Novel total-internal-reflection pump-signal coupler with >90% pump coupling efficiency from a broad-area diode laser into a double-clad fiber

In this paper, we present a novel total-internal-reflection (TIR) pump-signal coupler for coupling multimode pump light from a broad-area laser into a double-clad fiber (DCF) having small inner-clad diameters with higher pump brightness. We demonstrate a coupling efficiency exceeding 90% with negligible effect on the single-mode signal. The TIR couplers have wide application to compact high performance amplifiers utilizing multimode pump sources.