Systems and methods detect changes in incident optical radiation at high frequencies. A detector having one or more asymmetrically conductive areas, formed of relaxation semiconductor material, is configured with at least two electrical contacts, positioned on opposite sides of an active area. Asymmetrical conductivity, for example provided by use of one doped contact and one un-doped contact, creates a transient voltage across the active area, which is measured by electronics connected with the electrical contacts. The transient voltage indicates changes in incident optical radiation, which may be distributed spatially uniformly over the system.