Abstract: A tunable plasmon resonator, comprising a plasmon resonance layer made of graphene, a crystalline group-IV-semiconductor material or a crystalline group-III-V semiconductor material, and arranged on a carrier substrate, the plasmon resonance layer having a plasmon resonance region that is exposed to a sensing volume and a tuning device that is integrated into the plasmon resonator and arranged and configured to modify a density of free charge carriers in the plasmon resonance region or to modify an effective mass amount of the free charge carriers in the plasmon resonance region by applying of a control voltage to tuning control electrode(s) of the tuning device, thereby setting a plasmon frequency of plasmon polaritons in the plasmon resonance region to a desired plasmon frequency value within a plasmon frequency tuning interval, for resonance excitation of plasmon polaritons by incident electromagnetic waves of a frequency corresponding to the set plasmon frequency value.