Study On Plasmonic Hologram Based On Metallic Nanowire Gratings

Holography is a technique which can record both amplitude and phase of light field. It involves the use of interference recording and diffraction reconstruction respectively. The relief hologram contains sub-wavelength microstructure, which enables three-dimensional images to be made. Laser holographic anti-counterfeiting is a popular method to achieve anti-counterfeiting in the past several decades. Based on this technique, the fabrication of the relief hologram by molding process which is easy to copy has been invented. However, the relief hologram is suffering from counterfeiting, due to the simplex judgement of diffractive intensity. Therefore, we proposed plasmonic hologram(PHG) based on metallic nanowire gratings, of which the microstructure scale is further reduced. The traditional hologram is embedded with periodic sub-wavelength metallic structures, which can help enhance the diffraction efficiency and achieve polarization-sensitivity. Combined with a tiny polarizer, PHG is able to improve the anti-counterfeiting performance. The article has fulfilled the research on PHG both in experiment and theoretical analysis.We studied the process to effectively fabricate PHG and analyzed the diffraction, reflection, transmission and absorption of TM/TE light in PHG. To make hologram embedded with periodic sub-wavelength metallic structure, transmission hologram optical arrangement with flat object to be recorded is a good candidate. Meanwhile, compared with traditional dielectric hologram, PHG expands the differences between TM and TE light in reconstructed images. Further, by use of metal-insulator-metal waveguides model and rigorous coupled-wave analysis, we found that TM polarization can pass through the air slit of MIM waveguide to reconstruct PHG, while TE polarization is cut off by the air slit. Therefore, polarization-sensitivity was achieved. Finally, DiffractMOD software based on rigorous coupling wave analysis was applied to optimize metallic nanowire gratings. To get more polarization-sensitive, it is necessary to take the different wavelengths into consideration when we optimize the width of air slit, height of dielectric grating ridge and thickness of metal film.Due to the peculiar polarized performances, besides stronger anti-counterfeiting, PHG is potentially compatible with liquid crystal for dynamic three dimensional displays.