Neutrino oscillations with a polarized laser beam: an analogical demonstration experiment

The underlying physics of neutrino oscillation in vacuum can be demonstrated by an optical analogical experiment. Two different neutrino flavors are represented by two polarization states of a laser beam, whereas the different phase propagation in vacuum is mimicked by the propagation difference of an ordinary and an extraordinary beam in a birefringent crystal. This allows us to demonstrate neutrino oscillation by optical methods in a fully microscopic way at the particle level. The description of both realizations of oscillation is also mathematically identical. In our demonstration experiment we can vary the oscillation parameters such as propagation length L and mixing angle Theta.

💡 Research Summary

The paper presents a tabletop optical analogue of neutrino oscillations that can be used both as a pedagogical demonstration and as a proof‑of‑concept that the mathematics of flavor oscillations is not limited to high‑energy particle physics. In the analogue, the two neutrino flavors are mapped onto two orthogonal polarization states of a laser beam (for example, horizontal and vertical linear polarizations or left‑ and right‑handed circular polarizations). The mixing angle Θ, which in the neutrino context quantifies the rotation between flavor and mass eigenstates, is implemented by rotating the input polarizer (or a wave plate) by the same angle before the beam enters the oscillation medium.

The “propagation in vacuum” that gives rise to a relative phase between the two mass eigenstates is mimicked by the birefringent crystal. Inside the crystal an ordinary ray (o‑ray) and an extraordinary ray (e‑ray) travel with different refractive indices (n_o) and (n_e). Consequently the two polarization components acquire a relative phase
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