Laser mode selection with intracavity phase elements

Several methods for operating a laser with a single high-order transverse mode are presented. These methods are based on the insertion of binary and spiral phase elements within the laser resonator, so as to introduce high losses to the undesired modes and low losses to the desired mode, as well as controlling the phases of the various lobes of the high order mode distribution. The basic principles and experimental results are presented, demonstrating efficient high order mode selection in various Nd:YAG and CO₂ laser configurations, where the far-field intensity distribution is comprised mainly of a dominant main lobe. The experiments were performed with low gain CW lasers as well as short-pulse-high-gain Q-switched lasers.