Photonics

Four-Pass Coupler for Laser-Diode-Pumped Solid-State Laser

A smaller laser slab can be made to perform comparably to a larger one. Goddard Space Flight Center, Greenbelt, Maryland A four-pass optical coupler affords increased (in comparison with related prior two-pass optical couplers) utilization of light generated by a laser diode in side pumping of a solid-state laser slab. The original application for which this coupler was conceived involves a neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal slab, which, when pumped by a row of laser diodes at a wavelength of 809 nm, lases at a wavelength of 1,064 nm.

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

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Varying the Divergence of Multiple Parallel Laser Beams

Lenses mode-matched to the laser beams would be moved axially within an afocal optical subassembly. NASA’s Jet Propulsion Laboratory, Pasadena, California A provision for controlled variation of the divergence of a laser beam or of multiple parallel laser beams has been incorporated into the design of a conceptual free-space optical-communication station from which the transmitted laser beam(s) would be launched via a telescope. The original purpose to be served by this provision was to enable optimization, under various atmospheric optical conditions, of the divergence of a laser beam or beams transmitted from a ground station to a spacecraft. Beyond the original purpose, the underlying design concept could be beneficial for terrestrial free-space laser communication, ranging, and scientific instrumentation applications in which there are requirements to vary the divergences of laser beams.

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Low-Resolution Raman-Spectroscopy Combustion Thermometry

This method offers advantages over related prior Raman-spectroscopy-based methods. John H. Glenn Research Center, Cleveland, Ohio A method of optical thermometry, now undergoing development, involves low-resolution measurement of the spectrum of spontaneous Raman scattering (SRS) from N2 and O2 molecules. The method is especially suitable for measuring temperatures in high-pressure combustion environments that contain N2, O2, or N2/O2 mixtures (including air).

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Going Green in the Workplace with LEDs

In August 2007, Cree’s management made a bold decision to replace the existing fluorescent lighting technology at its Durham, NC facility with new energy-saving, environmentally friendly LED lighting technology. The group started with the company’s headquarters building, but eventually plans to replace more than 7,000 existing fluorescent light fixtures covering more than 800,000 square feet campus-wide. Phase one replaced 200 existing fixtures in 7,000 square feet of space in the visitor lobby, waiting areas and conference rooms. All the exterior parking lot lighting was also converted from high-pressure sodium to LED lighting. Both parts of phase one had to be completed by early November 2007, just 3 months later.

Posted in: Features, ptb catchall, Photonics, Articles

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Precision Prism Manufacturing — Art or Science?

Prisms are used in countless optical systems — from the pair of binoculars in your closet to cutting edge targeting systems to retroreflectors on the Moon. In modern, high-end optical systems, precision optics may be required that push the envelope of manufacturability within given cost constraints. Prisms are an integral component in many of these systems and often require manual fabrication in small quantities; however, they save space, mounting time, and materials, presenting opportunities as well as challenges for optical system designers.

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

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Multichannel Monitor-Stabilizer for Injection-Locked Lasers

NASA’s Jet Propulsion Laboratory, Pasadena, California Temp Tracker and Temp Tracker 12 ch (single-channel and 12-channel versions) programs are designed for use with an atomic gravity gradiometer. They support the stable operation of the injection-locked slave laser(s) in an autonomous regime. Due to changes of environmental conditions and aging, slave lasers tend to drift from the locking range and need to be relocked. This program checks the injection-locking range for each slave laser and re-centers them with respect to the master lasers, if needed. The master laser is assumed to be locked at an absorption line of Cs.

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Self-Quenching Single-Photon Detector

The detector has applications in nuclear physics instruments, spectroscopy, night-vision devices, and biological instrumentation. NASA’s Jet Propulsion Laboratory, Pasadena, California The self-quenching single-photon detector exhibits unique avalanching behaviors. It can automatically quench each of the Geiger mode avalanche events occurring inside the detector, can maintain the capability over a broad bias range, and can output explicit pulses with virtually constant and high value gain.

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