The high-power-optical-amplifier of the present invention uses a number of spaced, thin slabs (e.g., disc-shaped doped-slabs that are stacked, with a space between discs), aligned to give an amplifier both with a high active cross-section and a very high surface area to volume ratio. More specifically, the present invention provides several methods that include the steps of aligning at least two or four slabs having a thickness dimension of less than one centimeter, substantially parallel to, and spaced from adjacent slabs, wherein the slab surfaces are rendered essentially non-reflective, optically pumping the slabs and passing an input beam through the surfaces wherein the beam is optically amplified in the slabs, and wherein the input beam is of an eye-safe wavelength.