Resonant modes analysis of a FP cavity under different laser alignment conditions

Ultra-stable lasers (USLs) based on Fabry-Perot (FP) cavities frequency stabilization take TEM00 mode as the reference frequency. When the laser does not match the FP cavity perfectly, high-order modes will be excited, affecting the performance of USLs. In this paper, influence of different laser alignment conditions on resonant modes of a FP cavity was numerically analyzed using Optical Simulation Containing Ansys Results (OSCAR) code. The relationship between energies of resonant modes and different laser incident conditions was revealed. The results can be a guide for aligning lasers and FP cavities.