WAVE-COUPLED LINBO3 ELECTROOPTIC MODULATOR FOR MICROWAVE AND MILLIMETER-WAVE MODULATION

The phase velocity mismatch due to material dispersion in traveling-wave LiNbO3 optical waveguide modulators may be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface dipole antenna. The array of antennas is then illuminated by the modulation signal from below at the proper angle to produce a delay from antenna to antenna that matches the optical waveguide's delay. A phase modulator 25 mm in length with five antennas and five transmission line segments was operated from 4.6 to 13 GHz with a maximum phase modulation sensitivity over 100-degrees/W1/2.