Nonresonant Effects in CO2 Amplifier of Ultrashort Laser Pulses

Recently the amplification of subpicosecond pulses in CO2 resonant with 10.6 μm lasing transition 001→100 has been achieved for intensities up to 1012 W/cm2 [1]. This corresponds to Rabi frequency ≃ 10 cm-1 which becomes comparable to the detuning of various CO2 transitions usually neglected in standard calculations [2]. For instance, this Rabi frequency becomes close to the spacing between laser P(20) transition and R(18) transition equal to 32 cm-1 [1,3]. For higher intensities, the 9.6 μm, 001→020 transition should be taken into account, as well as the transitions 001→000, 001-002, etc. - see fig. 1.