Optical on-line controllable filters based on photorefractive crystals

Multi-Channel Adaptive Interferometers Based on Dynamic Hologram Multiplexing

“…Note as well that such a demultiplexer can be also built on the basis of dynamic holographic grating recorded in a PR crystal (Hukriede, et al, 2003;Petrov, et al, 2001;Petrov, et al, 2003;Runde, et al, 2005). The scheme of such photorefractive band-drop filter proposed in (Petrov, et al, 2003) is shown in Fig. 24.…”

“…26 which shows experimental dependence of central wavelength on the angle , the change of the latter leads to shift of B  by 80 nm (from 1480 to 1560 nm). Authors (Petrov, et al, 2003) note that shift of the Bragg wavelength has no observable effect on the form of the transfer function and the diffraction efficiency. The speed of tuning was determined by the recording time of the dynamic hologram and was about 0.5 s. The central wavelength of the filter based on a photorefractive grating can be additionally tuned electrically by application of external electric field to the photorefractive crystal.…”

Nonlinear Properties of an Integrated Optical Filter based on Photorefractive Gratings in LiNbO3

“…Using equation (2) and the experimentally observed value of the Bragg wavelength for the first harmonic, we calculated the average refractive index of the material (waveguide in our case) 0001 . 0 212 .…”

“…Due to the growing demands of DWDM technology [1], integrated optical filters based on Bragg reflection from a holographic grating are one of the most sought-after due to their high selectivity and narrow bandwidth [1,2]. Lithium niobate is a widely used material for integrated optics due to its remarkable acousto-and electrooptical properties.…”

Photorefractive Polymers

“…Illumination with uniform intensity distribution of appropriate wavelength will erase any grating that has already been written inside the material, making them suitable for reversible and real-time holography. Many applications such as multiplexed data storage [2], holographic filters [3], neural networks [4], and updatable 3D display [5] have been demonstrated on a laboratory scale, but commercial products are not yet available mainly because of the strict requirements on material quality and the complexity of the optics required to implement these systems. Early searches for better materials had been concentrated on inorganic crystals, but after the invention of polymer PR materials, significant research efforts have directed to this class of materials as well due to the ease of processability, which is an advantage over inorganic crystals.…”