A grating coupler may be fabricated by exposing a photopolymer layer to grating forming light for forming periodic refractive index variations in the photopolymer layer. The photopolymer layer may be exposed to apodization light for reducing an amplitude of the periodic refractive index variations in a spatially-selective manner. The apodization may also be achieved or facilitated by subjecting outer surface(s) of the photopolymer layer to a chemically reactive agent that causes the refractive index contrast to be reduced near the surface(s) of application. The apodized refractive index profile of the gratings facilitates the reduction of optical crosstalk between different gratings of the grating coupler.

The invention relates to a scaled holographic medium comprising a layer construction B′-C1′-C2′, to a process for producing the sealed holographic medium, to a kit of parts, to a layer construction comprising a protective layer and a substrate layer and to the use thereof.

The invention relates to a scaled holographic medium comprising a layer construction B′-C1′-C2′, to a process for producing the sealed holographic medium, to a kit of parts, to a layer construction comprising a protective layer and a substrate layer and to the use thereof.

The present invention relates to photopolymer comprising a photopolymerizable component and a photo initiator system. Further aspects of the present invention are a holographic media which comprises such a photopolymer, a display which comprises such a holographic media and the use of such a holographic media to make chip cards, security documents, bank notes and/or holographic optical elements especially for displays.

The present invention relates to photopolymer comprising a photopolymerizable component and a photo initiator system. Further aspects of the present invention are a holographic media which comprises such a photopolymer, a display which comprises such a holographic media and the use of such a holographic media to make chip cards, security documents, bank notes and/or holographic optical elements especially for displays.

The present invention provides a novel photopolymer formulation comprising matrix polymers, writing monomer and a photoinitiator and further comprising a compound of formula (1) ##STR00001##
where A.sup.1, A.sup.2 and A.sup.3 are each independently hydrogen, fluorine, chlorine, bromine or iodine, R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are each independently hydrogen, halogen, cyano, nitro, amino, alkylimino, azide, isonitrile, enamino, formyl, acyl, carboxyl, carboxylate, carboxamide, orthoester, sulphonate, phosphate, organosulphonyl, organosulphoxidyl, optionally fluorinated alkoxy or an optionally substituted aromatic, heteroaromatic, aliphatic, araliphatic, olefinic or acetylenic radical while suitable radicals may be connected together via bridge of any desired substitution, or in that two or more compounds of formula (I) may be connected together via at least one of the radicals R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5, in which case these radicals therein constitute a 2- to 4-tuply functional bridge, with the proviso that at least one of the radicals R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 is not hydrogen. Further subjects of the invention are a photopolymer comprising matrix polymers, a writing monomer and photoinitiator, a holographic medium comprising a photopolymer formulation of the present invention or being obtainable by use thereof, the use of a holographic medium of the present invention and also a process for producing a holographic medium by using a photopolymer formulation of the present invention.

The purpose of the present invention is to provide a hologram reproducing apparatus and a hologram reproducing method, which are suitable for reproducing hologram. The purpose can be achieved by means of a hologram reproducing apparatus, which reproduces information signals by irradiating an optical information recording medium with reference light, and a hologram reproducing method for the hologram reproducing apparatus. The hologram reproducing apparatus is characterized in being provided with: a polarization conversion section, which converts polarization of diffracted light that is generated when the optical information recording medium is irradiated with the reference light; a light receiving section, which receives the diffracted light having the polarization thereof converted by means of the polarization conversion section; and a servo signal generating circuit section, which generates signals for moving the optical information recording medium or the polarization conversion section using the diffracted light received by means of the light receiving section.

The purpose of the present invention is to provide a hologram reproducing apparatus and a hologram reproducing method, which are suitable for reproducing hologram. The purpose can be achieved by means of a hologram reproducing apparatus, which reproduces information signals by irradiating an optical information recording medium with reference light, and a hologram reproducing method for the hologram reproducing apparatus. The hologram reproducing apparatus is characterized in being provided with: a polarization conversion section, which converts polarization of diffracted light that is generated when the optical information recording medium is irradiated with the reference light; a light receiving section, which receives the diffracted light having the polarization thereof converted by means of the polarization conversion section; and a servo signal generating circuit section, which generates signals for moving the optical information recording medium or the polarization conversion section using the diffracted light received by means of the light receiving section.

To provide a photosensitive composition for hologram recording that enables further improvement in diffraction characteristic. A photosensitive composition for hologram recording that includes at least two kinds of photopolymerizable monomers, a photopolymerization initiator, a binder resin, and a polymerization inhibitor. The at least two kinds of photopolymerizable monomers are a monofunctional monomer and a polyfunctional monomer.

To provide a photosensitive composition for hologram recording that enables further improvement in diffraction characteristic. A photosensitive composition for hologram recording that includes at least two kinds of photopolymerizable monomers, a photopolymerization initiator, a binder resin, and a polymerization inhibitor. The at least two kinds of photopolymerizable monomers are a monofunctional monomer and a polyfunctional monomer.