Photonics

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: ptb catchall, Applications, Photonics, Application Briefs

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Compact Packaging of Photonic Millimeter-Wave Receiver

Bulky positioning mechanisms are not needed. John H. Glenn Research Center, Cleveland, Ohio 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: Tech Briefs, ptb catchall, Photonics, Briefs

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Fabrication of Submillimeter Axisymmetric Optical Components

Surfaces of components can be arbitrarily shaped to optimize spectral responses. NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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Mapping Nearby Terrain in 3D by Use of a Grid of Laser Spots

A relatively simple system would utilize triangulation. NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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Wide-Band, High-Quantum-Efficiency Photodetector

This device could detect single photons. NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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Diffractive Combiner of Single-Mode Pump Laser-Diode Beams

Multiple beams can be combined without inducing multifrequency lasing. NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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Narrow-Band WGM Optical Filters With Tunable FSRs

Microwave signals generated by optoelectronic oscillators can be tuned. NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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