Photonics/Optics

Downsampling Photodetector Array With Windowing

Applications include laser ranging for commercial surveys, and building-to-building optical data links. In a photon counting detector array, each pixel in the array produces an electrical pulse when an incident photon on that pixel is detected. Detection and demodulation of an optical communication signal that modulated the intensity of the optical signal requires counting the number of photon arrivals over a given interval. As the size of photon counting photodetector arrays increases, parallel processing of all the pixels exceeds the resources available in current application-specific integrated circuit (ASIC) and gate array (GA) technology; the desire for a high fill factor in avalanche photodiode (APD) detector arrays also precludes this.

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

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Optical Communications Channel Combiner

NASA has identified deep-space optical communications links as an integral part of a unified space communication network in order to provide data rates in excess of 100 Mb/s. The distances and limited power inherent in a deep-space optical downlink necessitate the use of photon-counting detectors and a powerefficient modulation such as pulse position modulation (PPM). For the output of each photodetector, whether from a separate telescope or a portion of the detection area, a communication receiver estimates a log-likelihood ratio for each PPM slot. To realize the full effective aperture of these receivers, their outputs must be combined prior to information decoding.

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

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Development of Thermal Infrared Sensor To Supplement Operational Land Imager

The application is for the Landsat Data Continuity Mission. The thermal infrared sensor (TIRS) is a quantum well infrared photodetector (QWIP)-based instrument intended to supplement the Operational Land Imager (OLI) for the Landsat Data Continuity Mission (LDCM). The TIRS instrument is a far-infrared imager operating in the pushbroom mode with two IR channels: 10.8 and 12 μm. The focal plane will contain three 640×512 QWIP arrays mounted onto a silicon substrate. The readout integrated circuit (ROIC) addresses each pixel on the QWIP arrays and reads out the pixel value (signal). The ROIC is controlled by the focal plane electronics (FPE) by means of clock signals and bias voltage value. The means of how the FPE is designed to control and interact with the TIRS focal plane assembly (FPA) is the basis for this work.

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Infrared Laser Beam Evaluation Tool

The CoolCard™ II from Pathfinder Research (Lafayette, CO) is a handheld infrared laser beamfinder and beam evaluation instrument. The IR beam-quality evaluation tool can be used with lasers and other IR sources operating from the near-IR to 10-μm wavelengths. Using thermally- stabilized liquid crystal technology, the CoolCard™ senses and resolves the fine spatial character of lasers operating near and beyond 1.7 μm. The beamfinder features a rechargeable, field-replaceable Li-ion battery with capacity sufficient for multi-hour continuous operation.

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Glass Reflectron Lens Process

PHOTONIS USA (Sturbridge, MA) has been awarded a patent for the manufacture of resistive glass tubes with non-linear gradient electrical resistance changes. The patented process creates a solid-piece reflectron lens. Reflectron lenses are used in Timeof- Flight (TOF) mass spectrometers to create an electrostatic field to alter ion flow, providing for a longer flight path and greater resolution. A reflectron lens made with resistive glass provides an assembly replacement for a stacked ring assembly yet provides the same ability to alter ion flow.

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Fiber Laser

The Mentad fiber laser from RPMC Lasers (O’Fallon, MO) is now available at the 1.0μm wavelength. The 4.25 × 2.7 × 0.8" Mentad produces pulse energies up to 50μJ, with pulse widths from 500ps to 1.25μs and rep rates from 5kHz to 2MHz. The laser is also available at 1.5μm. At 1.5μm, the Mentad can produce up to 100μJ of pulse energy. Typical applications for the Mentad include: LIDAR, range finding, telemetry, target ID, 3D and topography scanning, and weather and pollutant detection.

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Infrared Emitters

Opto Diode Corp. (Newbury Park, CA) has introduced three new infrared (IR) emitters. The OD-850W gallium aluminum arsenide (GaAlAs) LED features a wide-emission angle and typical optical output of 40mW. The new device has a peak emission wavelength at 850nm.

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