Demonstration of Laser Phase Correction Using Supersonic Gas Jets

Abstract

Preliminary experiments have been carried out to demonstrate the feasibility of using active gas optics to compensate for distortions in the phase of laser beams. Two parallel supersonic gas jets, in which a simple mechanical control system varied the mean optical density of one of the jets, were placed orthogonal to the beam path. When operated with combinations of He and He-Ar mixtures, phase shifts of ftp to 3?r have been introduced into a HeNe laser beam. The resulting far-field diffraction patterns have been shown to compare well with theoretical predictions for these phase shifts. Qualitative phase restoration has been achieved when a simply distorted laser beam is passed through the jets. Unwanted phase distortions resulting from the waves in the flow in the present nozzle design limited the Strehl ratio to a low value.