Propagation and absorption of light in planar dielectric waveguides with two-dimensional semiconductors

Strong optical responses of atomically thin two-dimensional (2D) semiconductors make them attractive candidates for integration into various photonic and optoelectronic structures. We discuss some fundamental effects of such integration into planar dielectric waveguides by demonstrating that a substantial modification of the spectrum of waveguide modes can occur due to high in-plane polarizability of 2D layers. Our calculations illustrate both the conceptual possibilities associated with sharp excitonic resonances as well as the results obtained with the experimentally assessed polarizability of monolayer MoS₂ over a broad spectral range. We point out that waveguide structures could also enable the tunable absorption by 2D semiconductors of the light that propagates along them, a modality quite different from the traditional light harvesting geometry.