Observation of enhanced single longitudinal mode operation in 1.5-μm GaInAsP erbium-doped semiconductor injection lasers

Abstract

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 chosen 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. Spectrally, the narrow optical gain due to the rare-earth ion transition will superimpose on top of the broad gain peak of the host 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. Furthermore, reproducible precise lasing wavelength insensitive to temperature variation should be possible. Such a proposed rare-earth/semiconductor injection laser was investigated with erbium doping in the GaInAsP (λ=1.55 μm) active layer of the heteroepitaxial ridge-overgrown laser. Stable, single longitudinal mode operation at 15 322 Å was obtained. Furthermore, this lasing line shifted at a slow rate of ≲1 Å/°C with heat-sink temperature. Initial results do appear to confirm this new proposed rare-earth/semiconductor laser operation scheme.