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A&A Supplement series, Vol. 123, May II 1997, 179-182

Received May 14; accepted September 16, 1996

Optical materials for near infrared Wollaston prisms

E. Olivatex2html_wrap1143, S. Gennaritex2html_wrap1145, L. Vanzitex2html_wrap1147, A. Carusotex2html_wrap1149, and M. Ciofinitex2html_wrap1151

Send offprint request: E. Oliva

tex2html_wrap1153  Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
tex2html_wrap1155  Dipartimento di Astronomia e Scienza dell Spazio, Università di Firenze, Largo E. Fermi 5, I-50125 Firenze, Italy
tex2html_wrap1157  Istituto Nazionale di Ottica, Largo E. Fermi 6, I-50125 Firenze, Italy


The optical characteristics of birefringent materials transmitting in the near IR (0.9-2.5 tex2html_wrap_inline1101m) are analyzed. Wollaston prisms with large beam separation and virtually free from lateral chromatism - e.g. with fields of view >1 arcmin and image elongation tex2html_wrap_inline1105 - could be manufactured using AgGaStex2html_wrap_inline1107 or LiYFtex2html_wrap_inline1109 (YLF). These materials are used for non linear applications and may therefore find another interesting application in IR focal plane instruments. From the optical point of view the best material is AgGaStex2html_wrap_inline1111 but YLF may be practically more convenient because of its lower refractive index (tex2html_wrap_inline1113), better thermo-mechanical properties and lower price.

New measurements of the transparency of Calcite at room and cryogenic temperatures are also presented, these show significant absorption (tex2html_wrap_inline1115 tex2html_wrap_inline1117) of the ordinary ray already at tex2html_wrap_inline1119 tex2html_wrap_inline1121m and very strong bands (absorption coefficient tex2html_wrap_inline1123 cmtex2html_wrap_inline1125) beyond 2.25 tex2html_wrap_inline1127m. The absorption does not decrease significantly when the crystals is cooled, CaCOtex2html_wrap_inline1129 should not be therefore used in instruments working beyond 2.0 tex2html_wrap_inline1131m.

keywords: instrumentation: miscellaneous -- instrumentation: polarimeters

Copyright by the European Southern Observatory (ESO)