Production process for growing crystals of gallium scandium gadolinium garnets for passive q-switches

FIELD: chemistry; passive Q-switch crystal growing process.

SUBSTANCE: production process for growing crystals of galium scandium gadolinium garnets is based on Czochralski process, which implies crystal growing from initial molten batch, which is congruently melting gallium scandium gadolinium garnet produced by 3-phase synthesis, doped with magnesium oxide and chromium oxide. These oxides provide for 2.0×1020-2.6×1020 atoms/cm3 concentration of cromium and magensium cations in melt during the first crystal growing, in argon with 14-17% of carbon dioxide, pressure in chamber being 1.3-2.0 atm. For the second, third and subsequent growths, an initial batch amount equal to previous crystal weight, cromium and magnesium content in batch being determined according to formula (СCr×СMg)/1020 = 0.5÷2, where СCr is at least 5×1019 atoms/cm3, is added to the crucible.

EFFECT: provides for required Q-switched mode, continuous or pulse, within wavelength range of 1,057-1,067 mcm.

2 ex

 

The invention relates to a passive laser paddles for modern lasers used in optical and optoelectronic devices such as laser range finders operating in the near infrared region of the spectrum. Can also be used to obtain fluorescent and photo - and katotohanan materials based on gallium-scandium-gadolinium garnet and other single crystals of multicomponent oxides containing oxides of gallium and chromium.

A method of obtaining a passive laser paddles from single crystals of yttrium aluminium garnet doped with vanadium cations grown by the method of Bridgeman (see Ivanov V.I., Krutova L.K., Mironov, I., and others, proceedings of the 6th International conference "Applied optics-2004". St. Petersburg, October 2004, V. 4, p.41-45). However, this technology does not allow repeated growing of crystals to generate passive laser paddles.

Known technology passive gates of crystals of yttrium aluminium garnet doped with vanadium, where as the original mixture, a mixture of metal oxides stoichiometric composition of garnet, which fuse at temperatures of 1970°With a nitrogen atmosphere with the addition of oxygen, and then grow the crystal by the Czochralski method with subsequent annealing in reducing atmosphere (Merczyk Z., Z. Frukacz, OPTO-ELECTRONIC REVIEW, v 8, (1), 2000, page 67-74). In this study, no data on the serial cultivation of crystals for passive valves. The unknown authors of the work on this topic.

Closest to the proposed technical solution is the method of growing crystals based on gallium-scandium-gadolinium garnet for passive laser paddles by the Czochralski method from the iridium crucible with the melt mixture of a mixture of metal oxides - SU 1667587 A1, 27.01.1995. However, when using gallium-scandium-gadolinium garnet obtained by this method (compositions 1 and 2)obtained small values of absorption coefficients, and at high concentrations of the ingredients of the charge MgO×Cr2About3(3) there is a reduction optical homogeneity of plane-parallel plates, which were used as phototrophic paddles in neodymium lasers. In this way not provided by the seriation of growing crystals, i.e. the possibility of using the melt after the previous growing with the addition of the charge of the corresponding composition.

The objective of the proposed technological solution is the improvement of the method of obtaining passive laser paddles for operation in the wavelength range 1,057-1,067 microns, providing the necessary modulation mode q-factor in the continuous and the pulse modes for growing crystals from a mixture of metal oxides, consisting of serial cultivation of crystals of gallium-scandium-gadolinium garnet doped with cations of chromium, using the remainder of the original charge in the crucible and, as a consequence, saving costly mixture of high-purity metal oxides, as well as the simplification and reduction of process cycle at the stage of growing crystals and all technology in General.

Delivered process is accomplished in a serial fashion for growing crystals of gallium-scandium-gadolinium garnet for passive laser paddles by the Czochralski method from a melt source blend containing a mixture of metal oxides constituting obtained by the method of solid-phase synthesis of gallium-scandium-gadolinium garnet congruently melting composition with additives of magnesium oxide and chromium oxide, providing the concentration of cations of chromium and magnesium in the melt for growing a first crystal 2.0 to 2.6×1020atoms/cm3while growing crystal is carried out at a chamber pressure of 1.3 to 2.0 ATM in argon and carbon dioxide with a volume share of the latter in the gas mixture 14-17%, and in the second, third and subsequent vyrashivaniem in the crucible add the amount of the original charge, equal to the weight of the previous crystal composition in which a part of the cations of chromium and magnesium determined by the formula (CCr×C Mg/1020=0,5÷2, CCrnot less than 5×1019atoms/cm3.

The invention consists in the following: passive laser gates of gallium-scandium-gadolinium garnet doped with cations of chromium, used in lasers at the wavelength of the generation of the active element on the basis of neodymium (1,057-1,067 μm) to provide the necessary modulation mode q-factor in the continuous and pulsed modes of operation of the device. At the stage of growing crystals of gallium-scandium-gadolinium garnet doped with cations of chromium, there was no cultivation technology series, without complete replacement of the original charge, because of the high volatility of gallium oxide at high temperatures changes in the composition of garnet at the stage of synthesis, and at the stage of growing crystal from the melt. The lack of direct correlation between the quantity of the alloying additives in the form of cations (Cr4+in the crystal and the melt on the concentration of cations of chromium due to the diversity of the cationic forms of chromium was not possible to calculate the necessary number of metal oxides and alloying additives to compensate for their disadvantage in the melt for growing crystals of the required quality and of obtaining from them a passive laser paddles. Generalizing a technological problem, we can say that it is necessary to create and maintain conditional "material is Noah" the balance of the melt-crystal-additive, in terms of ingredients, in a series of five versiani that is the best option.

The mentioned problems are eliminated by the fact that they use the initial charge of gallium-scandium-gadolinium garnet congruent composition with additives of magnesium oxide and chromium oxide, providing the concentration of chromium cations WithCrand magnesium CMgin the melt 2×l020-2,6×l020atoms/cm3. This range of concentrations of these cations in the mixture provides the desired concentration of chromium cations when growing the first crystal. Next, synthesize garnet method of solid-phase synthesis, crystal growth is carried out in argon and carbon dioxide, the volume fraction of the latter 14-17% in the gas mixture. The pressure in the chamber may vary from 1.3 to 2 ATM. When the pressure in the chamber is less than 1.3 ATM change dramatically, due to the high volatility of gallium, the composition of the melt, which causes formation of a second phase in the crystal. At a pressure of more than 2 atmospheres. change the temperature gradients over the surface of the melt, the crystal cracks. When the second, third and subsequent vyrashivaniem in the crucible add the initial charge in the amount equal to the weight of the previous crystal composition in which a part of the cations of chromium and magnesium is defined as (CCr×CMg)/1020and equal to the values from 0.5 to 2 CCr not less than 5×1019atoms/cm3whereCrCMgthe concentration of cations of chromium and magnesium in the melt.

Additive by weight, is equal to the previous crystal ensures that the initial conditions for growing crystals and the material balance from cultivation to cultivation. This ratio of concentrations of cations of chromium and magnesium in additive allows to maintain the desired concentration of cations (Cr4+in the melt during the second, third and subsequent vyrashivaniem to the fifth, as well as in the crystal. The behavior of the following versiani unprofitable, due to the large number of iridium (the material) in the melt.

The use of the proposed process parameters for a series of five versiani crystals of gallium-scandium-gadolinium garnet doped with chromium, provides obtaining suitable crystals for the manufacture of passive laser gates, operating in the wavelength range 1.057-1,067 microns and providing the necessary modulation mode q-factor in the continuous and pulsed modes of operation.

As the example shows two series of growing crystals of gallium-scandium-gadolinium garnet doped with cations of chromium, with an absorption coefficient of 4.8-5,9 cm-1at a wavelength of 1,067 mm. Of the crystals after cutting, grinding, polishing and coating the lumen of the shining coatings were obtained certified passive laser gates absorption coefficient 12-32% at a wavelength of 1,067 microns in diameter, 7 and 8 mm

The serial method of growing crystals of gallium-scandium-gadolinium garnet for passive laser paddles by the Czochralski method from a melt source charge representing obtained by the method of solid-phase synthesis of gallium-scandium-gadolinium garnet congruently melting composition with additives of magnesium oxide and chromium oxide, providing the concentration of cations of chromium and magnesium in the melt for growing a first crystal 2.0·1020-2,6·1020atoms/cm3while growing crystal is carried out at a chamber pressure of 1.3 to 2.0 ATM in argon and carbon dioxide with a volume share of the latter in the gas mixture 14-17%, and in the second, third and subsequent vyrashivaniem in the crucible add the amount of the original charge, equal to the weight of the previous crystal composition in which a part of the cations of chromium and magnesium determined by the formula (CCr·CMg)/1020=0,5÷2, CCrnot less than 5·1019atoms/cm3.



 

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