variation in one unavoidably leads to a change in the other. Polarization beating has a unique character that the geometric and dynamical phases are entangled, i.e. We demonstrate both approaches experimentally by using an interferometer with a fast detector and a specific polarimetric arrangement. The geometric phase inherent in polarization beating is governed by a compact expression containing only the Stokes parameters of the interfering waves and can alternatively be obtained from the individual beam intensities and the amplitude of the intensity beats.

Varying the intensity and polarization characteristics of the beams, the relative contributions of the geometric and dynamical phases can be adjusted. We show that the phase difference over a single beating period decomposes into the Pancharatnam–Berry geometric phase and a dynamical phase of which the former depends exclusively on the intensities and polarization states of the interfering beams whereas the sum of the phases is determined solely by the beam frequencies. In this work, we reveal a foundational and elegant phase structure underlying such polarization beating. When two monochromatic optical beams of different frequencies and states of polarization interfere, the polarization state of the superposition field exhibits temporal periodic variation-polarization beating. Beating is a simple physical phenomenon known for long in the context of sound waves but remained surprisingly unexplored for light waves.

Equation for intensity of a light wave