Nanophotonics refers to the study of interaction of nano-scale material structures with light. Compared to the usual bulk materials, the interaction of light with sub-wavelength structures offers several new properties that are counterintuitive to our usual notions of reflection, refraction and diffraction. For example, nanoscale structures on peacock feathers reflect stunning colors, a class of materials called “meta-materials” can show negative values of the refractive index over certain wavelength ranges, and by means of metallic nano-structures light can be confined to a length scale much smaller than the traditional diffraction limit. With such exotic properties under investigation, nanophotonics has become an active research area with potential for a diverse range of applications. One of the biggest challenges in the engineering of nanophotonic structures is to design a structure so that it can show a desired physical property that is likely to be significantly different from the bulk counterpart of the same material. This requires modelling of the interaction or propagation of light in nanophotonic structures and efficient computational tools are required for this purpose.
For several nanophotonic structures such as waveguides, cavitives and sources, ultimately the usable or detectable light is collected in the far field and the properties of these devices thus depends on the details of coupling of fields to free space. The authors of this JOSA A article describe a novel open geometry Fourier modal method that combines open boundary conditions (as opposed to artificial absorbing boundary conditions such as PML) and non-uniform k-space sampling. Successful artefact-free modelling of several structures such as dipole emitters near interface or in nano-waveguides, interaction of light with metallic nano-wires has been demonstrated. Efficient convergence properties of this method with regard to the degrees of freedom in the problem can potentially make this approach an important alternative to existing methods in the literature.
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