Particle Identification by Laser-Induced Incandescence in a Solid-State Laser Cavity

The laser-induced incandescence of a particle of unknown size and composition can be detected simultaneously with the light elastically scattered by the particle, providing information on both the size and composition of the particle. The technique relies on vaporization of the particle; detection of the incandescence signal at the time of vaporization allows determination of the boiling point of the particle, which can in turn be related to the composition of the particle. The elastically scattered signal provides information about the size of the particle and confirmation that it was vaporized. The technique is demonstrated by directing particles through a Nd:YAG laser cavity with ~10^6 W /cm^2 of circulating intensity. Elements such as tungsten, silicon, and graphite, as well as common aerosols such as soot, can be detected and identified