Demonstration of an optical-coherence converter

Abstract

Studying the coherence of an optical field is typically compartmentalized with respect to its different optical degrees of freedom (DoFs) -spatial, temporal, and polarization. Although this traditional approach succeeds when the DoFs are uncoupled, it fails at capturing key features of the field's coherence if the DOFs are indeed correlated -a situation that arises often. By viewing coherence as a 'resource' that can be shared among the DoFs, it becomes possible to convert the entropy associated with the fluctuations in one DoF to another DoF that is initially fluctuation-free. Here, we verify experimentally that coherence can indeed be reversibly exchanged -without loss of energy -between polarization and the spatial DoF of a partially coherent field. Starting from a linearly polarized spatially incoherent field -one that produces no spatial interference fringes -we obtain a spatially coherent field that is unpolarized. By reallocating the entropy to polarization, the field becomes invariant with regards to the action of a polarization scrambler, thus suggesting a strategy for avoiding the deleterious effects of a randomizing system on a DoF of the optical field.

Classification of propagation-invariant space-time wave packets in free space: Theory and experiments

“…In this sense, the ability to controllably synthesize ST wave packets opens up avenues for laboratory-scale studies of relativistic optical effects [86]. Furthermore, ST wave packets are a realization of 'classical entanglement', which is the analog of multi-partite quantum entanglement applied to the correlations between the different degrees of freedom of a classical optical field [87][88][89][90][91][92]. Most studies of classical entanglement have focused on correlations between discretized degrees of freedom, such as polarization and spatial modes, whereas ST wave packets are an exam- ple of classical entanglement between continuous degrees of freedom (spatial and temporal frequencies).…”

Self-healing of space-time light sheets

“…As such, these ST wave packets maybe useful for time-gated imaging in turbid media or biological samples. Finally, we draw the reader's attention to the fact that the spatio-temporal correlations introduced into the spectrum is the continuous counterpart of the correlations realized between discretized degrees of freedom, such as polarization and spatial modes in 24,25 . In other words, ST wave packets represent optical fields into which continuous 'classical entanglement' has been introduced.…”

Hierarchical Mean-Field $\mathbb{T}$ Operator Bounds on Electromagnetic Scattering: Upper Bounds on Near-Field Radiative Purcell Enhancement

“…Accelerating over the last decade, the adoption of inverse design techniques like "density" ("topology") or level-set optimization in photonics [1,2]-ideally matching structural degrees of freedom to the computational grid-has vastly simplified the challenge of discovering geometries with remarkable optical characteristics, leading to improved designs for wide band-gap photonic crystals [3][4][5], enhanced polarization control [6,7], ultra-thin optical elements [8][9][10], and topological materials [11][12][13]. However, because navigating the immense range of allowed structures in such formulations necessitates reliance on local information (approximations based on function evaluations, gradients, etc.…”