Polaritons in 2D materials are fundamentally interesting for different technological applications, but their coupling to light is generally weak due to their momentum mismatch. In this work, we remarkably show that a small scatterer placed at a suitable distance from a given surface can couple light completely into the surface modes supported by the surface, under illumination by a modulated field. We present rigorous closed-form prescriptions for the modulation of the incident light beam which maximizes this coupling, depending on the characteristics of the scatterer and surface, and use the derived expressions to provide a rigorous theoretical analysis of the extremal light coupling to plasmons in different 2D materials (namely thin metals and graphene). We corroborate the analytical results by performing fully-numerical simulations using realistic setups, which exhibit a very strong enhancement of the absorption into surface plasmons under the prescribed optimal conditions.
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