In second harmonic generation (SHG), the energy of two incoming photons, e.g., from a femtosecond laser, can be combined in one outgoing photon of twice the energy, e.g., by means of a nonlinear crystal. The SHG efficiency, however, is limited. In this work, the harvested signal is maximized by composing a hybrid system consisting of a nonlinear crystal with a dense coverage of plasmonic nanostructures separated by narrow gaps. The method of self-assembled diblock-copolymer-based micellar lithography with subsequent electroless deposition is employed to cover the whole surface of a lithium niobate (LiNbO3) crystal. The interaction of plasmonic nanostructures with light leads to a strong electric near-field in the adjacent crystal. This near-field is harnessed to enhance the near-surface SHG signal from the nonlinear crystal. At the plasmon resonance of the gold nanoparticles, a pronounced enhancement of about 60-fold SHG is observed compared to the bare crystal within the confocal volume of a laser spot.
Enhancement of the second harmonic signal of nonlinear crystals by self-assembled gold nanoparticles
Note: This paper is part of the JCP Special Topic on Emerging Directions in Plasmonics.
Emre Gürdal, Anke Horneber, Nadim Shaqqura, Alfred J. Meixner, Dieter P. Kern, Dai Zhang, Monika Fleischer; Enhancement of the second harmonic signal of nonlinear crystals by self-assembled gold nanoparticles. J. Chem. Phys. 14 March 2020; 152 (10): 104711. https://doi.org/10.1063/1.5139893
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