On the influence of spatial hole-burning on mode selection and mode synchronization in a CW laser

The single-mode operation and mode synchronization of a laser with a Fabry-Perot resonator are investigated with emphasis to the effect of spatial hole-burning and the resulting Bragg reflections. It is found that single-frequency operation in this type of laser can be achieved if the loss difference between the mode to be selected and modes to be quenched is proportional to the Bragg losses of the selected mode due to scattering at a self-induced grating. The proportionality factor depends on the length and position of the amplifier in the resonator. In the case of a short amplifier and a short absorber inside the resonator, it is shown that for certain positions of the amplifier inside the resonator, its effect on the frequency behavior of the modes can be neglected.