A multi-clad optical fiber is provided. The fiber includes, concentrically and radially outwards from the center of the optical fiber, a core doped with at least one rare-earth dopant material, a pedestal cladding structure, an inner cladding and an outer cladding. The pedestal cladding structure includes a pedestal layer having a refractive index smaller than a refractive index of the core, and a raised index layer having a refractive index larger than the refractive index of the pedestal layer. The raised index layer has a thickness and a refractive index which preserve the confinement of the core mode in the core and minimize the overlap of one or more pedestal modes with the core.

An optical fiber may comprise a core doped with one or more active ions to guide signal light from an input end of the optical fiber to an output end of the optical fiber, a cladding surrounding the core to guide pump light from the input end of the optical fiber to the output end of the optical fiber, and one or more inserts formed in the cladding surrounding the core. The core may have a geometry (e.g., a cross-sectional size, a helical pitch, and/or the like) that varies along a longitudinal length of the optical fiber, which may cause an absorption of the pump light to be modulated along the longitudinal length of the optical fiber.

A system including an erbium doped fiber amplifier (EDFA), comprising a length of erbium doped fiber having a first end and a second end, an isolator wavelength division multiplexer (IWDM) comprising an output optically connected at an optical connection with the first end of the erbium doped fiber, wherein the optical connection with the first end of the erbium doped fiber is continuous between the IWDM and the first end of the erbium doped fiber, and an isolator comprising an input optically connected at an optical connection with the second end of the erbium doped fiber.

An optical fiber for a fiber laser includes a core to which a rare-earth element is added, a first cladding formed around the core; and a second cladding formed around the first cladding, and excitation light is guided from at least one end of the first cladding to excite the rare-earth element to output a laser oscillation light. An addition concentration of the rare-earth element to the core is different in a longitudinal direction of the optical fiber for a fiber laser, and a core diameter and a numerical aperture of the optical fiber for a fiber laser are constant in the longitudinal direction of the optical fiber for a fiber laser.

A fiber-based optical amplifier for operation at an eye-safe input signal wavelength λ.sub.S within the 2 μm region is formed to include a section of Holmium (Ho)-doped optical gain fiber. The pump source for the fiber amplifier is particularly configured to provide pump light at a wavelength where the absorption coefficient of the Ho-doped optical gain fiber exceeds its gain coefficient (referred to as an “absorption-dominant pump wavelength”), and is typically within the range of 1800-1900 nm. The selection of an absorption-dominant pump wavelength limits the spontaneous emission of the pump from affecting the amount of gain achieved at the higher wavelength end of the operating region. The amount of crosstalk between the signal wavelength and pump wavelength is also reduced (in comparison to using the conventional 1940 nm pump wavelength).

The invention relates to an optical system with a dividing element (2), which divides the input laser beam (EL) into a number of spatially separate sub-beams, at least one optical amplifier (4), through which the spatially separate sub-beams propagate, at least one path-length adjustment element (3), which adjusts the path length of at least one of the sub-beams, and a combination element (6, 8), which coherently superimposes the sub-beams in an output laser beam. The object of the invention is to achieve a high beam quality in the output laser beam, wherein the demands on the surface quality of the optical components used are to be reduced compared with the prior art. To this end the invention proposes that at least one optical functional element (5, 5′, 6′, 7) from the group of transport element, spectral broadening element, beam deflection element, optical isolator, optical modulator and pulse compressor is provided arranged after the at least one optical amplifier (4) in the beam path, through which functional element the spatially separate sub-beams propagate.

A broadband optical amplifier for operation in the 2 μm visible wavelength band is based upon a single-clad Ho-doped fiber amplifier (HDFA). A compact pump source uses a combination of discrete laser diode with a fiber laser (which may be a dual-stage fiber laser) to create a pump output beam at a wavelength associated with creating gain in the presence of Ho ions (an exemplary pump wavelength being 1940 nm). The broadband optical amplifier may take the form of a single stage amplifier or a multi-stage amplifier, and may utilize a co-propagating pump and/or a counter-propagating pump arrangement.

Methods for synthesizing fibers having nanoparticles therein are provided, as well as preforms and fibers incorporating nanoparticles. The nanoparticles may include one or more rare earth ions selected based on fluorescence at eye-safer wavelengths, surrounded by a low-phonon energy host. Nanoparticles that are not doped with rare earth ions may also be included as a co-dopant to help increase solubility of nanoparticles doped with rare earth ions in the silica matrix. The nanoparticles may be incorporated into a preform, which is then drawn to form fiber. The fibers may beneficially be incorporated into lasers and amplifiers that operate at eye safer wavelengths. Lasers and amplifiers incorporating the fibers may also beneficially exhibit reduced Stimulated Brillouin Scattering.

A system includes a seed laser configured to generate a seed beam and multiple arrays of semiconductor diode lasers configured to generate multiple pump beams. The system also includes a Raman amplifier having a core, a first cladding around the core, and at least a second cladding around the first cladding. The core is configured to amplify the seed beam based on optical pump power provided by the pump beams. Each of the core, the first cladding, and the second cladding includes fused silica, and at least the core and the first cladding are doped. The core has a numerical aperture of approximately 0.06 or less and a diameter of approximately 20 μm to approximately 25 μm. The first cladding has a numerical aperture of approximately 0.17 or less and a diameter of approximately 35 μm to approximately 45 μm.

Disclosed is an all-fiber optical vortex laser based on resonance of orbital angular momentum modes. The all-fiber optical vortex laser has an annular cavity structure, and includes a narrow-linewidth pump laser, an optical amplifier, an orbital angular momentum mode generator, a first polarization controller, an optical fiber circulator, an optical fiber coupler, a second polarization controller and a vortex optical fiber. The orbital angular momentum mode generator (3) realizes directional conversion from a fundamental transverse mode in a single-mode optical fiber into an orbital angular momentum mode with a specific topological charge in a vortex optical fiber. The optical fiber coupler can realize directional coupling from an orbital angular momentum mode in one vortex optical fiber to an orbital angular momentum mode in another vortex optical fiber; the vortex optical fiber is an optical fiber supporting stable transmission of an orbital angular momentum model.