Generation of Higher Order Vortex Beams From a YVO<sub>4</sub>/Nd:YVO<sub>4</sub> Self-Raman Laser via Off-Axis Pumping With Mode Converter

Abstract

The generation of high-order Hermite-Gaussian (HG) beams at the Stokes wavelength in a YVO4 /Nd:YVO4 self- Raman laser with off-axis pumping is demonstrated. The high- order vortex beams at the Stokes field are successfully created by transforming these HG modes via an extra-cavity mode converter. The stimulated Raman scattering (SRS) threshold pump power for the diode-end-pumped laser is theoretically analyzed to verify the feasibility of generating high-order HG modes by off-axis pump- ing. At a pump power of 18.6 W, the SRS output powers can be higher than 1.0 W for the HG modes from TEM0 ,0 to TEM3 ,0 . Under the same pump power, the maximum order can be up to TEM 28 ,0 . Index Terms—Optical vortices, Raman scattering, diode pump- ing, Beam transformation.