Investigation of spectrum of rotational resolve spctrum of collimated CO2 Raman laser

In this work, a pulsed 1064 nm laser was used as pump source, high pressure CO2 gas was used as Raman medium, and a spectrum up to 12 anti-Stokes and 2 Stokes collimated vibrational Raman lasers was obtained. When higher pumping energy and high resolution spectrometer were applied, a rotational resolved spectrum of collimated CO2 Raman laser was achieved. By the Boltzmann population distribution and Raman gain coefficient analysis, mechanism of stimulated pure rotational Raman scattering was eliminated, and stimulated S-branch vibrational Raman scattering process was identified; by multiple four-wave-maxing (FWM) processes, a spectrum with multiple rotational Raman structure was achieved. Raman gain of Stimulated S-branch vibrational Raman scattering covered a range of more than ten wavenumbers, and was estimated about 5.5 times smaller than that of Stimulated Q-branch vibrational Raman scattering.