Photodetector, comprising a substrate, and supported by the substrate a configuration configured to act as optical resonator and to absorb incident radiation of a band, in particular infrared radiation, the configuration comprising: - a resonant frontside structure comprising frontside elements arranged in a periodic pattern, the frontside structure facing the incident radiation, - a backside structure arranged between the frontside structure and the substrate, wherein the backside structure serves as optical element that in combination with the frontside structure contributes to the optical resonating property of the configuration, the frontside structure being made from an electrically conducting material, and - a layer of an active material made from a semiconducting material, and configured to convert at least part of the incident radiation of the band into charge carriers, - a dielectric spacer between the backside structure and the frontside structure, wherein the frontside structure is in contact with the active material, wherein the active material is arranged on top of the dielectric spacer, wherein the configuration is configured to selectively absorb the incident radiation of the band, wherein the frontside structure, but not the backside structure, is contacted by electrical contacts for sensing the charge carriers in the active material, wherein the active material comprises an amorphous or a polycrystalline material, characterized in that the frontside structure is arranged between the dielectric spacer and the active material, or in that the frontside structure is arranged embedded in the active material. a substrate, and supported by the substrate a configuration configured to act as optical resonator and to absorb incident radiation of a band, in particular infrared radiation, the configuration comprising: - a resonant frontside structure comprising frontside elements arranged in a periodic pattern, the frontside structure facing the incident radiation, - a backside structure arranged between the frontside structure and the substrate, wherein the backside structure serves as optical element that in combination with the frontside structure contributes to the optical resonating property of the configuration, the frontside structure being made from an electrically conducting material, and - a layer of an active material made from a semiconducting material, and configured to convert at least part of the incident radiation of the band into charge carriers, - a dielectric spacer between the backside structure and the frontside structure, - a resonant frontside structure comprising frontside elements arranged in a periodic pattern, the frontside structure facing the incident radiation, - a backside structure arranged between the frontside structure and the substrate, wherein the backside structure serves as optical element that in combination with the frontside structure contributes to the optical resonating property of the configuration, the frontside structure being made from an electrically conducting material, and - a layer of an active material made from a semiconducting material, and configured to convert at least part of the incident radiation of the band into charge carriers, - a dielectric spacer between the backside structure and the frontside structure, wherein the frontside structure is in contact with the active material, wherein the active material is arranged on top of the dielectric spacer, wherein the configuration is configured to selectively absorb the incident radiation of the band, wherein the frontside structure, but not the backside structure, is contacted by electrical contacts for sensing the charge carriers in the active material, wherein the active material comprises an amorphous or a polycrystalline material, characterized in that the frontside structure is arranged between the dielectric spacer and the active material, or in that the frontside structure is arranged embedded in the active material.