Calculated Simulation of Modes for Active Cavity

Using Fox-Li iterative method and split step Fourier transform, the active cavity modes of uniform and non-uniform gain have been simulated and studied.. In the calculation, the output coupling mirror loss, the diffraction loss and the inner-cavity loss, have been taken into consideration. The calculation results indicate that in the condition of uniform gain, small signal gain coefficient (SSG) increasing, higher order modes' gain are greater than loss. The output power increases and laser beam quality gets worse. In the condition of non-uniform gain, the mode near threshold is symmetric distribution. When the gain gets increasing, light intensity increases, non-uniform pump impact of the mode field increasingly evident. Mode field peak offsets to the pump direction and beam quality gets worse.