<p>Among photothermal techniques, the pulsed-laser thermal lens (PLTL) method provides highly accurate measurements of thermo-optic parameters. In this study, the PLTL setup was first validated by measuring the thermal diffusivity of the pure solvent over a range of temperatures, yielding a maximum deviation of only 1&#xa0;% from reliable reference data and confirming the high accuracy of the system. Subsequently, ethanol solutions of Rhodamine 123 (Rho123) and Rhodamine 110 (Rho110) with concentrations ranging from 0.02&#xa0;g⋅L⁻¹ to 0.09&#xa0;g⋅L⁻¹ were prepared, and their characteristic times and corresponding thermal diffusivities were measured at temperatures between 288&#xa0;K and 328 K. The results demonstrate that the thermal diffusivity of both dyes increases monotonically with temperature, while remaining nearly independent of Nd:YAG laser energy within the investigated range. In contrast, increasing dye concentration leads to a pronounced reduction in thermal diffusivity due to enhanced thermal-wave scattering and energy trapping by dye molecules. A comparative analysis reveals that dilute Rho123 solutions exhibit higher thermal diffusivity than Rho110 under identical conditions. This behavior is attributed to weaker thermal trapping and lower scattering losses in Rho123 solutions, which facilitate more efficient heat transport. Consequently, Rho123 is identified as a more favorable active medium for dye laser applications, where effective thermal management and cooling performance are critical.</p>