Fiber lasers - Sources, technology and applications

Although first implemented in the 1960s, fiber lasers have only been in common use in industry for the past 20 years or so. Their success can be explained by their unique properties: they combine high optical efficiency, good heat dissipation, high integration potential, and excellent beam quality. These properties, combined with the possibility of pumping with high-power laser diodes, make fiber lasers particularly bright sources. In addition, numerous technological developments related to the telecommunications industry have led to highly reliable manufacturing processes and the availability of a wide variety of guided optics components. This article provides a general overview of fiber lasers, their properties, and their applications.

The first part starts with the guiding properties of active optical fibers to determine the optogeometric parameters relevant to the implementation of fiber laser sources. The different optical pumping schemes are discussed. Beam quality is defined and the main architectures used around active optical fibers are described. Finally, a commonly used model based on population equations is presented, allowing the performance of fiber laser sources to be determined quantitatively.

In the second part, we study optical amplification mechanisms in optical fibers, the various technologies associated with them, and the areas of the optical spectrum that can be achieved using them. Three rare earth elements whose radiative transitions are commonly used for optical amplification—erbium, ytterbium, and thulium—are given special attention. More versatile solutions in terms of spectral range, such as stimulated Raman scattering, optical parametric amplification, and supercontinuum generation, are briefly presented.

Fiber lasers can be configured to emit in very different temporal regimes; the emitted radiation can be continuous, and even longitudinally single-mode, but can also be composed of pulses of varying durations, down to the femtosecond regime. In the third part, we present the laser architectures that enable these regimes to be achieved, and the parameters that influence the properties of the emitted pulses.

Finally, we describe the main applications of laser sources in various fields of industry, medicine, biology, and physics. We will see that the main applications of high-power fiber lasers in industry are cutting, welding, and laser marking. The various temporal regimes accessible by fiber sources allow for very different cutting or marking qualities to be obtained. Other more specific applications are also examined, such as sensors, lidars, femtosecond comb frequency metrology, and applications in biological tissue imaging.

A glossary of terms used can be...