Fig. 1. Schematic showing the layout of the system used to generate mid-infrared high-order LG modes from a vortex-pumped optical parametric oscillator.

Fig. 2. Images showing the spatial intensity distribution of (a) the free-space and (b) focused (through a tilted lens) pump vortex beam with OAM = 1. Images of the spatial intensity distribution of (c) the free space and (d) focused (through a tilted lens) signal beam. (e₁)–(e₆) The experimentally obtained spatial profiles of the idler beam for a range of cavity lengths. (f₁)–(f₆) The corresponding theoretically modeled spatial intensity profiles of these beams.

Fig. 3. A collection of images showing the spatial intensity profiles of modes generated when the OPO is pumped with vortex modes of order ℓ=2 and 3. (a) and (b) The free-space and focused (through a tilted lens) pump vortex beam with ℓ=2, respectively. (c) and (d) The corresponding profiles of the generated signal field. (e₁)–(e₉) The free-space spatial intensity profiles of the generated idler field, for a range of resonant cavity lengths. (f₁)–(f₉) The corresponding theoretically modeled mode profiles. (g) and (h) The free-pace and focused (through a tilted lens) pump vortex beam with ℓ=3, respectively. (i) and (j) The corresponding profiles of the generated signal field. (k₁)–(k₁₁) Free-space spatial intensity profiles of the generated idler field, for a range of resonant cavity lengths. (l₁)–(l₁₁) The corresponding theoretically modeled mode profiles.

Fig. 4. Plots of the theoretically modeled spatial overlap efficiency as a function of resonant cavity mode order (ℓ) for pump vortex beams with topological charge ℓp of 1 – 3.

Fig. 5. Plots showing the output energies of the signal and high-order LG mode idler fields as a function of incident pump energy and for different resonant cavity lengths. Panel (a) shows results using a pump vortex beam with ℓp=1; panel (b) shows results using a pump vortex beam with ℓp=2; and panel (c) shows results using a pump vortex beam with ℓp=3.

Fig. 6. Plots of the output signal (1535 nm) and idler (3468 nm) field spectra; insets are zoomed spectra highlighting the spectral bandwidth of each field.