All-optical control of phase singularities using strong light-matter coupling

Strong light-matter coupling occurs when the coupling strength between a confined electromagnetic mode and a molecular resonance exceeds losses to the environment. The study of strong coupling has been motivated by applications such as lasing and the modification of chemical processes. Here we show that strong coupling can be used to create phase singularities. Many nanophotonic structures have been designed to generate phase singularities for use in sensing and optoelectronics. We utilise the concept of cavity-free strong coupling, where electromagnetic modes sustained by a material are strong enough to strongly couple to the material's own molecular resonance, to create phase singularities in a simple thin film of organic molecules. We show that the use of photochromic molecules allows for all-optical control of phase singularities. Our results suggest a new application for strong light-matter coupling and a new, simplified, more versatile pathway to singular phase optics.