Remote Elemental Analysis by Laser-Induced Breakdown Spectroscopy Using a Fiber-Optic Cable

The elemental composition of solids can be determined rapidly and simply with the use of laser-induced breakdown spectroscopy (LIBS). This method, described in detail elsewhere, uses powerful laser pulses to form a microplasma or spark on a sample. A small amount of material is vaporized, and emitting species in the plasma are identified by spectrally and temporally resolving the spark light. Although LIBS measurements can be performed remotely on solids at distances up to 24 m from the laser and detection system with a long-focal-length lens, this method has some disadvantages including safety (the possibility of ocular damage by the high-energy laser pulses), need for a clear line of sight to the analysis area, scattering of incident pulse energy by dusts or fogs, and problems associated with precise focusing of laser beams at long distances. In particular, the plasma will preferentially form on dust particles in front of the sample because of the long Rayleigh length of the focused beam.