Abstract
We have demonstrated the first direct femtosecond vortex beam generation from a semiconductor saturable absorber mirror (SESAM) mode locked Yb:KYW oscillator, featuring a homemade defect-spot mirror. Experimentally, a Laguerre Gaussian LG01 vortex beam with a repetition rate of ∼103.5 MHz and a pulse duration of 298 fs has been obtained. Both the defect mirror induced spatial loss modulation and intra-cavity astigmatism are responsible for the doughnut mode generation. Further, the chirality of the vortex beam is controlled by slightly tilting the angle of the Yb:KYW crystal, which hence breaks the azimuthal symmetry inside the laser cavity and leads to differential losses for LG0,+1 and LG0,-1 modes. The potential of the vortex beam’s amplification by a 2-m long Yb-doped double cladding fiber (DCF) amplifier has also been demonstrated.
Published Version
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