An effective configuration for interferometric measurement of pulsed laser-induced plasma densities

Pulsed laser-induced plasmas evolve in nanoseconds, so instruments to observe that evolution must be very high speed. We have used a Wollaston prism to create interference fringes, and set up a electronic system to obtain synchronization between the main laser and probing laser. By adjusting the delay unit to make the pulse output of probing laser lag behind the pulse output of main laser for different times, the situation of the plasma at different stages can be recorded. The individual interferometric image is captured by a camera frame grabber that is triggered by the incidence of a probing laser signal on a CCD camera; so the induced phase shift pattern is easy to be photographed and analyzed in terms of plasma density. A demonstration of pulsed laser induce plasma from a graphite target is provided.