CN1424437A - Preparation method of neodymium-doped yttrium aluminum garnet and yttrium aluminum garnet composite laser crystal - Google Patents

Abstract

A preparation method of Nd-doped yttrium aluminum garnet and pure yttrium aluminum garnet composite laser crystal, which is characterized in that a resistance heating liquid phase epitaxy furnace is used, and a Nd:YAG single crystal substrate with a crystal plane direction of (111) is used as a large area The seed crystal, at the crystallization temperature of the YAG single crystal, grows a YAG single crystal of equal thickness on the two interfaces in contact with the saturated solution containing the YAG polycrystalline material and flux. The YAG/Nd:YAG/YAG composite laser crystal prepared by this method has the advantages of good crystal integrity, good repeatability, and no obvious interface. After cutting, rounding, processing, and coating, it can be made into an all-solid-state continuous laser, laser It has good laser performance and low laser threshold.

Description

Preparation method of neodymium-doped yttrium aluminum garnet and yttrium aluminum garnet composite laser crystal

Technical field:

The present invention relates to the growth method of neodymium-doped yttrium-aluminum garnet (Nd:YAG) and yttrium-aluminum garnet (YAG) composite laser crystals, in particular to growing non-doped The yttrium-aluminum garnet is combined into a composite laser crystal material of Nd-doped yttrium-aluminum garnet and yttrium-aluminum garnet: YAG/Nd:YAG/YAG.

Background technique:

Neodymium-doped yttrium aluminum garnet (Nd:YAG) laser crystal has excellent laser and physical and chemical properties, and is one of the most widely used solid-state laser gain media. Due to the small quantum efficiency of the Nd:YAG crystal, when a large amount of heat generated by the non-radiative transition propagates in the gain medium, the Nd:YAG crystal produces a thermal lens effect, thereby reducing its laser efficiency and laser beam quality.

In order to compensate for this thermal effect of Nd:YAG crystals, in 1998 R..Weber et al. proposed a composite structure of optically glued pure YAG crystals at both ends of the Nd:YAG laser rod. On the one hand, pure YAG crystals do not absorb pump light or oscillate Light can effectively cool the gain medium and reduce thermal effects and thermal lens effects; on the other hand, coating both ends of pure YAG rods has a significant effect on increasing the laser damage threshold of the film, thereby greatly improving the laser performance of Nd:YAG. Reduced laser threshold (see IEEE Journal of Quantum Electronics, Issue 6, Vol. 34, 1998, p. 1046). In 2002, D. Ehrentraut et al reported growing Yb-doped YAG inside a pure YAG tube using an improved pulling method (Joumal of Crystal Growth No. 242, 2002 p. 375), and this method can also be used to prepare YAG/Nd:YAG/YAG composite laser material in the present invention.

However, the composite laser material prepared by the above prior art has obvious disadvantages: (1) the composite laser material formed by optical coupling agent or direct lamination (optical glue), due to the mismatch between the optical coupling agent and the single crystal, And there is a clear boundary between the pure crystal and the doped crystal, and the light loss is large; (2) The composite single crystal grown by the improved pulling method has poor crystal quality, and there are a lot of defects such as bubbles and inclusions, and the repeatability is low. , has not been practically applied in devices so far.

Invention content:

The problem to be solved in the present invention is to overcome the disadvantages of large optical loss, poor quality and low repeatability in preparing composite laser crystal materials in the prior art, and propose a method for preparing YAG/Nd:YAG/YAG composite laser crystal materials to improve Production efficiency, to meet the needs of the growing high-power laser device manufacturing technology.

Technical solution of the present invention is as follows:

A kind of preparation method of neodymium-doped yttrium aluminum garnet composite laser crystal, it is characterized in that adopt resistance heating liquid-phase epitaxy furnace, make the Nd:YAG single crystal substrate that crystal plane direction is (111) large-area seed crystal, in YAG At the crystallization temperature of the single crystal, YAG single crystals of equal thickness grow on the two interfaces in contact with the saturated solution containing the YAG polycrystalline material and flux.

The structure of the resistance heating liquid phase epitaxy furnace for preparing YAG/Nd:YAG/YAG composite laser crystal mainly includes: a furnace body 1, the lower part of the furnace body 1 is a main furnace body 101, and the upper part of the furnace body 1 is an annealing furnace body 102. In the furnace body 101, a crucible 9 is placed in the center, and the crucible 9 is coaxial with the furnace body 1. In the main furnace body 101, a side heating element 2 is arranged around the opposite crucible 9. The periphery of the side heating element 2 is an insulating layer 11, and the bottom of the crucible 9 There is a heat insulating layer 13 and a bottom support 12 that can adjust the height of the crucible 9. There is an upper side heating element 5 in the annealing furnace 102. The main furnace body 101 is also equipped with a middle temperature measuring thermocouple 3, and the annealing furnace 102 is equipped with an upper temperature measuring thermocouple. A rotating lifting rod 6 extends downward from the center of the upper top cover of the furnace body 1 , the lower end of the rotating lifting rod 6 is a substrate holder 7 , and the rotating lifting rod 6 is coaxial with the furnace body 1 .

The raw material ratio of the saturated solution containing YAG polycrystalline material and flux is as follows:

①The molar ratio of flux PbO to B ₂ O ₃ is PbO:B ₂ O ₃ =(64-95):(36-5)

②The weight percentage of YAG polycrystal and flux is: YAG/(PbO+B ₂ O ₃ )=10wt%-50wt%

The preparation method comprises the following steps:

<1> Weigh the raw materials according to the ratio of the selected YAG polycrystal and flux, mix them well and put them into the crucible 9 and put them into the furnace body 1;

<2> Place the Nd:YAG substrate wafer with crystal plane direction (111) in the substrate fixture, and adjust the rotating lifting rod so that it is on the coaxial position of the crucible;

<3> Raise the temperature to 1050-1250°C at a heating rate of 100°C/Hr, melt the raw material YAG and the flux PbO-B ₂ O ₃ to make it a saturated solution, and keep the temperature at 1050-1250°C for 5 hours after it is completely dissolved;

<4> Gradually lower and rotate the lifting rod to lower the substrate wafer to a place 3-5 mm away from the saturated flux liquid level, and then keep the temperature at the YAG crystallization temperature range of 900-1100 °C for 2-4 hours;

<5> Lower the rotating lifting rod to completely immerse the substrate wafer in the saturated solution at constant temperature. The rotating lifting rod rotates at a speed of 100-250r/min, and adjust the corresponding growth time according to the thickness of the YAG crystal plane of equal thickness required for growth, and the growth time is over. Immediately lift the rotating lifting rod to remove the substrate from the liquid surface;

<6> Annealing, continue to lift the rotating lifting rod, so that the substrate wafer and the YAG single crystal of equal thickness precipitated on it enter the upper heating element section in the annealing furnace, and adjust the power of the upper heating element so that the temperature is 1000 After keeping the temperature at ℃ for 5 hours, the temperature was then lowered to room temperature at a rate of 50 ℃/Hr to complete the preparation of the YAG/Nd:YAG/YAG composite laser material.

However, the above-mentioned preparation method can also be realized by growing YAG crystal twice on a single end surface, and the steps <1>, <2>, <3>, and <4> are the same as above, and the step <5> is to adjust the side of the main furnace body The heating power of the heating element is set to 1000-1200°C indicated by the thermocouple in the middle temperature measurement, and then the temperature is kept constant for 1-2 hours. Rotate at a speed of 100-250r/min, adjust the corresponding growth time according to the thickness of the YAG crystal surface to be grown, when the growth time is over, immediately lift the rotating lifting rod to make the substrate wafer out of the liquid surface;

<6> After annealing, a YAG/Nd:YAG crystal material with a YAG crystal layer at one end is obtained;

<7> Turn the prepared substrate wafer over and put it into the substrate fixture again, and adjust the rotating lifting rod 6 so that it is in the coaxial position of the crucible 9;

<8> After the above steps <3><4><5><6>, the preparation of YAG/Nd:YAG/YAG composite laser crystal material is completed.

Technical effect of the present invention is as follows:

Compared with the prior art, the present invention, on the one hand, compared with the direct lamination of the existing optical coupling agent (optical glue), Nd:YAG and YAG are directly grown together, there is no lattice mismatch, no obvious interface, The optical loss is very small; on the other hand, compared with the existing compound single crystal grown by the improved pulling method, the YAG/Nd:YAG/YAG crystal grown by the liquid phase epitaxy method has no obvious boundary between them, and the crystal integrity is good , good repeatability. The invention is suitable for mass production, can meet the market demand in the manufacture of high-power laser devices, and has good economic benefits.

Description of drawings:

Fig. 1 is a sectional view of a growth device used for preparing YAG/Nd:YAG/YAG composite laser crystal material according to the present invention.

Detailed ways:

Please refer to Fig. 1 first, the structure of the used resistance heating liquid phase epitaxy furnace of the present invention preparation YAG/Nd:YAG/YAG composite laser crystal material method mainly comprises:

Furnace body 1, the lower part of the furnace body 1 is the main furnace body 101, and the upper part of the furnace body 1 is the annealing furnace body 102. In the main furnace body 101, a crucible 9 is placed in the center, and the crucible 9 is coaxial with the furnace body 1. The crucible 9 contains a saturated solution 10 containing YAG polycrystalline material and PbO—B ₂ O ₃ co-solvent. Stretching down from the top of the furnace body 1 is a rotating lifting rod 6 , and a substrate holder 7 is arranged at the lower end of the rotating lifting rod 6 , and a Nd:YAG substrate wafer 8 is placed on the substrate holder 7 and extends into the crucible 9 . The rotating lifting rod 6 is concentric with the furnace body 1 on the central axis. Around the crucible 9 of the main furnace body 101, there is a side heating element 2, a heat insulating layer 11 is arranged on the periphery of the side heating element 2, a heat insulating layer 13 is arranged under the crucible 9 and a base 12 that can adjust the height of the crucible 9 is arranged. Inside the annealing furnace 102 on the upper part of the furnace body 1 is an upper heating element 5 . There is also a middle temperature measuring thermocouple 3 and an upper temperature measuring thermocouple 4 in the device. The annealing furnace 101 in the furnace body 1 of the device of the present invention enables the grown large-area YAG single crystal to eliminate thermal stress in the material, so as to improve the uniformity of the single crystal material and prevent cracking.

The saturated solution of YAG polycrystalline material and flux used in the preparation method of the present invention is prepared by YAG polycrystalline material, fluxing agents lead oxide (PbO) and diboron trioxide (B ₂ O ₃ ) according to the following ratio:

The molar ratio of flux PbO to B ₂ O ₃ is PbO: B ₂ O ₃ = (64-95) mol: (36-5) mol;

The weight percent of YAG polycrystal and flux is: YAAG/(PbO+B ₂ O ₃ )=10wt%-50wt%

The preparation of YAG/Nd:YAG/YAG composite laser crystal material of the present invention mainly contains the following two methods: a method can be called "double-sided impregnation method", that is, grow pure YAG single crystal simultaneously on both ends of Nd:YAG crystal The method; another method can be called "single-side dipping method", that is, first grow a pure YAG single crystal on one end face of the Nd:YAG crystal, and then grow an equal-thickness YAG single crystal on the other corresponding end face. The method of YAG single crystal.

List two examples below and illustrate the preparation method of the present invention:

Embodiment 1: The specific steps of preparing YAG/Nd:YAG/YAG composite laser crystal material by "double-sided dipping method" are as follows:

The selected resistance heating liquid phase epitaxy furnace is as shown in FIG. 1 , and the crucible 9 in the main furnace 101 is a platinum crucible. According to the above-mentioned preparation process step <1>, the polycrystalline raw material YAG and the co-solvent (PbO:B ₂ O ₃ =4mol:1mol) were weighed according to the ratio of YAG/(PbO+B ₂ O ₃ )=0.15 in weight percentage Amount of 1000g in total, mixed evenly and put into a platinum crucible 9 of φ80×80mm; according to the process step <2>, a Nd:YAG substrate wafer 8 with a size of φ30×0.5mm and a crystal plane direction of (111) was placed on the substrate In the bottom fixture 7, put the substrate fixture 7 into the bottom end of the rotating lifting rod 6, adjust the position of the crucible 9 and the substrate wafer 8 to make them coaxial, and both are in the center of the main furnace body 101; according to the above steps <. 3>Heat the furnace body 101 to 1250°C to melt the raw materials and flux to form a saturated solution 10, and after keeping the temperature at 1200°C for 5 hours, gradually lower and rotate the lifting rod 6 according to step <4> to saturate the distance between the substrate wafer 8 The liquid level of the solution 10 is 4mm, and then keep the temperature at 1050°C in the YAG crystallization temperature range for 3 hours; according to the above process step <5>, lower and rotate the lifting rod 6 to completely immerse the substrate wafer 8 in the saturated solution 10, and make the rotating lifting rod 6 Rotate at a speed of 200r/min, grow at a constant temperature at 1050°C for 5 hours, quickly lift off the rotating lifting rod 6 to make the substrate wafer 8 and the single crystal on it leave the liquid surface, and the crystallization is completed; follow the above process steps<6> Perform annealing, pull the grown YAG single crystal together with the substrate wafer 8 to the heating element 5 section of the annealing furnace 102 above the furnace body 1, keep the temperature at 1000°C for 5 hours, and then heat it at a speed of 50°C/Hr The temperature is lowered to room temperature, the annealing is completed, and the YAG/Nd:YAG/YAG composite laser crystal material is prepared.

Embodiment 2: The steps of growing YAG/Nd:YAG/YAG composite laser crystal material by "one-side dipping method" are as follows:

According to the step <1> in the above example 1, the YAG polycrystalline material and the co-solvent (PbO:B ₂ O ₃ =16mol:9mol) are carried out according to the ratio of YAG/(PbO+B ₂ O ₃ )=0.20 in weight percentage Weigh a total of 1000g, repeat the step <2> in the above example 1, heat the furnace body 101 to 1100°C according to <.3> in the above example 1, melt the raw materials and flux to form a saturated solution 10, and heat After 5 hours of constant temperature, according to <4> in the above-mentioned embodiment 1, gradually lower and rotate the lifting rod 6, so that the substrate wafer 8 is 4mm away from the saturated liquid level, and then keep the temperature at 1000°C in the YAG crystallization temperature range for 3 hours, and implement as above In Example 1, <5> lower the rotating lifting rod 6 so that the lower end surface of the substrate wafer 8 is in contact with the liquid surface of the saturated solution 10, and rotate the rotating lifting rod 6 at a speed of 200 r/min. After growing at a constant temperature of 1000 ° C for 5 hours , quickly lifted away from the rotating lifting rod 6, so that the substrate wafer 8 and the single crystal on it were separated from the liquid surface, and the crystallization was completed; annealing was carried out according to the step <6> of the above-mentioned embodiment 1, and the YAG single crystal to be grown was the same as the substrate. The wafer 8 is pulled together into the heating area of the annealing furnace 102 above the furnace body 1, and after being kept at a constant temperature of 900°C for 5 hours, the temperature is lowered to room temperature at a rate of 50°C/Hr, and the annealing is completed; YAG with a single-end YAG crystal layer is obtained /Nd:YAG, turn the prepared substrate wafer 8 together with the single crystal into the substrate fixture 7 again, adjust the rotating lifting rod 6 so that it is in the coaxial position of the crucible 9, and repeat the above <3>～ <6> step (wherein the growth time is the same as the above <5> growth time), obtain YAG single crystal with equal thickness, and complete the preparation of YAG/Nd:YAG/YAG composite laser material.

After the YAG/Nd:YAG/YAG composite laser crystal material grown by the above method is cut, rounded, processed, and coated, it is made into an all-solid-state continuous laser. The laser has good laser performance and low laser threshold. The composite laser crystal has broad application prospects in high-power laser systems and other fields.

Claims (5)

1. neodymium-doped yttrium-aluminum garnet recombination laser crystalline preparation method, it is characterized in that adopting resistive heating rheotaxy stove, crystal plane direction is made the big area seed crystal for the Nd:YAG single crystalline substrate of (111), under the Tc of YAG monocrystalline, with the YAG monocrystalline of growth uniform thickness on two interfaces that the saturated solution that contains YAG polycrystal and fusing assistant contacts.

2. recombination laser crystalline preparation method according to claim 1 is characterized in that the structure of described resistive heating rheotaxy stove mainly comprises:

Body of heater (1), body of heater (1) bottom is main furnace body (101), body of heater (1) top is annealing body of heater (102).In body of heater (101), central authorities are equipped with crucible (9), crucible (9) is coaxial with body of heater (1), relative crucible (9) is provided with side heating element (2) on every side in the main furnace body (101), the periphery of side heating element (2) is thermal insulation layer (11), thermal insulation layer (13) is arranged under the crucible (9) and can regulate crucible (9) collet (12) just, upside heating element (5) is arranged in the annealing furnace (102), main furnace body (101) also is provided with middle temperature thermocouple (3), annealing furnace (102) is provided with temperature thermocouple, under the upper top cover mediad of body of heater (1), be extended with a rotary pulling bar (6), the lower end of this rotary pulling bar (6) is substrate clamp (7), and rotary pulling bar (6) is coaxial with body of heater (1).

3. recombination laser crystalline preparation method according to claim 2, its feature is as follows with the described proportioning raw materials that contains the saturated solution that YAG polycrystal and fusing assistant are arranged:

1. fusing assistant PbO and B ₂O ₃Mol ratio be PbO: B ₂O ₃=(64-95): (36-5)

2. the weight percent of YAG polycrystalline and fusing assistant is: YAG/ (PbO+B ₂O ₃)=10wt%-50wt%

4. recombination laser crystalline preparation method according to claim 3, its feature is comprising the following steps: with this method

＜1〉according to the selected YAG polycrystalline and the proportioning raw materials weighing of fusing assistant, in the crucible (9) of packing into after thorough mixing is even and in the body of heater of packing into (1);

＜2〉crystal plane direction is inserted in the substrate clamp (7) for the substrate wafer (8) of the Nd:YAG of (111), adjusted rotary pulling bar (6), make it to be on the coaxial position of crucible (9);

＜3〉heat-up rate with 100 ℃/Hr is warming up to 1050～1250 ℃, fused raw material YAG and fusing assistant PbO-B ₂O ₃Make it become saturated solution (10), treat all dissolvings after, 1050～1250 ℃ of constant temperature 5 hours;

＜4〉the rotary pulling bar (6) that descends gradually drops to from saturated fusing assistant liquid level 3～5mm place substrate wafer (8), again constant temperature 2～4 hours under 900～1100 ℃ of conditions of YAG crystallization range;

＜5〉decline rotary pulling bar (6) immerses in the homothermic saturated solution (10) substrate wafer (8) fully, rotary pulling bar (6) rotates with 100～250r/min speed, regulate corresponding growth time according to required growth needs YAG crystal face thickness, after growth time finishes, mention rotary pulling bar (6) immediately, make substrate (8) make it break away from liquid level;

＜6〉annealing, rotary pulling bar (6) will be continued to mention, make substrate wafer (8) and precipitating thereof uniform thickness YAG monocrystalline thereon enter interior upside heating element (5) interval of annealing furnace (102), the power of heating element in the adjustment (5) makes its temperature at 1000 ℃ of constant temperature after 5 hours, be cooled to room temperature with 50 ℃/Hr speed then, finish the preparation of YAG/Nd:YAG/YAG composite laser material.

5. according to the described recombination laser crystalline of claim 4 preparation method, 5. its feature is being the heating power of the side heating element (2) of adjusting main furnace body (101) with described step, make middle temperature thermocouple (3) be designated as 1000～1200 ℃, constant temperature 1～2h again, rotary pulling bar (6) then descends, the lower surface of substrate wafer (8) is contacted with homothermic saturated solution (10), this rotary pulling bar (6) is with the speed rotation of 100～250r/min, thickness according to the YAG crystal face of required growth is regulated corresponding growth time, growth time finishes, mention rotary pulling bar (6) immediately, make substrate wafer (8) break away from liquid level;

＜6〉the annealing back obtains single-ended YAG/Nd:YAG crystalline material with YAG crystal layer;

＜7〉will insert once more in the substrate clamp (7) behind prepared substrate wafer (8) turn-over, adjust rotary pulling bar (6) and make it to be on the coaxial position of crucible (9);

＜8〉through step＜3〉＜4＜5＜6 after finish the preparation of YAG/Nd:YAG/YAG recombination laser crystalline material.