In this study, an analytical model, taking into account the coupled photoelastic and thermal-optical effects, is established to evaluate the temperature dependence of a single-chip silicon micromachined Fabry-Perot pressure sensor. The results show that temperature variation has significant impact on the micromachined Fabry-Perot pressure sensor with conventional flat diaphragm. A new membrane-type silicon micromachined Fabry-Perot pressure sensor with a novel deeply corrugated diaphragm is then proposed. The sensor is fabricated on a single-chip using both surface- and bulk-micromachining techniques. Both analytical and experimental results show that the cross-sensitivity to temperature of Fabry-Perot pressure sensors, can be substantially alleviated by the proposed single deeply corrugated diaphragm/mirror.

The function of a large number of MEMS and NEMS devices relies critically on the transduction method employed to convert the mechanical displacement into electrical signal. Optical transduction techniques have distinct advantages over more traditional capacitive and piezoelectric transduction methods. Optical interferometers can provide a much higher sensitivity, about 3 orders of magnitude, but are hardly compatible with standard MEMS and microelectronics processing. In this paper, we present a scalable architecture based in silicon on sapphire (SOS) CMOS 1 for building an interferometric optical detection system. This new detection system is currently being applied to the sense the motion of a resonating MEMS device, but can be used to detect the motion of any object to which the system is packaged. In the current hybrid approach the SOS CMOS device is packaged with both vertical cavity surface emitting lasers (VCSELs) and MEMS devices. The optical transparency of the sapphire substrate together with the ultra thin silicon PIN photodiodes available in this SOS process allows for the design of both a Michelson type and Fabry Perot type interferometer. The detectors, signal processing electronics and VCSEL drivers are built on the SOS CMOS for a complete system. We present experimental data demonstrating interferometric detection of a vibrating device.

We describe the development of a MEMS-based correlation radiometer for remote detection of chemical species. The radiometer utilizes a new type of MEMS programmable diffraction grating called the Polychromator. The Polychromator contains an array of 1024 electrostatically actuated reflective beams that are 10 microns wide by 1 cm long, and have a vertical travel of approximately 2 - 4 microns. The Polychromator grating is used to replace the reference cell of conventional correlation radiometry. Appropriate programming of the deflection profile of the grating array enables the production of any spectral transfer function desired for the correlation measurement. Advantages of this approach to correlation radiometry include the ability to detect multiple chemical species with a compact instrument, the ability to optimize the reference spectra to eliminate chemical interferences, and the ability to produce reference spectra for hazardous and transient species.

MEMS based SnO₂ gas sensor with sol gel synthesized mesoporous nanocrystalline (<10 nm) semiconductor thin (100~150 nm) film has been recently developed. The SnO₂ nano film is fabricated with the combination of polymeric sol gel chemistry with block copolymers used for structure directing agents. The novel hydrogen sensor has a fast response time (1s) and quick recovery time (3s), as well as good sensitivity (about 90%), comparing to other hydrogen sensors developed. The improved capabilities are credited to the large surface to volume ratio of gas sensing thin film with nano sized porous surface topology, which can greatly increase the sensitivity even at relatively low working temperature. The gas sensing film is deposited onto a thin dielectric membrane of low thermal conductivity, which provides good thermal isolation between substrate and the gas-sensitive heated area on the membrane. In this way the power consumption can be kept very low. Since the fabrication process is completely compatible with IC industry, it makes mass production possible and greatly reduces the cost. The working temperature of the new sensor can be reduced as low as 100°C. The low working temperature posse advantages such as lower power consumption, lower thermal induced signal shift as well as safe detection in certain environments where temperature is strictly limited.

We have experimentally demonstrated operation of a laterally deformable optical NEMS grating transducer. The device is fabricated in amorphous diamond on a silicon substrate with standard lithographic techniques. For small changes in the spacing of the grating elements, a large change in the optical reflection amplitude is observed. An in-plane motion detection sensitivity of 160 fm/√Hz has been measured, which agrees well with theoretical models. This sensitivity compares favorably to that of any other MEMS transducer. Calculations predict that this sensitivity could be improved by up to two orders of magnitude in future designs. As well as having applications to the field of accelerometers and other inertial sensors, this device could also be used as a modulator for optical switching.

SU-8 is a negative-tone photoresist that can serve as a complete optical bench for micro-photonic systems. Functional optical devices and passive alignment structures can all be formed in the same material system with common processing steps. Many interrelated process parameters control the final geometry of structures formed in SU-8, but all can be accurately simulated and predicted by computer modeling. In this work, a comprehensive model of the lithography process was developed and combined with rigorous electromagnetic simulation. It was applied to predict sidewall slope of a tall structures as well as the geometry and transmission spectra of a three-dimensional photonic crystal. The model is seen as an enabling step toward realizing optimized micro-photonic systems in SU-8.

The eventual, widespread insertion of Micro-Opto-Electro-Mechanical Systems (MOEMS) into the marketplace rests fundamentally on the ability to produce viable components that maximize optical performance while minimizing power consumption and size. In addition, the incorporation of optical reconfigurability into custom MOEMS devices offers an extra degree of freedom not possible with conventional components. Active control of surface topology allows for one component to perform multiple functions thus reducing cost and complexity. This paper will focus on the current status of the MOEMS research program at the University at Albany Institute for Materials’ (UAIM) NanoFab 200 with several examples described to illustrate component and system development. In particular, among the MOEMS research portfolio at UAIM, the development of selected MOEMS-based, active optics will be discussed. This active control of diffraction and reflection forms the basis for the utility of such devices. Leveraging the extensive research expertise on the patented MEMS Compound Grating (MCG), emphasis will be placed on the extension of the approach to novel designs, materials and fabrication methods to yield low power, high performance prototypes. The main focus of this paper is on the development of a polymer version (including sacrificial layer, in some designs) of the MCG which allows for ease of fabrication and a reduced electrostatic actuation voltage. Following a system design effort, several generations of the component were fabricated to optimize the process flow. Component metrology, electromechanical characterization and initial results of optical tests will be reported. A second example presented is the design and prototype fabrication of a spring micrograting using a customized SOI process. This highly flexible component builds on the MCG concept and yields an order of magnitude reduction in actuation voltage. These examples will be presented against a backdrop of the broad UAIM program to provide an overview of the applications of MOEMS and their integration with complementary technologies at the wafer level.

While testing electrical properties in microsystems is a well-developed art, the testing of mechanical properties of MEMS devices is not. 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 (MZI). MZI is monolithically integrated on top of a electrostatically rotatable micromirror loaded with the sensing arm of MZI. A single mode buried channel waveguide based on silica/silicon oxinitride/silica structure is used. It performs a low optical attenuation and a coupling efficiency of 55% from waveguide to a standard fiber, connecting MZI to outside world (light source and detector). The working principle of MZI read out is based on the change of effective refractive index of guided waves of MZI induced by displacement of the deformable structure, obtained via the elastooptic effect. The technology process steps with special emphasis to the fiber-to-waveguide coupling based on V-grooves is detailed here. Our goal is aiming to obtain an angular alignment of ± 0.2 deg. of V-groove walls with <110> directions and the vertical misalignment not, exceeding ± 0.6 μm.

Two different approaches for ultra flat image acquisition sensors on the basis of artificial compound eyes are examined. In apposition optics the image reconstruction is based on moire or static sampling while the superposition eye approach produces an overall image. Both types of sensors are compared with respect to theoretical limitations of resolution, sensitivity and system thickness. Explicit design rules are given. A paraxial 3x3 matrix formalism is used to describe the arrangement of three microlens arrays with different pitches to find first order parameters of artificial superposition eyes. The model is validated by analysis of the system with raytracing software. Measurements of focal length of anamorphic reflow lenses, which are key components of the superposition approach, under oblique incidence are performed. For the second approach, the artificial apposition eye, a first demonstrator system is presented. The monolithic device consists of a UV-replicated reflow microlens array on a thin silica-substrate with a pinhole array in a metal layer on the backside. The pitch of the pinholes differs from the lens array pitch to enable an individual viewing angle for each channel. Imaged test patterns are presented and measurements of the angular sensitivity function are compared to calculations using commercial raytracing software.

Silex Microsystems produces Silicon Optical Benches and Silicon Optical Mirrors for a variety of customers on an international market. The core of the activity is the MEMS chip itself and the related processes. By qualifying processes Silex provides the opportunity for clients to increase the degree of development in the MEMS cores of their products. The designs are customized in order to meet the specifications for a wide customer base with even wider demands. The Silicon Optical Benches can incorporate BCB layers in order to integrate RF-lines and make it possible to design for example coils of high performance. The polysilicon resistors have been qualified to be stable within 3-ppm over 6 months at elevated temperatures. The polysilicon temperature dependence makes it possible to use the resistors in order to measure temperature and excludes thermistors from the designs. Electrical feed through vias can be incorporated to enable backside connection and simplify packaging. The Silicon Optical Mirrors are produced both as large arrays of small mirrors and smaller arrays of larger mirrors depending on applications. Also for the mirrors the incorporations of electrical vias simplify design and process issues. The pads under the mirrors are connected from backside and it is possible to avoid difficult contacting down in cavities.

Photonic crystal with defects such as (L₁H₁)^m L_CH₂(L₂H₂)ⁿ is investigated in this paper. The band gap edge transmission peak is narrowed when the couple-layer LC and the cover layer H₂(L₂H₂)ⁿ are added to the photonic crystal (L₁H₁)^m. Two different structures were studied in thip paper. Structure A is not suitable for the tunable filter, which has two discrete tuning regions. Structure B provides a good optical tuning method: large dynamic range (>150 nm), narrow bandwidth (FWHM is about 2 nm) and good tuning linearity. This kind of structure can be fabricated by the surface micromachined technique easily.

A novel micro-optical crossconnect switch based on the use of diffractive optical elements is introduced. A set of micro-actuated diffractive optical elements are used to reshape the optical beam as well as establish the interconnection required between two arrays of input and output optical fibers. The coupling efficiency of the switch is shown to be far higher than those using reflecting mirrors. Possible techniques for the fabrication of the switch are discussed.

In this paper, we present a thermo-optic effect optical switch provided with heater electrodes to a single mode polymer optical waveguide fabricated by revolutionary replication technology. A low-cost and high-performance optical switch is a key issue to expand the FTTH and Metro Optical Networking. The optical switch consists of a Y-branch polymer waveguide and thin metal film heaters on the surface of the waveguide. The waveguide has been prepared by photopolymerization (2P) method, which is suitable for submicron fine pattern replication, e.g. diffractive optics, and for the large-scale production with a short processing time. Thin metal film heaters were formed on the waveguide using the bonding technology of MEMS. The insertion loss of less than 2.5 dB, the switching time of less than 3 ms and the extinction ratio of more than 15dB were obtained respectively. Moreover, VOA has also been produced with the Mach Zehnder interferometer (MZI) system using the same technology as described above, and an attenuation rate of 25dB was obtained at a power consumption of 20mW.

POF (Plastic Optical Fiber) is more suitable than the quartz optical fiber for indoor LAN (Local Area Network), for example in-home or office networks because of its flexibility and ease of connection by relatively large core diameter.1 x 2 optical switches for indoor LAN using POF have been developed. For switching by movement of a POF, large displacement is necessary as core diameter is large (e.g. 0.486mm). A SMA (shape memory alloy) coil actuator is used for large displacement and a magnetic latching system is used for fixing the position of the shifted POF. Switching speed is less than 0.5 second and the insertion loss of the fabricated switch is 0.40 to 0.50dB. The insertion loss is 0.06 to 0.09dB using index-matching oil. PCF (Plastic Clad Fiber) has also large core diameter (e.g. 0.20mm) and an optical switches using PCF will be useful for short distance network between buildings.

In modern optical diagnostics there is an increasing interest in compact and cost-effective devices, i.e. for the analysis of surfaces, thin films, solids, powders, pastes, gels, liquids and alike. Therefore fast and non-invasive measurements are necessary. For the realization of such devices, micro system technology especially Micro-Opto-Electro-Mechanical System (MOEMS) technology is suitable. Hence two main miniaturized optical analyzer modules employing MOEMS have been developed. They are based on the principle of spectral sensing in the infrared range by means of a scanning micro mirror with an integrated diffraction grating or in combination with a separate grating. Using these configurations it is possible to project a specific wavelength onto an exit slit in front of an infrared detector. The first packaging approach is based on assembled laser-cut stainless steel sheets and optical standard components. During the further development different setups with improved reliability and accuracy have been realized. Due to the requirement of compact dimensions and short optical paths modern methods e.g. rapid prototyping were utilized to optimize packaging and optical setup and therefore the performance of the complete system. In this work the characteristics and the measurement results of different development levels will be reviewed. Furthermore we address issues, challenges and performance optimization of MOEMS packaging with respect to ultra compact micro mirror spectrometers. Finally, the applications and the feasibility of such miniaturized spectrometer systems are discussed.

Densely integrated systems in the future will incorporate device and communication technologies that span the domains of digital and analog electronics, optics, micro-mechanics, and micro-fluidics. Given the fundamental differences in substrate materials, feature scale and processing requirements between integrated devices in these domains, it is likely that multi-chip, system-in-package, integration solutions will be required for the foreseeable future. The multi-domain nature of these systems necessitates design tools that span multiple energy domains, time and length scales, as well as abstraction levels. This paper describes a case study of the modeling of a photonic/multi-technology system based on a 3D volumetric packaging technology implemented with Fiber Image Guide (FIG) based technology. It is 64x64 fiber crossbar switch implementation using three Silicon-on-Sapphire mixed signal switch die with flip-chip bonded VCSEL and detector arrays. We show a single end-to-end system simulation of the O/E crossbar working across the domains of free-space and guided wave optical propagation, GaAs O/E and E/O devices, analog drivers and receivers and integrated digital control.

To develop an integrated optical bench or free-space optical system, a focusing lens’ optical axis is required to be parallel with the substrate on which the whole system is located. In micro-optical systems, hinged lenses were fabricated in surface technologies and suspended with a mechanical hinge, then driven up to the required vertical position using electrostatic or electromagnetic actuation. In this paper, we report the research work to design, simulate, and fabricate a new type of microlens using direct lithograph of SU-8 resist. Without any assembly process, this microlens’ optical axis is parallel with the substrate on which the whole optical system is. The lenses obtained this way are perpendicular to the substrate and can be pre-aligned with other micro optical components. The focus of the lens can be controlled with different surface curvature by using different cylindrical beams, expose dosage, and development time. A numerical simulation is done about the SU-8 development. The optical simulation is also being done with ZEMAX software. At the same time, the optical properties of the cured SU-8 and the optical properties of this cured-SU-8 refractive microlens are also being tested and presented in this symposium.

Unlike other Micro Electro Mechanical System (MEMS) type devices packaging, MEMS type optical devices require higher standard of packaging technique and careful material selection than any other MEMS type products. A number of attempts and a lot of efforts have been devoted to achieve a reliable MEMS type optical device. In this paper, we have achieved highly reliable MEMS type variable optical attenuator (VOA), which passed the Telcordia reliability standard for optical components, by our advanced packaging process and careful reliability considerations in the initial product design step. Our advanced packaging process includes, ultra fine optical fibre alignment on the MEMS chip, securing the aligned optical fibre and hermetic sealing technique. This paper will discuss above advanced packaging issues in detail and reliability test result of the device fabricated according to the developed packaging method.

In a mature industry all elements of the supply chain are available and are more or less in balance. Mainstream technologies are defined and well supported by a chain of specialist companies. Those specialist companies, offering services ranging from consultancy to manufacturing subcontracting, are an essential element in the industrialization. There specialization and dedication to one or a few elements in the technology increases professionalism and efficiency. The MOEMS industry however, is still in its infancy. After the birth and growth of many companies aiming at development of products, the appearance of companies aiming at the production of components and systems, we see know the first companies concentrating on the delivering of services to this industry. We can divide them in the like : * Design and Engineering companies * Foundries * Assembly and Packaging providers * Design and simulation software providers For manufacturing suppliers and customers the lack of industry standards and mainstream technologies is a serious drawback. Insight in availability and trends in technology is important to make the right choices in the field of industrialization and production. This awareness was the reason to perform a detailed study to the companies supplying commercial services in this field. This article focuses on one important part of this study: packaging and assembly. This tends to remain a bottleneck at the end of the design cycle, often delaying and sometimes preventing industrialization and commercialization. For nearly all MEMS/MST products literally everything comes together in the packaging and assembly. This is the area of full integration: electrical, mechanical, optical fluidic, magnetic etc. functionalities come together. The problems associated with the concentration of functionalities forms a big headache for the designer. Conflicting demands, of which functionality versus economics is only one, and technical hurdles have to overcome. Besides that, packaging and assembly is from nature application specific and solutions found are not always transferable from one product to another. But designers can often benefit from experience from other and general available technologies. A number of companies offer packaging and assembly services for MEMS/MST and this report give typical examples of those commercial services. The companies range from small start-ups, offering very specialized services, to large semiconductor packaging companies, having production lines for microsystem based products. Selecting the proper packaging method may tip the scales towards a product success or towards a product failure, while it nearly always present s a substantial part of the cost of the product. This is therefore is not a marginal concern, but a crucial part of the product design. The presentation will also address mayor trends and technologies. Finally, the article provides sufficient levels of classification and categorisation for various aspects for the technologies, in specific, and the industry, in general, to provide particularly useful insights into the activities and the developments in this market. With over 50 companies studied and assessed, it provides an up to date account of the state of this business and its future potential.

Low stress membrane mirrors will allow improved wave front correction in vision science and astronomical adaptive optics systems. We have fabricated low stress membrane mirrors from single crystal silicon, and flip chip bonded membranes to electrode arrays. These devices operate at lower voltage and have greater stroke than existing membrane mirror devices; they have 256 control electrodes, and are driven by off chip electronics. Devices have a single electrode plane and are pre-biased to allow full wave front correction. We have demonstrated these devices in an adaptive optics system consisting of a coherent source, and a Shack-Hartmann wave front sensor. We compare the experimental performance of the devices to computer simulations and theoretical calculations.

In this paper we present a micromirror fabrication technique without using silicon-on-insulator (SOI) wafers. Torsional electrostatic micromirrors have been fabricated using a combination of chemical mechanical polishing (CMP) process and anodic bonding. The size of fabricated silicon mirror plate was 610×400 μm² and 20 μm thick. The steering electrodes have been fabricated in the dry etched trench on the glass wafer by electroplating process and CMP processing without damage of electrodes during anodic bonding process. The surface roughness of polished silicon micromirror(Ra) was 3.19nm. The single crystal silicon mirrors are electrostatically actuated with parallel bottom electrodes placed 8 μm below the mirror plate, and they could be stably operated in a ±1.1°. The pull-in voltage has been measured as 520 V. The resonant frequency of the fabricated torsion mirror was 47.3 kHz.

An adaptive control scheme to achieve accurate positioning and trajectory tracking of torsional micromirror is presented in this study. The torsional micromirror is fabricated by using surface micromachining processes, in which phosphorusdoped polysilicon is employed as the structure layer as well as the bottom electrode. Generally, every fabrication step contributes to imperfections in micromirror. The proposed adaptive self-tuning controller has advantages of on-line compensating parameter variations or model uncertainty of the torsional micromirror, resulting from fabrication imperfections that produce asymmetric structures, misalignment of actuation mechanism, and deviations of the center of mass from the geometric center. In our design, the amount of detection of differential capacitance between the left and right electrodes at the femtofarad (fF) level is utilized as feedback signals. Simulation results show that the designed controller has better transient response compared to the PID control scheme. The micromirror can follow the reference trajectory (5 kHz) with acceptable error in several microseconds, thus the convergence of the controller is confirmed. Furthermore, the unknown model parameters can be identified correctly while the so-called persistent excitation condition is satisfied.

One dimensional torsional micro mirrors for laser steering applications have been developed and manufactured at Fraunhofer Institute of Photonic Microsystems. Several design variations with rectangular plates are available. The device can be operated in resonant mode and quasistatic mode as well. The device is fabricated out of a BSOI wafer and a second conductive silicon wafer. The structure is assembled by conductive adhesive bonding. Torsional springs connect the mirror plate to the mirror frame mechanically and electrically. Filled isolation trench structures separate volumes of different electrical potentials at the frame and at the deflective mirror respectively. Comb drive structures at both sides of the deflectable mirror and the part of frame located opposite increases capacitance at both mirror half sides. Applying a low level drive voltage between the combs, the mirror can be operated in resonant mode. The second silicon wafer is placed below the deflective mirror and is electrically at ground. Applying a electrical potential of higher level to one side of the deflectable mirror, the mirror can be driven quasistatic and resonant as well. While the drive voltage is applied to one side of the mirror, the comb drive structure of the opposite side can be used for capacitance based position read out.