Coherence vortices: generation and detection [Invited]

Abstract

Since the concept of optical vortices was introduced in 1989, structured light has become a vital area in modern optics. Extending vortex beams to low coherent source has led to partially coherent vortex beams (PCVBs), which combine vortex phase with stochastic fields. PCVBs exhibit unique features, such as correlation singularities or coherence vortices (CVs), that link coherence and topology in light fields. Their tunable coherence allows for controlled beam shaping and improved stability in turbulent environments, offering advantages in optical communication, trapping, and imaging. Recent progress has focused on their theoretical modelling, generation methods, topological charge (TC) measurement, and emerging applications across singular and coherence optics. This paper highlights and discusses recent techniques for generating and detecting vortices in low-coherent light. As an example, a distinctive binary spiral pinhole aperture method is presented to create CVs, illustrating how structured transmittance modulation of an incoherent source enables the formation of CVs within the two-point complex spatial coherence function. The phase component of this function exhibits a helical structure, while its magnitude displays the characteristic doughnut-shaped amplitude distribution associated with CVs. Additionally, a detection approach for determining the TC and phase of a vortex beam embedded in a low-coherent source is also discussed.