Ultra-wide plasmonic tuning of semiconductor metasurface resonators on epsilon near zero media

TL;DR

This paper demonstrates large, dynamic tuning of semiconductor metasurface resonators at mid-infrared wavelengths by exploiting temperature-dependent free-carrier effects in InSb, enabling highly reconfigurable optical devices.

Contribution

It introduces a novel approach to achieve significant refractive index tuning in semiconductor metasurfaces using temperature-dependent free-carrier effects in InSb.

Findings

Nearly two-fold increase in electron effective mass in doped InSb

Over 10-fold change in thermal free-carrier concentration in undoped InSb

Resonance shifts greater than 1.5 micrometers in tunable metasurfaces

Abstract

Fully reconfigurable metasurfaces would enable new classes of optical devices that provide unprecedented control of electromagnetic beamforms. The principal challenge for achieving reconfigurability is the need to generate large tunability of subwavelength, low-Q metasurface resonators. Here, we demonstrate large refractive index tuning can be efficiently facilitated at mid-infrared wavelengths using novel temperature-dependent control over free-carrier refraction. In doped InSb we demonstrate nearly two-fold increase in the electron effective mass leading to a positive refractive index shift ({\Delta}n>1.5) far greater than conventional thermo-optic effects. In undoped films we demonstrate more than 10-fold change in the thermal free-carrier concentration producing a near-unity negative refractive index shift. Exploiting both effects within a single resonator system, intrinsic InSb wires on a heavily doped (epsilon near zero) InSb substrate, we demonstrate dynamically tunable Mie resonances. The observed larger than line-width resonance shifts ({\Delta}{\lambda}>1.5{\mu}m) suggest new avenues for highly tunable and reconfigurable mid-infrared semiconductor metasurfaces.