Since the early 1990s, fiber lasers have established themselves in the telecom and medical procedure markets, as well as in a variety of advanced and scientific applications. The wide wavelength range, narrow linewidths, polarized or unpolarized emissions, short pulse durations, single-mode operation, insensitivity to environmental conditions, and compact size of fiber lasers make them a favorable solution for the scientific and government communities, where the lasers often help to solve challenges that other laser technologies cannot.

During the 2000s, industrial fiber lasers were increasingly used for processing materials in applications across automotive, aerospace, heavy industry and transport, consumer devices, electronics, medical devices, oil and gas, nuclear power, photovoltaics, semiconductor manufacturing, and other industries.

While materials processing of metals has accounted for the bulk of early adoption, other quickly emerging applications include cladding and 3D printing, heat treating, surface cleaning and modification, and a variety of microprocessing techniques encompassing polymer, ceramic, and other nonmetal materials.

Across all of these industries and applications, industrial fiber lasers have emerged as a benchmark for performance. Their comparably higher output powers and uniformly excellent beam quality help to ensure fast processing speeds, while their resistance to vibration and contamination, rugged compact packaging, efficient energy consumption, and reliability contribute to a fast return on investment.

Industrial fiber lasers have two stages, characterized by power combiners and brightness converters (Figure 1).

An industrial fiber laser, such as this single-mode fiber laser configuration using a single-emitter diode, has two stages, a power combiner (stage 1) and a brightness converter (stage 2).

The first-stage power combiner consists of a collection of multiple laser diode-pumped packages designed to efficiently combine their multimode light into a passive delivery fiber. The use of a redundant number of single emitter diode packages ensures high reliability of the laser. The laser's optical cavity is defined by two fiber Bragg grating mirrors in the central single-mode core, a clad high-purity fiber doped with various rare earth elements.

The cavity converts the low-quality diode light into single-mode laser light. One of the FBGs acts as a total reflector, while the other acts as a partial reflector or output coupler. The multimode cladding is undoped. It is only used to spread the diode pump light. The solid-state construction of fiber lasers makes them less susceptible to environmental factors such as dust, moisture, and free-space air disturbances.

The bulk pumping approach has electrical efficiencies in excess of 50% and produces a single-mode output of approximately 2 to 3 kW of continuous wave power from a single module. The outputs of individual modules can be used directly or combined to provide high-brightness output exceeding 100 kW, which enables fiber lasers to meet a variety of industrial applications (Figure 2).

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