Energy Efficiency of Radiation Input/Output in Planar Waveguides with Holographic Reflection Gratings

Some experimental data on the energy efficiency (EE) of radiation input/output throughout the entire path of its propagation in a medium of photopolymer holographic gratings and a planar waveguide were obtained and analyzed. It was established that the major contribution to radiation power losses is made by absorption in the photopolymer medium due to incomplete decoloration of the dye during the postprocessing of holograms and a relatively low diffraction efficiency (DE). Due to incomplete matching between the spectral characteristics of reflection holograms and LED displays, the power of their radiation is only partially used as a useful signal. Taking into account the experimental data, the final EE estimate is ~10% relative to the LED emission power at the input of the entire input/output gratings–waveguide structure. To increase this parameter, it is necessary to apply recording media with a small thickness (less than 10 μ m) and, at the same time, with a high amplitude of photoinduced change in the refractive index to provide the necessary DE and degree of matching between the mentioned diffraction characteristics and to decrease absorption in the photopolymer medium. In this case, the desired EE value may attain ~40% .