Selective generation of Laguerre-Gaussian (LG(0n)) mode output in a diode-laser pumped Nd:YAG laser

Direct excitation of an arbitrary Laguerre-Gaussian (LG(0n)) doughnut mode in an end-pumped solid-state laser using a fiber-based pump beam conditioning scheme to produce a ring-shaped inversion distribution is reported. An analytical expression for the dependence of threshold pump power for a particular LG(0n) mode on the spatial overlap with the pump beam is derived and shows that the desired LG(0n) mode can be selectively excited through simple adjustment of the pump beam dimensions. This approach has been applied to a diode-laser pumped Nd:YAG laser to achieve selective lasing on the LG(01), LG(02) or LG(03) mode. Predicted values for threshold pump power and beam propagation factor (M-2) are in good agreement with measured values. The prospects for further improvement in laser performance will be discussed. (C) 2013 Elsevier B.V. All rights reserved.This research was supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (2011-0022830), and by the Engineering and Physical Sciences Research Council (UK)