Efficient quantron with a coaxial pump lamp and a phosphate-glass active element

Record characteristics for a quantron with a coaxial pump lamp have been achieved: a small-signal gain of 6000 per pass through the active element and an efficiency of 6% under free-running conditions. A tight fit of the active element in the coaxial lamp maximizes the laser efficiency but prevents the attainment of large values of the small-signal specific gain coefficient. The decrease in the efficiency of the amplifiers with increasing pump energy which is observed experimentally is due primarily to an increase in the superluminescence loss. Methods for reducing this loss are discussed.