KR101124841B1 - Novel optical storage materials based on narrowband optical properties - Google Patents

Abstract

A holographic storage medium 60 is disclosed that includes a substrate and a dye material that can undergo light-induced changes. Data can be written to the holographic storage medium using light of one wavelength and read using light of different wavelengths.

Description

NOVEL OPTICAL STORAGE MATERIALS BASED ON NARROWBAND OPTICAL PROPERTIES}

The present invention relates to the storage of digital data using an optical storage medium. More specifically, the present invention relates to holographic storage media having a narrowband optical absorbing material dispersed in a substrate. The narrowband material undergoes a light-induced change upon exposure to light resulting in a large change in its refractive index.

Optical data storage technology has been greatly developed based on surface storage phenomena. For example, in a compact disc (CD), which is one of the most common optical storage formats, data is encoded as a fine change on the surface of a recording medium. The data is read by optical means (usually a laser), similar to the manner in which data recorded in a magnetic medium can be read by a magnetic sensing head or a needle can read data recorded in a vinyl medium. However, unlike vinyl records, in optical storage devices the data is usually stored digitally.

CD technology, and related larger-volume formats, digital video discs or DVDs, started out as read-only formats that store data as metalized micro pits on the substrate surface. The read-only format soon followed a system capable of writing and rewriting. By way of example, a magneto-optical system (the orientation of the magnetic domain changes the direction of polarization rotation of the reflected concentrated light beam); Phase-change systems (the medium may be locally crystalline or amorphous, each state having a different reflectivity); And dye-polymer systems (the reflectivity of the medium is changed by powerful illumination). In all surface-based optical data storage systems, each bit of data occupies a particular physical location in the storage medium. The data density of the optical medium is thus limited by the physical constraints on the minimum size of the recording spot.

In recognition of the limitations imposed by surface-based formats, attempts have been made to develop multilayer systems. Such systems increase data density by applying surface-based storage techniques to individual layers and then integrating to create multilayer media. Such a technique requires a special heterogeneous layered recording medium whose complexity increases rapidly with the number of layers. Due to this complexity, commercially available multilayer DVD optical storage media provide up to two layers of data and are in prerecorded format. Soon-to-be-released Blu-Ray technology also supports multiple layers, but it can only be used as a recordable medium because of the mastery and repeatability of the data format.

A different approach than the traditional surface-based storage system is the volumetric storage technique, which uses the total volume of the storage medium to increase data capacity. The two most common techniques for volume storage are the multilayer and holographic techniques. The multilayer approach uses the multiple optical phenomena that are sensitive to focused rays to record and retrieve data, and thus can handle various depths in the medium by varying the depth of focus. Similar to the approach. The technique eliminates the complexity of fabricating and assembling multilayers and also removes limitations on the number of layers, making it only a function of the focusing capability of the optical system.

On the other hand, holographic storage stores data throughout the volume of the medium via a 3D interference pattern. In the holographic recording process, two light beams, laser light from a signal light beam containing reference light and symbolic data, meet within the volume of the photosensitive holographic medium. The interference pattern from the superposition of the two rays changes or modulates the refractive index of the holographic medium. This modulation in the medium serves to record both strength and phase information from the signal. The recorded intensity and phase data is then retrieved by exposing the storage medium only to the reference ray. The reference ray interacts with the stored holographic data and generates a reconstructed signal ray in proportion to the initial signal ray used to store the holographic image. For information on conventional volume holographic storage devices, see, for example, US Pat. Nos. 4,920,220, 5,450,218 and 5,440,669. In addition, non-destructive reading of volume holographic storage can be performed using different wavelengths in the writing and reading phases (see US Pat. No. 5,438,439).

Typically, volume holographic storage is achieved by writing data in parallel on a holographic medium containing at least 1 × 10 ⁶ bits or on an array or “page”. Each bit is typically stored as part of an interference pattern that generates an exponential modulation for the volume of the holographic storage medium in a given spot, so it is no problem to say it is a spatial “placement” of a single bit. Instead, each bit can be thought of as consuming some small portion of the overall exponential modulation. Storage media that can support large exponential changes can consequently store several pages within the volume of the holographic medium by angle, wavelength, phase-signal or related diversification techniques.

The heart of any holographic storage system is the medium. Demonstration of early holographic storage devices used inorganic photorefractive crystals, such as lithium niobate, in which incident light can cause refractive index changes. This exponential change is due to the photo-induced generation and subsequent capture of electrons, which creates an induced internal electric field that ultimately alters the index through a linear electro-optical effect. However, the efficiency of these materials is relatively poor and large decisions are needed to observe the significant effects. More recent studies have led to the development of organic polymers that can sustain large exponential changes due to optically induced polymerization processes. Such materials are called photopolymers, the most common being based on cationic ring-opening polymerization (CROP). The use of chemically amplified forms greatly improved the optical sensitivity and efficiency of the material compared to lithium niobate. However, since the exponential change is photopolymerized, the material must start a substantial portion of the medium in monomeric form, which tends to make the material gel-like and very sensitive to environmental conditions. As a result, the use of organic materials trades off stability and environmental sensitivity for improved efficiency and optical sensitivity.

In order for holographic data storage by volume to be completed with viable data storage options, the system and storage medium must be developed so that its operation is relatively simple, inexpensive and robust. The first priority of this effort is the development of materials that are not only efficient and light sensitive, but also stable and relatively insensitive to environmental conditions such as temperature and humidity. At the same time, efforts have been made to optimize the reading and recording system for certain material variables in addition to the material development.

Summary of the Invention

The present invention provides a holographic storage medium comprising a substrate having a dye material having optical properties located in a narrow region of the wavelength range. In one aspect, the invention provides an optically transparent substrate; A photochemically active narrowband dye material capable of undergoing light-induced changes embedded in the optically transparent substrate; And one or more photolysis products of said dye. The photolysis products contained in the optically transparent substrate are patterned to provide one or more optically readable data contained in the holographic storage medium in the substrate.

In another aspect, the present invention relates to a method of manufacturing a holographic storage medium. In yet another aspect, the invention relates to a method of storing data on a holographic storage medium.

1 shows a digital holographic storage device for recording data (FIG. 1A) and reading stored data (FIG. 1B).

FIG. 2 shows a diffraction efficiency apparatus for recording plane wave holograms (FIG. 2 (a)) and measuring diffracted light (FIG. 2 (b)).

3 is a graph showing the absorption and associated refractive index spectra of typical dye molecules both before and after exposure to light. The dark area on the left represents the recording wavelength band and the dark area on the right represents the read wavelength band.

4 shows a holographic planar wave characterization system used to characterize the dye-doped polycarbonates of the present invention.

FIG. 5 is a planar wave holographic recording measurement graph of dye-doped polycarbonate prepared according to the present invention showing oscillating behavior of diffracted light in a medium.

FIG. 6 is a graph of each selectivity measurement at 0 ° for the 1.5 mm thick dye-doped polycarbonate of the present invention. FIG.

FIG. 7 is a measurement graph of 130 plane wave angle-diversified holograms in a 1.5 mm thick dye doped polycarbonate medium prepared according to the present invention showing M / # of 1.1 to 1.5.

FIG. 8 is a measurement graph of 150 plane wave angle-diversified holograms in a 1.5 mm thick dye doped polycarbonate medium prepared in accordance with the present invention showing an M / # of approximately 2. FIG.

The present invention provides an optical data storage medium for use in holographic data storage and retrieval. The holographic storage medium comprises a substrate and a dye material having narrowband optical properties selected and used on the basis of several important features, including: the ability to change the refractive index of the dye material upon exposure to light; Efficiency at which the light produces the change; And separation between the maximum absorption of the dye and the desired wavelength or wavelengths used for storing and / or reading data. The present invention relates to a method of locally changing the refractive index of the dye material in a graded manner rather than in separate steps (continuous sine wave change) and finally using the induced change as a diffractive optical element. to provide. Typically, the dye molecules used are photochemically active narrowband dyes. Narrowband dyes of photochemical activity can be described as dye molecules with light absorption resonance characterized by maximum absorption and a central wavelength associated with a spectral width of less than 500 nm (full width at half maximum, FWHM). In addition, the photochemically active narrowband dye molecules undergo a photo-induced chemical reaction upon exposure to light having a wavelength within the absorption range. Such reactions may be photodegradation reactions such as oxidation, reduction, or bond breakage to form smaller components, or molecular rearrangements such as sigma-directed rearrangements, or addition reactions such as ferriccyclic ring reactions. Can be.

Substrates used in the holographic storage media of the present invention may read data in the holographic storage material, including any material having sufficient optical properties, for example low scattering, low birefringence and negligible loss at the wavelength of interest. To be able. In general, any plastic material exhibiting these properties can be used as the substrate. However, the plastic material must be able to withstand processing parameters (eg, incorporation of dyes and the application of any coating or subsequent layers, and molding into final form) and subsequent storage conditions. Possible plastic materials include thermoplastics having a glass transition temperature of at least about 100 ° C, preferably at least about 150 ° C. In some embodiments, the plastic material, such as polyetherimide, polyimide, a combination comprising one or more of these and others has a glass transition temperature of greater than about 200 ° C.

Some possible examples of such plastic materials include, but are not limited to, amorphous and semicrystalline thermoplastics and blends such as polycarbonates, polyetherimides, polyvinyl chlorides, polyolefins (eg, but not limited to linear or cyclic polyolefins, For example polyethylene, chlorinated polyethylene, polypropylene, etc., polyesters, polyamides, polysulfones (e.g., but not limited to hydrogenated polysulfones, etc.), polyimides, polyether sulfones, ABS resins, polystyrenes (e.g. Non-limiting hydrogenated polystyrenes, syndiotactic and atactic polystyrenes, polycyclohexyl ethylene, styrene-co-acrylonitrile, styrene-co-maleic anhydride, etc.), polybutadiene, poly Acrylates such as, but not limited to, polymethylmethacrylate (PMMA), methyl methacrylate poly Copolymers), polyacrylonitrile, polyacetals, polyphenylene ethers (e.g., but not limited to those derived from 2,6-dimethylphenol and with 2,3,6-trimethylphenol) Copolymers, etc.), ethylene-vinyl acetate copolymers, polyvinyl acetate, ethylene-tetrafluoroethylene copolymers, aromatic polyesters, polyvinyl fluorides, polyvinylidene fluorides, and polyvinylidene chlorides.

In some embodiments, the plastic material used as the substrate in the present invention is made of polycarbonate. The polycarbonate may be an aromatic polycarbonate, an aliphatic polycarbonate, or a polycarbonate including both aromatic and aliphatic structural units. As used herein, the terms "polycarbonate", "polycarbonate composition", and "composition comprising aromatic carbonate chain units" include compositions having structural units of formula (I):

Where

Preferably, R ¹ is an aromatic organic radical, more preferably a radical of formula II:

-A ¹ -Y ¹ -A ^2-

Where

A ¹ and A ² are each monocyclic divalent aryl radicals,

Y ¹ is a bridging radical having 0, 1 or 2 atoms separating A ¹ and A ² .

In a typical embodiment, one atom separates A ¹ and A ² . Exemplary non-limiting examples of radicals of this type are -O-, -S-, -S (O)-, -S (O) _2- , -C (O)-, methylene, cyclohexyl-methylene, 2- Ethylidene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, adamantylidene and the like. In another embodiment, 0 atoms separate A ¹ and A ² , an illustrative example being biphenol (OH-benzene-benzene-OH). The crosslinking radical Y ¹ may be a hydrocarbon group or a saturated hydrocarbon group, for example methylene, cyclohexylidene or isopropylidene or an aryl crosslinking group.

Polycarbonates can be produced by the reaction of dihydroxy compounds in which only one atom separates A ¹ from A ² . The term "dihydroxy compound" as used herein includes, for example, bisphenol compounds having the formula III:

Where

R ^a and R ^b each independently represent a halogen atom or a monovalent hydrocarbon group;

p and q are each independently integers of 0 to 4;

X ^a represents one of the groups of formula IV:

Where

R ^c and R ^d each independently represent a hydrogen atom or a monovalent linear or cyclic hydrocarbon group,

R ^e is a divalent hydrocarbon group.

Some illustrative non-limiting examples of suitable dihydroxy compounds include dihydric phenols and dihydroxy-substituted aromatic hydrocarbons, such as those disclosed by the name or formula (general or specific) in US Pat. No. 4,217,438. do. A non-limiting list of specific examples of bisphenol compounds of the type that may be represented by Formula III is as follows: 1,1-bis (4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) ethane; 2,2-bis (4-hydroxyphenyl) propane (hereinafter "bisphenol A" or "BPA"); 2,2-bis (4-hydroxyphenyl) butane; 2,2-bis (4-hydroxyphenyl) octane; 1,1-bis (4-hydroxyphenyl) propane; 1,1-bis (4-hydroxyphenyl) n-butane; Bis (4-hydroxyphenyl) phenylmethane; 2,2-bis (4-hydroxy-3-methylphenyl) propane (hereinafter "DMBPA"); 1,1-bis (4-hydroxy-t-butylphenyl) propane; Bis (hydroxyaryl) alkanes such as 2,2-bis (4-hydroxy-3-bromophenyl) propane; 1,1-bis (4-hydroxyphenyl) cyclopentane; 9,9'-bis (4-hydroxyphenyl) fluorene; 9,9'-bis (4-hydroxy-3-methylphenyl) fluorene; 4,4'-biphenol; And bis (hydroxyaryl) cycloalkanes such as 1,1-bis (4-hydroxyphenyl) cyclohexane and 1,1-bis (4-hydroxy-3-methylphenyl) cyclohexane (hereinafter referred to as "DMBPC "Or" BCC ") and the like as well as combinations comprising at least one of the above bisphenol compounds.

In another embodiment, X ^a in Formula III may be ^a C ₆ -C ₂₀ aromatic radical. In some embodiments, the aromatic radical can be substituted with groups including, but not limited to, alkyl, aryl, esters, ketones, halides, ethers, and combinations thereof.

Polycarbonates or dihydric phenols and glycols, hydroxy- or acid-terminated polyesters, dibasic acids, hydroxy acids, or polycarbonates resulting from the polymerization of two or more different dihydric phenols, if desired, rather than homopolymers, are desired. It is also possible to use copolymers with aliphatic diacids. In general, useful aliphatic diacids have from about 2 to about 40 carbons. Preferred aliphatic diacids are dodecanedioic acid. Polyarylate and polyester-carbonate resins or blends thereof may also be used.

In addition to branched polycarbonates, blends of linear polycarbonates with branched polycarbonates are also useful. The branched polycarbonate can be prepared by adding a branching agent during the polymerization. Such branching agents are well known and may include polyfunctional organic compounds containing at least three functional groups, which may be hydroxyl, carboxyl, carboxylic anhydride, haloform, and mixtures comprising one or more of the branching agents. . Specific examples include trimellitic acid, trimellitic anhydride, trimellitic acid trichloride, tris-p-hydroxy phenyl ethane, isatin-bisphenol, (1,3,5-tris ((p-hydroxyphenyl) isopropyl) ) Benzene), (4 (4 (1,1-bis (p-hydroxyphenyl) ethyl) α, α (dimethyl benzyl) phenol), 4-chloroformyl phthalic anhydride, trimesic acid, benzophenone tetracarboxylic acid, etc. As well as combinations comprising at least one of the branching agents, The branching agent can be added at a level of from about 0.05 to about 2.0 weight percent based on the total weight of the substrate. Examples of methods for preparing are disclosed in US Pat. Nos. 3,635,895 and 4,001,184. All types of polycarbonate end groups are contemplated herein.

Preferred polycarbonates are based on bisphenol A, wherein A ¹ and A ² are each p-phenylene and Y ¹ is isopropylidene. Preferably, the weight average molecular weight of the polycarbonate is from about 5,000 to about 100,000 atomic mass units, more preferably from about 10,000 to about 65,000 atomic mass units and most preferably from about 15,000 to about 35,000 atomic mass units.

As indicated above, the polycarbonate material has a dye material. The polycarbonate composition may also include various additives conventionally incorporated in this type of resin composition. Such additives include, for example, heat stabilizers; Antioxidants; Light stabilizers; Plasticizers; Antistatic agents; Mold release agents; Additional resins; Blowing agents and the like, as well as combinations of the above additives.

One example of a suitable polycarbonate is Lexan®, commercially available from General Electric Company.

In other embodiments, polyetherimide can be used as the substrate. Such materials are known in the art and include, for example, Ultem®, an amorphous thermoplastic polyetherimide commercially available from General Electric Company.

The data storage medium may be prepared by first preparing the base material using conventional reaction vessels, such as single or twin screw extruders, kneaders, blenders, etc., which may suitably mix various precursors.

The extruder must be maintained at a temperature high enough to melt the substrate material precursor without its decomposition. In the case of polycarbonates, for example a temperature of about 220 to about 360 ° C, preferably about 260 to about 320 ° C may be used. Similarly, the residence time in the extruder should be adjusted to minimize degradation. A residence time of about 2 minutes or less, preferably about 1.5 minutes or less, particularly preferably about 1 minute or less can be used. Prior to extrusion into the desired form (typically pellets, sheets, webs, etc.), the mixture may be optionally filtered, for example by use of melt filtration and / or screen packs to remove undesirable contaminants or degradation products. have.

Once the composition of plastic material has been prepared, it can be molded into the substrate using a variety of molding and / or processing techniques. Possible techniques include injection molding, film casting, extrusion, compression molding, blow molding, stamping, and the like. Typically the substrate has a thickness of approximately 100 microns to several centimeters, depending on the desired optical properties.

As indicated above, the holographic storage medium of the present invention has a material that acts as a data storage material, interspersed entirely. Preferably, the data storage material is a dye having narrowband optical properties, ie narrowband absorption resonance. The dye also undergoes light-induced reactions that significantly alter its absorption properties. Thus, the dye materials used in accordance with the present invention allow for an increased refractive index change due to the refractive index dispersion associated with the light-induced change in the narrowband absorption resonance.

The photochemically active narrowband dye material used in the present invention is preferably an organic dye, which undergoes irreversible chemical change upon exposure to the "recording" wavelength of specific light that eliminates the absorption bands exhibited by the narrowband dye. . Photolysis products or photolysis products resulting from the interaction of the photochemically active narrowband dye with light having a “recording” wavelength typically exhibit an absorption spectrum (spectrums) that is entirely different from that represented by the dye prior to irradiation. . Irreversible chemical change in the dye produced by the interaction with the recording wavelength light results in a change corresponding to the molecular structure of the dye, resulting in a "photolysate", which is a cleavage type photolysate or rearrangement type. It may be a photolysis product. Modifications to this dye molecular structure and simultaneous changes in the light absorption properties of the photolysate (s) to the starting narrowband dye result in significant changes in the refractive index in the substrate that can be observed at separate “read” wavelengths. . Narrow-band dye materials used according to the invention also tend to have strong optical properties due to the preservation of the oscillator strength, i.e., since the absorption is concentrated in a narrow spectral region, the magnitude of the absorption is determined by the area under the curve ( Stronger as the oscillator strength is preserved.

As indicated above, the present invention uses narrowband dye materials that undergo photo-induced changes, including photolysis (eg, oxidation or bleaching) or photo-induced molecular rearrangements. The narrowband material has the ability to support a first order response to light intensity, as opposed to an on / off response. In the case of photolysis, the material contributing to the narrowband absorption decomposes in the presence of light. As a result, the strong absorption resonance of the material disappears like the associated refractive index dispersion. The result is a permanent light-induced change. In the case of molecular rearrangement, the results are almost the same but the molecules are rearranged instead of degraded to shift the absorption to longer or shorter wavelengths. Because these processes use dye materials with strong narrow band absorption, they are strongly associated with refractive index changes that change simultaneously with the absorption.

In another embodiment, the narrowband material may undergo a light-induced change, for example physical transport, wherein the dye material is bound to another molecule to undergo spatial diffusion in the presence of light. In such cases, higher concentrations of the narrowband material may be collected in areas of greater light intensity.

The dye material may be used for the substrate as described above, for example polycarbonate or polyetherimide. The narrowband material undergoes large refractive index changes. Such narrowband materials can support wavelength varying optical data storage for increased data density.

The narrowband dye material used in the present invention is suitable for use in a guest-host system in which the narrowband dye material is a guest and the substrate is a host. In some embodiments, the narrowband dye material is dissolved with a polymer host in a solvent to prepare a solution. Films can be formed from the solution by spin coating. In other embodiments, the film can be formed by blade coating, substrate dipping and spraying. Suitable polymeric base materials containing narrowband dye materials are referred to as "doped polymers". Such doped polymers can be prepared by various techniques, such as the solvent casting techniques mentioned above. In one embodiment, the doped polymer is also dissolved in the narrowband dye material in a liquid monomer and thereafter the monomer is polymerized thermally or by photoreaction in the presence of the dye to narrow the photochemically active narrowband dye. Can be prepared by producing an optically transparent base material in which is uniformly dispersed.

In another embodiment, the narrowband dye material of the present invention may be chemically bonded to the polymeric support. Binding of the dye to the polymer support can be accomplished by including reactive substituents on the dye molecules involved in the polymerization reaction. Suitable substituents include simple alcohols, amines, carboxylates and other reactive functional groups such as chloroformate. The product polymer includes dyes added to the polymer. The dye can be attached to the main chain of the polymer chain or to the polymer chain as a chain stopper. Examples of suitable polymers are bisphenol A polycarbonates, polyetherimides, acrylate polymers such as PMMA, polysulfones, polyamides and the like. If used, films and disks can be made using the methods described above for guest-host systems.

Preferably, the dye material scattered throughout the substrate comprises an organic dye having two or more aromatic rings bonded by crosslinked double bonds. Such materials are known to those skilled in the art and include stilbenes, stilbene derivatives (extended stilbenes), azo, and other dye molecules such as organic nonlinear optical (NLO) materials. Surprisingly, it has been found that the dye molecules of the invention having at least one nitro group in the ortho position relative to the crosslinked double bonds joining the two or more aromatic rings are particularly well suited as photo-modifying dye materials. The aromatic ring of the dye material having the o-nitro group may also contain other electron recovery groups, typically cyano or additional nitro groups.

Further, other aromatic rings of the dye material are preferably electron donating groups, for example primary, secondary, or tertiary amines, preferably tertiary amines; Aryloxy groups; Alkoxy groups; Hydroxyl groups; Or inorganic or organic phenoxide salts. In some embodiments, multiple electron donating substituents, such as combinations of the above groups, may also be present on the ring.

Aldehydes and ketones also act as electron acceptors and simple alkyl groups can act as donors, but these groups are generally less effective and can be on either ring without presumably significant change. Other sulfur and nitrogen compounds may be included as acceptors or as donors, depending on the structure of the substituents and whether the groups have a net or recovery effect.

Preferably, the organic dyes used according to the invention are nitrostilbene or nitrostilbene derivatives. As indicated above, one of the aromatic rings of the nitrostilbene dye molecule has an ortho nitro group to the crosslinked double bond. Suitable nitrostilbene derivatives include 4-dimethylamino-2 ', 4'-dynitrostilbene, 4-dimethylamino-4'-cyano-2'-nitrostilbene, 4-hydroxy -2 ', 4'-dynitrostilbene and 4-methoxy-2', 4'-dynitrostilbene. These dyes were synthesized and optically induced rearrangements of such dyes were studied in relation to their chemistry of reactants and products, as well as their activation energies and entropy factors (JS Splitter and M. Calvin, "The Photochemical Behavior of Some o"). -Nitrostilbenes ", J. Org. Chem., Vol. 20, pg. 1086 (1955). More recent studies have focused on recording waveguides in polymers doped with the dye using refractive index modulation resulting from these optically induced changes (McCulloch, IA, "Novel Photoactive Nonlinear Optical Polymers for Use in Optical Waveguides"). ", Macromolecules, vol. 27, pg. 1697 (1994)).

Additional functional groups which may be substituted on the nitrostilbene derivatives include alkyl groups having 1 to 6 carbon atoms, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl and the like; Particularly preferred are those having 1 to 4 carbon atoms, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl and the like. Alkoxy groups, aryl groups and aralkyl groups can also be substituted on said nitrostilbenes for use according to the invention.

When used, the alkyl group is a hydroxyalkyl group, alkoxyalkyl group, alkylaminoalkyl group, dialkylaminoalkyl group, alkoxycarbonylalkyl group, carboxyalkyl group, halogenated alkyl group, alkanoyloxyalkyl group, aminoalkyl And the like.

In some embodiments, the alkyl group preferably has conjugated substituents such as electron donating groups such as alkoxy groups, alkylamino groups, dialkylamino groups, amino groups and the like.

Examples of such hydroxyalkyl groups include those having 1 to 6 carbon atoms in the alkyl moiety, for example hydroxymethyl, 2-hydroxyethyl, 1,1-dimethyl-2-hydroxyethyl, 3-hydroxypropyl , 4-hydroxybutyl, 2-hydroxybutyl, 1-hydroxypentyl, 6-hydroxyhexyl and the like.

Examples of alkoxyalkyl groups include those having 1 to 6 carbon atoms in both the alkyl moiety and the alkoxy moiety, for example methoxymethyl, methoxyethyl, methoxybutyl, ethoxyhexyl, ethoxymethyl, butoxyethyl, t- Butoxyhexyl, hexyloxymethyl, and the like.

Examples of alkylaminoalkyl groups include those having 1 to 6 carbon atoms in the alkyl moiety, for example methylaminomethyl, ethylaminomethyl, hexylaminomethyl, ethylaminoethyl, hexylaminoethyl, methylaminopropyl, butylaminopropyl, methyl Aminobutyl, ethylaminobutyl, hexylaminobutyl, methylaminohexyl, ethylaminohexyl, butylaminohexyl, hexylaminohexyl and the like. Substituted alkylamino groups, such as hydroxyethylamino, are included within the meaning of "alkylamino" as defined herein. Moreover, the hydroxyethylamino group can act as a useful substituent on the narrowband dye when the narrowband dye must be chemically bound to a polymer comprising an optically transparent substrate as in the case of polymer-linked dyes. have.

Examples of dialkylaminoalkyl groups include those having 1 to 6 carbon atoms in the alkyl moiety, for example dimethylaminomethyl, diethylaminomethyl, dihexylaminomethyl, diethylaminoethyl, dihexylaminoethyl, dimethylamino Propyl, dibutylaminopropyl, dimethylaminobutyl, diethylaminobutyl, dihexylaminobutyl, dimethylaminohexyl, diethylaminohexyl, dibutylaminohexyl, dihexylaminohexyl and the like.

Examples of alkoxycarbonylalkyl groups include those having 1 to 6 carbon atoms in both the alkyl moiety and the alkoxy moiety, for example methoxycarbonylmethyl, methoxycarbonylethyl, methoxycarbonylhexyl, ethoxycarbonylmethyl, Ethoxycarbonylethyl, propoxycarbonylmethyl, isopropoxycarbonylmethyl, butoxycarbonylmethyl, pentyloxycarbonylmethyl, hexylcarbonylmethyl, hexylcarbonylbutyl, hexylcarbylhexyl and the like.

Examples of carboxyalkyl groups include those having 1 to 6 carbon atoms in the alkyl moiety, for example carboxymethyl, carboxyethyl, carboxybutyl, carboxyhexyl, 1-methyl-2-carboxyethyl and the like.

Examples of halogenated alkyl groups include alkyl groups having 1 to 6 carbon atoms substituted with one to three halogen atoms, for example monochloromethyl, monobromomethyl, monoiodomethyl, monofluoromethyl, dichloromethyl, dives Lomomethyl, diiodomethyl, difluoromethyl, trichloromethyl, tribromomethyl, triiodomethyl, trifluoromethyl, monochloroethyl, monobromoethyl, monoiodoethyl, monofluoroethyl, dives Lomobutyl, diiodobutyl, difluorobutyl, chlorohexyl, bromohexyl, iodohexyl and fluorohexyl. Suitable halogenated alkyl groups also include aryl halides.

Examples of alkanoyloxyalkyl groups include alkanoyloxy groups having 2 to 6 carbon atoms in the alkanoyl moiety and 1 to 6 carbon atoms in the alkyl moiety such as acetoxymethyl, 2- acetoxyethyl, propionyloxymethyl, 1-hexanoyloxy-2-methylpentyl and the like.

Examples of alkoxy groups include those having 1 to 6 carbon atoms, for example methoxy, ethoxy, propoxy, isopropoxy, butoxy, t-butoxy, pentyloxy, hexyloxy and the like. Moreover, such alkoxy groups are optionally substituted by halogen atoms, amino groups, hydroxyl groups, carboxyl groups, alkanoyloxy groups and the like as mentioned above as substituents on alkyl groups.

Examples of aryl groups include groups such as phenyl, naphthyl, anthryl, phenanthryl and the like.

Examples of arylalkyl groups include those having 1 to 6 carbon atoms in the alkyl moiety, for example benzyl 1-phenylethyl, 3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl, 6-phenylhexyl and the like.

The aryl group and aralkyl group optionally have substituents in addition to the aforementioned alkyl groups of 1 to 6 carbon atoms and alkoxy groups of 1 to 6 carbon atoms, and examples thereof include halogen atoms, amino groups, hydroxyl groups, and carboxyl groups which are optionally esterified. And cyano groups. Moreover, it is not necessary to specify the substitution position of these substituents.

The size and shape of the holographic storage media of the present invention may vary and may be annular, oval, rectangular or rectangular in shape. Most preferably the holographic storage medium is in the form of an annular disk. The thickness of the holographic storage medium may vary from 50 microns to about 5 cm, more preferably from about 0.25 to about 3 mm, most preferably from about 1 to about 2 mm.

Once formed, processes known to those skilled in the art can be applied to the holographic storage medium of the present invention for holographic data storage. Holographic data storage is one of a number of techniques that seek to maximize data density using the maximum volume of storage material (as opposed to surface storage as used in CD and DVD style systems). In the holographic storage method, the data is used to generate an optical interference pattern, which is subsequently stored in the holographic storage medium of the present invention.

An example of a holographic data storage method suitable for the production of the holographic storage medium of the present invention is shown in FIG. 1A. In this configuration, the output from laser 10 (532 nm) is divided by two split light beams by beam splitter 20. One ray, ie signal ray 40, is on some form of spatial light modulator (SLM) or deformable mirror device (DMD) 30 (which causes data to be stored on the signal ray 40). Incident. The device consists of a plurality of pixels that can block or transmit light based on an input electrical signal. Each pixel may represent a bit or part of a bit of data being stored (a single bit may consume more than one pixel of the SLM or DMD). The output of the SLM or DMD 30 is then incident on the storage material 60. The second light beam, ie the reference light beam 50, is transmitted to the storage material 60 by the reflecting mirror 70 with minimal deformation throughout the way. The two rays of light are incident together at different angles in the same area of the storage material 60. The net result is that the two rays produce an interference pattern at their intersection among the materials. The interference pattern is a unique function of the data imparted to the signal beam 40 by the SLM or DMD 30. The dye material in the holographic storage medium undergoes chemical change to change the refractive index of the area exposed to the laser light, and the resulting interference pattern is “fixed” into the holographic storage medium to give the storage material 60 Effectively produce a diffraction grating.

For reading data, as shown in FIG. 1B, a diffraction grating or pattern generated in the storage material 60 is blocked with a shutter 80 in the absence of the single light beam to simply expose it to the reference light beam 50. The data is reconstructed in the generated signal beam 90 again.

To test the properties of the material, diffraction efficiency measurements can be used. A system suitable for this measurement is shown in Figure 2a. Such devices are very similar to holographic storage devices; There is a second mirror 100 in place of the SLM or DMD. The laser 10 (532 nm) is split into two rays 110 and 120, where they interfere in the storage medium 60 to produce a plane wave diffraction grating. Then, as shown in FIG. 2B, one of the rays is either turned off or blocked with a shutter 80 and the amount of light diffracted by the diffraction grating in the storage material 60 is measured. The diffraction efficiency is measured as the amount of diffracted light ray 130 versus the total force incident on the storage material. More accurate measurements may also take into account the loss of the material due to reflection at the surface and absorption in the volume.

On the one hand, holographic plane wave characterization systems, in particular diversified holograms, can be used to test the properties of the material. Such a system can provide M / # for a given sample, which characterizes the final dynamic range or information storage capability of the sample as measured by the maximum number and efficiency of the diversified holograms stored in the material. The measurement standard used. A system suitable for this measurement is shown in FIG. 4. In this device, the output from the laser 10 (Coherent, Inc. DPSS 532) is passed through the shutter 140 for read / write adjustment and then half-wave for force adjustment. Pass through the combination of plate 150 and polarized light-splitter 160. The light is then passed through a two-lens telescope 170 (arrow with two ends in front) to adjust the size of the beam, reflect it to mirror 180, and then reflect it to mirror 190 to measure the beam. Transport into the area. The light is then passed through a second half-wave plate 200 and a second polarization beam splitter 210 to split the beam into two to adjust the force of each of the two beams. Subsequently, the light beam reflected from the light splitter is passed through the second shutter 220, and the shutter may independently turn on / off the force of the first light beam. The first light beam is then reflected from the mirror 230 and is incident on the sample 60 loaded on the rotating end 240. Light from the first light beam that has passed through the sample collects in the detector 250. The second light beam passes through the third half wave plate 260 to rotate its polarization in the same direction as the first light beam and then passes through the shutter 225 to provide on / off control of the second light beam. The second light beam is then reflected from the mirror 235 and incident on the sample. To measure the dynamic change of the in-situ system during exposure of the sample, a second laser 270 is passed through a two-lens telescope 175, reflected from a mirror 185 and a mirror 195 and then the first and Simultaneously enter the sample at the same position as the second light ray. The diffracted light is then collected at the detector 255.

Preferably, the holographic storage medium of the present invention records data to the holographic storage medium using light of one wavelength from a laser while using the light of different wavelengths to store data from the holographic storage medium. Use with the method of reading. In the holographic storage medium of the present invention, the refractive index change is produced by using a laser wavelength that is strongly absorbed by the dye. This absorption of light induces a photochemical reaction, which irreversibly converts the dye molecule from one compound to a second compound or combination of compounds. The product of the reaction does not have strong absorption at the laser wavelength characterizing the initial dye. However, since the interference pattern consists of bright and dark areas, some of the dye is not exposed and needs to remain unexposed to maintain successful operation. The read wavelength is chosen such that the wavelength is in the spectral region outside the strong absorption region, although there is a refractive index change.

Due to the correlation between the absorption resonance and the refractive index, the removal of the absorption resonance also has a dramatic effect on the refractive index with respect to nearby wavelengths. This relationship is shown graphically in FIG. 3, which was estimated based on an approved theoretical model (eg, “Lasers”, PW Milonni and JH Eberly, New York, NY: John Wiley & Sons, Inc., 1988] and the Karmers-Kronig relationship by Quantum Electronics 3rd ed., A. Yariv, New York, NY: Wiley Text Books, Inc., 1989. The spectral regions where there is a refractive index change but outside the strong absorption region are also shown in Figure 3. Details of the read / write process for two-color holography are included in the examples below.

In the production of holographic storage media of the invention, it is possible to select the wavelength of the light and the dye material which produces the desired absorption at the wavelength of light used. In some embodiments, the recording wavelength band can be any portion of the spectrum where more than 10% of incident light is absorbed. However, too strong absorption can cause non-linearity in the storage of data, resulting in poor reconstruction of the stored information. It is also possible to reduce the absorption by lowering the concentration of the dye material in the substrate, but this has the disadvantage of reducing the maximum achievable refractive index change and subsequently reducing the efficiency of the material in data storage. Moreover, too little absorption lacks sensitivity and the material requires long exposure times for the storage of data.

Another way to improve data storage efficiency is to modify the system so that the wavelength for recording does not match the maximum absorption of the dye material. This can add substantially more dye to the holographic storage medium, but still maintains a controllable absorption coefficient such that the data is stored correctly. The exact amount can be measured as a function of the maximum absorption of the dye. For example, if the peak absorption is only transmitting 1% of the light at the same wavelength, the recording wavelength may be selected away from the peak such that the material transmits about 25 to about 75% of the incident light. In some cases, the transmission can range from about 40% to about 60%, and in some other embodiments there is about 50% transmission.

As will be appreciated by those skilled in the art, different molecules will have broadly different absorption profiles (wider, narrower, etc.). Thus, the wavelength used to record and read the holographic storage medium of the present invention will vary depending on the light source, substrate and dye material. Suitable wavelengths for recording data to holographic storage media can vary depending on both the substrate and dye material used, and can range from about 375 to about 550 nm, preferably from about 400 to about 500 nm.

The read wavelength is preferably differentiated from the write wavelength such that there is very little or no absorption of the read light at the wavelength selected for reading the information contained in the holographic storage medium. Preferably the wavelength of light used for reading is selected so that the difference between the reading wavelength and the absorption band associated with the recording event is maximized. In one embodiment, the read light has a wavelength shifted from about 50 nm to about 400 nm from the wavelength of the signal light. In some embodiments, a suitable readout light has a wavelength of about 400 to about 800 nm. However, the further away from the absorption band, the smaller the refractive index change is, which negatively affects the efficiency of the storage process. Also, the greater the separation between the write and read wavelengths, the more difficult it is to reconstruct the data. Therefore, the read wavelength is most preferably selected as the closest wavelength with a transmittance greater than 95%.

In some embodiments, blue light in wavelengths ranging from about 375 to about 425 nm can be used for recording and green / red light in wavelengths ranging from about 500 to about 800 nm can be used for reading. In other embodiments, the wavelength of light used for recording can range from about 425 to about 550 nm, and the read wavelength can range from about 600 to about 700 nm. In one embodiment, light at 532 nm wavelength can be used for recording and light at 633 nm or 650 nm wavelength can be used for reading.

The holographic storage media of the present invention can support a number of diversified holograms, which in some cases can be driven by the total refractive index contrast between the substrate with the dye material and the substrate lacking the dye material. In turn, the overall refractive index contrast may be higher in the dye-doped materials of the present invention in some embodiments. In other embodiments, the storage materials of the present invention can be used in a solid form.

The invention is illustrated by the following non-limiting examples.

Test samples comprising photochemically active narrowband dyes and transparent substrates prepared and tested in Examples 1 to 3 below are based on polycarbonate hosts, and various amounts of known dyes are dissolved in the polycarbonate. The polycarbonate substrate is referred to as "host" for convenience and the dissolved dye is referred to as "guest dopant". In the present invention, the test sample used a stilbene derivative prepared using a known synthetic method as a guest dopant.

All of the films disclosed in the examples below were made from glass tubing (2 inches in diameter, 2 inches in length) in which the dye material and substrate, i.e. polycarbonate, was dissolved in methylene chloride as about 5% by weight solids and the solution was placed on a piece of flat glass. It was poured into a cut cylinder and manufactured. A sheet of filter paper was placed on top to prevent the particles from falling off as the solvent evaporated. After approximately 4 hours, the film was removed from the glass plate, sandwiched between metal rings and placed in a vacuum oven at 50 ° C. for at least 16 hours. The film was removed from the glass and placed between metal rings to allow it to dry evenly under vacuum. A test was then conducted to determine its diffraction efficiency on the film. Table 1 below shows the amount of polycarbonate and solvent needed to produce the specific film thicknesses shown in the examples.

Example 1

This example was based on polycarbonate doped with 4-dimethylamino-2 ', 4'-dynitrostilbene. The chemical formula of the dye is shown below:

4-Dimethylamino-2 ', 4'-dynitrostilbene was added to a polycarbonate substrate (commercially available as Lexan® from General Electric Company) according to the procedure outlined above. A film was prepared. The resulting film had various concentrations of 4-dimethylamino-2 ', 4'-dynitrostilbene and various thicknesses as shown in Table 2 below. The film was exposed to light at 532 nm wavelength using a coherent incorporated DPSS 532 laser to record data to the medium. Diffraction efficiency was measured using a device similar to the device shown in FIG. 2. The table below shows the results obtained by diffraction efficiency measurements.

Example 2

Based on the results of Example 1, a second series of samples were prepared using different dyes. The selected dye was envisioned such that the absorption peak shifted to a shorter wavelength to lower the net absorption observed at that recording wavelength. This was done so that larger changes in the net refractive index could be obtained using higher concentrations of the dye. To achieve this blue shift, cyano group is used in place of one of the nitro groups of 4-dimethylamino-2 ', 4'-dynitrostilbene to give 4-dimethylamino-4'-cyano- 2'-nitrostilbene was formed and its structure is shown below:

4-Dimethylamino-4'-cyano-2'-nitrostilbene was added to Lexan® according to the procedure outlined above to prepare a number of films. The resulting film had various concentrations of 4-dimethylamino-4'-cyano-2'-nitrostilbene and various thicknesses as shown in Table 3 below. The film was exposed to light at 532 nm wavelength using a coherent incorporated DPSS 532 laser to record data to the medium. Diffraction efficiency was measured using a device similar to the device shown in FIG. 2. The table below shows the results obtained by diffraction efficiency measurements.

In addition to diffraction efficiency measurements, sample 8 was used to store analog images. Analog images were stored in a 1.13 wt% 4-dimethylamino-4'-cyano-2'-nitrostilbene sample (Sample 8) using the digital holography device shown in FIG. The image was recorded using a 532 nm laser. The image was then read using a 650 nm diode laser to generate the analog image. The material has been used successfully for two-color holography (one color / wavelength is for writing and the other is for reading).

Example 3

A series of sample films was prepared to obtain improved concentrations of dye dissolved in polycarbonate. These samples used 4-hydroxy-2 ', 4'-dynitrostilbene as dye material, the structure of which is shown below:

Hydroxy dynitrostilbene was added to Lexan® according to the procedure outlined above to prepare a number of films. The resulting film had various concentrations of hydroxy dynitrostilbene as shown in Table 4 below. These films were exposed to light at 532 nm wavelength using a coherent incorporated DPSS 532 laser to record data to the medium. Diffraction efficiency was measured using a device similar to the device shown in FIG. 2. The table below shows the results obtained by diffraction efficiency measurements.

Example 4

Sample discs were prepared via compression molding of bisphenol A polycarbonate doped with 3.3 wt% and 6.6 wt% of the 4-hydroxy-2 ', 4'-dynitrostilbene dye mentioned in Example 3, respectively. The samples were compressed in a mold at about 255 ° C under a pressure of approximately 150 pounds. After heating and compacting the mixture of polycarbonate and dye for a period sufficient to melt, the mold was transferred to a cold press and held under a pressure of 4000 pounds until the mold temperature was reduced to about 50 ° C. The resulting disk was then recovered from the mold and had a diameter of about 1 inch and a thickness of about 1.5 to about 2 mm.

Example 5

A number of experiments were performed to evaluate the performance of the disks prepared in Example 4 for angular-differentiated holographic storage.

The absorption at 532 nm of the 1.5 mm thick dye doped polycarbonate sample prepared in Example 4 was measured using a coherent incorporated DPSS 532 laser. The absorption values measured for the disks with dye concentrations of 3.3 wt% and 6.6 wt% were about 40% and 60%, respectively.

A 1.5 mm thick sample disk with 6.6 wt% dye prepared according to Example 4 was placed in a planar wave holographic characterization system as shown in FIG. 4. The sample was rotated to obtain angular diversification. The hologram was recorded by 532 nm light and the hologram was read by 632 nm laser light for kinematic measurements or by one of two 532 nm laser light for diffraction efficiency measurements.

Kinetic measurements on hologram recording were performed using 100 mW of 532 nm light in each branch. The low sensitivity required the samples to be exposed for hundreds of seconds. The results are shown in FIG. The vibration pattern shown in FIG. 5 showed low maximum diffraction efficiency values of several percent. The vibration pattern had a period of tens of seconds.

A read measurement was then performed on the disk using a 532 nm wavelength to measure M / # instead of measuring the maximum diffraction efficiency. The read exposure was much shorter than the write exposure; Thus, each hologram could be recorded in tens of seconds, which limited the vibration problem.

The angular selectivity at 0 ° was estimated to be approximately 0.04 °, which was confirmed by measurement using the experimental setup shown in FIG. 4, and the results are shown in FIG. 6.

The experimental apparatus illustrated in FIG. 4 was then used for angle-diversity 130 and later 150, plane wave holograms (separated to 0.3 °) in the disc. Graphs of the results are shown in FIGS. 7 and 8.

The square root of the diffraction efficiencies of the holograms of FIG. 7 were added to give an M / # of 1.1. By correcting the angle-dependent reflection coefficient (samples not A / R coated) the M / # was increased to 1.5.

It can be seen that the vibration phenomenon observed during the kinematic measurements also influenced the results shown in FIGS. 7 and 8. Pairs of adjacent multiple holograms separated by only 0.3 ° had amplitudes that differ by a factor of five.

Subsequently, 358 digital angle-diversified holograms were recorded on dye doped polycarbonate samples of 6.6% by weight, 1.5 mm thick. Five kilobits per page were recorded. The measured Bit-Error-Rate was about 5 × 10 ⁻³ .

Example 6

Preparation of Bisphenol A (BPA) Polycarbonates Comprising 4-hydroxy-2 ', 4'-dynitrostilbene as Chain Stopper

BPA monomer (22.8 g, 100 mmol), 4-hydroxy-2 ', 4 in 500 ml 5-neck Morton flask equipped with reflux cooler, pH probe, dip tube for phosgene, thermometer and base addition tube '-Dynitrostilbene (1.15 g, 4 mmol), triethylamine (150 μl, 1 mmol), 90 mL methylene chloride and 90 mL water were charged. After adjusting the pH to 10.5 with 25% aqueous sodium hydroxide solution, phosgene was introduced at a rate of 0.5 g / min. The phosgene addition continued until the 20% excess was added (12 g, 120 mmol) while maintaining the pH at 10.5 with the base solution. At the end of the reaction, excess phosgene was sparged from the solution by a nitrogen stream. The brine layer was separated from the polymer containing organic layer and discarded. The organic layer was diluted with additional methylene chloride, washed twice with 1N HCl, washed three times with water and precipitated with methanol to form 23 g of a light yellow polymer. Gel permeation chromatography provided the following results: Mw-79,500, Mn-45,700 (based on polystyrene standard). NMR analysis confirmed the presence of 4'-hydroxy-2,4-dynitrostilbene as chain stopper.

As can be seen from the above examples, the material of the present invention has a very simple geometry, low shrinkage, high optical quality (by suitable processing) and is economical to production.

While the invention has been illustrated and described in exemplary embodiments, it is not intended to be limited to the details shown, and therefore, various modifications and substitutions can be made without departing from the spirit of the invention in any manner. Additional modifications and equivalents of the present invention can be made to those skilled in the art using routine experimentation as such, and all such modifications and equivalents are within the scope and spirit of the invention as defined by the following claims. It is believed to be present.

Claims (10)

Optically transparent substrates; Photochemically active narrowband dye materials capable of undergoing light-induced changes embedded in the optically transparent substrate; And One or more photolysis products of the dye, patterned in the substrate to provide one or more optically readable data included in the holographic storage medium, The photochemically active narrowband dye material comprises an organic dye having at least two aromatic rings bonded by crosslinked double bonds, wherein at least one knight is ortho to one of the at least two aromatic rings to the crosslinked double bond With a flag, The optically transparent substrate is polycarbonate, polyetherimide, polyvinyl chloride, polyolefin, polyester, polyamide, polysulfone, polyimide, polyether sulfone, polyphenylene sulfide, polyether ketone, polyether ether ketone, ABS resin , Polystyrene, polybutadiene, polyacrylate, polyacrylonitrile, polyacetal, polyphenylene ether, ethylene-vinyl acetate copolymer, polyvinyl acetate, liquid crystal polymer, ethylene-tetrafluoroethylene copolymer, aromatic Selected from the group consisting of polyester, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene chloride and tetrafluoroethylene, Holographic storage medium 60. delete delete The method of claim 1, The photochemically active narrowband dye material is 4-dimethylamino-2 ', 4'-dynitrostilbene, 4-dimethylamino-4'-cyano-2'-nitrostilbene, 4- Holographic storage medium comprising substituted nitrostilbenes selected from the group consisting of hydroxy-2 ', 4'-dynitrostilbene and 4-methoxy-2', 4'-dynitrostilbene 60. As a method of manufacturing the holographic storage medium 60, Optically transparent substrates include polycarbonates, polyetherimides, polyvinyl chlorides, polyolefins, polyesters, polyamides, polysulfones, polyimides, polyether sulfones, polyphenylene sulfides, polyether ketones, polyether ether ketones, ABS resins, Polystyrene, polybutadiene, polyacrylate, polyacrylonitrile, polyacetal, polyphenylene ether, ethylene-vinyl acetate copolymer, polyvinyl acetate, liquid crystal polymer, ethylene-tetrafluoroethylene copolymer, aromatic poly Selected from the group consisting of esters, polyvinyl fluorides, polyvinylidene fluorides, polyvinylidene chlorides and tetrafluoroethylene; Can undergo light-induced changes, including organic dyes having at least two aromatic rings bonded by crosslinked double bonds, wherein one of the at least two aromatic rings has at least one nitro group ortho to the crosslinked double bond Selecting a photochemically active narrowband dye material; Embedding the photochemically active narrowband dye material in the optically transparent substrate to provide a doped substrate; Patterning the photolysis product of the dye in the doped substrate at a wavelength capable of performing the light-induced change of the dye to form a holographic storage medium (60). A method of storing data in the holographic storage medium 60 of claim 1, Simultaneously illuminating the storage medium with the signal light and the reference light with the data to store a hologram of data contained in the signal light in the optical storage medium; Wherein the photochemically active narrowband dye material undergoes a light-induced change upon exposure to the signal beam to form a hologram in the storage medium. delete An optical reading method of the holographic storage medium of claim 1, Simultaneously illuminating the signal and reference beams having the data on the holographic storage medium to store a hologram of data contained in the signal beam in the optical storage medium, wherein the dye material is exposed to the signal beam. Undergoing irreversible rearrangement to form a hologram in the storage medium; Illuminating the holographic storage medium with a read light ray having a wavelength shifted from a wavelength of the signal light ray from 50 to 400 nm; And Reading data contained in the diffracted light from the hologram. The method of claim 8, Illuminating the signal ray to the storage medium comprises the signal ray having a wavelength between 375 and 550 nm. The method of claim 9, Shining the read light onto the storage medium comprises the read light having a wavelength between 400 and 800 nm.

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