High-speed low-voltage modulation with a nonsymmetric Mach-Zehnder interferometer

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Abstract
The authors demonstrate broadband optical modulation with a Ti:LiNbO/sub 3/ nonsymmetric interferometer at microwave frequencies up to 16 GHz. The 3-dB bandwidth of 8.7 GHz is only slightly less than the theoretical limit of 9.6 GHz for a 1-cm-long device. The device uses a 2- mu m-thick gold-plated asymmetric stripline electrode, with a characteristic impedance of 40 Omega and ohmic loss of 3 dB/cm at 10 GHz. The DC switching voltage is 6.5 V, and the on/off ratio is -16 dB. Fabrication tolerances in the nonsymmetric interferometer are much less strict than for directional coupler modulators with comparable performance, making this device a better candidate for use in communications systems.