Fig. 1.

(A) Low-frequency Raman spectra measured on the setup described in Urquidi et al. (2). The detection part was modified using SureBlock XLF Notch filters (Coherent) to be able to measure the low-frequency region of Raman spectrum. The sample is SnCl₂ dissolved in water (1 mol⋅L⁻¹). This sample is suited for this purpose because it has well-defined peaks at the region where we can measure both Stokes and anti-Stokes Raman spectrum. No change of the spectra was observed from 150 mW up to 1.2 W. If the temperature were elevated by the 532-nm laser, the relative peak intensity of Stokes Raman ($I_S$) to anti-Stokes Raman ($I_{\mathit{AS}}$) would have decreased. (B) The expected ratio of $I_S$ to $I_{\mathit{AS}}$ at 111 cm⁻¹ peak as a function of temperature calculated using the model in ref. 5. As expected, the $I_S/I_{\mathit{AS}}$ decreases as temperature increases. (C) The $I_S/I_{\mathit{AS}}$ calculated from the data shown in A. The ratio remains constant around room temperature even at 1.2-W laser power.