DMI/MEMS Seminar

Presenter: Prof. Viktor A. Podolskiy, University of Massachusetts Lowell

Light interaction with isotropic materials is fully determined by their refractive indices that govern refraction and emission through Snell's and Purcell laws, respectively. When materials become anisotropic, refraction and often reflection are anomalous: the directions of the beams depend on anisotropy and on orientation of the interface, in addition to direction of the incident beam. In some geometries the angle of incidence is not equal to the angle of reflection, opening the possibilities to significant reshaping of light. In this talk we discuss the implications of anomalous refraction and reflection that accompany hyperbolic dispersion in metamaterials for confining light to the nanoscale and for extracting light from highly confined areas.

We show that in planar structures high confinement (and high Purcell effect) is often accompanied by weak coupling efficiency. In non-planar structures, such as in conical waveguides with hyperbolic cores (photonic funnels), anomalous reflection enables simultaneous enhancement and confinement of the electromagnetic fields, by directing light that originally propagates along the optical axis towards the tip of the properly designed structures. Anomalous reflection can be further utilized to out-couple the emission from lossy (but high-optical-density) modes propagating along critical angle directions, towards low-loss diffraction-limited beams. The latter process may alleviate the trade-off between high Purcell factors and high emission efficiency.