Oscillation properties of AlGaAs DH lasers with an external grating

External control of the longitudinal oscillation mode of AlGaAs double heterostructure lasers using a diffraction grating is presented. Dependence of threshold current on selected mode wavelength is observed experimentally and is compared with a theory based on multilongitudinal mode rate equations. Baseband frequency responses for various bias currents above threshold are estimated by small-signal analysis and coincide well with experimental observations. Resonance frequency shifts to lower frequency and the resonance width is broadened by the optical feedback. Theoretical and experimental step pulse responses are also studied. Single longitudinal mode builds up rapidly. Relaxation oscillation observed after the oscillation builds up is less damped when mode selective feedback is provided. Output fluctuation frequency corresponds to the resonance frequency.