Study On Random Lasing From Dye-doped Liquid Crystal Embedded With Ag Nanoparticles

Noble metal nanoparticles(NPs)can enhance random lasing(RL)because of the localized surface plasmon resonance properties.The plasmonic random lasing have been investigated.However,the plasmonic enhanced RL in liquid crystals(LCs)is not studied in depth.In order to investigate the roles of localized surface plasmon and nematic liquid crystal light scattering in forming coherent random lasing,the random lasing behaviour of dye-doped liquid crystal embedded with Ag NPs(NPDDLC)was studied,and the results have been compared with those of dye-doped liquid crystal(DDLC)and dye-doped ethanol solution with Ag NPs(DDNP)systems.The main conclusions are as follows:(1)We have not observed the random lasing from the thin DDLC sample box;(2)we can achieve the high threshold RL whose threshold is 45 ?J/pulse from the thin DDNP sample box;(3)For DDLC embedded with Ag NPs system,we can observe low threshold RL whose threshold is 5.12 ?J/pulse from the thin sample box;(4)For capillary with diameter of 0.3 mm,we can also observe RL whose threshold is 28 ?J/pulse from NPDDLC sample.We believe that the coherent random lasing primarily stems from the effect of multiple scattering caused by the fluctuations of the nematic liquid crystal director,and the role of Ag NPs on the RL is to enhanced the localized electric field in the vicinity of the Ag NPs and then to improve the efficiency of the absorption and excitation of dye molecules.For the thin NPDDLC sample box,the lasing output intensity is direction-dependent and area-dependent.The considerable output distributed in an angle range of 0°~ 45°deviating from the direction of the pump stripe and the emission intensity gradually increases with the excitation area.