Near-to-Far Field Transformations for Radiative and Guided Waves

Abstract

Light emitters or scatterers embedded in stratified media may couple energy to both free-space modes and guided modes of the stratified structure. For a comprehensive analysis, it is important to evaluate the angular intensity distribution of both the free-space modes and guided modes excited in such systems. In the present work, we propose an original method based on Lorentz reciprocity theorem to efficiently calculate the free-space and guided radiation diagrams with a high accuracy from the sole knowledge of the near-field around the emitters or scatterers. Compared to conventional near-to-far field transformation techniques, the proposal allows one to easily evaluate the guided-mode radiation diagrams, even if material dissipation is present in the stack, and thus to simultaneously track the coupling of light to all channels (i.e., free-space and guided ones). We also provide an open-source code that may be used with essentially any Maxwell’s equation solver. The numerical tool may help to engineer various devices, such as light-emitting diodes or nanoantennas, to achieve directional and efficient radiative spontaneous decays in free-space and guided optics.