A substrate support apparatus for a plasma processing system includes a layer of dielectric material having a top surface and a bottom surface. The top surface is defined to support a substrate in exposure to a plasma. The substrate support apparatus also includes a number of optical fibers each having a first end and a second end. The first end of each optical fiber is defined to receive photons from a photon source. The second end of each optical fiber is oriented to project photons received from the photon source onto the bottom surface of the layer of dielectric material.