AI Article Synopsis
- Researchers used 18 femtosecond laser pulses at 820 nm to perform Z-scan measurements on carbon disulfide (CS2), focusing on the effects of pulse timing and separation.
- They found that the negative nonlinear refraction in CS2 increased with time relative to the pulse train, especially within the thermal diffusivity time constant.
- The study challenges the traditional view of how heat is generated in CS2, suggesting that non-radiative relaxation from individual laser pulses, rather than multi-photon excitation, is responsible for the observed thermal lensing effect.
Article Abstract
By chopping 820 nm 18 femtosecond (fs)-laser pulses, continuously generated by a self-mode locked Ti:Al2O3 laser at 82 MHz, into trains with both train-width and train-to-train separation considerably longer than the thermal diffusivity time constant τth of CS2, we conducted Z-scan measurements on it at various times relative to the leading pulse of each train (T's). As a result, we observed negative nonlinear refraction strengthening with T within τth and gradually stabilizing with T exceeding τth. We quantitatively explain the experimental results in terms of the thermal lensing effect. In particular, we attribute the heat generation to non-radiative relaxation of libration excited by individual 18 fs-pulses via stimulated Raman scattering. In contrast to the commonly held view of multi-photon excitation, we propose and verify a new heat-generating mechanism for the thermal lensing effect in CS2.
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| http://dx.doi.org/10.1039/c5cp01796c | DOI Listing |
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