High-speed traveling-wave directional coupler switch/modulator for λ = 1.32 µm

We have designed and fabricated a Ti:LiNbO3waveguide traveling-wave directional coupler switch/modulator operating atλ = 1.32 that exhibits a 3 dB modulation bandwidth of 7.2 GHz, a switching voltage of 4.5 V, and power per unit bandwidth of 7.6 mw/ GHz. Using short drive pulses, optical pulsewidths as short as 58 ps have been generated and directly measured with a high-speed InGaAs/InP p-i-n photodiode. Thick (~ 2.8 ) electroplated gold has been used to produce a small gap (5 μm) and low-loss coplanar strip electrode. The 1.5 cm long, 15 μm wide electrode has a dc resistance of 7 Ω and a total microwave power loss of ∼4dB at 5 GHz.