Fig. 1. Schematic of the infrared vortex laser system. BS, beam splitter; L, lens; YAG, yttrium aluminum garnet crystal; DM, dichroic mirror; SPP, spiral phase plate; BBO, BaB₂O₄.

Fig. 2. (a) Simulated phase-matching spectrum of the OPA process. (b) Spectra of the signal and the idler. (c) Calculated FTL pulse shapes of the signal and the idler.

Fig. 3. (a) Spatial profile of the amplified 1.45 μm vortex output. (b) Self-interference fringes of the amplified 1.45 μm vortex. (c) Spatial profile of the amplified 1.8 μm vortex output. (d) Self-interference fringes of the amplified 1.8 μm vortex.

Fig. 4. Temporal and spectral characterizations of the output pulses. (a) The pulse temporal profile of the duration (blue curve) and phase (orange curve) of the signal light at 1450 nm. (b) Reconstructed spectrum of the SHG-FROG (blue curve) and phase (orange curve) of the signal light at 1450 nm. (c) Measured and reconstructed SHG-FROG traces of the signal light at 1450 nm. (d) The pulse temporal profile of the duration (blue curve) and phase (orange curve) of the idler light at 1800 nm. (e) Reconstructed spectrum of the SHG-FROG (blue curve) and phase (orange curve) of the idler light at 1800 nm. (f) Measured and reconstructed SHG-FROG traces of the idler light at 1800 nm.

Fig. 5. (a) Spectral stability of output pulses at 1450 and 1800 nm. (b) Spectral fluctuation of output pulses at 1800 nm. (c) Spectral fluctuation of output pulses at 1450 nm. (d) Energy stability of signal pulses (red dot) and idler pulses (blue dot).