Design and numerical analysis of metallic Ronchi diffraction gratings acting as reflective beam-splitter

Abstract

ObjectiveIn this work, a reflective beam-splitter based on a metallic Ronchi diffraction grating normally illuminated is designed and analysed. This kind of beam-splitter could have potential applications in photonics and optical technologies in which robustness is necessary since it may be manufactured over malleable metallic substrates. MethodsThe main idea under the design is as simple as obligating the zero-th diffraction order to be null. Firstly, scalar approach is performed, showing an approximation to the parameters of the grating necessary to cancel zero-th diffraction order. After that, a more rigorous approach such as Rigorous Coupled Waves Analysis (TE and TM polarization) is used to evaluate the proposed diffraction gratings as reflective beam-splitters. ResultsBeam-splitting is demonstrated for TE and TM polarization with slightly different dimensional parameters of the diffraction grating. Besides, we show how physical height of the grating grooves that allows cancelling zero-th diffraction order for a certain illumination wavelength depends on the metals used to manufacture the grating and its period. The dependence of the grooves height on the period is exponentially decreasing. To complete the analysis, we demonstrate how for a given grating period, the grooves height also depends on the illumination wavelength.