Separate Confinement Heterostructure Ridge Overgrown Distributed Feedback (SCH-RO-DFB) Laser Diode was fabricated by two step liquid phase epitaxy (LPE). Third order grating was formed by holographic interference lithography using Ar ion laser after the first epitaxy for distributed feedback. The ridges were overgrown by an additional selective liquid phase epitaxy with r.f. sputtered $SiO_2$ mask.
Electrical and optical properties of the fabricated laser diodes were investigated. From the investigation of spectral and luminescence-current (L-I) characteristics, DFB lasing action is observed, sometimes, together with the Fabry Perot mode osciallations for laser diodes with two cleaved facets. The coexistence of the two lasing modes was consistently confirmed from the spectral and L-I characteristics. Contrary to the strong dependence of the lasing wavelength of the pumping current for the Fabry Perot modes (117.5 Å/A), much smaller dependence of 6.7Å/A which corresponds to the refractive index change with injection current was observed for the DFB modes.
