We present a low chirp electroabsorption modulator integrated DFB laser (EML) fabricated by a selective area growth double stack active layer technique. A stable single mode operation can be obtained and the typical side mode suppression ratio (SMSR) is over 53 dB. The threshold current of the device is about 16 mA and the optical output power from the EAM fact is over 8 mW at an injection current of 80 mA. A static extinction ratio as high as 34 dB can be obtained when the bias voltage is approaching -5 V. The chirp parameters of the EML chip are measured with a fiber resonance method. Negative chirp parameters can be obtained when the reverse bias voltage increases to 1 V. A clear 25 Gb/s back to back eye diagram can be achieved and a 20 Gb/s eye diagram can be seen after the transmission of 25 km single mode fiber. The EAM can operate at 20 Gb/s with a dynamic extinction of 8.6 dB with a driving voltage as low as 0.65 V. The fabricated EML chip shows great advantages in very-short-reach systems as well as long distance applications.
We represent a high speed evanescently coupled waveguide UTC-PD. It is shown that a layer of polymer layer under the electrical pads can enlarge the response bandwidth of a UTC-PD greatly. The effects of the polymer layer are also studied with numerical simulations, which show the same trend.