Ultrafast all-optical tuning of direct-gap semiconductor metasurfaces

TLDR

Optical metasurfaces are quasi‑planar nanopatterns that can transform light spatially and spectrally, yet they are normally fixed after fabrication, posing a challenge for fast, efficient post‑fabrication tuning. This work seeks to develop a rapid, efficient method to tune the optical properties of metasurfaces after fabrication. The authors experimentally realize a gallium arsenide metasurface that delivers picosecond‑scale reflectance modulation of 0.35 and a 30‑nm resonance shift at pump fluences below 400 μJ cm⁻², enabling versatile ultrafast light control. Shcherbakov et al.

Abstract

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.Metasurfaces are not adjustable after fabrication, and a critical challenge is to realise a technique of tuning their optical properties that is both fast and efficient. Here, Shcherbakov et al. realise an ultrafast tunable metasurface with picosecond-scale large absolute reflectance modulation at low pump fluences.