Efficient Selection of High-Order Laguerre–Gaussian Modes in a Q-Switched Nd : YAG Laser

Intra-cavity binary phase elements are incorporated into a -switched Nd : YAG laser resonator to obtain efficient high-order transverse mode selection. The resonator configuration is analyzed using the propagation-matrix diagonalization method and the Fox–Li algorithm, and a simple model for predicting the relative output powers of the selected modes is developed. The predicted results are verified experimentally with binary phase elements for selecting the TEM01, TEM02 and TEM03, degenerate Laguerre–Gaussian modes. The output energy per pulse was 15 mJ for the TEM01, 16.5 mJ for TEM02 and 18.3 mJ for TEM03, all higher than the 10mJ for the TEM00. The performance in -switched operation was found to be similar to that in free-running operation. The numerical calculations, experimental procedure and experimental results are presented.