Influence of Laser Wavelength (532 nm vs 1064 nm) on Plasma Diagnostics and Self-Absorption in LIBS of Titanium for Automotive Applications

Abstract

Titanium (Ti) metal requires precise compositional analysis because it has crucial importance in automotive applications due to its exceptional mechanical qualities. LIBS is a rapid and non-destructive analytical technique suitable for in situ elemental analysis. However, the technique has some limitations due to low-quality spectra because of self-absorption effects, which are dependent on experimental parameters. The combined effect of laser wavelength and other experimental factors on Tiplasma diagnostics requires further systematic evaluation. This study examines how laser wavelength influences plasma characteristics and self-absorption effects. To conduct experiments under atmospheric conditions, a Q-switched Nd: YAG laser at 532 nm and 1064 nm laser excitations were used with three laser energies (80 mJ, 103 mJ, and 126 mJ) and two time delays (1 µs, 2 µs) to analyze their combined effects on plasma characteristics. The Internal reference method, the Boltzmann plot, and Stark broadening methods were used for self-absorption correction, estimation of electron temperature, and density, respectively. The results show that 1064 nm excitation generates relatively high plasma temperatures. Although 532 nm excitation produced stronger emission intensity and higher electron density, a more pronounced self-absorption effect was observed due to increased plasma density and enhanced ablation under similar conditions. The 532 nm excitation improves emission intensity and diagnostic sensitivity; however, it also requires careful optimization of experimental parameters and self-absorption correction due to stronger self-absorption effects compared to 1064 nm. These findings highlight that wavelength selection is relevant to enhance spectral reliability in Ti LIBS analysis. Self-absorption correction combined with optimized wavelength selection improves spectral consistency and plasma parameter reliability.