A new index-guided AlGaInP visible semiconductor laser with very small astigmatism

The authors demonstrate a novel index-guided AlGaInP visible semiconductor laser with very small astigmatism. This laser, composed of a twin-groove ridge stripe structure, is formed by a two-step MOVPE process (metal-organic vapor phase epitaxy). After the AlGaInP (0.8 mu m)/GaInP (0.8 mu m) double heterostructure is grown on an n-GaAs substrate, a 3.5- mu m-wide ridge stripe is formed by etching the p-AlGaInP cladding layer, leaving a 0.3- mu m-thick cladding layer on the GaInP active layer. Then, n-GaAs selective growth is carried out on the etched cladding layer, and a 4- mu m-wide twin groove just near the ridge stripe structure is fabricated by selectively etching the n-GaAs current blocking layer. Finally, a Si/sub 3/N/sub 4/ insulating block with low refractive index is formed only in the twin groove. As a result of the new structure, the visible laser is realized with not only the index-guide mode but also with low thermal resistivity ( approximately 50 K/W). Transverse-mode stabilized CW operation at room temperature was achieved at a lasing wavelength of 670 mu m, a threshold current of 70 mA, and an external differential quantum efficiency of 20%/facet.