Extraordinary wavelength reduction in terahertz graphene-cladded photonic crystal slabs

TL;DR

This paper demonstrates that graphene-cladded photonic crystal slabs can achieve a 100x wavelength reduction in the terahertz regime, enabling ultra-compact terahertz photonic devices with strong confinement and broad band gaps.

Contribution

The study introduces a novel graphene cladding approach that allows silicon photonic crystal slabs to operate in the terahertz range with extreme wavelength scaling and excellent confinement.

Findings

Achieved 100x wavelength reduction in terahertz photonic crystal slabs.

Demonstrated broad two-dimensional photonic band gaps with near-zero thickness slabs.

Showed waveguiding with propagation lengths of tens of lattice constants.

Abstract

Photonic crystal slabs have been widely used in nanophotonics for light confinement, dispersion engineering, nonlinearity enhancement, and other unusual effects arising from their structural periodicity. Sub-micron device sizes and mode volumes are routine for silicon-based photonic crystal slabs, however spectrally they are limited to operate in the near infrared. Here, we show that two single-layer graphene sheets allow silicon photonic crystal slabs with submicron periodicity to operate in the terahertz regime, with an extreme 100x wavelength reduction and excellent out-of-plane confinement. The graphene-cladded photonic crystal slabs exhibit band structures closely resembling those of ideal two-dimensional photonic crystals, with broad two-dimensional photonic band gaps even when the slab thickness approaches zero. The overall photonic band structure not only scales with the graphene Fermi level, but more importantly scales to lower frequencies with reduced slab thickness. Just like ideal 2D photonic crystals, graphene-cladded photonic crystal slabs confine light along line defects, forming waveguides with the propagation lengths on the order of tens of lattice constants. The proposed structure opens up the possibility to dramatically reduce the size of terahertz photonic systems by orders of magnitude.