Amplified spontaneous emission in disk lasers

Amplified spontaneous emission(ASE) and parasitic oscillation in laser resonators exhibit distinct physical properties. An analytic method is employed to find eigenmodes of disk medium. These modes processes some non-trivial dispersion relations, which allow few stable longitudinal modes only. It decreases amplifying rate of parasitic oscillation in mode competition with main laser. A numerical model is further proposed to perform (3+1) dimensional simulations. Ray tracing method, together with finite-difference in time domain and Fox-Li type iteration, are used to solve a set of coupled equations. Transverse mode competition between ASE/parasitic oscillations and main laser increases threshold to establish laser oscillation and decreases output power as well. Time evolution of laser outpu