Generation of higher-order Laguerre–Gaussian modes from a diode-pumped Pr³⁺:LiYF₄ laser with an intra-cavity spherical aberration

Abstract

We demonstrate, for the first time to the best of our knowledge, the direct generation of higher-order Laguerre–Gaussian (LG) petal modes, formed of the coherent superposition of positive and negative LG modes with the topological charge of ± ℓ as an eigen mode, from a compact diode end-pumped P r 3 + : L i Y F 4 (YLF) laser with an intra-cavity lens configuration. The on-axis displacement of the intra-cavity lens with spherical aberration allows the selective operation of the desired higher-order LG modes with | ℓ | ≤ 31 from the laser cavity at 640 nm and 607 nm. Such visible higher-order LG modes will offer new applications in optical manipulation, quantum/optical underwater telecommunication, and microfabrication.

Direct generation of higher-order vector vortex modes at 640 nm from a Pr3+:YLF laser source

“…2. The generated vector vortex modes exhibited typically a flower-shaped spatial form with 2ℓ petals, manifesting the coherent superposition of degenerated positive and negative LG modes with the same topological charge ℓ, as mentioned in our previous higher-order scalar vortex generation work 9 , and it was also evidenced by linearly polarized twin-lobe modes obtained by employing the polarization analysis. The output power of higher order vector vortex modes was typically measured to be 10 mW at the maximum pump power of 3 W.…”

Visible skyrmion praseodymium laser in red and orange

“…The basic laser cavity configuration followed that of a previous laser design. 13 It used an a-cut Praseodymium: Yttrium-Lithium-Fluoride (Pr:YLF) gain medium (0.5 at.% doping, 3 mm long, 3 mm square aperture), which was end pumped by two polarisation combined blue diode lasers at 442 nm with a maximum combined power of 4.2 W. The Pr:YLF crystal had a dichroic coating that transmitted pump light and was highly reflecting at the laser wavelengths, which formed the rear mirror of the oscillator. Two crystals with different rear coating properties were used to obtain orange (607 nm) and red (640 nm) lasing, with each crystal being highly reflective for the corresponding lasing wavelength.…”

A conceptual review on Bessel beams

“…For example, by inserting an axicon within the laser cavity [242] or by intra-cavity thermal effects [243] we can generate Bessel-like beams with high-mode quality. The strong-intra-cavity spherical aberration can be used to generate a tunable Bessel-like beam [244,245]. Fibers generally have high mode purity and can also be used to generate Bessel-like beams by fabricating micro-axicons on fiber tip [246,247] or by multimode interference within the fiber [248].…”