A fiber laser apparatus includes a fiber laser oscillator that performs laser oscillation with laser light from at least one laser diode module, and includes a loop-shaped optical fiber formed with: a combiner in which at least two input side optical fibers are connected to one output side optical fiber that includes one output end; and an optical fiber for connection of both ends in which the output end of the output side optical fiber is connected to the input end of any one of the input side optical fibers, the optical fiber for connection of both ends including a light leakage means formed such that at least one of values among a numerical aperture, a core diameter and a mode field diameter of the optical fiber for connection of both ends is gradually reduced from a side which is connected to the output end toward a side which is connected to the input end.

A microstructured optical fiber for generating supercontinuum light. The optical fiber includes a core and a cladding region surrounding the core. The optical fiber includes a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections. The first fiber length section has a core with a first characteristic core diameter larger than about 7 ?m. The second fiber length section has a core with a second characteristic core diameter, smaller than said first characteristic core diameter. The intermediate length section of the optical fiber includes a core which is tapered from said first characteristic core diameter to the second characteristic core diameter over a tapered length. Also, a supercontinuum light source including an optical fiber and a pump light source.

The present invention benefits from the determination that pre-selected spectral bandwidths that avoid the spectrum of an electronic transition of a metal/alloy vapor allow for welds substantially free from detritus that may discolor the weld. Accordingly, the present invention provides analytical methods, welding methods and fiber lasers configured to provide high quality metal/alloy welds.

A single mode fiber pulsed oscillator includes an all normal dispersion ring cavity provided with a mode-locking fiber loop component and a giant chirp generating fiber component. The mode-locking fiber loop component is configured with a hybrid of NOLM and NALM configurations which is operative to induce a first phase acquisition of a spectrally narrow pulse due to SPM. The giant chirp generating fiber loop component is configured to induce the additional phase acquisition to the pulse broadened in the mode-locking fiber component so as to generate a pulse with a giant chirp. The fiber loop components each include a fiber amplifier and a coil of fiber. The amplifiers each are configured with an active fiber provided with a core which supports multiple transverse mode in a range of wavelength except for the desired wavelength at which the core is configured to support a single fundamental mode.

A single-mode (SM) Green fiber laser is configured to operate in a Green spectral range in a continuous-wave (CW) or quasi-continuous-wave (QCW) mode. The Green laser is configured with a pump source, outputting narrow-linewidth pump light at a fundamental wavelength in one (1) micrometer spectral range, and a single-pass second harmonic generator (SHG), such as a nonlinear LBO crystal, frequency doubling the pump light to output Green light at a signal wavelength. The pump light source is configured to have a MOPFA configuration with a SM seed which emits the SM pump light with a linewidth narrower than 0.2 nm, and at least one ytterbium (Yb) fiber amplifier receiving and amplifying the SM pump light at the fundamental wavelength while maintaining the linewidth narrower than 0.2 nm. The SM Green fiber laser operates with a wall plug efficiency between 15% and 30% in a 510-540 nm signal wavelength range and a power range between about 50 W and kW-levels.

A fiber amplifier has a first amplification stage and a second amplification stage. The first amplification stage comprises a first gain fiber that is configured to receive, at its input end, a signal light and a pump light. The first gain fiber uses a portion of the pump light to provide first-stage amplification to the signal light. The second amplification stage comprises a second gain fiber that is configured to receive, at its input end, the first-stage-amplified signal light and residual pump light. The second gain fiber uses the residual pump light to provide second-stage amplification of the first-stage-amplified signal light and to provide, at its output end, the second-stage amplified signal light. The first amplification stage may include a single-mode gain fiber, and the second amplification stage may include a higher-order-mode gain fiber, and the first amplification stage may be configured to provide single-mode amplification of a sub-threshold input to satisfy the low-ASE threshold of the second amplification stage.

A microstructured optical fiber for generating supercontinuum light. The optical fiber includes a core and a cladding region surrounding the core. The optical fiber includes a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections. The first fiber length section has a core with a first characteristic core diameter larger than about 7 ?m. The second fiber length section has a core with a second characteristic core diameter, smaller than said first characteristic core diameter. The intermediate length section of the optical fiber includes a core which is tapered from said first characteristic core diameter to the second characteristic core diameter over a tapered length. Also, a supercontinuum light source including an optical fiber and a pump light source.

Disclosed are a mode-locked resonator according to an embodiment and an ultrashort pulse laser comprising the mode-locked resonator. The mode-locked resonator according to an embodiment includes a resonator including a shape of a sphere; and a saturable absorber coated on a surface of the resonator, wherein the resonator is coupled with some photons traveling in a tapered optical fiber disposed near the mode-locked resonator and interacts with the saturable absorber based on a Whispering Gallery Mode (WGM).

A water-cooled package of an optical fiber combiner (OFC) comprising an OFC assembly, a front end cap (EC), a rear EC, and a housing operates for long term reliability. The OFC assembly comprises two submounts and an OFC. Each of the two submounts comprises a U-groove in a lengthwise direction and two flat portions symmetrically connected to the U-groove in a widthwise direction. The two flat portions of each of the two submounts are mechanically coincident in a way to form a cavity between the two U-grooves of the two submounts, in which the OFC is fixed. When the OFC assembly is concentrically mated and sealed with the front EC and the rear EC, cooling water in the water-cooled package is prevented from immersing the OFC. The configurations can minimize varying stress-induced optical degradations and maintain beam quality of a laser light exiting the OFC.

A single mode (SM) high power laser system is configured with a laser source outputting a single mode or low mode kW-power light and a passive delivery fiber spliced to an output fiber of the fiber laser source and having a double bottleneck-shaped core. The latter is configured to increase a threshold for nonlinear effects in general and in particular for stimulated Raman scattering (SRS) so that the delivery passive fiber has a fiber length at least twice the length of a delivery passive fiber with a standard uniformly dimensioned core, which may be used with the same laser source, while outputting the kW-power light with an M2 factor less than 2.