DEVELOPMENT OF EM FIELD IN LASERS WITH ROTATING MIRROR Q-SWITCH

A fast-Fourier-transform (FFT) computational scheme based on a Fourier expansion technique is developed to calculate the development of an e lectromagnetic (EM) field from spontaneous noise inside a loaded rotat ing mirror Q-switched laser. A rate equations analysis is also carried out, using FFT calculated dependence of the diffraction loss on the f ixed Q-switch mirror tilt angle. The computational results are compare d with the output characteristics of an ''eye safe'' (lambda = 1.54 mu m) erbium glass laser. The experiments are in good qualitative and qua ntitative agreement with the predictions of the FFT model. The model r eveals short-duration intense spatial regions, as well as two types of temporal modulations of the laser output pulses. The temporal modulat ions are attributed to the inhomogeneous development of the laser fiel d in the longitudinal and transverse laser resonator direction. These irregularities must be taken into account when calculating eye-safety levels of rotating mirror Q-switched lasers.