Signal improvement using circular polarization for focused femtosecond laser-induced breakdown spectroscopy
In the femtosecond laser field with linear polarization, electrons experience alternative acceleration and deceleration during each optical cycle of the pulse. However, a circularly polarized femtosecond laser can continuously accelerate free electrons. The electrons will get higher energy compared with linear polarization. In femtosecond laser ablation of metals, the light absorption mainly is due to free electrons within metals. The spectral emission of plasma generated with a circularly polarized femtosecond laser will differ from that generated with a linearly polarized femtosecond laser. This study investigated femtosecond laser-induced breakdown spectroscopy (LIBS) of brass. The spectral intensity with circular polarization was higher than that with linear polarization. The results demonstrate the capability of a circularly polarized laser to facilitate signal improvement in femtosecond LIBS.