Widely tunable self-assembled quantum dot lasers

Quantum dot laser diodes with up to five well-defined electronic shells are fabricated using self-assembled quantum dots (QDs) grown by molecular beam epitaxy. At 77 K, we tune the lasers from the first to the fourth excited state of the QDs by varying the cavity length, this covers a wavelength ran ge from 869 to 963 nm. At room temperature, we obtain lasing from the secon d to the fourth excited state covering the 938 to 984 nm wavelength range. For high injection currents, a large part of the QD ensemble contributes at once to the stimulated emission yielding a lasing emission linewidth havin g a full width at half maximum of 25 nm. By increasing the energy spacing b etween the QD energy level contributing to the lasing and the wetting layer energy levels, improved thresholds at higher temperatures are observed, le ading to lasing below 100 A/cm(2) at room temperature. (C) 2000 American Va cuum Society. [S0734-2101(00)02302-2].