Abstract
In this paper, a random laser is fabricated based on zinc oxide (ZnO) nanosheets, which are grown on a fluorine-doped tin oxide glass substrate using an electrodeposition technique. ZnO nanosheets act as scattering centers, while optical gain in the random laser is provided by Rhodamine 6G dye solution. It is found that there is only a single emission peak in the random laser spectrum. It is also observed that changing the electrolyte concentration used in electrodeposition leads to the generation of ZnO nanosheets with different sizes, thicknesses, and shapes. The effects of changing the sheet geometry on the random laser characteristics are studied. Our results reveal that by increasing the size of nanosheets and decreasing their thickness, first the lasing threshold decreases and then two peaks appear in the emission spectrum, which are called random laser modes. These effects arise from the dependence of optical absorption and scattering strength of ZnO nanosheets on their sizes and thicknesses. Because of mode competition and cross gain saturation effects between the excited modes, an increase in their threshold and a decrease in their intensity are observed. Furthermore, our results show that the double mode random lasing emission from ZnO nanosheets strongly depends on the region of the sample illuminated by the pump laser.
© 2018 Optical Society of America
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