An electrically controllable plasmonic enhanced coherent random lasing from the dye-doped nematic liquid crystal containing Au nanoparticles is demonstrated. To achieve the optimal control of the RL properties, the polarization of the pump light should be parallel to the rubbing direction of the cells. The lasing output intensity is direction-dependent and the substantial output distributes in an angle range of 0°~30° deviating from the direction of the pump stripe. The coherent feedback associated with the coherent random lasing mainly originates from the cooperative effect of the enhanced localized electric field in the vicinity of Au nanoparticles and the multiple scattering caused by the fluctuations of the liquid crystal director and local dielectric tensor.
We report a plasmonic enhanced low-threshold random lasing from dye-doped nematic liquid crystals with titanium nitride (TiN) nanoparticles (NPDDNLC) in capillary tubes. The NPDDNLC sample yields a coherent random laser with about 0.3 nm in the full width at half maximum (FWHM). We find the laser threshold is decreased by introducing the TiN NPs into the dye-doped nematic liquid crystal sample. The laser threshold decreases with increasing the number density of TiN nanoparticles from 5.613 × 1010/ml to 5.314 × 1011/ml. We suggest that the low-threshold random laser is caused by the cooperative effect of the recurrent multiple scattering and field enhancement in the vicinity of TiN nanoparticles. The localized electric field near the TiN nanoparticles enhances the energy absorption of the dye and strengthens the fluorescence amplification. Moreover, we provide a new parameter (the relative efficiency of the stimulated radiation photons) to quantify the quality of the random laser, and we give expressions for the wavelength, mode, and whole emission spectrum. Finally, we find the emission spectrum depends strongly on the emission angle and we discuss the reasons. These findings provide a simple and efficient way for the realization of low-threshold random lasers with low cost.
Modulation and enhancement of the optical absorption of graphene-loaded plasmonic hybrid nanostructures is one of the important challenges for applications of graphene in advanced nanoelectronic and nanophotonic devices. In this paper, we study systematically the modulation and enhancement of optical absorption of the metal (Au)/graphene/dielectric/metal (Au) (MGDM) structure in visible and near-infrared regions. We find that the absorption intensity of the MGDM structure is significantly enhanced and is about three times higher than the absorption intensity of the traditional metal (Au)/graphene/dielectric (MGD) structure. Next, the dependence of the absorption spectra of the MGDM structure on the parameters of it, the refractive index of the external environment, the refractive index of the dielectric layer, and the graphene Fermi energy is studied. Results show there are optimal parameters of the MGDM structure for maximum absorbance of it. The absorption spectra of the MGDM structure are very sensitive to the refractive index of the external environment and the refractive index of the dielectric layer. Active modulation of the absorption spectra of the MGDM structure is realized by changing the graphene Fermi energy, and the modulation depth can be as high as 27.5%. Finally, the multi-peaks and the broad bandwidth phenomenon of the absorption spectra can be realized by forming a multi-MGDM structure. This study provides a promising platform for the application of graphene in photodetectors, tunable optical modulators, photovoltaic cells, and other plasmonic modulation devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.