Flip-Chip Compatible Electroabsorption Modulator for up to 40 Gb/s, Integrated With 1.55 $\mu{\rm m}$ DFB Laser and Spot-Size Expander

An electroabsorption modulator (EAM) was integrated with a distributed feedback laser and a spot-size expander forming an electro-modulated laser (EML) device. The EMLs are based on the conventional InP/InGaAsP material system and are designed for flip-chip mounting. They rely on a buried heterostructure with Fe-doped blocking layers, and the EAM section is optically butt-joint-coupled. The performance of EMLs with two different EAM lengths is reported. 150 μm long EAM sections can be operated with an f_3dB bandwidth of 25 GHz allowing an error-free large signal modulation at 25 Gb/s with a dynamic extinction ratio (ER) of 11 dB. With 100 μm long EAM sections, the f_3dB bandwidth increases up to 33 GHz. Large signal modulation at 40 Gb/s is achieved with a dynamic ER of more than 8 dB. Transmission of 40 Gb/s over 2 km is demonstrated.