Femtosecond-nanosecond Double-pulse Laser-induced Breakdown Spectroscopy

In recent years,laser-induced breakdown spectroscopy(LIBS),as an emerging element analysis technology,has developed rapidly with a promising application prospect.It works by focusing a high-energy laser pulse on the surface of the sample to produce the plasma,analyzing the spectral emission of the produced plasma and then through the spectrum to infer its element composition.Compared with other traditional analytical methods(e.g.,X-ray fluorescence spectrometry,inductively coupled plasma atomic emission spectrometry,etc.),LIBS has many advantages in the following aspects: the applicability to any type of sample(gases,liquids,and solids),the capability of simultaneous multi-element analysis,nearly nondestructive nature,the standoff sensing capability,normally no need for sample preparation,in situ and remote analysis.Due to these unique advantages,LIBS can benefit many application fields,including environment,industry,geology,art,medicine and nuclear safety.Therefore,the research on LIBS technology is of great significance to people’s production and life.In order to better develop LIBS technology,most researchers have turned their attention to enhancing the spectral intensity of LIBS and improving the accuracy and precision of LIBS.Until now,they have proposed many different methods,such as double-pulse LIBS,resonance-excited LIBS,femtosecond LIBS,nano-particle enhanced LIBS,and spatial confinement LIBS,of which the double-pulse LIBS has unique advantages in remote detection.The long distance weakens the collected spectral emission intensity.However,researchers have paid little attention to improving the LIBS remote detection capability,but only focus on enhancing the plasma spectral intensity,improving the sensitivity and stability of detection,reducing the detection limit,or improving the SNR and SBR.They ignored the application research of LIBS technology as its greatest significance.Improving the long-range detection capability of LIBS is an important basis for promoting the application of LIBS.The current solution is to use femtosecond-nanosecond collinear double-pulse LIBS technology to remotely excite the sample to be measured to generate a plasma spectrum,so as to increase the spectral intensity of the corresponding plasma.That is to say,the research aim of this thesis is to enhance the plasma spectral intensity,detection sensitivity and so on for the future development and application.The main contents of this paper are as follows:1.To study some previous research achievements: special confinement LIBS,pre-heated LIBS,and the effect of sample surface and focal distance on LIBS,etc.It has been clearly shown that these methods can enhance the spectral emission intensity,but compared to femtosecond nanosecond collinear double-pulse LIBS,these methods all use the nanosecond double-pulse LIBS,which cannot enhance the spectral intensity in remote detection.This comparison provides a sufficient research background for later work.2.To propose the scheme of femtosecond-nanosecond double-pulse LIBS and discuss the plasma spectral intensity by detecting typical materials in semiconductor materials(silicon),metal materials(Cu),and organic materials(PMMA).The research is of great significance because it can enhance the spectral intensity,sensitivity,and signal-to-background ratio based on widening practical applications.In summary,the innovation of this thesis lies in the femtosecond-nanosecond collinear double-pulse LIBS’ improvement in practical applications(remote detection),and its significant role in enhancing the spectral intensity.This scheme has great guiding significance for practical application and enhancement.