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

Abstract

We have fabricated 1 .55 im 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, ii and detuning, the measured -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 -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.