An apparatus and method for pumping optical fibers. An optical element is disposed for directing pump energy into the inner cladding of a dual clad optical fiber, where the optical element has a refractive index greater than the refractive index of the inner cladding. A gradient refractive index structure is disposed between the optical element and the inner cladding to provide for a smooth transition from the refractive index of the optical element to the refractive index of the inner cladding.