Abstract: A sensor arrangement performs simultaneous measurement of optical and electrical properties of a dielectric medium to be investigated, as well as the analytes contained therein. The arrangement contains a field-effect transistor and a surface plasmon resonance sensor. The sensor arrangement further contains a sample chamber for receiving the dielectric medium, which sample chamber is arranged such that the optical and electrical properties of the dielectric medium can be recorded simultaneously. The gate electrode of the field-effect transistor forms the active surface and/or is connected to the active surface of the surface plasmon resonance sensor, and has charge carriers which can be caused to oscillate by use of electromagnetic radiation.