Nitrogen-laser-pumped ultrashort pulse amplifier

The amplification of ultrashort pulses in a N₂-laser-pumped amplifier was studied both theoretically and experimentally. A good agreement was found between the theoretical and experimental results over six orders of magnitude of input energies if the excited-state absorption of the dye was taken into account. The output energy density of the last amplifier stage was 16.0 mJ/cm², which ensured an energy extraction efficiency as high as 7.7%. The calculated pulse duration increase was 20%. The amplified spontaneous emission background was found to be 1%. The stabilization of the output pulse energy by saturation of the amplification is discussed.