Analysis of near-field effects in artificial dielectric structures using rigorous coupled-wave analysis

Abstract

Artificial dielectric (AD) materials, where the optical properties of a material are altered through the introduction of subwavelength periodic structuring, have extensive applications in optoelectronic and photonic components to implement properties such as antireflectivity, birefringence, or tuning of the refractive index. However, as the sophistication of AD structures grows, a detailed understanding of the near-field effects in the structure becomes critical. For dense device integration or multifunctional device designs, near-field effects may result in performance degradation. A tool capable of accurately modeling the near fields in an AD is crucial for the study of these effects and for advanced device design. In order to achieve these goals, we have developed a new method which extends the capabilities of rigorous coupled-wave analysis (RCWA) to compute the internal (in addition to the external) fields of an AD with quasimonochromatic or ultrashort pulse illumination. We then apply this technique to investigate one important application of near-field effects: field concentration within an AD. For example, in the study of nonlinear optical interactions with matter, ultrashort pulse lasers are commonplace, as the nonlinear effects are greatly enhanced by the extremely high peak power resulting from the temporal concentration of the field. By using an appropriate AD structure, field localization in the transverse direction can also be achieved. To demonstrate this idea, we design two AD structures that rely on transverse field concentration: (i) a device which exhibits field confinement in the transverse direction when illuminated by an ultrashort optical pulse, thereby allowing enhancement of nonlinear effects; and (ii) a multifunctional device combining an effective l-D photonic crystal (PC) color filter with an AD for field localization, allowing for enhanced detection efficiency.