A novel type of light modulating micromirror device has been designed and fabricated. A unique hinge structure provides the device with the potential for modulating both the phase and amplitude of light signals, while its high thermal conductivity makes the device amenable to high power laser applications. An extremely high fill factor can be attained since the hinges lie entirely beneath the mirror surface. This hidden hinge structure is comprised of a single level and therefore involves a simple fabrication process. Micromirrors with dimensions ranging from 100 micrometers X 100 micrometers to 300 micrometers X 300 micrometers with maximum deflection angles from 2 degree(s) to 4 degree(s) were fabricated. The devices were characterized in terms of the reflecting surface optical quality, the operational modes attainable, the critical voltages (as low as 15 volts), and the response time (as short as 125 microsecond(s) ).

Using flip-chip bonding techniques with micromachined conductive polymer bumps and passive alignment techniques with electroplated side alignment pedestal bumps, a prototype MOEMS structure for optical I/O couplers has been designed, fabricated and characterized. A top MOEMS substrate has through holes, contact metal pads, and side alignment pedestals with electroplated copper to align GaAs MSMs. Conductive polymer bumps have been micromachined on contact metal pads of GaAs MSMs using thick photoresist bump-holes as molding patterns. A diced GaAs photodetectors die with micromachined conductive polymer bumps was aligned to the side alignment pedestals within +/- 5 micrometers and flip-chip bonded onto the substrate. This conductive polymer flip-chip bonding technique allowed a very low contact resistance (approximately 10 m(Omega) ), a lower bonding temperature (approximately 170 degree(s)C), and simple processing steps. The GaAs MSM photodetectors flip-chip mounted on the top of OE-MCM substrate showed a low dark current of about 10 nA and a high responsivity of 0.66 A/W. By using bulk- micromachining, conductive polymer flip-chip bonding, and passive pedestal alignment techniques, a prototype MOEMS structure for optical I/O couplers realized in this work shows high potential to use as a fundamental building block in OE-MCMs.

A silicon based micro mirror array is a highly efficient component for use in optical applications as adaptive optical systems and optical correlators. Many types of micro mirror or micro mirror array have been studied and proposed in order to obtain the optimal performance according to their own purposes. A micro mirror array designed, fabricated and tested in this paper consists of 5 X 5 single layer polysilicon-based, electrostatically driven actuators. The micro mirror array for the optical phase modulation is made by using only two masks and can be driven independently by 25 channel circuits. About 6 (pi) phase modulation is obtained in He-Ne laser ((lambda) equals 633 nm) with 67% fill-factor. In this paper, the deflection characteristics of the actuators in controllable range were studied. The experimental results show that the deflection characteristics is much dependent upon a residual stress in flexure, the initial curvature of mirror due to stress gradient and an electrostatic force acted on other element except for mirror itself. The modeling results agree well with the experimental results. Also, it is important to fabricate a flat mirror that is not initially curved because the curved mirror brings a bad performance in optical use. Therefore, a new method to obtain the flat mirror by using the gold metallization in spite of the residual stress unbalance is proposed in this paper.

This paper describes the design and fabrication of surface- micromachined micromirror array with hidden joint structures. Instead of using elastic spring components, such as cantilevers, flexure beams, and torsion hinges, we have used joint structure composed of pin and staples to support the mirror plate. The position of the joint structure, under the mirror plate, makes large active surface area possible. Arrays of 100 X 110 micrometers ² sized micromirrors with two different staple shapes are designed and fabricated. These flexureless micromirrors are driven by electrostatic force between mirror plate and address electrode under it. As the mirror plate has discrete deflection angles the device is well suited for spatial light modulating purpose. Four-level metal structural layers and semi-cured photoresist sacrificial layers are used in the fabrication process and sacrificial layers are removed by dry release process using oxygen plasma. Performance characteristics are measured by applying voltage difference between the ground electrode, which contacts the mirror plate via support post, and an address electrode.

Here we propose and report a novel fiber optic hydrogen sensor which is constructed by depositing palladium over an exposed core region of a multimode fiber. Since the length, thickness, and composition of the palladium patch can be controlled independently of each other, it is possible to increase the speed of our sensor at lower temperatures while maintaining its sensitivity. This is not possible in so called micromirror sensors due to a restriction imposed on their active area of interaction by the fiber optic cross- sectional area. Micromirror fiber optic sensors, studied in the past, take advantage of the reflection/absorption of a palladium film deposited at the end of a fiber and it is only possible to have one sensor per a fiber optic strand. On the other hand, since many evanescent field-based sensors can be deposited over a single fiber optic strand, multiplexing can be easily accomplished using both time- domain and wavelength-domain methods. Using a 100 angstroms thick palladium with 1.5 cm interaction length, we could detect hydrogen in the 0.2% to 0.6% range with corresponding response times of 30 s to 20 s at room temperature. At -10 degree(s)C, these response times increased by a factor of only 2 which is impressive.

Recent progress of the deep reactive ion etching explores several new applications of 3D structures of silicon devices. We have developed new optical and electrical devices having the penetrating holes to transmit the optical beam to the down stream. The transmission silicon position sensor having the divided cell type photodiode on the Si mesh structure is fabricated. The beam splitter is considered to be integrated in this device and a part of the incident light beam is detected by the photodiode. Using nearly same technique, the pinhole of the spatial filter surrounded by the divided cell type photodiode is fabricated to detect the relative position between the incident beam spot and the center pinhole.

In this paper, a new method which simplifies the design process of micromachined deformable mirrors is presented. By varying the widths of an array of constant-pitched electrodes, the electrostatic-force profile needed to shape the mirror can be precisely controlled by using only one voltage input. A mirror was formed by a thin membrane micromachined from a silicon wafer and is coated with a thin metallic film. The electrodes were deposited on a ground plane over which the membrane is suspended. Viewing the mirror as a surface composed of many small patches with the same pitch, we can calculate the required traction of each patch from the deformed shape by using basic elasticity formulae. The analytical solution of the electrostatic field between the mirror and a electrode of one pitch can be obtained by adopting conformal mapping method. Once the relationship between the traction and the width of the electrode was established, the widths of all the electrodes can be obtained by fitting the electrode width to that of the design goal. This new method applies equally well to design both membrane electrostatic actuators and capacitive sensors. The design method is not necessary to solve the PDEs (Partial Differential Equations) of the structure governing equations, and is always valid for any deformation.

An ultra-miniaturized sensor head for absolute measurement which has a size of less than 5 mm cube is realized. The sensor works by means of the optical triangulation. To achieve the optical function, the sensor consists of a three layer polymer waveguide patterned by X-ray lithography, an incoupling fiber and two detection fibers and micro cylindrical lenses which are also fabricated by X-ray lithography. The fibers and the cylindrical lenses are placed into the waveguide without any active alignment by using waveguide walls as guiding and fixing structures. The ratio of intensity detected in the two detection fibers is a measure for the distance between the object and the sensor. The detection range of the sensor is 1 to 6 mm between the sensor and an object with diffusively reflecting surface.

One of the most difficult problems of large-screen projection displays and micromachining systems is overloading of a panel to be projected (for example a liquid crystal panel) with illuminating light. The problem can be solved by using, on the way from a panel to be projected to a screen or to an object to be treated, an optical amplifier with high enough amplification. The prospects of using laser amplifiers in these devices are discussed. Among all laser amplifiers the most suitable for this application are now pulsed metal vapor laser and metal halide laser amplifiers. They have rather high gain enabling amplification in the range from 10² to 10⁴ and high average and peak output power sufficient to illuminate a large screen or to treat a material. The main characteristics of these amplifiers are described. The results of experimental investigations of projection systems with copper, copper bromide, gold and some other metal vapor amplifiers are reported. In all cases good quality amplified images were obtained. Average power at the output of amplifiers was under typical conditions of operation comparable with the output power of a laser with the same amplifying element. Measurements of contrast of amplified images showed that under normal conditions of operation it is close to the contrast of the input picture even at strong saturation of the amplifying medium. The influence of the amplifier saturation is briefly discussed. The results of experiments with TV projection systems using two types of liquid crystal spatial light modulators are presented and prospects of development of large-screen projection displays and systems for micromachining with laser light are discussed.

Transparent polymer elements, containing both 3D-positioning structures and planar optical elements made by surface structuring, open the way for the mutual passive alignment of optical elements with respect to fibers, detectors and light sources in micro-optical benches with sub-micron precision. A fabrication process is presented for polymer inserts in micro-optical benches, which combines the mechanical precision of the LIGA-process with the wide variety of optical functions offered by diffractive optical elements. For this purpose, metal masters with lens elements made by surface structuring, and frame structures made with deep X-ray lithography and electroplating were used in a combined molding tool, and precision micro-optical elements were replicated by injection molding. The fabrication of the different parts of the mold insert and the alignment and fixing schemes for metal plates forming the micro cavity is described in detail. Injection molding experiments have been carried out using polycarbonate, a polymer known for its good optical properties. We discuss the different designs of mold inserts and injection geometries used for the mold, which were chosen in order to control the shrinkage of the molded element, to restrict damages during demolding, and to avoid inhomogeneities in the area of the lenses due to flow anisotropies and seam lines. We report on the characterization of the molded lens components. Injection molded lens structures are compared with hot embossed replicas, and used for the purpose of collimation applications. The imaging properties of these optical elements from single mode fibers onto single mode fibers is discussed. The miniature optical elements are arranged in arrays with 250 micrometers pitch which make them well suited for applications with fiber ribbons. Various positioning schemes and bench arrangements are under development.

We report optical coupling loss and vibration characterization for packaging of 2 X 2 vertical torsion mirror switches. The coupling losses of fiber-to-fiber and fiber-lens-lens-fiber are examined in order to design 2 X 2 MEMS optical switches required for the performance specification. The results indicate that the fiber-lens- lens-fiber configuration provides a over 1 mm working distance of 2.5 dB loss between the lens centers. The fiber- to-fiber only allows 175 micrometers for the same loss. In addition, the mechanical frequency response of the vertical torsion mirror is experimentally examined by electrostatic excitation. The discrepancy between the calculated and the measured nature frequencies is investigated by the study of the effect of the in-house post processes.

We discuss a novel deposition method that uses electric field and local probes to deposit materials from gas phase. Using gas-phase metal-organic precursors, semiconductors such as Si, GaAs, GaN, and SiC, metals such as Al, Cu, Mo, W, and Pt, and oxides such as SiO₂, and Al₂O₃, and other insulators such as Si₃N₄ can be deposited. These precursor gases are carried over the local tip area where relatively large electric fields (10⁶ V/cm: field emission mode) are generated by applying a few volts to the probe. In the tip region, the electric field decomposes the precursor molecules and deposits the desired material over the substrate. By choosing the tip to substrate polarity appropriately, deposition over the tip is avoided. The rest of the decomposed precursor molecule remains in the gas phase and is carried away by the carrier neutral gas. A novel approach, that involves laterally vibrating the local probe, is used to achieve line-widths in the wide range of 100 angstroms to 10 micrometers . Local probes, depositing in parallel, efficiently cover large areas needed in integrated circuits. The speed of deposition by our proposed local probes is only limited by the rate of the material delivery by the carrier gas. In this novel approach the deposition chamber encloses a volume that is slightly larger than the local tip-substrate volume. Thus, the whole fabrication facility can be fabricated on silicon using bulk and surface micromachining used in micro-electro-mechanical systems (MEMS) technologies. All the valves, flow meters, pressure gauges and analysis tools can also be fabricated using MEMS technologies and constitute an integral part of the micro- fabrication facility.

A bulk micromachining process for fabricating extremely high aspect ratio metal structures is developed. The structures are thin films perpendicular to the plane of the substrate. The metal structures offer various physical and chemical properties depending on the choice of the metal used. Internal stress considerations for the choice of metal are also discussed.

In the fields of adaptive optics and pattern recognition system, SLM is used to modulate the phase and amplitude of incident light in order to correct aberration in an optical system through active control of mirror array. In this paper, a micro spatial light modulator (SLM) array, which has one hundred of micro SLM, that is to say, 10 X 10 array, for phase and amplitude modulation of incident light is designed and fabricated using surface micromachining technology. In order to maximize the fill factor and minimize diffraction effect, hidden spring structure is used. A designed micro SLM is composed of a mirror plate, upper electrode, five support posts, and bottom electrode. The spring structures are composed of double crab leg spring for phase modulation and torsional spring for amplitude modulation. The micro SLM is actuated by electrostatic force generated by electric potential applied between upper electrode and bottom electrode. In case of phase modulation, the maximum deflection length of mirror plate is 4 micrometers and in case of amplitude modulation, it is designed to be capable of tilting +/- 5.4 degree(s) to reflect incident light.

In this paper a software package for design of bulk wave acousto-optical (AO) spatial light deflectors is reported. This package consists of a main program and the following modules: a database of acousto-optic materials, a program for coordinate transformation, a multi-layer transducer analysis program with the capability of matching layer, and matching circuit design, an acousto-optic interaction analysis program, and a user friendly interface. The heart of the package is the acousto-optic interaction program based on rigorous coupled wave analysis in anisotropic media. The polarization of input optical beam can be TE, TM, or mixed. The beam can have either uniform or Gaussian intensity profile. The user chooses the bandwidth, central frequency, the laser wavelength and polarization, the preferred AO material, and then the program provides all the geometrical parameters of design and plots the results of its simulation. The program accepts constraints on spatial resolution and transit time, as well. Several examples, both single and multi-frequency problems have been done using this package. An example comparing a result of this package with a previously reported one will be addressed in this paper. At present this package is restricted to single element transducer designs.

The Thin-Film Actuated Mirror Array (TFAMA) is a new reflective type spatial light modulator developed by using the microelectromechanical system technology. The micromachined thin-film piezoelectric actuators are used to control the tilting angle of micromirrors. This paper describes the principle, design, fabrication and the performance of the TFAMA module for high-brightness projection displays. Maximizing the optical performance in terms of the fill factor and the mirror flatness is the main issue of this paper. A hidden actuator design with the two- spacer process provides the highest optical efficiency among the reflection light modulators at the present time. A working projector prototype of 5,000 ANSI lumen is realized with three TFAMA modules with a 1 kW Xenon lamp.

Today, the fabrication of microactuators and micromechanical parts is merely based on IC fabrication technologies. However, the 2D world of microelectronics sets a limit to the 3D micromechanical world. With a new micromachining technology, reshaping, which combines advantages of 2D IC fabrication with the third dimension of the mechanical world, a surface micromachined polycrystalline structure can be deformed to any desired 3D shape. In this work, this technique is employed for the first time to realize 3D actuators, and micro-opto-electro-mechanical systems. In this work, the design, fabrication and characterization of a micromirror are discussed. The structure is reshaped in such a way that the mirror platform, which is placed between two bimorph actuators, is tilted at a desired angle. The experimental results of electro-thermally actuated structure are in good agreement with the numerical results carried out by using IntelliCAD, an FEA tool to design and simulate MEMS. The reshaped micromirror demonstrates how reshaping technology eliminates complicated, silicon area consuming actuators. The fabrication steps of the micromirror are much simpler than those of previously reported device. A barcode scanner system employing reshaped micromirrors and optical filters is proposed as one example of many possible reshaped 3D MOEM Systems.

This paper describes two examples, which include thermal and comb-drive actuators for optical sensor applications. In both examples, numerical simulation was used to provide an optimum design. A 2D finite element modeling (FEM) was used to predict the state of stress and deformation in the MEM cantilever beam and also to analyze the materials and designs so as to minimize the stress state in the structure. The initial processed device showed a small warpage of more than 300 micrometers , which was not acceptable for Rockwell system applications. Using FEM, these devices were optimized to drastically reduce the residual stresses, and resulted in actual fabricated warpage-free structures. Once practical structures were found, parametric 2- and 3-D models were developed to verify mechanical reliability and the final architecture of the MEM device. The second device example was a MEM comb-drive structure. The frequency response of these dynamic structures provide the designer with the minimum detectable signal which can be resolved as well as the deflection of the mass per given acceleration. Therefore, the knowledge of an accurate frequency response is critical for successful design. Accurate FEM modeling provides the coefficients of the second order differential equation which describes mechanical behavior of the accelerometer. These coefficients can be used to create an equivalent circuit model. The model can be simulated in SPICE together with its interface electronics to evaluate the complete sensor performance.

The alignment of optical elements in a Micro-Opto-Electro- Mechanical System, is of prime importance in order to realize a reliable and low loss system. Fabrication errors or temperature changes deteriorate the alignment accuracy. These errors can be compensated with the aid of an active alignment system. The aim of the paper is to investigate an active system in order to align microlenses and fibers. A high lateral precision is required for single mode fiber injection, typically better than 1 micrometers . The alignment along the optical axis is less critical. Our system consists of a microlens placed between one input fiber and one output fiber. The fibers are held in V-grooves and the microlens is mounted on an XY-stage. The lens is fabricated by melting resist technology and subsequent etching in quartz. The mechanical parts are realized by wire electro-discharge machining (wire-EDM). Two piezo-electrical actuators move the flexible bearings of the stage in the X and Y direction. We will present the results obtained with this system and we will discuss its potential.

Evanescent optical fields and photon tunneling junctions can be used to monitor position of an object with an exponential sensitivity given by exp(-x/x₀) where x₀ is the fraction of the photon wavelength. Compared with electron tunneling methods, photon based physical sensors do not suffer from coulombic attractive forces (and backlashes) and tunneling junction deterioration that result in modification of the sensor sensitivity and excess noise, respectively. Experimental results obtained using fiber optic photon tunneling junctions and micromachined Si diaphragms clearly indicate the exponential sensitivity of these sensors. We will present these experimental data and discuss design rules and methodologies for photon tunneling physical sensors and accelerometers.

The application of shape memory alloy (SMA) thin films in optical devices is introduced and explored for the first time. Physical and optical properties of Titanium-Nickel (TiNi) SMA thin films change as these films undergo phase transformation upon heating. An optical beam can be modulated either mechanically using a TiNi actuator or by the changes that occur in TiNi's optical properties upon heating and phase transformation. Reflection coefficient of TiNi films were measured in their so called martensitic (at room temperature) and austenitic (elevated temperature) phases. The reflection coefficient of the austenitic phase were higher than those of the martensitic phase by more than 45% in the wavelength range between 550 - 850 nm. Also, a microfabricated TiNi diaphragm with a 0.26 mm diameter hole was used as a prototype light-valve. The intensity of the transmitted light through the hole was reduced by 10 - 17% when the diaphragm was heated. A novel TiNi light-valve fabricated using silicon micromachining techniques is also proposed and discussed. We present both optical data and structural data obtained using transmission electron microscopies.

Microassembly promises to extend MEMS beyond the confines of silicon micromachining. This paper surveys research in both serial and parallel microassembly. The former extends conventional `pick and place' assembly into the micro- domain, where surface forces play a dominant role. Parallel assembly involves the simultaneous precise organization of an ensemble of micro components. This can be achieved by microstructure transfer between aligned wafers or arrays of binding sites that trap an initially random collection of parts. Binding sites can be micromachined cavities or electrostatic traps; short-range attractive forces and random agitation of the parts serve to fill the sites. Microassembly strategies should furnish reliable mechanical bonds and electrical interconnection between the micropart and the target substrate or subassembly.

This presentation looks first at the opportunity and characteristics of silicon microstructures that make it an enabling technology, followed by examples where the technology has found markets. A summary of the industry characteristics and a comparison and contrast with the traditional electronics industry follows. A profile of successful microstructure applications and future trends leads to insight on how to structure a commercially viable approach. Finally, a summary of the market drivers and requirements and the true cost of ownership provides guidance on markets where a microstructure solution makes sense.

An overview of the key micromachining technologies that enable communications applications for MEMS is presented with a focus on frequency-selective devices. In particular, micromechanical filters are briefly reviewed and key technologies needed to extend their frequencies into the high VHF and UHF ranges are anticipated. Series resistance in interconnect or structural materials is shown to be a common concern for virtually all RF MEMS components, from mechanical vibrating beams, to high-Q inductors and tunable capacitors, to switches and antennas. Environmental parasites--such as feedthrough capacitance, eddy currents, and molecular contaminants--are identified as major performance limiters for RF MEMS. Strategies for eliminating them via combination of monolithic integration and encapsulation packaging are described.