Paper
12 May 2015 Polarizers for a spectral range centered at 121.6 nm operating by reflectance or by transmittance
Juan I. Larruquert, A. Marco Malvezzi, Angelo Giglia, José A. Aznárez, Luis Rodríguez-de Marcos, José A. Méndez, Paolo Miotti, Fabio Frassetto, Giuseppe Massone, Gerardo Capobianco, Silvano Fineschi, Stefano Nannarone
Author Affiliations +
Abstract
Polarimetry is a powerful tool to interpret how the coronal plasma is involved in the energy transfer processes from the Sun’s inner parts to the outer space. Space polarimetry in the far ultraviolet (FUV) provides essential information of processes governed by the Doppler and Hanle resonant electron scattering effects. Among the key FUV spectral lines to observe these processes, H I Lyman α (121.6 nm) is the most intense. Some developing or proposed solar physics missions, such as CLASP, SolmeX, and COMPASS, plan to perform polarimetry at 121.6 nm. Classical solutions, such as a parallel plate of a transparent material, either MgF2 or LiF, result in a modest efficiency of the passing polarization component. The development of more efficient linear polarizers at this wavelength will benefit future space instruments. A research has been conducted to develop polarizers based on (Al/MgF2)n multilayer coatings in a band containing 121.6 nm, to obtain a significant efficiency increase over plates. Coatings operating by reflectance resulted in a high efficiency after approximately one year of storage under nitrogen. In parallel, coating polarizers operating by transmittance have been prepared for the first time. Transmissive polarizers have the advantage that they involve no deviation of the beam. As a further benefit, the developed transmittance polarizers additionally incorporate filtering properties to help reject wavelengths both shortwards and longwards of a band containing 121.6 nm. Hence a polarizer combined with a filter is obtained with a single device. The combined polarizer-filter could enable a higher performance polarimeter for solar physics if the use of a separate filter to isolate Lyman α turns unnecessary.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Juan I. Larruquert, A. Marco Malvezzi, Angelo Giglia, José A. Aznárez, Luis Rodríguez-de Marcos, José A. Méndez, Paolo Miotti, Fabio Frassetto, Giuseppe Massone, Gerardo Capobianco, Silvano Fineschi, and Stefano Nannarone "Polarizers for a spectral range centered at 121.6 nm operating by reflectance or by transmittance", Proc. SPIE 9510, EUV and X-ray Optics: Synergy between Laboratory and Space IV, 951008 (12 May 2015); https://doi.org/10.1117/12.2179446
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KEYWORDS
Polarizers

Reflectivity

Transmittance

Polarization

Magnesium fluoride

Polarimetry

Optical filters

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