Polaritonic sinusoidal gratings

Two-photon polymerization provides the opportunity to create 2.5D metasurfaces of arbitrary shape on various materials. In this work, we demonstrate the ability to produce metallic and metallic-like sinusoidal one-dimensional gratings with the use of a Photonic Professional GT2 Nanoscribe. In particular, we produced metallic-coated sinusoidal gratings with varying periods and heights, capable of sustaining surface plasmon polaritons for both gold and copper. The grating period ranged from 1 to 6.2 μm, while the heights ranged from 1 to 6.2 μm. In the case of gold, the two plasmonic resonances measured are in the range of 2000 to 3500 cm^-1 and 4900 to 7100 cm^-1 with Q factors varying between 0.7 and 6, Similarly, for copper, two plasmonic resonances were measured in the range of 900 to 940 cm^-1 and 5800 to 6600 cm^-1 with Q factors varying between 0.5 and 5. We also produced 4H SiC sinusoidal gratings that support surface phonon polariton resonances within the Restsrahlen band between 797 cm^-1 and 972 cm^-1. Gratings were produced utilizing the Nanoscribe to produce a grayscale mask that was etched into the SiC substrate to obtain sinusoidal gratings with periods also varying from 1 to 6.2 μm while the heights were varied from 0.3 to 2 μm. In this case, as expected from a low-loss plasmonic-like polar dielectric, the Q factors of the resonances within the Restsrahlen band were in the range of 50-110. To understand the origin of these surface plasmon and surface phonon polariton resonances, we performed finite element calculations using COMSOL.