Path length enhancement in disordered media for increased absorption

Year: 2015

Authors: Mupparapu R., Vynck K., Svensson T., Burresi M., Wiersma D.

Autors Affiliation: European Laboratory for Non-linear Spectroscopy (LENS), Via Nello Carrara 1, Sesto Fiorentino, 50019, Italy; Istituto Italiano di Tecnologia, via Morego 30, Genova, 16163, Italy; Laboratoire Photonique, Numérique et Nanosciences (LP2N), UMR 5298, CNRS, IOGS, Univ. Bordeaux, Talence, 33400, France; Istituto Nazionale di Ottica, Consiglio Nazionale Delle Ricerche, Largo Fermi 6, Firenze, 50125, Italy; Universitá di Firenze, Dipartimento di Fisica e Astronomia, via Giovanni Sansone 1, Sesto Fiorentino, 50019, Italy

Abstract: We theoretically and numerically investigate the capability of disordered media to enhance the optical path length in dielectric slabs and augment their light absorption efficiency due to scattering. We first perform a series of Monte Carlo simulations of random walks to determine the path length distribution in weakly to strongly (single to multiple) scattering, non-absorbing dielectric slabs under normally incident light and derive analytical expressions for the path length enhancement in these two limits. Quite interestingly, while multiple scattering is expected to produce long optical paths, we find that media containing a vanishingly small amount of scatterers can still provide high path length enhancements due to the very long trajectories sustained by total internal reflection at the slab interfaces. The path length distributions are then used to calculate the light absorption efficiency of media with varying absorption coefficients. We find that maximum absorption enhancement is obtained at an optimal scattering strength, in-between the single-scattering and the diffusive (strong multiple-scattering) regimes. This study can guide experimentalists towards more efficient and potentially low-cost solutions in photovoltaic technologies. (C) 2015 Optical Society of America

Journal/Review: OPTICS EXPRESS

Volume: 23 (24)      Pages from: A1472  to: A148

More Information: We acknowledge ENI S.p.A, the Eu-NoE “Nanophotonics for Energy Efficiency” for their financial support. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n. [291349].
KeyWords: Dielectric materials; Efficiency; Electromagnetic wave absorption; Intelligent systems; Monte Carlo methods; Multiple scattering; Refractive index, Absorbing dielectrics; Absorption co-efficient; Absorption enhancement; Analytical expressions; Light absorption efficiency; Path length distribution; Photovoltaic technology; Total internal reflections, Light absorption
DOI: 10.1364/OE.23.0A1472

Citations: 26
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