Intermediate infrared 2.9 mu m wave band enhanced fluoride laser crystal and preparation method and application thereof

Abstract

The invention belongs to the technical field of laser materials and preparation thereof, and particularly relates to a mid-infrared 2.9 mu m wave band enhanced fluoride laser crystal and a preparation method and application thereof, the chemical composition of the crystal is any one of xHo, yA, zB: Ae1F2 or xHo, yA, zB: Ae1Ae2F4, ho < 3 + > ions are used as active ions, A < 3 + > ions are used as deactivation ions of the Ho < 3 + > ions, and B < 3 + > ions are used as structure regulation ions; 0.5 < = x < = 1.5 at.%, 0.05 < = y < = 0.15 at.%, and 1 < = z < = 30 at.%; the crystal structure belongs to a cubic system, and the space group is Fm-3m (225). Compared with the prior art, the crystal can realize higher luminous intensity in a 2.9 mu m wave band, realizes reversion of fluorescence intensity relative to a 1.9 mu m wave band, has better crystal quality and higher-power intermediate infrared laser output capability, and has the advantages of high gain bandwidth, high gain section, high power, high slope efficiency and the like in an intermediate infrared wave band.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser materials and their preparation, and specifically relates to a mid-infrared 2.9μm band enhanced fluoride laser crystal and its preparation method and application. Background Art

[0002] Fluoride crystals, as an important class of functional materials, have unique physical and chemical properties and have shown significant application advantages in the field of mid-infrared lasers. Their core feature is that they have low maximum phonon energy (e.g., LaF3 is 360cm -1 ), which can significantly inhibit non-radiative transitions and improve luminous efficiency; the wide spectral transmission range covers the ultraviolet to far infrared band (0.19-10μm), especially in the mid-infrared (2-5μm) region, the transmittance is as high as more than 85%; it has excellent chemical stability (corrosion resistance, low moisture absorption) and thermal stability (some crystals have high melting point and high thermal conductivity); at the same time, its lattice structure allows rare earth ions (such as Er 3+ 、Nd 3+ ) high-efficiency doping, by regulating the doping concentration (such as Er 3+ :LaF3) can achieve flexible tuning of laser wavelength in the range of 2.7-2.9μm.

[0003] As a mid-infrared laser gain medium, the core advantages of fluoride crystals are: low phonon energy characteristics greatly reduce the thermal dissipation of excited state energy; wide tuning range covers 2-5μm, supports a variety of activation ions (such as Cr 3+ 、Tm 3+ 、Ho 3+ ) and achieve high power output; its high thermal stability and radiation resistance make it adaptable to extreme environments; its mature preparation process and scalability further promote its application in mid-infrared lasers.

[0004] Patent CN118390161A provides an ion co-doped disordered mixed alkaline earth fluoride laser crystal and its preparation, the chemical formula of the crystal is (A 3+ , B 3+ ):Ca x Sr 1-x F2, where A 3+ Pr 3+ , and praseodymium ion Pr 3+ The doping concentration is 0.3-3%, B 3+ Including yttrium ion Y 3+ , lanthanum ion La 3+ , Lutetium ion 3+ , gadolinium ion Gd 3+ , scandium ion Sc 3+ , B 3+The doping concentration is 1-20at.%, 0<x<1, and the crystal prepared by this invention has a wide fluorescence band. However, due to the complex crystal components, the crystal crystallization performance is reduced, and the growth cost and difficulty are high. 3+ ions and Pr used in CN118390161A 3+ Compared with the conventional pump source, it has better adaptability and more mature research, and Ho 3+ Ions can currently achieve higher output power and slope efficiency in the mid-infrared band.

[0005] Ho 3+ The main reason for choosing fluoride crystal as the matrix for 2.9μm ion laser is that the low maximum phonon energy can significantly suppress the Ho 3+ Non-radiative transition of excited states, extending the upper energy level 5 The fluorescence lifetime of I6 (such as 5.391ms in Ho:LaF3) can improve the particle number inversion efficiency; its wide mid-infrared transmittance (2-5μm band transmittance>85%) is similar to that of Ho 3+ of 5 I6→ 5 The 2.9μm laser spectrum of the I7 transition emission is highly matched, and it also supports ultra-broadband fluorescence emission (such as Ho / Pr:PbF2 can reach 2.8-3.3μm); the fluoride matrix can also be co-doped with Pr 3+ 、Yb 3+ Deactivated ions (such as Ho, Pr: YAP) 5 The I7 energy level lifetime is shortened from 5.391ms to 1.121ms) to regulate the self-termination effect and achieve lifetime reversal; in addition, the high melting point (1400-2500℃) and thermal conductivity of fluoride crystals (such as YAG and YSGG) can withstand high-power pumping (such as LD side-pumping YSGG / Er:YSGG / YSGG composite crystal to achieve 28.02W continuous output).

[0006] However, there are still many technical challenges at this stage: the first is the energy level 5 I6 is susceptible to the influence of the crystal field environment and produces multi-phonon relaxation, which causes rapid energy dissipation, resulting in weaker fluorescence intensity in the 2.9μm band compared to the 1.9μm and 1.2μm bands. At the same time, the incomplete suppression of the self-termination effect leads to the 3+ Doping concentration and co-doping ratio need to be strictly controlled (such as Ho in Ho:YAP 3+ 4at.%), the residual self-termination effect still makes the laser slope efficiency low (such as Ho, Pr: YAP is only 6.3%); Ho 3+The intrinsic absorption peak (~1.15μm) is mismatched with the wavelength of commercial high-power LD pump sources (such as 980nm, 808nm), requiring reliance on Raman fiber lasers or special-band LDs (such as 1150nm), which increases system complexity. The thermal lens effect (such as the significant change of thermal focal length with power in YSGG) and temperature gradient under high-power pumping lead to a decrease in beam quality (M 2 The factor deteriorates to 1.53 / 1.39); during the growth of fluoride crystals (such as LLF, LaF3), volatile components (such as PbF2) are prone to cause defects such as pores and stress cracks, limiting the application of large-sized crystals; multi-ion cooperative luminescence systems (such as Ho / Pr / Yb:PbF2 covering 2.6-3.4μm) need to balance Ho 3+ 、Pr 3+ 、Yb 3+ The energy level coupling and energy transfer efficiency are good, but cross relaxation and excited state absorption will introduce additional losses.

[0007] In summary, fluoride crystals have significant advantages in the field of mid-infrared lasers, such as low phonon energy, wide spectral transmission, and high quantum efficiency when used as gain media. 3+ There are many reasons for choosing it as a matrix. However, it currently faces challenges such as upper level energy dissipation and difficulty in suppressing self-termination effects. Summary of the Invention

[0008] Based on the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a mid-infrared 2.9μm band enhanced fluoride laser crystal and its preparation method and application. Compared with the prior art, the prepared crystal can achieve stronger luminescence intensity in the 2.9μm band, achieving a reversal of the fluorescence intensity relative to the 1.9μm band, while having better crystal quality and higher power mid-infrared laser output capability.

[0009] To achieve the above objectives, the present invention provides the following technical solutions:

[0010] One of the technical solutions of the present application provides a mid-infrared 2.9μm band enhanced fluoride laser crystal, wherein the chemical composition of the crystal is any one of xHo,yA,zB:Ae1F2 or xHo,yA,zB:Ae1Ae2F4;

[0011] Among them, Ho means Ho 3+ ions, as active ions, have a doping concentration range x of 0.5 ≤ x ≤ 1.5 at.%;

[0012] A means A 3+ ions, as deactivating ions, are Pr 3+ 、Eu 3+ or Tb 3+One of the ions, with a doping concentration range y of 0.05≤y≤0.15at.%;

[0013] B means B 3+ ion, as a structure-regulating ion, is a trivalent non-luminescent ion La 3+ 、Y 3+ 、Gd 3+ Sc 3+ 、Lu 3+ 、Al 3+ or Ga 3+ One of the above, wherein the doping concentration range z is 1≤z≤30at.%;

[0014] Ae1 and Ae2 are each independently selected from any one of Ca, Sr and Ba.

[0015] Furthermore, the fluoride laser crystal structure belongs to the cubic system, and its space group is Fm-3m(225).

[0016] Furthermore, Ho 3+ ions as active ions in the mid-infrared band, A 3+ ions as Ho 3+ Deactivation ion of ion, B 3+ Ions act as structure-regulating ions in crystals.

[0017] A second technical solution of the present application provides a method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal, wherein the method adopts a porous graphite crucible temperature gradient method to grow the crystal, and comprises the following steps:

[0018] (1) Using HoF3, Re1F3, Re2F3, Ae1F2, and Ae2F2 as raw materials, calculate the required mass of each raw material according to the chemical formula xHo,yA,zB:Ae1F2 or xHo,yA,zB:Ae1Ae2F4 and weigh them; weigh PbF2;

[0019] (2) After weighing the above raw materials, grind them thoroughly and mix them evenly, then put them into a porous graphite crucible and cover the crucible with a lid;

[0020] (3) Place the crucible in a hot field, start the vacuum pump to evacuate the hot field to a high vacuum, and maintain high vacuum throughout the crystal growth process; then start the power supply and raise the temperature to the target temperature according to the heating program, and maintain the temperature until the raw materials are fully melted and impurities are removed;

[0021] (4) Start a slow cooling process to grow the crystal, ensure that the crystal grows fully and eliminates thermal stress; then perform a fast cooling process to cool to room temperature and take out the crystal.

[0022] Furthermore, the HoF3, Re1F3, Re2F3, Ae1F2 and Ae2F2 raw materials described in step (1) are in the form of single crystal particles or powders; the purity of the single crystal particles or powders is 99.99% (4N) or 99.999% (5N) purity; and accurate weighing is required during weighing, with the weighing error controlled within 0.0001g;

[0023] Furthermore, the PbF2 powder in step (1) accounts for 1-1.5% of the total mass of the raw material, more preferably 1%, and serves as a water and oxygen remover in the raw material.

[0024] Furthermore, the crucible cover strip in step (2) has a vent hole with a diameter of 1 mm in the center to remove impurities during the growth process.

[0025] Furthermore, the thermal field in step (3) is a graphite insulation thermal field; and the high vacuum is to pump the vacuum degree to below 3 Pa and maintain it through a mechanical pump and a molecular pump in sequence.

[0026] Furthermore, the heating program in step (3) is: heating at a rate of 400-500°C / h; the target temperature is 1350-1450°C, and the constant temperature time is 10-20h.

[0027] Furthermore, the cooling rate of the slow cooling process in step (4) is 0.5-2°C / h, and the temperature is reduced to 950-1050°C.

[0028] Furthermore, the cooling rate of the rapid cooling process in step (4) is 25-35°C / h, cooling to room temperature.

[0029] The main reasons for the generation of thermal stress are the temperature difference inside the object and the thermal expansion and contraction characteristics of the material. This application eliminates thermal stress through a slow cooling program to a level that does not affect the normal operation and performance of the object, thereby ensuring the stability and reliability of the object structure.

[0030] The third technical solution of this application provides an application of a mid-infrared 2.9μm band enhanced fluoride laser crystal. The fluoride laser crystal is used as a laser gain medium to obtain mid-infrared laser for space exploration, atmospheric detection, pollution monitoring and biomedicine.

[0031] Compared with the prior art, this application has at least the following improvements and beneficial effects:

[0032] The porous graphite crucible temperature method employed in this method enables high-throughput production of high-quality mid-infrared 2.9μm enhanced fluoride laser crystals. These fluoride laser crystals exhibit high chemical stability, high transmittance, and high quality. Furthermore, they offer advantages in the mid-infrared band, such as high gain bandwidth, high gain cross section, high power, and high slope efficiency. These advantages hold significant promise for applications in environmental monitoring, industrial processing, national defense, and security. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Laue diffraction patterns of the crystals in Example 1, Example 2, and Example 3;

[0034] Figure 2 The transmittance spectra of the crystals in Example 1, Example 2, and Example 3 in the ultraviolet-mid-infrared band are shown;

[0035] Figure 3 This is the normalized fluorescence spectrum of the crystal in the infrared band in this embodiment 1, implementation example 2 and implementation example 3. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0037] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0038] Example 1: The specific implementation steps of growing 1% Ho, 0.1% Pr, 5% Y:CaF2 by temperature gradient method are as follows:

[0039] According to the chemical formula of 1% Ho, 0.1% Pr, 5% Y:CaF2, 150 g of raw materials (the raw materials are HoF3, PrF3, YF3, and CaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water and oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the pressure in the furnace chamber to 1.0×10 -4Pa high vacuum; start the power supply and heat up to 1400℃ at a rate of 500℃ / h and keep the temperature constant for 12h; start slow cooling process at a rate of 1℃ / h to grow crystals, after the temperature drops to 1000℃, start fast cooling process at a rate of 25℃ / h, and take out the crystal after it drops to room temperature. The crystal is 1%Ho, 0.1%Pr, 5%Y:CaF2 (i.e. Figure 2 、 Figure 3 1at.% Ho, 0.1at.% Pr, 5at.% Y CaF2). The Laue diffraction pattern of the crystal is as follows Figure 1 As shown in (a), the Laue diffraction spots of the crystal are clearly visible and arranged in a periodic pattern, and there are no other impurity diffraction spots, which proves that the crystal has a very high crystal quality.

[0040] Example 2: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Y:CaF2 by temperature gradient method are as follows:

[0041] According to the chemical formula of 1% Ho, 0.1% Pr, 10% Y:CaF2, 150 g of raw materials (the raw materials are HoF3, PrF3, YF3, and CaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water and oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the pressure in the furnace chamber to 1.0×10 -4 Pa high vacuum; start the power supply and heat up to 1400℃ at a rate of 500℃ / h and keep the temperature constant for 12h; start slow cooling process at a rate of 1℃ / h to grow crystals, after the temperature drops to 1000℃, start fast cooling process at a rate of 25℃ / h, and take out the crystal after it drops to room temperature. The crystal is 1%Ho, 0.1%Pr, 10%Y:CaF2 (i.e. Figure 2 、 Figure 3 1at.% Ho, 0.1at.% Pr, 10at.% Y CaF2). The Laue diffraction pattern of the crystal is as follows Figure 1 As shown in (b), the Laue diffraction spots of the crystal are clearly visible and arranged in a periodic pattern, and there are no other impurity diffraction spots, which proves that the crystal has a very high crystal quality.

[0042] Example 3: The specific implementation steps of growing 1% Ho, 0.1% Pr, 15% Y:CaF2 by temperature gradient method are as follows:

[0043] According to the chemical formula of 1% Ho, 0.1% Pr, 15% Y:CaF2, 150 g of raw materials (the raw materials are HoF3, PrF3, YF3, and CaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water and oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the pressure in the furnace chamber to 1.0×10 -4 Pa high vacuum; start the power supply and heat up to 1400℃ at a rate of 500℃ / h and keep the temperature constant for 12h; start slow cooling process at a rate of 1℃ / h to grow crystals, after the temperature drops to 1000℃, start fast cooling process at a rate of 25℃ / h, and take out the crystal after it drops to room temperature. The crystal is 1%Ho, 0.1%Pr, 15%Y:CaF2 (i.e. Figure 2 、 Figure 3 1at.% Ho, 0.1at.% Pr, 15at.% Y CaF2). The Laue diffraction pattern of the crystal is as follows Figure 1 As shown in (c), the Laue diffraction spots of the crystal are clearly visible and arranged in a periodic pattern, and there are no other impurity diffraction spots, which proves that the crystal has a very high crystal quality.

[0044] The difference in composition between the crystals provided in Examples 1-3 is the different contents of Y. Their transmittance spectra in the ultraviolet-mid-infrared band are as follows: Figure 2 The normalized fluorescence spectrum in the mid-infrared band is shown in Figure 3 As shown, it can be seen that the crystals are 3+ The characteristic absorption peaks of the ions all have high absorption coefficients, and their fluorescence peak intensities are also high, which is conducive to the crystal's efficient absorption of the pump source's energy and efficient laser operation in the mid-infrared band.

[0045] Example 4: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Lu:CaF2 by temperature gradient method are as follows:

[0046] According to the chemical formula 1% Ho, 0.1% Pr, 10% Lu:CaF2, 150 g of raw materials (the raw materials are HoF3, PrF3, LuF3, CaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the furnace chamber to 1.0×10 -4The device was placed in a high vacuum of 1.5 Pa; the power was started to increase the temperature to 1400°C at a rate of 500°C / h and kept at a constant temperature for 12 hours; a slow cooling process was started at a rate of 1°C / h to allow crystal growth, and after the temperature was reduced to 1000°C, a fast cooling process was started at a rate of 25°C / h, and the crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Pr, and 10% Lu:CaF2.

[0047] Example 5: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Gd:CaF2 by temperature gradient method are as follows:

[0048] According to the chemical formula 1% Ho, 0.1% Pr, 10% Gd:CaF2, 150 g of raw materials (the raw materials are HoF3, PrF3, GdF3, CaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the furnace chamber to 1.0×10 -4 The device was placed in a high vacuum of 1.5 Pa; the power was started to increase the temperature to 1400°C at a rate of 500°C / h and kept at this temperature for 12 hours; a slow cooling process was started at a rate of 1°C / h to allow crystal growth, and after the temperature was reduced to 1000°C, a fast cooling process was started at a rate of 25°C / h, and the crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Pr, and 10% Gd:CaF2.

[0049] Example 6: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Gd: BaF2 by temperature gradient method are as follows:

[0050] According to the chemical formula 1% Ho, 0.1% Pr, 10% Gd:BaF2, 150 g of raw materials (the raw materials are HoF3, PrF3, GdF3, BaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the furnace chamber to 1.0×10 -4 The device was placed in a high vacuum of 1.5 Pa; the power was started to increase the temperature to 1400°C at a rate of 500°C / h and kept at this temperature for 12 hours; a slow cooling process was started at a rate of 1°C / h to allow crystal growth, and after the temperature was reduced to 1000°C, a fast cooling process was started at a rate of 25°C / h, and the crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Pr, and 10% Gd:BaF2.

[0051] Example 7: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Gd: SrF2 by temperature gradient method are as follows:

[0052] According to the chemical formula 1% Ho, 0.1% Pr, 10% Gd: SrF2, 150 g of raw materials (the raw materials are HoF3, PrF3, GdF3, SrF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the furnace chamber to 1.0×10 -4 The device was placed in a high vacuum of 1.5 Pa; the power was started to increase the temperature to 1400°C at a rate of 500°C / h and kept at a constant temperature for 12 hours; a slow cooling process was started at a rate of 1°C / h to allow crystal growth, and after the temperature was reduced to 1000°C, a fast cooling process was started at a rate of 25°C / h, and the crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Pr, and 10% Gd:SrF2.

[0053] Example 8: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Gd:CaSrF4 by temperature gradient method are as follows:

[0054] According to the chemical formula 1% Ho, 0.1% Pr, 10% Gd:CaSrF4, 150 g of raw materials (the raw materials are HoF3, PrF3, GdF3, CaF2, SrF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the furnace chamber to 1.0×10 -4 The device was placed in a high vacuum of 1.5 Pa; the power was started to increase the temperature to 1400°C at a rate of 500°C / h and kept at this temperature for 12 hours; a slow cooling process was started at a rate of 1°C / h to allow crystal growth, and after the temperature was reduced to 1000°C, a fast cooling process was started at a rate of 25°C / h, and the crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Pr, and 10% Gd:CaSrF4.

[0055] Example 9: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Gd:CaBaF4 by temperature gradient method are as follows:

[0056] According to the chemical formula 1% Ho, 0.1% Pr, 10% Gd:CaBaF4, 150 g of raw materials (the raw materials are HoF3, PrF3, GdF3, CaF2, BaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the pressure in the furnace chamber to 1.0×10 -4 The device was placed in a high vacuum of 1.5 Pa; the power was started to increase the temperature to 1400°C at a rate of 500°C / h and kept at this temperature for 12 hours; a slow cooling process was started at a rate of 1°C / h to allow crystal growth, and after the temperature was reduced to 1000°C, a fast cooling process was started at a rate of 25°C / h, and the crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Pr, and 10% Gd:CaBaF4.

[0057] Example 10: The specific implementation steps of growing 1% Ho, 0.1% Pr, 10% Gd: SrBaF4 by temperature gradient method are as follows:

[0058] According to the chemical formula 1% Ho, 0.1% Pr, 10% Gd: SrBaF4, 150 g of raw materials (the raw materials are HoF3, PrF3, GdF3, BaF2, SrF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the furnace chamber to 1.0×10 -4 The temperature was raised to 1400°C at a rate of 500°C / h and kept constant for 12 hours; a slow cooling process was started at a rate of 1°C / h for crystal growth, and after the temperature was lowered to 1000°C, a fast cooling process was started at a rate of 25°C / h. The crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Pr, and 10% Gd:SrBaF4.

[0059] Example 11: The specific implementation steps of growing 1% Ho, 0.1% Eu, 5% Y:CaF2 by temperature gradient method are as follows:

[0060] According to the chemical formula of 1% Ho, 0.1% Eu, 5% Y:CaF2, 150 g of raw materials (the raw materials are HoF3, EuF3, YF3, and CaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water and oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the pressure in the furnace chamber to 1.0×10 -4 Pa; start the power supply and raise the temperature to 1400℃ at a rate of 500℃ / h and keep the temperature constant for 12h; start a slow cooling process at a rate of 1℃ / h to grow crystals, reduce the temperature to 1000℃ and then start a fast cooling process at a rate of 25℃ / h, take out the crystal after cooling to room temperature, which is 1% Ho, 0.1% Eu, 5% Y:CaF2.

[0061] Example 12: The specific implementation steps of growing 1% Ho, 0.1% Tb, 5% Y:CaF2 by temperature gradient method are as follows:

[0062] According to the chemical formula of 1% Ho, 0.1% Tb, 5% Y:CaF2, 150 g of raw materials (the raw materials are HoF3, TbF3, YF3, and CaF2) are accurately weighed, and 1.5 g of PbF2 is weighed as a water and oxygen remover; the weighed raw materials are placed in an agate mortar and ground and stirred until the raw materials are fully mixed; the mixed raw materials are transferred to a porous graphite crucible; the porous graphite crucible is transferred to a single crystal growth furnace, and the pressure in the furnace chamber is first pumped to a low vacuum of 5 Pa using a mechanical pump, and then the molecular pump is turned on to pump the pressure in the furnace chamber to 1.0×10 -4 The device was placed in a high vacuum of 1.5 Pa; the power was started to increase the temperature to 1400°C at a rate of 500°C / h and kept at a constant temperature for 12 hours; a slow cooling process was started at a rate of 1°C / h to allow crystal growth, and after the temperature was reduced to 1000°C, a fast cooling process was started at a rate of 25°C / h, and the crystal was taken out after it cooled to room temperature. The crystal was 1% Ho, 0.1% Tb, and 5% Y:CaF2.

[0063] Comparative Example 1-12 Crystals without Ho Element

[0064] The steps of Comparative Examples 1-12 correspond to Reference Examples 1-12, respectively, with the difference being that the crystal composition does not contain the Ho element. For example, the crystal structure formula in Comparative Example 1 is 0.1% Pr, 5% Y:CaF2, the crystal structure formula in Comparative Example 2 is 0.1% Pr, 10% Y:CaF2, the crystal structure formula in Comparative Example 3 is 0.1% Pr, 15% Y:CaF2, and so on.

[0065] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A mid-infrared 2.9μm band enhanced fluoride laser crystal, characterized in that: The chemical composition of the crystal is any one of xHo,yA,zB:Ae1F2 or xHo,yA,zB:Ae1Ae2F4; Among them, Ho means Ho 3+ ions, as active ions, with a doping concentration range x of 0.5 ≤ x ≤ 1.5 at.%; A means A 3+ ions, as deactivating ions, are Pr 3+ 、Eu 3+ or Tb 3+ One of the ions, with a doping concentration range y of 0.05≤y≤0.15at.%; B means B 3+ ion, as a structure-regulating ion, is a trivalent non-luminescent ion La 3+ 、Y 3+ 、Gd 3+ Sc 3+ 、Lu 3+ 、Al 3+ or Ga 3+ One of the above, wherein the doping concentration range z is 1≤z≤30at.%; Ae1 and Ae2 are each independently selected from any one of Ca, Sr and Ba.

2. The mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 1, characterized in that: The fluoride laser crystal structure belongs to the cubic system, and its space group is Fm-3m (225).

3. The method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 1, characterized in that: The preparation method adopts a porous graphite crucible temperature gradient method to grow crystals, comprising the following steps: (1) Using HoF3, AF3, BF3, Ae1F2, and Ae2F2 as raw materials, calculate the required mass of each raw material according to the chemical formula xHo,yA,zB:Ae1F2 or xHo,yA,zB:Ae1Ae2F4 and weigh them; weigh the deoxidizer PbF2; (2) After weighing the above raw materials, grind them thoroughly and mix them evenly, then put them into a crucible and cover the crucible with a lid; (3) Place the crucible in a hot field, start the vacuum pump to evacuate the hot field to a high vacuum, and maintain high vacuum throughout the crystal growth process; then raise the temperature to the target temperature according to the heating program, and maintain the temperature until the raw materials are fully melted and impurities are removed; (4) Start a slow cooling process to grow the crystal, ensure that the crystal grows fully and eliminates thermal stress; then perform a fast cooling process to cool to room temperature and take out the crystal.

4. The method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 3, characterized in that: The HoF3, AF3, BF3, Ae1F2 and Ae2F2 raw materials described in step (1) are in the form of single crystal particles or powders; the purity of the single crystal particles or powders is 4N or 5N purity; the PbF2 powder described in step (1) accounts for 1-1.5% of the total mass of the raw materials.

5. The method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 3, characterized in that: The crucible cover strip described in step (2) has a vent hole with a diameter of 1 mm in the center.

6. The method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 3, characterized in that: The high vacuum in step (3) is: drawing the vacuum degree to below 3 Pa and maintaining it.

7. The method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 3, characterized in that: The heating program of step (3) is: heating at a rate of 400-500°C / h; the target temperature is 1350-1450°C, and the constant temperature time is 10-20h.

8. The method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 3, characterized in that: The cooling rate of the slow cooling process in step (4) is 0.5-2°C / h, and the temperature is reduced to 950-1050°C.

9. The method for preparing a mid-infrared 2.9 μm band enhanced fluoride laser crystal according to claim 3, characterized in that: The cooling rate of the rapid cooling process in step (4) is 25-35°C / h, and the temperature is cooled to room temperature.

10. Use of a mid-infrared 2.9 μm band enhanced fluoride laser crystal in the preparation of a laser gain medium according to claim 1, characterized in that: The fluoride laser crystal is used to obtain mid-infrared laser.

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