Abstract: Power output and power conversion efficiency of an intracavity non-linear optical laser is substantially increased by reducing the effect of thermal focussing per unit of pump energy enabling a stable resonator cavity at high input powers by utilizing a closely coupled reflector, multi-gain media configuration, and various pump source filters and/or semiconductor laser diode pumping.

Abstract: Sludge digestion in a digester tank wherein the primary sludge is force fed into a vertically extending updraft tube mounted within the tank. The primary sludge is fed into the updraft tube at a position adjacent to the upper open end thereof whereas the gas lift employed for circulating the contents within the tank is introduced at a position adjacent to the lower end thereof with a portion of the conduit for the feed of the gas lift medium extending vertically within the updraft tube. A plurality of openings are provided in the updraft tube to allow for the flow of some of the digested sludge thereinto when the gases are fed under pressure into the updraft tube.