Surface-enhanced second harmonic generation and fluorescence using effectively lossless GaP nanoantennas in the visible regime

J. CAMBIASSO; G. GRINBLAT; Y. LI; A. RAKOVICH; E. CORTÉS; S. A. MAIER

Conferencia; The 8th International Conference on Metamaterials; 2017

The initial motivation on plasmonic nanostructures for the development of nanophotonic devices operating in the optical regime was later partially eclipsed by the realization that losses could, in some cases, overtake actual radiative properties.[1,2] In this scenario, dielectric nanoantennas have recently emerged as promising alternative candidates to plasmonic systems in the visible range.[3,4] High-refractive-index dielectric nanostructures can highly concentrate electric and magnetic fields within subwavelength volumes, while presenting ultra-low absorption, compared to metals, when excited above their band gap energies.[5] In particular, dielectric nanoantennas are expected to boost both nonlinear phenomena and surface-enhanced spectroscopies, without producing significant heating, since locally enhancing the incident light intensity can significantly amplify these processes, as their efficiencies increase with the excitation density.GaP, in particular, is a dielectric with an associated band gap wavelength as small as 550 nm and a relatively high refractive index of 3.5, opening interesting opportunities for the development of ultra-low-loss nanophotonic antennas in the optical range. In this presentation, efficient generation of second harmonic light is demonstrated throughout the visible regime by suitably tuning the size of single GaP nanodisks, enhancing their nonlinear response by more than three orders of magnitude with respect to the bulk, via surface effects.[6] Furthermore, by analysing the radiative properties of fluorescent molecules located in the hot-spot of a GaP dimer nanoantenna with 35 nm gap, a fluorescence enhancement factor as high as 2640 is attained when comparing with the bare emitter.[6] Both, high-field confinement effects, and a fluorescence lifetime reduction of more than one order of magnitude, give rise to the measured enhancement factor. The results of this work open new avenues for low-loss nanophotonics in the optical range.[1] Albella, P.; Poyli, M. A.; Schmidt, M. K.; Maier, S. A.; Moreno, F.; Sáenz, J. J.; Aizpurua, J. J. Phys. Chem. C 2013, 117, 13573-13584.[2] Khurgin, J. B. Nat. Nanotech. 2015, 10, 2-6. [3] Caldarola, M.; Albella, P.; Cortés, E.; Rahmani, M.; Roschuk, T.; Grinblat, G.; Oulton, R. F.; Bragas, A. V.; Maier, S. A. Nat. Commun. 2015, 6, 7915. [4] Regmi, R.; Berthelot, J.; Winkler, P. M.; Mivelle, M.; Proust, J.; Bedu, F.; Ozerov, I.; Begou, T.; Lumeau, J.; Rigneault, H.; García-Parajó, M. F.; Bidault, S.; Wenger, J.; Bonod, N. Nano Lett. 2016, 16, 5143-5151. [5] Albella, P.; Alcaraz de la Osa, R.; Moreno, G.; Maier S. A. ACS Photonics 2014, 1, 524-529. [6] Cambiasso, J.; Grinblat, G.; Li, Yi.; Rakovich, A.; Cortés, E.; Maier, S. A. Submitted, 2017.