Abstract
Laser-induced breakdown spectroscopy (LIBS) is a useful tool for determination of elements in solids, liquids, and gases. For nanosecond LIBS (ns-LIBS), the plasma shielding effect limits its reproducibility, repeatability, and signal-to-noise ratios. Although femtosecond laser filament induced breakdown spectroscopy (FIBS) has no plasma shielding effects, the power density clamping inside the filaments limits the measurement sensitivity. We propose and demonstrate plasma-grating-induced breakdown spectroscopy (GIBS). The technique relies on a plasma excitation source—a plasma grating generated by the interference of two noncollinear femtosecond filaments. We demonstrate that GIBS can overcome the limitations of standard techniques such as ns-LIBS and FIBS. Signal intensity enhancement with GIBS is observed to be greater than 3 times that of FIBS. The matrix effect is also significantly reduced with GIBS, by virtue of the high power and electron density of the plasma grating, demonstrating great potential for analyzing samples with complex matrix.
Highlights
Laser-induced breakdown spectroscopy (LIBS) is one of the most effective tools used to study the interaction between lasers and matter
The exposure time of the spectrometer is set as 0.05 s, considering the pulse interval of 0.001 s of the 1 kHz repetitive femtosecond pulses, which means that each spectrum obtained under the integrate-on-chip mode is accumulated with 50 shots
The signal intensity of the Si line obtained by the grating-induced breakdown spectroscopy (GIBS) is about 3 times higher than that obtained by the Filament-induced breakdown spectroscopy (FIBS) using the same pulse energy
Summary
Laser-induced breakdown spectroscopy (LIBS) is one of the most effective tools used to study the interaction between lasers and matter. Like atomic absorption spectroscopy and inductively coupled plasma optical emission spectroscopy, LIBS has some unique advantages including the capacity of direct analysis without a complex pretreatment of the sample, rapid response, and multiple elemental analysis ability. Due to some adverse impacts like laser emission intensity, long pulse duration, and plasma shielding effect,[11] the ns-LIBS has drawbacks, including low reproducibility and repeatability, low signal-to-noise ratios, and difficult molecular measurements. The pulse duration of femtosecond lasers is much shorter, such that there is no plasma shielding effect and the interaction time of laser and matter is very short. Signal-to-background ratios and Filament-induced breakdown spectroscopy (FIBS) combines the LIBS technique and a femtosecond laser filament. Signal-to-background ratios and Filament-induced breakdown spectroscopy (FIBS) combines the LIBS technique and a femtosecond laser filament. 17
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