ABSTRACT
Fiber lasers began their remarkable history in the early 1960s, when the first working laser of its kind was demonstrated, and very soon after, optical fibers with reasonably small attenuation were developed [1,2]. Initially, optical fibers mainly found application in signal transmission in optical telecom networks. It took about two decades before fully functional fiber-based optical amplifiers and fiber lasers appeared on the scene of research and industrial applications. Optical fibers with different dopants, mainly rare earth metal ions, have opened virtually unlimited opportunities as unique gain materials operating in the near-and mid-infrared (IR) bands of the optical spectrum. Currently, fibers of complicated chemical structure with gain properties in the far IR, over 3 μm, are being actively explored [3-6].
