A PCSS comprises a photoconductive semiconductor block that exhibits electrically-conductive behavior when exposed to light of a predetermined wavelength; two or more electrodes fixed to the photoconductive semiconductor block and connectable to a power supply; a resonance cavity enveloping the photoconductive semiconductor block, the resonance cavity having a reflective outer surface to trap light within the resonance cavity and the photoconductive semiconductor block, the resonance cavity having a window through the reflective outer surface to admit light of the predetermined wavelength, the resonance cavity being transmissive to light of the predetermined wavelength within the reflective outer surface; and a light source directed toward the photoconductive semiconductor block and through the window, and emitting light at the predetermined wavelength. The photoconductive semiconductor block may include Si, GaAs, GaN, AlN, SiC, and/or Ga2O3. The resonance cavity may include glass, crystal, Au, Ag, Cr, Ni, V, Pd, Pt, Ir, Rh, and/or Al.