Development and RF characteristics of analog 60-GHz electroabsorption modulator module for RF/optic conversion

We developed an analog 60-GHz module for RF/optic conversion by using an electroabsorption modulator (EAM) device associated with a traveling-wave electrode. The impedance matching of the module was accomplished with the 30-Ω termination such that the resonance was precisely located at 60 GHz and the fractional bandwidth at S₁₁=-15 dB was as large as 1.0 GHz. The RF/optic conversion gain of the EAM device revealed a strong dependence on the input optical power and was closely related with the slope change in the optical transmission characteristic with reverse bias. From the EAM module with the composite-type multiple-quantum-well electroabsorption core consisting of both 8- and 12-nm quantum wells, we obtained the optimal RF/optic conversion gain at the reverse bias between 1.5-2 V in a wide range of input optical power from -6 to +9 dBm. In the same bias range, the third-order intermodulation distortion was <-49.5 dBc as obtained with RF input of -7.5 dBm.