Patent ID: 7593435

Claim:
A single mode (SM) ultra powerful fiber laser system comprising: at least one gain block having a multiclad and multimode active fiber (AF) with a core, which is configured to support a fundamental mode of light propagating therethrough at a first wavelength (Le) and characterized by a core mode field diameter (MFD), an inner cladding and at least one outer cladding; upstream and downstream SM photosensitive fibers coupled to respective opposite ends of the AF and having respective field mode diameters which substantially match the MFD of the core of AF; and at least two spaced apart fiber gratings defining a laser cavity therebetween, at least a portion of the AF being located within the laser cavity; at least one ultra powerful pumping assembly comprising a plurality of SM fiber lasers each having and operative to emit an optical pump output at a second wavelength (Lp) shorter than the Le of the AF; at least one SM-MM fiber combiner combining outputs of the respective SM fiber lasers into a multimode (MM) output pump fiber launching a low mode pump output into the AF; an output delivery fiber emitting an optical system output and having an input region substantially losslessly spliced to the downstream SM photosensitive fiber and an output end region, the delivery fiber being configured as a multiclad passive (PF) with a multimode core propagating the fundamental mode of the laser emission without an essential coupling to higher modes, wherein the multimode core of the PF has a field mode diameter at least along the input end region thereof substantially matching the MFDs of the respective AF and SM fibers at the first wavelength (Le); and an output connector having a silica beam expander spliced to the output end region, of the PF, wherein the at least one gain block, fiber gratings, fiber coupler, pumping assembly, SM-MM combiner, and the PF fiber are configured as a monolithic system without free space interfaces upon being losslessly coupled to one another.