New concepts in the field of pump light injection are required to create compact and stable fiber laser set-ups for high-performance operation.
The Fraunhofer IOF is pursuing the concept of a reflecting pump coupler. For this, several pump fibers are arranged concentrically around the active fiber. The pump light supplied by these fibers is projected into the pump core of the active fiber via the curved inner surface of a spliced plan convex lens. The area of the end cap is dichroically coated so that pump light is reflected and laser light coming from the active fiber core is transmitted. As a result, with corresponding design of the end cap, it is possible to reduce power densities during beam exit and, in addition to the monolithic pump light injection, ensure a high level of power stability.
The coupling represents a monolithic injection concept for pump light, in which the amplified light is coupled out as an impulse using an end cap and can therefore be used further, for example, in a grating compressor as part of a short pulse fiber amplifier.
Jun Ki Kim, Christian Hagemann, Thomas Schreiber, Thomas Peschel, Steffen Böhme, Ramona Eberhardt, and Andreas Tünnermann, "Monolithic all-glass pump combiner scheme for high-power fiber laser systems," Opt. Express 18, 13194-13203 (2010)