Direct generation of multicolor Bessel beams from a Pr3+: WPFG fiber laser.

Multicolor visible high-order Bessel (Bessel-vortex) beams which have a helical wavefront and a long confocal length have garnered significant interest for applications in materials processing and biomedical technologies. In this paper, we demonstrate the direct generation of multicolor (523, 605 and 637 nm) Bessel-vortex beams from a Pr3+-doped water-proof fluoro-aluminate glass (Pr3+: WPFG) fiber laser with an intracavity lens which induces chromatic and spherical aberration. The handedness of the generated Bessel-vortex beam is selectively controlled through lateral displacement of the intra-cavity lens.

Direct generation of lower-order cylindrical vector vortex modes from an end-pumped Pr3+:LiYF4 laser.

We report the direct generation of vector vortex laser modes at 640 nm from a compact, diode end-pumped continuous-wave P r 3+:L i Y F 4 (YLF) laser that utilizes an intracavity lens and diaphragm. On-axis displacement of the intracavity lens, combined with appropriate choice of the intracavity diaphragm, enables selective generation of a desired radial and azimuthal vector laser mode. Such compact, vector vortex laser sources based on P r 3+:Y L F in the visible wavelength region are a significant enabling technology for a wide range of applications.

Free-Form Optical Fiber with a Square Mode and Top-Hat Intensity Distribution.

The development of bend-induced effectively single-mode fiber with a square cross-section and flat top-hat intensity distribution is reported using core topology nanostructuring dedicated to femtosecond laser ablation systems. The fiber's core comprises 5419 silica and germanium-doped silica nanorods with a diameter of 430 nm each arranged into a hexagonal lattice. The distribution of the rods is calculated using in-house developed code based on the Monte Carlo algorithm to obtain a target shape of mode and intensity distribution. As a proof-of-concept, a silica nanostructured fiber with a 24 µm core is developed and verified against the purity of mode guidance, bending, and guiding losses. It is shown that for a wavelength of 1030 nm, the fiber is effectively single-mode with 96% mode purity when bending with a radius of 20 cm is applied. The fiber has a measured mode area of 360 µm2, numerical aperture of 0.03, and total losses of 0.07 dB m-1.