Light structured by thermodynamic principles : generation of partially-coherent beams from a few to multiple modes

Abstract

The coherence state of light is important in several optical systems. This state is also subject to variations due to propagation and imperfections present along the propagation path. Even though changes in the coherence state are common, direct measurements are sometimes diff icult and the interpretation complicated, particularly for beams containing few modes. Here, partially coherent beams are analyzed using thermodynamic principles. As far as we know, our approach is novel in the literature and the associated analysis allows to describe partially coherent light from the limit of a few to many modes. Particularly, the beam quality factor, M2, can be associated with an effective temperature for light beams. This link between optics and thermodynamics allows to describe the beam wavefront based on the mean number of available modes and other macroscopic beam effective parameters, such as the beam width, curvature, and divergence angle. Later, ensembles of beams defined by a fixed M2 are generated and statistically analyzed. Holography is used to generate the thermodynamically inspired structured light beams, and the statistical analysis of the beam intensity profiles accounts for the retrieval and characterization of the light coherence state. The present discussion can be useful to light propagation in turbulent media, optical systems with imperfections, metasurfaces, and optical communications systems.