Atomic-Void van der Waals Channel Waveguides.

Layered van der Waals materials allow creating unique atomic-void channels with subnanometer dimensions. Coupling light into these channels may further advance sensing, quantum information, and single molecule chemistries. Here, we examine theoretically limits of light guiding in atomic-void channels and show that van der Waals materials exhibiting strong resonances, excitonic and polaritonic, are ideally suited for deeply subwavelength light guiding. We predict that excitonic transition metal dichalcogenides can squeeze >70% of optical power in just <λ/100 thick channel in the visible and near-infrared. We also show that polariton resonances of hexagonal boron nitride allow deeply subwavelength (<λ/500) guiding in the mid-infrared. We further reveal effects of natural material anisotropy and discuss the influence of losses. Such van der Waals channel waveguides while offering extreme optical confinement exhibit significantly lower loss compared to plasmonic counterparts, thus paving the way to low-loss and deeply subwavelength optics.