Tunable random laser in capillary with Nile red solution and TiO2 nanoparticles

Abstract

We report a tunable random laser in Nile red (NR) solution with TiO2 nanoparticles (NPs). The good lasing characteristics and low-level threshold at 71.8 μJ is achieved in our random laser system. We analyze the influence of TiO2 NPs number density to the random laser threshold and obtain the optimal number density of TiO2 NPs in NR/ethanol solution as 2.018 × 1013 cm−3 with lowest threshold. Furthermore, on account of the solvatochromism characteristic of NR, we use sulfuric acid to change the polarity of the sample and obtain the continuously tunable random laser spectra, ranging from 642.7 nm to 668.8 nm. This random laser system containing NR and TiO2 NPs has advantages of easy operation, simple structure, and large tuning range, which could open up an avenue to the generation and tuning of random laser, and meanwhile provide innovative ideas such as speckle-free laser source used in laser display technology or other fields.