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 laser system and method generate milliwatt-power pump light by a fiber-coupled laser diode with a single-mode integrated fiber housed in a pump enclosure. The milliwatt-power pump light is conveyed from the single-mode integrated fiber out of the first enclosure into one end of a single-mode fiber cable that is external to the pump enclosure. The milliwatt-power pump light is conveyed from an opposite end of the external single-mode fiber cable into one end of a single-mode resident fiber disposed internally within a laser-head enclosure. A crystal housed in the laser-head enclosure is pumped with the milliwatt-power pump light that exits into free space from an opposite end of the single-mode resident fiber onto a face of the crystal, to produce stable milliwatt-power single-mode laser light having a frequency stability of less than 3 MHz per minute. The stable milliwatt-power single-mode laser light is emitted from the laser-head enclosure.

Provided is a differential modal attenuation compensation fiber that has a simple structure and can reduce MDL while eliminating the need for precise alignment work, an optical amplifier, and a transmission line design method. The differential modal attenuation compensation fiber according to the present invention, imparts excess loss to a desired propagation mode by forming a cavity portion or a ring-shaped high refractive index portion in a core of an optical fiber. By forming the cavity portion or the ring-shaped high refractive index portion in a part of the profile of the core, electric field distribution of a particular mode propagating through the fiber can be controlled, and different losses can be imparted to different propagation modes at an interface between the cavity portion or the ring-shaped high refractive index portion and a region not including the cavity portion or the ring-shaped high refractive index portion.

An apparatus and method for cooling an optical fiber, comprising impinging electromagnetic radiation from a laser on an optical fiber comprising a core, in which the electromagnetic radiation is substantially confined, and a cladding, in thermal communication with the core, configured to provide optically activated cooling of the core via the electromagnetic radiation from the laser.

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.

A method of manufacturing an optical fiber is provided. The method involves providing a fiber preform with an active core and a pump-guiding cladding, and assembling one or more side rods to the fiber preform. The side rods extend longitudinally along an outer surface of the pump-guiding cladding. The resulting fiber preform assembly is drawn into the optical fiber. Each side rod defines a longitudinal protrusion extending along the optical fiber. Each longitudinal protrusion may have a cross-section forming a middle bump projecting radially away from the outer surface of the pump-guiding cladding and smooth transition regions with this outer surface of the pump-guiding cladding on opposite sides of the middle bump.

Provided is a method for producing a crystal fiber which can suppress the occurrence of stress birefringence even while distributing a light emission center so as to concentrate on a cross-sectional middle portion. The method for producing a crystal fiber comprises the steps of: using, as a preform, the crystal fiber comprising a light emission center that volatilizes from a melted portion upon the melting of a crystal, and heating a portion or a plurality of portions of the side of the preform, whereby the portion or the plurality of portions of the preform are melted such that only a given amount of the inside of the portion or the plurality of portions of the preform is not melted, to form the melted portion; and sequentially transferring the melted portion in the longitudinal direction of the preform, and cooling the melted portion, whereby the melted portion is continuously recrystallized to form a recrystallized region.

An optical fiber may include a core in which core-guided light generated by one or more light sources propagates along a length of the at least one optical fiber, one or more claddings, surrounding the core, to guide cladding-guided light generated by the one or more light sources along the length of the at least one optical fiber, and a reflector structure machined into the at least one optical fiber. The reflector structure may include multiple angled facets arranged at one or more respective angles relative to an axis of the optical fiber to reflect at least a portion of the core-guided light and/or the cladding-guided light passing through the optical fiber.

A fiber amplification system is provided for amplifying a laser pulse signal, e.g., an oscillator signal of an oscillator device. The fiber amplification system includes a fiber pre-amplification system having a short, fundamental-mode and step-index fiber configured to pre-amplify the laser pule signal to generate a seed signal and a main amplification system having a large core fiber configured to amplify the seed signal. The short, fundamental-mode step-index fiber can have a length no longer than about 30 cm, and a mode field diameter no less than about 30 μm, e.g., in a range from 30 μm to 60 μm, as well as a high doping concentration needed to provide an absorption length no more than about 30 cm, for providing the seed signal for the large core fiber with low non-linearity.

A laser system has a fiber cable, a pump enclosure connected to the fiber cable outside of the pump enclosure, and a laser-head enclosure connected to the fiber cable disposed outside of the laser-head enclosure. The pump enclosure houses a fiber-coupled laser diode configured to produce and convey pump light through the pump enclosure out to the fiber cable. The laser-head enclosure houses a crystal. The pump light, when produced by the laser diode, propagates out from the pump enclosure through the fiber cable into the laser-head enclosure and into the crystal. The crystal produces a laser beam in response to the pump light. The integrated fiber of the laser diode, the fiber cable, and internal fiber of the laser-head enclosure, through which the pump light propagates, may be single-mode fibers, to achieve superior laser system performance with lower frequency and intensity noise than pumping through multimode fibers.