A ten element piston micromirror array has been used to produce a single irradiation spot in the far-field of a ten element laser diode array operating in the fundamental out- of-phase supermode and to steer the far-field irradiance pattern. A strong single lobe was obtained for several different laser injection currents. The produced lobe with full width at half maximum of 0.167 degree(s) was narrower than the original far-field lobes. Steering of the single lobe to 12 separate spots over a 0.807 degree(s) range was demonstrated.

This paper describes a study to characterize the performance of surface micromachined electrostatic actuators, with a brief introduction to some MEMS (microelectromechanical systems) mirrors developed at BU incorporating these actuators. Fixed-fixed actuators were extensively tested to determine suitability for optical applications, and specifically for an adaptive optics imagining system. The critical issues relating to device performance, namely yield (indicating robustness and process reliability), position repeatability, precision and frequency response, were quantified in the research effort described here. The study demonstrated 95% device yield, 10 nm position repeatability (99% confidence levels), and greater than 66 kHz frequency bandwidth.

In this work, bulk-micromachined {111}-oriented silicon mirrors at 54.7 degree(s) have been fabricated in 20 wt% KOH solution at various temperatures and characterized with single mode fibers (10/125 and 5/125). In fabricating the mirrors, the etch rate of the (100) silicon surface was widely changed from 5.3 micrometers /hr to 73 micrometers /hr as the processing temperatures were varied from 40 degree(s)C to 80 degree(s)C. In spite of the tremendous variation of etch rate, the measured reflectivities of the mirrors showed fairly stable values of 63.7 - 58% at 1330 nm and 55.4 - 57.7% at 1550 nm respectively. This paper describes the silicon mirror processing conditions, measured reflectivities, reflected beam profiles, and a prototype integrated optical I/O coupler with the realized mirrors. The results obtained from this work show that optical I/O couplers with 54.7 degree(s) mirrors on conventional (100)-oriented silicon wafers are feasible, envisaging a synchronized optical clock distribution system as well as a distributed remote optical sensing system with low manufacturing cost.

A novel process for fabrication of torsional micro-mirrors with large dimensions (300 X 240 micrometers and 150 X 120 micrometers ) is presented. The mirrors consist of a sputtered aluminum film on a layer of supporting oxide mounted on fully suspended single crystal silicon grids. The grids have an aspect ratio of 7:1 in order to provide a stiff backbone and to ensure flatness of the mirror surface. The mirrors thus do not bend due to the internal stresses. A new idea of actuation of torsional structures is also presented in this paper. Vertical near-comb type actuators were fabricated to drive the torsional structures.

Micromirror arrays have been designed, fabricated, and tested that can steer coherent beams and that can simultaneously implement continuous phase control for beam shaping or aberration correction. A typical micromirror consists of a polysilicon plate (metalized for reflection) that is less than 100 microns in maximum dimension. Each micromirror is suspended a few microns above a polysilicon electrode by flexure hinges, and potentials of less than 50 volts applied to the electrodes displace the micromirrors over continuous ranges. Applications for arrays of these micromirrors include adaptive optics, active optical interconnections, and laser radar and communications.

Low-cost linear arrays of deflectable micromirrors using a CMOS process to define both on-chip circuitry and the mirror structure are presented. The mirrors consist of the second CMOS metallization deposited in two successive passes in order to establish a thick metal layer for the stiff mirror plate as well as a thin one for the flexible hinges. The mirrors are released by sacrificial aluminum and oxide etching. Supercritical point drying is performed in order to avoid sticking of the mirrors to the substrate. The mirrors are electrostatically deflected by biasing the address electrodes implanted into the substrate underneath the mirror plate. Full angular deflection of 4.8 degree(s) of a 30 X 40 micrometers ² plate is achieved with a driving voltage of 12 V. On-chip circuitry adjacent to each mirror allows to address the pixels by 5 V data pulses. The reflectivity of the aluminum surface for wavelength between 400 and 700 nm was measured to be 83 - 89%. The mirror surface was further characterized using Auger spectroscopy showing that no optically relevant surface modification occur during post- processing. The surface rms roughness measured by atomic force microscopy is in the order of 25 nm.

Microoptical components, such as diffractive and refractive microlenses, micromirrors, beam splitter and beam combining have recently received considerable attention in the optics R&D centers and finally in the manufacturing community. This achievement is due to MEM technology that demonstrated major improvements in overall performance/cost of optical systems while offering the possibility of relatively rapid transition to products for military, industrial and consumer markets. Because of these technology advances, an industrial infrastructure is rapidly becoming established to provide combining microoptical components and MEM-based microactuators for on-chip optical processing. Optical systems that once were considered to be impractical due to the limitations of bulk optics can now easily be designed and fabricated with all required optical paths, signal conditioning, and electronic controls, integrated on a single chip. On-chip optical processing will enhance the performance of devices such as focal plane optical concentrator, smart actuators, color separation, beam shaping, FDDI switch, digital micromirror devices (DMDs), and miniature optical scanners. In this paper we review advances in microoptical components developed at Rockwell Science Center. We also review the potential of on-chip optical processing and recent achievement of free-space integrated optics and microoptical bench components developed at UCLA, and DMDs developed at Texas Instruments.

The fabrication and testing of optomechanical structure which can be used for microwave phase conjugation is described. It consists of the metal-coated dielectric elongated beams 1 mm X 100 micrometers X 10 micrometers suspended by nonconductive torsional springs attached to a microwave transparent frame. Standard photolithography techniques combined with dry XeF₂ etching yield hundred of rotating elements on a single 4' silicon wafer. Rotation of single elements, in a polarized electromagnetic field at 15 GHz, was measured and found to be in a good agreement with theory. This first experimental implementation of combining the concept of nonlinear microwave devices and microelectromechanical systems demonstrates the potential of an entirely new class of devices.

A novel precision wavelength monitor comprising 3D microlenses and rotatable gratings has been demonstrated on a single chip of Si using free-space micro-optical bench (FSMOB) technique. Batch-fabricated by surface- micromachining, the integrable wavelength monitor is potentially low cost, light weight, and small volume, and can be directly incorporated into the packages of active semiconductor optoelectronic sources and detectors. All the micro-optical elements on the FSMOB have been `pre-aligned' during the layout of the photomasks. A 1.3 micrometers distributed feedback (DFB) laser has been integrated with this micro- wavelength-meter on the Si substrate using a self-aligned hybrid-integration scheme. A laser-power-independent linear response has been obtained over the entire thermal tuning range of the DFB laser (1.2 nm). The wavelength reading can potentially by fed back to control and stabilize the wavelength of the DFB laser for wavelength-division multiplexed optical communication systems. It is also very useful for spectroscopy applications.

A new remote optical fiber sensor is presented for the detection of carbon dioxide by molecular absorption in the near infrared corresponding to fundamental mode v₃ equals 2349 cm^-1 (4.257 micrometers ). To overcome this problem of the strong attenuation signal of optical fibers in the infrared, the opto power supply, technique is used which changes the working wavelength from 4.3 micrometers to 860 nm and permits the use of standard 50/125 multimode optical fibers. The simulation of absorption has been obtained by modeling the carbon dioxide absorption spectrum. The relative absorption versus the partial pressure of carbon dioxide have been compared to different theoretical models. The establishment of the calibration curves indicate that the sensor detects partial pressures greater than 100 (mu) bar with a minimal error margin of 100 (mu) bar, which is acceptable considering the future use of the device. The sensor was designed to monitor carbon dioxide concentrations in enriched greenhouses.

Various on-axis and off-axis Fresnel zone lenses with different focal lengths and of different apertures were fabricated in quartz glass by means of microstructuring techniques. The kinoform profile of the diffractive optical elements was approximated by a staircase-like profile having a number of discrete phase levels. Dynamic, that is electrically switchable, lenses have been realized by filling the structured surface with liquid crystal. By applying an AC-voltage the elements can be switched from the state of a `focusing lens' to that of a `transparent glass- plate'. The optical properties of the lenses as well as the switching behavior were studied. Experimental measurements will be compared with theoretical results.

Micro mechanical parts and optical parts are fabricated through ultra precision cutting technique. The precision cutting technique has been considered to be inappropriate for micro parts fabrication of the micrometer order. Our ultra precision cutting technique with sub-micrometer cutting depth made it possible to fabricate 3D micro mechanical parts and micro optical parts. Following micro mechanical parts are fabricated: 10 micrometer shaft by lathe machining, 100 micrometer screw with 20 micrometer pitch thread, and 50 micrometer thickness lever made by stainless steel. Also it was able to fabricate micro optical parts such as holographic optical element with sawtooth cross section and pitch of 3 micrometer. The fabrication was carried out with newly developed ultra precision machine tool with X, Y, Z linear axis and one rotational axis using single crystalline diamond cutting tool. Those linear axis are controlled through hologram scale with 1 nm resolution. The fabrication process by precision cutting has proved to be faster and more precise compared to the lithography and etching method.

To control the third dimension of micro mechanical structures, new materials have to be designed. Unfortunately, increased manufacturability results generally in degraded mechanical and electrical characteristics. The paper is presenting a detailed analysis of p+ silicon as a mechanical material for microresonators and of the low temperature dielectrics used in electrostatic microactuators. All the relevant parameters of p+ silicon are experimentally determined and process recommendations allowing improved quality are formulated. Charge injection and trapping in low temperature dielectrics are analyzed and their impact on the behavior of the electrostatic actuators evaluated.

A micromachined silicon Fabry-Perot interferometric sensor is demonstrated as an optical chemical sensor. This sensor is based on the combined nature of the amplifying and tuning characteristics of the Fabry-Perot microcavity structure and the doping effect of polymer films such as Poly(3- dodecylthiophene) (P3DDT) upon exposure to an oxidizer, in this case, iodine. The fabricated Fabry-Perot chemical sensors show reversible sensing behavior with a maximum change in transmitted optical intensity of 60%. Significant improvement of the sensing performance is obtained from the Fabry-Perot microcavity structure compared to a simple planar single membrane structure, which indicates the resonant effect of the Fabry-Perot cavity on the chemical sensor. The measured sensing characteristics suggest that the change in absorptance of P3DDT polymer inside the microcavity plays a major role, while the deflection of a microcavity membrane by the P3DDT polymer-induced surface tension gives tunability of the sensor to maximize the amplification of output response by adjusting the Fabry- Perot microcavity gap spacing.

Smart MEMS (MicroElectroMechanical Systems) in the form of integrated sensors and actuators offer significant potential for many rotorcraft applications. Sensing of flex beam deflection and acceleration, ice formation and deicing are major candidate areas where smart conformal MEMS based sensors can be exploited by the rotorcraft community. The major technical barrier of the present day smart structures technology is the need for wired communication between sensors and actuators in the rotating system and controllers, data storage units, and cockpit avionics. Many proposed sensors and actuators are commonly distributed either along the blade length or, in the active flap devices, out near the 75% blade radial station. Also they are not conformal to the airfoil shape of the rotor blades. The communication between rotating and fixed systems is typically accomplished using complex slip ring assemblies transferring electronic information down through the rotor shaft. Although advances have been made in wired communication, these complex assemblies are essentially similar to test hardware and present numerous reliability and maintainability limitations when implemented on a production scale. Considering these limitations, development of a wireless means of communication through a new generation of conformal sensors with built-in antenna, akin to telemetry, could have a dramatic beneficial payoff for rotorcraft applications.

A novel method to detect the convolution interlaced minimum for recognizing and tracing the moving target is proposed in this paper. A diffraction device, which can divide an incidence light into 33 X 33 arrays evenly is designed and fabricated. With two 33 X 33 diffraction devices, a dual channel optical real-time processor is built for parallel performing the recognition and tracing of the moving target. Some measures for compensating scale and rotation distortion for moving recognition are provided. The experimental results show that: (1) The 33 X 33 diffraction device has a good diffraction efficiency, 62.5%. (2) The moving target can be recognized parallelly by one step of operation. (3) The scale and rotation distortion of the moving target recognition is insensible. The change of rotation angle to be allowed in moving target recognition is from -25 degree(s) to +25 degree(s).

We propose a wavelength-insensitive optical TE-TM polarization mode converter using twist nematic liquid crystal cell for multi-mode or single-mode fiber communication systems application. Based on the simple and widely used TNLC cell structure, the optical converter has the potential advantages such as inexpensive, simple fabrication processes, and easy mass production. The low crosstalk of -28.3 dB is obtained.

Transmissive single crystal AMLCD light valves have recently drawn much attention for application in flat panel displays. The active matrix circuits are fabricated on SIMOX wafers and then transferred to glass. Circuit transfer consists in bonding a CMOS processed SIMOX wafer to a Pyrex glass substrate, thinning the SIMOX wafer and opening the contact pads. The pixel electrodes are made in polysilicon to allow standard CMOS processing. This paper discusses the transparency of the poly electrode and evaluates the potential of anodic bonding and adhesive bonding for circuit transfer. A major challenge for anodic bonding is the protection of the device dielectrics against the high voltages applied during bonding. A test chip was designed to investigate different ways of circumventing breakdown of the dielectrics. A method for adhesive bonding is discussed that assures good uniformity of the thickness of the epoxy layer and avoids the inclusion of air bubbles. It is demonstrated that the epoxies are resistant to the chemicals used for thinning the silicon substrate.

Prompted by the successful experimental control of concavity of the field emitter profile, simulations on the effect of shape change and cone-side curvature on the field strength of the emitter were carried out. The dependency of field strength on the cone angle or the curvature angle is found to be approximately linear with 5.77 X 10⁴ V/cm/degree. On the other hand, the dependency on the curvature angle (curvature radius) is approximately 4.98 X 10⁴ V/cm/degree which is slightly lower than that of the straight cone angle variation but the average field intensity is about 1.6% higher than that of the pyramidal type. These results indicate that the cone-side curvature angle has a more pronounced effect on the strength of the electrical field than the cone angle. Hence a precise control of cone shape is an effective method of obtaining high electric fields. Optimal shapes of the field emitter can be achieved using appropriate anisotropic, followed by isotropic, etching techniques.

Micromachine technologies based on IC-compatible micromachining have advantages denoted by three `M's'. Miniaturization is the most popular but Multiplicity, which means the batch fabrication capability of many complicated elements, and Microelectronics to control motions or to add different functions such as the optical function are equally important. This paper deals with the application of micromachine technologies to micro optical devices. A basic concept making the best use of the advantages is proposed. Recent examples of optical microelectromechanical systems are reviewed.

MEMS as a technology base is coming ofage, butas in any vital process growing pains occur. Commercializing MEMS is simultaneously viewed asagonizingly slow by many ofits promoters and lightingly quick by many companies whose products are beingreplaced with MEMS based substitutes. This effort ties current efforts in market analysis, technology evaluations, competency based strategy in an effort to understand the pace ofMEMS commercialization.