Narrow Linewidth 1550 nm Corrugated Ridge Waveguide DFB Lasers

We report on the design and characterization of InP-based multiple quantum well corrugated ridge waveguide distributed feedback diode lasers operating at 1550 nm. Third-order gratings have been etched along the sidewalls of the ridge waveguide using the standard I-line stepper lithography technique with an inductively coupled reactive ion etching process. An as-cleaved 1500-mu m-long laser diode shows stable continuous wave single-mode operation at 1550 nm with high side-mode suppression ratios (>50 dB), a temperature-dependent wavelength shift d lambda/dT similar to 0.095 nm/degrees C, and output powers >= 7 mW at 25 degrees C. Linewidth determination has been carried using the delayed self-heterodyne interferometric technique. Narrow linewidths (<= 250 kHz) have been observed for a wide range of current injection, with a minimum of 184 kHz at 300 mA.