Purcell effect of magnetic dipoles in nanofibers

Light-matter interaction can be enhanced in presence of optical cavities and has been studied extensively within the framework of Purcell effect for many decades [1, 2]. This field of study has recently been further enriched by finding that high index dielectric nanoparticle can present metamaterial behaviour [3]. In particular, the report of enhanced magnetic response of an electric dipole at the interface of a nanofiber [4] has opened up a new frontier in the field of light-matter interaction. Motivated by these, our recent effort to experimentally demonstrate enhanced magnetic response in THz regime [5], and the fact that there is no report of Purcell effect of magnetic dipoles in vicinity of optical nanofibers, here, we develop a theoretical/numerical model to describe the radiation of a magnetic dipole in vicinity of an optical fibre. The model allows the calculation of power coupled to guided and radiation modes of optical fibers. Considering the strong magnetic response of an electric dipole at the interface of a nanofiber [5], we investigate electric and magnetic contributions into the first few resonances in the radiation power. In addition, we identify the Whispering Gallery Modes that form in the cross section of the fiber to interpret the radiation resonances. Although the model is general, it provides a valuable tool to understand the experimental results in THz regime, where a combination of electric and magnetic dipoles are present [5].