Abstract

Berry's phases in optics have been studied extensively, and examples are typically discussed in quantum-mechanical terms. To our knowledge, however, experimental demonstrations have been performed only at the classical level. We report the first observation of a Berry's phase at the single-photon level. In particular, we investigated Pan-charatnam's phase,¹ which is acquired whenever light is taken through a closed cycle of polarization states, e.g., with various retardation plates. Correlated pairs of linearly-polarized photons were produced by parametric fluorescence in a UV-pumped KDP crystal. One of each pair was directed into a photomultiplier tube (PMT1). The other was directed into a Michelson interferometer, one arm of which contained two quarter-wave plates, that was used to generate a Berry's phase.

© 1990 Optical Society of America