A thulium-doped yttrium calcium fluoride composite near-infrared waveband laser crystal and a preparation method thereof

Abstract

The application relates to a new thulium-doped fluoroyttrium calcium composite near-mid-infrared waveband laser crystal and a preparation method thereof. x Y y Ca 1‑x‑y F2, wherein 0.001<=x<=0.01, 0.005<=y<=0.12; the preparation method comprises the following steps: mixing TmF3, YF3 and CaF2, keeping at 1500 DEG C for 12 hours in a protective gas atmosphere, and slowly cooling to 1000-1200 DEG C at a rate of 1-3 DEG C / h to obtain the crystal. Compared with the prior art, the prepared near-mid-infrared waveband laser crystal can realize higher output power than existing fluorides, and has good application potential in aspects of 1.5 mu m and 2.3 mu m laser output laser materials and the like.

Description

Technical Field

[0001] This invention belongs to the field of laser materials technology, and relates to a near-mid-infrared laser crystal and its preparation method, particularly to a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal and its preparation method. Background Technology

[0002] With the advancement of information technology, the demand for lasers in specific wavelength bands is increasing. This situation has prompted research in related fields to shift towards high-performance lasers in new wavelength bands. Among them, near-infrared lasers have received widespread attention due to their broad applications in daily life. The infrared spectrum is generally divided into three regions: near-infrared (0.75–2.5 μm), mid-infrared (2.5–25 μm), and far-infrared (25–300 μm). Due to differences in application requirements, different fields have different definitions for the range of infrared wavelengths. In the laser field, the near-infrared wavelength range is generally defined as 1–5 μm. Near-infrared lasers have important applications in medicine, military, communication, and detection. Currently, there are three main methods for realizing near-infrared lasers: 1) Activated ion-doped lasers, which utilize the transitions in specific near-infrared bands of activated ions to prepare ion-doped laser materials such as crystals, glasses, ceramics, and optical fibers. 2) Optical parametric technology utilizes nonlinear techniques such as optical parametric oscillation, optical parametric amplification, difference frequency conversion, and sum frequency conversion to tune mature short-wavelength lasers using nonlinear materials, thereby obtaining mid-infrared lasers. 3) Semiconductor lasers achieve population inversion between the conduction and valence bands through excitation. Stimulated emission occurs when electrons at the bottom of the conduction band recombine with holes at the top of the valence band. Commonly used semiconductor lasers include InGaAsSb and AlGaAsS. While optical parametric technology can utilize existing lasers, it is costly and inconvenient for application. Semiconductor lasers also suffer from low power and poor beam quality. In contrast, doped activated ion solid-state or fiber lasers, especially rare-earth ion doped lasers, are not only small and easy to use, but also stable in operation, with high output beam quality and high efficiency, attracting increasing attention from researchers in modern society. Summary of the Invention

[0003] The purpose of this invention is to provide a thulium-doped yttrium-calcium composite near-infrared laser crystal with low matrix phonon energy, large interatomic spacing, and high output power, and its preparation method.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A novel thulium-fluorine-yttrium-calcium composite near-mid-infrared laser crystal, with the chemical formula Tm x Y y Ca 1-x-yF2, where 0.001≤x≤0.01, 0.005≤y≤0.12. Preferably, x=0.005, 0.01≤y≤0.08, the space group of the crystal is Fm-3m(225), belonging to the cubic crystal system, and the cell parameters are... Further preferably, the cell parameters are as follows:

[0006] A method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal includes: mixing TmF3, YF3, and CaF2, holding the mixture at 1400-1700℃ for 10-15 hours in a protective gas atmosphere, and then slowly cooling it to 1000-1200℃ at a rate of 1-3℃ / h to obtain the crystal.

[0007] Furthermore, the TmF3, YF3, and CaF2 mentioned are corresponding single crystal particles or powders.

[0008] Furthermore, the mixing process of TmF3, YF3, and CaF2 involves grinding for 40-60 minutes.

[0009] Furthermore, PbF2 is added before calcination, and the amount added is 5% of the total mass of TmF3, YF3, and CaF2.

[0010] Furthermore, during the calcination process, the heating rate is 200-300℃ / h, and the cooling rate is 50-60℃ / h.

[0011] Furthermore, the protective gas is at least one of argon, CF4, or HF.

[0012] Furthermore, during the calcination process, the calcination vessel for TmF3, YF3, and CaF2 is a porous graphite crucible.

[0013] Currently, the rare earth ions that produce laser output in the near-mid-infrared range of 1.5-3.5 μm mainly include thulium (Tm), holmium (Ho), erbium (Er), and dysprosium (Dy). Among these, Tm... 3+ The ion absorption energies at 1.5 μm and 2.3 μm match those of commonly used pumps, and the wide gain bandwidth enables the laser to be tunable. Tm 3+ Ions are composed of Tm atoms (outer electron distribution 4f) 13 6s 2 The 4f electron shell loses one electron, and the 6s electron shell loses two electrons to form Tm. 3+ The main absorption band of the ion corresponds to 3 H6→ 3The H4 transition, with a wavelength around 800 nm, closely matches the emission wavelength of GaAsAl laser diodes. Therefore, high-power GaAsAl lasers can be used as Tm... 3+ Ion-doped laser dielectric pump source. Tm 3+ The main luminescence of ions in the near-mid-infrared band includes transitions at 1.5 μm, 2 μm, and 2.3 μm, respectively. 3 H4→ 3 F4 3 F4→ 3 H6 3 H4→ 3 H5.

[0014] In Tm 3+ In ions, 3 H4 and 3 The energy level spacing of F4 and 3 F4 and 3 The energy level spacing of H6 is relatively close, making it highly susceptible to cross-relaxation (CR). The pump light then... 3 H6 population pumping to 3 The H4 energy level, through a cross-relaxation process 3 H4(Tm 3+ )+ 3 H6(Tm 3+ → 3 F4(Tm 3+ )+ 3 F4(Tm 3+ ),exist 3 The F4 energy level receives twice the number of particles, and then through 3 F4→ 3 The H6 emission transition generates a 2μm laser. Through a cross-relaxation process, the theoretical quantum efficiency of the 2μm laser can reach 200%, meaning that one pump photon can generate two 2μm laser photons. Therefore, Tm 3+ Ion-doped laser media have achieved high output power and high slope efficiency lasers in the 2μm band, and have been put into practical use. In 2007, Tm-doped laser media... 3+ A 1.9 μm continuous-wave laser output with an output power of 64 W and a slope efficiency of 68% was obtained in a Ge fiber containing ions. By 2010, Tm 3+ Ion-doped fiber lasers have achieved kilowatt-level output power.

[0015] Although cross-relaxation is very beneficial to Tm 3+ The laser output at 2μm ion emission has the opposite effect on 1.5μm and 2.3μm emission. Especially for 1.5μm, the lower energy level... 3 F4's lifetime relative to the upper energy level3 H4 is an order of magnitude higher, which leads to self-termination of the 1.5μm laser. To achieve laser output at both 1.5μm and 2.3μm, a crucial approach is to suppress cross-relaxation and achieve population inversion. This is achieved by controlling the local coordination within the crystal, thereby modulating Tm. 3+ Near-mid-infrared emission of ions.

[0016] Disorderly distributed mixed type Tm 0.005 Y 0.08 Ca 0.915 F2 crystals, still belonging to the cubic crystal system, not only possess lower phonon energies but also allow for the modulation of Tm at the atomic, molecular, and group scales. 3+ The local coordination structure of ions introduces modulating ions Y into Tm:CaF2 crystals. 3+ When ions are present, Y 3+ and Tm 3+ All will replace Ca 2+ Grid position, on the one hand, Y 3+ The incorporation of ions can break Tm 3+ The cluster structure of ions enables efficient laser output; on the other hand, Y... 3+ The incorporation of ions forms a mixed-type fluoride crystal with a disordered distribution of (Ca,Y)F2 in the form of compound components, creating a truly effective "disordered" activation of ions, thereby inhibiting Tm. 3+ The cross-relaxation of ions enhances the 1.5μm and 2.3μm areas.

[0017] Based on the above theory, this invention develops a laser material with higher output power and greater potential to achieve 1.5μm and 2.3μm laser output than existing fluorides.

[0018] Compared with existing technologies, this invention selects (Ca,Y)F2 as the laser crystal matrix material and uses a temperature gradient method to increase Tm 3+ Ions are incorporated into the (Ca,Y)F2 lattice. The lower phonon energy of (Ca,Y)F2 helps reduce nonradiative transitions caused by multiphonon relaxation, which greatly improves the output efficiency of near-mid-infrared lasers. Furthermore, the disordered, mixed-type crystal structure allows for the modulation of Tm at the atomic, molecular, and group scales. 3+ The local coordination structure of ions forms a truly effective activating ion "disorder," thereby inhibiting Tm. 3+ The cross-relaxation of ions enhances the 1.5μm and 2.3μm areas. Based on the above analysis, Tm 0.005 Y 0.08 Ca 0.915 F2 crystals can achieve higher output power than existing fluorides and have good application potential in laser materials with 1.5μm and 2.3μm laser output. Attached Figure Description

[0019] Figure 1 The X-ray diffraction pattern of the novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal prepared in Example 1 is shown below.

[0020] Figure 2 The room temperature absorption coefficient spectrum of the novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal prepared in Example 1 is shown.

[0021] Figure 3 The images show the room temperature fluorescence spectra of the novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal at 1.5 μm (top) and 2.3 μm (bottom) prepared in Example 1.

[0022] Figure 4 The novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal prepared in Example 1 was excited by 808 nm light. 3 Fluorescence lifetime spectrum corresponding to the H4 energy level;

[0023] Figure 5 Tm prepared in Example 2 0.005 Y 0.04 Ca 0.955 Fluorescence lifetime spectra of sample F2 under 808nm light excitation, corresponding to emission peaks at 1.5μm and 2.3μm;

[0024] Figure 6 Tm prepared in Example 3 0.005 Y 0.06 Ca 0.935 Fluorescence lifetime spectra of sample F2 under 808nm light excitation, corresponding to emission peaks at 1.5μm and 2.3μm;

[0025] Figure 7 Tm prepared in Example 4 0.005 Y 0.12 Ca 0.875 Fluorescence lifetime spectra of the F2 sample corresponding to the emission peaks at 1.5 μm and 2.3 μm under 808 nm light excitation. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] A novel thulium-fluorine-yttrium-calcium composite near-mid-infrared laser crystal, with the chemical formula Tm x Y y Ca 1-x-yF2, where 0.001≤x≤0.01, 0.005≤y≤0.12, has a space group of Fm-3m(225), belongs to the cubic crystal system, and preferably has x=0.005, 0.01≤y≤0.08, with the following cell parameters: Further preferably, the cell parameters are as follows:

[0028] A method for preparing a novel thulium-fluorine-yttrium-calcium composite near-mid-infrared laser crystal includes the following steps:

[0029] 1) Using TmF3, YF3, and CaF2 single crystal particles or powders as raw materials, according to the chemical formula Tm x Y y Ca 1-x-y F2 calculates the required mass of each raw material and weighs it accurately;

[0030] Preferably, the purity of TmF3, YF3, and CaF2 single crystal particles or powders is 5N. 5N purity raw materials contain fewer impurities than chemically analytical grade and 4N purity raw materials, which can avoid problems such as difficulty in obtaining crystals and poor crystal quality caused by impurities reacting with the crucible and raw materials during the growth process.

[0031] 2) Grind the weighed raw material powder thoroughly to make it evenly mixed. The preferred grinding time is 40-60 minutes. Then put it into a porous graphite crucible and cover it with a round graphite lid with a diameter of 1-2 mm.

[0032] 3) Add PbF2 as an oxygen scavenger to prevent the calcium fluoride raw material from being oxidized; the amount added is 5% of the total mass of TmF3, YF3, and CaF2.

[0033] 5) Place the porous graphite crucible in the hot zone and evacuate it until the vacuum level inside the furnace reaches below 8 Pa. Then, fill the furnace with protective gas until the positive bias voltage is zero. Start the heating program and continue heating at a rate of 200-300℃ / h to 1400-1700℃. Hold the temperature for 10-15 hours to ensure complete melting and impurity removal. Then, slowly cool down to 1000-1200℃ at a rate of 1-3℃ / h for 150-500 hours for crystal growth. After the growth is completed, cool down to room temperature at a rate of 50-60℃ / h and then remove the crystal.

[0034] The vacuuming process includes rough vacuuming using a mechanical pump and fine vacuuming using a molecular pump; the protective gas is argon or a fluorine-containing gas, specifically, the fluorine-containing gas is at least one of CF4 or HF.

[0035] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiment.

[0036] Example 1:

[0037] A novel thulium-fluorine-yttrium-calcium composite near-mid-infrared laser crystal Tm 0.005 Y 0.08 Ca 0.915 F2, the preparation method of which includes the following steps:

[0038] 1) Using TmF3, YF3, and CaF2 single crystal particles as raw materials, according to the chemical formula Tm 0.005 Y 0.08 Ca 0.915 Weigh 25g of F2, grind it thoroughly for 40 minutes to mix it evenly, and then put it into a porous graphite crucible.

[0039] 2) Add 1.25g PbF2 as an oxygen scavenger and cover with a round graphite cap;

[0040] 3) Place the porous graphite crucible in a calcining furnace, evacuate the furnace to a vacuum level below 8 Pa, then purge the furnace with argon as a protective atmosphere to zero positive bias. Start the heating program, increasing the temperature to 1500℃ at a rate of 200℃ / h, and hold for 12 hours to ensure complete melting and impurity removal. Then, slowly decrease the temperature to 1100℃ at a rate of 1℃ / h for 300 hours of crystal growth. After growth, cool to room temperature at 50℃ / h. The resulting crystal has good optical quality. 0.005 Y 0.08 Ca 0.915 F2 crystal.

[0041] like Figure 1 The image shows the prepared Tm. 0.005 Y 0.08 Ca 0.915 The X-ray powder diffraction pattern of sample F2 shows that Tm doping... 3+ Tm 0.005 Y 0.08 Ca 0.915 The diffraction peak positions of F2 and CaF2 (JCPDS#35–0816) and (Ca,Y)F2 (JCPDS#35–0293) single crystals are basically consistent.

[0042] like Figure 2 The image shows the prepared Tm. 0.005 Y 0.08 Ca 0.915 The room temperature absorption coefficient spectrum of sample F2 shows that it is very consistent with the emission wavelength of GaAsAl laser diode.

[0043] like Figure 3 The image shows the prepared Tm. 0.005 Y 0.08 Ca0.915 The room temperature fluorescence spectra of the F2 sample at 1.5 μm and 2.3 μm show that the crystal has strong emission at 1.5 μm and 2.3 μm.

[0044] like Figure 4 The image shows the prepared Tm. 0.005 Y 0.08 Ca 0.915 The fluorescence lifetime spectra of sample F2 under 808nm light excitation, corresponding to the emission peaks at 1.5μm and 2.3μm, show that the sample... 3 The lifetime of the H4 level is 1.50 ms.

[0045] That is, the Tm prepared in this embodiment 0.005 Y 0.08 Ca 0.915 The emission cross-section of the F2 crystal at 1.5 μm is 3.05 × 10⁻⁶. – 21 cm 2 The half-width at half-maximum (FWHM) is 76 nm, and the emission cross-section at 2.3 μm is 2.56 × 10⁻⁶. –21 cm 2 The half-width at half-maximum (FWHM) is 195 nm, the fluorescence lifetime is 1.50 ms, and the spectral quality factor is 4.58 × 10⁻⁶. -24 cm 2 s and 3.84×10 -24 cm 2 s.

[0046] Example 2:

[0047] A novel thulium-fluorine-yttrium-calcium composite near-mid-infrared laser crystal Tm 0.005 Y 0.04 Ca 0.955 F2 is prepared in the same way as in Example 1.

[0048] like Figure 5 The image shows the prepared Tm. 0.005 Y 0.04 Ca 0.955 The fluorescence lifetime spectra of sample F2 under 808nm light excitation, corresponding to the emission peaks at 1.5μm and 2.3μm, show that the sample... 3 The lifetime of the H4 level is 1.05 ms.

[0049] Example 3:

[0050] A novel thulium-fluorine-yttrium-calcium composite near-mid-infrared laser crystal Tm 0.005 Y 0.06 Ca 0.935 F2 is prepared in the same way as in Example 1.

[0051] like Figure 6 The image shows the prepared Tm. 0.005 Y 0.06 Ca 0.935 The fluorescence lifetime spectra of sample F2 under 808nm light excitation, corresponding to the emission peaks at 1.5μm and 2.3μm, show that the sample... 3 The lifetime of the H4 level is 1.36 ms.

[0052] Example 4:

[0053] A novel thulium-fluorine-yttrium-calcium composite near-mid-infrared laser crystal Tm 0.005 Y 0.12 Ca 0.875 F2 is prepared in the same way as in Example 1.

[0054] like Figure 7 The image shows the prepared Tm. 0.005 Y 0.12 Ca 0.875 The fluorescence lifetime spectra of sample F2 under 808nm light excitation, corresponding to the emission peaks at 1.5μm and 2.3μm, show that the sample... 3 The lifetime of the H4 level is 1.03 ms.

[0055] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any 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 invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal, characterized in that, The chemical formula of this crystal is Tm x Y y Ca 1-x-y F2, where x = 0.005, 0.01 ≤ y ≤ 0.08; The preparation method includes: mixing TmF3, YF3, and CaF2, heating at 200-300℃ / h in a protective gas atmosphere, holding at 1400-1700℃ for 10-15 h, and then slowly cooling to 1000-1200℃ at a rate of 1-3℃ / h for crystal growth for 150-500 hours. After the growth is completed, cooling to room temperature at 50-60℃ / h yields the crystal.

2. The method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal according to claim 1, characterized in that, The space group of the crystal is Fm-3m(225), which belongs to the cubic crystal system, and the cell parameters are a=b=c=5.458-5.482Å.

3. The method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal according to claim 1, characterized in that, The TmF3, YF3, and CaF2 mentioned are corresponding single crystal particles or powders.

4. The method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal according to claim 1, characterized in that, The mixing process of TmF3, YF3 and CaF2 is grinding for 40-60 minutes.

5. The method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal according to claim 1, characterized in that, PbF2 is added before calcination, and the amount added is 5% of the total mass of TmF3, YF3 and CaF2.

6. The method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal according to claim 1, characterized in that, The protective gas is at least one of argon, CF4, or HF.

7. The method for preparing a novel thulium-doped yttrium-calcium composite near-mid-infrared laser crystal according to claim 1, characterized in that, During the calcination process, the calcination vessel for TmF3, YF3, and CaF2 is a porous graphite crucible.

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