Investigation On Passively Q-switched Characteristics Of The Novel Material Gold Nanocages

Q-switched pulse laser has been widely used in biomedical,machining,military science,remote sensing and other fields due to its advantages of stable output pulse,high peak power and low requirements for the external environment.Along with the rapid development of pulsed laser,saturable absorber as the core component has become the research focus of many researchers.A large number of new saturable absorbers are emerging,such as graphene,carbon nanotubes,topological insulators and so on.But these new materials have the same shortcoming that is the coverage of absorption peak is too large lead to that they can't only be used in a single wavelength.The appearance of gold nanomaterials has successfully solved this problem.By changing the size of the gold nanomaterials,the position and shape of the absorption peak can be changed to achieve absorption at a specific wavelength expediently.Particularly,gold nanocages,because of the special structure of internal hollow and porous wall,not only can change the position of absorption peak by changing size,but also can change the relative strength of scattering cross section and absorption cross section by changing porosity,whose parameters can be controlled more accurately.In this paper,the passively Q-switched characteristics of the novel material gold nanocages in solid-state laser are studied.Gold nanocages as saturable absorber were placed inNd:YVO4,Nd:GAGG and Nd:YAG solid-state lasers to study their output pulse characteristics at the wavelengths of 1064 n,,1106 nm and 1123 nm.The passively Q-switched performance of gold nanocages in solid-state laser is analyzed by the parameters of the Q-switched pulse.The specific research work is as follows:1.According to the optical properties and preparation method ofgold nanocages,the advantages derived from its unique structure are analyzed.The saturable absorption characteristics of gold nanocages are measured and studied.Gold nanocages were used as saturable absorber to explore its Q-switched performance in Nd:YVO4 laser.Two resonant cavities designed with different transmittance were used and we obtained the output pulse of 1064 nm.When the pump power is 5.98 W and the average output power is 211 mW,the narrowest pulse width of 143 ns and the maximum repetition frequency of 467 kHz were obtained at a transmissivity of 4%2.We studied 1106 nm Nd:GAGG passively Q-switched solid-state laser based on gold nanocages which is the first time that using gold nanocages and Nd:GAGG crystal in the same laser.Although the final output poweir is low due to excessive loss,the passively Q-switched pulse is still obtained,which proved the feasibility of passively Q-switched in Nd:GAGG laser based on gold nanocages.When the pump power is 7.69 W.the maximum average output power of the obtained output pulse was 121 WThe minimum pulse width was 370 ns and the repetition frequency was 170 kHz.The corresponding light conversion efficiency was 1.6%3.The 1123 nm Nd:YAG Q-switched lasers with MoS2 and gold nanocages as saturated absorbers were studied respectively In the passively Q-switched laser with MoS2 saturable absorber,when the power of the incident pump light is 6.81 W,the Q-switched pulse with the maximum output power of 208 mW,the narrowest pulse width of 412 ns and the maximum repetition frequency of 233 kHz were obtained.In the passively Q-switched laser with gold nanocages saturable absorber,when the power of the incident pump light is 6.04 W,the Q-switched pulse with the maximum output power of 221 mW,the narrowest pulse width of 253 ns and the maximum repetition frequency of 326 kHz were obtained.It is proved that gold nanocages has better passively Q-switched performance than MoS2 at 1123 um and is a potential saturated absorber.