Ultrafast all-optical tuning of direct-gap semiconductor metasurfaces

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

doi:10.1038/s41467-017-00019-3

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.

Highlights

Optical metasurfaces are regular quasi-planar nanopatterns that can apply diverse spatial and spectral transformations to light waves
By means of femtosecond wide-band pump–probe spectroscopy, we demonstrate, for the first time to our knowledge, free-carrier-induced absolute reflectance modulation of up to 0.35 under low pump fluence values and with recovery times of about 6 ps mainly determined by surface-mediated recombination processes
Analysing the efficiency of the observed all-optical modulation, it becomes evident that using direct-gap semiconductors as the constituent material for metasurfaces is key to developing active nonlinear-optical nanodevices

Summary

Introduction

Optical metasurfaces are regular quasi-planar nanopatterns that can apply diverse spatial and spectral transformations to light waves. Spectral and polarisation control of the optical response was demonstrated by a large body of research, achieving fast and efficient temporal control remains an open challenge Such control would dramatically enhance the scope of optical metasurfaces, as their functionalities would no longer be permanently encoded during the fabrication process but could be tuned on demand. Numerous ways of actively modulating the optical properties of metasurfaces were reported, including phase-change materials[5, 6], mechanical tuning[7, 8], liquid-crystal-based tuning[9], and all-optical modulation[10,11,12,13] None of these approaches allows for fast and efficient modulation at the same time.

Methods

Results

Conclusion