Photonics/Optics

Fiber-Optic Strain Gauge With High Resolution And Update Rate

Changes in strain are correlated with changes in speckle patterns.

An improved fiber-optic strain gauge is capable of measuring strains in the approximate range of 0 to 50 microstrains with a resolution of 0.1 microstrain. (To some extent, the resolution of the strain gauge can be tailored and may be extensible to 0.01 microstrain.) The total cost of the hardware components of this strain gauge is less than $100 at 2006 prices. In comparison with prior strain gauges capable of measurement of such low strains, this strain gauge is more accurate, more economical, and more robust, and it operates at a higher update rate. Strain gauges like this one are useful mainly for measuring small strains (including those associated with vibrations) in such structures as rocket test stands, buildings, oilrigs, bridges, and dams. The technology was inspired by the need to measure very small strains on structures supporting liquid oxygen tanks, as a way to measure accurately mass of liquid oxygen during rocket engine testing.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Finite element analysis, Fiber optics, Test equipment and instrumentation
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Mini CW Lasers Enable Next-Generation Bioinstrumentation

During the past few years, low-cost, continuous-wave (CW) lasers have helped advance a wide range of life and health science applications such as cell sorting, DNA sequencing, confocal microscopy, micro array readers, hematology, and flow cytometry. The bioinstrumentation market continues to evolve, and as it matures, it continues to follow the same trends inherent to the semiconductor and telecommunications markets. Like their counterparts in those other markets, manufacturers of benchtop instruments are looking for robust, cost-effective solutions. They want smaller footprints so that they can decrease the size of their solutions. At the same time, they want to consolidate their supply chain by focusing on proven suppliers that can provide a complete spectrum of wavelengths.

Posted in: Articles, Features, ptb catchall, Photonics, Downsizing, Lasers, Biological sciences, Medical equipment and supplies, Supply chain management, Test equipment and instrumentation
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FPGAs Yield Virtual Laser Valves for Microfluidics

In today’s “micro world,” complex electrical systems, including analog and digital components, can fit on integrated circuits smaller than a fingernail. Microfluidics, a subset of microelectro-mechanical systems (MEMS) technology, is emerging as a new technical niche within microelectronics with widespread application in the health, chemical, and food industries.

Posted in: Application Briefs, Applications, ptb catchall, Photonics, Integrated circuits, Lasers, Microelectromechanical devices, Medical, health, and wellness, Valves
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Compact Packaging of Photonic Millimeter-Wave Receiver

Bulky positioning mechanisms are not needed.

A carrier structure made from a single silicon substrate is the basis of a compact, lightweight, relatively inexpensive package that holds the main optical/electronic coupling components of a photonic millimeter-wave receiver based on a lithium niobate resonator disk. The design of the package is simple and provides for precise relative placement of optical components, eliminating the need for complex, bulky positioning mechanisms like those commonly used to align optical components to optimize focus and coupling. Although a prototype of the package was fabricated as a discrete unit, the design is amenable to integration of the package into a larger photonic and/or electronic receiver system.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Lasers, Optics, Packaging
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Fabrication of Submillimeter Axisymmetric Optical Components

Surfaces of components can be arbitrarily shaped to optimize spectral responses.

It is now possible to fashion transparent crystalline materials into axisymmetric optical components having diameters ranging from hundreds down to tens of micrometers, whereas previously, the smallest attainable diameter was 500 μm. A major step in the fabrication process that makes this possible can be characterized as diamond turning or computer numerically controlled machining on an ultrahigh-precision lathe. This process affords the flexibility to make arbitrary axisymmetric shapes that have various degrees of complexity: examples include a flat disk or a torus supported by a cylinder (see figure), or multiple closely axially spaced disks or tori supported by a cylinder. Such optical components are intended mainly for use as whispering-gallery-mode optical resonators in diverse actual and potential applications, including wavelength filtering, modulation, photonic generation and detection of microwaves, and research in quantum electrodynamics and quantum optics.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Optics, Computer integrated manufacturing, Fabrication, Turning, Parts
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Mapping Nearby Terrain in 3D by Use of a Grid of Laser Spots

A relatively simple system would utilize triangulation.

A proposed optoelectronic system, to be mounted aboard an exploratory robotic vehicle, would be used to generate a three-dimensional (3D) map of nearby terrain and obstacles for purposes of navigating the vehicle across the terrain and avoiding the obstacles. Like some other systems that have been, variously, developed and proposed to perform similar functions, this system would include (1) a light source that would project a known pattern of bright spots onto the terrain, (2) an electronic camera that would be laterally offset from the light source by a known baseline distance, (3) circuitry to digitize the output of the camera during imaging of the light spots, and (4) a computer that would calculate the 3D coordinates of the illuminated spots from their positions in the images by triangulation.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Cartography, Computer software and hardware, Lasers, Navigation and guidance systems, Terrain, Robotics
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Wide-Band, High-Quantum-Efficiency Photodetector

This device could detect single photons.

A design has been proposed for a photodetector that would exhibit a high quantum efficiency (as much as 90 percent) over a wide wavelength band, which would typically be centered at a wavelength of 1.55 μm. This and similar photodetectors would afford a capability for detecting single photons — a capability that is needed for research in quantum optics as well as for the practical development of secure optical communication systems for distribution of quantum cryptographic keys.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Design processes, Cryptography, Optics, Sensors and actuators, Wireless communication systems
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Diffractive Combiner of Single-Mode Pump Laser-Diode Beams

Multiple beams can be combined without inducing multifrequency lasing.

An optical beam combiner now under development would make it possible to use the outputs of multiple single-mode laser diodes to pump a neodymium: yttrium aluminum garnet (Nd:YAG) non-planar ring oscillator (NPRO) laser while ensuring that the laser operates at only a single desired frequency. Heretofore, an Nd:YAG NPRO like the present one has been pumped by a single multimode laser-diode beam delivered via an optical fiber. It would be desirable to use multiple pump laser diodes to increase reliability beyond that obtainable from a single pump laser diode. However, as explained below, simplistically coupling multiple multimode laser-diode beams through a fiber-optic combiner would entail a significant reduction in coupling efficiency, and lasing would occur at one or more other frequencies in addition to the single desired frequency.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Fiber optics, Lasers, Waveguides
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Narrow-Band WGM Optical Filters With Tunable FSRs

Microwave signals generated by optoelectronic oscillators can be tuned.

Optical resonators of the whispering-gallery-mode (WGM) type featuring DC-tunable free spectral ranges (FSRs) have been demonstrated. Previously, the FSRs of WGM optical resonators were determined solely by the resonator geometries and materials: hence, the FSR of such a resonator could be tailored by design, but once the resonator was constructed, its FSR was fixed. By making the FSR tunable, one makes it possible to adjust, during operation, the frequency of a microwave signal generated by an optoelectronic oscillator in which an WGM optical resonator is utilized as a narrow-band filter.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Mirrors, Calibration, Lasers, Performance upgrades
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Digital Beam Deflectors Based Partly on Liquid Crystals

Laser beams are switched to different directions, without using solid moving parts.

A digital beam deflector based partly on liquid crystals has been demonstrated as a prototype of a class of optical beam-steering devices that contain no mechanical actuators or solid moving parts. Such beam-steering devices could be useful in a variety of applications, including free-space optical communications, switching in fiber-optic communications, general optical switching, and optical scanning. Liquid crystals are of special interest as active materials in nonmechanical beam steerers and deflectors because of their structural flexibility, low operating voltages, and the relatively low costs of fabrication of devices that contain them. Recent advances in synthesis of liquid-crystal materials and design of the nematic-liquid-crystal cells have resulted in significant improvements in properties (e.g., short response times and birefringence) that are important for effective beam steering.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Fiber optics, Optics, Switches, Wireless communication systems
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