Double-pulsed time differential holographic interferometry.

A unique method for double-pulsed holographic interferometry has been developed and employed in a meter-long theta-pinch experiment. Q-switching of two orthogonally polarized ruby laser beams, using the same lasing medium but different laser cavities, allows pulse separations of 0.2-100 microsec. The double-pulse operation with short pulse separation avoids many temporal aberrations seen in single-pulse systems and allows time differential interferograms of transient phenomena such as seen in theta-pinch plasmas. Orthogonal polarization of the two beams permits background fringe construction without the need for a mechanically introduced planar phase shift.