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Algorithm for Estimating PRC Wavefront Errors from Shack-Hartmann Camera Images

Phase retrieval is used for the calibration and the fine-alignment of an optical system. NASA’s Jet Propulsion Laboratory, Pasadena, California Phase retrieval (PR) and Shack-Hartmann Sensor (SHS) are the two preferred methods of image-based wavefront sensing widely used in various optical testbeds, adaptive optical systems, and ground- and space-based telescopes. They are used to recover the phase information of an optical system from defocused point source images (PR) and focused point source or extended scene images (SHS). For example, the Terrestrial Planet Finder Coronagraph’s (TPF-C’s) High-Contrast Imaging Testbed (HCIT) uses a PR camera (PRC) to estimate, and subsequently correct, the phase error at the exit pupil of this optical system. Several other test-beds at JPL were, and will be, equipped with both a PRC and a Shack-Hartmann camera (SHC).

Posted in: Briefs, TSP, Cameras, Optics, Sensors

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Photo-Thermo-Refractive Glass Co-Doped with Luminescent Agents for All-Solid-State Microchip Lasers

Goddard Space Flight Center, Greenbelt, Maryland A proposed solid-state technology possesses photosensitivity that enables volume hologram recording and a high efficiency of luminescence, enabling stimulated emission. These features were used to record volume Bragg gratings and to demonstrate lasing under laser diode pumping for the same volume of glass. Moreover, a combination of dopants provides extremely wide luminescence bands, which enables both wideband optical processing and extremely short laser pulse generation. It is important that the whole design be incorporated in a single, monolithic piece of glass that excludes the opportunity for misalignment and sensitivity to vibrations. If developed, the compactness and reliability of such laser devices would find wide use in space or aeronautical applications.

Posted in: Briefs, TSP, Lasers & Laser Systems, Optics

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Monolithic Dual Telescope for Compact Biaxial Lidar

Goddard Space Flight Center, Greenbelt, Maryland A document discusses the Ultra Compact Cloud Physics Lidar, a biaxial lidar with a narrow receiver field of view. It requires tight optical alignment between the transmitter and receiver paths while flying on various aircraft over various temperatures and in the presence of vibration. To achieve optical crossover as close to the lidar as possible, the transmit and receive telescopes must be built very closely to each other.

Posted in: Articles, Briefs, TSP, Tech Briefs, Photonics

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Passive Aerosol Cloud Suite

High-accuracy polarization measurements can be made with high angular density across full images. Goddard Space Flight Center, Greenbelt, Maryland The Passive Aerosol Cloud Suite (PACS) is an imaging polarimeter that employs wide field-of-view (FOV) optics to obtain a highly accurate polarimetric signal across an image with hyperangle, multiangle views. PACS is designed to measure the array of parameters necessary to retrieve aerosol and cloud microphysical characteristics. The final goal of PACS is a flight model able to compete for a position on the Aerosol-Cloud-Ecology (ACE) Decadal Survey mission or other space-based platforms, but adaptations of the basic technology to airborne and ground-based applications are anticipated.

Posted in: Articles, Briefs, TSP, Tech Briefs, Optics, Photonics

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V-Assembly Dual-Head Efficiency Resonator (VADER) Laser Transmitter

The combined features form a unit with new performance levels. A complete demonstration breadboard unit for advanced development as a high-TRL (technology readiness level) system has been constructed and characterized. Infusion of several new component technologies, such as ceramic:YAG material and high-power laser diode arrays (LDAs), combined with a proprietary minimal part count architecture, has resulted in dramatic performance gains. The proprietary dual-head configuration employs a pair of side-pumped laser slabs, optically in series in the cavity, but at opposing polarization orientations. This promises tremendous power range scalability, simplified and symmetrical thermal lens control, unprecedented stored energy extraction efficiency, and inherent diffraction limited TEM00 beam quality.

Posted in: Briefs, TSP, Tech Briefs, Photonics

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Twin Head Efficient Oscillator Development for the ACE Multi- Beam Lidar and 3D-Winds

This technology is applicable to atmospheric lidar, Doppler wind measurements, interplanetary laser communications, and materials processing. The Twin Head Efficient Oscillator (THEO) concept uses a pair of smaller, identical laser pump modules, oriented to remove asymmetrical thermo-optical effects typical in single-slab lasers such as HOMER (High Output Maximum Efficiency Resonator), MLA (Mercury Laser Altimeter), LOLA Lunar Orbiter Laser Altimeter, and GLAS (Geoscience Laser Altimeter), while simultaneously increasing efficiency and lifetime. This creates 100+ mJ pulses in an oscillator-only design, with reduced risk of optical damage, record efficiency, high stability, long life, and high TEM00 beam quality typical of much smaller rod-based cavities. Near-field-beam quality is critical to efficient second harmonic generation (SHG 532 nm), which is typically poor in slab-based Nd:YAG lasers.

Posted in: Briefs, TSP, Photonics

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Planetary Polarization Nephelometer

Instrument provides more detailed information on aerosols encountered in a planetary environment. Aerosols in planetary atmospheres have a significant impact on the energy balance of the planets, yet are often poorly characterized. An in situ instrument was developed that would provide more diagnostic information on the nature of aerosols it encountered if deployed on a planetary descent probe. Previous probe instruments only measured intensity phase functions, but much particle ambiguity remains with only this information. Adding the polarization phase function greatly reduces particle characteristic ambiguities, but also adds more challenges in designing a measurement approach. Laboratory instrumentation to measure intensity and polarization phase functions have existed since the early 1970s, but these instruments employed quarter-wave plates and Pockels cells to modulate the illuminating beam and the scattered light to isolate the intensity and polarization phase functions. Both of these components are unstable except under tightly controlled thermal conditions. This solution avoids the use of thermally sensitive components such as quarter- wave plates or Pockels cells, and avoids requiring the detectors to be placed around the sensing volume.

Posted in: Briefs, TSP, Photonics

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