DIRECTIONAL COUPLER ELECTROOPTIC MODULATOR IN ALGAAS GAAS WITH LOW VOLTAGE-LENGTH PRODUCT/

An AlGaAs/GaAs ridge directional coupler electro-optic modulator with a voltage-length (VL) product of only 7.0 V mm (L=3.5 mm, V=2 V) is re ported. The low VL product has resulted from the efficient electrode c onfiguration as well as the large overlap between the optical and elec trical fields in the waveguides. Propagation loss of 3.4 dB/cm and the measured I-V characteristics confirm that the contributions from the Franz-Keldysh, charge-carrier, and thermal effects are small. To our k nowledge, this is the lowest VL product ever reported for an electro-o ptic directional coupler modulator utilizing the Pockels effect. An ex tinction ratio of 13 dB was measured for the modulator at 0.83 mum wav elength.