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.