Electrically modulatable photodiode, comprising a substrate having a first and a second p-n junction, a common contact for jointly contacting the p or n dopings of the two p-n junctions, and two further contacts for separately contacting the other doping of the p and n dopings of the two p-n junctions, and a circuit, wherein the circuit is designed to measure a current flow caused by charge carriers which have been generated by impinging radiomagnetic waves in the substrate and which have reached the first further contact, and to switch the second further contact at different times to at least one first and one second switching state, wherein in the first switching state the second further contact is switched to the floating state and in the second switching state a potential is applied, and wherein a blocking voltage applied between the common contact and the first further contact is constant.