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Coronagraph Focal-Plane Phase Masks Based on Photonic Crystal Technology: Recent Progress and Observational StrategyPhotonic crystal, an artificial periodic nanostructure of refractive indices, is one of the attractive technologies for coronagraph focal-plane masks aiming at direct imaging and characterization of terrestrial extrasolar planets. We manufactured the eight-octant phase mask (8OPM) and the vector vortex mask (VVM) very precisely using the photonic crystal technology. Fully achromatic phase-mask coronagraphs can be realized by applying appropriate polarization filters to the masks. We carried out laboratory experiments of the polarization-filtered 8OPM coronagraph using the High-Contrast Imaging Testbed (HCIT), a state-of-the-art coronagraph simulator at the Jet Propulsion Laboratory (JPL). We report the experimental results of 10-8-level contrast across several wavelengths over 10% bandwidth around 800nm. In addition, we present future prospects and observational strategy for the photonic-crystal mask coronagraphs combined with differential imaging techniques to reach higher contrast. We proposed to apply a polarization-differential imaging (PDI) technique to the VVM coronagraph, in which we built a two-channel coronagraph using polarizing beam splitters to avoid a loss of intensity due to the polarization filters. We also proposed to apply an angular-differential imaging (ADI) technique to the 8OPM coronagraph. The 8OPM/ADI mode avoids an intensity loss due to a phase transition of the mask and provides a full field of view around central stars. We present results of preliminary laboratory demonstrations of the PDI and ADI observational modes with the phase-mask coronagraphs.
Document ID
20140002147
Document Type
Conference Paper
External Source(s)
Authors
Murakami, Naoshi (Hokkaido Univ. Sapporo, Japan)
Nishikawa, Jun (Tokyo Astronomical Observatory Mitaka, Japan)
Sakamoto, Moritsugu (Hokkaido Univ. Sapporo, Japan)
Ise, Akitoshi (Hokkaido Univ. Sapporo, Japan)
Oka, Kazuhiko (Hokkaido Univ. Sapporo, Japan)
Baba, Naoshi (Hokkaido Univ. Sapporo, Japan)
Murakami, Hiroshi (Tokyo Univ. Sagamihara, Japan)
Tamura, Motohide (Tokyo Astronomical Observatory Mitaka, Japan)
Traub, Wesley A. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Mawet, Dimitri (European Southern Observatory Santiago, Chile)
Moody, Dwight C. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Kern, Brian D. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Trauger, John T. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Serabyn, Eugene (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Hamaguchi, Shoki (Hokkaido Univ. Sapporo, Japan)
Oshiyama, Fumika (Hokkaido Univ. Sapporo, Japan)
Date Acquired
March 20, 2014
Publication Date
July 1, 2012
Subject Category
Instrumentation and Photography
Meeting Information
SPIE Astronomical Telescopes and Instrumentation 2012(Amsterdam)
Funding Number(s)
CONTRACT_GRANT: JSPS 21340041
CONTRACT_GRANT: JSPS 23740139
CONTRACT_GRANT: JSPS 19360036
CONTRACT_GRANT: SJPS 204783
Distribution Limits
Public
Copyright
Other
Keywords
coronagraphy
photonic crystal
extrasolar planets
polarization
eight-octant phase mask
high-contrast imaging
vector vortex mask