Fiber laser sources and applications

Although first introduced in the 1960s, fiber lasers have only been in widespread use in industry for the past ten years. This success is due to 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 high-power laser diode pumping, make fiber lasers particularly bright sources. In addition, numerous technological developments in the telecommunications industry have led to more reliable manufacturing processes and the availability of a wide variety of guided optics components. This article gives an overview of fiber lasers, their properties and applications.

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

In the second part, we present the mechanisms of optical amplification in optical fibers, the various technologies associated with them, and the areas of the optical spectrum that can be reached by using them. Special attention is paid to three rare earths whose radiative transitions are commonly used for optical amplification: erbium, ytterbium and thulium. More versatile solutions in terms of spectral range, such as stimulated Raman scattering, optical parametric amplification, or supercontinuum generation, are briefly presented.

Fiber lasers can be configured to emit in a wide range of temporal regimes: the radiation emitted can be continuous, and even longitudinal single-mode, but can also be composed of pulses of varying duration, right up to the femtosecond regime. The third section describes 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 and biology, and physics. The main industrial applications of high-power fiber lasers are cutting, welding and laser marking. The various temporal regimes accessible to fiber sources enable us to obtain very different cutting or marking qualities. Other more specific applications will also be examined, such as sensors, lidars, femtosecond comb frequency metrology, or biological tissue imaging applications.