Laser crystal material and preparation method and application thereof

Abstract

The present application discloses a laser crystal material, its preparation method, and its application, belonging to the field of inorganic functional crystal materials. The chemical formula of the laser crystal material is Ca3Yb2AlGaO9. The crystal is grown by the melt pulling method. The laser crystal material has ultra-wideband absorption and emission properties. Under 939nm pumping, the laser crystal material can achieve tunable femtosecond laser output in the infrared band of 950 to 1070nm. The laser crystal material has a structural feature of disordered atomic distribution, and its absorption cross section and half-maximum width are large, which helps the crystal absorb pump light, thereby enhancing the crystal's fluorescence emission in the infrared band of ~1 micron; the large emission cross section and half-maximum width, as well as strong fluorescence emission, help increase the femtosecond laser emission power and efficiency, and compress the pulse width. It is a femtosecond laser crystal material with great application value.

Description

Technical Field

[0001] The present application relates to a laser crystal material and a preparation method and application thereof, belonging to the field of inorganic functional crystal materials. Background Art

[0002] Femtosecond lasers are an ultra-strong, ultrafast laser technology that developed rapidly in the early 1980s. Unlike other long-pulse lasers and continuous lasers, they possess characteristics such as ultrashort pulses, ultrahigh electric fields, and ultrawide frequency spectra, representing extreme physical conditions that can be achieved in a laboratory. Ultrashort pulse durations require only a relatively small amount of laser energy (μJ) to generate extremely high instantaneous power at the focal point, reaching trillions of watts. The focusing intensity is even higher than the energy density of all the light radiated from the sun to Earth when focused to the size of a needle tip. Femtosecond laser pulses can generate plasma, which, when interacting with matter, can produce a variety of phenomena based on the nonlinear interaction between light and matter. Therefore, femtosecond laser technology has been widely used in various fields, including information technology, energy, environment, medicine, national defense, and basic scientific research.

[0003] Femtosecond lasers in the infrared band of 1 micron have attracted great attention due to their unique advantages and have important applications in all-solid-state lasers, biomedicine, industrial processing, etc. At present, the realization of 1 micron lasers is mostly achieved by pumping Yb-doped lasers with semiconductor laser diodes (LDs). 3+ The gain medium can directly obtain 1 micron laser, with simple device, compact structure, high laser output power and optical-to-optical conversion efficiency. 3+ ) gain medium mode-locked lasers have the widest application. Commonly used Yb-doped crystals include Yb:YAG, Yb:CaF2, Yb:CaGdAlO4, Yb:CaYAlO4, etc., which have obvious advantages such as wide emission spectrum and few quantum defects. However, since existing laser crystals are difficult to take into account both high power and short pulse width, the discovery of new laser crystals with ultra-wideband luminescence and ultrashort pulse properties is still a hot research direction in the field of all-solid-state lasers. Summary of the Invention

[0004] This application provides a laser crystal material, Ca3Yb2AlGaO9, a novel femtosecond laser crystal material. This crystal is grown using the melt-pulling method. This laser crystal material is an excellent laser host crystal. Using a 939nm pump, it produces ultra-broadband fluorescence emission in the 950-1070nm band, with a peak wavelength of 996nm. This laser crystal material can be used to generate broadband infrared femtosecond lasers.

[0005] According to a first aspect of the present application, a laser crystal material is provided.

[0006] A laser crystal material, wherein the chemical formula of the laser crystal material is Ca3Yb2AlGaO9.

[0007] Optionally, the laser crystal material belongs to the monoclinic system and the P21 / c space group.

[0008] Optionally, the unit cell parameters of the laser crystal material are α=γ=90°, β=107~109°, Density is 6.14-6.16 g·cm -3 .

[0009] Specifically, the unit cell parameters of the laser crystal material are β=108°, Density is 6.15 g·cm -3 .

[0010] Optionally, the laser crystal material is in block shape;

[0011] The laser crystal material has at least one dimension with a size of 35 to 66 mm.

[0012] Optionally, the diameter of the laser crystal material is 25-35 mm, and the length is 45-66 mm.

[0013] Optionally, the absorption spectrum of the laser crystal material contains a broadband absorption peak with a peak wavelength of 980 nm in the 900-1025 nm band.

[0014] Optionally, the fluorescence spectrum of the laser crystal material under 939 nm pumping contains a broadband emission peak with a peak wavelength of 996 nm in the 950-1070 nm band.

[0015] This laser crystal material has excellent physical and chemical properties. It does not absorb moisture in air and the crystal is insoluble in acids and alkalis. It has a high melting point, high mechanical strength, a high laser damage threshold, and high thermal conductivity.

[0016] According to a second aspect of the present application, a method for preparing the laser crystal material described above is provided.

[0017] The above-mentioned method for preparing the laser crystal material adopts a melt-pulling method and comprises the following steps:

[0018] S1. Obtain Ca3Yb2AlGaO9 polycrystalline raw material rod;

[0019] S2. The raw materials of CaCO3, Yb2O3, Ga2O3 and Al2O3 are weighed in a stoichiometric ratio, ground and mixed, pressed into blocks, sintered to generate polycrystalline materials, heated and melted, and the Ca3Yb2AlGaO9 polycrystalline raw material rod is used as a seed crystal for introduction. After the crystal is formed on the seed crystal, crystal growth is carried out to obtain the laser crystal material.

[0020] Optionally, the Ca3Yb2AlGaO9 polycrystalline raw material rod is produced by hot isostatic pressing.

[0021] Optionally, the size of the Ca3Yb2AlGaO9 polycrystalline raw material rod is Φ6mm×50mm.

[0022] Optionally, the molar ratio of CaCO3, Yb2O3, Ga2O3 and Al2O3 is CaCO3:Yb2O3:Ga2O3:Al2O3=6:2:1:1.

[0023] Optionally, the crystal growth conditions are:

[0024] The pulling rate is 0.5-1.8 mm / h, the rotation speed of the seed crystal rod is 5-12 rpm, the growth rate is 0.7-1.3 mm / h, and after the growth is completed, the crystal is lifted from the liquid surface and cooled to room temperature at a rate of 15-65°C / h.

[0025] Optionally, the purity of CaCO3, Yb2O3, Ga2O3 and Al2O3 is 99.999%.

[0026] Optionally, raw materials containing CaCO3, Yb2O3, Ga2O3, and Al2O3 are weighed according to a stoichiometric ratio, placed in a homemade mixer for wet mixing, pressed into blocks at 25 MPa, and placed in a sintering furnace for high-temperature sintering at 1350°C for 48 hours, and then heated and melted in a single crystal growth furnace. Ca3Yb2AlGaO9 polycrystalline raw material rods are used as seed crystals for introduction, and crystals are grown on the seed crystals.

[0027] As a specific embodiment, the method for preparing the laser crystal material includes at least the following steps:

[0028] CaCO3, Yb2O3, Ga2O3 and Al2O3 are used as raw materials, wherein the molar ratio of CaCO3, Yb2O3, Ga2O3 and Al2O3 in the raw materials is CaCO3:Yb2O3:Ga2O3:Al2O3=6:2:1:1, and the chemical substances are weighed and finely ground according to the molar ratio. The raw materials CaCO3, Yb2O3, Ga2O3 and Al2O3 are mixed and pressed into tablets, and then placed in an iridium crucible of a crystal growth furnace, evacuated and heated to 1860°C for melting. Then, a Φ6mm×50mm Ca3Yb2AlGaO9 polycrystalline raw material rod made by hot isostatic pressing equipment is selected as the seed crystal for introduction and crystal growth is carried out. The growth conditions are: a pulling rate of 0.5-1.8mm / h, a rotation rate of the seed crystal rod of 5-12rpm, and after the growth is completed, the crystal is lifted from the liquid surface and cooled to room temperature at a rate of 15-65°C / h to obtain the block crystal with a diameter of 25-35mm and a length of 45-66mm.

[0029] According to a third aspect of the present application, there is provided an application of the above-mentioned laser crystal material in infrared femtosecond laser.

[0030] The laser crystal material is used for realizing the output of femtosecond laser with a wavelength in the infrared band of 950-1070 nm under 939 nm pumping.

[0031] According to a fourth aspect of the present application, an all-solid-state femtosecond laser is provided.

[0032] An all-solid-state femtosecond laser comprises the laser crystal material described above.

[0033] Optionally, the all-solid-state femtosecond laser further includes an LD end-face pump module, a beam coupling system, an input mirror, a folding mirror, a chirped mirror, and a SESAM output mirror;

[0034] The beam coupling system is located behind the LD end-face pump module;

[0035] The input mirror is located after the beam coupling system;

[0036] The folding mirror is located behind the input mirror;

[0037] The chirped mirror is located behind the folding mirror;

[0038] The SESAM output mirror is located after the chirped mirror;

[0039] The laser crystal material is located between the input mirror and the folding mirror.

[0040] Optionally, the pump source of the LD end-face pump module is a 939nm InGaAs LD;

[0041] The pumping mode is end-face pumping, and the pump source is a fiber-coupled semiconductor laser;

[0042] The laser resonant cavity is a plano-concave cavity with a total cavity length of 58 mm;

[0043] The input mirror is a plane mirror, and the mirror surfaces on both sides are coated with a 939nm anti-reflection film and a 1035-1060nm high-reflection film respectively;

[0044] The output mirror is a concave mirror with a curvature radius of 75 mm and a transmittance of 3%.

[0045] The beneficial effects of this application include:

[0046] 1) The laser crystal material Ca3Yb2AlGaO9 provided in this application has ultra-wideband absorption and emission properties. Under 939nm pumping, the laser crystal material can achieve tunable femtosecond laser output in the infrared band of 950 to 1070nm.

[0047] 2) The laser crystal material Ca3Yb2AlGaO9 provided in this application is different from the ordinary Yb 3+ Doped aluminates such as CaGdAlO4, CaYAlO4 and Y3Al5O 12 Compared with other crystals, it has the following advantages: Ca3Yb2AlGaO9 has the structural characteristics of disordered atomic distribution, and its absorption cross-section and half-maximum width are large, which helps the crystal to absorb pump light, thereby enhancing the crystal's fluorescence emission in the infrared band of ~1 micron; it has a large emission cross-section and half-maximum width, as well as strong fluorescence emission, which is very beneficial to laser output, helps to increase the emission power and efficiency of femtosecond lasers, and helps to compress the pulse width. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is the Ca3Yb2AlGaO9 crystal grown by the pulling method in Example 1.

[0049] Figure 2 This is the X-ray powder diffraction pattern of Ca3Yb2AlGaO9 crystal, compared with the standard card (No. 14-0475).

[0050] Figure 3 This is the room temperature absorption spectrum of Ca3Yb2AlGaO9 crystal.

[0051] Figure 4 This is the fluorescence spectrum of Ca3Yb2AlGaO9 crystal in the infrared band under 939nm pumping.

[0052] Figure 5This is a schematic diagram of the device for laser experiments using Ca3Yb2AlGaO9 crystals, where M1, M2, and M3 are the input mirror, folding mirror, and chirped mirror, respectively. The laser diode and SESAM are the laser semiconductor pump source and semiconductor saturable absorber mirror, respectively. DETAILED DESCRIPTION

[0053] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0054] Unless otherwise specified, all raw materials and reagents used in this application were purchased from commercial sources and used directly without treatment. The instruments and equipment used adopted the protocols and parameters recommended by the manufacturers.

[0055] In the embodiment, the instrument used for the crystal pulling method is a DJL-600 crystal growth furnace, the crucible used is an iridium crucible of Ф80mm×80mm, and the raw materials used are CaCO3, Yb2O3, Ga2O3 and Al2O3 with a purity of 99.999%.

[0056] In the examples, powder X-ray analysis of the samples was performed on a Miniflex 600 powder diffractometer.

[0057] In the examples, the absorption spectra of the samples were measured on a Lambda950 absorption spectrometer produced by Pekin-Elmer; and the fluorescence spectra under 939 nm pumping were measured on a FLS980 fluorescence spectrometer produced by Edinburgh, UK.

[0058] Example 1 Preparation of Large-Size Single Crystal Samples of Ca3Yb2AlGaO9

[0059] CaCO3, Yb2O3, Ga2O3 and Al2O3 are prepared as raw materials according to the following chemical reaction formula:

[0060] 6CaCO3+2Yb2O3+Ga2O3+Al2O3→2Ca3Yb2AlGaO 9+ 6CO2↑

[0061] According to the above molar ratio of CaCO3﹕Yb2O3﹕Ga2O3﹕Al2O3=6:2:1:1, CaCO3, Yb2O3, Ga2O3 and Al2O3 were weighed, and the total weight of the raw materials was 2400g. After mixing evenly, a hydraulic press was used to press them into cylindrical blocks at 25Mpa, and placed in a sintering furnace for high temperature sintering at 1350℃ for 48h, placed in an iridium crucible of Ф80mm×80mm, placed in a DJL-600 crystal growth furnace, evacuated, and slowly heated at a rate of 250℃ / h. The raw materials are melted and kept at a constant temperature for 4 hours to completely melt the raw materials. Then, a Φ6mm×50mm Ca3Yb2AlGaO9 polycrystalline raw material rod prepared by hot isostatic pressing equipment is used as the seed crystal for introduction. The preparation method is: the Ca3Yb2AlGaO9 polycrystalline raw material powder prepared according to the chemical proportion is placed in a closed cylindrical rubber container, and an equal pressure of 200Mpa is applied to the product in all directions. At the same time, a high temperature of 1000℃ is applied. Under the action of high temperature and high pressure, the product is sintered and densified to form a cylindrical raw material rod.

[0062] After the crystals are formed on the seed crystals, the crystals are grown. During the growth process, the growth rate is set to 1 mm / h, the pulling speed is 1 mm / h, and the rotation rate of the seed crystal rod is 8 rpm. After the growth is completed, the crystals are lifted from the liquid surface and cooled to room temperature at a rate of 40 ° C / h to obtain colorless and transparent crystals with a size of Φ27 mm × 56 mm. The crystal photos are shown in the figure. Figure 1 shown.

[0063] Example 2 Crystal structure characterization of the sample

[0064] A small piece was cut from the grown bulk crystal and finely ground into powder. The structure of the crystal sample was determined by X-ray diffraction.

[0065] The measured diffraction pattern is compared with the XRD diffraction pattern of Y4Al2O9 standard card. Figure 2 As shown in the figure, the actual measured XRD spectrum is roughly consistent with the diffraction peak position of the substance in the standard card, indicating that the structure of the obtained sample is similar to it, and that the obtained crystal is a high-purity crystal Ca3Yb2AlGaO9 without impurity phase.

[0066] The crystal structure is analyzed and belongs to the monoclinic system, P21 / c space group, unit cell parameters α=γ=90°, β=108°,

[0067] The density is obtained by testing using the following method. The specific steps are:

[0068] Ⅰ from Example 1 cut a square crystal of size 5mm × 5mm × 5mm, weighed on a balance to obtain its mass m;

[0069] II. Pour an appropriate amount of water into a graduated cylinder and record the volume V1. Then place the square crystal into the cylinder and read the volume V2.

[0070] Ⅲ. Repeat the above steps three times and record the experimental data each time;

[0071] IV. Calculate the density of the crystal using the formula ρ = m(V2-V1). Take the average of three experiments and obtain a crystal density of 6.15 g cm -3 .

[0072] Example 3 Spectral performance measurement of samples

[0073] The grown bulk crystals were cut, processed and polished into pieces with the dimensions of 10.0 × 10.0 × 1.0 mm. 3 X-cut crystal piece, two parallel surfaces of light passing through 10.0×10.0mm 2 Polishing, and conducting spectral performance testing in the E / / X direction.

[0074] The results show that Figure 3 As shown, the absorption spectrum of the sample shows that Yb 3+ The characteristic absorption peak of Yb has a wide absorption peak between 900-1025nm, with a peak wavelength of 980nm, corresponding to 3+ : 2 F 7 / 2 arrive 2 F 5 / 2 This absorption band matches the commercial InGaAs semiconductor pump source, making the crystal very suitable for laser experiments using commercial InGaAs diode pumping.

[0075] like Figure 4 As shown in the figure, the room temperature fluorescence spectrum of the sample under 939 nm pumping has a wide fluorescence emission band between 950 and 1070 nm, with a peak wavelength of 996 nm, corresponding to Yb 3+ : 2 F 5 / 2 → 2 F 7 / 2 The full width at half maximum (FWHM) is 75.8 nm, and the emission cross section calculated using the FL equation is 8.55×10 -21 cm 2 @996nm, the emission cross section and emission bandwidth are large, which is conducive to the realization of femtosecond laser output.

[0076] The above research and experimental results show that Ca3Yb2AlGaO9 crystal is a laser crystal material with great application prospects and can achieve femtosecond laser output in the 950-1070nm infrared band.

[0077] Application of Example 4 in Laser Device

[0078] From the as-grown Ca3Yb2AlGaO9 crystal, an X-cut crystal rod measuring 3mm × 3mm × 8mm was machined. Both ends were precision-polished with 3mm × 3mm surfaces for laser performance testing. The crystal was placed on a cooling system consisting of a temperature-controlled stage and a copper block. During the experiment, the crystal temperature was maintained at 7–8°C with a control accuracy of 0.1°C. A layer of indium paper was placed between the copper stage and the crystal to improve heat dissipation. A 939nm InGaAs LD pump source was used for end-pumping. The pump light passed through a double-cemented achromatic lens and plane mirror 1 before being focused at the center of the crystal. The laser resonator consisted of a plano-concave mirror with a total length of 58mm. The input mirror was a plane mirror with two mirror surfaces coated with a 939nm anti-reflection coating and a 1035–1060nm high-reflection coating, respectively. The transmittance at 939nm was greater than 96%, and the reflectance at 1035–1060nm was greater than 99.7%. The output mirror was a concave mirror with a radius of curvature of 75mm and a transmittance of 3%. Schematic diagram of the experimental setup Figure 5 As shown, the beam coupling system is located after the LD end-pumping module, with the laser diode serving as the laser diode pump source for the LD end-pumping module. The input mirror M1 is located after the beam coupling system; the folding mirror M2 is located after the input mirror M1; the chirped mirror M3 is located after the folding mirror M2; the SESAM, a semiconductor saturable absorber, is located after the chirped mirror M3; and the laser crystal is located between the input mirror M1 and the folding mirror M2. In the tunable laser experiment, an etalon is inserted as a wavelength-selective element. The saturable absorber is located between the etalon and the output mirror. The results show that due to the disordered structure and broadened emission band of the Ca3Yb2AlGaO9 crystal, the laser exhibits multi-wavelength output from 1035 to 1045 nm, with a central wavelength of approximately 1035 nm. Further adjustments to the pump power and laser parameters achieved hundred-femtosecond laser output. Furthermore, the repetition rate and pulse width exhibit an inverse relationship, with a higher repetition rate corresponding to a narrower pulse width, demonstrating a typical passive Q-switching behavior.

[0079] Therefore, the new crystal Ca3Yb2AlGaO9 provided by the present invention is a very excellent femtosecond laser gain material.

[0080] The several embodiments of the present application do not limit the present application in any form. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technical personnel familiar with this profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A laser crystal material, characterized in that: The chemical formula of the laser crystal material is Ca3Yb2AlGaO9; The laser crystal material belongs to the monoclinic system and the P21 / c space group; The unit cell parameters of the laser crystal material are a=7.3905 Å, b=10.8840 Å, c=11.3143 Å, β=108°, V=910.1019 Å 3 , with a density of 6.15 g·cm -3 .

2. The laser crystal material according to claim 1, characterized in that The laser crystal material is in block shape; The laser crystal material has at least one dimension with a size of 35-66 mm.

3. The laser crystal material according to claim 2, characterized in that The diameter of the laser crystal material is 25-35 mm and the length is 45-66 mm.

4. The laser crystal material according to claim 1, characterized in that The absorption spectrum of the laser crystal material contains a broadband absorption peak with a peak wavelength of 980 nm in the 900-1025 nm band.

5. The laser crystal material according to claim 1, characterized in that The fluorescence spectrum of the laser crystal material under 939 nm pumping contains a broadband emission peak with a peak wavelength of 996 nm in the 950-1070 nm band.

6. The method for preparing the laser crystal material according to any one of claims 1 to 5, characterized in that: The preparation method adopts a melt pulling method, comprising the following steps: S1. Obtain Ca3Yb2AlGaO9 polycrystalline raw material rod; S2. The raw materials of CaCO3, Yb2O3, Ga2O3 and Al2O3 are weighed in a stoichiometric ratio, ground and mixed, pressed into blocks, sintered to generate polycrystalline materials, heated and melted, and the Ca3Yb2AlGaO9 polycrystalline raw material rod is used as a seed crystal for introduction. After the crystal is formed on the seed crystal, crystal growth is carried out to obtain the laser crystal material.

7. The preparation method according to claim 6, characterized in that Ca3Yb2AlGaO9 polycrystalline raw material rods were prepared by hot isostatic pressing.

8. The preparation method according to claim 7, characterized in that The size of the Ca3Yb2AlGaO9 polycrystalline raw material rod is Φ6 mm×50 mm.

9. The preparation method according to claim 6, characterized in that The molar ratio of CaCO3, Yb2O3, Ga2O3 and Al2O3 is CaCO3﹕Yb2O3﹕Ga2O3﹕Al2O3=6:2:1:

1.

10. The preparation method according to claim 6, characterized in that The conditions for the crystal growth are: The pulling rate is 0.5~1.8 mm / h, the rotation speed of the seed rod is 5~12 rpm, and the growth rate is 0.7~1.3 mm / h. After the growth is completed, the crystal is lifted from the liquid surface and cooled to room temperature at a rate of 15~65 ℃ / h.

11. Use of the laser crystal material according to any one of claims 1 to 5 in infrared femtosecond laser.

12. The use according to claim 11, characterized in that The laser crystal material is used to realize the output of femtosecond laser with a wavelength in the infrared band of 950-1070 nm under 939 nm pumping.

13. An all-solid-state femtosecond laser, characterized in that: The all-solid-state femtosecond laser comprises the laser crystal material according to any one of claims 1 to 5.

14. The all-solid-state femtosecond laser according to claim 13, characterized in that: The all-solid-state femtosecond laser also includes an LD end-face pump module, a beam coupling system, an input mirror, a folding mirror, a chirped mirror, and a SESAM output mirror; The beam coupling system is located behind the LD end-face pump module; The input mirror is located after the beam coupling system; The folding mirror is located behind the input mirror; The chirped mirror is located behind the folding mirror; The SESAM output mirror is located after the chirped mirror; The laser crystal material is located between the input mirror and the folding mirror.

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