Abstract

Multistage dye amplifier systems have been developed over the past few years for amplification of ultrashort optical pulses to millijoule energies.¹ These systems have utilized a variety of pumping geometries in attempts to maximize short-pulse gain while suppressing amplified spontaneous emission (ASE) and preserving optimum transverse beam quality. The final amplification stage has posed the greatest challenges because of the required high-energy transfer to the short pulse together with the large beam diameter necessary to avoid nonlinear optical effects, making the preservation of favorable transverse beam quality especially difficult. Early systems maximized gain near the output of the final stage cell by using collinear counterpropagating pump and signal pulses at the expense of poor transverse beam quality and focusability. Later systems have improved beam quality to some extent by using transversely pumped prismatic Bethune cells,² sacrificing the desirable feature of maximizing gain near the output of the cell.

© 1988 Optical Society of America