The confluence of the rapidly expanding sensor, computation, and telecommunication industries has allowed for a new instrument concept: the Sensor Web. A Sensor Web consists of intra-communicating, spatially-distributed sensor pods that are deployed to monitor and explore environments. It is capable of automated reasoning for it can perform intelligent autonomous operations in uncertain environments, respond to changing environmental conditions, and carry out automated diagnosis and recovery. Sensor Webs could have as much an impact on the uses of sensors as the Internet did on the uses of computers. Sensor Webs are often confused with distributed sensors or sensor networks. The unique feature of the Sensor Web is that information gathered by one pod is shared and used by other pods. In contrast, sensor networks merely gather data and information gathered by a particular pod on such a network does not influence the behavior of another pod. Thus, sensor networks collect data while Sensor Webs can react and modify their behavior on the basis of the collected data. This paper will outline the potential of the Sensor Web concept and describe the Jet Propulsion Laboratory Sensor Webs Project. In particular, a prototype Sensor Web deployed at the Huntington Botanical Gardens will be discussed.
The design and on-going fabrication of an opto-electro- mechanical microsystem that acts as a four-function optical fiber switch will be presented. The four functions of the 2x2 optical switch include 1) Normal mode, where channel A and channel B pass light straight through, 2) Loopback mode, where light originating in channel A is detected in the B leg, 3) Monitor A mode, where a probe pulse is inserted into the channel B and any reflections are detected in the A leg, and 4) Monitor B mode, the compliment of 3) above. High spatial frequency gratings etched in fused silica configure the light beams through free-space substrate-mode propagation. The design for an OTDR-mode transmission grating that normally passes light from an incidence angle of 45 degrees within the silica substrate as well as passes light from a normal incidence straight through the silica will be discussed. A miniature commercial drive motor, positioned with LIGA alignment plates, rotates the optical grating disk into one of the four implemented function positions. The impact of required tolerances and packaging limitations on the optics, LIGA alignment plates, and the complete microsystem will be presented.
Multivariate Optical Computing (MOC) devices have the potential of greatly simplifying as well as reducing the cost of applying the mathematics of multivariate regression to problems of chemical analysis in the real world. These devices utilize special optical interference coatings known as multivariate optical elements (MOEs) that are encoded with pre-determined spectroscopic patterns to selectively quantify a chemical species of interest in the presence of other interfering species. A T-format prototype of the first optical computing device is presented utilizing a multilayer MOE consisting of alternating layers of two metal oxide films (Nb2O5 and SiO2) on a BK-7 glass substrate. The device was tested by using it to quantify copper uroporphyrin in a quaternary mixture consisting of uroporphyrin (freebase), tin uroporphyrin, nickel uroporphyrin, and copper uroporphyrin. A standard error of prediction (SEP) of 0.86(mu) M was obtained for copper uroporphyrin.
The development of integrated isolators is critical to the functional integration of optics within OEM devices and systems. Bulk isolators have proven to be the most important components in many fiber optic systems due to their ability to protect light sources from back-reflected light. Such reflections are created at each component interface, inhomogeneity, or other perturbation in the path of the light. This paper reviews the operation of and current work in integrated isolators. Several methods for fabricating monolithically integrated magneto-optical isolators are discussed, including the fabrication of garnets, magnets, and cladding/buffer layers. Garnets are traditionally grown by liquid phase epitaxy (LPE) at temperatures and environments that are not friendly to semiconductors or other common substrates. More importantly, LPE requires epitaxial growth, which dictates garnet substrates and therefore hybrid integration techniques. We have used metallorganic chemical vapor deposition (MOCVD), sputtering, and metallorganic chemical liquid deposition (MOCLD) to deposit single-phase yttrium iron garnet (YIG). A variety of substrates were used, including MgO and SiO2 which are promising buffer layer materials. The chemical, structural, and optical properties of the resulting films are discussed. We have also used a variety of sputtering techniques to integrate permanent magnet films with semiconductor processing. These magnets are sufficient for biasing the magneto-optical element. The chemical, structural and magnetic properties of these materials, as well as total integration will be discussed.
This paper gives the status of theoretical and experimental efforts at JPL in the development of environmentally robust (Radiation Hard and radiation Tolerant), ultra-low power, high performance CMOS active pixel sensor (APS) imagers for start tracker/imager applications. The work explores the effect of imager performance on star position accuracy, specifically examining the performance of JPL designed APS imagers. Accuracy is estimated as a function of star magnitude for a nominal star tracker optical design. Using these APS sensors, which have wide dynamic range and no blooming, simultaneous imaging of widely differing star magnitudes during the same observation is possible. It is shown that prototype Rad Hard APS imagers meet many next generation, star tracker/imager mission performance requirements when operated at reduced temperatures. These imagers also provide excellent performance at cryogenic operating temperatures appropriate to some anticipate flight missions. APS imagers with their high level of integration, on-chip timing and control, ultra-low power, and environmental robustness are excellent candidates for NASA's earth observing, interplanetary and deep space exploration missions.
The advances in the design and fabrication of microlaser arrays, photodetectors and free-space optical interconnection elements have driven the creation of ever more real world demonstrator systems. In this paper we review the progress made to date on two separate demonstrator projects which have been assembled at Heriot- Watt University. We shall describe some of the enabling technologies used in the creation of these systems and outline the potential for scaling the architectures described up to sizes where the computational advantages of the optics-in-computing paradigm become highly attractive.
Liquid phase deposition of sol-gel method derived hybrid glass materials is utilized for fabrication of UV light deformable thin films. The hybrid glass material undergoes a surface-relief deformation when exposed to UV light. The observed deformation phenomenon is in the form of a physical expansion of the exposed areas. The maximum deformation when the material was patterned as a sinusoidal grating was 643 nm. The hybrid glass material features an index of refraction of 1.52, rms surface roughness of 2.25 +/- 0.83 nm after processing, and extinction coefficients of 1.2 10-3 micrometers -1 and 0.47 10-3 micrometers -1 at wavelengths of 633 nm and 1550 nm, respectively.
Recent interest in optical sensors, especially optical biosensors, has led to the introduction of commercially available instrumentation and sensor schemes for label free, real time monitoring of intermolecular interactions. One of the promising optical structure is the grating coupler planar waveguide sensor, where high precision surface relief grating is used and a low cost manufacturing is needed. A practical method to mass-produce gratings with limited lateral dimension is to emboss master grating into a sol-gel waveguide film. With proper optimization of the sol-gel process, a wide time window is available to perform embossing and highly reproducible, cost effective grating structures can be replicated. In our practice SiO2, TiO2, SiO2/TiO2, Ta2O5 and a mixture of these sol-gel thin films are proved to be good candidates for low optical loss waveguide materials in which grating with 2400 line/mm periodicity could be directly embossed. The relatively wide time window for optimal embossing opens the possibility to develop grating structures with more than one grating. Producing multiple gratings separated laterally and/or vertically from each other is demonstrated.
The several production methods of paper processing chain can be used, by analogy, to generate novel ideas for production of optics and electronics. Paper processing is a very fast reel-to-reel process: In the beginning of the paper web production the process is running at the speed of over thousand meters per minute and the web width can be 10 meters, and still at the later stages the speed is several hundreds of meters per minute with the web width of a couple of meters. There are several potential reel-to-reel production methods like embossing, printing, laminating and different kinds of vacuum coating, for example evaporation and sputtering. End products are complex multi-layer composite structures. The benefits from this analogy for optics and electronics would be ideas for ultra fast production, paper-like disposable and recyclable products and the integration of optics and electronics into ordinary things like books, wallpapers, tissue papers and packages. Two experiments are presented to demonstrate the possibilities. In the first experiment optical patterns are embossed directly on paper. In the second one conductive polymers are printed on paper and plastic webs. In future, a wide network of cooperation will be needed to realize all the opportunities.
We present the design and fabrication of miniaturized light sources for micro-optical systems using organic light emitting diodes (OLEDs). These devices can be integrated on a micro-optical table (MOT) using various backplanes. Acceptable angular uniformity of emitted radiance, and a brightness of more than 30,000 cd/m2 can be readily achieved with OLEDs having areas ranging from 0.0004 cm2 to 0.0363 cm2.
The transient and steady state performance of organic light- emitting devices (OLEDs) has been investigated with a view towards suitability for pulse sources. The rise and fall times of the electroluminescence of the different structures and materials were afforded special attention. The tested devices cover single and multi-layer structures with different layer thicknesses. Both molecular and polymeric- based devices were tested. Molecular materials used in the OLEDs were N, N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) as a hole transporter, tris-(8-hydroxyquinolate) aluminum (Alq3) as an electron transporter/emitter and 4,7-diphenyl-1,10-phenanthroline (BCP) as a hole blocking material. Poly)2-methoxy, 5-(2'-ethyl-hexoxy)-1,4- phenylene-vinylene) (MEH-PPV) and poly(3,4- ethylenedioxythiophene)/poly(styrene) (PEDOT/PSS) were the polymeric materials used in the devices. The effect of the driving voltage on the response time and the current density in transients was under investigation. In addition, changes in the response time were studied, when the bias voltage was applied.
We have used non-sequential ray tracing as a simulation tool to model micro-optical systems. Ray tracing can be used to model micro-optical systems as long as the wave nature of the light is not dominant. Non-sequential ray tracing takes inherently into account the aberrations of the optical system and enables the modeling of scattering and stray light effects. We have used measured scattering properties of a hybrid-glass lens material to model scattering in an example imaging micro-optical system. We have also used non-sequential ray tracing to model a straight and a bent light-guide that can be used as chemical sensors. Modeling estimates the amount of light going through the optical system to the detector and shows the paths of the rays leaking out from the system.
The development of optical MEMS or MOEMS devices is strongly driven by the requirements of high date transfer in telecommunications and data transmission. To realize the required high data rates with low loss, EMV-sensitivity, cross-talk, and reflections optical MEMS devices were developed. In this paper a short overview on the technological and commercial visions on these fields is given. Furthermore the most important technological approaches to make optical MEMS are summarized and some devices are mentioned. But in order to realize complete devices the packaging and interconnection requirements have to be early incorporated into the design process. This is pointed out and some packaging approaches are discussed. Moreover the important field of optical interconnections is illuminated and a very promising way to integrate polymer waveguides into a PCB is presented.
The rapid advancement of electro-optical components and micro-mechanical devices has led to increased functionality in decreasing package sizes. In particular, the development of massively parallel arrays of optical sources such as Vertical Cavity Surface Emitting Lasers (VCSEL) and innovative micro-opto-electro-mechanical systems (MOEMS) has opened the door for new possibilities. Recently, there has been a drive toward integration of the sensing, processing and actuation functions in a single package for fully integrated performance. One area which can benefit from this research is real time, spectroscopic analysis of biological and chemical samples. Numerous situations require a compact, self-contained bio/chemometric system for rapid, low cost spectral analysis or monitoring. To fully realize this potential, further component development and integration issues must be addressed. This paper will present the status of the VCSEL and MOEMS programs at the Institute and initial integration activities. The VCSELs are based on multiple quantum well Ga/As/InGaAs and GaAs/AlGaAs architectures with monolithic, epitaxially grown distributed Bragg reflectors. The VCSEL arrays have 6-15 micron apertures, 100 micron pitch and a mA threshold current. In parallel, the MOEMS program is focused on the development of active, reconfigurable diffractive and reflective arrays whose surface topology can be changed in real time. These MOEMS arrays can be sued to redirect light for flexible interrogation of samples. The combination of these two technologies offers a unique opportunity for fully functional systems on a chip.
Single stage thin film coolers based on thermoelectric and thermionic cooling in p-type InGaAsP superlattice structures have been fabricated. Devices with different sizes and at various ambient temperatures have been characterized. Experimental results showed 0.5 degree centigrade cooling below the ambient temperature at 25C. This cooling over 1 4mu2m thick superlattice barrier corresponds to cooling power densities on the order of 200 W/cm2. The device cools by a factor of two better at higher temperatures (70C). This is due to the reduction of the superlattice thermal conductivity and the broadening of the electronic distribution function at higher temperatures. 150x150 micrometers 2 devices provide largest cooling at room temperature while the optimum device size shrinks as the temperature increases. Simulations results that take into account finite thermal resistance of the InP substrate, the effect of the contact resistance, heat generation in the wire-bonds and metallic pads on top of the device predict accurately the optimum cooling of these micro refrigerators. By eliminating the major parasitic sources of heating (Joule heating in the substrate, heat conduction through the side contact and reducing the contact resistance to 5x7-7 ohm-cm2) simulations show that, ultimately, one can achieve 15 degree(s)C cooling (10's of kW/cm2 cooling power) with single stage p-InGaAsP thin film coolers.
Since micro robot has merits on small size and flexible movements, it could be used under many situations. A lot of novel designs of micro-robot have been developed recently. However, as miniaturizing the size of the micro-robot, the number of its sensor gets restricted. Then the information from the detectors becomes lack. This makes the micro robot difficult to acquire its status. A micro robot tracing a line has been designed in our lab. With the help of optoelectronic detection and logical algorithm, the micro robot could follow a black line printed on the white ground exactly. The micro robot's intelligence is realized through the program in its microprocessor. The technical details of the micro robot are as follows: dimensions: 30mm*25mm*35**; velocity: 60mm/s.
We present a brief overview of a promising switching technology based on Silica on Silicon thermo-optic integrated circuits. This is basically a 2D solid-state optical device capable of non-blocking switching operation. Except of its excellent performance (insertion loss<5dB, switching time<2ms...), the switch enables additional important build-in functionalities. It enables single-to- single channel switching and single-to-multiple channel multicasting/broadcasting. In addition, it has the capability of channel weighting and variable output power control (attenuation), for instance, to equalize signal levels and compensate for unbalanced different optical input powers, or to equalize unbalanced EDFA gain curve. We examine the market segments appropriate for the switch size and technology, followed by a discussion of the basic features of the technology. The discussion is focused on important requirements from the switch and the technology (e.g., insertion loss, power consumption, channel isolation, extinction ratio, switching time, and heat dissipation). The mechanical design is also considered. It must take into account integration of optical fiber, optical planar wafer, analog electronics and digital microprocessor controls, embedded software, and heating power dissipation. The Lynx Photon.8x8 switch is compared to competing technologies, in terms of typical market performance requirements.