Achromatic Wave Plates for the Visible Spectrum*

Abstract

We report the experimental demonstration of an optical quarter-wave plate having a retardation of 90°±1° in the region from 4000 to 8000 Å. The device is based on the synthesis procedure of Harris, Ammann, and Chang and consists of six sapphire wave plates with appropriately oriented principal axes. The device does not suffer from thermal or angular problems as do longer, narrow-band birefringent networks. Results comparing a 10-plate unit with the above 6-plate unit are given.