An improved achromatic half-wave plate phase shifter for white light interferometry

Polarization components can be used as nearly achromatic phase shifters in an interferometers. Here we present an improved achromatic half-wave plate (HWP) phase shifter that can be incorporated at the input end of a white light interferometer. A nearly achromatic HWP phase shifter that can be used at the input of an interferometer consists of a rotating HWP followed by a quarter wave plate (QWP) fixed at an azimuth of 45 degrees. An improved achromatic phase shifter for the input end can be constructed using achromatic circular polarizers. The performance of this achromatic HWP phase shifter when used at the input end of a white light interferometer is studied using Jones calculus. The calculated values of the phase shifts between the interfering beams and their amplitudes are very nearly same for all the wavelengths. This phase shifter thus gives much improved performance.