40-GHZ BANDWIDTH INGAAS/INALAS MULTIPLE QUANTUM-WELL OPTICAL-INTENSITY MODULATOR

High-speed waveguide InGaAs/InAlAs multiple quantum well (MQW) optical intensity modulators are demonstrated. To minimize the modulator capacitance, an undoped InAlAs cladding layer is added over the MQW core layer in the optical waveguide. In addition, polyimide is spin coated under the bonding pad. As a result, a very wide bandwidth in excess of 40 GHz is developed with a driving voltage of 6 V for a 10-dB extinction ratio and a linewidth broadening factor alpha of < 1.0 at an operating wavelength of 1.54-mu-m. The frequency response of the modulator is limited by the device capacitance and inductance.