Ultimate values of the gain of solid-state rod amplifiers operating under inversion storage conditions

A numerical calculation is reported of an inversion conservation coefficient of cylindrical rod solid-state amplifiers with the active element diameter from 1.5 to 15 cm operated under continuous pumping conditions. It is shown that the ultimate gain, limited only by superluminescence, exceeds considerably the value usually obtained in experiments. Various methods of eliminating parasitic effects, which limit the gain of real amplifiers, are considered. The degree of influence of these effects on the inversion conservation coefficient is discussed. The results are given of an experimental determination of the gain close to the ultimate value (0.18 cm^– 1 for an active element 3 cm in diameter). Calculations are reported of the angular distributions of superluminescence and parasitic modes demonstrating that the latter can be suppressed by spatial filtering.