Interminiband Optical Transitions in Graphene Lateral Superlattices

Gated graphene superlattices, where in-plane variations in the potential-energy profile are introduced with a periodic patterning of the gate electrode or dielectric, provide new opportunities for tailoring the electronic and optical properties of two-dimensional materials. Here we present a numerical study of the optical transitions between minibands derived from the same energy band (conduction or valence) in these systems. Giant absorption peaks at voltage-tunable THz frequencies are obtained, associated with van Hove singularities in the joint density of states of select pairs of minibands. Furthermore, we describe the possibility of interminiband THz gain in the same systems under external carrier injection, resulting from a local population inversion at specific symmetry points of the mini-Brillouin zone, even in the absence of a global inversion. These results highlight the great potential of engineered graphene superlattices for THz optoelectronic device applications, including modulators, tunable photodetectors, and lasers.