Designs of fiber lasers with a laser resonator with an intracavity Raman-suppressing slanted fiber Bragg sating to provide bidirectional suppression of Raman light.

It is necessary to reduce the power consumption of a plurality of optical amplifiers when there is a difference in the required pumping power between the plurality of optical amplifiers; therefore, an optical amplifying apparatus according to an exemplary aspect of the invention includes a plurality of optical amplifying means for amplifying a plurality of optical signals, each of the plurality of optical amplifying means including a gain medium; a plurality of laser light generating means for generating a plurality of laser beams; at least one optical coupling means for coupling the plurality of laser beams variably in accordance with a coupling factor and outputting a plurality of excitation light beams, each of the plurality of excitation light beams exciting the gain medium; and controlling means for controlling the coupling factor and an output power of each of the plurality of laser light generating means.

An object is to improve the efficiency of amplification by rare earth ion while maintaining beam quality of output light in a multi-mode fiber doped with rare earth ion. A multi-mode fiber (11) that includes a rare-earth-ion-doped core and that has a normalized frequency of not less than 2.40 includes a filter portion (111) that is formed by bending a partial section of or entirety of the multi-mode fiber (11), the filter portion (111) having a smallest diameter (diameter R1) that is set so that (1) only LP01, LP11, LP21, and LP02 modes propagate or only LP01 and LP11 modes propagate and (2) a loss of a highest-order one of the modes that propagate is not more than 0.1 dB/m.

Stimulated Brillouin scattering (SBS) limits the maximum power in fiber lasers with narrow linewidths. SBS occurs when the power exceeds a threshold proportional to the beam area divided by the effective fiber length. The fiber lasers disclosed here operate with higher SBS power thresholds (and hence higher maximum powers at kilohertz-class linewidths) than other fiber lasers thanks to several techniques. These techniques include using high-absorption gain fibers, operating the laser with low pump absorption (e.g., ≤80%), reducing the length of un-pumped gain fiber at the fiber output, foregoing a delivery fiber at the output, foregoing a cladding light stripper at the output, using free-space dichroic mirrors to separate signal light from unabsorbed pump light, and using cascaded gain fibers with non-overlapping Stokes shifts. The upstream gain fiber has high absorption and a larger diameter for high gain, and subsequent gain fiber has a smaller diameter to improve beam quality.

A Raman fiber laser source is configured with a feeding fiber delivering MM pump radiation to an inner cladding of double-clad MM Raman fiber laser. The MM pump beam radiation has a sufficient power to produce Raman scattering in the MM Raman fiber converting the pump radiation to a MM signal radiation at a Raman-shifted wavelength λram which is longer than a wavelength λpump of the pump radiation. The Raman laser source further has a pair of spaced reflectors defining therebetween a resonator for the signal radiation at a 1.sup.st Stokes wavelength and flanking at least part of the MM core of the Raman fiber which is provided with a central core region which is doped with impurities for enhancing Raman process. The reflectors and central core region are dimensioned to correspond to the fundamental mode of the MM signal radiation which is output from the Raman fiber with an M.sup.2 factor ≤1.1 and in a power range between a few kW and tens of kW.

A modular and scalable high-power fiber laser system is configurable to generate 1 kW or more of laser output, and includes one or more separable pump modules separately disposed from each other, each pump module including a plurality of fiber-coupled component pump sources optically combined by one or more fiber-based pump module pump combiners, each pump module providing one or more pump module fiber outputs, and a gain module separately disposed from the one or more separable pump modules and including one or more gain module pump fiber inputs optically coupled to corresponding ones of the pump module fiber outputs, and including a gain fiber optically coupled to the one or more gain module pump fiber inputs, the gain fiber configured to generate a gain module fiber output power scalable in relation to the number and power of said pump module fiber outputs coupled to the gain fiber.

A laser device that is easily assembled and can be manufactured at low cost and a light-source device using the same are provided. The laser device includes a base plate portion, a semiconductor laser element placed on the base plate portion, a lid portion provided on the base plate portion, on which the semiconductor laser element is placed, and including a top plate, and a side wall portion covering a part or all of lateral sides of a space between the base plate portion and the top plate. The top plate is integrally formed with a part or all of the side wall portion.

A combiner, that optically combines input fibers that propagate pumping light launched from pumping light sources and a relay fiber connected to an amplification fiber, includes: a bundle portion where the input fibers are bundled together; and a melting portion where the input fibers are melted and integrated together. In an interface between the relay fiber and the melting portion, the input fibers are fused together without a gap between the input fibers.

A fiber laser is configured with a double clad fiber with a core doped with ions of Erbium (Er.sup.+3) and Ytterbium (Yb.sup.+3). At least two spaced apart high and low reflection mirrors flank the core and define a resonant cavity therebetween. The fiber laser further includes a pump laser outputting light in a 1.02-1.06 μm wavelength range which is coupled into the Yb:Er doped double clad fiber.

A fiber amplifier includes a double clad fiber with a core doped with ions of Erbium (Er.sup.+3) and Ytterbium (Yb.sup.+3), and a pump laser generating radiation at a pump wavelength in a 1.02-1.06 wavelength range, a pump laser outputting light in a 1.02-1.06 μm wavelength range coupled into the Yb:Er doped double clad fiber.

The disclosed fiber laser and fiber amplifier each have a significantly higher lasing threshold in the 1 μm wavelength range than the threshold of the known schematics operating at a 9xx nm pump wavelength.

An optical amplifier includes a light source that generates excitation light in a wavelength band for Raman-amplifying signal light, an input unit that inputs the signal light and the excitation light to an optical fiber, and a processor connected to the light source. The processor executes a process including: acquiring a gain reduction amount of Raman amplification according to power of the signal light input to the optical fiber; determining a target gain based on the gain reduction amount acquired; judging whether a Raman gain corresponding to power of spontaneous emission light generated when the signal light is Raman-amplified in the optical fiber achieves the target gain determined; and setting power of the excitation light according to a judging result at the judging.