Intensity fluctuations of radiation from multimode solidstate lasers with modulated resonator losses

The response of the radiation intensity of a solid-state laser to modulation of the resonator losses is analyzed using linearized rate equations. Resonance curves of the intensity response of individual modes and of the total radiation from a two-mode laser are obtained using the small-parameter method in the matrix form. It is shown that in addition to a main resonance at a frequency characteristic of a singlemode laser, there is also a low-frequency resonance. The height of this low-frequency resonance in the total intensity is appreciably lower than that in each of the modes. A multimode laser has a group of lowfrequency resonances. An analysis is made of the effect of the relative phases of modulation of the mode losses and it is shown that, for constant-phase modulation of the losses, a multimode laser behaves as a single-mode laser. An experimental investigation was made of a YAG:Nd³⁺ laser and this supported the theoretical conclusions. The conditions for establishment of stable regular pulsations at the relaxation frequency are discussed.