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Digital Planar Holography

Digital Planar Holography (DPH) is a new technology, developed recently for fabricating miniature components for integrated optics. The essence of the DPH technology is embedding digital holograms, calculated in a computer, inside a planar waveguide. This allows for light propagation in the hologram plane rather than in the perpendicular direction and results in a long interaction path. Benefits of a long interaction path are well known for volume/thick holograms . On the other hand planar configuration provides easy access to the surface, where the hologram should be embedded.
As it is well known, light can be confined in waveguides by a refractive index gradient. Light propagates in a core layer, surrounded with a cladding layer(s), which should be selected the core refractive index N_core is greater than that of cladding N_clad : _Ncore > N_clad. Cylindrical waveguides (optical fibers) allow for one-dimensional light propagation along the axis. Planar waveguides, fabricated by sequential depositing flat layers of transparent materials with a proper refractive index gradient on a standard wafer, confine light in one direction (axis z) and permit free propagation in two others (axes x and y).
Planar waveguide
Planar waveguide
Light wave, propagating through the core, extends to some distinct into the both cladding layers. If the refractive index is modulated in the wave path, light of each given wavelength can be directed to a desirable point.
The DPH technology comprises design and fabrication of the holographic nano-structures inside a planar waveguide, providing light processing and control. There are many ways of modulating the core refractive index, the simplest of which is engraving the required pattern by nanolithography means. The modulation is created by embedding a digital hologram on the lower or upper core surface or on the both of them. According to NOD statement, standard lithographical processes can be used, making mass production straightforward and inexpensive. Nanoimprinting could be another viable method of fabricating DPH patterns.