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QC Lasers Improve Hazardous Gas Monitoring

The measurement of gases associated with industrial processing/emissions monitoring has become increasingly important as the need to improve efficiencies in process control has increased, and legislation governing emissions has come into force. Gases including NOx, SOx, CO2, CO, NH3, and H2O commonly are used to assess processes such as combustion and quenching, while many fall under emissions legislation resulting from the Kyoto agreement.

Posted in: Features, ptb catchall, Photonics, Motion Control, Articles

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LUTs: Take Control of Your Imaging Application

It is hard to see how machine-vision camera manufacturers produce decent-quality products at reasonable prices. The multi-megapixel sensors at the heart of current machine-vision cameras are among the largest of VLSI (very-large-scale integration) semiconductor chips, and it is almost impossible to make them with the pixel-to-pixel uniformity required for high-precision imaging applications. Without some way of compensating for manufacturing variations across a given image sensor, many otherwise acceptable chips would have to be discarded. That would drastically reduce manufacturing yields and drive sensor-chip prices far beyond levels acceptable for many applications.

Posted in: Features, ptb catchall, Photonics, Articles

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Water Jets and Lasers Cut Through Electronic Industry’s Problems

Semiconductor manufacturers need the flexibility of a wafer-cutting machine that supports various wafer sizes and cuts them without the mechanical and thermal damage often seen with traditional cutting methods, including the mechanical stress that occurs with conventional sawing, or the contamination and/or ablated material caused by laser cutting. Employing a dicing process that makes the wafers less prone to breakage would allow manufacturers to introduce thinner wafers into the production line, thereby increasing the number of functions on a given device. A machine that cuts lasers without a heat-affected zone would also offer efficiency advantages to manufacturers.

Posted in: ptb catchall, Applications, Photonics, Application Briefs

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Full-Duplex Digital Communication on a Single Laser Beam

The laser beam would be transmitted with one modulation and retroreflected with another modulation. Goddard Space Flight Center, Greenbelt, Maryland A proposed free-space optical communication system would operate in a full-duplex mode, using a single constant-power laser beam for transmission and reception of binary signals at both ends of the free-space optical path. The system was conceived for two-way data communication between a ground station and a spacecraft in a low orbit around the Earth. It has been estimated that in this application, a data rate of 10 kb/s could be achieved at a ground-station-to-spacecraft distance of 320 km, using a laser power of only 100 mW. The basic system concept is also applicable to terrestrial free-space optical communications.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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Stabilizing Microwave Frequency of a Photonic Oscillator

Microwave frequency is stabilized by stabilizing optical frequency to an atomic transition. NASA’s Jet Propulsion Laboratory, Pasadena, California A scheme for stabilizing the frequency of a microwave signal is proposed that exploits the operational characteristics of a coupled optoelectronic oscillator (COEO) and related optoelectronic equipment. An essential element in the scheme is a fiber mode-locked laser (MLL), the optical frequency of which is locked to an atomic transition. In this scheme, the optical frequency stability of the mode-locked laser is transferred to that of the microwave in the same device. Relative to prior schemes for using wideband optical frequency comb to stabilize microwave signals, this scheme is simpler and lends itself more readily to implementation in relatively compact, rugged equipment. The anticipated development of small, low-power, lightweight, highly stable microwave oscillators based on this scheme would afford great benefits in communication, navigation, metrology, and fundamental sciences.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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Microwave Oscillators Based on Nonlinear WGM Resonators

Optical signals are phase-modulated with spectrally pure microwave signals. NASA’s Jet Propulsion Laboratory, Pasadena, California Optical oscillators that exploit resonantly enhanced four-wave mixing in nonlinear whispering-gallery-mode (WGM) resonators are under investigation for potential utility as low-power, ultra-miniature sources of stable, spectrally pure microwave signals. There are numerous potential uses for such oscillators in radar systems, communication systems, and scientific instrumentation.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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Fiber-Optic Gratings for Lidar Measurements of Water Vapor

These are highly selective, lightweight, tunable optical filters. Langley Research Center, Hampton, Virginia Narrow-band filters in the form of phase-shifted Fabry-Perot Bragg gratings incorporated into optical fibers are being developed for differential-absorption lidar (DIAL) instruments used to measure concentrations of atmospheric water vapor. The basic idea is to measure the relative amounts of pulsed laser light scattered from the atmosphere at two nearly equal wavelengths, one of which coincides with an absorption spectral peak of water molecules and the other corresponding to no water vapor absorption. As part of the DIAL measurement process, the scattered light is made to pass through a filter on the way to a photodetector. Omitting other details of DIAL for the sake of brevity, what is required of the filter is to provide a stop band that:

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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