Abstract
The random laser (RL) based on organic Rhodamine 6G (R6G) laser- dye and Titanium dioxide (TiO2) suspended nanoparticles have been prepared with polymethylmethacrylate (PMMA) as a host. Both liquid and spray-coated homogeneous film samples of 22.4 µm - 30.1 µm thickness range were use. Optimum concentrations have been determined depending on the normal fluorescence spectra which give evidence that the laser dye provides amplification and TiO2 nanoparticles as scatter center. At the optimum concentrations, results of the random laser (RL) under second harmonic Nd: YAG laser ex-citation show that the values of bandwidth at full width half-maximum (FWHM) and the threshold energy are about 9 nm and 15 mJ respectively, which represent the minimum value for the liquid samples in the current research. Correspondly, these values become 14 nm and 15 mJ for film sample. The broadening that can be attributed to the concentration quenching of a laser dye at high concentration levels has been observed.
Highlights
Random lasers (RL) are unique sources of stimulated emission in which the feedback is provided by scattering in a gain medium [1,2]
Results of the random laser (RL) under second harmonic Nd: YAG laser excitation show that the values of bandwidth at full width half-maximum (FWHM) and the threshold energy are about 9 nm and 15 mJ respectively, which represent the minimum value for the liquid samples in the current research
Rhodamine 6G laser dye (C28H31N2O3Cl) with molecular weight 479.02 g/mol supplied by Lambda Physics LC (5900): Ethanol alcohol (C2H5OH) with spectroscopic grade purity supplied by Gainland Chemical Company and chloroform (CH3CCl3) with spectroscopic grade purity supplied by Philip Harris chemical company UK
Summary
Random lasers (RL) are unique sources of stimulated emission in which the feedback is provided by scattering in a gain medium [1,2]. In a random laser the FWHM of the spectrum of the emitted light below the threshold of the laser is approximately the width of the emission spectrum of the gain medium (typical 40 nm) for R6G. From fluorescence measurements of the above concentrations, it was noticed that a TiO2 concentration of 10–3 mol/l had the highest intensity and the narrowest bandwidth for both liquid and film samples At this optimum TiO2 nanoparticles concentration, the emission intensity spectra at different Nd:YAG pumping energies were investigated to determine the lasing threshold [17]
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