Temporal and interference fringe analysis of TEM_01* laser modes

Abstract

The properties of TEM₀₁* doughnut modes have been examined by frequency analysis and by two-beam interference. Interpretation in terms of an evolving helix, made up to two orthogonal TEM₀₁ modes of different frequency, is supported by computer simulation of fringe patterns. These patterns are shown to correspond closely with photographic recordings; the implications of the phenomena for the crossed-beam technique in laser velocimetry are outlined. Finally, the possibility of developing a beam of pure helical cophasal surface is discussed and its interference patterns analyzed.