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18 July 2014 Polarization gratings for visible and near-infrared astronomy
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We report on the development of polarization gratings that can be used for polarimetry and/or high throughput broadband spectroscopy in astronomy. Polarization gratings are able to overcome fundamental limitations on the diffraction efficiency of conventional gratings to provide near 100% diffraction efficiency over a broad bandwidth. The broad spectral coverage of these devices will be useful for observations of gamma-ray bursts and supernovae of unknown the redshift, where spectral features may fall over a range of wavelengths. As a spectropolarimeter a polarization grating would be ideal, for example, for the study of dusts and hazes, whose polarimetric properties vary with wavelength. We present the results of a series of laboratory measurements of the diffraction efficiency and modulation efficiency of a prototype grating designed for operation from 500 to 900 nm. We find that the grating is able to achieve greater than 90% diffraction efficiency from 500 to 850 nm and modulate incident circular polarized light with an efficiency of ~ 99%. Our future plans include on-sky testing at a small local telescope, with an eventual goal of incorporating a polarization grating into the design of a microshutter array- based multi-object visible/NIR spectrograph for a 10m class facility.
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Max Millar-Blanchaer, Dae-Sik Moon, James R. Graham, and Michael Escuti "Polarization gratings for visible and near-infrared astronomy", Proc. SPIE 9151, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, 91514I (18 July 2014);

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