Narrow linewidth and wavelength tunable distributed feedback lasers

Results obtained for an experimental three-section multiple-quantum-well distributed-feedback (DFB) laser with a long cavity and a lambda /4 phase-shifted grating are reviewed. To narrow the linewidth, a 1.2-mm-long cavity, Bragg wavelength detuning of -20 nm from gain peak, and a quantum-well active layer were used. Wavelength tuning was achieved by controlling spatial hole burning using three electrodes with nonuniform current injection. The maximum wavelength tuning range was 1.6 nm, the minimum linewidth was 350 kHz, and FM response was flat from 100 kHz to 10 GHz, making the laser suitable for use in coherent optical fiber transmission systems.<>