry. The transverse scan is obtained by tilting the two-axis MEMS mirror to scan the optical beam across the target. High-resolution OCT imaging has enabled in vivo observation of tissue architectural layers and differentiation of normal from tumor lesions within the human gastrointestinal tract. MEMS scanner based catheters with distal beam scanning can image with higher speed, precision, and repeatability than conventional linear scanning catheters. In this work, a 1-mm diameter MEMS scanning mirror with collimator and focusing optics is integrated into a compact 5-mm diameter package that is compatible with limited space in the endoscope. A large fill factor mirror provides high aperture over large scan angle and frequencies of hundreds of Hz in both axes. Using a broadband femtosecond laser light source, high axial image resolution of ~5 um is achieved at 1.06 um wavelength. Transverse resolution of ~ 12-um is demonstrated for cross-sectional image with the endoscope.
Next generation giant telescopes as well as next generation instrumentation for 10m-class telescopes relies on the availability of highly performing adaptive optical systems, for studying new fields like circumstellar disks and extrasolar planets. These systems require deformable mirrors with very challenging parameters, including number of actuators up to 250 000 and inter-actuator spacing around 500μm. MOEMS-based devices are promising for future deformable mirrors. However, only limited strokes for large driving voltages have been demonstrated. In order to overcome these limitations, we are currently developing a micro-deformable mirror based on an array of electrostatic actuators with attachment posts to a continuous mirror on top. The originality of our approach lies in the elaboration of a sacrificial layer and of a structural layer made of polymer materials, using low-temperature process. This process allows the realization of high optical quality mirrors on top of an actuator array made with various techniques. We have developed the first polymer piston-motion actuator in order to reach high strokes for low driving voltages: a 10μm thick mobile plate with four springs attached to the substrate, and with an air gap of 10μm exhibits a piston motion of 2μm for 30V. Preliminary comparison with FEM models show very good agreement and design of a complete polymer-based MDM looks possible.
Membrane deformable mirror devices consist of a single large membrane that is suspended above an array of actuating electrodes. A transparent electrode is incorporated into the membrane mirror device in the optical path in an effort to provide significantly greater control of the membrane, and hence improved performance in an adaptive optics system. The devices presented here were fabricated from 1 mm thickness SOI; devices were bonded to electrode arrays with 1024 electrodes, packaged in ceramic pin grid arrays and driven by off chip D/A electronics. The transparent electrodes consist of glass that is ITO coated for electrical conductivity and visible light transmission. An electrode is inserted into a recessed cavity of each membrane chip, and is positioned 70 mm above the membrane. With 2x2 binned electrodes, the device demonstrates 10 mm deflection toward the electrode array at 40 V. Large deflection at low voltage is obtained because of the low intrinsic stress of the silicon membrane. These data also demonstrate modest deflection toward the transparent electrode, which may be improved with better alignment of the transparent electrode with the underlying membrane and electrode array in future devices.