Microwave properties of GaAlAs/GaAs MQW traveling-wave interferometer optical modulator

The Mach-Zehnder Interferometer traveling-wave modulator designed by method of lines is fabricated on the substrate of semi-insulator GaAs, adopting the asymmetric multiple quantum wells with larger change of field-induced reflective index. In order to reduce the microwave loss by the unnecessary carriers, ridge waveguide is used and a mesa is wet etched. Then the microwave frequency response are measured and analyzed. It shows that the frequency response drops faster at lower frequency, and keeps no evident drop in the range of 2.5/spl sim/20 GHz which means the bandwidth of 20 GHz, and even larger for the limitation of measurement. Nevertheless, the microwave loss is relatively large. Finally, the reason is argued and the improving ways are proposed.