Study of the spectral width of intermode beats and optical spectrum of an actively mode-locked three-mirror semiconductor laser

Various oscillation regimes of an actively mode-locked semiconductor laser are studied experimentally. Two types of regimes are found in which the minimal spectral width (~3.5 kHz) of intermode beats is achieved. The width of the optical spectrum of modes is studied as a function of their locking and the feedback coefficients. The maximum width of the spectrum is ~3.7 THz.