The Preparation And Characterization Of Gold Nanorods And The Study Of Its Ultrafast Optical Properties

Noble metal nanomaterials have been widely used in optical detectors,optical sensors,optical absorbers and other nonlinear optical devices due to their surface plasmon resonance effect(SPR).As a noble metal nanomaterial,gold nanorods have two SPR peaks,one is transverse surface plasma resonance peak(TSPR)and the other is longitudinal surface plasma resonance peak(LSPR).The LSPE is particularly sensitive to the aspect ratio of the gold nanorods.By adjusting the aspect ratio of the gold nanorods,the LPSR can be flexibly tuned in a widely spectral ranging from visible to near-infrared band.This characteristic makes GNRs have widespread application prospect in chemistry,biology,optics and other areas.In recent years,mode-locked and Q-switched fiber lasers by using GNRs as SA have been demonstrated at different wavebands(1 ?m,1.56 ?m,and 2 ?m).Acquiring solitons with shorter pulse duration,however,is a further goal for researches.Generally,fiber laser would work in one of the multi-soliton states.Nevertheless,coexistence between different kinds of multi-soliton states could also be generated in a passively mode-locked fiber laser by precisely adjusting and optimizing the cavity parameters.Gold nanorods,as a promising SA,could be used to generating special kinds of multi-pulse in fiber laser cavity for further research.Gold nanoparticles,gold and silver alloy nanoparticles and gold nanorods were firstly prepared and systematically characterized.By adjusting aspect ratio,we fined the gold nanorods with appropriate aspect ratio and used as saturable absorbers.The gold nanorods saturable absorbers were compounded with tapered fiber to make saturable absorption devices,and then applied in fiber lasers to mode-locked.The research results are as follows.(1)The aspect ratio of the prepared gold nanorods ranged from 2.5 to 8.5,with an average particle size of 58.7 nm.An aqueous solution of gold nanorods saturable absorbers was dropped onto a tapered fiber and injected laser into the tapered fiber.Under the interaction of evanescent field,the saturable absorption device were made and be putted into the Er-doped fiber laser.After optimizing the parameters of nonlinearity,birefringence and dispersion in the cavity,a 100-femtosecond pulse was generated successfully.The saturable intensity of the gold nanorod in this paper was 266 MW/cm2.The modulation depth was 0.6 percent.The 3 dB spectral width of the generated traditional soliton is 5.2 nm.The central wavelength is 1561 nm.and he half width at half maxium of the pulse are?100 femtoseconds.(2)By adjusting the polarization direction of the cavity,soliton molecules with a spectrum modulation period of 3.3 nm and a pulse modulation interval of 2.238 ps were directly obtained.The most important is that after increasing the power,a gth harmonic soliton molecule pulse was obtained in the laser cavity for the first time.The results show that gold nanorods,as a promising high-performance saturable absorber,have a broad application prospects in the field of ultrafast photonics and needs to be further researched on the generation of special kinds of multi-pulses in the fiber laser cavity.