Linear interferometric waveguide modulator for electromagnetic-field detection

A channel-waveguide interferometer with asymmetric arms, suitable for electromagnetic-field detection, is described. A π/2 intrinsic phase differential makes the output linearly proportional to the applied voltage (electromagnetic field). Horizontal and vertical electrode sets provide polarization-independent operation, with electrode lengths chosen to make the voltages approximately equal. In Ti-diffused devices in Z–X-cut LiNbO3, the TE- and TM-mode outputs are equally modulated with the horizontal voltage 43% of the vertical. Output linearity over a 40-dB range and operation up to 300 MHz are demonstrated.