Linewidth-narrowed distributed feedback injection lasers with long cavity length and detuned Bragg wavelength

We report linewidth narrowing for 1.3-μm InGaAsP distributed feedback lasers with either a long cavity length or a detuned Bragg wavelength. The narrowest linewidth measured was 3 MHz at 6 mW for a 780-μm long-cavity laser, and was 8 MHz at 5.5 mW for a 250-μm regular-length laser with detuned wavelength. From our analysis, distributed feedback lasers with 1 MHz linewidth appear to be feasible.