Behaviors of the Rh6G random laser comprising solvents and scatterers with different refractive indices

We report a systematic study based on the random laser behaviors of comparable systems in which the refractive indices are varied. Threshold and spectra features have been obtained. The experimental results indicate that the threshold (Eth) of the random laser depends on the refractive index of the scatterers and surrounding solvents. The larger the refractive index of scatters or smaller the refractive index of solvents is, the smaller the Eth will be. The theoretical explanation based on Mie scattering theory for this phenomenon is made. We introduce refractive index contrast-ratio w. The thresholds variation is attributed to the alteration of w which influences the scattering strength and the transport mean free path. As for the spectra, typical emission evolution spectra have been observed. The peak positions vary with the change of scatterers and solvents, the reason of the variation is the absorption of the samples.