Abstract
Metasurfaces with sub-wavelength features are useful in modulating the phase, amplitude or polarization of electromagnetic fields. While several applications are reported for light manipulation and control, the sharp phase changes would be useful in enhancing the beam shifts at reflection from a metasurface. In designed periodic patterns on metal film, at surface plasmon resonance, we demonstrate Goos-Hanchen shift of the order of 70 times the incident wavelength and the angular shifts of several hundred microradians. We have designed the patterns using rigorous coupled wave analysis (RCWA) together with S-matrices and have used a complete vector theory to calculate the shifts as well as demonstrate a versatile experimental setup to directly measure the shifts. The giant shifts demonstrated could prove to be useful in enhancing the sensitivity of experiments ranging from atomic force microscopy to gravitational wave detection.
Highlights
Metasurfaces are 2-dimensional equivalents of metamaterials with features smaller than the wavelength designed to modulate the phase, amplitude or polarization of electromagnetic field
There is a large modulation of the complex amplitude of the reflected field as is the case close to the critical angle in total internal reflection (TIR) and during the excitation of various surface modes
General theoretical models to calculate the shifts for incident beam of any polarization has been presented[29], as well as a unified model applied to harmonic generation by which the second harmonic beam generated at a metallic interface is shown to experience the shift[30]
Summary
Metasurfaces are 2-dimensional equivalents of metamaterials with features smaller than the wavelength designed to modulate the phase, amplitude or polarization of electromagnetic field. A beam reflected off an interface experiences spatial and angular shifts depending on the polarization and the beam profile. Artmann calculated the GH shift by combining the Fresnel coefficients with the expressions for phase shift for a plane wave and showed that there is polarization dependence in the lateral shift[10] This has been viewed as a consequence of the presence of an evanescent component of the field beyond the interface. Bretenaker et al.[18] demonstrated a novel way of measuring the GH shift in single reflection by making use of the difference in the s- and p-polarized reflected beams This was followed by the study of enhanced shifts at a Wood’s anomaly in a metallic grating[19]. We proceed to demonstrate a robust high resolution experimental setup that can directly measure the plasmon enhanced shift of p-polarized beam with respect to an s-polarized reference beam
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