Anisotropic Wave Breaking in Highly Nonlinear Thermal Media

In optics, many phenomena are ruled by the nonlinear Schrödinger equation (NLSE), as solitons and dispersive shock waves (DSWs). We report experiments on 2D-optical DSWs with anisotropic singularity in m-cresol/nylon, and provide theoretical description by time asymmetric quantum mechanics (TAQM) [1].

M-cresol/nylon is a chemical solution with an isotropic giant self-defocusing nonlinearity. When it is enlightened by a CW laser beam, the material experiences a thermo-optical effect, governed by the nonlocal version of the defocusing NLSE.

By choosing an initial beam shape (propagating along z) that has null intensity along x = 0, a new kind of wave breaking emerges: the shock develops undular bores on the beam external borders, but around the singularity it presents an abrupt intensity discontinuity.

We analyze this shock and find that it is caused by the interplay of a trapping/focusing potential along x and an antitrapping/defocusing potential along y. While the trapping potential is the standard harmonic oscillator (HO), the antitrapping potential is the reversed HO, a paradigmatic model in TAQM. Indeed, light propagation is described by a superposition of exponential decays with quantized decay rates, a fundamental TAQM signature.

[1] G. Marcucci et al., arXiv:1909.04506