Analysis of a collinear holographic storage system: introduction of pixel spread function

Image formation in a collinear holographic storage system was analyzed. The wavefront from each pixel of a spatial light modulator was regarded as a plane wave in the recording medium, and its wave vector was determined by the position of the pixel. The hologram in the recording medium was treated as the summation of all gratings written by all combinations of two plane waves. The image of a data page was formed by diffraction of the reference waves by all gratings. The results of the simulation showed good agreement with experiment. We introduced the pixel spread function to describe the image formation characteristics. Analysis of the pixel spread function reveals that a radial-line pixel pattern for reference waves gave a sharper image than other reference pixel patterns. It is also shown that a random phase modulation applied to each reference pixel improved the image formation.     

Charge stripe structure in FeTe

We report the STM study on a single-crystalline sample of FeTe at 7.8 K. FeTe is one of the iron-based superconductor. We measured the resistivity and the magnetization of FeTe. FeTe shows SDW transition at 58 K on these measurements. We study the electronic state of FeTe by using STM/STS for observing FeTe from a microscopic viewpoint. We observed the iron layer and the tellurium layer with atomic resolution. Moreover, we discover the charge stripe structure on STM/STS measurement. We find the charge stripe structure is caused by iron atoms from the analysis. The gap structure of 9 meV was observed in tunneling spectra. This gap size is consistent with the SDW gap which is expected from mean field theory with T_N=58 K.     

Test of bell’s inequality using the one-atom micromaser

We examine a local realist bound in the case of a one-atom micromaser. It is shown that such a bound is violated using a simplified treatment of the micromaser. We consider the effect of dissipation in a proposed experiment with the real micromaser. It is seen that the magnitude of violation of a Bell-type inequality depends significantly on the cavity parameters.     

Crystal‐to‐Crystal Photoinduced Electron Transfer Generating Photoacids to Formulate Water‐Borne Photopolymers

Casting a photopolymer solution to form a film, followed by imagewise photoirradiation and subsequent wet development, leads to photolithography. Whereas the wet development is achievable with aqueous alkali, the emission of an organic solvent as a volatile organic compound (VOC) is usually inevitable during the film casting because ingredients of common photopolymers are insoluble in water. We show here a prototype of water‐borne photopolymers dispersed with milled nanoparticles of poorly water‐soluble photoacid generators (PAGs), which undergo solid‐state photolysis to liberate a photoacid to make a poly(vinyl alcohol) film insoluble in water with the aid of an acid‐sensitive crosslinking reagent. The photolysis of onium‐type PAGs is sensitized in the solid state simply by comilling with water‐insoluble sensitizers to extend spectral sensitivity of this kind of photopolymers. Fluorescence quenching measurements revealed that the solid‐state sensitization occurs through exciton migration in sensitizer particles followed by electron transfer to PAG particles.

     

Semi-local units modulo Gauss sums

For the p-th cyclotomic field k, Iwasawa proved that p does not divide the class number of its maximal real subfield if and only if the odd part of the group of local units coincides with its subgroup generated by Jacobi sums related to k. We refine and give a quantitative version of this result for more general imaginary abelian fields. Our result is an analogy of the famous result on “semi-local units modulo cyclotomic units”. Received: 2 May 1997 / Revised version: 11 November 1997     

Photosensitive poly(methacrylates) having styrylpyridinium and styrylquinolinium groups

Three methods to introduce photodimerizable styrylpyridinium or styrylquinolinium groups to methacrylate polymers are described. Among these, copolymerization of methacrylate monomers with methacrylated styrylpyridine or styrylquinoline offered the most convenient procedure to prepare photosensitive polymers because of the excellent solubility of the polymers having the photofunctional groups in high content. Subsequent treatment with p-toluenesulfonic acid to quaternize the pyridine or quinoline moiety made the polymer highly photosensitive. The polymers having a styrylquinolinium group were found to be sensitive to 488 nm light of an Ar laser, and the sensitivity was about 3 mJ/cm² when the content of the photosensitive group was 15 mol %.