Plasmonic enhancement of second harmonic generation from nonlinear RbTiOPO_4 crystals by aggregates of silver nanostructures

Abstract

Abstract:We demonstrate a 60-fold enhancement of the second harmonic generation (SHG) response at the nanoscale in a hybrid metal-dielectric system. By using complex silver nanostructures photochemically deposited on the polar surface of a ferroelectric crystal, we tune the plasmonic resonances from the visible to the near-infrared (NIR) spectral region, matching either the SH or the fundamental frequency. In both cases the SHG signal at the metal-dielectric interface is enhanced, although with substantially different enhancement values: around 5 times when the plasmonic resonance is at the SH frequency or up to 60 times when it matches the fundamental NIR radiation. The results are consistent with the more spatially-extended near-field response of complex metallic nanostructures and can be well explained by taking into account the quadratic character of the SHG process. The work points out the potential of aggregates of silver nanostructures for enhancing optical nonlinearities at the nanoscale and provides an alternative approach for the development of nanometric nonlinear photonic devices in a scalable way. References and links1. J. A. Armstrong, N. Bloembergen, J. Ducuing, and P. S. Pershan, "Interactions between light waves in a nonlinear dielectric," Phys. Rev. 127(6), 1918-1939 (1962). 2. P. Franken, A. E. Hill, C. W. Peters, and G. Weinreich, "Generation of optical harmonics," Phys. Rev. Lett. 7(4), 118-120 (1961). 1720-1723 (2011). 9. H. Aouani, M. Rahmani, M. Navarro-Cía, and S. A. Maier, "Third-harmonic-upconversion enhancement from a single semiconductor nanoparticle coupled to a plasmonic antenna," Nat. Nanotechnol. 9(4), 290-294 (2014). 10. N. Kauranen and A. V. Zayats, "Nonlinear plasmonics," Nat. Photonics 6(11), 737-748 (2012 harmonic emission by plasmonic resonances at the second harmonic wavelength," Nano Lett. 15(6), 3917-3922 (2015).

Hybrid Plasmonic–Ferroelectric Architectures for Lasing and SHG Processes at the Nanoscale

“…However, their influence on the spatially selective photodeposition of metallic structures was not reported until 2001, when Giocondi and Rohrer demonstrated in a pioneer work the possibility to control the photochemical reduction of silver NPs on the surface of Barium Titanate, BaTiO 3 . Since then, the combination of domain selective photodeposition process with ferroelectric domain structures has been exploited to produce a variety of metallic arrangements on different ferroelectric crystals …”

“…Finally, it has also been reported the possibility of shaping the organization of metallic nanostructures into predefined ferroelectric arrangements by tuning external parameters such as temperature, solution concentration, flux of photogenerated electrons (irradiation time), stoichiometry, or the irradiation photon energy . For example, increasing the temperature of the photoreduction process will decrease the magnitude of the spontaneous polarization, which leads to a larger amount of uncompensated screening charges.…”

“…This fact, combined with the ability of shaping ferroelectric domains structures with different geometries allows fabricating 1D and 2D plasmonic arrangements of interacting NPs of different size and separation distances. Isolated nanocubes, elongated prisms, millimetrically long linear chains, or large polygonal arrangements of closely spaced Ag NPs, constitute different examples of the plasmonic arrangements attained by this technique …”

“…However, at nanoscopic dimensions, the performance of frequency conversion processes undergoes fundamental limitations mainly related to the efficiency of the NL process itself, which is associated with the interaction length of the participating waves. To overcome this drawback, the association of plasmonic nanostructures with quadratic NL dielectric materials can benefit from both the field enhancement provided by the plasmonic arrangements and the high second‐order susceptibility, χ 2 , values of specific NL crystals, offering a useful route for boosting NL processes at the nanoscale . The versatility of the plasmonic arrangements could envisage the development of dense integrated nanophotonic circuits useful for integrated NL photonics.…”

Plasmonic Enhancement in the Fluorescence of Organic and Biological Molecules by Photovoltaic Tweezing Assembly

“…A factor 8 was obtained in another system with Cy5 dye molecules, where the LSPR linked to arrays of Ag‐nanoparticles matches both absorption and emission bands of the dye . Moreover, in a recent work concerning SHG, the authors use Ag‐metallic structures (formed by aggregates) on RTP crystals, a structure rather similar to our PV patterns. The enhancement factor in our FL experiments (around 10) is somewhat higher than that obtained in the SHG experiments (factor 5) when the SH frequency matches the plasmon resonance of the nanostructure.…”