||Compared to traditional lasers which need fixed reflection mirrors to form a cavity, random lasers can be generated by using scattering materials to form cavity-like multiple scattering loop paths. There are several unique advantages of random lasers, such as simple fabrication process, small size, low cost, multiple lasing wavelengths, broad solid angle of lasing output. In recent years, random lasers have been employed in speckle-free imaging, medical diagnostics, liquid crystal display and illumination system.|
In this thesis, we demonstrate a random laser from a UV curable gel film consisting of silicon dioxide nanoparticles. The lasing properties of random lasers are discussed by changing the surrounding temperature and pressing the sample. In order to obtain appropriate concentration for the lasing action, we change the concentration of the silicon dioxide nanoparticles in the polymer film. Experimental results show that the 0.2wt% doping concentration of silicon dioxide provides better lasing action, and the lasing threshold is approximately 29.91μJ/mm2.
We then vary the temperature to change the random lasers from the coherent feedback to incoherent feedback with the raising operation temperature. In addition, the emission intensity and the lasing peak are also varied by the operation temperature. Finally, we also observe that the emission can be switched between the coherent feedback and the incoherent feedback by applying the external force, and the intensity and the lasing peak are varied by the curvature of the polymer film.