Apparatus for optical communications (10, 110, 210) includes a low-temperature grown photoconductor (12, 140, 220) coupled to at least one resonant tunneling device (14, 120, 130, 230, 240). When exposed to an input light, low-temperature grown photoconductor (10, 110, 210) absorbs photons, which decreases the resistivity, and thus the resistance of the photoconductor. This decrease in resistance causes a decrease in the voltage drop across photoconductor (12, 140, 220), which causes a corresponding increase in the voltage drop across resonant tunneling device (14, 120, 130, 230, 140).