Spectral linewidth reduction by MOVPE grown 1.5 μm quantum well DFB LDS

A marked spectral linewidth reduction was achieved by using 1.5-μm quantum-well distributed-feedback (QW DFB) laser diodes. The InGaAs/InGaAsP QW heterostructure was fabricated on (001)InP substrates with 2400 angstrom period grating by the low-pressure (76 torr) metalorganic vapor-phase epitaxy (MOVPE) technique. High QW DFB wafer qualities were evidenced by photoluminescence (PL) measurement. The intensity and FWHM for the PL spectra were comparable to those for QW wafers grown on flat InP substrates. Threshold currents were 15-20 mA. Stable single-frequency CW operation was maintained at a more than 20-mW light output power level. Spectral linewidths were measured by the delayed self-homodyne method. A minimum linewidth of 2.0 MHz was achieved at 6-mW output.