Nonlinear optical processes are known to be weak in bulk materials and extremely small at the nanoscale since they mainly scale with the volume. Here I will show how we enhance second-harmonic generation in two typical χ2 non centrosymmetric nanomaterials.
First, in barium titanate nanoparticles, we take advantage of various resonances occurring in the visible wavelength range. Contrary to plasmonics occurring in metallic nanostructures, those resonances take place in dieletric nanoparticles and they are well described by the Mie scattering theory.
Second, in lithium niobate nanowires, we demonstrate phase-matching and use it to increase the guided second-harmonic power by a factor of more than 80. We also increase non-phase-matched guided second-harmonic by engineering the nanowire length. Those bright nanostructures can serve for developing compact efficient nonlinear optical sources or waveguides.
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