Novel Planar Electrode Structure for High-Speed (>40 GHz) Electroabsorption Modulators

A novel planar electrode structure has been developed for the fabrication of high-speed electroabsorption (EA) modulators. To reduce the modulator capacitance, a narrow high-mesa waveguide is fabricated by inductively coupled plasma (ICP) dry etching technique. A planarized electrode is then formed by inserting a thick SiO2 insulation mesa beneath the bonding pad, and photo-sensitive polymer is adopted to fill the trench between the ridge and the SiO2 mesa. The planarization procedure is carried out in a self-aligned way. The capacitance of fabricated EA modulators is estimated to be 0.12 pF, and a modulation bandwidth over 40 GHz has been demonstrated.