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4Anomalous femtosecond dynamics in hybrid and all-metal magnetophotonic metasurfaces
T.V. Dolgova1*, M.A. Kiryanov1, I.A. Novikov1, G.S. Ostanin1, D.A. Safiullin1, M. Inoue2,
A.A. Fedyanin1
1-Faculty of Physics, Lomonosov Moscow State University, Moscow, 119991 Russia 2- Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology 1-1
Tempaku-cho, Toyohashi, Aichi, 441-8580 Japan
Resonant plasmonic systems can significantly increase both the degree of impact to an electromagnetic wave on the medium and the influence of the medium on the electromagnetic wave. On the other hand, powerful femtosecond laser pulses are widely used to study and control ultrafast processes in solid-state nanostructures. Therefore, it is possible to use non-steady-state ultrafast plasmonics to solve various fundamental problems. Laser heating with high peak power pulses has a nonlinear effect on the optical response of both homogeneous materials and metasurfaces. Such a pulse heats the electron gas in the metal, leading to a change in the dielectric constant. There is a theoretical model that describes the temperature of a metal when heated by a femtosecond pulse, also known as the two-temperature model [1]. The metal is considered as a two-temperature system consisting of an electron and a phonon subsystems. The model assumes that at the beginning the electron gas is heated under the influence of the incident pulse, remaining all the time in an equilibrium state. However, it turns out that such a description is not always sufficient. In resonant plasmonic and hybrid metal-dielectric systems, the dynamics of the optical response can deviate greatly from those predicted by the two-temperature model.
This work provides examples of resonant systems with the features: an all-nickel magnetoplasmonic crystal with surface modulation that implements the critical coupling condition, a hybrid metal-dielectric metasurface of gold nanospheres in yttrium-iron-garnet matrix. The results of experiments in a pump-probe scheme with features of the relaxation dynamics of the optical and magneto-optical response will be presented. Methods for describing such relaxation beyond the two-temperature model are discussed.
Besides, femtosecond laser pulses in a pump-probe design are also widely used to photogenerate charge carriers in a semiconductor to control terahertz radiation [2]. In terahertz semiconductor antennas, under the influence of a photon in the optical range, an electron-hole pair is created, which significantly changes the properties of the semiconductor in terms of the interaction of terahertz waves with it (transmission, absorption), and also allows the generation of terahertz radiation due to nonlinear interactions. If, using a femtosecond pulsed laser source, an image of a mask is projected onto a semiconductor crystal, for example, GaAs, an amplitude and phase mask corresponding to the image is formed on its surface [3]. The experimental results on propagating plasmon excitation in a tunable photoinduced gratings on GaAs surface are demonstrated above metallization fluence threshold.
This work was supported by Russian Science Foundation (Grant No. 24-12-00210).
[1] S.I. Anisimov and B.L. Kapeliovich, Electron emission from metal surfaces exposed to ultrashort laser pulses, J. Exp. Theor. Phys. 66, 375-377 (1974).
[2] I. Chatzakis, P. Tassin, L. Luo, N.-H. Shen, L. Zhang, J. Wang, T. Koschny, C.M. Soukoulis, One- and two-dimensional photo-imprinted diffraction gratings for manipulating terahertz waves, Appl. Phys. Lett. 103, 043101 (2013).
[3] G. Georgiou, H.K. Tyagi, P. Mulder, G.J. Bauhuis, J.J. Schermer, J. Gómez Rivas, Photo-generated THz antennas, Sci Rep 4, 3584 (2014).
