An experiment to demonstrate the angular Doppler effect on laser light

Abstract

Two simple and related experiments are outlined that allow the student to investigate the frequency shift experienced by a laser light beam when passing through a rotating half-wave retardation plate. The shift arises due to the energy exchange between a rotating optical element, in this case a half-wave plate, and a circularly polarized light beam. The shift is directly proportional to the rotation frequency of the optical element. The shift may be interpreted as an angular Doppler effect for light.