Abstract

Nowadays laser beams are used in a great number of application areas such as industry, medicine, defence, telecomm and so on. Each area requires unique beam properties depending on its application and especially the spatial intensity distribution is one of the most important factors to determine its performance. In general, the spatial intensity distribution of the laser beam is determined by a transverse mode in an optical resonator, a Hermite-Gaussian (HG) mode in rectangular configurations and a Laguerre-Gaussian (LG) mode in cylindrical configurations [1]. Since both transverse modes have quite different intensity distribution, it is difficult to switch the transverse mode between them in one laser configuration and hence most of the laser systems are optimized to generate one mode only, especially lowest order mode (TEM₀₀) or the first-order LG mode (LG₀₁). Some techniques have been developed to switch the generated transverse mode in the resonator. Inserting a spatial light modulator can convert one mode to the other but at the expense of severe power loss and efficiency. Tailoring the pump beam for the targeted beam is an alternative way to select the generated mode but a special optical device, e.g. hollow fibre, is required for generating the ring mode [2].

© 2015 IEEE