Publications

Ultrafast all-optical tuning of direct-gap semiconductor metasurfaces

Shcherbakov, Maxim R.; Liu, Sheng L.; Zubyuk, Varvara V.; Vaskin, Aleksandr; Vabishchevich, Polina P.; Keeler, Gordon A.; Pertsch, Thomas; Dolgova, Tatyana V.; Staude, Isabelle; Brener, Igal B.; Fedyanin, Andrey A.

Optical metasurfaces are regular quasi-planar nanopatterns that can apply diverse spatial and spectral transformations to light waves. However, metasurfaces are no longer adjustable after fabrication, and a critical challenge is to realise a technique of tuning their optical properties that is both fast and efficient. We experimentally realise an ultrafast tunable metasurface consisting of subwavelength gallium arsenide nanoparticles supporting Mie-type resonances in the near infrared. Using transient reflectance spectroscopy, we demonstrate a picosecond-scale absolute reflectance modulation of up to 0.35 at the magnetic dipole resonance of the metasurfaces and a spectral shift of the resonance by 30 nm, both achieved at unprecedentedly low pump fluences of less than 400 μJ cm-2. Our findings thereby enable a versatile tool for ultrafast and efficient control of light using light.