A multi-clad optical fiber design is described in order to provide low optical loss, a high numerical aperture (NA), and high optical gain for the fundamental propagating mode, the linearly polarized (LP) 01 mode in the UV and visible portion of the optical spectrum. The optical fiber design may contain dopants in order to simultaneously increase the optical gain in the core region while avoiding additional losses during the fiber fabrication process. The optical fiber design may incorporate rare-earth dopants for efficient lasing. Additionally, the modal characteristics of the propagating modes in the optical core promote highly efficient nonlinear mixing, providing for a high beam quality (M.sup.2<1.5) output of the emitted light.

In various embodiments, the beam parameter product and/or beam shape of a laser beam is adjusted by directing the laser beam across a path along the input end of a cellular-core optical fiber. The beam emitted at the output end of the cellular-core optical fiber may be utilized to process a workpiece.

The optical fibers disclosed is a single mode optical fiber having a core region and a cladding region surrounding and directly adjacent to the core region. The core region can have a radius r.sub.1 in a range from 3.0 microns to 6.0 microns and a core volume V.sub.1 less than 6.0%-micron.sup.2. The cladding region can include a first outer cladding region and a second outer cladding region surrounding and directly adjacent to the first outer cladding region. The first outer cladding region can have a radius r.sub.4a, the second outer cladding region can have a radius r.sub.4b less than or equal to 65 microns and comprising silica based glass doped with titania. The disclosed single mode optical fiber can have a fiber cutoff wavelength λ.sub.CF less than 1530 nm.

In various embodiments, optical fibers have arrangements of core, annular core, and cladding regions enabling variation of beam shape and/or beam parameter product and may be utilized for the processing (e.g., welding, cutting, drilling, etc.) of various workpieces.

In various embodiments, the beam parameter product and/or beam shape of a laser beam is adjusted by directing the laser beam across a path along the input end of a cellular-core optical fiber. The beam emitted at the output end of the cellular-core optical fiber may be utilized to process a workpiece.

The present disclosure relates more to mode mixing optical fibers useful, for example in providing optical fiber laser outputs having a desired beam product parameter and beam profile. In one aspect, the disclosure provides a mode mixing optical fiber for delivering optical radiation having a wavelength, the mode mixing optical fiber having an input end, an output end, a centerline and a refractive index profile, the mode mixing optical fiber comprising: an innermost core, the innermost core having a refractive index profile; and a cladding disposed about the innermost core, wherein the mode mixing optical fiber has at least five modes at the wavelength, and wherein the mode mixing optical fiber is configured to distribute a fraction of the light input at its input end from its lower-order modes to its higher-order modes.

Laser waveguides, methods and systems for forming a laser waveguide are provided. The waveguide includes an inner cladding layer surrounding a central axis and a glass core surrounding and located outside of the inner cladding layer. The glass core includes a laser-active material. The waveguide includes an outer cladding layer surrounding and located outside of the glass core. The inner cladding, outer cladding and/or core may surround a hollow central channel or bore and may be annular in shape.

A wave guide may have an index profile including at least one maximum. The maximum or maxima of the index profile may correspond respectively to at least one maximum intensity of the outlet radiation with a mode of desired order. The wave guide may also have at least one doping ion configured to absorb the pump radiation. The doping ion or ions may have a concentration profile of doping ions including at least one maximum.

In various embodiments, the beam parameter product and/or beam shape of a laser beam is adjusted by directing the laser beam across a path along the input end of a cellular-core optical fiber. The beam emitted at the output end of the cellular-core optical fiber may be utilized to process a workpiece.

An anti-resonant hollow core optical fiber having multiple resonant layers. The optical fiber comprises a low-refractive index core region (1) and a high-refractive index cladding region. The high-refractive index cladding region comprises an inner cladding region (4) and an outer cladding region (5). The outer cladding region (5) clads the inner cladding region (4) and the core region (1). The inner cladding region (4) comprises a first anti-resonant layer (2) and a second anti-resonant layer (3), and the first anti-resonant layer (2) and the second anti-resonant layer (3) surround the core region (1); and the first anti-resonant layer (2) comprises several layers of microcapillary tubes, and the second anti-resonant layer (3) supports the first anti-resonant layer (2). The optical fiber adopts a double-cladding structure and uses two or more anti-resonant layers such that theoretically simulated loss is reduced to 0.1 dB/km, and has the features of ultralow transmission loss, wide spectral bandwidth, low bending loss, low transmission loss, high damage threshold and single-mode transmission.