"One product, one process": This MEMS law is true for micro-optical modulators, too and thus puts a high load on every product and technology development team. On the other hand the law expresses nothing but the high versatility of the underlying usually silicon based technology. A huge variety of applications where an electromagnetic wave experiences a spatial-temporal modulation makes use of this technology: High resolution as well as ultra-compact displays, optical switches in telecommunication as well as data storage devices, spectrometers e. g. for quality control, as well as adaptive optics and pattern generation to mention only a few. The applications completely differ with regard to the requirements in almost all aspects. The most important drivers to use silicon based micro-optical modulators are high accuracy, high bandwidth and high miniaturization. A continuous further development of the technology can be reported. Novel optical, mechanical and electrical working principles are investigated to meet future requirements. After a short overview of the most typical applications of silicon based micro-optical modulators the high versatility of this technology is detailed by means of selected devices and applications. Single 1D and 2D micro mirrors with diameters of up to 4 mm e. g. for projection, imaging and spectroscopy are as well presented and discussed as micro mirror arrays comprising up to 1 million analog deflectable mirrors for image generation and phase modulation in microlithography and adaptive optics.

In recent years, many compact spectrometers for purposes such as environmental monitoring and process quality control in industrial production have been realized. However, most of them still employ spectrometer mounts with focal lengths in the range of several cm. Therefore, their size is about that of a palm which is too large for OEM-use in handily sized optical sensor equipment. Accordingly, we have developed a thumb-sized, truly miniaturized spectrometer for the spectral range 340nm to 750nm, which is particularly suited for use inside hand-held or portable color management sensor equipment. The spectrometer is using a self-imaging, aberration-corrected concave grating with very short focal length and a blazed grating profile for high diffraction efficiency. The grating is replicated onto the top of a convex glass lens using nano-imprint technology. Opposite to the concave grating, a dedicated C-MOS image sensor with an in-built on-chip slit is placed. The slit with a width of 75μm is formed into the silicon chip using MEMS technology. Due to this advanced technology, the distance between the sensor area and the slit is as small as 1mm. Based on this high level of integration, the number of optical components could be kept to a minimum and the distance between the concave grating and C-MOS image sensor is about 8.5mm only. In summary, we have realized a well-performing miniaturized spectrometer with an extremely small package size of 28mm - 17mm - 13mm and a weight of only about 9g, which is highly suited for integration into optical sensing equipment.

The Fraunhofer IPMS, in cooperation with Micronic Laser Systems, develops and fabricates micromirror arrays used as spatial light modulators (SLM) for image generation in microlithography. The SLMs used consist of 2048×512 individually addressable micromirrors of 16×16μm² and can be operated in an analog mode at a frame rate of up to 2 kHz. There are continued efforts to improve the performance of the mask writers with respect to stability and CD uniformity, which include measures to improve the SLMs used, especially with respect to the optical quality and the stability. Therefore, a new technology has been introduced which allows to use different materials for the mechanical suspension and the mirror, thus optimizing them separately. The hinges are made of a thin layer of a material with very good creep resistance, while the mirrors consist of a thick aluminium alloy with high reflectivity in DUV. Furthermore, the same inorganic material is used for the planarization of the electrodes (by means of chemical mechanical polishing) and as sacrificial layer for the actuator fabrication. Thus, at the end of the process, all sacrificial material, including that between the electrodes is removed. In this way, the charging effects caused by dielectrics between the electrodes (as seen in the previous devices) are eliminated. The first devices using the technology described above have been fabricated and tested. The first tests in a lithography machine show that considerable improvements in machine performance can be expected. The next steps are to stabilize and optimize the process.

We are developing a linear array of micromirrors designed for optical, femtosecond laser pulse shaping. It is a bulkmicromachined device, capable of retarding or diminishing certain laser frequencies in order to perform phase and amplitude modulation within a frequency band spanning the UV to the near-infrared. The design consists of a linear array of mirrors fixed on either side by springs. They feature two degrees of freedom: Out-of-plane motion for phase shifting and rotational motion for binary amplitude modulation, both realized using vertical comb drives. The first applications will include femtosecond discrimination experiments on biomolecules.

The development of a micro-opto-electro-mechanical system (MOEMS) technology employing interference effects to modulate incident light in the near-IR band (1550nm) over a wide angular range (120 degrees) is reported. Modulation is achieved by tuning a large array of Fabry-Perot cavities via the application of an electrostatic force to adjust the gap between a moveable mirror and the underlying silicon substrate. The optical design determines the layer thicknesses; however, the speed and power are determined by the geometry of the individual moveable elements. Electro-mechanical trade-offs will be presented as well as a key innovation of utilising overshoot in the device response in reduced pressure environment to reduce the drive voltage. Devices have been manufactured in a modified polysilicon surface micromachining process with anti-reflection coatings on the back of the silicon substrate. Measurements of individual mirror elements and arrays of mirrors at 1550nm show excellent uniformity across the array. This enables good response to an incident signal over a wide field of view when integrated with a silicon retroreflector in a passive optical tag. In conjunction with appropriate anti-stiction coatings, lifetimes of over 100 million cycles have been demonstrated. Key advantages of the modulator are that it is low cost being based on standard polysilicon micromachining; high speed (>100kHz) and robust due to utilising a massively parallel array of identical compact devices; low power for portable applications; and operates in transmission - allowing simple integration with a retroreflector in a passive tag for halfduplex free-space optical communications to a remote interrogator.

Today, spatial light modulators (SLMs) based on individually addressable micro-mirrors play an important role for use in DUV lithography and adaptive optics. Especially the mirror planarity and stability are important issues for these applications. Mono-crystalline silicon as mirror material offers a great possibility to combine the perfect surface with the good mechanical properties of the crystalline material. Nevertheless, the challenge is the integration of mono-crystalline silicon in a CMOS process with low temperature budget (below 450°C) and restricted material options. Thus, standard processes like epitaxial growth or re-crystallization of poly-silicon cannot be used. We will present a CMOS-compatible approach, using adhesive wafer transfer bonding with Benzocyclobutene (BCB) of a 300nm thin silicon membrane, located on a SOI-donor wafer. After the bond process, the SOI-donor wafer is grinded and spin etched to remove the handle silicon and the buried oxide layer, which results in a transfer of the mono-crystalline silicon membrane to the CMOS wafer. This technology is fully compatible for integration in a CMOS process, in order to fabricate SLMs, consisting of one million individually addressable mono-crystalline silicon micro-mirrors. The mirrors, presented here, have a size of 16×16 μm². Deflection is achieved by applying a voltage between the mirrors and the underlying electrodes of the CMOS electronics. In this paper, we will present the fabrication process as well as first investigations of the mirror properties.

Position feedback of resonant scanning micromirrors plays a key role for various applications like portable laser projection displays or scanning grating spectrometers. The SOI device layer without an additional surface implantation is used for the piezoresistive sensor design. It assures the full compatibility to microscanner technology and requires no additional technological efforts. The necessary asymmetry of the current field density is achieved by the geometrical design of the sensor and its contacting. Integrated 2D position sensors with amplitude sensitivities of 0.42mV/V° were fabricated. FEA simulation and measured data correlates well with variations of ≤ 20.4%.

This paper will investigate a novel thermally actuated micro-shutter design for micro-optical-electro-mechanical system (MOEMS) applications. The use of actuators in optical systems has improved with new developments in micro-electromechanical systems (MEMS) designs for use as components in optical systems. Thermal actuators provide a novel approach to scaling MOEMS to reduce size, weight and power of optical systems. Through the investigation of an aluminum electro-thermal actuator, we developed an in-house fabrication method which operates at less than one volt to aid in reducing the size, weight, and power of the optical system. This paper discusses several challenges and opportunities that may arise from the fabrication of thermally actuated micro-shutter designs which can help improve the actuator's uniformity, reproducibility, and reliability. In addition, we discuss the characterization of the thermal actuator micro-shutter to include mechanical, electrical and optical properties. The "switching" speed of the thermal actuator will also be assessed from a scaling perspective to determine usability.

A technology approach is presented which enables an initial permanent counter electrode deflection of planar out of plane comb drive actuators allowing quasistatic operation of an electrostatic microscanner. The device is assembled by mounting a top wafer with salient stamps onto a mirror wafer. The commonly fix in plane counter electrode parts on the mirror wafer are connected to deflectable platforms via a mechanical structure of coupled hinges. During the wafers assembly the down pressing stamps displace the platforms and result in a predefined permanent out of plane counter comb deflection.

We present a novel approach to construct three-dimensional rotary micro-mirrors, which are fundamental components to build 1×N or N×M optical switching systems. A rotary micro-mirror consists of two microparts: a rotary micro-motor and a micro-mirror. Both of the two microparts are fabricated with PolyMUMPs, a surface micromachining process. A sequential robotic microassembly process is developed to join the two microparts together to construct a threedimensional device. In order to achieve high positioning accuracy and a strong mechanical connection, the micro-mirror is joined to the micro-motor using an adhesive mechanical fastener. The mechanical fastener has self-alignment ability and provides a temporary joint between the two microparts. The adhesive bonding can create a strong permanent connection, which does not require extra supporting plates for the micro-mirror. A hybrid manipulation strategy, which includes pick-and-place and pushing-based manipulations, is utilized to manipulation the micro-mirror. The pick-andplace manipulation has the ability to globally position the micro-mirror in six degrees of freedom. The pushing-based manipulation can achieve high positioning accuracy. This microassembly approach has great flexibility and high accuracy; furthermore, it does not require extra supporting plates, which greatly simplifies the assembly process.

This paper discusses the simulation, development and potential application of Si LEDs in pre-specified complementary metal oxide semiconductors (CMOS) integrated circuit structures in the wavelength range of 450nm - 750nm. A MONTE CARLO simulation technique was developed in which the optical wave propagation phenomena as relevant in CMOS structures were continuously updated as the optical ray progresses through the structure. Refractive index of the material, layers thickness and structure curvatures were all incorporated as ray propagation parameters. By using a multi-ray simulation approach, the overall propagation phenomena wrt refraction, reflection, scattering, and intensities could be evaluated in globular context in any complex CMOS integrated circuit structure in a progressive way. MATLAB software was used as a mathematical capable and programmable language to develop the dedicated software evaluation tool. Subsequently, some first iteration, conceptual, applications of MOEMS structures are demonstrated as implemented in Si CMOS integrated circuitry, utilizing Si InAva LEDs and silicon detectors.

In this paper we present basic designs, operation concepts and some application examples of a novel microspectrometer for the spectral range of 3-5μm, which is based on a pyroelectric detector with an integrated micromachined Fabry-Perot filter (FPF). We discuss the influence of different optical setups on the spectral resolution and the signal-to-noise ratio of the microspectrometer. Two basic operation modes, step scan mode and continuous sweep mode are demonstrated. Such a device has a large potential in the field of infrared absorption spectroscopy, particularly if multicomponent mixtures have to be analyzed.

Quantitative determination of gas compositions are important for operation and control of different industrial processes, e.g. in thermo process line operations. Changing gas conditions are affecting such processes significantly. Thus direct measurement of these gases enables adjustment of variable gas composition very fast and precisely and can improve process and product quality. Traditional analyzers, designed primarily for laboratory use, are too large, too delicate, and too costly to deploy. Cost efficient devices can however measure individual parameters (e.g. IR absorption at a specific wavelength, heat conductivity etc.) of gases and compositions can be derived directly by calculating it online. To bridge the gap between these traditional and expensive gas analyzers and favorable, cost-effective gas measurements, we have developed a low cost MEMS-based gas analyzer system. By using near infrared spectroscopy, individual components of the mixed gas can be determined quantitatively. Also disadvantages of existing cost-effective systems like selectivity, sensitivity and measurement time is avoided. Requirements of a suitable system are precise determination and adoption of the overall optical system as well as a high wavelength stability, which represents one important condition for exact chemometric evaluation. Likewise a robust and exact spectral evaluation procedure is important. Other challenges are MEMS design and packaging as well as optimization of insensitivity against vibrations and thermal stress. In this paper, the application of MEMS analyzer in gas measuring is described and above mentioned challenges will be discussed. To demonstrate the performance of the whole system, measurement results of gas mixtures will be shown.

In this work we describe the fabrication and characterization of MOEMS-based integrated optical switches with improved ON/OFF performance. These structures consist of silicon oxynitride-based optical waveguides, through which a light beam of 633-nm can be conducted, and mobile thermo-electro actuated cantilevers, which form part of the waveguide and can work as ON-OFF switches for the laser. These switches allow the laser light to pass or block the laser light when activated electrically. The cantilevers are fabricated by freeing regions of the waveguide, which is done by front side micromachining the silicon wafer used as substrate. Also, they are actuated electrically through the heating of a metallic resistance positioned in the device, where the applied current heats the cantilevers and, due to the difference in thermal expansion coefficients of the constituent materials, it is possible to produce a controlled motion proportional to the heating current. Therefore, the switches can be electrically polarized in on/off cycles allowing or blocking the light through the waveguide, similar to logic "1's" and "0's".

We present a novel micro-interferometer implemented using arrays of single-mode planar optical waveguides. The spatial heterodyne waveguide spectrometer offers high resolution and increased optical throughput (etendue) and is compatible with a microsatellite platform. A stationary Fourier technique is employed to reconstruct the input spectrum from the array of outputs. Calibration mitigates waveguide fabrication errors and input illumination non-uniformities and can be readily implemented in the spectral retrieval algorithm. Signal to noise performance is estimated for a remote sensing application using a classical telescope front end with comparison to classical techniques.

Programmable microshutter arrays were designed to improve the attainable signal to noise ratio (SNR) of a miniature dispersive spectrometer developed for space applications. Integration of a microshutter array to this instrument provides advantages such as the addition of a binary coded optical input operation mode for the miniature spectrometer which results in SNR benefits without spectral resolution loss. These arrays were successfully fabricated using surface micromachining technology. Each microshutter is basically an electrostatic zipping actuator having a curved shape. Applying critical voltage to one microshutter pulls the actuator down to the substrate and closes the associated slit. Opening of the microslits relies on the restoring force generated within the actuated zippers. High light transmission is obtained with the actuator in the open position and excellent light blocking is observed when the shutter is closed. The pull-in voltage to close the microslits was about 110 V and the response times to close and open the microslits were about 2 ms and 7 ms, respectively. Selected array dies were mounted in modified off-the-shelf ceramic packages and electrically connected to package pins. The packages were hermetically sealed with AR coated sapphire windows. This last packaging step was performed in a dry nitrogen controlled atmosphere.

Programmable Micro-Diffraction Gratings (PMDG) are a new type of MOEMS, opening new observational capabilities in future astronomical instrumentation. Programmable gratings are based on a serial of parallel ribbons able to move out of the plane. By using electrostatic force, ribbons are actuated and a grating could be formed. A few ribbons are efficient enough to diffract the light; then, locally, this grating acts as a ON-OFF switch. If the spectrum is focused on this type of device, by setting ON and OFF a selected number of "wavelengths", the spectral response of the spectrograph is programmable. Programmable gratings permit the design of programmable spectrometers, useful in space mission, like ESA Darwin mission. This mission will search, detect and characterize exo-planets, using high-contrast nulling interferometry, coupled with spectroscopic observation. We propose a new observational concept for Darwin using a programmable spectrometer. By tailoring the spectral response, sensitivity as well as signal to noise ratio of the instrument will be increased. A demonstrator breadboard with a PMDG device has been designed and built. This demonstrator, including adjustable sources (location, spectral type, brightness), permits the tailoring of spectral patterns by the PMDG component. Two parallel spectral and imaging channels are used for the optical analysis of the tailored signals. Typical exo-planet spectra have been generated and set by the PMDG. Simulated signatures of exo-planets with life forms are clearly revealed and characterized on the breadboard, demonstrating successfully our concept. Several new observational modes using PMDG devices in future astronomical instrumentation is then foreseen.

INO has established a VOx-based uncooled microbolometer detector technology and an expertise in the development of custom detectors and focal plane arrays. Thanks to their low power consumption and broadband sensitivity, uncooled microbolometer detectors are finding an increased number of applications in the field of space-based thermal remote sensing. A mission requirement study has identified at least seven applications with a need for data in the MWIR (3-8 μm), LWIR (8-15 μm) and or FIR (15-100 μm) wavelength bands. The requirement study points to the need for two main classes of uncooled thermal detectors, the first requiring small and fast detectors for MWIR and LWIR imaging with small ground sampling distance, and the second requiring larger detectors with sensitivity out to the FIR. In this paper, the simulation, design, microfabrication and radiometric testing of detectors for these two classes of requirements will be presented. The performance of the experimental detectors closely approach the mission requirements and show the potential of microbolometer technology to fulfill the requirements of future space based thermal imaging missions.

Next-generation infra-red astronomical instrumentation for space and ground-based telescopes requires MOEMS-based programmable slit masks for multi-object spectroscopy (MOS) which has to work in cryogenic environment. A first prototype of micromirror arrays (MMA) of 5×5 single-crystal silicon micromirrors was successfully designed, fabricated and tested. 100×200 μm² micromirrors can be tilted by electrostatic actuation yielding 20° mechanical tiltangle. The MMA were successfully actuated before, during and after cryogenic cooling, below 100 K. A MMA is composed of two different chips fabricated on silicon on insulator (SOI) wafers: the mirror chip and the electrode chip. The array was obtained by assembling these two chips. For the assembly step of large array (100×200 micromirrors) we needed high precision alignment as well as the suppression of manual handling. Therefore we developed a technique of assembly for such devices and we designed and fabricated a dedicated XYZ tip/tilt stage. This stage allows aligning the electrodes towards the micromirrors with a micrometer precision. Large MMA of 100×200 micromirrors, measuring 22 mm×25 mm, for large field of view were microfabricated and assembled using the above setup. No additional deformations were observed due to the assembly step. The peak to valley (PTV) deformation of the micromirrors was found to be 14 nm PTV. The first actuation tests were carried out.

This paper reports on the design and analysis of two miniature far infrared radiometers to be distributed on low Earth orbit by means of two formation flying nanosatellites. These instruments are intended for the coregistration of the Earth's limb profiles in the emission bands of CO₂ and H₂O, 14-16 um and 24.3-26.1 um. Their purposes are to produce a new database of navigational horizon characteristics and to support the investigations of the atmospheric outgoing radiation in the far infrared spectrum. Miniaturization technologies have been used to ensure compliances of the radiometer with an average power consumption of 400 mW, a mass of 500 g, and an envelope of 10⁵×10⁵×100 mm³. The optics of the radiometer was designed to achieve adequate throughput for a vertical resolution of 2.8 km of the limb. It was shown that good optical performance could be obtained in the far infrared using small lens assemblies. The sensor consists of a linear array of 256×2 custom designed microbolometers whose absorptance characteristics were tailored to the working spectral band. Computed data on the sensor performance confirmed its suitability for the acquisition of limb targets with typical temperature profile of 220-300 K at the above spatial resolution. The data acquisition is to be performed in sequences of measurement of 14 s with one orbital period between sequences until the latitude coverage is completed. This duty cycle was found compatible with the downlink and storage capacity of the nanosatellite.

MEMS sensors, actuators, and sub-systems can enable an important reduction in the size and mass of spacecrafts, first by replacing larger and heavier components, then by replacing entire subsystems, and finally by enabling the microfabrication of highly integrated picosats. Very small satellites (1 to 100 kg) stand to benefit the most from MEMS technologies. These small satellites are typically used for science or technology demonstration missions, with higher risk tolerance than multi-ton telecommunication satellites. While MEMS are playing a growing role on Earth in safety-critical applications, in the harsh and remote environment of space, reliability is still the crucial issue, and the absence of an accepted qualification methodology is holding back MEMS from wider use. An overview is given of the range of MEMS applications in space. An effective way to prove that MEMS can operate reliably in space is to use them in space: we illustrate how Cubesats (1 kg, 1 liter, cubic satellites in a standardized format to reduce launch costs) can serve as low-cost vectors for MEMS technology demonstration in space. The Cubesat SwissCube developed in Switzerland is used as one example of a rapid way to fly new microtechnologies, and also as an example of a spacecraft whose performance is only possible thanks to MEMS.

Optical intra-communication links are investigated by several currently operational qualification missions. Compared with RF communication systems, the optical domain obtains a wider bandwidth, enables miniaturized spacecraft and reduced power consumption. In this project, a microtransmitter is designed and manufactured for formation flying spacecraft with transmission rates of 1 Gbit/s. Simulations in Matlab and Simulink show that a BER of 10-9 can be achieved with aperture sizes of 1 cm and a transmitter output peak power of 12 mW for a distance of 10 km. The results show that the performance of the communication link decreases due to mechanical vibrations in the spacecraft together with a narrow laser beam. A dual-axis microactuator designed as a deflectable mirror has been developed for the laser beam steering where the fabrication is based on a double-sided, bulk micromachining process. The mirror actuates by joints consisting of v-grooves filled with SU-8 polymer. The deflection is controlled by integrated resistive heaters in the joints causing the polymer to expand thermally. Results show that the mirror actuates 20-30° in the temperature interval 25-250°C. Flat Fresnel lenses made of Pyrex 7740 are used to collimate the laser beam. These lenses are simulated in the Comsol software and optimized for a 670 nm red VCSEL. The lenses are manufactured using lithography and reactive ion etching. All tests are made in a normal laboratory environment, but the effect of the space environment is discussed.

Scanning photon microscopes (SPM), also known as laser scanning microscopes (LSM), are provided by several commercial manufacturers, e.g. [1-4]. Technically they illuminate a sample with light from a laser light source which is deflected in two directions. The reflected light is detected through a photo sensitive detector. From the position of the laser spot and the detector signal the image of the sample is calculated. Applying a second detector behind an aperture stop, bright and dark field images of the sample can be taken. Furthermore processes like fluorescence or RAMAN can be initiated. If the sample or a kind of marker added to the sample creates a fluorescence or RAMAN signal from a selected wavelength, the signal can be separated through an additional filter in front of the detector or a spectrometer respectively. Doing this, interesting applications in the field of non destructive testing arise. State of the art systems offer an optical resolution of 0.2...0.5 μm but they are bulky and expensive. In our new approach we aim at a lower resolution of 5 ... 10 μm applying a small system size and less effort for installation and usage. This aim can be reached using a 2d MEMS scanner mirror for the laser light deflection. The test setup realized has a size of 20cm x 10cm x 5cm. A red semiconductor laser with 30mW has been used for evaluation. An image area of 10mm x 10mm has been selected. 1000×1000 pixels were taken in accordance with 10μm optical resolution.

In this study we developed a liquid-filled varifocal lens operated by electroactive polymer actuators. A silicon wafer was structured with micromachining processes to have four microfluidic chambers and a circular hole working as an aperture. The structured silicon wafer (opaque frame) was bonded to a glass wafer (transparent frame), and thus microfluidic channels were formed between them. Top surface of the main frame was covered with a transparent elastomer membrane, and the internal volume confined by the membrane and the two frames was filled with optical fluid. In order to operate this varifocal lens system, multilayered P(VDF-TrFE-CFE) [poly(vinylidene fluoride-trifluoroethylene-clorofluoroethylene)] polymer actuators were also developed, which show relaxor ferroelectric behavior, and thus produce large electrostrictive strain. When an electric field is applied, the multilayered P(VDF-TrFE-CFE) polymer actuators push the optical fluid so that the elastomer membrane together with the internal fluid changes their shape, which alters the light path of the varifocal lens. The original shape of the elastomer membrane is restored by the elastic recovery of the P(VDF-TrFE-CFE) actuators when an applied electric field is removed. We observed that with the applied voltage of 40 V the varifocal lens changes the optical power of more than 30 diopters within 20 ms. Optical analysis showed that the deformation shape of the optical membrane can be successfully used to design phone camera modules with auto-focus function.

This paper describes a method to extend the range of motion of a deformable, continuous membrane mirror beyond the limit of open-loop electrostatic instability through the use of a feedback control scheme. The feedback scheme is based on capacitive sensing of the mirror. The sensing is achieved by coupling the actuation electrodes to a ring oscillator. We use a differential technique, where the frequency of the coupled oscillator is compared to a reference ring oscillator. Analysis of the system using a simplified parallel-plate model shows that the range of stable deflection depends on the dynamics of the device and control circuitry, and suggests that stable full-gap displacement can be achieved under certain conditions. Experimental results are provided, showing stable closed-loop deflection of our silicon nitride test device to 61% of the air gap, consistent with the predictions of our model.

For miniature laser projection displays the laser beam is swept very fast back and forth with a MEMS mirror. This paper presents an innovative design for such a MEMS mirror. Both the dynamical behavior and manufacturability have been improved. We designed a process based upon industrially proven process steps to accurately control critical parameters and fabricated a mirror consisting of: cantilever beams, out-of-plane support beams and a rhombus shaped enforcement structure. Measurements show a well defined resonant mode of operation at 23.5 kHz while suffering from only little parasitic resonance modes. This mirror can now be mass-produced at low costs.

Damping is a critical factor affecting the dynamics of resonant scanning micromirrors and the design of their actuator systems. For any new micromirror design, modeling the damping to sufficient accuracy to predict the performance can save much effort in testing and redesign. To address this challenge, a simple formula for the air drag on scanning micromirrors is postulated that contains a drag coefficient, which is treated as a function of the Reynolds number that is fit to experimental measurements of the damping of two different MEMS scanning mirrors. A formula is found that describes the drag coefficients for both scanning mirrors for a range of their Reynolds numbers.

Diffractive spatial optical modulators (SOM) with fine pitch pixel array were introduced for the mobile applications of laser projection display which requires the small volume, low power consumption and high optical efficiency. Micromechanical designs of piezoelectric (PZT) actuator and mirror ribbon structure were optimized for small volume, but keeping the same level of the other performance. Even though the same design rule and fabrication equipment were used for 10 um pitch SOM and 16 um pitch SOM, the optical efficiency of the fine pitch SOM was 78 % for the 0th order diffraction and is better than that of 16 um pitch SOM (73%). The full on/off contrast ratio has no difference between 10 um pitch and 16 um pitch SOM. All the optical characteristics coincide well with the theoretical estimations. High displacement of 500nm, which is enough to modulate the three Red, Green and Blue colors were achieved by the control of the thicknesses and stresses of constituent structural layers. It was found that the stress of Pt/PZT/Pt actuating layer was the main parameter affecting the initial gap height of the ribbon and also its displacement. For improving the optical properties of the SOM devices, the required ribbon-flatness could be achieved by applying a stress gradient on the SiN layer to compensate for the stress unbalance between Al mirror and SiN supprting layer. The temperature sensitive characteristics of the SOM device, which degrades the image quality, could be minimized by a mechanical compensation method using a thermal expansion effect of Si substrates. This concept could be applied in most of the bridge type MEMS structure. The most critical parameter which limit the SOM device lifetime was found to be the ribbon displacement degradation. By using a temperature accelerating lifetime measurement method based on the displacement degradation the estimated lifetime was more than 4,000 hrs and is of acceptable level in the mobile application. In short, the developed fine pitch SOM device, for making small volume of optical module, has sufficient response time and ribbon displacement for modulating the red, blue and green colors with one SOM chip and is suitable for high quality embedded laser projection displays. Optical module with VGA is successfully demonstrated for its potential applications in mobile laser projection display such as a embed projection cellular phone.

(This paper was presented in Session 4, Waveguide Devices, during the MEMS and Miniaturized Systems VIII conference.) This work shows improvements on previous results related to the integration of optical waveguides and simple light sources. These previous results showed the possibility of coupling the light emitted from an incandescent chromium filament embedded in a self-supported region of silicon oxynitride (SiO_xN_y) film with a SiO_xN_y waveguide. This specific work aims to increase optical power coupled to the waveguide through the investigation of the geometry of the microlamp. Here, the length of the incandescent light is analyzed. The waveguide are fabricated on a (100) silicon substrate using silicon oxynitride deposited by PECVD as the core and cladding layers. Bulk micromachining of the silicon substrate in KOH solution is used to free from the substrate the embedded filament, reducing the thermal dissipation of that region, allowing the filament to heat up to incandescent temperatures. A microannealing process of a PECVD-obtained amorphous hydrogenated silicon carbide (a-SiC:H) deposited over the microlamp allows the correct coupling of the light.