Dynamic characteristics of 1.55-um strained MQW-DFB lasers: improvement of high-speed performance by gain-coupling effects

摘要

We have fabricated 1.55 $mu@m ridge waveguide DFB lasers consisting of p-doped, 1.5% compressive strained-layer all quaternary MQW active region by two-step MOCVD with a first-order grating located in the upper GRINSCH region. By optimizing the p- doped carrier concentration in the barrier layers, kL and detuning, the measured $MIN@3 dB bandwidth was 13 GHz with flat frequency response and very little RC roll-off in this structure. From RIN measurements, the intrinsic bandwidth was calculated to be 18 GHz. Furthermore, by changing the position of the grating to the MQW active region, partly gain-coupled DFB lasers were formed; these devices exhibit very stable single mode operation and narrow spectral linewidths. The $MIN@3 dB electrical bandwidth was measured around 22 GHz and the intrinsic bandwidth was estimated to be 28 - 30 GHz. Experimental results show that the devices have small wavelength chirps and clear eye patterns under 10 Gbit/s NRZ direct modulation.