Abstract

A novel design of the refractive index profile for cladding-pumped fiber lasers and amplifiers has been developed and experimentally realized (cf. Fig. 1). The core (1) consists of pure silica and is doped with rare earth ions only. The light guiding in the core is provided by a depressed-index cladding (2) which is thick enough to suppress energy transfer from the core to the second cladding (3). The second cladding has almost the same index as the core as it consists of pure silica. A jacket with a low refractive index serves as third cladding (4). This leads to an interface with a high numerical aperture to guide the pump light. The single mode core has a low numerical aperture to allow for an increased diameter. This is advantageous for the absorption of pump light from the cladding, an increased energy storage capacity in the upper laser level for Q-switched systems and a reduced intensity in the core for high power applications. Since the core can be manufactured without index-raising dopants, the design also offers low intrinsic losses.

© 1998 IEEE