On the Quest for High-efficiency Third-harmonic Generation on the Nanoscale

G. GRINBLAT; I. ABDELWAHAB; T. SHIBANUMA; P. ALBELLA; K. LENG; X. CHI; A. RUSYDI; Y. LI; K. P. LOH; S. A. MAIER

Simposio; Progress In Electromagnetics Research Symposium; 2018

Enhancing nonlinear optical effects on the nanometre scale is a topic of extensive theoretical and experimental studies. Among nonlinear photonics phenomena, light-frequency upconversion has attracted significant attention from the scientific community in the past years, as it is highly desirable for applications spanning (bio)-imaging and sensing to the development of optoelectronic hybrid devices. In particular, third harmonic generation (THG) is a nonlinear optical effect that coherently triples the energy of the incident photons. Recently, some of us have shown that all-dielectric germanium nanodisks can yield THG conversion efficiencies between 1E-4% and 1E-3% when excited at specific Mie resonances [1-3], exceeding by several orders of magnitude corresponding values that can be achieved through plasmonic nanoantennas or other nanomaterials. This presentation will focus on two other approaches that can further push these efficiencies close to 1E-2%.First, it will be shown that a suitably designed hybrid dielectric/metallic silicon/gold nanoantenna can locally enhance the incident light intensity inside the silicon region, giving rise to a nonlinear response that outperforms the nanoantenna's individual metallic and dielectric components by more than 5 and 3 orders of magnitude, respectively [4]. Furthermore, it will be demonstrated thatthe maximum THG emission can be tuned throughout the whole visible range by conveniently modifying the size of the nanoantenna. In a second part, a completely different strategy will be presented, considering two-dimensional hybrid organic-inorganic Ruddlesden-Popper perovskites (RPPs), which possess a natural multi-quantum-well structure. It will be shown that their THG emission can be resonantly enhanced at the excitonic band gap energy of the 2D RPP crystals, producing THG conversion efficiencies more than 5 orders of magnitude higher than previously reported values for 2D materials [5]. Our study of mechanically exfoliated flakes from four different lead halide 2D RPP single crystals shows that their THG emission can be tuned from violet to red by selecting the RPP homologue with the requisite resonance. Interestingly, it isfound that the strongest nonlinear response is achieved for thicknesses less than 100 nm, mainly due to THG signal depletion effects. REFERENCES [1] Grinblat, G., Y. Li, M. Nielsen, R. F. Oulton, and S. A. Maier, Nano Letters, Vol. 16, 4635-4640, 2016. [2] Grinblat, G., Y. Li, M. Nielsen, R. F. Oulton, and S. A. Maier, ACS Nano, Vol. 11, 953-960,2017. [3] Grinblat, G., Y. Li, M. Nielsen, R. F. Oulton, and S. A. Maier, ACS Photonics, Vol. 4, 2144-2149, 2017. [4] Shibanuma, T., G. Grinblat, P. Albella, and S. A. Maier, Nano Letters, Vol. 17, 2647-2651,2017. [5] Abdelwahab, I., G. Grinblat, K. Leng, Y. Li, X. Chi, A. Rusydi, S. A. Maier, and K. P. Loh, ACS Nano, Vol. 12, 644-650, 2018.