A multilayer mirror, ring laser gyroscope and method are disclosed. For example, the multilayer mirror includes a plurality of alternating layers of a high index of refraction optical material and a low index of refraction optical material, an amplification layer of an optical material disposed on the plurality of alternating layers, and a coating of an anti-reflective material disposed on an outermost surface of the optical material amplification layer.

A solid-state optical amplifier is described, having an active core and doped cladding in a single chip. An active optical core runs through a doped cladding in a structure formed on a substrate. A light emitting structure, such as an LED, is formed within and/or adjacent to the optical core. The cladding is doped, for example, with erbium or other rare-earth elements or metals. Several exemplary devices and methods of their formation are given.

An amplification optical fiber includes: a core; an inner cladding having a refractive index lower than a refractive index of the core, wherein an active element pumped by pumping light is entirely doped to the core, and a relative effective refractive index difference of light in an LP01 mode is greater than or equal to 0.05% and a relative effective refractive index difference of light in an LP21 mode is less than 0.05% in light propagating through the core.

An apparatus includes a PWG having a core region and a cladding layer. The amplifier is configured to receive pump light. The core region is configured to amplify an input beam using energy from the pump light to generate an amplified output beam. The apparatus also includes a cooling fluid configured to cool the core region. The cooling fluid has a lower refractive index than the core region and the cladding layer in order to support guiding of the input beam and pump light within the amplifier. The amplifier also includes first and second endcaps attached to opposite faces of the core region and cladding layer. The core region, cladding layer, and endcaps collectively form a monolithic fused structure. Each endcap has a major outer surface that is larger in area than a combined area of the faces of the core region and cladding layer to which the endcap is attached.

A high-power Raman fiber laser includes: a seed laser; a plurality of pump lasers, each including a cladding and comprising of thulium-doped fiber laser (TDFL) and configured to operate in a 1935-2020 nm spectral window; a pump/seed combiner to combine outputs of the pump lasers and output of the seed laser and having a tapered portion including a cladding; and a Raman fiber amplifier having a core and a cladding surrounding the core, the seed laser is launched into the core, and pump laser output beams are launched into the cladding, to amplify the seed laser to produce an amplified output signal, and a brightness of the cladding of the Raman fiber amplifier is matched to a combined brightness of the plurality of pump lasers.

A laser amplifier includes a volume configured to receive pump light from an array of laser diodes pump source, and a gain medium arranged within the volume and configured to amplify light in response to receiving the pump light. The gain medium comprises a first solid-state element configured to emit a first laser radiation having a peak centered at a first peak fluorescence wavelength and a second solid-state element configured to emit a second laser radiation having a peak centered at a second peak fluorescence wavelength. Each of the first and the second solid-state elements contain respective active laser ions. The difference between the first peak fluorescence wavelength and the second peak fluorescence wavelength is larger than or equal to 10 nm and smaller than or equal to 60 nm. The first solid-state element and the second solid-state element are cooled, for instance fluid-cooled.

A rare earth-doped optical fiber comprises a fluorosilicate core surrounded by a silica cladding, where the fluorosilicate core comprises an alkaline-earth fluoro-alumino-silicate glass, such as a strontium fluoro-alumino-silicate glass. The rare earth-doped optical fiber may be useful as a high-power fiber laser and/or fiber amplifier. A method of making a rare earth-doped optical fiber comprises: inserting a powder mixture comprising YbF.sub.3, SrF.sub.2, and Al.sub.2O.sub.3 into a silica tube; after inserting the powder mixture, heating the silica tube to a temperature of at least about 2000 C., some or all of the powder mixture undergoing melting; drawing the silica tube to obtain a reduced-diameter fiber; and cooling the reduced-diameter fiber. Thus, a rare earth-doped optical fiber comprising a fluorosilicate core surrounded by a silica cladding is formed.

An optical fiber includes: an optical waveguide; and a resin coating that is lower in refractive index than the optical waveguide and covers a side surface of the optical waveguide except in a coating-removed section of the side surface. The coating-removed section of the side surface is covered throughout with an inorganic layer that is lower in refractive index than the optical waveguide.

Fiber lasers and methods are provided, in which the modal instability threshold is raised to provide more laser power. Fiber lasers comprise an active optical fiber having at least one absorption peak wavelength (.sub.peak) and capable of supporting more than a fundamental mode during operation, and a plurality of pump diodes connected to deliver radiation emitted thereby into the optical fiber. At least one of the pump diodes is a wavelength-locked (WL) diode and at least one of the pump diodes is configured to deliver radiation at at least (not necessarily the same diode(s)). The pump diodes may comprise any of WL diode(s) at .sub.peak, WL diode(s) at =.sub.peak and non-WL diode(s). Pumping radiation off the fiber's absorption peak increases the modal instability threshold, most likely by reducing the temperature gradient in the active fiber at the fiber pump entrance point and along the fiber.

An apparatus includes a PWG having a core region and a cladding layer. The amplifier is configured to receive pump light. The core region is configured to amplify an input beam using energy from the pump light to generate an amplified output beam. The apparatus also includes a cooling fluid configured to cool the core region. The cooling fluid has a lower refractive index than the core region and the cladding layer in order to support guiding of the input beam and pump light within the amplifier. The amplifier also includes first and second endcaps attached to opposite faces of the core region and cladding layer. The core region, cladding layer, and endcaps collectively form a monolithic fused structure. Each endcap has a major outer surface that is larger in area than a combined area of the faces of the core region and cladding layer to which the endcap is attached.