Observation of enhanced single-longitudinal mode operation in 1.5microns GaInAsP Erbium-doped semiconductor injection lasers.

We propose a new type of current injection semiconductor laser with rare-earth dopant in the active layer for achieving stable single-longitudinal mode operation. In this laser, the rare- earth/semiconductor combination is choosen such that the wavelengths of the dominant emission from the trivalent rare-earth ion internal 4f-4f transitions are shorter than that of the band- edge emission of the host semiconductor. This presumably leads to two important new consequences: (1) The transfer of electrons from the conduction-band to the upper level (excited state) of the rare-earth is by a resonant process; (2) Spectrally, the narrow optical gain due to the rare-earth ion transition will superimpose on top of the broad gain peak of the hose semiconductor. Such laser diodes will attain lasing action at the rare-earth transition wavelength resulting in single- longitudinal mode operation with conventional Fabry-Perot cavity.