Efficient ultrafast all-optical modulation in a nonlinear crystalline gallium phosphide nanodisk at the anapole excitation

Gustavo Grinblat; Haizhong Zhang; Michael P Nielsen; Leonid Krivitsky; Rodrigo Berté; Yi Li; Benjamin Tilmann; Emiliano Cortés; Rupert F Oulton; Arseniy I Kuznetsov; Stefan A Maier

doi:10.1126/sciadv.abb3123

Efficient ultrafast all-optical modulation in a nonlinear crystalline gallium phosphide nanodisk at the anapole excitation

Sci Adv. 2020 Aug 21;6(34):eabb3123. doi: 10.1126/sciadv.abb3123. Print 2020 Aug.

Authors

Affiliations

¹ Departamento de Física, FCEN, IFIBA-CONICET, Universidad de Buenos Aires, C1428EGA Buenos Aires, Argentina. grinblat@df.uba.ar.
² Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 138634, Singapore.
³ School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
⁴ Chair in Hybrid Nanosystems, Nanoinstitut München, Fakultät für Physik, Ludwig-Maximilians-Universität München, 80539 München, Germany.
⁵ School of Microelectronics, MOE Engineering Research Center of Integrated Circuits for Next Generation Communications, Southern University of Science and Technology, Shenzhen, 518055 Guangdong, China.
⁶ The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, UK.

Abstract

High-refractive index nanostructured dielectrics have the ability to locally enhance electromagnetic fields with low losses while presenting high third-order nonlinearities. In this work, we exploit these characteristics to achieve efficient ultrafast all-optical modulation in a crystalline gallium phosphide (GaP) nanoantenna through the optical Kerr effect (OKE) and two-photon absorption (TPA) in the visible/near-infrared range. We show that an individual GaP nanodisk can yield differential reflectivity modulations of up to ~40%, with characteristic modulation times between 14 and 66 fs, when probed at the anapole excitation (AE). Numerical simulations reveal that the AE represents a unique condition where both the OKE and TPA contribute with the same modulation sign, maximizing the response. These findings highly outperform previous reports on sub-100-fs all-optical switching from resonant nanoscale dielectrics, which have demonstrated modulation depths no larger than 0.5%, placing GaP nanoantennas as a promising choice for ultrafast all-optical modulation at the nanometer scale.

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