Abstract: Apparatus for modulation of optical signals at millimeter-wave frequencies comprises a thin elongate dielectric slab (1) of lithium niobate to partially confine and guide therein a polarized electrical signal (8) at millimeter-wave frequencies; a thinner optical waveguide (3) of lithium niobate with titanium diffused therein to substantially confine and guide therein an optical signal (9), having at least one elongate surface adjacent to an elongate surface of the dielectric slab (1); an optical grating (5) of arsenic trisulfide for directing a polarized optical signal (9) into the waveguide (3) to propagate in a lengthwise direction therein; an optical grating (7) of arsenic trisulfide for directing the optical signal (9) out of the waveguide (3) after it has traversed a predetermined distance therein; and a metallic waveguide (2) for directing an electrical signal (8) into the dielectric slab (1) in the same direction as that of the optical signal (9) in the waveguide (3), and at a center frequency such tha

Abstract: A photoconductive antenna modulator which optically modulates a radio frequency carrier signal from a dielectric waveguide antenna is disclosed. A photoconductor film is placed in proximity with the dielectric waveguide antenna such that the radio frequency carrier signal from the antenna must be conducted through the film when it is radiated into space. The carrier is then optically modulated by variably illuminating the photoconductor film with light which has wavelengths near the photoconductor film's spectral region of photoconductor sensitivity, which decreases the photoconductor film's transparency to the radio frequency carrier signal. By varying the strength of the illumination on the photoconductor film, one is able to optically modulate the radio frequency carrier signal propagated through the photoconductor.