An example apparatus may include a first plate having a first side. A first plurality of fins may be integral with the first side of the first plate and protruding perpendicularly therefrom. The first plurality of fins may be arranged in first concentric circles separated radially by a first distance. The apparatus may also include a second plate having a first side. The second plate may be rotatably coupled to the first plate. A second plurality of fins may be integral with the first side of the second plate and protruding perpendicularly therefrom. The second plurality of fins may be arranged in second concentric circles separated radially by the first distance. Each fin of the second plurality of fins may interpose between adjacent fins of the first plurality of fins to transfer heat between the second plate and the first plate.

An example apparatus may include a first plate having a first side. A first plurality of fins may be integral with the first side of the first plate and protruding perpendicularly therefrom. The first plurality of fins may be arranged in first concentric circles separated radially by a first distance. The apparatus may also include a second plate having a first side. The second plate may be rotatably coupled to the first plate. A second plurality of fins may be integral with the first side of the second plate and protruding perpendicularly therefrom. The second plurality of fins may be arranged in second concentric circles separated radially by the first distance. Each fin of the second plurality of fins may interpose between adjacent fins of the first plurality of fins to transfer heat between the second plate and the first plate.

A bidirectional mode-locked fiber laser includes first and second passive optical fibers, a doped optical fiber, first and second polarization controllers, and first and second polarized beamsplitters that are arranged as a ring cavity with clockwise (CW) and counter-clockwise (CCW) directions. The laser imparts different nonlinear phase shifts in the CW and CCW directions, corresponding to CW and CCW repetition rates that are slightly different. When the normalized difference in repetition rates is less than approximately 10.sup.−5, both directions can be mode-locked simultaneously, thereby preventing one direction from inhibiting mode-locking of the other direction. Optical-fiber nonlinearity implements an intra-cavity bidirectional artificial saturable absorber based on nonlinear polarization rotation. The laser uses only components with normal group-velocity dispersion (GVD), thereby achieving higher pulse energies than mode-locked lasers utilizing negative GVD. The combination of artificial saturable absorber and normal GVD components increases pulse energy, which improves the efficiency of spectral broadening.

A fiber applied to an optical amplifier, where the fiber includes a rare earth-doped core and a cladding. The core includes a gain equalization unit. The core is configured to separately amplify optical signals of all wavelengths in a received multiplexing wave. The gain equalization unit is configured to equalize gains of the optical signals of all the wavelengths, such that gains of optical signals that are of all the wavelengths and that are transmitted from an egress port of the fiber all fall within a preset range, The gain of the optical signal of each wavelength in the optical signals of all the wavelengths is determined based on a ratio of power of an amplified optical signal to power of the unamplified optical signal.

A method of marking an optical fiber that includes directing a laser beam onto a first colored layer of an optical fiber. The optical fiber includes a core and a cladding surrounding the core, the first colored layer surrounds the cladding, and the laser beam modifies the first colored layer to form one or more laser-modified regions along an outer surface of the first colored layer.

A dielectric-grating waveguide free-electron laser device generating coherent or laser-like radiation is provided. An electron beam propagates next to a dielectric waveguide with a built-in grating structure to generate highly confined coherent or laser-like radiation in the waveguide through the Bragg resonance, the backward-wave resonance, or the Fabry-Perot resonance provided by the grating-waveguide structure. The dielectric-grating waveguide can be made of linear optical materials or nonlinear optical materials or combination of linear and nonlinear optical materials to enable versatile functionalities, such as laser generation, laser-wavelength conversion, and laser signal processing. Owing to the build-up of the laser modes inside the dielectric waveguide, coherent or laser-like Smith-Purcell radiation is also generated above the grating via coupling and bunching of the electrons with the surface mode fields.

A single-laser light source system for cold atom interferometers, comprising: a reference light module including a narrow-bandwidth laser and a frequency stabilization module and an optical frequency shift module including a first electro-optic modulator and a first narrow-bandwidth optical-fiber filter. The first electro-optic modulator is connected to the first narrow-bandwidth optical-fiber filter by an optical fiber, and the first electro-optic modulator is connected to the laser by an optical fiber. The first electro-optic modulator receives an initial light from the laser, modulates the initial light by a modulation signal with a preset frequency, and generates sidebands with the preset frequency. The first narrow-bandwidth optical-fiber filter filters the optical signal at the output of the first electro-optic modulator to obtain a frequency-shifted light as the +1-order sideband. The frequency-shifted light is used for modulation to obtain a measurement and control light of the cold atom interferometer.

The active optical fiber comprises an active core doped with at least one the active element and at least two reflective claddings; the cross-sectional area of the core and the cross-sectional area of the reflective cladding adjacent to the core continuously change along the length of the active optical fiber so that the maximum total area S.sup.max of the cross-sectional area of the core and the reflective cladding is at least twice as large as the minimum total area S.sup.min of the cross-sectional area of the core and the reflective cladding; at least one reflective cladding of said at least two reflective claddings comprises at least one modified section configured to reduce the power of the pump radiation propagating along the fiber in at least one reflective cladding after passing the at least one modified section; the at least one modified section of the reflective cladding is located in that region along the axis of the optical fiber, where the total area Sint of the cross-section of the core and the reflective cladding adjacent to the core satisfies the following condition: 1.5×S.sup.min<S.sup.int≤S.sup.max. The method for manufacturing the active optical fiber and the optical signal amplifier based on the active optical fiber are also proposed.

The active optical fiber comprises an active core doped with at least one the active element and at least two reflective claddings; the cross-sectional area of the core and the cross-sectional area of the reflective cladding adjacent to the core continuously change along the length of the active optical fiber so that the maximum total area S.sup.max of the cross-sectional area of the core and the reflective cladding is at least twice as large as the minimum total area S.sup.min of the cross-sectional area of the core and the reflective cladding; at least one reflective cladding of said at least two reflective claddings comprises at least one modified section configured to reduce the power of the pump radiation propagating along the fiber in at least one reflective cladding after passing the at least one modified section; the at least one modified section of the reflective cladding is located in that region along the axis of the optical fiber, where the total area Sint of the cross-section of the core and the reflective cladding adjacent to the core satisfies the following condition: 1.5×S.sup.min<S.sup.int≤S.sup.max. The method for manufacturing the active optical fiber and the optical signal amplifier based on the active optical fiber are also proposed.

There are provided methods and system for providing high power, high brightness, visible laser source and laser beams. There are provided methods and systems of a direct conversion of poor beam quality visible laser light sources into a single high brightness beam in a resonant or ring laser cavity using a dual core or single core optical fiber and Stimulated Brillouin Scattering as the non-linear conversion mechanism in the graded index core of the fiber.