Title: Ultra-wide plasmonic tuning of semiconductor metasurface resonators on epsilon near zero media,
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.