Low-voltage, 50 Omega , GaAs/AlGaAs travelling-wave modulator with bandwidth exceeding 25 GHz

Travelling-wave, Mach-Zehnder electro-optic modulators to a new design in GaAs/AlGaAs are described. Velocity matching, with 50 Ω impedance and high electro-optic efficiency, is achieved using a capacitively loaded stripline approach. Devices with Vx = 4.85 V (λ = 1152 nm) have 3 dB bandwidths of 25.5 GHz, while those with shorter electrodes (Vx = 5.7 V) show no roll-off below 26.5 GHz. The bandwidth/voltage ratio for these devices represents the highest yet reported for any class of electro-optic modulator.