Thermal Relaxation Time and Thermal Diffusivity in Random Laser Gain Media: Balancing Plasmonic Heating and Enhanced Cooling to Continuous-Wave Operation

Abstract

The active medium in the random laser consisted of an active material, the kiton red dye, and scattering centers. In the current study, two types of scattering centers were used: perovskite nanoparticles and Au nanoparticles. The thermal relaxation time and thermal diffusivity of this medium are significant factors that affect the stability of the structure and output coefficients. Thermal lens spectroscopy, which relies on the use of two types of lasers, was used to measure these two factors. The pumping laser had a wavelength of 532 nm and a power of 20 mW, whereas the probe laser was of the helium-neon type with a wavelength of 632 nm and a stable power of 1 mW. The results showed a clear effect of the dye solution concentration, as increasing the dye concentration increased the thermal relaxation time and decreased the thermal diffusivity. A significant effect was also observed when nanoparticles were added. The also of perovskite nanoparticles led to nonlinear behavior, which created an ideal volumetric ratio for heat leakage. The results also showed that the addition of Au nanoparticles led to an increase in the thermal relaxation time and a deterioration in the thermal diffusivity. The reason for the increased thermal relaxation time in the case of nano-gold is its strong absorption of light and its conversion into heat via the photothermal effect, which increases the overall heat capacity of the system, while perovskite allows the possibility of controlling heat leakage through the optimal volume ratio. These findings can be used to design thermally stable random laser devices for biomedical imaging and remote sensing applications. A future horizon for this work is to develop a theoretical model that links the geometric structure of the scattering centers and the parameters that were measured.