The Temperature Dependence of Homogeneous and Inhomogeneous Vibrational Linewidth Broadening Studies Using Coherent Picosecond Stokes Scattering
The theoretical interpretation of vibrational dephasing experiments has been dependent on several simplifying assumptions . One important assumption has been low depletion (≤5%) of the laser pump in the stimulated Raman excitation process. We have observed that, given exponential stimulated Stokes gain and pulse intensity fluctuations from passively mode-locked Nd:glass laser systems, maintaining stimulated Stokes conversions between 1–5% is a nearly impossible task. Figure 1 shows that immediately after the stimulated Raman scattering threshold is reached, the laser can be depleted ≥10% and depletion approaches ≈50% as the laser energy increases. Other studies measuring both laser and Stokes pulses after the Raman cell reveal coincident sharp thresholds for stimulated Stokes scattering and laser depletion . Consequently, we believe that most vibrational dephasing experiments [3–6] have been performed in the high Stokes conversion regime.
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