Efficient linewidth reduction in conventional 1.5 mu m laser diodes by integration to a weakly coupled InGaAsP Bragg waveguide with low optical losses

Detuned single-mode lasers with excellent linewidth performance (minimum linewidth of 2 MHz) have been obtained by monolithically coupling a low loss, low kappa tunable InGaAsP Bragg waveguide (BW) to double-channel planar buried heterostructure 1.5- mu m GaInAsP laser diodes using conventional liquid-phase epitaxy (LPE) fabrication techniques. The results compare favorably to the results obtained by coupling a Fabry-Perot laser to a SiO/sub 2/-Si/sub 3/N/sub 4/-SiO/sub 2/ BW. The main advantages of the present method over the hybrid approach are the mechanical stability and the excellent coupling between the sections of the integrated device. Further reduction of the kappa of the InGaAsP BW should result in even lower linewidths.<
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