This PDF file contains the front matter associated with SPIE Proceedings Volume 7930, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Optical MEMS technologies originally developed for the WDM systems have found a wide range of lateral spreading applications. For instance, we have constructed a novel power-over-fiber type OCT endoscope by using two different wavelengths for powering an electrostatic MEMS scanner and for optical probing; this work is on the extension of a MEMS variable optical attenuator. Another example is a Fabry-Perot interferometer for wavelength filtering that has been redirected to a new use of a tunable color pixel developed in a plastic sheet of large area. We look into the diverging potential of MEMS in micro optics.

A miniaturized MEMS scanning microscope is presented, which enables endoscopic imaging for medical, biological and technical purposes. It consists of an optical head of only 8 mm diameter that is coupled via optical fibers and wires to a distant unit containing optics and electronics for microscope control and data processing. A PC or notebook is completing the system, acting as user interface, image display and storage. The microscope uses a focused flying laser spot allowing a resolution of about 15 μm within the focus plane. This enables new endoscopic applications as in-vivo investigation of cancer-suspicious tissues in medicine.

We are developing MEMS deformable mirrors for focus control in miniature optical systems, including endoscopic microscopes and small form-factor camera lenses. This paper describes a new process to create mirrors made from the photoset polymer SU-8. The SU-8 also serves as the adhesive layer for wafer bonding, resulting in a simple, low cost fabrication process. The paper describes the process details and the optical properties of the resulting focus control mirrors, which have a diameter of 2 mm, a stroke in excess of 8 μm and very low residual aberration. Multiple actuation electrodes allow control of more than 0.4 μm peak-peak of spherical aberration.

SU8-2002 deformable membrane mirrors for primary focus control and compensation of focus-induced spherical aberration have been fabricated using a surface micromachining process with dry etching of silicon in XeF₂. This process has a higher yield and realizes larger mirrors with a twofold improvement in stroke, relative to a wet release etch process previously described. The use of 3 mm x 4.24 mm elliptical mirrors for 45° incidence focus control in microscopy is described.

In endoscopy there is a need for cameras with adjustable focus. In flexible and capsule endoscopes conventional focus systems are not suitable, because of restrictions in diameter and lens displacement range. In this paper it is shown that electrowetting-based variable-focus liquid lenses can provide a solution. A theoretical comparison is made between displacing and deforming lenses, and a demonstrator was built to prove the optical feasibility of focusing with liquid lenses in endoscopes.

Miniaturization and reduction of production cost of optical components in consumer electronics leads to wafer level optics. This miniaturization, associated with the increase of CMOS sensors resolution, generates new needs such as auto-focus (AF) and optical image stabilization (OIS) in order to reduce the blurring caused by hand jitter. In this paper, we propose a wafer scale technology to perform AF and introduce OIS functionality. We managed to create a tunable focal lens by filling with nematic liquid crystal (LC) an assembly of two glass substrates coated with circular hole patterned chromium electrodes and resistive transparent layers of Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS). When a voltage with tunable magnitude and frequency is applied to the electrodes, the resistive layer creates a non-uniform voltage distribution from the edge to the center of the aperture which depends on electrical parameters of PEDOT-PSS and LC. The resultant electric field generates a gradient orientation of the nematic director which allows to focus light polarized along the director. It is also possible to shift the optical axis of the lens by dividing the hole patterned electrodes in several sectors and to apply different voltages on each sectors. The principle of the shifting effect has been demonstrated but its magnitude has to be increased by using more adapted electrode structure to ensure the OIS function. Finally, we characterised the dynamical behaviour of the lens in both focus and shifting modes.

In this paper, a novel liquid lens design is presented, in which a diffractive surface with an aspherical phase contour, combined with the spherical-like refractive surface, is adopted to improve the inherent chromatic and spherical aberration performance when compared to conventional pure refractive-type configurations. Single-point diamond turning together with soft lithography is used to realize this structure. Both simulation and test measurement results agree well with each other and demonstrate significantly improved chromatic and spherical aberration within the tunable range of the lens.

We propose a microoptical approach to ultra-compact optics for real-time vision systems that are inspired by the compound eyes of insects. The demonstrated module achieves about VGA resolution with a total track length of 1.4 mm which is about two times shorter than comparable single aperture optics. The partial images that are separately recorded in different optical channels are stitched together to form a final image of the whole field of view by means of image processing. A software correction is applied to each partial image so that the final image is made free of distortion. The microlens arrays are realized by state of the art microoptical fabrication techniques on wafer-level which are suitable for a potential application in high volume e.g. for consumer electronic products.

As a matter of course, cameras are integrated in the field of information and communication technology. It can be observed, that there is a trend that those cameras get smaller and at the same time cheaper. Because single aperture have a limit of miniaturization, while simultaneously keeping the same space-bandwidth-product and transmitting a wide field of view, there is a need of new ideas like the multi aperture optical systems. In the proposed camera system the image is formed with many different channels each consisting of four microlenses which are arranged one after another in different microlens arrays. A partial image which fits together with the neighbouring one is formed in every single channel, so that a real erect image is generated and a conventional image sensor can be used. The microoptical fabrication process and the assembly are well established and can be carried out on wafer-level. Laser writing is used for the fabrication of the masks. UV-lithography, a reflow process and UV-molding is needed for the fabrication of the apertures and the lenses. The developed system is very small in terms of both length and lateral dimensions and has a VGA resolution and a diagonal field of view of 65 degrees. This microoptical vision system is appropriate for being implemented in electronic devices such as webcams integrated in notebookdisplays.

We present the optical design of an ultra-thin non-conventional objective lens (UTOL), based on the concept of superposition compound eye that some insects and arthropods have. One of the features of the UTOL is the capability to improve image quality by using an array of micro-tunable lens. Lens parameters, design and simulation techniques are described.

Driven by dramatic cost reduction of detectors, the market volume for thermography and infrared vision will triple by 2015. In our paper, we have both analyzed market and technical trends for uncooled infrared imagers' applications.

MEMS based handheld projection systems entered the consumer markets in 2009 and 2010. These low cost, compact and handheld devices enable many and diverse possibilities for consumer and industrial applications. In this paper we will discuss many of these applications and the performance requirements that will be needed to support them.

Head-up displays (HUD) in automobiles and other vehicles have been shown to significantly reduce accident rates by keeping the driver's eyes on the road. The requirements for automotive HUDs are quite demanding especially in terms of brightness, dimming range, supplied power, and size. Scanned laser display technology is particularly well-suited to this application since the lasers can be very efficiently relayed to the driver's eyes. Additionally, the lasers are only turned on where the light is needed in the image. This helps to provide the required brightness while minimizing power and avoiding a background glow that disturbs the see-through experience. Microvision has developed a couple of HUD architectures that are presented herein. One design uses an exit pupil expander and relay optics to produce a high quality virtual image for built-in systems where the image appears to float above the hood of the auto. A second design uses a patented see-through screen technology and pico projector to make automotive HUDs available to anyone with a projector. The presentation will go over the basic designs for the two types of HUD and discuss design tradeoffs.

A new kind of MEMS reflective display is being developed having high contrast and reflectivity, better than on printed paper. The system is based on novel vertical flaps, which can be electrostatically turned by 90° to horizontal position. After fabrication, the poly-silicon flaps are vertical to the wafer surface and on the top suspended by torsion beams. In this state the pixel is black, incoming ambient light passes by the flaps and is absorbed by an underlying absorptive layer. When the flaps are turned to horizontal position light is reflected back and the pixel gets white. A self-aligning four masks bulk microfabrication process is employed, which uses poly-silicon filling of high aspect-ratio cavities. Parylene was also employed as flap material. Thanks to auto stress-compensation the flaps are not deformed due to intrinsic stresses. Low actuation voltages down to 20V can be achieved.

A translatory MOEMS actuator with extraordinary large stroke - especially developed for fast optical path length modulation in miniaturized FTIR-spectrometers - is presented. A precise translational out-of-plane oscillation at 500 Hz with large stroke of up to 1.2 mm is realized by means of a new suspension design of the comparative large mirror plate with 19.6 mm² aperture using four pantographs. The MOEMS device is driven electro - statically resonant and is manufactured in a CMOS compatible SOI process. Up to ± 600 μm amplitude (typically 1mm stroke) has been measured in vacuum of 30 Pa and 50 V driving voltage for an optimized pantograph design enabling reduced gas damping and higher driving efficiency.

In this work we present the full characterization of an optical MEMS Fourier Transform Infra Red FTIR spectrometer fabricated by Deep Reactive Ion Etching DRIE Technology on Silicon substrate. Both electrical and optical properties of the spectrometer are measured. The presented techniques allows to build an engineering model for the spectrometer and to predict its main specifications taking into account the specificity of the MEMS technology used in the spectrometer fabrication.

A tunable IR filter based on a Fabry-Perot interferometer with two movable reflectors is reported. The infrared filter can be tuned over a wavelength range from 8 μm to 11 μm with voltages lower than 63 V. The FWHM bandwidth is lower than 200 nm and the peak transmittance is larger than 70 %. Simulation and practical shock test, both showed that the device can withstand 1500 g, 0.5 ms shocks according to Mil-Std-883G, method 2002.4, test condition B. The new infrared filter measures 8.5 mm x 8.5 mm and is suitable for the integration in a TO-8 housing in combination with a broadband infrared detector. The design benefits from relatively low stiffness of the mirror suspensions, compensation of vibration and gravitation induced forces possibly influencing the central wavelength and much lower actuation voltages as a result. Both reflector carriers are movable and are actuated by electrostatic forces.

The Mid-wave infrared (MWIR) spectrum has applications to many fields, from night vision to chemical and biological sensors. Existing broadband detector technology based on HgCdTe allows for high sensitivity and wide range, but lacks the spectral decomposition necessary for many applications. Combining this detector technology with a tunable optical filter has been sought after, but few commercial realizations have been developed. MEMS-based optical filters have been identified as promising for their small size, light-weight, scalability and robustness of operation. In particular, Fabry-Perot interferometers with dielectric Bragg stacks used as reflective surfaces have been investigated. The integration of a detector and a filter in a device that would be compact, light-weight, inexpensive to produce and scaled for the entire range of applications could provide spectrally resolved detection in the MWIR for multiple instruments. We present a fabrication method for the optical components of such a filter. The emphasis was placed on wafer-scale fabrication with IC-compatible methods. Single, double and triple Bragg stacks composed of germanium and silicon oxide quarter-wavelength layers were designed for MWIR devices centered around 4 microns and have been fabricated on Silicon-On-Insulator (SOI) wafers, with and without anti-reflective half-wavelength silicon nitride layers. Optical testing in the MWIR and comparison of these measurements to theory and simulations are presented. The effect of film stress induced by deposition of these dielectric layers on the mechanical performance of the device is investigated. An optimal SOI substrate for the mechanical performance is determined. The fabrication flow for the optical MEMS component is also determined. Part of this work investigates device geometry and fabrication methods for scalable integration with HgCdTe detector and IC circuitry.

We present a new multiplexed high-voltage driver architecture that departs from previous MEMS deformable-mirror drivers. Just one D/A converter and one high-voltage amplifier module drive the entire actuator array through a row-column addressing scheme. This approach reduces operational power consumption of a multiple-channel deformable-mirror driver by two orders of magnitude. It can provide for the integration of the deformable mirror and driver into a compact package, reducing driver volume by an order of magnitude. Both of these system modifications are essential for the implementation of MEMS deformable mirrors into space-based adaptive optics systems and other applications.

Multi-object spectroscopy is a powerful tool for space and ground-based telescopes for the study of the formation of galaxies. This technique requires a programmable slit mask for astronomical object selection. We are developing MEMS-based programmable reflective slit masks for multi-object spectroscopy that consist of micromirror arrays on which each micromirror of size 100 x 200 μm² is electrostatically tilted providing a precise angle. The main requirements for these arrays are cryogenic environment capabilities, precise and uniform tilt angle over the whole device, uniformity of the mirror voltage-tilt hysteresis and a low mirror deformation. A first generation of MEMS-based programmable reflective slit masks composed of 5 x 5 micromirrors was tested in cryogenic conditions at 92 K. Then, first prototypes of large arrays were microfabricated and characterized, but the reliability of these arrays had to be improved. To increase the reliability of these devices, a third generation of micromirror arrays composed of 64 x 32 micromirrors is under development. This generation was especially designed for individual actuation of each mirror, applying a line-column algorithm based on the voltage-tilt hysteresis of the actuator. The fabrication process was optimized and is now based on multiple wafer level bonding steps. Microfabricated devices have micromirror with a peak-to-valley deformation less than 3 nm. The mirrors can be tilted at 20° by an actuation voltage lower than 100 V. First experiments showed that our micromirrors are well suited for the line-column addressing of each micromirror.

A concept of a compact imaging spectrometer component based on an integrated waveguide array is elaborated and its design rules presented. The component, a focal plane array spectrometer (FPAS), is used in a similar way as a CMOS detector array or a CCD in a camera. The classical spectrometer, for instance an optical grating spectrometer, disappears from the optical system. The whole instrument is therefore reduced to the imaging optics and the FPAS in the focal plane which takes over the function of the spectrometer and detector array. Its potential for very high spectral resolution, minimal size, simple instrument integration, modularity and ruggedness makes it interesting for commercial and special applications like space. Two typical space optical instruments are reconceived using the FPAS with the result of a potential volume reduction of a factor five to eight while keeping the same performances. Also the specifications of simple and generic spectrometers based on the proposed component concept are very promising with respect to spectral resolution, volume and simplicity of instrument design and manufacturing.

Shaping light with microtechnology components has been possible for many years. The Texas Instruments digital micromirror device (DMD) and all types of adaptive optics systems are very sophisticated tools, well established and widely used. Here we present, however, two very dedicated systems, where one is an extremely simple MEMS-based tunable diffuser, while the second device is complex micromirror array with new capabilities for femtosecond laser pulse shaping. Showing the two systems right next to each other demonstrates the vast options and versatility of MOEMS for shaping light in the space and time domain.

The main goals of this work is the development of a large dual-axis MEMS mirror, ~3mm in diameter, capable of steering a laser beam within an angular cone of 60°. The targeted application involves the control of a laser beam with a particular interest for the resulting far field beam direction and profile. Finite element simulations using ANSYS modeling program were conducted to optimize the mirror design and determine the main characteristics of the mirror. The voltage required to tilt the mirror by 15° around each of the two axes was evaluated to be in the range of 700 V. The construction of this device is based on high precision structural dies assembly which relies on innovative developments in the fields of selective electroplating, deep reactive ion etching (DRIE) and thermocompression flip-chip bonding. The fabrication process involved the microassembly of 4 mirror parts, i.e. address electrodes, thick pedestal, gimbals structure and mirror plate. Single crystal silicon was used as material for the fabrication of the thick pedestal and mirror plate which provided the required large mirror-electrode gap and a high quality mirror with high flatness and low roughness. Soldering based on SnAu was considered for the microassembly of the thick pedestal to the address electrodes die, while Au-Au thermocompression bonding was considered to achieve the assembly of gimbals and mirror. The gimbals were supported by a polyimide sacrificial film to avoid damaging the hinges during mirror plate assembly.

Small size, low power consumption and the capability to produce sharp images without need of an objective make MEMS scanning laser based pico-projectors an attractive solution for embedded cell-phone projection displays. To fulfil the high image resolution demands the MEMS scanning mirror has to show large scan angles, a large mirror aperture size and a high scan frequency. An additional important requirement in pico-projector applications is to minimize power consumption of the MEMS scanner to enable a long video projection time. Typically high losses in power are caused by gas damping. For that reason Fraunhofer ISIT has established a fabrication process for 2D-MEMS mirrors that includes vacuum encapsulation on 8-inch wafers. Quality factors as high as 145,000 require dedicated closed loop phase control electronics to enable stable image projection even at rapidly changing laser intensities. A capacitive feedback signal is the basis for controlling the 2D MEMS oscillation and for synchronising the laser sources. This paper reports on fabrication of two-axis wafer level vacuum packaged scanning micromirrors and its use in a compact laser projection display. The paper presents different approaches of overcoming the well-known reflex problem of packaged MEMS scanning mirrors.

Resonantly driven oscillating MOEMS mirrors have many applications in the fields of optics, telecommunication and spectroscopy. Assuring stable resonant oscillation with well controlled amplitude under varying environmental conditions is a complex task, which can impede or retard incorporation of such MOEMS mirrors in large systems. For this we have developed compact modules comprising optical position sensing and driver electronics with closed loop control, which can ensure stable resonant operation of 1D and 2D micro-mirrors. In this contribution we present in much detail the position encoding and feedback scheme, and show very first experimental results with the novel 2D device.

Research interest for silicon nanophotonics is a topic of heavy interest currently due to the requirements for high density communications of integrated devices with small footprints in the semiconductor industry. Silicon photonic crystals (PhC) are nanoscale subwavelength periodic structures that possess the capability to induce strong interaction between light and matter. PhC nanocavities utilizes the photonic bandgap effect to trap certain frequencies of light within a small confined region for a diverse range of applications such as enhancement and suppression of spontaneous emission, efficient and compact lasers, add/drop multiplexers, optical filters and sensing etc. In this paper, we describe a mechanically-perturbative near-field probe with a special design shape to achieve low-loss and precise resonance control of PhC nanocavities. One-dimensional (1D) PhC are chosen for our study due to the ease of integrating with low-loss SOI waveguide technology and easy integration with nanomechanical structures. Sub-micron microelectromechanical systems (MEMS/NEMS) technology is introduced as an ideal integration platform with such near-field probe designs due to its capabilities to accurately control fine displacements without the need of bulky equipment such as atomic force microscopy (AFM), scanning near field microscope (SNOM) or highly sensitive piezo-controlled micromanipulator stages. We propose that such near-field probe designs are capable of achieving large resonance spectral shift of up to few nm with high re-configurability, highly accurate actuation displacements, low power consumption, and portability. In this work, we propose an approach utilizing numerical methods to study and characterize the electromagnetic interaction between PhC nanocavities and nanomechanically displaced near-field nano-probes.

This work aims to advance 3D position input and motion sensing in a variety of human-machine interface (HMI) and industrial robotics systems with a MEMS-mirror based optical 3D tracking approach which we termed "MEMSEye." The goal is to enable real time interaction with computers and robotics in ways that are more intuitive, precise and natural. Objects can be tracked which are marked either by light sources (e.g. a near-IR LED,) corner-cube retroreflectors (CCRs,) or with retro-reflective tape. Each "MEMSEye" unit can track the object with high speed and determine with high precision the azimuth and elevation (θX and θY) angles of the line between the unit and the object. When two or more such units are utilized to triangulate the object, relative position can be fully determined since distance information can also be obtained. This final XYZ position information down to sub-millimeter precision can be obtained in relatively large volumes at update rates of >20 kHz. A demonstration system capable of tracking full-speed human hand motion provides position information at up to 4m distance with 13-bit precision and repeatability. In another demonstration, a vector in free space is marked by two target CCRs and the MEMSEye system measures its orientation in space with ~0.1° precision by locating both CCRs in a time-multiplexed manner.

We have been developing a piezoresistive position detection for scanning micro mirrors in order to combine high position resolution with the capability of monolithic integration. In comparison to our formerly published results, the sensor sensitivity was strongly enhanced by implanting a 1 μm thick p-doped layer of NA ≈ 10¹⁷ cm^-3 into the lowly p-doped SOI device layer of NA ≈ 10¹⁵ cm^-3. This sensitivity was even further improved by at least a factor of 3 by a novel sensor design, allowing to couple more mechanical stress into the sensor structure.

We report on the advances towards the design and fabrication of a system consisting of two 10mm mirrors, one actuated magnetically and the other electrostatically. The system will be used for beam steering. The maximum resonant frequencies and deflection angle of each of the actuators will be reviewed and compared.

In this paper, we report the design and fabrication of a pre-aligned free-space optical interconnection (FSOI) device. A simple FSOI prototype device is designed based on Gaussian beam propagation calculation. All optical components of a FSOI device were designed in a single one mask, and the alignment between the optical components was achieved in the mask design stage. All optical components including microlens array and micro mirrors were positioned in an out-of-plane fashion. The fabrication was based on a tilted Ultraviolet (UV) lithography of the SU-8 mold and fast replication using a UV curable polymer. This method allows the production of integrated optical systems similar to conventional optical benches in microscale and eliminates the need for tedious high-precision assembly.

Advanced 3D CAD and optical simulation software were used to design first iteration on-CMOS chip MOEMS micro-systems. A Si Avalanche-based LED and an array of detectors interface laterally with a single arm canti-lever system, all to be fabricated with CMOS technology. Silicon nitride wave-guides are used as optical propagation channels offering losses of lower than 1dB.cm^-1. Micro-bending and multi-planing of the wave guiding is possible. Far-field manipulation of the emitted channel radiation is possible. Mechanically designed and sensor systems can be added by means of CMOS post processing techniques. The emission level of the Si CMOS Av LEDs is 10⁺³ higher than the detectivity of silicon p-i-n detectors, offering good dynamic range in detection and data analyses. The mature processing characteristics of CMOS technology offers high integration possibilities and low cost manufacturing of the designed systems.

Spatial light modulators (SLM) developed at the Fraunhofer Institute for Photonic Microsystems (Fraunhofer IPMS) are based on arrays of tiltable micro mirrors on a semiconductor chip. Development and optimization of such complex micro- opto-electro-mechanical systems (MOEMS) require detailed knowledge of the device behaviour under application specific operating conditions. In this context, the need for a high resolution surface topography measurement under laser exposure (in situ) was identified, complementing ex situ characterizations where laser exposure and micro-mirror topography measurements are carried out sequentially. For this purpose an interferometric setup using the phase-shift principle was designed and is presented in this paper. For setup verification SLMs were irradiated at 248 nm (KrF) with energy densities of up to 10 mJ/cm2. In general, the setup is neither limited to a specific illumination wavelength nor to micromirrors as structures under test. Influences of different illumination parameters such as energy density, laser repetition rate etc. on the mirror topography can be studied in detail. Results obtained so far reveal valuable feedback for further technological optimization of mirror array devices.