Proceedings Volume 3008

Miniaturized Systems with Micro-Optics and Micromechanics II

M. Edward Motamedi, Larry J. Hornbeck, Kristofer S. J. Pister
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Proceedings Volume 3008

Miniaturized Systems with Micro-Optics and Micromechanics II

M. Edward Motamedi, Larry J. Hornbeck, Kristofer S. J. Pister
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 11 April 1997
Contents: 7 Sessions, 41 Papers, 0 Presentations
Conference: Photonics West '97 1997
Volume Number: 3008

Table of Contents

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Table of Contents

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  • MOEM Devices
  • Beam Steering and Micro-optical Scanners
  • Micro-optics Integration I
  • Optical Processing and Control
  • MOEM Processes
  • Micro-optics Integration II
  • MEM Actuator Materials
  • Micro-optics Integration I
MOEM Devices
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MOEM systems in Europe
This is a brief summary of the talk given at Photonics West, San Jose, on 10 February 1997. The description made hereafter of the strategic problematics in Europe in the domain of microsystems results from a free and extensive reading of the literature made available by the EC programs in particular through EUROPRACTICE and NEXUS. What follows expresses personal views and does not reflect any official position. Most of the information material can be found in the mst news journal edited by VDI/VDE-IT. This talk was an attempt to extract the essentials of what is going on in European Microsystem Technologies (MST) from the numerous programs, projects schemes, and initiatives which have been announced, and to position the Opto-Electro-Mechanical Microsystem sin the MST framework.
Micro-opto-electro-mechanical (MOEM) adaptive optic system
This paper discusses the application of MOEM technology to adaptive optics. An experiment is described in which a micromachined mirror array is used in a closed loop adaptive optic demonstration. An interferometer wavefront sensor is used for wavefront sensing. Parallel analog electronics are used for the wavefront reconstruction. Parallel operational amplifiers are used to drive the micromirrors. The actuators utilize a novel silicon design developed by SY Technology, Inc. The actuators have a measured frequency response of 15kHz, and a maximum usable stroke of 4 microns. The entire adaptive optic demonstration has a bandwidth exceeding 10kHz. Measured performance is described. The experiments conducted are designed to explore the feasibility of creating a single chip adaptive optic system, also described in this paper. This chip would combine all on a single VLSI chip aspects of a complete adaptive optics system, wavefront sensing, wavefront reconstruction, and wavefront correction. The wavefront sensing would be accomplished with a novel compact shearing interferometer design. The analog refractive and diffractive micro optics will be fabricated using a new single step analog mask technology. The reconstruction circuit would use an analog resistive grid solver. The resistive grid would be fabricated in polysilicon. The drive circuits and micromirror actuators would use standard CMOS silicon fabrication methods.
Laser aperture integrated with position-sensing detectors
Evan D. Green, Kulwant S. Brar
A laser alignment aperture for automation of laser beam alignment has been realized. The expected system application is to define a straight line by placing apertures integrated with position sensitive photodiodes in the beam path. Any deviation of the incident laser beam from the predetermined path causes it to strike one of the four photodiode quadrants around one of the apertures. The photocurrent signal produced at one of the four detector quadrants, when compared to the photocurrents from the other quadrants provides a measurement of the beam position. Using standard silicon microfabrication and micromachining processes, apertures from 0.5 to 1.3 mm diameter have been fabricated.
Surface micromachined tunable resonant cavity LED using wafer bonding
Gina L. Christenson, Alex T.T. D. Tran, Zuhua Zhu, et al.
Surface micromachining and wafer bonding techniques have been integrated to fabricate a dual-use resonant cavity tunable LED/photodetector operating at 1.5 micrometers . The device has a tuning range of 75 nm, and a spectral linewidth of 4 nm, with an extinction ratio of greater than 20 dB throughout the tuning range. The device has potential applications in WDM networks and optical interconnects due to the small physical size, beam profile, and wafer-scale fabrication and testing possibilities. A GaAs/AlAs distributed Bragg reflector (DBR) is integrated with an InGaAsP strain-compensated multiple quantum well gain medium using wafer bonding. The InGaAsP material with a central wavelength of 1.52 micrometers is grown lattice-matched on an InP substrate. After wafer bonding, the InP substrate is removed, leaving the active layers on the GaAs-based mirror and substrate. The top DBR mirror of the resonant cavity is formed using surface micromachining techniques. The mirror consists of a 4 5 pair S1/S1O2 DBR and a T1/W support and contact layer. These materials are deposited on a sacrificial polymide layer above the InP-based gain medium. The polymide is selectively etched to release the membrane, creating an air gap between the top mirror and the epitaxial layers. When a voltage is applied between these two layers, the membrane is deflected towards the substrates, changing the Fabry-Perot cavity length, and causing a corresponding change in the resonance wavelength of the device. The device functions as a resonant cavity photodetector by reverse biasing the multiple quantum well region. The absorption bandwidth and wavelength running are identical to the emission characteristics of the same device when used as an LED.
Design and fabrication of optoelectronic multichip module prototypes using MEMS fabrication techniques
Seungug Koh, Daniel J. Sadler, Kwang Wook Oh, et al.
This paper describes the design, fabrication, and assembly issues of OE-MSMs using MEMS fabrication techniques by characterizing some of the basic building blocks like micromachined silicon mirrors, GaAs MSM photodiodes. Issues of aligning and bonding discrete components discrete components on OE-MCMs are addressed along with the proposed fabrication and packaging strategies. The CMOS compatible TMAH processes are investigated with results comparable to those obtained from KOH processes. After sputtered aluminum layers are applied, the micromachined silicon mirror reflectivities are further improved with some samples showing reflectivities above 95 percent at wavelengths of 1300 nm and 1500 nm. The results from silicon mirror beam profiling and the minor impacts of packaging processes to silicon mirror I/O coupling efficiencies indicate that the mass fabrication of OE-MCM is technically and economically feasible.
Optical probe for micromachine performance analysis
Fred M. Dickey, Scott C. Holswade, Norman F. Smith, et al.
Understanding the mechanisms that impact the performance of Microelectromechanical Systems (MEMS) is essential to the development of optimized designs and fabrication processes, as well as the qualification of devices for commercial applications. Silicon micromachines include engines that consist of orthogonally oriented linear comb drive actuators mechanically connected to a rotating gear. These gears are as small as 50 micrometers in diameter and can be driven at rotation rates exceeding 300,000 rpm. Optical techniques offer the potential for measuring long term statistical performance data and transient responses needed to optimize designs and manufacturing techniques. We describe the development of Micromachine Optical Probe (MOP) technology for the evaluation of micromachine performance. The MOP approach is based on the detection of optical signals scattered by the gear teeth or other physical structures. We present experimental results obtained with a prototype optical probe and micromachines developed at Sandia National Laboratories.
InP-based micromechanical tunable and selective photodetector for WDM systems
The design and the fabrication of vertical InP-based micro- opto-electro-mechanical devices are reported. These are based on micromachined III-V semiconductor structures realized by selective removal of adapted sacrificial layers in order to produce Fabry-Perot resonant microcavity. Continuous wavelength running of 50nm around 1.55 micrometers for a 15 volt bias actuation has been demonstrated. Resonant peak full width at half maximum of about 10 nm at 1.5 micrometers has been performed on a InP/air gap multilayered interferometric filter. The integration of absorbing layers inside the cavity will allow us to realize resonant cavity enhanced photonic devices with thinner, and therefore faster, photodetector structures with high quantum efficiencies.
Beam Steering and Micro-optical Scanners
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Potential of transmittive micro-optical systems for miniaturized scanners, modulators, and switches
The utilization of micro-optical components in systems for optical beam deflection and modulation offers the possibility for realization switches and scanners. As the required displacement of the micro-optical components for efficient beam manipulation is quite small, high speed actuators with small electrical power consumption can be used. We present a variety of micro-optical configurations and discuss their potential for the creation of different types of miniaturized scanners and switches. The combination of micro-optical components already available and semiclassical piezoelectric actuators leads to new types of switching and modulation systems for a very broad spectrum of applications.
Micromachined microscanners for optical scanning
Meng-Hsiung Kiang, Olav Solgaard, Richard S. Muller, et al.
We present the design and fabrication of surface- micromachined electrostatic-comb driven microscanners that have high angular precision over a large scan angle. When used as resonant scanners, these mirrors have fast scan rates with very low operating power. We use polysilicon microhinges, which allow the micromirrors to be lifted out of the plane of the substrate after processing is completed, to create high-aspect-ratio optical surfaces with dimensions in the hundreds of micrometers s while taking advantage of the planar surface-micromachining processing technology. Microscanners that are capable of high-speed scanning over large scan angles with high precision have been fabricated. Application of these actuated micromirrors in laser barcode scanning and optical-fiber switches have been demonstrated. These single-mirror scanners can be combined to form more complicated microscanners such as a two-mirror, two-axis raster scanner that have a wide range of applications in areas such as medicine, displays, printing, data storage, and communications.
Microactuated mirrors for beam steering
Steven C. Gustafson, Gordon R. Little, David M. Burns, et al.
The design, fabrication, and potential performance of micro- actuated mirrors for beam steering are considered. Micro- actuators are by definition small devices that implement small displacements; they typically function using either electrostatic attraction or thermal expansion and are much smaller and less expensive than voice coil, piezoelectric stack, and related macro-actuators. Mirrors for use with micro-actuators may consist of rigid optically flat plates, continuous deformable membranes of facesheets, or arrays of elements with many possible element shapes, spacings, and displacement patterns. In general, the number of potentially practical micro-actuated mirror designs for beam steering increases as angular range, aperture size, steering speed, optical quality, and optical power requirements decrease.
Designs to improve polysilicon micromirror surface topology
David M. Burns, Victor M. Bright
Many applications for surface micromachined micromirrors require optically flat mirror surfaces. Holographic data storage and optical beam steering for display applications need reflective surfaces free of phase distortion to reduce the signal noise level, minimize cross-talk, and keep the system in focus. Typical micromirror designs may have unintentional embossing on the mirror surface resulting from the top surface conforming to the pattern of underlying layers. The bottom layers may have been shaped to form electrodes to electrostatically move the mirror. The mirror surface may also sag as a result of an imbalance between the stresses in the metal layer and the underlying polysilicon layer. This paper presents a study of the surface of a baseline micromirror, and shows the results of applying smart designs to minimize surface topology defects. The micromirrors presented in this paper were fabricated through the multi-user MEMS processes and categorized with an interferometric microscope.
Two-dimensional miniature optical-scanning sensor with silicon micromachined scanning mirror
Masaaki Ikeda, Hiroshi Goto, Hiromi Totani, et al.
For achieving higher performance and for miniaturizing the size of an optical scanning sensor, raising the scanning angle response, increasing the accuracy of detection of the scanning location independent from the environmental temperature, and miniaturizing an optical-scanning sensor were considered. And the silicon micromachined 2D optical scanner integrated with a piezoresistor for scanning location detection and a photodiode for optical intensity detection was newly designed and fabricated. The obtained results with the fabricated scanner are following. The scanner is capable of scanning a light beam more than 40 degrees 2D. The scanning angle sensitivities are 4.8 deg/V for horizontal direction and 10.5 deg/V for vertical direction. The scanning location detection sensitivity for each horizontal and vertical directions are 21 mV/deg and 26 mV/deg., respectively. The decrease of detection accuracy of scanning location has been reduced to less than 1 percent within +/- 10 degrees C temperature shift. And the photodetector has a photosensitivity of 0.33 A/W which allows the optical-scanning sensor to detect the reflected light intensity from an object which is 200 mm away from the sensor.
Micro-optics Integration I
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Polymer guided-wave integrated optics: an enabling technology for micro-opto-electro-mechanical systems
Lawrence Anthony Hornak, Kolin S. Brown, B. J. Taylor, et al.
Efficient merging of optical, microelectromechanical (MEM) and microelectronic systems offers significant potential for achieving the microoptoelectromechanical (MOEM) system functionality necessary to meet the performance needs of a number of emerging display, sensing, communications, and control applications. Central to realization of this potential will be the development of a set o microoptical components and processes suitable for co-integration with MEMS devices and support microelectronics. The resulting MEMS 'optical toolbox' will provide the generic building blocks with which photonic functions can be achieved within MOEM systems. An extensive set of bulk and surface micromachined microoptical components supporting free-space optical beam manipulation for optical display, scan, and sense functions is currently under investigation by a number of research groups. Integrated waveguide components have ben less developed within the surface micromachined MEMS environment yet offer substantial opportunities for extending MOEM integrated system capability. This paper explores issues confronting the integration of waveguide technologies within the surface micromachined MEMS environment. Specific focus is placed on initial efforts developing processes for guided wave polymer optics cointegration with the multi-user MEMS process service surface micromachining process. Efforts studying the cointegration of polyimide waveguides with MEMS for integrated optical metrology and state feedback applications will be highlighted.
Exact numerical technique for the analysis of Bragg reflectors in integrated optical filters
Kambiz Pashaei Fakhri, Philippe Gerard, Pierre Benech, et al.
We present an exact numerical technique for analyzing Bragg reflectors. Bragg reflectors can be used as narrow-band distributed feedback reflectors that reflect at the center of the grating stopband and transmit at frequencies to either side. THese reflectors can be sued as highly selective pass-band filters. These reflectors can be also used as highly selective pass-band filters. Our structure that is realized by the LEAME consists of microcavities inserted in a waveguide suspended in air. These cavities ar air voids placed periodically in a high-refractive index semiconductor material. Recently Zhang et al. realized a broad-band Bragg reflector by placing a 1D array of air holes in a dielectric waveguide without taking into account the power loss in their simulation. Power loss due to radiation at abrupt discontinuities limits the performance of these microcavities.Unlike the other analytical methods no physical approximations are made throughout the entire analysis, so it may be used to analyze any periodic dielectric structure regardless of the geometry or strong discontinuities. Our exact technique uses the local normal modes of the structure to form a transfer matrix for the whole structure. For this reason our method can be used to evaluate exactly the transmitted, reflected and radiated power. We will present later the result of the numerical simulations for a Bragg reflector with few steps.
Optical displacement measurement using a monolithic Michelson interferometer
Contactless optical displacement measurement has the potential for a variety of industrial and scientific applications. For highly accurate displacement measurements at distances below 1 m, interferometric methods are preferred over most other methods. This is mainly because of the good resolution and the possibility of doing the measurements in real-time. Furthermore, the use of direct bandgap semiconductor materials also enables the fabrication of a compact interferometer-based device which unites all necessary components, including the light emitter, on a single chip. In this paper, a monolithically integrated optical displacement sensor fabricated in the GaAs/AlGaAs material system is reported. This single chip microsystem is configured as a double Michelson interferometer and comprises a distributed Bragg reflector laser, photodetectors, phase shifters and waveguide couplers. In the course of this paper, we will also briefly discuss possible scientific and industrial applications of such devices.
Novel architecture for silicon-based integrated interferometer with phase modulation by elasto-optic effect
As a novelty application of Si-based integrated optics, the preliminary results of realisation of a compact Mach-Zehnder interferometer will be presented. The deposition of a piezoelectric ZnO thin-film transducer on the reftrence arm of the interferometer will allow to transform this optically passive device in a device under an active phase modulation, useful to built a high-resolution microsensing systems with optical heterodyning.
Loss reduction of abrupt waveguide bends using Fabry-Perot cavity for optical interconnects
Jau-Jan Deng, Yang-Tung Huang
A novel low-loss bending structure in dielectric waveguides is proposed. In the proposed structure, an antiresonant Fabry-Perot cavity parallel to the original waveguide is added at the outer side of the bend in order to reduce the bending loss. Based on a simple design rule for the antiresonant cavity, the materials can be flexibly chosen to be adapted to fabrication methods. The beam propagation method is used to verify this low-loss design. The double- bend and curved structures using the same principle for further loss improvement are also presented.
Optical Processing and Control
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Optical transformer and collimator for efficient fiber coupling
M. Edward Motamedi, Haluk O. Sankur, Frederic M. Durville, et al.
Efficient coupling of high power lasers to optical fibers is desired for many applications. An example of these applications is the medical market, where coherent optical power delivered through fibers is used to perform state-of- the-art surgery. We report an efficient method for coupling optical energy from a laser-diode bar to a fiber. This method uses a single surface collimator combined with a two- surface optical transformer. An array of corrector lenses was used to assure that the output of the collimator was appropriately incident on the transformer. Optical efficiency of the collimator, after AR coating, is about 85 percent. The gratin design of the transformer is based on 4- phase level binary optics blazed grating with minimum feature size of 1.5 micrometers . Test results indicate that all the design aspects of our collimator and optical transformer are as expected, and experimental data are well within theoretical expectations. The average tested diffraction efficiency of the optical transformer is as high as 72 percent for one surface. Considering standard 0.8 micrometers process, the efficiency of the transformer for one surface can increase to > 92 percent. To our knowledge, this is the first practical demonstration of the optical transformer concept. These results demonstrate a low-cost and reliable method for efficient coupling of high power laser arrays to fibers for medical and industrial applications.
Optical communication link using micromachined corner cube reflector
Patrick B. Chu, Nanping R. Lo, Erik Berg, et al.
An optical communication link using a micromachined corner cube reflector (CCR) was demonstrated to transmit digital signals over a range of 2 meters by reflecting an interrogating laser from a 5mW laser source. The surface micromachined CCRs are made of 250micrometers square hinged polysilicon plates and have measured reflectance ranging from 34 percent to 77 percent for different mirror designs. LIght reflected by the CCRs has a divergence ranging from 15-35mrad. The CCRs are electrostatically actuated with 10 to 20V. The highest data rate transmitted with a CCR is 1K bps. Theoretical analysis and some dynamic optical test results of the device are presented.
Micro-optical beam transformation system for high-power laser diode bars with efficient brightness conservation
Rolf Goering, Peter Schreiber, Torsten Possner
Most of the potential applications of high power laser diode bars and stacks need special beam transformation systems in order to create a much more symmetric output beam. We present a novel concept for single emitted beam reconfiguration of high power laser diode bars, which uses different types of microoptical components. A very compact and efficient beam shaping system has been built upon the base of this concept, forming a nearly circular output beam with minimum brightness reduction compared to the laser diode output radiation.
Micro-optical modulators and switches for multimode fiber applications
Steffen Gloeckner, Rolf Goering, Torsten Possner, et al.
External modulators and switches for multimode fiber transmission systems are required for aplenty of applications in optical metrology and communication systems. We show that a confocal arrangement of microlens arrays with certain filter elements in the common focal plane of the arrays, which are moved with the help of piezoelectrical actuators, is a very simple and flexible concept to meet the needs of a number of very different applications. The focal length, lens pitch and width of the arrays have to be chosen properly. We discuss which optical elements are required for certain applications. We present experiments for an intensity modulator.
MOEM Processes
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E-beam lithography: an efficient tool for the fabrication of diffractive and micro-optical elements
The fabrication of surface profiles for microoptical and micromechanical devices becomes more and more important. Especially the high accuracy necessary for the realization of the functional components benefits from the use of e-beam lithography, either for the fabrication of tools for optical lithography and replication techniques or for the direct writing of the pattern. After a classification of the pattern and an introduction into the processes for the realization of surface structures we show examples for the basic structure classes as well as for the integration of several properties within one profile resulting in elements with higher complexity.
Fabrication and application of subwavelength gratings
Bernd Schnabel, Ernst-Bernhard Kley
Binary gratings with periods below the wavelength of visible light may be fabricated by e-beam direct writing in a resist layer and then transferred into other materials by ion beam etching. We used a well-adapted e-beam writer 'LION LV1' which allows feature sizes of 100nm and below and arbitrary directions of the grating lines as well as radial, circular or elliptical grating lines. By transfering such gratings into metallic layers polarization effects may be obtained which depend both on the parameters of the gratings and of the metal layer. The dependence of the polarization on grating period and duty cycle was measured for chromium layers with 35nm thickness. By writing concentric circular gratin lines, interesting polarization analyzers may be fabricated. in addition to metal stripe gratings, dielectric subwavelength gratings show interesting properties, too. They may be used for coupling free space light into a planar or rib waveguide with incoupling efficiencies higher than 50 percent. Both for metallic and dielectric gratings, the optical properties strongly depend on an accurate and reproducible fabrication process which, therefore, has to be subject of further research.
Assembling of micro-optical components
Guenther Tittelbach, Ramona Eberhardt, Volker Guyenot
In future most microoptical components will be applied as hybrid integrated systems. The manufacturing of beam shaping optics consisting of two or more microoptical components in a hybrid microsystem places demanding requirements on the assembling process due to the need for extreme positioning accuracy. The basis of the micro-assembly system is a high- precision robot. The robot is used to handle, to grip and to join the components with minimal position deviations. Various vacuum grippers are described. The dispensing of adhesive drops of approximately 5-30 nl volume is an essential part of the task.
Strength of indium phosphide-based microstructures
Staffan Greek, Klas Hjort, Jan-Ake Schweitz, et al.
Microoptoelectromechanical (MOEMS) systems with InP based micromechanics are proposed for devices with wide tuning ranges in the optical wavelengths where InP optoelectronics are normally used. To evaluate if these InP based micromechanical structures may be strong enough the mechanical strengths of surface micromachined epitaxial InP micro beams are evaluated. Reactive ion etching (RIE) with CH4:H2:H2Ar is used to structure the beams. A sacrificial InGaAs layer is below the InP microstructures and selectively etched by HCl:H2O2:H2O in ratios 1:1:10 to release the InP beams. Sublimation of tert-butanol is used to dry the micro structures. The RIE conditions are shown to be of large importance, since the induced surface defects are here the dominant reasons for fracture. Bending strength values up to 3.1 GPa were measured, i.e. much higher than for the strongest construction steel. Weibull statistics show that it is possible to make micromachines for typical MOEMS applications with acceptable loss in yield due to fracture probability, i.e. with a fracture probability of 0.0001 for 100 MPa maximum bending stress.
Optical characterization methods of InP-based micro-opto-electro-mechanical systems
Ronan Le Dantec, Taha Benyattou, Gerard Guillot, et al.
We have studied actuable suspended beams that form vertical optical resonant cavities. They are fabricated by sacrificial layers etching techniques on InP. They can be used as tunable optical filters for telecommunication applications. In this paper, we report optical characterizations of those devices. We have used micro reflectivity and optical profilometer measurements to make those characterizations. We have developed a micro- reflectivity experimental setup which uses the confocal principle. We have shown the deformation of the suspended beams and the variation of the reflectivity response induced by electrostatic actuation of the devices.
Dielectric microfilter arrays for multispectral measuring devices
Marcus Frank, Uwe B. Schallenberg, Norbert Kaiser, et al.
For specified color measuring devices miniaturized dielectric filter arrays have been designed and developed. The manufacturing procedure is based on the combination of coating- and micropatterning processes including the employment of etchstop layers. The spectral properties of a basic filter, fabricated as an unpatterned filter blank, have been modified within small areas by reactive ion etching a defined number edge by edge within a period of 25 micrometers . In this paper design and development of two-color microfilter arrays are described and problems are depicted, arising with the production of multicolor dielectric microfilters. An alternative manufacturing procedure is discussed, making it possible to arrange more than two different interference filters edge by edge.
Micro-optical and optomechanical systems fabricated by the LIGA technique
Juergen Mohr, Jost Goettert, Andre Mueller, et al.
The LIGA process is used to fabricate micro-optical benches which allow to mount hybridically active and passive optical components with very high precision and without active alignment. Moreover, also micro mechanical structures like electro-mechanical actuators are fabricated on the same substrate. To avoid any lateral misalignment al fixing structures in the optical bench are produced in the lithography step. Due to the high precision of x-ray lithography lateral tolerances are in the range of 0.1 to 0.2 micrometers depending on thermal distortions. Thus, optical losses for these components are rather small. The potential of the free space concept based on LIGA technology for the fabrication of devices for optical telecommunication has been demonstrated by a bi-directional transceiver module as well as an optical bypass. In the case of the optical bypass element, a movable mirror is fabricated on the substrate together with the fixing elements. This movable mirror is the end face of an electro-static actuator which allows to move the mirror into the collimated light beam between two fibers and thus, change the direction of the light. For the first prototypes the losses in the beam without mirror are about 1.7 dB, whereas the losses in the deflected beam are about 4.5 dB.
Micro-optic fabrication using one-level gray-tone lithography
Klaus Reimer, Hans Joachim Quenzer, M. Juerss, et al.
This paper reports on a methodology to fabricate arbitrarily shaped structures using technologies common to standard IC manufacturing processes. Particular emphasis is put on the design and use of halftone transmission masks for the lithography step required in the fabrication process of mechanical, optical or electronic components. The algorithms to transfer an initial height profile into a design representation in the common data format GDSII are discussed. This set of data could be used directly by a commercial mask shop. The great data amount of a reticle layout is reduced significantly by a linear working data compaction algorithm. The nonlinear influences of the different process steps on the transfer function are regarded. The specific parameters for the mask making and the resist process are determined. Several components like shaped gratings or lenses are realized in resist up to 10 micrometers thick. In the field of transfering the pattern into a substrate material like silicon, a dry etching process is evaluated.
LIGA tunable spectral filter performance
J. Allen Cox, David C. Dobson, Thomas R. Ohnstein, et al.
Using LIGA techniques, a transmissive diffraction grating device in permalloy with variable, and controllable, grating period has been designed and fabricated for use as a tunable infrared spectral filer. Typical device parameters exhibit parameters exhibit periods approximately 8-30 microns, permalloy grating lines approximately 3 microns wide by 10- 50 microns high. In Ell polarization, the device acts as low pass spectral filter with cutoff wavelength determined by the variable grating period. Recent developments in fabrication of the gratin structure and actuator are reviewed briefly. Emphasis is given to results of recent performance modeling both for thinner and shorter grating walls suitable for shorter wavelength applications and to demonstrate the effects of an incident spherical wave.
Silicon mirror arrays fabricated by using bulk and surface micromachining
Thomas Gessner, Wolfram Doetzel, Detlef Billep, et al.
Recently scanning actuator arrays have developed using metal, e.g. aluminium, or polysilicon as mirror material. Design and technology of micro mirror arrays mad of monocrystalline silicon are discussed in this paper as well as experimental results characterizing the arrays. Micro mirror arrays with up to 1000 simultaneously movable electrostatically operated cells convenient for continuous scanning with frequencies of several hundred Hz up to some kHz will be presented. The technological approaches consist of the use of silicon wet- and dry-etching, wafer bonding and metallization. A novel modified BESOI technology with CMP, wafer bonding with buried refractory metal electrodes and sacrificial layer etching has ben developed and will be discussed. The design process is based on simple analytical calculations of the mechanical behavior, the fluid flow surrounding the movable mirror and the electrostatic field as well as numerical simulations by means of the finite element method and network analysis. Furthermore, some experimental methods to characterize the electro-mechanical behavior of micro mirror arrays are discussed. In order to evaluate theoretical models describing the behavior, the natural frequencies, the damping coefficients and the frequency transfer function are measured. The adaptation of the model parameters leads to more accurate values simulating the behavior.
Method of computer-controlled microlens processing and testing
Sergey A. Rodionov, Vadim P. Veiko, Alexander T. Shakola, et al.
Computer controlled process of microlens manufacturing and testing is described. Lens figuring is made by high energy CO2 laser beam scanning over surface. Testing procedure is realized in the same installation without removal of manufactured lens. Test uses low energy He-Ne laser beam scanning over entrance pupil of lens using the same scanning system as during manufacturing procedure. Testing method is based on principles of Hartmann test but do not use any diaphragm. The least squares method is used to determine coefficients of Zernike polynomial expansion, describing testing lens surface figuring errors.
Micro-optics Integration II
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Photonic crystal fabrication by way of coherent microparticle interaction
Laurence E. Malley, Drew A. Pommet, Michael A. Fiddy
A method for determining steady-state particle density distribution resulting from an incident standing-wave field is discussed. A brief review of photonic crystals relates their established properties and their symmetry along with spectral relationships using 1D eigenvalue equations. Electrostatic interactions between neutral but polarizable particles are derived from Maxwell's equations and the Lorentz force equation. The role of the stress tensor in electromagnetic propagation is discussed. Macroscopic van der Waals forces are described in terms of the Maxwell stress tensor, and equations for the microscopic van der Waals forces between two parallel dipoles are given for in- phase and out-of-phase cases. Spatial distribution of the electric field magnitude for the two cases are illustrated. Possible applications are described.
Fabrication of optical waveguides by the diffusion of Disperse Red 1 dye
Stephanie L. Jones, Richard W. Ridgway, James R. Busch, et al.
A method for fabricating moldable guest-host polymer waveguides by a diffusion process using an ethylene glycol/methanol mixture as the solvent was developed. The change in refractive index to create the guiding layer was obtained by the use of a small quantity of Disperse Red 1 dye added to the solvent mixture. The mixture of the two solvents serves two purposes. First, the ethylene glycol facilitates thorough dissolution of the dye. Secondly, the presence of methanol allows diffusion of the dye into the PMMA to occur more readily. The effects of various diffusion temperatures and mixture concentration levels on the ultimate index of refraction change were investigated. In addition, the number of guided modes was determined for each sample and the optical loss was measured using prism couplers for input and output coupling. Superficially, the waveguide surfaces do not appear to be adversely affected by the solvent mixture and the profile of the diffused dye possesses sufficient uniformity to allow the input beam to be detectable with the unaided eye at a length of at least 5 cm, this value being limited by the physical length of the waveguides fabricated rather than by the optical loses of the waveguide. The waveguides fabricated by this method vary in their properties depending on fabrication parameters, including diffusion time and temperature as well as dye concentration. Those diffused at lower temperatures or for a shorter duration supported fewer modes. The waveguides fabricated support between one and six modes of both TE and TM waves.
New intensity GaAs electro-optic modulator realized by intersecting waveguides
Beniamino Castagnolo, Maria Rizzi, Zhene Xu
An intersecting waveguide modulator which utilizes the carrier injection effects is presented and characterized. Using O+ implantation to render the implanted region electrically inactive, a well confined injection carrier channel is formed. This area can be driven to function as waveguide or as anti-waveguide. A transversal electrode switches the modulator from the on-state to the off-state or vice versa. By the use of carrier induced refractive index modeling and the finite difference beam propagation method simulation, good performance and small injection current of this modulator are predicted.
Electromagnetic near field induced by surface defects in microstructures
Zhi-Yuan Li, Guozhen Yang, Ben-Yuan Gu
An intersecting waveguide modulator which utilizes the carrier injection effects is presented and characterized. Using O+ implantation to render the implanted region electrically inactive, a well confined injection carrier channel is formed. This area can be driven to function as waveguide or as antiwaveguide. A transversal electrode switches the modulator from the On-state to the Off-state or vice versa. By the use of carrier induced refractive index modeling and the finite difference beam propagation method (FD-BPM) simulation, good performance and small injection current ofthis modulator are predicted.
MEM Actuator Materials
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Ferroelectric PZT thin films on Si and SBN substrates
Ratnakar R. Neurgaonkar, Jeffrey G. Nelson, Joey Lin, et al.
The sol-gel technique has been used to produce perovskite PZT thin films on lattice-matched SBN:60 and LaAlO3 substrates. These films were spin-coated and then annealed in the range of 500-700 degrees C in an oxygen atmosphere. Highly grain oriented films showed high polarization and the potential for a large electro-optic response.In all cases, the PZT thin films were highly crystalline, with dielectric constants > 1300. PZT films were also deposited on Pt- metallized Si using the same deposition technique in order to establish the effect of annealing conditions on the formation of pyrochlore phase.
Ferroelectric PbZr1-xTixO3 thin films made by various metalorganic chemical vapor deposition techniques
Tingkai Li, Peter A. Zawadzki, Richard A. Stall, et al.
Ferroelectric films of PbZr1-xT1xO3 (PZT) have been prepared by various MOCVD techniques including bubbler, direct liquid injection, plasma enhanced MOCVD and TurboDisc techniques. The titanium tetraisopropoxide was used as the precursor for titanium source, while lead bis- tetramethylheptadione, zirconium tetrak1s- tetramethylheptadione were used as sources for lead and zirconium respectively. The PZT films were deposited onto Pt/T1/S1O2/S1 wafers and single-crystal sapphire substrates to measure their phase formation, microstructure and ferroelectric properties. It was found that nucleation of PZT perovskite phase started at a deposition temperature over 550 degrees C and grain growth dominated at 650 degrees C or above. The grain size of PbZr05T105O3 thin films increased from 0.04 micrometers to 0.3 micrometers with increasing deposition temperature. The microstructure of the films was found to be dense and homogeneous. The PZT thin films made by MOCVD exhibit excellent ferroelectric properties. Typically the 300 nm thick PZT films with grain size about 0.3 micrometers on Pt electrodes have Pr greater than 20-30 (mu) C/cm2 at 5V, dielectric constant around 1000, low coercive field Ec50-70 kV/cm, low fatigue rate and leakage current 2-6 X 10-7 A/cm2 at 150 kV/cm and room temperature. The microstructure and ferroelectric properties of PZT thin films made by various MOCVD techniques were also investigated.
Ferroelectric SrBi2Ta2O9 thin films made by one- and two-step metalorganic chemical vapor deposition
Tingkai Li, Richard A. Stall, Yongfei Zhu, et al.
Ferroelectric SeB12Ta2O9 (SBT) thin films have been deposited on sapphire, S1 and Pt/T1/SiO2/S1 substrates by using one and two step MOCVD processes. It was found that nucleation of SBT started at a deposition temperature close to 500 degrees C and grain growth dominated at 700 degrees C or above. With increasing deposition temperature, the grain size of SBT thin films increased from 0.01 micrometers to 0.2 micrometers , but surface roughness and porosity of the films also increased. Therefore, in order to obtain dense and homogeneous SBT films that have low surface roughness, the films have to be deposited at a low temperature for nucleation, then be annealed at a higher temperature for grain growth, which is defined as a one-step deposition process. An alternate approach is to use a two-step deposition process. The first step is a nucleation step, to make a very thin nucleation layer of the desired materials or buffer layer at lower temperature. Even thought heterogeneous nucleation is preferred, homogeneous nucleation also takes place because the heterogeneous nucleation can not grow at the low temperature. The second step is a grain growth step: grains will grow from the nucleation layer or buffer layer at higher temperature. In this manner, high quality SBT thin films were obtained. The SBT thin films with grain size about 0.1 micrometers exhibit following properties: thickness: 0.16-0.19 micrometers , 2Pr:7.8-11 4 (mu) C/cm2 at 5V, Ec. 50-65 kV/cm, Ileakage: 8.0-9.5 X 10-9 A/cm2 at 150 kV/cm, dielectric constant 100-200, fatigue rate: 0.94-0.98 after 1010 cycles at 5V. The interface between SBT film and substrate, surface roughness, thickness uniformity, microstructures and ferroelectric properties of SBT thin films were also investigated.
High-resolution Mueller matrix polarimetry of thin film PLZT electro-optic modulators
A thin-film lead-lanthanum-zirconate-titanate (PLZT) electro-optic spatial light modulator has been characterized with the Mueller matrix imaging polarimeter (MMIP). The MMIP is a dual rotating-retarder polarimeter which illuminates a sample with calibrated polarized states and analyzes the existing polarized state over a spatially-resolved image of the sample images of the retardance magnitude and retardance fast axis orientation reveal the relative electric field strengths in the PLZT 9/65/35 material. By measuring Mueller matrix images of the device at several different applied voltages, a quadratic electro-optic coefficient of 2 X 10-16 (m/V)2 was determined in the modulator active regions.
Micro-optics Integration I
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Microjoinery for optomechanical systems
C. Gonzalez, R. J. Welty, Rosemary L. Smith, et al.
A new technology for the fabrication of optical microcomponents is presented. This technology combines a number of standard and new techniques to produce microstructures based scaled down versions of macro joints such as dovetail, dado, etc. and has been coined MicroJoinery. This technique along with the collected 'toolbox' of associated technologies is presented through the fabrication and characterization of two fundamental optical components: and xyz positioning microstages and a 1 x fiber optic switch. Other microstructures and components which demonstrate MicroJoinery are also presented.