Method to model the cross-polarization of millimeter-wave telescopes using a commercial optical software package

Luca Olmi; Daniel J. Hoppe

doi:10.1117/12.458234

14 February 2003 Method to model the cross-polarization of millimeter-wave telescopes using a commercial optical software package

Luca Olmi, Daniel J. Hoppe

Author Affiliations +

Proceedings Volume 4843, Polarimetry in Astronomy; (2003) https://doi.org/10.1117/12.458234
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

We discuss the conceptual and practical guidelines of a method to calculate the cross-polarization of a telescope, including its relay optics, using a commercial optical design software, without the need to use complex, slow and expensive Physical Optics programs. These effects are usually negligible at visible and infrared wavelengths but may be of considerable importance at radio wavelengths. Offset reflector antenna configurations, common in the telecommunication industry, and antenna relay optics consisting of offset mirrors, common in millimeter and submillimeter-wave telescopes, result in an increased contribution to the cross-polarization. Polarization measurements are also becoming very important in Radio Astronomy. In fact, dust emission polarimetry and the study of linearly polarized, nonmasing, rotational lines (e.g., CO) with submm telescopes are both powerful diagnostic of magnetic fields in molecular clouds. However, the low average source polarization requires a careful optimization of the optical design to keep any instrumental polarization contribution from both telescope and relay optics as low as possible in astronomical polarimetry experiments. Likewise, in telecommunications applications polarization separation can be used to effectively double the available bandwidth provided the isolation between the two orthogonal polarization states is sufficient.

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Luca Olmi and Daniel J. Hoppe "Method to model the cross-polarization of millimeter-wave telescopes using a commercial optical software package", Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003); https://doi.org/10.1117/12.458234

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