EFFECT OF LASER LINEWIDTHS ON EFFICIENCY IN GENERATION OF EQUALLY-SPACED MULTIFREQUENCY BEAM BY 4-WAVE ROTATIONAL RAMAN MIXING

A two-color dye laser system whose linewidths can be changed independently is constructed for an investigation of the efficiency in generation of equally-spaced multifrequency laser emission by the two-color stimulated Raman effect. The efficiency in generation of a vibrational line is reduced substantially by increasing the linewidth of the laser, while it is not reduced drastically for rotational lines. Consequently, the rotational lines are more pronounced by broadening the laser linewidth. These results are explained by a difference in the processes for generation of these emissions, i.e. conventional Raman scattering for vibrational emission and four-wave Raman mixing for rotational emission. The present investigation implies that equally-spaced multifrequency laser emission can be generated efficiently in a wide spectral domain using a transform-limited femtosecond (high peak power and broad linewidth) laser pulse, which is required for generation of an ultrashort optical pulse in the scheme proposed in Optics Comm. 96 (1993) 94.