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Dynamic Pupil Masking for Phasing Telescope Mirror Segments

Piston and tilt adjustments could be performed more efficiently. NASA’s Jet Propulsion Laboratory, Pasadena, California A method that would notably include dynamic pupil masking has been proposed as an enhanced version of a prior method of phasing the segments of a primary telescope mirror. The method would apply, more specifically, to a primary telescope mirror that comprises multiple segments mounted on actuators that can be used to tilt the segments and translate them along the nominal optical axis to affect wavefront control in increments as fine as a fraction of a wavelength of light. An apparatus (see figure) for implementing the proposed method would be denoted a dispersed-fringe-sensor phasing camera system (DPCS).

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

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Pattern-Recognition Algorithm for Locking Laser Frequency

NASA’s Jet Propulsion Laboratory, Pasadena, California A computer program serves as part of a feedback control system that locks the frequency of a laser to one of the spectral peaks of cesium atoms in an optical-absorption cell. The system analyzes a saturation absorption spectrum to find a target peak and commands a laser-frequency-control circuit to minimize an error signal representing the difference between the laser frequency and the target peak. The program implements an algorithm consisting of the following steps:

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Optoelectronic Contract Manufacturing Starts Before Design — Not After

During the 1980s, electronics companies began a two-fold move toward outsourced manufacturing and away from a vertical manufacturing infrastructure to focus on their core competencies. This is evident in the rise of fabless design companies, the rise in electronic packaging companies, and the success of companies focused on system-level assembly. The rise of this new type of manufacturing environment has led to a very nimble, highly complex infrastructure with international capabilities.

Posted in: Features, ptb catchall, Photonics, Articles

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Using Quasiparticle Poisoning To Detect Photons

A mesoscale quantum phenomenon would be exploited to obtain high sensitivity. NASA’s Jet Propulsion Laboratory, Pasadena, California According to a proposal, a phenomenon associated with excitation of quasi- particles in certain superconducting quantum devices would be exploited as a means of detecting photons with exquisite sensitivity. The phenomenon could also be exploited to perform medium-resolution spectroscopy. The proposal was inspired by the observation that Coulomb blockade devices upon which some quantum logic gates are based are extremely sensitive to quasiparticles excited above the superconducting gaps in their leads. The presence of quasiparticles in the leads can be easily detected via the charge states. If quasiparticles could be generated in the leads by absorption of photons, then the devices could be used as very sensitive detectors of electromagnetic radiation over the spectral range from x-rays to submillimeter waves.

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Wavelength-Agile External-Cavity Diode Laser for DWDM

Lyndon B. Johnson Space Center, Houston, Texas A prototype external-cavity diode laser (ECDL) has been developed for communication systems utilizing dense wavelength-division multiplexing (DWDM). This ECDL is an updated version of the ECDL reported in “Wavelength-Agile External-Cavity Diode Laser” (LEW-17090), NASA Tech Briefs, Vol. 25, No. 11 (November 2001), page 14a. To recapitulate: The wavelength-agile ECDL combines the stability of an external-cavity laser with the wavelength agility of a diode laser. Wavelength is modulated by modulating the injection current of the diode-laser gain element. The external cavity is a Littman-Metcalf resonator, in which the zeroth-order output from a diffraction grating is used as the laser output and the first-order-diffracted light is retroreflected by a cavity feedback mirror, which establishes one end of the resonator. The other end of the resonator is the output surface of a Fabry-Perot resonator that constitutes the diode-laser gain element. Wavelength is selected by choosing the angle of the diffracted return beam, as determined by position of the feedback mirror. The present wavelength-agile ECDL is distinguished by design details that enable coverage of all 60 channels, separated by 100-GHz frequency intervals, that are specified in DWDM standards.

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Pattern-Recognition Processor Using Holographic Photopolymer

This processor would operate in real time with high resolution. NASA’s Jet Propulsion Laboratory, Pasadena, California A proposed joint-transform optical correlator (JTOC) would be capable of operating as a real-time pattern-recognition processor. The key correlation-filter reading/writing medium of this JTOC would be an updateable holographic photopolymer. The high-resolution, high-speed characteristics of this photopolymer would enable pattern-recognition processing to occur at a speed three orders of magnitude greater than that of state-of-the-art digital pattern-recognition processors. There are many potential applications in biometric personal identification (e.g., using images of fingerprints and faces) and nondestructive industrial inspection.

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Raman Spectrometer Monitors Multiple Reaction Sites with Doubled Dispersion

Compact f/2.4 design efficiently handles large numbers of optical fibers at the entrance aperture. Headwall Photonics, Fitchburg, Massachusetts Raman spectroscopy has risen to the top of a short list of technologies for identifying substances with high specificity. As a result, Raman spectrometers with high spectral resolution, high spatial resolution, high throughput, and small footprints are in high demand. Utilizing holographic diffraction gratings technology, Headwall Photonics has developed an imaging spectrometer that satisfies these performance demands through a retro-reflective concentric design utilizing the optimized properties of an advanced, highly efficient convex grating (see Figure 1).

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

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