Second-Harmonic Generation of the Vortex Beams with Integer and Fractional Topological Charges

The single-pass second-harmonic generation (SHG) of a vortex beam under low fundamental wave depletion is systematically studied. Vortex modes at 1064 nm with integer topological charges from ±1 to ±9 and fractional ones ±0.75 are generated by modulating the Gaussian different spiral phase plates. frequency doubling these realized via SHG through KTP. A detailed theoretical model set up in beams. Theoretical analysis indicates that higher order beams, lower efficiency, when waists power given. experimentally measured output characteristics verify those obtained analysis. Conservation orbital angular momentum during process also verified, regardless or SH LG0,2l beams high mode purity obtained. fundamental/SH KTP using 4f system demonstrate Rayleigh ranges same. paper comprehensively presents some basic laws beam. In addition, it an effective method improve