Double-pulse YAG:Nd³⁺laser with a controllable delay in the 20–100 ns range

Abstract

UV emission of silicon oxide molecules observed from a non-thermal atmospheric pulsed dielectric barrier discharge was experimentally explored in a spectral range from 228 to 253 nm. The main vibrational bands (1, 1), (2, 2) and (0, 1) of A 1 -X 1 + electronic transition were investigated. Corresponding synthetic spectra was built up and adjusted with good agreement. Excitation temperatures (T vib , T rot ) were deduced as a function of gas composition. It is shown that the rotational temperature can represent a non-intrusive diagnostic of plasma gas temperature in process control.

Laser ablation comparison by picosecond pulses train and nanosecond pulse

“…However, shorter laser pulses (picosecond and femtosecond) can improve some LIBS features [8][9][10]: fractional evaporation dampening, decreased ablation threshold, smallest or absence of heat affected zone, the most careful laser sampling due to smallest ablated mass per single laser pulse. A dramatic improvement of LIBS analytical capabilities was achieved by introducing a double pulse technique [11][12][13][14][15]. Splitting the laser pulse into two parts with a delay of several microseconds resulted in an increase of plasma emission of up to two hundred times thus improving LIBS sensitivity.…”

Laser beam profile influence on LIBS analytical capabilities: single vs. multimode beam

“…Depending on used Nd:YAG laser model a wide variety of output laser characteristics can be obtained: output wavelength; pulse duration; double pulse mode; beam profile. Beam profile can be different depending on laser model 8 : a Gaussian (single mode, TEM 00 ) profile for higher stability and smaller laser spot; multimode (TEM xy ) profile for higher energy; super-Gaussian profile for higher energy; flat-top profile; "camomile" beam profile 9 . It should be noted that other output laser characteristics are also depend on chosen resonator type (stable, unstable) and lasing regime (single mode or multimode).…”

Laser induced breakdown spectroscopy with picosecond pulse train

“…Picosecond and femtosecond laser pulses can be a better laser source for some specific LA ICP MS and LIBS applications due to particular features of short and ultrashort laser ablation like the absence of a heat affected zone and the smallest laser crater dimensions (elemental mapping), decreased ablation stress for nearby areas in the case of biological samples analysis, absence of fractional evaporation and the small ablation mass [8][9][10][11][12][13]. An alternative way to improve LIBS analytical performance is Laser Physics Letters Laser induced breakdown spectroscopy with picosecond pulse train to use a so-called double pulse technique which utilizes two successive nanosecond laser pulses with microsecond delay for ablation [14][15][16][17][18][19]. Double pulse LIBS results in significant improvement of the signal-to-noise ratio and reproducibility thus enhancing sensitivity and accuracy of LIBS analysis due to laser ablation mechanism changes [17].…”

“…An alternative way to improve LIBS analytical performance is Laser Physics Letters Laser induced breakdown spectroscopy with picosecond pulse train to use a so-called double pulse technique which utilizes two successive nanosecond laser pulses with microsecond delay for ablation [14][15][16][17][18][19]. Double pulse LIBS results in significant improvement of the signal-to-noise ratio and reproducibility thus enhancing sensitivity and accuracy of LIBS analysis due to laser ablation mechanism changes [17].…”