External-cavity InGaAs/InP graded index multiquantum well laser with a 200 nm tuning range

A tuning range of 200 nm has been achieved with a step-graded multiquantum well InGaAs/InP laser in an external-cavity configuration. Continuous, single-mode lasing could be observed from 1440 to 1640 nm. Depending on the current density, the laser can operate both at the n=1 and n=2 quantized states. At low current density, the n=1 state gives higher gain, whereas for higher carrier densities, the n=2 level dominates. This gives rise to a flat gain profile and an extended operating range, in fact, the widest tuning range reported so far for semiconductor lasers.