2019/10/01 by L. Rodríguez-Suné, Michael Scalora, Rodriguez-Sune, Laura +15 · 2 citations
Chemistry · Physics and Astronomy · #FOS: Physical sciences #Laser-Matter Interactions and Applications #Optics (physics.optics) #Spectroscopy and Laser Applications #Spectroscopy and Quantum Chemical Studies
paper · pdf · doi:10.48550/arxiv.1910.00313
openalex publication_date 2019/10/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report comparative experimental and theoretical studies of second and\nthird harmonic generation from a 20nm-thick indium tin oxide layer in proximity\nof the epsilon-near-zero condition. Using a tunable OPA laser we record both\nspectral and angular dependence of the generated harmonic signals close to this\nparticular point. In addition to the enhancement of the second harmonic\nefficiency close to the epsilon-near-zero wavelength, at oblique incidence\nthird harmonic generation displays unusual behavior, predicted but not observed\nbefore. We implement a comprehensive, first-principles hydrodynamic approach\nable to simulate our experimental conditions. The model is unique, flexible,\nand able to capture all major physical mechanisms that drive the electrodynamic\nbehavior of conductive oxide layers: nonlocal effects, which blueshift the\nepsilon-near-zero resonance by tens of nanometers; plasma frequency redshift\ndue to variations of the effective mass of hot carriers; charge density\ndistribution inside the layer, which determines nonlinear surface and magnetic\ninteractions; and the nonlinearity of the background medium triggered by bound\nelectrons. We show that by taking these contributions into account our\ntheoretical predictions are in very good qualitative and quantitative agreement\nwith our experimental results. We show that by taking these contributions into\naccount our theoretical predictions are in very good qualitative and\nquantitative agreement with our experimental results. We expect that our\nresults can be extended to other geometries where ENZ nonlinearity plays an\nimportant role.\n