Research On Laser-ablation Laser-induced Breakdown Spectroscopy Based On One Laser

LIBS (Laser-Induced Breakdown Spectroscopy) technology has the capability of fast onlineanalysis of elements of the sample with real-time in stu, which making it achieved rapiddevelopment in a wide range of research interests in the field of industry, environment andspace. But LIBS has low analytical sensitivity and its accuracy is susceptible to matrix effects.Dual-pulse LIBS (DP-LIBS) is addressed to solve for these shortcomings, which is one of thebetter technologies being rapidly developed in recent years.This paper presents a new dual-wavelength Laser-Ablation Laser-Induced BreakdownSpectroscopy (LA-LIBS) based on one single laser. The so-called dual-wavelength LA-LIBSis a minor adjustment of reheating orthogonal configuration of DP-LIBS. The first pulse isused to ablate a little mass of sample materials; the second pulse is used as an excitation lightsource to the sample. The focuses of two light beams focusing in space separates someappropriate distance and the time of the two beams of light reaching at the sample target alsogets some separated; then we can realize a time and space separation while ablating samplematerials and then subsequently re-exciting the plasma produced by the first pulse withsample target. By using of multi-wavelength outputs of the Nd: YAG solid-state laser, weapply the short wavelength, low-energy laser beam as the LA light source, which can improvethe spatial resolving power; with the near-infrared wavelength, high energy laser beam as theexcitation light source to ensure a high sensitivity analysis of LIBS.Since there is no delay time between the two beams of a single laser output, the paper hascome up with an innovative method: we utilize quartz glass optical fibers with large diameterto transmit high-power laser energy to get delayed between two laser beams. We have studiedthe laser coupled transmission properties of Thorlabs’600μm,800μm,1000μm and910μmcore diameter silica fiber. We discussed the conditions of laser coupled into fiber, thepreparation of fiber end face and the laser damage mechanism to the fiber end face and itseffect on the coupling efficiency of laser and quality of laser beam out from fiber. Weconcluded that the best focus lens is of length between15and20cm; and the best distancebetween the laser focus point to the fiber end face is5~10mm. In order to get enhanced spectroscopy of plasma, we need to get higher laser power density. So we tried differentcollimators and different re-focus lens to get better choice. Finally, we take advantage of thedual-wavelength LA-LIBS based on optical fiber delay to analyze alloy samples of Al, Cu,and Ag. We obtain a better result of4-fold enhancement of Cu signal to background thanusing single LIBS. Then we verify the feasibility of the dual-wavelength LA-LIBStechnology based on optical fiber transmitting energy.