Photonic Choke-Joints for Dual-Polarization Waveguides

The joint is constructed from a conductive metal, and requires no maintenance or peripheral equipment to operate.

Photonic choke-joint (PCJ) structures for dual-polarization waveguides have been investigated at NASA's Goddard Space Flight Center for use in device and component packaging. This interface enables the realization of a high-performance, non-contacting waveguide joint without degrading the in-band signal propagation properties. The choke properties of two tiling approaches — symmetric square Cartesian and octagonal quasi-crystal lattices of metallic posts — are explored and optimal PCJ design parameters are presented. For each of these schemes, the experimental results for structures with finite tilings demonstrate near ideal transmission and reflection performance over a full waveguide band.

Posted in: Briefs, Photonics, Electronic equipment, Waveguides, Product development
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Smart Optical Material Characterization System and Method

This technology creates a flexible, unified platform for dynamic smart optical material evaluation.

NASA's Langley Research Center has developed an adaptable and powerful interferometric test platform that uniquely enables multi-parameter evaluation of a wide variety of smart optical materials (SOM). The patent-pending SOM characterization system was created to measure the dynamic optical response of stimuli-responsive (“smart”) optical materials while external physical/electrical/thermal/chemical/pressure/magneto stimuli are applied to the material. Using novel interferometric fringe analysis software and a multi-stimuli-capable SOM test cell, the SOM characterization system enables a wide variety of materials — such as liquid crystals, nonlinear crystals, electro- and thermo-active polymer optics, and magneto- or piezo-driven optics — to be optically characterized for real-time changes in intensity, phase, and polarization. The versatility of the SOM test platform combined with the powerful, efficient, and user-friendly software interface makes it a valuable tool for the research or commercial development of smart materials.

Posted in: Briefs, Photonics, Computer software and hardware, Optics, Materials identification, Smart materials, Test equipment and instrumentation
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Compact Planar Microwave Blocking Filters

Innovators at NASA's Goddard Space Flight Center have designed, fabricated, and characterized absorptive thermal blocking filters for cryogenic microwave applications. The device allows direct integration of the high-frequency signal and microwave readout, and mitigates spurious resonances in the circuit response. This leads to improved electrical performance and a reduction in the required circuit area. The transmission line filter's input characteristic impedance is designed to match 50 ohms and its response has been validated from 0 to 50 GHz. The observed return loss in the 0 to 20 GHz design band is greater than 20 dB and shows graceful degradation with frequency. The filter's response is calculable, repeatable under cryogenic cycling, and is capable of providing an intrinsically broadband matched impedance termination.

Posted in: Briefs, Photonics, Electrical systems, Thermal management, Product development, Insulation
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System and Method for Generating a Frequency-Modulated Linear Laser Waveform

Applications include manufacturing equipment, robotics, surveillance and security, military imaging, and spectroscopy.

NASA's Langley Research Center has made a breakthrough improvement in laser frequency modulation. Frequency modulation technology has been used for surface mapping and measurement in sonar, radar, and time-of-flight laser technologies for decades. Although adequate, the accuracy of distance measurements made by these technologies can be improved by using a high-frequency triangular-waveform laser instead of a sine waveform or lower-frequency radio or microwaves. This new system generates a triangular modulation waveform with improved linearity that makes possible precision laser radar (light detection and ranging [lidar]) for a variety of applications.

Posted in: Briefs, Photonics, Lidar, Performance upgrades
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Systems and Methods for Mirror Mounting with Minimized Distortion

The use of larger, lighter, and more precise space optics requires not only a means of manufacture, but also a means of spacecraft integration and performance verification. Engineers at NASA's Goddard Space Flight Center (GSFC) have demonstrated a process capable of producing a high-precision, mounted, lightweight mirror, and have validated its on-orbit figure. This effort included the design of a mount capable of surviving the launch environment of a sounding rocket, as well as a mounting process that did not introduce performance-degrading figure distortion. Additionally, analysis techniques were developed and adapted to address the challenges in measuring an optic that exceeds its figure specification under the strain of its own weight.

Posted in: Briefs, Photonics, Mirrors, Optics, Mountings, Durability, Lightweighting
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Improved Approach to Exoplanet Coronagraphy

Visible nulling coronagraphy and interferometry requires that the wavefront errors be held to unprecedented precision in the presence of environmental disturbances. A Null Diversity algorithm is used to first attain the precision, but it does not execute at high enough temporal bandwidth to hold the precision for long periods of time (hours). The environmental changes, mostly vibration and jitter with some thermal drift, can be rapidly varying and thus require a fast control algorithm. To perform rapid control, an algorithm, based upon a series of approximations, has been developed and simulated at NASA Goddard Space Flight Center for the sensing and control, in closed loop, of extremely precise wave-front errors in an interferometer. It operates over the range of ~5 nanometers rms down to <100 picometers rms in closed loop at high bandwidth (~20 Hz) and is used to hold (i.e. maintain) the requisite wavefront error.

Posted in: Briefs, Photonics, Mathematical models, Lasers, Vibration
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Apparatus and Method for a Light Direction Sensor

This invention, developed at NASA's Goddard Space Flight Center, was originally conceived as a high-accuracy, high-sensitivity, bi-axial Sun angle sensor, but has also been proposed for applications involving the general field of precisely measuring the direction in which light travels toward the sensor. It has applications in spacecraft navigation, formation flying in space, space beacons, and automotive collision avoidance.

Posted in: Briefs, Photonics, Measurements, Sensors and actuators, Sun and solar
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Apparatus and Method for Creating a Photonic Densely Accumulated Ray-Point

NASA's Langley Research Center has discovered a new approach to achieving a laser focal point size much smaller than the wavelength of light used, and smaller than that obtained using conventional micro zone plate lenses. The Photonic Densely Accumulated Ray-poinT (DART) technology relies on phase contrast along with interference phenomena, with or without the use of a micro zone plate lens. Coupled with the extremely small spot size, the technology also provides very high laser energy density at the pseudo focal point surrounded by destructive interference, thereby enabling a range of potential useful applications such as laser processing, lithography, nanofabrication, and optical data storage.

Posted in: Briefs, Photonics, Lasers, Waveguides, Refractory materials
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Optical Fiber Sensors vs. Conventional Electrical Strain Gauges for Infrastructure Monitoring Applications

Public infrastructure, including bridges, pipelines, tunnels, foundations, roadways, dams, etc., is subject to factors that can degrade it or lead to malfunctions. These structural problems can be the result of deterioration, improper construction methods, seismic activity, nearby construction work, etc. Although electrical strain gauges have long been used for monitoring structural changes, they sometimes lack the durability and integrity necessary to provide accurate, actionable information over extended periods. The applications in this white paper demonstrate how optical fiber sensors can offer a variety of economic and performance advantages.

Posted in: White Papers, Fiber Optics, Optics, Sensors
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Laser Diode Modules

BEA Lasers (Elk Grove Village, IL) has introduced two new low-profile additions to their rugged MIL Series of laser diode modules. The new MIL RA Model features a right angle, and the new MIL Compact Model features a straight housing. Both new models utilize a low profile 3/8” rugged laser housing, fitted with a M12 connector, 2 meter long PVC jacketed cable, and integrated power supply. The optional sensor-style bracket, or multi-adjustable “LB” bracket, completes the laser system. The new MIL Series laser diode modules are offered with standard 515nm (green) or standard 635nm (red), with 1mW or 5mW.

Posted in: Products, Products, Lasers & Laser Systems
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