Features

This Month in NASA History

This year, as NASA celebrates its 50th anniversary, we’ll be highlighting technology innovations and important moments in NASA history, leading to our special 50th Anniversary Issue in October.

Posted in: UpFront

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Flexible Silicon Circuits Conform to Complex Shapes

Scientists at the University of Illinois Champaign-Urbana have developed a new form of stretchable silicon integrated circuit that can wrap around complex shapes such as spheres, body parts, and aircraft wings. The circuits can operate during stretching, compressing, folding, and other types of extreme mechanical deformations, without a reduction in electrical performance.

Posted in: UpFront

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Dr. William (Bill) Farrell, Scientist, Lunar Exploration Program

Goddard Space Flight Center, Greenbelt, MD Dr. William Farrell, a scientist with the Lunar Exploration Program at Goddard Space Flight Center, is an expert on the problem of lunar dust and its effects on astronauts and equipment.

Posted in: Who's Who

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Fly-by-Wireless: A Less-Wire and Wireless Revolution for Aerospace Vehicle Architectures

By George Studor, NASA’s Johnson Space Center, Houston, TX Every ounce of weight brought to the lunar surface costs 40 to 60 times that in fuel needed at liftoff from the Earth. Part of that weight penalty is due to wires, but the cost of wires is much more than weight. Wired connectivity drives up the price of design from the beginning: it drives the cost of the many systems and structures; it drives inspection, troubleshooting, maintenance, and upgrade costs; as well as the cost of making system changes. Future vehicles that can reduce the effects and limitations of wires will not be without risk or a lot of work, but the effort has begun.

Posted in: Articles

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Performance of 1mm² Silicon Photomultipliers

A silicon photomultiplier (SPM) is a new type of semiconductor detector that has the potential to replace the photomultiplier tube (PMT) detector in many applications. In common with a PMT detector, the output of an SPM is an easily detectable current pulse for each detected photon and can be used in both photon counting mode and as an analogue (photocurrent) detector. However, the SPM also has a distinct advantage over PMT detectors. The photon-induced current pulse from a PMT varies greatly from photon to photon, due to the statistics of the PMT multiplication process (excess noise). In contrast, the current pulse from an SPM is identical from photon to photon. This gives the SPM a distinct advantage in photon counting applications as it allows the associated electronics to be greatly simplified. Identical pulses also mean that the SPM can resolve the number of photons in weak optical pulses, so-called photon number resolution. This is critical in a number of applications including linear-optics quantum computing.

Posted in: Articles, Features, ptb catchall, Photonics

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Biomedical Imaging Using Ultrashort Laser Pulses

The field of optical microscopy experienced significant gains in resolution and speed following the introduction of lasers. Unfortunately, these gains came at the expense of sample degradation caused by the continuous flux of intense light. Taking advantage of the two-photon absorption process, Webb and Denk implemented a microscope based on the use of near-IR light pulses capable of causing simultaneous multiple fluorophore excitation. Two-photon microscopy is now widely applied in the biomedical imaging field due to the absence of out-of-focus photobleaching and reduced photodamage and fluorescence scattering. These advantages are brought about collectively by the inherent instantaneous peak intensity and narrow focal plane of excitation. Given that peak intensity increases with decreasing laser pulse duration, one would expect extensive use of available ultrashort (sub-10 fs) pulse laser systems in the field of biomedical imaging. However, most two-photon microscopes still use the same pulse duration that Webb and Denk used in 1990 (≈150 fs).

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

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Product of the Month: Fiber-Coupled Solid State Laser

Point Source (Hamble, UK) introduces the iFLEX-Mustang, a fiber-coupled solid-state laser with on-board modulation. Using single-mode and polarization preserving fiber, the iFLEX-Mustang delivers 25mW of power with a polarization extinction ratio of greater than 100:1. With an operating wavelength of 488 or 561nm and output power (from the fiber) of 25mW, the Mustang is ideal for use in bio-medical instrumentation and specialized semiconductor metrology. The unit’s power can be modulated at up to 2MHz, with a rise and fall time of 150ns and a dynamic range of 30dB. The Mustang is stable to better than 2% over four hours, and has noise of less than 0.3% over the frequency range 20Hz to 2MHz. A detachable fiber is included, simplifying installation and field servicing.

Posted in: Products, Products

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