Optical Fiber, Coil Winding, Lasers and Amplifiers

Conventionally, large-mode-area (LMA) fiber lasers use free-space polarizing components to achieve linear
polarization output. External components, however, significantly limit laser robustness and power scalability.
We demonstrate, to the best of our knowledge, the first high-power all-fiber cavity single-polarization
single-transverse-mode LMA fiber laser, without the use of free-space polarizing components. This has been
achieved by using tightly coiled high-birefringence 20 μm core LMA fiber. The lasing spectrum at 1085 nm
has been stabilized by a fiber grating, spliced at one end of a LMA fiber. Up to 405 W of single-polarization
output with a polarization extinction of >19 dB with a narrow spectrum (1.9 nm FWHM) and in a singletransverse
mode (M² < 1.1) has been demonstrated. The simplicity of a monolithic-cavity approach is highly
beneficial for a number of applications, including the use of a fiber laser for nonlinear wavelength conversion
and for coherent and spectral beam combining.

Solid state and gas lasers are routinely capable of producing cw multi-kW output powers and as such have become the mainstay of the laser cutting and welding industry.

Ytterbium-doped large mode areas (LMA) fibers have become an established high power laser medium in recent years

Recent advances in diode technology and the development of ytterbium-doped Large Mode Area (LMA) fibres have facilitated the demonstration of kilowatt-level fibre lasers.

A highly temperature-insensitive fiber is reported. Furthermore, a convenient method for selecting the temperature of minimum sensitivity, by controlling the B₂O₃ concentration in the core and monitoring it with 1550 nm attenuation, is presented.

Lidar applications involving human presence require eye safe laser emission. Good beam quality, for efficient power delivery to the target, and relatively short pulses of 1ns or less, for good spatial resolution, are also common modern Lidar requirements.

Large mode area (LMA) fibers enabled a rapid increase of continuous-wave (CW) single-transverse-mode fiber laser powers which currently are above 1-kW.

CO₂ and YAG lasers are routinely capable of producing cw output powers in the range of sub-W to multi-kW and as such have become the mainstay of the laser cutting and welding industry.

We report our recent progress in designing and manufacturing new, completely monolithic, linearly polarized, continuous wave (CW) fiber lasers that provide more than 300W of output power in a near diffraction limited, single transverse mode, spectrally stabilized output beam having a narrow line-width. The demonstrated design is simple and practical: the monolithic laser cavity can consist of only of a coil of polarization maintaining (PM), large mode area (LMA) active fiber having a fiber Bragg grating (FBG) at one end and a fiber cleave at the other end. Proper selection of the coil diameter enables gain in only one polarization mode so as to provide the linearly polarized output. Fiber lasers built using this novel technique do not require any external polarizing components or the use of polarizing fiber. Such compact and robust fiber lasers are suitable for a variety of applications, such as multi-kW power scaling through coherent beam combining, nonlinear wavelength conversion processes using a variety of nonlinear materials, etc.

We demonstrate the first completely monolithic linearly-polarized (extinction 19dB) fiber laser producing high power (306W) diffraction-limited beam (M² ~1.1) with a stabilized, narrow-linewidth (0.57nm) spectrum at 1086nm. Laser design does not require any external polarizing components.

Fiber lasers have a number of distinct advantages over their more conventional solid state laser alternatives. These advantages include size, reliability, wavelength selectivity, heat dissipation, wall plug efficiency and operational cost.

We demonstrate 700-W fundamental mode beam from Yb-doped fiber laser operating at 1092 nm.

It is shown that continuous-wave kW-power fibre lasers can be built using double-clad fibres with relatively small cores.

Although fiber amplifiers have been employed in communications systems for many years, until very recently the fiber laser was little more than a scientific curiosity.

The advent of double clad fiber technology has made high power lasers and amplifiers
possible.

Single mode, single-polarization output is demonstrated in a large mode area (LMA) fiber laser. Both mode filtering and polarization filtering are demonstrated by simply coiling multimode Polarization Maintaining Fibers (PMFs). The design is scaleable for all-fiber high power lasers.

We report on a linearly polarized (extinction ratio ~17 dB) large-mode-area fiber laser with an output power above 300 W and diffraction-limited beam quality. The PANDA-design is applied to induce the birefringence in the fiber.

Recent progress in fiber lasers has resulted in continuous wave (CW) powers as high as 810 W in a singlemode beam from a single-fiber system.

For intrinsic fiber optic sensors such as interferometric fiber optic gyroscopes that use polarization maintaining fibers, performance of the fibers that constitute the sensing coils is a key issue.

With the output power of fiber lasers growing all the time, manufacturers are hoping they'll be powerful enough to edge out the lasers already ensconced in industrial settings.

High-power fiber-laser arrays can potentially produce tens or hundreds of kilowatts of output power, providing significant military capabilities. At the May Solid-State and Diode Laser Technology Review workshop, hosted by the Directed Energy Professional Society (DEPS) in Albuquerque, NM, researchers from Northrop Grumman Space Technology demonstrated significant progress toward a seven-element fiber-laser array based on ytterbium (Yb)-doped polarization-maintaining single-mode power amplifiers. The 155-W output from the single fiber laser was a record for this type of coherent-beam-combining design and should prove highly scalable.

Reduced cladding fibers (80 mm vs. 125 mm) are attractive for small form factor components. Experimental and modeling data are presented to show that the fiber and/or the coil need to be redesigned for the impact of reducing cladding diameter on bend loss.

The adoption of reduced cladding thickness fibers by the telecom industry has greatly increased over the last year. In fact, almost every specialty fiber manufacturer has launched products aimed at the small form factor (SFF) market. Despite appearances the use of 80µm OD fiber, rather than 125 µm, has actually been commonplace for years in certain non-telecom applications, fiber optic gyros for example. The general move toward SFF components within the optoelectronics industry -- specifically telecom and datacom applications -- is also well underway.

Fibers for high-power laser and amplifier applications require large claddings with high numerical apertures for efficiently coupling pump energy.