Efficient selection of high-order Laguerre-Gaussian modes in a Q-switched Nd:YAG laser

Intra-cavity binary phase elements are incorporated into a Q-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 TEM/sub 01/, TEM/sub 02/ and TEM/sub 03/, degenerate Laguerre-Gaussian modes. The output energy per pulse was 15 mJ for the TEM/sub 01/, 16.5 mJ for TEM/sub 02/ and 18.3 mJ for TEM/sub 03/, all higher than the 10 mJ for the TEM/sub 00/. The performance in Q-switched operation was found to be similar to that in free-running operation. The numerical calculations, experimental procedure and experimental results are presented.