Dr. G. Lawrence Carr Profile

Dr. G. Lawrence Carr

Physicist at Brookhaven National Lab

SPIE Involvement:

Author

Proceedings Article | 26 September 2013 Paper

Calibrating apodizer fabrication techniques for high-contrast coronagraphs on segmented and monolithic space telescopes

Anand Sivaramakrishnan, Alexandra Greenbaum, G. Lawrence Carr, Randy Smith, Xiaoxiang Xi, Neil Zimmerman

Proceedings Volume 8860, 88600W (2013) https://doi.org/10.1117/12.2024091

KEYWORDS: Synchrotrons, Calibration, Coronagraphy, Fourier transforms, Glasses, Gemini Planet Imager, Mirrors, Light sources, Space telescopes, Apodization

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High contrast imaging can use pupil apodizers to suppress diffracted starlight from a bright source in order to observe its environs. Metallic half-tone dot transmissive apodizers were developed for the Gemini Planet Imager (GPI) and ESO SPHERE coronagraphs for use in the near-IR. Dot sizes on the scale of the wavelength of the light often result in unexpected variations in the optical transmission vs. superficial dot density relation. We measured 5 and 10 micron half-tone microdot screens' transmissions between 550 -1050 nm to prepare to fabricate apodizations that mitigate diffraction by segments gaps and spiders on future large space telescopes. We utilized slow test beams (f/40, f/80) to estimate the on-axis (far-field, or zero-order) transmission of test patches using a Fourier Transform Spectrograph on Beamline U10B at Brookhaven National Laboratory's National Synchrotron Light Source (BNL NSLS). We also modified our previous GPI IR characterization hardware and methods for this experiment. Our measurements show an internal consistency of 0.1% in transmission, a factor of 5 better than our near-IR GPI work on the NSLS U4IR beamline. The systematics of the set-up appeared to limit the absolute calibration for our f/40 data on the 50-patch, maximum Optical Density 3 (OD3), sample. Credible measurements of transmissions down to about 3% transmission were achieved for this sample. Future work on apodizers for obstructed and segmented primary mirror coronagraphs will require configurations that mimic the intended diffractive configurations closely in order to tune apodizer fabrication to any particular application, and measure chromatic effects in representative diffractive regimes. Further experimental refinements are needed to measure the densest test patches which possess transmissions less than a few percent. The new NSLS-II should provide much greater spectral stability of its synchrotron beam, which will improve measurement accuracy and reduce systematics.

Proceedings Article | 21 July 2010 Paper

Gemini Planet Imager coronagraph testbed results

Anand Sivaramakrishnan, Rémi Soummer, Ben Oppenheimer, G. Lawrence Carr, Jacob Mey, Doug Brenner, Charles Mandeville, Neil Zimmerman, Bruce Macintosh, James Graham, Les Saddlemyer, Brian Bauman, Alexis Carlotti, Laurent Pueyo, Peter Tuthill, Christophe Dorrer, Robin Roberts, Alexandra Greenbaum

Proceedings Volume 7735, 773586 (2010) https://doi.org/10.1117/12.858623

KEYWORDS: Coronagraphy, Gemini Planet Imager, Adaptive optics, Wavefronts, Stars, Mirrors, Calibration, Wavefront sensors, Synchrotrons, Gemini Observatory

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Proceedings Article | 20 August 2009 Paper

Calibrating IR optical densities for the Gemini Planet Imager extreme adaptive optics coronagraph apodizers

Anand Sivaramakrishnan, Rémi Soummer, G. Lawrence Carr, Christophe Dorrer, Allen Bolognesi, Neil Zimmerman, Ben Oppenheimer, Robin Roberts, Alexandra Greenbaum

Proceedings Volume 7440, 74401C (2009) https://doi.org/10.1117/12.826955

KEYWORDS: Coronagraphy, Calibration, Absorbance, Gemini Planet Imager, Opacity, Synchrotrons, Glasses, FT-IR spectroscopy, Adaptive optics, Optical calibration

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Proceedings Article | 25 October 1999 Paper

Time-resolved infrared spectroscopy on the U12IR beamline at the NSLS

J. LaVeigne, G. Lawrence Carr, Ricardo Lobo, David Reitze, David Tanner

Proceedings Volume 3775, (1999) https://doi.org/10.1117/12.366637

KEYWORDS: Synchrotrons, Infrared spectroscopy, Spectroscopy, Oscillators, Absorption, Lead, Electrons, Superconductors, Pulsed laser operation, Mid-IR

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Proceedings Article | 25 October 1999 Paper

Characterization of the new NSLS infrared microspectroscopy beamline U10B

G. Lawrence Carr, Olivier Merlo, M. Munsli, S. Springer, S. Ho

Proceedings Volume 3775, (1999) https://doi.org/10.1117/12.366648

KEYWORDS: Infrared radiation, Imaging spectroscopy, Mirrors, Synchrotrons, Spectroscopy, Spatial resolution, Absorbance, Photoresist materials, Diffraction, Off axis mirrors

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Proceedings Article | 25 October 1999 Paper

Two-color experiments combining the UV storage ring free-electron laser and the SA5 IR beamline at Super-ACO

Laurent Nahon, Eric Renault, Marie-Emmanuelle Couprie, Daniele Nutarelli, David Garzella, Michel Billardon, G. Lawrence Carr, Gwyn Williams, Paul Dumas

Proceedings Volume 3775, (1999) https://doi.org/10.1117/12.366640

KEYWORDS: Free electron lasers, Ultraviolet radiation, Synchrotron radiation, Picosecond phenomena, Mirrors, Spectroscopy, Microscopes, Infrared radiation, Infrared spectroscopy, Synchrotrons

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Proceedings Article | 25 October 1999 Paper

Evidence for millimeter-wave coherent emission from the NSLS VUV ring

G. Lawrence Carr, Ricardo Lobo, J. LaVeigne, David Reitze, David Tanner, Stephen Kramer, James Murphy

Proceedings Volume 3775, (1999) https://doi.org/10.1117/12.366632

KEYWORDS: Synchrotron radiation, Vacuum ultraviolet, Modulation, Sensors, Far infrared, Particles, Infrared radiation, Synchrotrons, Spectroscopy, Electron beams

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