New progress in fiber-optic energy-induced laser-induced plasma spectroscopy

[ China Instrument Network Instrument Development ] Laser-induced breakdown spectroscopy (LIBS) is a spectrometric technique for material composition analysis with fast, in situ, real-time and simple sample preparation. However, the conventional lenticular transmission LIBS has the disadvantages of being bulky and unable to flexibly conduct laser light. In order to solve this problem, in recent years, researchers have proposed the use of optical fibers to transmit the high-energy pulsed lasers required in LIBS, namely fiber-optic energy-induced laser-induced breakdown spectroscopy (FO-LIBS). The FO-LIBS device is highly integrated and can adapt to complex detection environments or remote detection. However, due to the relatively low threshold of fiber-conducting laser energy, the excitation spectrum has weak intensity and self-absorption effects, which leads to low detection accuracy of FO-LIBS.

Experimental setup (a) and custom plasma system axes (b)

Associate Professor Guo Lianbo from the LIBS Research Group of the Laser Advanced Manufacturing Technology Research Group of Wuhan National Optoelectronics Research Center led the master student Lu Wei and others to conduct in-depth research on fiber-optic energy-induced laser-induced breakdown spectroscopy, and proposed the use of spatial resolution technology to observe plasma. Morphology, improve quantitative detection accuracy and suppress self-absorption effect. Taking the three elements of iron, magnesium and zinc in aluminum alloy as an example, the effects of spatially resolved FO-LIBS on the calibration curve and self-absorption were analyzed. The results show that the spatial resolution technique is applied to FO-LIBS, and the optimal acquisition point in the plasma can be selected to significantly improve the accuracy of quantitative analysis. The cross-validation root mean square (RMSECV) is from 0.388, 0.348, 0.097 wt.%, respectively. Increased to 0.172, 0.224, 0.024 wt.%; at the same time, this method can also significantly inhibit the self-absorption effect.

On January 12, 2018, relevant research results were published on the Optics Express, a journal of the Optical Society of America (WJ Lu, ZH Zhu, Y. Tang, SX Ma, YW Chu, YY Ma, QD Zeng, LB Guo, YF Lu, and XY Zeng, "Accuracy improvement of quantitative analysis in spatially resolved fiber-optic laser-induced breakdown spectroscopy," Opt. Express 26, 30409-30419 (2018)).

The work was funded by the National Natural Science Foundation of China (61705064), the Hubei Provincial Department of Education Project (B2016183) and the Hubei Provincial Natural Science Project (2018CFB773).

(Original title: New advances in fiber-optic energy-induced laser-induced plasma spectroscopy)