CN102051684A - Method for growing thulium-holmium co-doped yttrium calcium aluminate laser crystal - Google Patents

Abstract

A method for growing a thulium-holmium co-doped calcium yttrium aluminate laser crystal comprises the following steps: Tm ³⁺ and Ho ³⁺ rare earth ions are directly doped simultaneously in a CaYAlO ₄ crystal matrix, and a high-quality Tm/Ho:CaYAlO ₄ laser crystal is grown by a Czochralski method. Experiments show that the method is feasible, and the grown crystal is complete without cracks or macroscopic defects, and can be used as a laser medium.

Description

Growth method of thulium-holmium co-doped yttrium-calcium aluminate laser crystal

technical field

The invention relates to a laser crystal, in particular to a growth method of a thulium-holmium co-doped yttrium-calcium aluminate laser crystal (abbreviated as Tm/Ho:CaYAlO ₄ hereinafter).

Background technique

Laser diode-pumped solid-state lasers have the advantages of compact structure, good beam quality, and high energy. They are widely used in industry, defense and other fields. Due to the ⁵ I ₇ → ⁵ I ₈ energy level transition of Ho ³⁺ , Ho ³⁺ doped solid-state lasers have a unique advantage in lasing in the 2 μm band. However, there is no suitable laser diode pumping source for Ho ³⁺ doped laser crystals at present, and Tm ³⁺ ion laser resonant pumping is often used to achieve laser output.

A simpler method is to directly co-dope Tm ³⁺ and Ho ³⁺ into a certain crystal matrix, so that the energy transfer between particles can be completed within the same matrix, thereby simplifying the laser structure and achieving the purpose of efficient operation. In 2010, AALagatsky et al. reported for the first time the femtosecond-level output of Tm, Ho co-doped laser crystals, and the average output laser power reached 130mW at 2055nm (see Optics Letters, 35(2010), 172). CaYAlO ₄ has a perovskite structure, and the rare earth elements Tm and Ho are in C _4v symmetric positions in the crystal lattice. CaYAlO ₄ crystal has excellent physical properties and is an ideal disordered laser host. Double-doped Tm/Ho:CaYAlO ₄ crystal has not been reported yet.

Contents of the invention

The purpose of the present invention is to provide a growth method of thulium-holmium co-doped yttrium-calcium aluminate laser crystal, directly doping Tm ³⁺ and Ho ³⁺ rare earth ions in the CaYAlO ₄ crystal matrix, and adopting the pulling method to grow and prepare high-quality Tm /Ho:CaYAlO ₄ laser crystal.

Technical solution of the present invention is as follows:

A kind of growth method of thulium holmium co-doped yttrium calcium aluminate laser crystal is characterized in that comprising the following steps:

① Grow Tm/Ho:CaYAlO ₄ crystals by medium frequency induction heating and pulling method, the heating element is an iridium crucible, and the raw materials of the crystals are weighed according to the molar ratio of the following reaction formula:

2CaCO ₃ +(1-xy)Y ₂ O ₃ +xHo ₂ O ₃ +yTm ₂ O ₃ +Al ₂ O ₃ ＝2CaY _(1-xy) Ho _x Tm _y AlO ₄ +2CO ₂

The value range of x and y is: 0<x≤0.008, 0<y≤0.12;

② After the raw materials are mixed evenly, they are compacted into blocks under a hydraulic press, and sintered in a muffle furnace at 1200°C for 10 hours, a solid phase reaction occurs, and the sintered blocks are put into an iridium crucible and pulled Growth single crystal furnace;

③The single crystal furnace is evacuated to high vacuum, and then filled with nitrogen atmosphere, the growth temperature is 1810°C, the crystal pulling speed is 1-2mm/h, and the rotation speed is 10-20rpm;

④Put the seed crystal deep into the melt, shrink the neck of the crystal, shoulder it, and grow it with equal diameters. At the end stage, pull the crystal out of the melt, and then slowly lower the temperature in the single crystal pulling furnace to room temperature;

⑤ Open the heat preservation cover, take out the seed crystal frame from the pulling growth single crystal furnace, take out the crystal, and obtain the thulium-holmium co-doped yttrium-calcium aluminate laser crystal.

After the crystal raw material is raised to 1810° C. in the pulling and growing single crystal furnace, the temperature in the furnace is continuously raised to 1820-1900° C. and kept for 0.5-1 hour to allow the molten liquid to fully melt and mix.

The composition of the seed crystal is CaYAlO ₄ , or Tm/Ho:CaYAlO ₄ , and the direction of the end face of the seed crystal is [100], [101], or [001].

The device for growing Tm/Ho:CaYAlO ₄ laser crystals by the pulling method used in the present invention is an ordinary medium frequency induction heating single crystal furnace. The whole system includes iridium crucible, vacuum equipment, medium frequency induction generator power supply and temperature control and other parts.

Experiments show that the method of the invention is feasible, and the grown crystal is complete without cracks and macroscopic defects, and can be used as a laser medium. When the [100] direction seed crystal is used, there is a very good (001) crystal plane on the crystal surface, which further illustrates the feasibility of preparing Tm/Ho:CaYAlO ₄ laser crystals by this method.

Description of drawings

Fig. 1 is the polarized absorption spectrum of CaY _0.935 Ho _0.005 Tm _0.06 AlO ₄ crystal of one embodiment of the present invention

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention should not be limited thereby.

Example 1:

Get x=0.005, y=0.06 in the raw material proportioning of this embodiment. CaCO ₃ , Y ₂ O ₃ , Ho ₂ O ₃ , Tm ₂ O ₃ , and Al ₂ O ₃ high-purity raw materials (the content of which is greater than 99.999%) are weighed according to the stoichiometric ratio of 2:0.935:0.005:0.06:1. After mechanically mixing evenly, use a plexiglass mold to press on a press to form a block. The pressed material was sintered in a muffle furnace at 1200°C for 10 hours. Then put the cooled material into the iridium crucible, and then into the pulling single crystal furnace. After the furnace is evacuated, it is filled with nitrogen. Raise the temperature to 1850°C, let the materials fully melt and mix, then cool down to 1810°C after 1 hour, put down the CaYAlO ₄ seed crystal in the [100] direction, and start growing crystals, the crystal pulling speed is 1.2mm/h, and the rotation speed is 10rpm. After growing the crystal, it was slowly lowered to room temperature, and the crystal was taken out. The crystal is intact without cracks, and it can be seen from the morphology of the tail that the crystal grows as a plano-convex interface.

Orient the above-mentioned CaY _0.935 Ho _0.005 Tm _0.06 AlO ₄ single crystal, and cut out 11×10×1 mm ³ slices. After the thin slices were optically polished, the polarized absorption spectra at room temperature were measured using a Lambda 900 spectrophotometer. Fig. 1 shows the polarized absorption spectrum of the CaY _0.935 Ho _0.005 Tm _0.06 AlO ₄ single crystal sheet in the 300-2200 nm band of this embodiment, which can be used as a laser medium.

Example 2:

Take x=0.005, y=0.10 in the raw material proportioning of present embodiment. CaCO ₃ , Y ₂ O ₃ , Ho ₂ O ₃ , Tm ₂ O ₃ , and Al ₂ O ₃ high-purity raw materials (the content of which is greater than 99.999%) are weighed according to the stoichiometric ratio of 2:0.895:0.005:0.10:1. After mechanically mixing evenly, use a plexiglass mold to press on a press to form a block. The pressed material was sintered in a muffle furnace at 1200°C for 10 hours. Then put the cooled material into the iridium crucible, and then into the pulling furnace. After the furnace is evacuated, it is filled with nitrogen. Raise the temperature to 1840°C, let the materials fully melt and mix, then cool down to 1810°C after 1 hour, put down the [101] direction CaYAlO ₄ seed crystal, and start to grow the crystal. The crystal pulling speed is 1.0 mm/h, and the rotation speed is 15 rpm. After growing the crystal, it was slowly lowered to room temperature, and the crystal was taken out, and the crystal was intact without cracking. In this embodiment, the crystal grown from the [101] direction seed crystal does not show a cleavage plane on the surface.

Example 3:

Get x=0.004, y=0.08 in the raw material proportioning of present embodiment. CaCO ₃ , Y ₂ O ₃ , Ho ₂ O ₃ , Tm ₂ O ₃ , and Al ₂ O ₃ high-purity raw materials (the content of which is greater than 99.999%) are weighed according to the stoichiometric ratio of 2:0.916:0.004:0.08:1. After mechanically mixing evenly, use a plexiglass mold to press on a press to form a block. The pressed material was sintered in a muffle furnace at 1200°C for 10 hours. Then put the cooled material into the iridium crucible, and then into the pulling furnace. After the furnace is evacuated, it is filled with nitrogen. Raise the temperature to 1820°C, let the materials fully melt and mix, then cool down to 1810°C after 0.5 hours. The seed crystal adopts the [100] direction Tm/Ho:CaYAlO ₄ seed crystal to start growing the crystal. The crystal pulling speed is 1.3 mm/h, and the rotation speed is 20 rpm. After growing the crystal, it was slowly lowered to room temperature, and the crystal was taken out. The crystal is complete without cracks. It can be seen from the tail that the tail shows a plano-convex interface when the crystal grows, and it well reflects the (001) crystal plane. In this embodiment, the heat preservation time after the chemical is slightly shorter, but compared with the above-mentioned embodiment in the next seeding stage, there is no obvious difference observed.

Example 4:

Get x=0.004, y=0.12 in the raw material proportioning of present embodiment. CaCO ₃ , Y ₂ O ₃ , Ho ₂ O ₃ , Tm ₂ O ₃ , and Al ₂ O ₃ high-purity raw materials (the content of which is greater than 99.999%) are weighed according to the stoichiometric ratio of 2:0.876:0.004:0.12:1. After mechanically mixing evenly, use a plexiglass mold to press on a press to form a block. The pressed material was sintered in a muffle furnace at 1200°C for 10 hours. Then put the cooled material into the iridium crucible, and then into the pulling furnace. After the furnace is evacuated, it is filled with nitrogen. Raise the temperature to 1840°C, let the materials fully melt and mix, then cool down to 1810°C after 1 hour. Put down the [001] direction Tm/Ho:CaYAlO ₄ seed crystal and start to grow the crystal. The crystal pulling speed is 1.5 mm/h, and the rotation speed is 20 rpm. After growing the crystal, it was slowly lowered to room temperature, and the crystal was taken out, and the quality of the crystal was good.

Example 5:

Get x=0.006, y=0.10 in the raw material proportioning of present embodiment. CaCO ₃ , Y ₂ O ₃ , Ho ₂ O ₃ , Tm ₂ O ₃ , and Al ₂ O ₃ high-purity raw materials (the content of which is greater than 99.999%) are weighed according to the stoichiometric ratio of 2:0.894:0.006:0.10:1. After mechanically mixing evenly, use a plexiglass mold to press on a press to form a block. The pressed material was sintered in a muffle furnace at 1200°C for 10 hours. Then put the cooled material into the iridium crucible, and then into the pulling furnace. After the furnace is evacuated, it is filled with nitrogen. Raise the temperature to 1840°C, let the materials fully melt and mix, then cool down to 1810°C after 1 hour, put down the [101]CaYAlO ₄ seed crystal, and start to grow the crystal. The crystal pulling speed is 1.5 mm/h, and the rotation speed is 20 rpm. After growing the crystal, it was slowly lowered to room temperature, and the crystal was taken out.

Embodiment 6:

Get x=0.008, y=0.08 in the raw material proportioning of present embodiment. CaCO ₃ , Y ₂ O ₃ , Ho ₂ O ₃ , Tm ₂ O ₃ , and Al ₂ O ₃ high-purity raw materials (the content of which is greater than 99.999%) are weighed according to the stoichiometric ratio of 2:0.912:0.008:0.08:1. After mechanically mixing evenly, use a plexiglass mold to press on a press to form a block. The pressed material was sintered in a muffle furnace at 1200°C for 10 hours. Then put the cooled material into the iridium crucible, and then into the pulling furnace. After the furnace is evacuated, it is filled with nitrogen. Raise the temperature to 1840°C, let the materials fully melt and mix, then cool down to 1810°C after 1 hour, put down the [001]CaYAlO ₄ seed crystal, and start to grow the crystal. The crystal pulling speed is 1.5 mm/h, and the rotation speed is 15 rpm. After growing the crystal, it was slowly lowered to room temperature, and the crystal was taken out. The crystal had no cracks and no macroscopic defects.

Claims (3)

1. the growth method that the thulium holmium is mixed the yttrium-calcium aluminate laser crystals altogether is characterized in that comprising the following steps:

1. adopt Frequency Induction Heating Czochralski grown Tm/Ho:CaYAlO ₄Crystal, heating element are iridium crucible, and this crystalline raw material takes by weighing according to the mol ratio of following reaction formula:

2CaCO ₃+(1-x-y)Y ₂O ₃+xHo ₂O ₃+yTm ₂O ₃+Al ₂O ₃＝2CaY _(1-x-y)Ho _xTm _yAlO ₄+2CO ₂

Wherein the span of x and y is: 0＜x≤0.008,0＜y≤0.12;

2. described raw material is ground be mixed even after, under hydropress, be compacted into piece, and in retort furnace 1200 ℃ of sintering 10 hours, solid state reaction takes place, the piece material that sinters pack into the iridium crucible and the czochralski furnace of packing into;

3. described single crystal growing furnace pumping high vacuum charges into nitrogen atmosphere then, 1810 ℃ of growth temperatures, crystal pull rate 1-2mm/h, speed of rotation 10-20rpm;

4. seed crystal is goed deep into melt, through the crystal necking down, shouldering, isodiametric growth, the ending stage, crystal is pulled from melt, slowly reduce the interior temperature of lifting furnace then to room temperature;

5. stay-warm case is opened in blowing out, takes out the seed crystal frame in the pulling growth single crystal growing furnace, takes out crystal, obtains the thulium holmium and mixes the yttrium-calcium aluminate laser crystals altogether.

2. thulium holmium according to claim 1 is mixed the growth method of yttrium-calcium aluminate laser crystals altogether, after it is characterized in that in lifting furnace, rising to 1810 ℃, and temperature to 1820 in the continuation rising stove～1900 ℃, and kept 0.5～1 hour, allow the liquation body fully melt mixing.

3. thulium holmium according to claim 1 is mixed the growth method of yttrium-calcium aluminate laser crystals altogether, it is characterized in that described seed crystal composition is CaYAlO ₄, or Tm/Ho:CaYAlO ₄, seed crystal end face direction is [100], [101], or [001].

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