Experimental observation of fractal modes in unstable optical resonators

TL;DR

This paper experimentally demonstrates that eigenmodes in unstable optical resonators exhibit fractal patterns with maximum roughness, providing new insights into wave behavior in open systems.

Contribution

It provides the first direct experimental observation of fractal eigenmodes in unstable optical cavities, confirming theoretical predictions.

Findings

Eigenmodes have fractal patterns with a fractal dimension of approximately 3.

The patterns exhibit maximum roughness consistent with theoretical models.

The results enhance understanding of wave dynamics in open, unstable systems.

Abstract

We use a spatially resolved cavity ring-down technique to show that the 2D eigenmode of an unstable optical cavity has a fractal pattern, i.e. it looks the same at different length scales. In agreement with theory, we find that this pattern has the maximum conceivable roughness, i.e., its fractal dimension is 3.01 plus\minus 0.04. This insight in the nature of unstable cavity eigenmodes may lead to better understanding of wave dynamics in open systems, for both light and matter waves.