Stable and low chirp 1.55 μm complex-coupled DFB lasers with absorptive grating

We present our experimental studies on fabricating complex-coupled distributed feedback lasers with a loss grating and a compressively strained InGaAsP multi-quantum well active region. 3 μm wide ridge waveguide lasers have been successfully fabricated and have demonstrated stable single mode operations. Kink-free light-current characteristics having a relatively low threshold current of around 25 mA have been achieved with a 0.18 W/A slope efficiency. Stable single mode emission is demonstrated with a 52 dB side mode suppression ratio, a low chirp of 0.23 nm under 1 Gb/s pseudorandom digital modulation, and a spectral linewidth of 15.8 MHz with the device operating at 2.5 times the threshold current