Revealing the modal content of obstructed beams

Abstract: In this work, we propose a predictor/indicator of the self-healing ability of coherent structured light beams: the field's modal content. Specifically, the fidelity between the obstructed and unobstructed beams' modal spectrum serves as a useful measure of the degree to which the beam will likely self-heal after an arbitrary obstacle. Since any optical field can be decomposed in terms of any chosen orthonormal basis, this analysis is, therefore, less restrictive than other methods for determining self-healing ability. Furthermore, since modal content is propagation invariant, this allows beam self-reconstruction to be studied in this way at any convenient transverse plane. As a case study, we present convincing experimental evidence for the superiority of the self-healing properties of Laguerre-Gaussian over Bessel-Gaussian beams; analysis that is facilitated primarily by the proposed measure.