BROADLY TUNABLE EXTERNAL-CAVITY LASER-DIODES WITH STAGGERED THICKNESSMULTIPLE-QUANTUM WELLS

Widely tunable low-threshold current laser diodes fabricated from an e ngineered multiple-quantum-well (MQW) gain structure consisting of thr ee compressively strained In0.2Ga0.8As wells of different thicknesses are reported, Using a grating in an external cavity, a continuous-wave tuning range of 70 nm (911-981 nm) is measured for a 155-mu m semicon ductor cavity length device at a current of 32 mA, This is the lowest reported bias current for a semiconductor laser with this broad a tuni ng range, A maximum continuous wave tuning of 80 nm (901-981 nm) has b een measured at a bias current of 95 mA, At long wavelengths, a suppre ssion of amplified spontaneous emission and preferential population of the lowest energy well were observed.