A thulium ion-doped lutetium yttrium garnet single crystal fiber and a method for manufacturing the same

Abstract

A thulium ion doped lutetium aluminum scandium garnet single crystal fiber has a chemical formula of Lu 3‑x Tm x Al 5‑y Sc y O 12 , wherein x is Tm 3+ doped Lu 3+ site is 0.09, and y is Sc 3+ doped Al 3+ site is 0.09, and 0.5<=y<=1. The single crystal fiber belongs to a cubic system, has a space group of Ia3d, and has a cell parameter of a=b=c=1.1941 nm. A preparation method comprises the following steps: taking Lu2O3, Tm2O3, Al2O3 and Sc2O3 as initial raw materials, grinding, primary calcining, ball milling, cold isostatic pressing into a block, and secondary calcining; and a growth method is a micro-pulling-down method, and a growth atmosphere is high-purity nitrogen. The single crystal fiber with high quality can be rapidly and batch-grown, and the grown crystal has the advantages of high thermal conductivity, high chemical stability, and a wide gain bandwidth in a mid-infrared wave band.

Description

Technical Field

[0001] This invention belongs to the field of laser materials and their preparation technology, specifically relating to a thulium ion-doped lutetium aluminum scandium garnet single crystal optical fiber and its preparation method. Background Technology

[0002] Laser technology is considered an indispensable tool for human survival and development in an intelligent society. With the increasing informatization of society, the demand for lasers in specific wavelengths is becoming increasingly strong in modern industrial society. Among them, mid-infrared lasers have attracted widespread attention due to their advantages such as strong penetration of smoke, wavelength falling within the "molecular fingerprint region" of the infrared spectrum, and strong absorption band of water, making their application in fields such as medicine, military, and communication detection highly sought after.

[0003] Currently, there are three main methods for achieving near-mid-infrared laser output: activated ion-doped lasers, optical parametric technology, and semiconductor lasers. However, optical parametric technology and semiconductor lasers have drawbacks such as high cost and low peak power, respectively. Therefore, activated ion-doped lasers based on rare-earth ion-doped crystals have become a focus of attention. Currently, Tm... 3+ Ho 3+ Er 3+ Dy 3+ Plasma. Among them, thulium-doped laser materials have the following advantages: (1) Mid-infrared band Tm 3+ As a four-level system, it is easy to achieve population inversion, has a low laser threshold, and Tm 3+ There is no self-absorption phenomenon in this band; (2) Tm at 800nm 3+ It has a strong absorption peak and a large absorption cross section, which can be matched with the wavelengths of commonly used pump sources such as 808nm and 793nm; (3) It has a wide gain bandwidth at 1.5μm, which makes Tm-doped 3+ Laser materials have good tunability, enabling ultrafast laser output.

[0004] Tm 3+ Doping has already been applied to oxides such as YAG, LuAG, LiYF4 (YLF), BaYb2F8, and KY3F. 10Mid-infrared laser output has been achieved in fluoride crystals and ZBLAN fluoride glasses. In 1983, 1.48 μm laser output was achieved in Tm:BaYb2F8 crystal; in 1989, 2.3 μm laser output was achieved in Tm:ZBLAN; and in 1994, 2.3 μm laser output with an output power of 200 mW and a slope efficiency of 15% was also achieved in Tm:YLF crystal. Lutetium aluminum scandium garnet single-crystal fiber belongs to the cubic crystal system, is relatively easy to grow, and has advantages such as high thermal conductivity, high chemical stability, and wide gain bandwidth in the mid-infrared band. Currently, there are no literature reports on thulium ion doping in lutetium aluminum scandium garnet. Summary of the Invention

[0005] The purpose of this invention is to provide a thulium ion-doped lutetium aluminum scandium garnet single crystal optical fiber and its preparation method. This method can rapidly grow high-quality single crystal optical fibers in batches. The grown crystals have advantages such as high thermal conductivity, high chemical stability, and wide gain bandwidth in the mid-infrared band, and have broad application prospects in the fields of medicine, military, communication and detection.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a thulium ion-doped lutetium aluminum scandium garnet single-crystal optical fiber, with the chemical formula Lu. 3-x Tm x Al 5-y Sc y O 12 In the formula, x is Tm 3+ Lu-doped 3+ The percentage of moles in a given position, y is Sc 3+ Doped Al 3+ The percentage of moles in a given position, x = 0.09, 0.5 ≤ y ≤ 1.

[0007] Preferably, the single-crystal optical fiber belongs to the cubic crystal system, with space group Ia3d and cell parameters a=b=c=1.1941nm.

[0008] The present invention also provides a method for preparing the above-mentioned thulium ion-doped lutetium aluminum scandium garnet single crystal optical fiber, comprising the following steps:

[0009] S1. Using Lu2O3 powder, Tm2O3 powder, Al2O3 powder, and Sc2O3 powder, all with a purity of 99.999%, as raw materials, according to the chemical formula Lu... 3-x Tm x Al 5-y Sc y O 12 The stoichiometric ratio of the corresponding elements in the formula is used to accurately weigh each raw material, where x is Tm. 3+ Lu-doped 3+ The percentage of moles in a given position, y is Sc 3+Doped Al 3+ The percentage of moles in a given position, x = 0.09, 0.5 ≤ y ≤ 1;

[0010] S2. Place the weighed raw materials into an agate mortar and grind and stir until the raw materials are fully mixed and uniform; transfer the uniformly mixed raw materials into an alumina crucible and then place it into a muffle furnace for the first high-temperature sintering;

[0011] S3. Place the sintered raw material into a ball mill for ball milling, then place it into a plastic bag for sealing, and cold isostatically press it into blocks; after loading the block raw material into an alumina crucible, place it into a muffle furnace for a second high-temperature sintering;

[0012] S4. After sintering twice, the raw material is placed in an iridium crucible and loaded into a micro pull-down furnace for crystal growth. First, a mechanical pump is used to evacuate the gas pressure in the furnace cavity to a low vacuum, then a molecular pump is turned on to evacuate the furnace cavity to a high vacuum. Then, a high-purity inert protective gas is introduced into the furnace cavity and a flowing atmosphere is maintained.

[0013] S5. After the furnace cavity is heated, the raw materials are fully melted; the seed crystal rod is slowly raised to ensure that the seed crystal is in full contact with the lower opening of the iridium crucible; the seed crystal rod is controlled to descend slowly and uniformly to start crystal growth, and the growth rate is slowly increased to 0.2-0.5 mm / min.

[0014] S6. After the crystal growth is complete, cool down to room temperature and then open the furnace door to cut the single-crystal fiber from the crystal rod to obtain thulium ion-doped lutetium aluminum scandium garnet single-crystal fiber.

[0015] Preferably, in step S2, the first high-temperature sintering temperature is 1000-1300℃ and the sintering time is 24h; in step (3), the second high-temperature sintering temperature is 1400-1700℃ and the sintering time is 30h.

[0016] Preferably, in step S3, the sintered raw material is placed in a ball mill and ball-milled until the average particle size of the raw material is 1 μm.

[0017] Preferably, in step S3, the cold isostatic pressure is 150 MPa and the holding time is 300 s.

[0018] Preferably, in step S4, the vacuum degree after evacuation by the mechanical pump is ≤10 Pa, and the vacuum degree after evacuation by the molecular pump is ≤1.0 × 10 Pa. -4 Pa; the inert protective gas introduced is nitrogen or argon with a purity of 99.999%, and the pressure inside the furnace cavity after filling is 1.01 atmospheres, and the gas flow rate of the flowing atmosphere is 15 ml / min.

[0019] Preferably, in step S5, the furnace cavity is heated to 2000℃-2100℃ over 2.5 hours and kept at that temperature for 30 minutes to allow the raw materials to fully melt.

[0020] Preferably, in step S5, the contact time between the seed crystal and the lower opening of the iridium crucible is 15 min; the initial seed crystal rod growth rate is 0.05 mm / min, and the growth rate is increased to 0.2-0.5 mm / min every 15 min by 0.05 mm / min.

[0021] Compared with existing technologies, this invention dops rare earth ions Tm into a lutetium aluminum scandium garnet matrix. 3+ Tm 3+ It is a luminescent ion; the Sc element content in the matrix will affect Tm. 3+ The luminescence of Tm is affected; Tm is grown using a micro-pull-down method. 3+ This invention relates to doped lutetium aluminum scandium garnet single-crystal optical fiber. Firstly, the temperature field employed in this invention has a suitable temperature gradient, which can effectively and quickly eliminate internal thermal stress in the single-crystal fiber, preventing cracking and ensuring the quality of the fiber, thus facilitating high-quality fiber growth. Furthermore, the micro-pull-down method for single-crystal fiber growth allows for rapid growth of high-quality fibers. Secondly, the selected lutetium aluminum scandium garnet single-crystal fiber belongs to the cubic crystal system, making its growth relatively easy, and it possesses advantages such as high thermal conductivity, high chemical stability, and a wide gain bandwidth in the mid-infrared band. Additionally, the Al in lutetium aluminum scandium garnet... 3+ and Sc 3+ The disordered distribution of tetrahedral and octahedral lattice sites in the crystal structure results in a disordered structure in lutetium aluminum scandium garnet, which in turn leads to the doping of Tm. 3+ The emission spectrum exhibits non-uniform broadening, which is beneficial for tunable and ultrafast laser operation. The crystal material prepared by this invention can achieve efficient 2μm band laser output, and can be applied in fields such as surgery, atmospheric sensing, lidar, and optical communication. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the crystal growth furnace and crystal growth process in this invention;

[0023] Figure 2 The X-ray diffraction patterns are those of the samples prepared in Examples 1-2, respectively.

[0024] Figure 3 The sample prepared in Example 1 was subjected to 808nm light excitation. 3 F4→ 3 Fluorescence spectrum corresponding to the H6 energy level transition;

[0025] Figure 4 The sample prepared in Example 2 was subjected to 808nm light excitation. 3 F4→ 3Fluorescence spectrum corresponding to the H6 energy level transition;

[0026] Figure 5 The sample prepared in Example 1 was subjected to 808nm light excitation. 3 F4→ 3 Fluorescence lifetime diagram corresponding to the H6 energy level transition;

[0027] Figure 6 The sample prepared in Example 2 was subjected to 808nm light excitation. 3 F4→ 3 Fluorescence lifetime diagram corresponding to the H6 energy level transition;

[0028] Figure 1 In the middle: 1. Corundum cover plate, 2. Induction heating coil, 3. Corundum insulation tube, 4. Iridium crucible, 5. Post-heater, 6. Corundum gasket, 7. Grown crystal, 8. Seed crystal, 9. Seed crystal rod, 10. Quartz tube. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1: Micro-pull-down growth of Lu 2.91 Tm 0.09 Al 4.5 Sc 0.5 O 12 The specific implementation steps are as follows:

[0031] S1. Using Lu2O3 powder, Tm2O3 powder, Al2O3 powder, and Sc2O3 powder, all with a purity of 99.999%, as raw materials, according to the chemical formula Lu... 2.91 Tm 0.09 Al 4.5 Sc 0.5 O 12 The stoichiometric ratios of the corresponding elements in the formula shall be accurately measured as follows: 6.731g of Lu2O3 powder, 0.202g of Tm2O3 powder, 2.667g of Al2O3 powder and 0.401g of Sc2O3 powder, with a weighing error not exceeding 0.001g.

[0032] S2. Place the weighed raw materials into an agate mortar and grind and stir until the raw materials are fully mixed and uniform; transfer the uniformly mixed raw materials into an alumina crucible and then place it into a muffle furnace for the first high-temperature sintering; the first high-temperature sintering temperature is 1300℃ and the sintering time is 24h.

[0033] S3. Place the sintered raw material into a ball mill and ball mill for 4 hours. Then place it into a plastic bag and seal it. Press it into blocks by cold isostatic pressing. The cold isostatic pressing pressure is 150 MPa and the holding time is 300 s. After loading the block raw material into an alumina crucible, place it into a muffle furnace for a second high-temperature sintering. The second high-temperature sintering temperature is 1400℃ and the sintering time is 30 hours.

[0034] S4. After sintering twice, the raw material is placed in iridium crucible 4 and then loaded into a micro-pull-down furnace for crystal growth. First, a mechanical pump is used to evacuate the furnace cavity to a low vacuum of 10 Pa, and then a molecular pump is turned on to evacuate the furnace cavity to 1.0 × 10⁻⁶ Pa. -4 A high vacuum of Pa was then introduced into the furnace cavity, and argon gas with a purity of 99.999% was introduced until the pressure inside the furnace cavity reached 1.01 atmospheres. The gas flow rate was maintained at 15 ml / min.

[0035] S5. The iridium crucible 4 and the post heater 5 are heated in the furnace cavity by induction heating coil 2. The temperature is raised to 2000℃ in 2.5 hours and held at a constant temperature for 30 minutes to fully melt the raw materials. The seed crystal rod 9 is slowly raised to make full contact between the seed crystal 8 and the lower opening of the iridium crucible 4 for 15 minutes. The seed crystal rod 9 is controlled to descend slowly and uniformly to start crystal growth. The initial crystal growth rate of the seed crystal rod 9 is 0.05 mm / min. Every 15 minutes, the growth rate is slowly increased by 0.05 mm / min to 0.2 mm / min. During the growth process, the corundum cover plate 1, corundum insulation tube 3, corundum gasket 6 and quartz tube 10 are used for heat preservation.

[0036] S6. After the crystal growth is completed, the temperature is lowered to room temperature for 3 hours and then cooled. The furnace door is then opened, and the single-crystal fiber is cut from the seed crystal 8 to obtain the grown crystal 7, which is a thulium ion-doped lutetium aluminum scandium garnet single-crystal fiber.

[0037] The growth furnace and crystal growth diagram used in this embodiment are shown below. Figure 1 As shown.

[0038] Combination Figure 1 , Figure 2 , Figure 3 and Figure 5 For the growth of Lu 2.91 Tm 0.09 Al 4.5 Sc 0.5 O 12 The crystal structure and spectral properties of the single-crystal optical fiber were analyzed. The XRD pattern of this single-crystal optical fiber is similar to that of Lu3Al5O4. 12 The standard card shows a high degree of agreement, with no secondary phase peaks, indicating that Tm 3+ It is a good replacement for Lu 3+It does not change the internal structure of the crystal, and no impurity phase appears during the growth process. At the same time, the emission peak is in the 2μm band and the fluorescence lifetime is 6.37ms, which has a wide emission bandwidth and long fluorescence lifetime, which is conducive to realizing 2μm band laser output.

[0039] Example 2: Micro-pull-down growth of Lu 2.91 Tm 0.09 Al4ScO 12 The specific implementation steps are as follows:

[0040] S1. Using Lu2O3 powder, Tm2O3 powder, Al2O3 powder, and Sc2O3 powder, all with a purity of 99.999%, as raw materials, according to the chemical formula Lu... 2.91 Tm 0.09 Al4ScO 12 The stoichiometric ratios of the corresponding elements in the formula are accurately measured as follows: 6.661g of Lu2O3 powder, 0.200g of Tm2O3 powder, 2.346g of Al2O3 powder, and 0.793g of Sc2O3 powder, with a weighing error not exceeding 0.001g.

[0041] S2. Place the weighed raw materials into an agate mortar and grind and stir until the raw materials are fully mixed and uniform; transfer the uniformly mixed raw materials into an alumina crucible and then place it into a muffle furnace for the first high-temperature sintering; the first high-temperature sintering temperature is 1000℃ and the sintering time is 24h.

[0042] S3. Place the sintered raw material into a ball mill and ball mill for 4 hours. Then place it into a plastic bag and seal it. Press it into blocks using cold isostatic pressing. The cold isostatic pressing pressure is 150 MPa and the holding time is 300 s. After loading the block raw material into an alumina crucible, place it into a muffle furnace for a second high-temperature sintering. The second high-temperature sintering temperature is 1500℃ and the sintering time is 30 hours.

[0043] S4. After sintering twice, the raw material is placed in iridium crucible 4 and then loaded into a micro-pull-down furnace for crystal growth. First, a mechanical pump is used to evacuate the furnace cavity to a low vacuum of 10 Pa, and then a molecular pump is turned on to evacuate the furnace cavity to 1.0 × 10⁻⁶ Pa. -4 A high vacuum of Pa was then introduced into the furnace cavity, and argon gas with a purity of 99.999% was introduced until the pressure inside the furnace cavity reached 1.01 atmospheres. The gas flow rate was maintained at 15 ml / min.

[0044] S5. The iridium crucible 4 and the post heater 5 are heated in the furnace cavity by induction heating coil 2. The temperature is raised to 2000℃ in 2.5 hours and held at a constant temperature for 30 minutes to fully melt the raw materials. The seed crystal rod 9 is slowly raised to make full contact between the seed crystal 8 and the lower opening of the iridium crucible 4 for 15 minutes. The seed crystal rod 9 is controlled to descend slowly and uniformly to start crystal growth. The initial crystal growth rate of the seed crystal rod 9 is 0.05 mm / min. Every 15 minutes, the growth rate is slowly increased by 0.05 mm / min to 0.2 mm / min. During the growth process, the corundum cover plate 1, corundum insulation tube 3, corundum gasket 6 and quartz tube 10 are used for heat preservation.

[0045] S6. After the crystal growth is completed, the temperature is lowered to room temperature for 3 hours and then cooled. The furnace door is then opened, and the single-crystal fiber is cut off from the seed crystal 8 to obtain the grown crystal 7, which is a thulium ion-doped lutetium aluminum scandium garnet single-crystal fiber.

[0046] The growth furnace and crystal growth diagram used in this embodiment are shown below. Figure 1 As shown.

[0047] Combination Figure 1 , Figure 2 , Figure 4 and Figure 6 For the growth of Lu 2.91 Tm 0.09 Al4ScO 12 The crystal structure and spectral properties of the single-crystal optical fiber were analyzed. The XRD pattern of this single-crystal optical fiber is similar to that of Lu3Al5O4. 12 The standard card shows a high degree of agreement, with no secondary phase peaks, indicating that Tm 3+ It is a good replacement for Lu 3+ It does not change the internal structure of the crystal, and no impurity phase appears during the growth process. At the same time, the emission peak is in the 2μm band and the fluorescence lifetime is 6.87ms, which has a wide emission bandwidth and long fluorescence lifetime, which is conducive to realizing 2μm band laser output.

Claims

1. A thulium ion-doped lutetium aluminum scandium garnet single-crystal optical fiber, characterized in that, Its chemical formula is Lu 3-x Tm x Al 5- y Sc y O 12 In the formula, x is Tm 3+ Lu-doped 3+ The mole fraction of s, y is Sc 3+ Doped Al 3+ The mole fraction of the place value, x=0.09, 0.5≤y≤1.

2. The thulium ion-doped lutetium aluminum scandium garnet single-crystal optical fiber according to claim 1, characterized in that, The single-crystal optical fiber belongs to the cubic crystal system, with space group Ia3d and cell parameters a=b=c=1.1941nm.

3. A method for preparing a thulium ion-doped lutetium aluminum scandium garnet single-crystal optical fiber as described in claim 1 or 2, characterized in that, Crystal growth using the micro-pull-down method includes the following steps: S1. Using Lu2O3 powder, Tm2O3 powder, Al2O3 powder, and Sc2O3 powder, all with a purity of 99.999%, as raw materials, according to the chemical formula Lu... 3-x Tm x Al 5-y Sc y O 12 The stoichiometric ratio of the corresponding elements in the formula is used to accurately weigh each raw material, where x is Tm. 3+ Lu-doped 3+ The mole fraction of s, y is Sc 3+ Doped Al 3+ The mole fraction of a given mole, x = 0.09, 0.5 ≤ y ≤ 1; S2. Place the weighed raw materials into an agate mortar and grind and stir until the raw materials are fully mixed and uniform; transfer the uniformly mixed raw materials into an alumina crucible and then place it into a muffle furnace for the first high-temperature sintering; the first high-temperature sintering temperature is 1000-1300℃ and the sintering time is 24h. S3. Place the sintered raw material into a ball mill for ball milling, then place it into a plastic bag for sealing, and cold isostatically press it into blocks; after loading the block raw material into an alumina crucible, place it into a muffle furnace for a second high-temperature sintering; the second high-temperature sintering temperature is 1400-1700℃, and the sintering time is 30h. S4. After sintering twice, the raw material is placed in an iridium crucible and loaded into a micro pull-down furnace for crystal growth. First, a mechanical pump is used to evacuate the gas pressure in the furnace cavity to a low vacuum, then a molecular pump is turned on to evacuate the furnace cavity to a high vacuum. Then, a high-purity inert protective gas is introduced into the furnace cavity and a flowing atmosphere is maintained. S5. After the furnace cavity is heated, the raw materials are fully melted. The seed crystal rod is slowly raised to ensure full contact between the seed crystal and the lower opening of the iridium crucible. The seed crystal rod is controlled to descend slowly and uniformly to begin crystal growth, and the growth rate is slowly increased to 0.2-0.5 mm / min. The contact time between the seed crystal and the lower opening of the iridium crucible is 15 min. The initial seed crystal rod crystal growth rate is 0.05 mm / min, and the growth rate is increased to 0.2-0.5 mm / min every 15 min by 0.05 mm / min. S6. After the crystal growth is complete, cool down to room temperature and then open the furnace door to cut the single-crystal fiber from the crystal rod to obtain thulium ion-doped lutetium aluminum scandium garnet single-crystal fiber.

4. The method for preparing a thulium ion-doped lutetium aluminum scandium garnet single crystal optical fiber according to claim 3, characterized in that, In step S3, the sintered raw material is placed in a ball mill and ball-milled until the average particle size of the raw material is 1 μm.

5. The method for preparing a thulium ion-doped lutetium aluminum scandium garnet single crystal optical fiber according to claim 3, characterized in that, In step S3, the cold isostatic pressure is 150 MPa, and the holding time is 300 s.

6. The method for preparing a thulium ion-doped lutetium aluminum scandium garnet single crystal optical fiber according to claim 3, characterized in that, In step S4, the vacuum level after evacuation by the mechanical pump is ≤10 Pa, and the vacuum level after evacuation by the molecular pump is ≤1.0×10 Pa. -4 Pa; the inert protective gas introduced is nitrogen or argon with a purity of 99.999%, and the pressure inside the furnace cavity after filling is 1.01 atmospheres, and the gas flow rate of the flowing atmosphere is 15 ml / min.

7. The method for preparing a thulium ion-doped lutetium aluminum scandium garnet single crystal optical fiber according to claim 3, characterized in that, In step S5, the furnace cavity is heated to 2000℃-2100℃ over 2.5 hours and kept at that temperature for 30 minutes to allow the raw materials to fully melt.

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