The photopolymer materials are good media to record thick hologram gratings, because photopolymer materials have high resolution, low cost, simple process technology and so on. According to coupled wave theory for thick hologram gratings, we know that the same object beam can be reconstructed if the same reference beam is used to retrieve a thick hologram grating. However, the shrinkage always occurs in the photopolymer materials because of environment temperature, humidity, vibration etc. For instance, the same object beam cannot be reconstructed even the same reference beam to be used. In this paper, we will analysis the shrinkage influence of photopolymer materials for thick hologram gratings. We divide the photopolymer materials into several geometry layers, and analysis the reconstructed characteristics separately basing on coupled wave theory of Kogelnik. Through gradually continuous changing the angle between gratings and the border (we call it slant angle), we can build the geometry model of gratings bending caused by shrinkage of materials. We calculate wave complex amplitude diffracted from every layer, and superpose them to compute the total diffraction efficiency. We simulate above methods to obtain the curve of diffraction efficiency with reconstruction wavelength by using Matlab software. Comparing the simulated results with the experiments results, we can deduce the probable situation of thick hologram gratings bending after photopolymer materials shrink.
Collinear holographic storage system is one of the advantages of the promising candidate as its unique system design. The wavelength margin is a very important characteristic which can make a laser diode to be used possible as a light source in a holographic storage system, because of the bit-error-rate (BER) of a reconstructed page data pattern will be so high that we cannot decode it correctively, even though the wavelength drift of the diode was small enough. To solve the problem, we studied a method of decreasing BER by adjusting the focal length of the lens to compensate the wavelength drift in the collinear holographic storage system. Once we changed the focal length of the lens, the angles can also be changed to satisfy the Bragg condition. So we find that decreasing the focal length of the lenses can compensate the wavelength drift up effectively and vice versa.
Using conventional wire grid polarizers to manipulate the polarization of deep ultraviolet (DUV) light is generally
known as difficult because of the limits of the current nano-fabrication technologies. To ease the fabrication, two
metallic gratings, Al-air and Al-SiO2 gratings, with periods slightly smaller than the DUV wavelength, were designed to
exhibit an inverse polarizing effect, i. e. with TE transmittance largely exceeding TM transmittance. Both gratings were
experimentally verified to possess inverse polarization transmission, whereas an enhanced TE transmission through Al-
SiO2 grating was observed. By using the Fourier modal method and the planar waveguide theory, we show that the
strong coupling of the incident DUV wave to surface plasmons results in the minimum in TM transmittance, whereas the
coupling to low-loss TE mode leads to the TE transmission through the grating region. By conformally filling the grating
slits with the substrate dielectrics-SiO2, the effective refractive index of the TE guided mode approaching that of the
substrate greatly reduces the reflection of the mode at the grating-substrate interface. Thus, the TE transmittance of Al-
SiO2 grating is largely enhanced compared with Al-air case. At the DUV lithographic wavelength-193 nm, the measured
inverse polarization extinction ratio of Al-SiO2 grating is 103, suggesting itself a qualified compact polarizer for ArF
193 nm lithography system.