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 - 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 of the resonance layer, and - to thus set 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, wherein - the plasmon resonance layer is a semiconductor layer of intrinsic conductivity, - the tuning device comprises a first tuning layer formed by a first doped semiconductor layer of a first conductivity type and a second tuning layer formed by a second doped semiconductor layer of a second conductivity type opposite to the first conductivity type, each of the first and second tuning layers being connected with a respective first or second tuning control electrode, and in that - the plasmon resonance layer is arranged between the first and second tuning layers to form a p-i-n structure, thus allowing an injection of free charge carriers into the plasmon resonance layer in a density amount that depends on an injection control voltage applied via the first and second tuning control electrodes, characterized in that the tuning device further comprises a piezoelectric third tuning layer configured and arranged to be deformed piezoelectrically and to thus exert tensile stress on the plasmon resonance layer with a stress amount depending on a strain control voltage applied to the tuning layer via at least one strain control electrode, thus modifying a lattice strain amount present in the plasmon resonance layer and in turn changing an effective mass of the free charge carriers in the plasmon resonance layer. - 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 - 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 of the resonance layer, and - to thus set 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, - the plasmon resonance layer is a semiconductor layer of intrinsic conductivity, - the tuning device comprises a first tuning layer formed by a first doped semiconductor layer of a first conductivity type and a second tuning layer formed by a second doped semiconductor layer of a second conductivity type opposite to the first conductivity type, each of the first and second tuning layers being connected with a respective first or second tuning control electrode, and in that - the plasmon resonance layer is arranged between the first and second tuning layers to form a p-i-n structure, thus allowing an injection of free charge carriers into the plasmon resonance layer in a density amount that depends on an injection control voltage applied via the first and second tuning control electrodes,