High selectivity of surface-plasmon polaritons on wavelength can be used for reconstruction of color holograms illuminated with white light. In such a case, a combination of plasmonic filter and holographic microstructure is used. Compared to other techniques for creating holograms for white light reconstruction, such as rainbow holograms, the plasmonic approach offers full angle color reconstruction.
The plasmonic structure consists of a holographic grating recorded in a photo-resist material and a thin metallic layer on top of the grating. The parameters of both components are tuned to transmit only a selected spectral range when illuminated with white light. For RGB reconstruction three independent structures can be combined on a single substrate.
An excitation of plasmonic effects usually requires a relatively complicated setup containing prisms for in-coupling of optical waves. In this paper, a modification of the plasmonic hologram is proposed, which consists of two gratings recorded on opposite surfaces of a substrate. The first grating serves as an in-coupling element which also partially tunes the spectral transmittance of the structure. The second grating is metallized and out-couples the energy stored in the surface plasmon to a transmitted wave.
However, there is still a problem of diffraction efficiency of such transmission holographic structures. In order to optimize the transmittance and spectral selectivity, numerical simulations of light propagation through the plasmonic structure have been performed using MEEP software. The dependencies of transmitted light on various parameters of the diffraction gratings and metallic layer are discussed in detail.