Fig. 1. (a) Principle of the spatio-temporal OFW beam transfer by nonlinear wave mixing. Experimental setup of (b) pulse-to-pulse interferometer and (c) spatio-temporal OFW beam transfer. OFC, optical frequency comb; M, high-reflection mirror; HWP, half-wave plate; PBS, polarization beam splitter; AOM, acousto-optic modulator; BB, beam block; HRM, hollow roof mirror; BS, beam splitter; QWP, quarter-wave plate; VWP, vortex wave plate; L, lens; F, filter; CCD, charge coupled device.

Fig. 2. Theoretical simulation results of generated blue–violet beam by the FWM process. (a) Spatial intensity and phase distribution of blue–violet beam with Δl=4, 6, 8, 12, and 18, respectively. (b) Temporal evolution of blue–violet beam azimuthal profile with Δl=4 and Δl=6, respectively.

Fig. 3. Experimental intensity profiles of the vortex comb beams with different topological charges (a) l1=1, 2, 3, 5, 7, and 9 and (b) l2=−1, −2, −3, −5, −7, and −9, respectively. Spatial distribution of (c) input 776 nm probe spatio-temporal OFW beams and (d) output 420 nm signal beams with topological charge difference Δl=2, 4, 6, 10, 14, and 18, respectively.

Fig. 4. Temporal characteristic transfer of spatio-temporal OFW beam with Δl=6 when Δf=2  Hz and Δf=−2  Hz, respectively. (a) and (c) show the rotating patterns imaged of 776 nm probe and 420 nm signal beams. (b) and (d) show the azimuthal angle for the beam maximum intensity ϕmax as a function of the rotation time.

Fig. 5. Rotation velocities of (a) input probe vp and (b) output signal vs beams as a function of Δf with Δl=2, 4, 6, 10, and 18, respectively. The dots represent the experimental results, and the lines refer to the theoretical fitting results.