RU2168707C2 - Volume phase hologram and process of its generation - Google Patents

Abstract

FIELD: phase three-dimensional holograms. SUBSTANCE: hologram includes porous silica structure with system of mutually coupled microcavities or pores whose mean radius is less than length of waves of hologram recording and reading radiation, product of photolysis of light sensitive material linked to walls of individual microcavities and spatially distributed in accordance with recorded interference picture and solid clear polymer material filling microcavities and characterized by local changes of refractive index which are spatially modulated in correspondence with recorded interference picture. Products of photolysis are modifier of polymerization of composition to be polymerized which transmutes as result of polymerization to polymer material filling microcavities. EFFECT: realization of volume phase hologram characterized by raised values of diffraction efficiency, reduced losses due to scattering. 19 cl, 2 dwg, 1 tbl

Description

 The invention relates to holography, more specifically to phase three-dimensional holograms.

 Known phase holograms consisting of a polymer matrix with local modulation of the refractive index. They can be detected in layers of photopolymers or in films of bichromated gelatin [See: R.J. Collier, S.V. Burckhardt, L. H. Lin "Optical Holography", 1971, Academic press, New York and London]. They are usually made of organic materials with low mechanical properties and heat resistance and, thus, are not very reliable and are subject to aging. Moreover, thick layers of such photosensitive media are practically inaccessible, which limits the achievable level of spectral and angular selectivity of the recorded holograms.

Volumetric holograms consisting of a porous high-silica framework and photolysis products of organic or inorganic photosensitive substances are also known, and spatial modulation of the hologram refractive index is achieved by appropriate modulation of the structure of the porous framework or spatial modulation of the concentration of photolysis products of the photosensitive substrate (See: V. Sukhanov, Heteremplary media , In SPIE, 1989, V. 1238, p. 226-230. The International Unesco Seminar Three-Dimensional Holography Science, Culture, Education. Ed. Tung H. Jeorg, 1989, Kiev, USSR). The physical thickness of such holograms can reach 10 ³ microns. Moreover, they are characterized by high thermal stability and are virtually non-shrinking. However, such holograms have a porous structure, which leads to a high level of light scattering in the blue-green region of the spectrum. To avoid this, the free volume of the hologram must be impregnated with the filler by introducing immersion. But the closer the refractive index of the filler to the refractive index of the porous skeleton, the lower the diffraction efficiency of the hologram (See: SA Kuchinskii et al., "The principal of hologram formation in capillary composites", Laser Physics, 1993, V3, n 6, p. 1114-1123). Thus, it is impossible to achieve both a low level of light scattering and high values of diffraction efficiency.

 The technical result, the achievement of which the present invention is directed, is the implementation of a volumetric phase hologram characterized by significantly increased values of diffraction efficiency and, at the same time, reduced losses due to scattering. The main idea of the invention is that the porous skeleton is filled with a solid-phase polymer with a spatially modulated refractive index, and the period of said spatial modulation of the refractive index should be the same as the spatial distribution period of the refractive index of the volume phase hologram consisting of a porous skeleton, the pores of which contain a filler with a spatially uniform refractive index.

 The indicated technical result is achieved by the fact that into a volumetric phase hologram with an interference pattern recorded in the form of local changes in the refractive index, containing a porous transparent silica skeleton having a system of interconnected microcavities or pores, the average radius of which is less than the wavelengths of the radiation that records and reads the hologram, a product of photolysis of a photosensitive material, wherein said product is rigidly attached to the wall of microcavities and spatially distributed n, in accordance with the intensity of the detected interference pattern, a solid-phase transparent polymer material is added that fills the microcavities, the polymer material being characterized by a local change in the refractive index, the variations being spatially modulated in accordance with the recorded interference pattern, and the photolysis product is a polymerization modifier for a composition polymerizable in said polymer, zap lnyayuschy microcavity material.

 The specified technical result is also achieved by the fact that as the named polymeric material, a homo- or copolymer of polyol- (allyl carbonate) is used.

 The specified technical result is also achieved by the fact that diethylene glycol bis-allyl carbonate is used as the named polyol- (allyl carbonate).

 The specified technical result is also achieved by the fact that the polymer of at least one alkyl methacrylate is used as the named polymer material.

 The specified technical result is also achieved by the fact that as the named polymer material, a homo- or copolymer of at least one vinyl monomer is used.

 The indicated technical result is also achieved by the fact that a copolymer of polyol- (allyl carbonate) with at least one other copolymerizable monomer selected from the series consisting mainly of vinyl acetate and oligourethanes having terminal dimethyl acrylate is used as the named polymer material.

 The indicated technical result is also achieved by the fact that as the named polymer material a styrene copolymer with at least one other copolymerizable monomer selected from the group consisting mainly of methyl methacrylate, vinyl acetate and acrylonitrile is used.

 The specified technical result is also achieved by the fact that the named porous frame is made in the form of porous high-silica glass obtained by acid etching of two-phase glass.

 The specified technical result is also achieved by the fact that the named porous frame is made in the form of porous glass obtained by sol-gel technology.

 The specified technical result is also achieved by the fact that the named polymerization modifier includes transition metal ions.

 The specified technical result is also achieved by the fact that as the polymerization modifier is used the product of a photolysable organometallic compound.

The specified technical result is also achieved by the fact that the named organometallic compound is selected from the group comprising: Mn ₂ (CO) ₁₀ , Co ₂ (CO ₈ ), Cr (CO) ₆ , Mo (CO) ₆ and Ti (cyclopentadiene) Cl ₂ .

The specified technical result is also achieved by the fact that the named polymerization modifier is the photolysis product of Cr ^VI .

The specified technical result is also achieved by the fact that the named salt of Cr ^VI selected from the group consisting mainly of: (NH ₄ ) ₂ Cr ₂ O ₇ , Na ₂ Cr ₂ O ₇ and K ₂ Cr ₂ O ₇ .

 The specified technical result is also achieved by the fact that the named polymerization modifier is directly attached to the walls of the microcavities of the named framework.

 The specified technical result is also achieved by the fact that the said polymerization modifier is enclosed in a layer covering the walls of the microcavities of the said framework.

 The specified technical result is also achieved by the fact that the named shell is made in the form of a photoresistor.

The specified technical result is also achieved by the fact that the named photoresistor is made of gelatin and the named Cr ^III ions are polymerization modifier.

 The specified technical result is also achieved by the fact that the named photoresistor is made of polyvinyl alcohol.

 The specified technical result is also achieved by the fact that the named photoresistor is made of shellac.

 The specified technical result is also achieved in that the optical device containing the light source and at least one optical element is characterized in that the said at least one optical element is made in the form of a hologram according to any of the methods described above.

 The specified technical result is also achieved by the fact that in the method of manufacturing a hologram, in which a transparent porous silica framework is obtained having a system of interconnected microcavities or pores, the average radius of which is less than the wavelengths of the radiation recording and reading the hologram, cover the walls of these microcavities with a photosensitive material, the product whose photolysis is a polymerization modifier for at least one of the selected polymerizable compositions, register a holographic interference pattern in the said material so that the named photolysis products are distributed on the walls of the individual named microcavities in accordance with the named interference pattern, the non-photolysed photosensitive material is removed, the remaining free volume of the named microcavities of at least one of the selected polymerizable compositions is filled, the named composition is polymerized so as to obtain a volumetric phase hologram made of transparent th frame filled with a solid phase polymeric material with spatial modulated refractive index, wherein the refractive index modulation period of said polymer must be the same as the period of spatial distribution of said photolysis products.

 By the term “polymerization modifier” is meant any substance which, when the polymerizable composition is polymerized in its presence, causes the refractive index of the polymerized material to be different from the refractive index of the polymerized material obtained by polymerizing the polymerized composition in the absence of the polymerization modifier.

Other features and advantages of the present invention will be apparent from the following descriptions and drawings, in which:
- FIG. 1 is a schematic volumetric phase hologram in accordance with the present invention; and
- FIG. 2 shows the dependence of diffraction efficiency on the lattice strength of a transmission hologram, useful for explaining the present invention.

The hologram shown in FIG. 1 consists of a porous high-silica skeleton 1 containing a system of pores or microcavities with an average radius less than the wavelength of visible light, i.e. less than 0.4 microns. The walls of individual microcavities are covered with shells with a refractive index n _c containing the products of photolysis of the photosensitive material and located in the vicinity of the maxima or minima of the recorded interference pattern. The free volume of the cavities is filled with filler 3 with a spatially modulated refractive index. Moreover, the refractive index of the filler is equal to n _f in cavities without a shell and n _f + Δ in other microcavities.

It is easy to show that the difference between the effective refractive indices of the exposed (A) and unexposed (B) regions in the volume of the hologram is determined by the expression:
n _A - n _B = Ff (n _c -n _f ) + F (1-f) Δ, (1)
where F = relative pore volume;
f = relative volume of the shell in the pores.

Более того, путем внедрения в свободный объем пористой голограммы пространственно модулированного наполнителя можно получить усиление решетки даже по отношению к начальной "сухой" голограмме (т.е. без наполнителя), для которой n_c - n_f достигает своей максимальной величины. Очевидно из (1), что коэффициент усиления в этом случае определяется выражением:

Как следует из выражений (2) и (3) усиление голограммы может иметь место как при симфазной модуляции показателя преломления наполнителя с распределением показателя преломления голограммы без наполнителя, так и в случае, когда эти же параметры промодулированы противофазно. Необходимо только, чтобы эта модуляция имела тот же пространственный период, что и изменение показателя преломления в зарегистрированной интерференционной картине, и чтобы абсолютные величины |K|, |K′|, определяемые выражениями (2) и (3), были больше 1. Как известно, максимальная величина дифракционной эффективности η пропускающей голограммы достигается при определенной величине амплитуды модуляции голограммы, что соответствует силе решетки χ, равной χ₁, где

Очевидно, что увеличение χ в К раз практически означает уменьшение уровня экспозиции, необходимого для достижения η = 100% (в предположении линейного отклика светочувствительного вещества голограммы).The first term in expression (1) describes the modulation amplitude of a porous hologram with a uniform filler, turning to zero if n _f is equal to n _c . But if spatial modulation of the refractive index of the filler takes place, this amplitude is nonzero, even if n _f = n _c , and is equal to F (1 - f) Δ. The amplitude of the change in the refractive index in the case of a spatially modulated filler is K times greater than in the case of a homogeneous filler (Δ = 0) Moreover, K is defined as:

Moreover, by introducing a spatially modulated filler into the free volume of the porous hologram, one can obtain lattice gain even with respect to the initial “dry” hologram (ie, without filler), for which n _c - n _f reaches its maximum value. It is obvious from (1) that the gain in this case is determined by the expression:

As follows from expressions (2) and (3), hologram amplification can take place both in case of phase-wise modulation of the refractive index of the filler with the distribution of the refractive index of the hologram without filler, and in the case when the same parameters are modulated out of phase. It is only necessary that this modulation has the same spatial period as the change in the refractive index in the recorded interference pattern, and that the absolute values | K |, | K ′ | defined by expressions (2) and (3) are greater than 1. How it is known that the maximum diffraction efficiency η of the transmitting hologram is achieved at a certain magnitude of the modulation amplitude of the hologram, which corresponds to a lattice strength χ equal to χ ₁ , where

Obviously, an increase in χ by a factor of K practically means a decrease in the level of exposure necessary to achieve η = 100% (assuming a linear response of the photosensitive substance of the hologram).

 Thus, according to the present invention, it is possible to obtain a phase hologram with high efficiency at a low level of light scattering by spatial modulation of the refractive index of the filler.

 The practical implementation of the described transition for enhancing the hologram is based on the difference between the mechanisms of polymerization of the monomer filler in the exposed and unexposed portions of the hologram, when the photolysis products of the photosensitive material manifest themselves as a polymerization modifier of this process. As a result, the density of the polymer filler and, consequently, the refractive index are spatially modulated in accordance with the intensity distribution of the recorded interference pattern.

 As a porous silicate transparent frame, for example, glass made by leaching borosilicate glass can be used (See: VI Sukhanov. "Porous glass as a storage medium". Optica Applicata, 1994, v. 24, n. 1-2, pp 13-26), or, for example, porous glass obtained by the so-called sol-gel technology (See: VI Sukhanov et al. "Porous sol-gel glass as holographic recording medium". In: Book of Abstracts. The VIII international Workshop on Glasses and Ceramics from Gels. 1995, Faro, Portugal, September 18-22, p. 331).

 In both cases, the porous skeleton contains a system of interconnected microcavities or pores with a developed inner surface, having an average radius substantially shorter than the wavelength of the acting light (recording or reading). These circumstances, on the one hand, provide a relatively low level of light scattering, and on the other hand, make it possible to efficiently impregnate the frame with the said photosensitive material and, therefore, provide a good coating of the walls of these microcavities with the named material.

 As photosensitive materials for recording holograms in accordance with the invention, for example, photosensitive materials can be used which form products during photolysis that significantly affect complex free radical polymerization.

Illustrative examples of suitable photosensitive materials are some inorganic transition metal salts, such as carbonyl or cyclopentadiene transition metal complexes, for example (NH ₄ ) ₂ Cr ₂ O ₇ , Na ₂ Cr ₂ O ₇ , K ₂ Cr ₂ O ₇ , and some organometallic compounds transition metals, such as carbonyl or cyclopentadiene transition metal complexes, for example Mn ₂ (CO) ₁₀ , Cr (CO) ₆ , Co ₂ (CO) ₆ , Mo (CO) ₆ or Ti (cyclopentadiene) ₂ Cl ₂ . (See: NF Borelly and DL Morse. "Photosensitive impregnated porous glass". Appl. Phys. Lett. 1983, v. 43, n.pp. 992-993; "Photosensitive metal-organic systems: mechanistic principles and applications", Ed .Ch. Kutal, N. Serpone. Advances in Chemistry. Ser. 238, 1993, Am. Chem. Soc., Washington, DC 449 p.).

 The creation of shells on the pore walls can be carried out in a simple way - by bathing porous glass in a solution of photosensitive material, followed by drying from a solvent. If necessary, a vacuum can be used to force the impregnation of porous glass.

 It should be noted that the photolysis of transition metal salts has already been used to record holograms, in particular the photolysis of Cr (VI) salts: (See: G. Manivannan et al. "Primary photoprocesses of Cr (VI) in real-time holographic recording: dichromated poly (vinyl alkohol). J. Phys. Chem., 1993, v. 97, n. 28, pp. 7228-7233) wherein Cr (VI) ions are reduced to Cr (III) ions in the exposed areas of the hologram.

 When, at the recording stage of a hologram, transition metal compounds are photolized inside a porous silica framework, their photolysis products interact with functional groups, for example, -SiOH, which are inevitably present on the silicate surface of the walls of microcavities, which leads to the formation of shells of complex molecules chemically bonded to the walls of the porous framework. Alternatively, a shell containing transition metal ions and chemically bonded to the walls of the porous glass framework may also be formed using organometallic transition metal compounds, as described by N.F. Borelly et al. "Photochemical method to produce waveguiding in glass." IEEE J. Of Quantum Electronics. 1986, v. QE-22, n. 6, pp. 896-901.

 Instead of the direct chemical attachment of transition metal ions to the pore walls of porous glass, it is also possible to form shells on the walls of these pores using a photoresist layer containing transition metal compounds. Synthetic polymers, in particular polyvinyl alcohol, can be used as photoresists (See: G. Manivanna et al. "Primary photoprocesses of Cr (VI) in real-time holographic recording: dichromated poly (vinyl alcohol). J.Phys.Chem ., 1993, v.97, n. 28, pp. 7228-7233), or natural polymers, in particular gelatin or shellac.

 Registration of the hologram is carried out according to the usual method using laser radiation of the visible region of the spectrum. It is only necessary that the exposure value is sufficient to generate such a number of photolysis products that could subsequently effectively act as a polymerization modifier in step (e) and lead to a difference in refractive indices in the exposed and unexposed sections of the hologram.

 The removal of non-photolysed photosensitive material can be performed by washing the porous skeleton with water after step (c).

 Filling the remaining free volume of microcavities with the polymerizable composition can be carried out by immersing the porous glass in a solution of the polymerizable composition and the polymerization step can be carried out in the usual way, for example by heating in a frame autoclave impregnated with the polymerized composition.

 Regardless of the form of the compounds, transition metal ions, for example Cr (III), modify the process of free-radial polymerization of the composition, affecting stereoselectivity.

 As a result, the packing density of the polymer chains formed in the polymerization process is different from the packing density of the chains formed by conventional free radical polymerization without the named ions, and therefore a polymer with a different refractive index is formed.

Examples of polymerizable compositions that can be used in the present invention include polyol (allyl carbonate) compositions, for example diethylene glycol bis-allyl carbonate, known under the trademark CRT-39 ^® , and mixtures thereof with comonomers such as vinyl acetate or oligourethanedimethacrylates; alkyl methacrylates, e.g. methyl methacrylate (MMA); vinyl monomers, for example vinyl acetate (VA), styrene and mixtures thereof, with comonomers such as MMA, VA or acrylonitrol. These compositions typically include, in addition to monomers, free-radical polymerization initiators, such as peroxides or azo compounds.

 The possibility of practical implementation of the attached invention is illustrated by the examples below.

На фиг. 2 представлены зависимости дифракционной эффективности голограмм от силы решетки (χ): кружки соответствуют голограмме, заполненной полидиэтиленгликольбисаллилкарбонатом (HCR-39), и квадраты - голограмме, заполненной полиметилметакрилатом (ПММА). Эти данные отвечают экспериментам, в которых были получены максимальные величины K₁ и K₂.During the experiments, diffraction efficiency was measured at various stages of manufacturing holograms in porous glass. The first series of measurements (η _em ) was performed after exposure and development, when the free volume of the holograms was filled with air. The second series of measurements (η _rf ) corresponds to a hologram filled with a liquid filler with a refractive index equal to the refractive index of the polymer filler, which will be used in the third stage of manufacturing the hologram. The third series of measurements (η _mf ) was performed after completion of the polymerization process. Based on the obtained experimental data, the amplification factors of the holograms were calculated, defined as:

In FIG. Figure 2 shows the dependences of the diffraction efficiency of holograms on the lattice strength (χ): the circles correspond to a hologram filled with polydiethylene glycol bisallyl carbonate (HCR-39), and the squares correspond to a hologram filled with polymethyl methacrylate (PMMA). These data correspond to experiments in which the maximum values of K ₁ and K ₂ were obtained.

 Table 1 shows the hologram gain for both cases.

From this it can be seen that in the case of a polymer filler with a spatially modulated refractive index, values of the gain K ₂ from 5 to 70 times with respect to the same hologram with a liquid filler uniform in refractive index were achieved. It should be noted that when filling a hologram with a polymer filler with a spatially modulated refractive index, its coefficient K ₁ , with respect to the same hologram filled with air, is ~ 2.0 for a PCR-39 filler and 4.5 for a PMMA filler.

The data presented in Table 1 also show that the values of K ₁ and K ₂ do not depend significantly on the type of porous glass and on the nature of the cation (Na ⁺ or NH ₄ ⁺ ) of the photolysed substance. In addition, in the case of PMMA filler, the values of K ₁ and K ₂ increase with decreasing exposure. Therefore, the method of obtaining a hologram proposed in the present invention can significantly increase the photosensitivity of the recording medium.

 Moreover, after filling the hologram with a polymer filler, the light scattering level is significantly reduced. Thus, the transmission of a hologram without a filler at λ = 488 nm is τ = 0.75, but after filling the free volume of the hologram with a polymer, the value of τ increases to 0.90.

доля объема пор ~ 30 ± 1%) было использовано в форме дисков диаметром 40 мм и толщиной 1,5 мм (стекло Тип 1 в Таблице 1). Это стекло было получено кислотным травлением боросиликатного стекла следующего состава: SiO₂- 61,12%; B₂O₃ - 28,03%; Na₂O - 7,65%; Al₂O₃ - 3,17%, в весовых %.Example 1
1. Porous high silica glass (average pore radius

a pore volume fraction of ~ 30 ± 1%) was used in the form of disks with a diameter of 40 mm and a thickness of 1.5 mm (Type 1 glass in Table 1). This glass was obtained by acid etching of borosilicate glass of the following composition: SiO ₂ - 61.12%; B ₂ O ₃ - 28.03%; Na ₂ O - 7.65%; Al ₂ O ₃ - 3.17%, in weight%.

2. The sensitization of the aforementioned porous glass was carried out by its impregnation in an aqueous solution of (NH ₄ ) ₂ Cr ₂ O ₇ with a concentration of 1.25% (wt.), Which was taken in an amount corresponding to a 5–6-fold excess of the solution volume relative to the glass volume . The impregnation process was carried out at 20 ^o C until then, until the optical density of the impregnated porous glass at λ = 488 nm reached 0.25 - 0.30. After that, the porous glass was dried in air at room temperature and the pore volume was filled with immersion - isopropyl alcohol to prevent damage to the glass by moisture.

3. A transmitting hologram was detected by argon laser radiation (488 nm) at a convergence angle of recording beams of 9.2 ^° . The exposure was 0.5 J / cm ² . After recording the hologram, the porous framework was dried in air to remove isopropyl alcohol, then it was washed with distilled water at 20 ^° C for 15 hours and at 70 ^° C for 30 minutes. In conclusion, the removal of water from the porous skeleton was carried out by drying in air and then heating in an oven at 120 ^° C. for 4 hours.

Зависимость дифракционной эффективности от силы решетки представлена на фиг. 2 и величины χ_em, χ_rf/ приведены в Таблице 1. После измерений пористый каркас сушился в вакууме (10^-2 мм Hg) при комнатной температуре (3 ч) и при 100^oC (3 ч).4. The diffraction efficiency of the holograms (η) was measured at λ = 633 nm (He-Ne laser) for an air-dry hologram (η _em ) and for a hologram filled with unpolymerizable material (o-xylene) (η _rf ).
The values of the lattice lattice force (χ) were calculated by the formula:

The dependence of diffraction efficiency on the lattice force is shown in FIG. 2 and the values χ _em , χ _{rf /} are shown in Table 1. After the measurements, the porous skeleton was dried in vacuum (10 ^-2 mm Hg) at room temperature (3 h) and at 100 ^o C (3 h).

 5. Filling the porous hologram with a polymer filler was performed as follows.

 The dried porous glass with a registered hologram was impregnated with a 2% (by weight) solution of azoisobutyric acid dinitrile in methyl methacrylate (MMA) at room temperature.

For polymerization, special forms were prepared in advance. They consisted of two silicate glass disks with plane-parallel polished work planes. Folded discs were tightened around the periphery with a cellophane film (3-4 layers). Previously, the working surfaces of the disks were treated with dichlorodimethylsilane to reduce the adhesion of the polymer to the silicate surface of the mold. An impregnated porous glass with a registered hologram was placed inside the mold into which an initiator solution in MMA was additionally poured so that the glass was completely immersed in it. The form was placed in an autoclave, where an inert gas overpressure (Ar or N ₂ ), 8 atm, was created.

The polymerization process was carried out by heating the autoclave in a liquid thermostat according to the following mode:
Exposure at 60 ^o C - 24 hours,
Raising the temperature to 100 ^o C at a speed of 10 ^o / h,
Exposure at 100 ^o C - 2 h and
Lowering the temperature to room temperature at a rate of 10 ^o / h.

 After depressurizing the autoclave to atmospheric, the autoclave was opened and the sample was removed from the mold.

6. The diffraction efficiency of the hologram recorded in a porous frame impregnated with a polymer filler was measured and the χ _mf value was calculated (See Step 4). Gain factors were determined according to expression (4) and are shown in Table 1.

Example 2
Steps 1-6 of Example 1 were repeated, except that the exposure during registration of the hologram was 3 J / cm ² .

 All experimental data are presented in Table 1.

Example 3
Steps 1-6 of Example 1 were repeated except that:
- the exposure when recording the hologram was 3 J / cm ² (step 3).

- 2% (by weight) initiator solution (benzoyl peroxide) in CR-39 (monomer) was used to impregnate porous glass and to form a polymer filler inside the pores (step 5). The polymerization process was carried out by heating the autoclave in a liquid thermostat according to the following mode:
Exposure at 60 ^o C - 24 hours;
Exposure at 80 ^o C - 65 hours;
Raising the temperature to 100 ^o C at a speed of 10 ^o C / h;
Exposure at 100 ^o C - 1.5 hours and
Lowering the temperature to room temperature at a rate of 10 ^o C / h

 All experimental data are presented in FIG. 2 and in Table 1.

и объемной долей пор 26 ± 1% (стекло Тип II в Таблице 1), полученное кислотным травлением боросиликатного стекла следующего состава (в весовых %): SiO₂ - 67,5%; В₂O₃-24,6%; Na₂O -7,9%; Al₂O₃ - 0,5%;
- сенсибилизация пористого стекла проводилась его пропиткой 10% (по весу) водным Na₂Cr₂O₇ (стадия 2).Example 4
Steps 1-6 of Example 1 were repeated, except that:
- used porous high silica glass with an average pore radius of 40-50

and a pore volume fraction of 26 ± 1% (Type II glass in Table 1) obtained by acid etching of borosilicate glass of the following composition (in weight%): SiO ₂ - 67.5%; In ₂ O ₃ -24.6%; Na ₂ O -7.9%; Al ₂ O ₃ - 0.5%;
- sensitization of porous glass was carried out by impregnating it with 10% (by weight) aqueous Na ₂ Cr ₂ O ₇ (stage 2).

 All experimental data are presented in Table 1.

Claims (21)

 1. Volumetric phase hologram with an interference pattern recorded in the form of local changes in the refractive index, containing a porous transparent silica skeleton having a system of interconnected microcavities or pores, the average radius of which is less than the wavelengths of the radiation recording and reading the hologram, a photolysis product of a photosensitive material, the named product is rigidly attached to the walls of microcavities and spatially distributed in accordance with the intensity of the recorded th interference pattern, characterized in that it additionally incorporates a solid-phase transparent polymer material filling the above micro cavities, while the said polymer material is characterized by a local change in the refractive index, the variations being spatially modulated in accordance with the registered interference pattern, and the named photolysis product is a modifier polymerization for the composition polymerizable in the named polymer, microcavity filling mat Rial.  2. The hologram according to claim 1, characterized in that a homo- or copolymer of polyol- (allyl carbonate) is used as the named polymer material.  3. The hologram according to claim 2, characterized in that diethylene glycol bis-allyl carbonate is used as the named polyol- (allyl carbonate).  4. The hologram according to claim 1, characterized in that the polymer of at least one alkyl methacrylate is used as the named polymer material.  5. The hologram according to claim 1, characterized in that a homo- or copolymer of at least one vinyl monomer is used as said polymer material.  6. The hologram according to claim 2, characterized in that a polyol- (allyl carbonate) copolymer with at least one other copolymerizable monomer selected from the series consisting mainly of vinyl acetate and oligourethanes having terminal dimethyl acrylate is used as the named polymer material.  7. The hologram according to claim 1, characterized in that the styrene copolymer with at least one other copolymerizable monomer selected from the group consisting mainly of methyl methacrylate, vinyl acetate and acrylonitrile is used as the named polymer material.  8. A hologram according to any one of claims 1 to 7, characterized in that said porous skeleton is made in the form of a porous high-silica glass obtained by acid etching of two-phase glass.  9. A hologram according to any one of claims 1 to 7, characterized in that the said porous skeleton is made in the form of porous glass obtained by sol-gel technology.  10. A hologram according to any one of claims 1 to 9, characterized in that said polymerization modifier comprises transition metal ions.  11. A hologram according to any one of claims 1 to 10, characterized in that the product of the photolysable organometallic compound is used as a polymerization modifier. 12. The hologram according to claim 11, characterized in that said organometallic compound is selected from the group consisting of Mn ₂ (CO) ₁₀ , Co ₂ (CO ₈ ), Cr (CO) ₆ , Mo (CO) ₆ and Ti (cyclopentadiene) Cl ₂ ). 13. A hologram according to any one of claims 1 to 10, characterized in that said polymerization modifier is the photolysis product of Cr ^VI . 14. The hologram of claim 13, wherein said Cr ^VI salt is selected from the group consisting mainly of (NH ₄ ) ₂ Cr ₂ O ₇ , Na ₂ Cr ₂ O ₇ and K ₂ Cr ₂ O ₇ . 15. A hologram according to any one of claims 1 to 14, characterized in that the said polymerization modifier is directly attached to the walls of the microcavities of the named framework.  16. A hologram according to any one of claims 1 to 14, characterized in that said polymerization modifier is enclosed in a layer covering the walls of microcavities of said framework.  17. The hologram according to clause 16, wherein the said shell is made in the form of a photoresistor. 18. The hologram according to claim 17, characterized in that said photoresistor is made of gelatin and said ions of Cr ^III are said polymerization modifier.  19. The hologram according to claim 17, characterized in that said photoresistor is made of polyvinyl alcohol.  20. The hologram according to claim 17, characterized in that said photoresistor is made of shellac.  21. An optical device containing a light source and at least one optical element, characterized in that said at least one optical element is made in the form of a hologram according to any one of claims 1 to 20.  22. A method of manufacturing a hologram according to any one of the preceding paragraphs, wherein a transparent porous silica framework is obtained having a system of interconnected microcavities or pores, the average radius of which is less than the wavelengths of the radiation recording and reading the hologram, characterized in that they cover the walls of these microcavities with a photosensitive material whose photolysis product is a polymerization modifier for at least one of the selected polymerizable compositions, register a holographic interference pattern in the said material so that the named photolysis products are distributed on the walls of the individual named microcavities in accordance with the named interference pattern, the non-photolysed photosensitive material is removed, the remaining free volume of the named microcavities of at least one of the selected polymerizable compositions is filled, the named composition is polymerized so as to obtain a volumetric phase hologram made of transparent th frame filled with a solid phase polymeric material with spatial modulated refractive index, wherein the refractive index modulation period of said polymer must be the same as the period of spatial distribution of said photolysis products.

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