Dripping, pressure and surface tension of self-trapped laser beams

TL;DR

This paper demonstrates that self-trapped laser beams in nonlinear media exhibit liquid-like properties such as pressure, surface tension, and capillarity, with a thermodynamic framework and analytical validation of droplet-like behavior.

Contribution

It introduces a thermodynamic approach to describe laser beam dynamics, revealing liquid analogies and deriving the Young-Laplace law for optical solitons.

Findings

Laser beams exhibit pressure and surface tension analogous to liquids.

Stationary solitons satisfy the Young-Laplace equation.

Dynamical evolution mimics droplet growth in liquids.

Abstract

We show that a laser beam which propagates through an optical medium with Kerr (focusing) and higher order (defocusing) nonlinearities displays pressure and surface-tension properties yielding capillarity and dripping effects totally analogous to usual liquid droplets. The system is reinterpreted in terms of a thermodynamic grand potential, allowing for the computation of the pressure and surface tension beyond the usual hydrodynamical approach based on Madelung transformation and the analogy with the Euler equation. We then show both analytically and numerically that the stationary soliton states of such a light system satisfy the Young-Laplace equation, and that the dynamical evolution through a capillary is described by the same law that governs the growth of droplets in an ordinary liquid system.