Abstract
We show that the weak second harmonic light generated from a random distribution of nonlinear domains of transparent Strontium Barium Niobate crystals can display a particularly intense generation in the forward direction. By using a theoretical model able to analyze the optical response of arbitrary distributions of three-dimensional nonlinear volumes of any shape, we found that the physical origin of this observation can be explained in terms of the scattering of light by a single nonlinear domain.
Highlights
Second harmonic generation (SHG) in random materials was already considered in the early days of nonlinear optics as a way to achieve a pseudo-phase matching mechanism between the fundamental wave and the second harmonic generated wave [1, 2]
We show that the weak second harmonic light generated from a random distribution of nonlinear domains of transparent Strontium Barium Niobate crystals can display a intense generation in the forward direction
By using a theoretical model able to analyze the optical response of arbitrary distributions of three-dimensional nonlinear volumes of any shape, we found that the physical origin of this observation can be explained in terms of the scattering of light by a single nonlinear domain
Summary
Second harmonic generation (SHG) in random materials was already considered in the early days of nonlinear optics as a way to achieve a pseudo-phase matching mechanism between the fundamental (pumping) wave and the second harmonic generated wave [1, 2]. It has been generally assumed that in this kind of structures, when the fundamental field propagates in a direction perpendicular to the domain axis, the generated second harmonic light is scattered in all directions on a plane that contains the incident beam This picture has been supported by a theoretical model in which the physical origin of the uniform in-plane SHG is attributed to a homogeneous distribution of reciprocal space vectors in all directions perpendicular to the polar axis of the crystal [6, 7]. We demonstrate that the larger average size of the nonlinear domains considered in this work with respect to previous studies of SHG in SBN [5,6,7] is crucial to enable the observation of the reported enhancement of the SHG signal
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