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Published January 20, 2008 | public
Journal Article Open

Design and initial performance of SHARP, a polarimeter for the SHARC-II camera at the Caltech Submillimeter Observatory


We have developed a foreoptics module that converts the Submillimeter High Angular Resolution Camera generation II (SHARC-II) camera at the Caltech Submillimeter Observatory into a sensitive imaging polarimeter at wavelengths of 350 and 450 μm. We refer to this module as "SHARP." SHARP splits the incident radiation into two orthogonally polarized beams that are then reimaged onto opposite ends of the 32×12 pixel detector array in SHARC-II. A rotating half-wave plate is used just upstream from the polarization-splitting optics. The effect of SHARP is to convert SHARC-II into a dual-beam 12×12 pixel polarimeter. A novel feature of SHARP's design is the use of a crossed grid in a submillimeter polarimeter. Here we describe the detailed optical design of SHARP and present results of tests carried out during our first few observing runs. At 350 μm, the beam size (9 arc sec), throughput (75%), and instrumental polarization (<1%) are all very close to our design goals.

Additional Information

© 2008 Optical Society of America. Received 25 June 2007; revised 29 October 2007; accepted 31 October 2007; posted 1 November 2007 (Doc. ID 84511); published 17 January 2008. Funding for SHARP has been provided by National Science Foundation (NSF) awards AST-02-43156 and AST-05-05230 to Northwestern University, by NSF award AST-05-05124 to The University of Chicago, and by Natural Sciences and Engineering Research Council (NSERC) Discovery grant and Canada Foundation for Innovation programs awards to The University of Western Ontario. The Caltech Submillimeter Observatory is operated with support from NSF via award AST-05-40882. We thank SHARP collaborators Roger Hildebrand, Megan Krejny, Martin Houde, Michael Attard, Hiroko Shinnaga, Jacqueline Davidson, Lerothodi Leeuw, David Chuss, Alex Lazarian, and Farhad Yusef-Zadeh for contributing to proposals, carrying out observations, and working on data analysis. We thank Richard Wylde and Paul Waltz for help with the design of SHARP, and Richard Chamberlain and the staff of the Caltech Submillimeter Observatory for assistance at the telescope. Finally, we thank Thang Bui and the staff of the Northwestern University (NU) Instrument Shop for carrying out the mechanical design and fabrication of SHARP.


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