Harmonic generation in the opaque region of GaAs: the role of the surface and magnetic nonlinearities
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Defense date2019-08-29
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Abstract
Phase-locked second and third harmonic generation in the opaque region of a GaAs
wafer is experimentally observed and analyzed both in transmission and reflection. These
harmonic components, which are generated close to the surface, can propagate through an opaque
material as long as the pump is tuned to a region of transparency or semitransparency and
correspond to the inhomogeneous solutions of Maxwell’s equations with nonlinear polarization
sources. We show that measurement of the angular and polarization dependence of the observed
harmonic components allows one to infer the different nonlinear mechanisms that trigger these
processes, including not only the bulk nonlinearity but also the surface and magnetic Lorentz
contributions, which usually are either hidden by the bulk contributions or assumed to be
negligible. The experimental results are compared with a detailed numerical model that takes
into account these different effects, including for the first time combined linear and nonlinear
material dispersions in a nonlinear Lorentz oscillator model of the bulk nonlinearities. Our results
suggest that the intensity of the second harmonic signal generated by the surface can be more
intense than the signal generated by the bulk. These findings have significant repercussions and
are consequential in nanoscale systems, which are usually investigated using only dispersionless
bulk nonlinearities, with near-complete disregard of surface and magnetic contributions and their
microscopic origins.
CitationRodriguez-Suné, L. [et al.]. Harmonic generation in the opaque region of GaAs: the role of the surface and magnetic nonlinearities. "Optics express", 29 Agost 2019, vol. 27, núm. 18, p. 26120-26130.
ISSN1094-4087
Publisher versionhttps://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-18-26120
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