Extended tunability of a self-seeded gain-switched InGaAsP laser using an intracavity absorber

The authors show that the use of a small absorber section with DC voltage control can improve the spectral tunability of gain-switched quantum well InGaAsP lasers. Using a self-seeding configuration, singlemode picosecond pulses are produced over a spectral range of 50nm, at a repetition rate of several gigahertz and a constant average output power of several milliwatts. The spectral evolutions of gain and absorption with bias conditions are deduced from net gain measurements under threshold. The extension of tunability to short wavelengths is correlated with the absorption red shift caused by the quantum confined Stark effect at negative voltages. Results are applicable to the design of two section gain-switched distributed feedback lasers capable of operating far from gain maximum.