Photonics/Optics

Wide-Field Optic for Autonomous Acquisition of Laser Link

This system has application in conventional wide-angle imaging such as low-light cockpit imaging, and in long-range motion detection. NASA’s Jet Propulsion Laboratory, Pasadena, California An innovation reported in “Two-Camera Acquisition and Tracking of a Flying Target,” NASA Tech Briefs, Vol. 32, No. 8 (August 2008), p. 20, used a commercial fish-eye lens and an electronic imaging camera for initially locating objects with subsequent handover to an actuated narrow-field camera. But this operated against a dark-sky background. An improved solution involves an optical design based on custom optical components for the wide-field optical system that directly addresses the key limitations in acquiring a laser signal from a moving source such as an aircraft or a spacecraft.

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

Read More >>

Method for Implementing Optical Phase Adjustment

Goddard Space Flight Center, Greenbelt, Maryland A method has been developed to mechanically implement the optical phase shift by adjusting the polarization of the pump and probe beams in an NMOR (nonlinear magneto-optical rotation) magnetometer as the proper phase shift is necessary to induce self-oscillation. This innovation consists of mounting the pump beam on a ring that surrounds the atomic vapor sample. The propagation of the probe beam is perpendicular to that of the pump beam. The probe beam can be considered as defining the axis of a cylinder, while the pump beam is directed radially. The magnetic field to be measured defines a third vector, but it is also taken to lie along the cylinder axis. Both the pump and probe beams are polarized such that their electric field vectors are substantially perpendicular to the magnet field. By rotation of the ring supporting the pump beam, its direction can be varied relative to the plane defined by the probe electric field and the magnetic field to be measured.

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

Read More >>

Multiple-Zone Diffractive Optic Element for Laser Ranging Applications

This technology can be used on unmanned aerial vehicles, or in collision-avoidance and robotic control applications in cars, trains, and ships. Goddard Space Flight Center, Greenbelt, Maryland A diffractive optic element (DOE) can be used as a beam splitter to generate multiple laser beams from a single input laser beam. This technology has been recently used in LRO’s Lunar Orbiter Laser Altimeter (LOLA) instrument to generate five laser beams that measure the lunar topography from a 50-km nominal mapping orbit (see figure). An extension of this approach is to use a multiple-zone DOE to allow a laser altimeter instrument to operate over a wider range of distances. In particular, a multiple-zone DOE could be used for applications that require both mapping and landing on a planetary body. In this case, the laser altimeter operating range would need to extend from several hundred kilometers down to a few meters.

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

Read More >>

Simplified Architecture for Precise Aiming of a Deep-Space Communication Laser Transceiver

New optical transceiver is a combination of innovative technologies. NASA’s Jet Propulsion Laboratory, Pasadena, California The simplified architecture is a minimal system for a deep-space optical communications transceiver. For a deep- space optical communications link the simplest form of the transceiver requires (1) an efficient modulated optical source, (2) a point-ahead mechanism (PAM) to compensate for two-way light travel, (3) an aperture to reduce the divergence of the transmit laser communication signal and also to collect the uplink communication signal, and (4) a receive detector to sense the uplink communication signal. Additional components are introduced to mitigate for spacecraft microvibrations and to improve the pointing accuracy.

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

Read More >>

Two-Photon-Absorption Scheme for Optical Beam Tracking

This approach reduces cost for free-space optical communication receivers. NASA’s Jet Propulsion Laboratory, Pasadena, California A new optical beam tracking approach for free-space optical communication links using two-photon absorption (TPA) in a high-bandgap detector material was demonstrated. This tracking scheme is part of the canonical architecture described in the preceding article. TPA is used to track a long-wavelength transmit laser while direct absorption on the same sensor simultaneously tracks a shorter-wavelength beacon. The TPA responsivity was measured for silicon using a PIN photodiode at a laser beacon wavelength of 1,550 nm. As expected, the responsivity shows a linear dependence with incident power level. The responsivity slope is 4.5 × 10–7 A/W2. Also, optical beam spots from the 1,550-nm laser beacon were characterized on commercial charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) imagers with as little as 13.7 μW of optical power (see figure). This new tracker technology offers an innovative solution to reduce system complexity, improve transmit/receive isolation, improve optical efficiency, improve signal-to-noise ratio (SNR), and reduce cost for free-space optical communications transceivers.

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

Read More >>

On Calculating the Zero-Gravity Surface Figure of a Mirror

As well as gravity reversing between two configurations, mount forces must reverse to within the St. Venant scale.An analysis of the classical method of calculating the zero-gravity surface figure of a mirror from surface-figure measurements in the presence of gravity has led to improved understanding of conditions under which the calculations are valid. In this method, one measures the surface figure in two or more gravity-reversed configurations, then calculates the zero-gravity surface figure as the average of the surface figures determined from these measurements. It is now understood that gravity reversal is not, by itself, sufficient to ensure validity of the calculations: It is also necessary to reverse mounting forces, for which purpose one must ensure that mounting-fixture/mirror contacts are located either at the same places or else sufficiently close to the same places in both gravity-reversed configurations. It is usually not practical to locate the contacts at the same places, raising the question of how close is sufficiently close. The criterion for sufficient closeness is embodied in the St. Venant principle, which, in the present context, translates to a requirement that the distance between corresponding gravity-reversed mounting positions be small in comparison to their distances to the optical surface of the mirror.

Posted in: Photonics, Briefs, Photonics

Read More >>

Fiber-Coupled Planar Light-Wave Circuit for Seed Laser Control in High Spectral Resolution Lidar Systems

The compact, efficient, and reliable design enables use on small aircraft and satellites.Precise laser remote sensing of aerosol extinction and backscatter in the atmosphere requires a high-power, pulsed, frequency doubled Nd:YAG laser that is wavelength-stabilized to a narrow absorption line such as found in iodine vapor. One method for precise wavelength control is to injection seed the Nd:YAG laser with a low-power CW laser that is stabilized by frequency converting a fraction of the beam to 532 nm, and to actively frequency-lock it to an iodine vapor absorption line. While the feasibility of this approach has been demonstrated using bulk optics in NASA Langley’s Airborne High Spectral Resolution Lidar (HSRL) program, an ideal, lower cost solution is to develop an all-waveguide, frequency-locked seed laser in a compact, robust package that will withstand the temperature, shock, and vibration levels associated with airborne and space-based remote sensing platforms.

Posted in: Photonics, Semiconductors & ICs, Briefs, TSP, Photonics

Read More >>

White Papers

Connectors Outperform Fardwiring for Manufacturers and Their Customers
Sponsored by Harting
Measurement of Harmonics using Spectrum Analyzers
Sponsored by Rohde and Schwarz A and D
Sphere Versus 45°/0° Versus Multi-angle: A Discussion Of Industrial Use Cases
Sponsored by x-rite
SpaceClaim in Manufacturing
Sponsored by SpaceClaim
Step on It! Walking for Power
Sponsored by HP
The Self-Driving Car
Sponsored by HP

White Papers Sponsored By: