[Delivery of megawatts high energy laser pulse with large core diameter silica fiber and its application in dual-wavelength laser-ablation laser-induced breakdown spectroscopy].

To resolve the contradiction between spatial resolution and analysis sensitivity in single pulse laser-induced breakdown spectroscopy (LIBS), a study on dual-wavelength laser-ablation laser-induced breakdown spectroscopy (LA-LIBS) was carried out by using one Nd : YAG laser which was capable of two laser beam outputs with different wavelengths, where, the second harmonic output, 532 nm laser beam, was used as laser-ablation source, and the fundamental output, 1064 nm laser beam, was delivered with a large core diameter silica fiber to realize nanoseconds time-delay and then used to breakdown the ablated samples. Two laser beams were orthogonally arranged to realize element analysis with high spatial resolution and high sensitivity. Some key techniques on the coupling of 1064 nm laser beam into fiber, the collimation of laser at the fiber end and re-focusing of the laser beam were studied. The energy delivery capabilities of four fibers of different types were studied and the maximum values were determined experimentally. A Q-switched laser pulse with 15 mJ pulse energy was successfully delivered by selecting a 50 meter long silica fiber with 800 microm core diameter and 0. 39 numerical aperture. And 250 ns time-delay was realized. A copper alloy was analyzed by spectra with current established LA-LIBS system and the possibility of realizing dual-wavelength LA-LIBS analysis based on one Nd : YAG laser was demonstrated experimentally. In this technique, only one Nd: YAG laser was required to carry out spectral analysis. It has a few advantages, such as simple equipment structure, and being convenient to miniaturize the whole system etc. This dual-wavelength LA-LIBS technique was suitable for in-situ elements microanalysis for different samples with both high spatial resolution and high sensitivity.