A planar waveguide analysis of the mode extinction modulator in LiNbO3

An analysis of the mode extinction modulator is reported based on a step index planar waveguide model. Three modulation mechanisms, the propagation loss, the coupling loss, and the radiative transfer, have been shown to have a significant influence on the transfer function shape and the performance characteristics of the device. The propagation loss effect is shown to play a dominant role in device efficiency and linearity. The operating point of the device can be selected by the choice of physical parameters without the use of a dc bias voltage. Verification of the modulation mechanisms has been demonstrated experimentally.