High-speed optical modulator in LiNbO3 with cascaded resonant-type electrodes

A high-speed optical modulator with cascaded resonant-type electrodes is presented. To reduce the drive power and switch voltage V_π and to maintain high-modulation efficiencies, resonant reduced-length electrode structures were cascaded and integrated on LiNbO₃. Electrical power coupling into the resonators was realized by a single-input source distributed with electrical power dividers and delay lines. As a result, an optical modulator with four resonant-type cascaded electrodes was fabricated and characterized. This device, with a total active-electrode length as short as 3.4 (4 × 0.85) mm, achieved a switch efficiency V_π· L of 68 V · mm at 25 GHz at 1.55-μm wavelength, resulting in a drive power 8.7 dB less than that required for a traveling wave modulator with the same active length.