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Deep Optical Switching on Subpicosecond Timescales in an Amorphous Ge Metamaterial
Author(s) -
Lemasters Robert,
Shcherbakov Maxim R.,
Yang Guoce,
Song Jia,
Lian Tianquan,
Harutyunyan Hayk,
Shvets Gennady
Publication year - 2021
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.202100240
Subject(s) - materials science , picosecond , amorphous solid , optoelectronics , transmittance , resonator , metamaterial , ultrashort pulse , nanoscopic scale , optics , relaxation (psychology) , lasing threshold , laser , nanotechnology , physics , psychology , social psychology , chemistry , organic chemistry , wavelength
Active nanostructured optical components show promise as potential building blocks for novel light‐based computing and data processing architectures. However, nanoscale all‐optical switches that have low activation powers and high‐contrast ultrafast switching have been elusive so far. Here, pump–probe measurements performed on amorphous‐Ge‐based micro‐resonator metasurfaces that exhibit strong resonant modes in the mid‐infrared are reported. Relative change is observed in transmittance of Δ T / T ≈ 1 with picosecond (down to τ ≈ 0.5 ps) free carrier relaxation rates, obtained with very low pump fluences of 50 μJ cm −2 . These observations are attributed to efficient free carrier promotion, affecting light transmittance via high quality‐factor optical resonances, followed by an increased electron–phonon scattering of free carriers due to the amorphous crystal structure of Ge. Full‐wave simulations based on a permittivity model that describes free‐carrier damping through crystal structure disorder find excellent agreement with the experimental data. These findings offer an efficient and robust platform for all‐optical switching at the nanoscale.