Quantitative analysis of "Δ: l = l _s - L _g" to coherent random lasing in solution systems with a series of solvents ordered by refractive index

This work systematically illustrated the effects of solvents on random lasing in active scatterer solution systems. The scatterer, N,N′-di[3-(isobutyl polyhedral oligomeric silsesquioxanes)propyl]perylene diimide (DPP), was chemically synthesized from gain group perylene diimide (PDI) and scattering group polyhedral oligomeric silsesquioxanes (POSS) at a mole ratio of 1:2 through chemical bonding. Random lasing action was detected in such solutions with a series of solvents ordered by refractive index (RI), from which it was found that solution systems with larger RI solvent facilitate boosting of random laser (RL) for a suitable "Δl = l_s - l_g" (l_s > l_g). There are two potential situations for solvents with smaller RI: in one, a small RI difference between scatterers and surroundings results in extremely large l_s, and the extremely large Δl in these samples means that there is no observation of random lasing; in the other, there is increased l_g as characterized by UV-Vis spectroscopy, although the l_s remains almost unchanged for the large RI fluctuations between scatterers and surroundings, resulting in smaller Δl with no detection of random lasing as the laser pumping energy cannot compensate for the gain loss. Results from this work will aid in quantitatively judging the necessary condition of "Δl = l_s - l_g" to RL in solutions, and aid in designing suitable solution systems to boost RL.