Cholesteric photoactive compound for generating laser emission

FIELD: physics, photographic material.

SUBSTANCE: invention pertains to polymer cholesteric photoactive compounds, which can independently generate laser emission when irradiated with laser light. Such a compound can be used, for example, in photonics, optoelectronics and telecommunication systems. The cholesteric photoactive compound for generating laser emission consists of cholesteric liquid crystal, photoactive additive and laser dye. The liquid crystal used contains conjoint polymer n-(6-acrylyl oxycapril hydroxyphenyl)-n-methoxy benzoate with cholesterine-11-acrylyl undecanoate, containing molar quantities between 30% and 25% of the cholesterine-11-acrylyl undecanoate links. Photoactive additive used is 2.5-bis(4-methoxy cynnamoyl)-1.4;3.6-dianhydro-B-sorbitol, while the laser dye used is 4-(dicyano methylene)-2-methyl-6-(4-dimethyl amino styryl)-4H-pyran. The invention improves the temporal and thermal stability of the compound, and allows for its use at room temperatures and at lower temperatures as well. Sensitivity of the compound to external effects is also lowered.

EFFECT: increased thermal stability of photoactive compounds and lower sensitivity to external effects.

2 ex, 1 dwg

 

The invention relates to the field of polymer cholesteric photoactive compositions, capable under the influence of irradiation of the laser light independently to generate laser radiation. Such compositions can be used, for example, in Photonics, optoelectronics, telecommunications systems, as well as in other areas, which are traditionally used laser technology.

Known cholesteric photoactive composition for generation of laser radiation on the basis of low-molecular weight liquid crystal (GCR) and laser dye (P.V.Shibaev, R.L.Sanford, D.Chiappetta, V.Milner, A.Genack, A.Yu.Bobrovsky, "Light controllable tuning and switching of losing in chiral liquid crystals" // Optics Express, 2005, 13, 7, 2358).

The disadvantage of this arrangement is the difficulty of its application, due to the liquid state of aggregation of the composition, requiring the creation of a special hermetic cells that protect the composition from external influences.

Known cholesteric photoactive composition for generation of laser radiation on the basis of polymerizable mixtures of mesogenic monomers and laser dyes (Pview, Nijana, Awesomsauce, Wpimages. "Generation of laser radiation in polymer cholesteric grids" // high-Molecular compounds. 47A, 6, 961, 2005).

The disadvantages of such compositions are the difficulty of retaining a uniform mono-domain planar the nd patterns in the polymerization mixture of monomers in the composition and poor reproducibility of the process of obtaining a uniform mono-domain structure, leading to poor performance of the composition.

Closest to the claimed is cholesteric photoactive composition for generating laser radiation, consisting of a cholesteric GCR (representing a mixture of nematic GCR unknown composition produced by the company Merck under the trade name (brand) Zli is-1695, chiral photoactive additive manufactured by the company Merck under the trade name (brand) Zli is-811, transforming, in addition, the nematic phase GCR in cholesteric) and laser dye n-decyloxy-n'-centerpanel, in the following ratio, wt.%:

Zli is-169563,6
Zli is-81135,8
n-decyloxy-n'-centerpanel0,6

(A.Chanishvili, G.Chilaya, G.Petriashvili, R.Barberi, R.Bartolino, G.Cipparrone, A.Mazzulla, L.Oriol "lasing in dye-doped cholesteric liquid crystls: two new tuning strategies" // Advanced Materials, 2004, 16, No. 9-10, 791) prototype.

The disadvantages of the known compositions are its instability over time and its sensitivity to external influences (temperature, mechanical, photochemical, and so on), due to the liquid state of aggregation of the composition, which leads to uncontrolled changes in its optical properties. For example, cooling the composition below 15°it leads to Cree is tallization and loss of performance properties.

An object of the invention is the creation of a cholesteric photoactive composition characterized by high temporal stability (years), thermal stability, including the possibility of its use at low temperatures down to -20°and low sensitivity to external influences.

This technical result is achieved by the fact that in the known cholesteric compositions for generating laser radiation, consisting of a cholesteric JKR, photoactive additives and laser dye, as JKR use a copolymer of n-(6-acryloyloxyhexyloxy)-n-methoxybenzoate (AA) with cholesteryl-11-akiloyunlari.com (HA), containing from 33 to 35 mol.% links HA, as photoactive additives use of 2,5-bis(4-methoxycinnamyl)-1,4; 3,6-dianhydro-D-sorbitol (Sorb), as a laser dye using 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-Piran, (DCM) in the following ratio, wt.%:

The copolymer of AA HA98-99
Sorb0,5-1,0
DCM0,5-1,0

Synthesis of copolymer of AA HA, having the structural formula shown in the drawing, described in (Niebaum, Diss. on saisc. academic degree Cand. chem. Sciences. Moscow, Moscow state University, 1988). what was experimentally detected, to obtain good results only suitable alloy containing from 30 to 35 mol.% links HA. Brednikova molecular weight (MP) of such alloy may vary within wide limits, for example from 10 to 30 kDa.

Synthesis of photoactive additives Sorb described in the literature (monitoring computerized. Bobrovsky, N.I.Boiko, V.P.Shibaev "New chiral-photochromic dopant with variable helical twisting power and its use in photosensitive cholesteric materials // Molecular Crystals and Liquid Crystals 2001, vol.363, 503).

The proposed laser dye DCM, produced under the trademark of DSM known. (Ulrich Brackmann, Lambdachrome Laser Dyes", D-37079 Goettingen, Germany, 2000, p.185).

The use of the proposed composition for the generation of laser radiation based on the introduction of small additives of laser dyes, which under the action of an external laser pump (external laser) are starting to generate laser radiation.

Photoactivity proposed composition depends on the composition and may be manifested as occurrence of lasing under irradiation optical cell with a composition by ultraviolet light, and the disappearance of laser generation under the action of UV radiation.

Laser generation of the proposed compositions recorded in the cells representing the two glass plates coated with polyimide coating, grated in one direction to create a planar orientation. The cell gap created with the help of two Teflon speicherbereich thickness.

Emission is observed in the direction perpendicular to the film plane, in the region of wavelengths corresponding to the edge of the photonic bandgap, i.e. on the border strip of selective reflection of light λmax.

The advantage of the proposed composition explain the following examples.

Example 1.

Cholesteric photoactive composition is prepared from a copolymer of AA HA with Mn=12 kDa, containing 33 mol.% links HA, with a glass transition temperature of 26°C, the temperature of the enlightenment 122°and a wavelength selective light reflection 565 nm. The composition is obtained by dissolving 98.5 mg (98.5 wt.%) the above CPF, 1.0 mg (1.0 wt.%) Sorb and 0.5 mg (0.5 wt.%) DCM in 0.5 ml of chloroform with subsequent removal of the chloroform in a drying Cabinet at 60°and drying in vacuum at a temperature of 120°C.

For manufacturing cell using glass plates coated with polyimide coating, grated in one direction to create a planar orientation. The cell gap created with the help of two Teflon spacers with a thickness of 20 μm. Filling the cell composition is realized by means of capillary forces when heated compositions and cells up to 150°C. thereafter, the cell is annealed for 1 h at a temperature of 112°10° below the temperature of enlightenment, then cooled to room temperature at a rate of 1° /min

For optical pumping of a laser dye, i.e. for the generation of laser radiation, use of a pulsed radiation of the second harmonic (532 nm) of Nd3+YAG laser operating in the modulation mode q-factor (pulse duration 5 NS, repetition rate 5 Hz). The pumping radiation is focused on the sample by a lens with a focal length of 28 cm, giving a focal plane spot size of 0.3 mm2.

The incident laser beam is directed at an angle of 45° to the normal plane of the cell and is generated in the direction normal to the radiation detected through the system, including fiber optic cable - CCD spectrometer (spectral resolution of 0.6 nm) - based computer.

Prepared cell filled with planar-oriented cholesteric composition, does not have a laser generation. Photoactivity this composition is manifested in the fact that UV irradiation of the cell with light of a wavelength of 365 nm for 3 h leads to the shift of the peak selective reflection of light by 30 nm in the wavelength region of the spectrum and the appearance of several narrow bands of laser generation (599.5 nm, 610.3 nm and 642.4 nm).

Check the intensity of the laser generating composition and its spectral range, conducted after 6 and 12 months after its preparation, showed the stability of the above operational characteristics. Received the song because of its solid aggregate state has low sensitivity to external influences.

Example 2.

The experience carried out analogously to example 1, but using alloy containing 35 mol.% links HA, with a glass transition temperature of 27°C, the temperature of the enlightenment 124°and a wavelength selective light reflection 558 nm. The composition is obtained by dissolving 98.0 mg (98.0 wt.%) the above CPF, 1.0 mg (1.0 wt.%) Sorb and 1.0 mg (1.0 wt.%) DCM in 1.0 ml of chloroform with subsequent removal of the chloroform in a drying Cabinet at 60°and drying in vacuum at a temperature of 120°C.

Prepared cell filled with planar-oriented cholesteric composition at a temperature of 0°has a laser generation with a strip of 639 nm.

Photoactivity this composition is manifested in the fact that UV irradiation of the cell with light of a wavelength of 365 nm for 3 h leads to the shift of the peak selective reflection of light in the wavelength region of the spectrum and the extinction of laser generation.

Check the intensity of the laser generating composition and its spectral range, conducted after 6 and 12 months after its preparation, showed the stability of the above operational characteristics. The resulting composition due to its solid aggregate state has low sensitivity to external influences.

Thus, the proposed composition really helps to increase a temporary camera is lnost composition until at least 1 year, to reduce the sensitivity of the composition to external influences and to improve its thermal stability, including the possibility of its use at room and lower temperatures.

Cholesteric photoactive composition for generating laser radiation, consisting of a cholesteric liquid crystal photoactive additives and laser dye, characterized in that the liquid crystal used is a copolymer of n-(6-acryloyloxyhexyloxy)-n-methoxybenzoate with cholesteryl-11-akiloyunlari.com containing from 30 to 35 mol.% links cholesteryl-11-acrylamidoglycolate, as photoactive additives use of 2,5-bis(4-methoxycinnamyl)-1,4;3,6-dianhydro-D-sorbitol as a laser dye using 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-Piran, in the following ratio, wt.%:

copolymer of n-(6-aryloxyalkyl)-
n-methoxybenzoate with cholesteryl-
11-akiloyunlari.com98-99
2,5-bis(4-methoxycinnamyl)-1,4;3,6-dianhydro-
D-sorbitol0,5-1,0
4-(dicyanomethylene)-2-methyl-6-
(4-dimethyl nostril)-4H-Piran 0,5-1,0



 

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