The enhancement and regulation of lasing in dye-doped multi-layer polymer film systems

As a new research hotspot in nano-materials and nano-structures, photoluminescence is widely used in medical imaging, biosensors, integrated devices and other fields because of its excellent optical performance and good stability. The design and fabrication of these nanostructures are expensive and complex, meanwhile, the influence of film structure change on lasing characteristics has not been systematically summarized. Thus, there are still challenges to realizing lasing regulation by using a multilayer film system. In this study, a dye-doped multilayer system was prepared by a convenient spin-coating method on polyethylene glycol terephthalate (PET) film. The effects of sandwich-like film and Au nanoparticles on the lasing characteristics were studied. The results show that the sandwich-like film can form a mirror symmetry plane and increase the photon scattering frequency. Furthermore, the band-gap edge effect can effectively improve the photon gain, enhancing the optical feedback and realizing band-edge lasing. The lasing intensity in the sandwich-like film is nearly 30% higher than that of the bilayer film system at the same pump energy. By adding Au nanoparticles as scatterers, the local electromagnetic field can be enhanced because of the surface plasmon resonance, improving the transition rate of dye molecules. Meanwhile, the photon scattering frequency among the scattering cross-section can also be increased, increasing the interaction between photons and dye. The lasing intensity can be enhanced by 160% at the same pump energy because of the interaction between the plasmon resonance effect and the scattering effect. The fabrication method in this study is convenient and easy to implement, which is conducive to improving the lasing intensity and provides an effective technical way for the realization of a modulated random laser.