Wang K.Chen L.Zhang H.Hsiao H.-H.Tsai D.P.Chen J.HUI-HSIN HSIAO2022-09-192022-09-192017https://www.scopus.com/inward/record.uri?eid=2-s2.0-85032904327&doi=10.1063%2f1.5002581&partnerID=40&md5=495a8ebcabdbf5ed488e991dfce4b30bhttps://scholars.lib.ntu.edu.tw/handle/123456789/621114Ultrafast all-optical switching in metals can be an efficient way for high-speed active photonic devices. However, with the improvement in modulation speed, typically by reducing the optical switching pulse width from picoseconds to femtoseconds, the nonlinear optical response of the metal will decrease significantly, which hinders the realization of the sufficient modulation depth at femtosecond optical control. Here, by combining two optical nonlinear enhancement effects of surface plasmon polaritons, including their extreme sensitivity to refractive index change and their capability to induce strong localized optical fields, we have achieved an ∼50-times enhancement in the modulation depth simultaneously with a switching time of ∼75-fs. Such enhancement was found to be independent of the control intensity, which sets a basis for the future application of femtosecond switching at a minimum power. © 2017 Author(s).[SDGs]SDG3Electromagnetic wave polarization; Modulation; Optical signal processing; Optical switches; Photonic devices; Plasmons; Refractive index; Switching; Active photonic devices; All-optical switching; Future applications; Nonlinear optical response; Optical nonlinearity; Refractive index changes; Surface plasmon polaritons; Ultrafast all-optical switching; Nonlinear opticsjournal article10.1063/1.50025812-s2.0-85032904327