Very low chirping of InGaAs-InGaAlAs MQW DFB BRS lasers under 10 Gbit/s modulation

The ability of the InGaAs/InGaAlAs multi-quantum-well (MQW) system to achieve ultra-low-chirp operation under 10-Gb/s operation is experimentally demonstrated. The MQW active layer has been grown by a solid-source molecular beam epitaxy (MBE) method. Two metalorganic chemical vapor deposition (MOCVD) regrowths were used to fabricate the distributed-feedback (DFB) buried ridge structure (BRS) lasers. DFB BRS lasers with good static and spectral performance have been obtained. Under 10-Gb/s modulation those lasers exhibited a chirp value as low as 0.11 nm at -20 dB, which is attributed to an extremely small phase-amplitude coupling coefficient of 1.8. An analysis of the AM and FM modulated laser field under digital pseudorandom signal confirms the observed spectra and shows the possibility of an optimum spectrum width for lasers with small chirping.< >