Propagation characteristics and characterization challenges of complex laser field distributions

The paper presents the propagation characteristics of several complex laser field distributions. It also outlines the challenges associated with characterizing laser fields based on their M2 parameter. To alleviate the challenges, we introduce a new beam characterization technique for defining the propagation characteristics of arbitrary laser beams. The new technique is based on calculating laser beam propagation characteristics as a function of the field’s lateral coordinates, and provides a quantitative way of accounting for the fractional beam power diffracted outside of the beam central node. The technique, called FM2 (FM-squared), accounts for the spatial evolution of the M2 beam quality parameter. It provides insights into the beam quality of laser beams, including the quality of laser beams affected by diffraction or by wavefront distortions, as well as the complex field distributions resulting from a coherent superposition of the individual beams contained within optical phased arrays.