Glan Thompson polarizers are cemented Glan prisms. They use the strong bi-refringence of natural crystal calcite to produce a high degree of p-polarization in the transmitted beam. These polarizers
provide an extinction ratio of 500,000 :1. They have a wide angular field of view almost twice that of Glan Taylor polarizers. Mounted in a metal cell they are surrounded by an opaque absorbing compound which prevents the egress of the rejected light.