Highly efficient resonantly enhanced modulators on X-cut LiNbO3 are investigated through the use of numerical optimization. We describe the optimization technique and present a new design trend relating the link-gain efficiency of optical radio systems that employ external modulation to the choice of modulator electrode geometric dimensions, especially the electrode gap. Using this optimization technique, resonant-type modulators with link gain enhancement up to 6 dB are achievable while maintaining excellent return loss at a resonant frequency of 1.8 GHz. The characteristics of both the optical waveguide and the coplanar electrode are characterized by finite-element simulation.
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