Photoinduced tunability of the Reststrahlen band in 4H-SiC

TL;DR

This paper demonstrates that photoexciting free carriers in 4H-SiC can actively tune the Reststrahlen band, enabling dynamic control of mid-infrared nanophotonic resonators.

Contribution

It introduces a method to actively tune the negative permittivity in 4H-SiC via photoexcitation, advancing tunable nanophotonic device development.

Findings

Photoexcitation induces significant changes in reflectance near the Reststrahlen band.

Carrier-induced permittivity changes of about 40 cm$^{-1}$ were achieved.

Potential for actively tunable mid-infrared nanophotonic devices.

Abstract

Materials with a negative dielectric permittivity (e.g. metals) display high reflectance and can be shaped into nanoscale optical-resonators exhibiting extreme mode confinement, a central theme of nanophotonics. However, the ability to $actively$ tune these effects remains elusive. By photoexciting free carriers in 4H-SiC, we induce dramatic changes in reflectance near the "Reststrahlen band" where the permittivity is negative due to charge oscillations of the polar optical phonons in the mid-infrared. We infer carrier-induced changes in the permittivity required for useful tunability (~ 40 cm$^{-1}$) in nanoscale resonators, providing a direct avenue towards the realization of actively tunable nanophotonic devices in the mid-infrared to terahertz spectral range.