Abstract

Recently, Lee and Hahn¹ demonstrated high energy efficiency of a four-pass amplifier by passing the laser beam back and forth four times on a single axis through a gain medium. This four-pass amplifier was capable to suppress self-oscillation to be generated by the laser beam traveling through the same pass in a high gain medium. However, the output beam of the four-pass amplifier involves quite big amplified spontaneous emission(ASE). They reported that the ASE portion reached to 15 % in normal operation. In the present work we introduce a new design of a four-pass amplifier suppressing the generation of ASE during the amplifying process, and describe the detailed operational characteristics of the new four-pass amplifier.

© 1998 IEEE