Yb:er:yag crystal for 2940 nm laser and preparation method thereof

Abstract

The application discloses a Yb:Er:YAG crystal for a 2940nm laser and a preparation method thereof, and belongs to the preparation of optical elements. The Yb:Er:YAG crystal is prepared from a Yb:Er:YAG block through a pulling method, and the Yb:Er:YAG block contains Yb 1 at%~10 at%, Er 30 at%~55 at% and the balance of YAG; wherein the atomic percentage value of Yb:Er is 1:8~25. The application improves the pumping absorption efficiency through Yb³⁺ sensitization, effectively alleviates the self-termination effect in high-doped Er:YAG through Yb to Er energy transfer, and realizes the optimal balance of energy transfer efficiency-quenching probability.

Description

Technical Field

[0001] This invention relates to the fabrication of optical elements, and particularly to a Yb:Er:YAG crystal for a 2940nm laser and its fabrication method. Background Technology

[0002] Er3+:YAG crystal (Er-doped yttrium aluminum garnet) belongs to the cubic crystal system and is a promising mid-infrared solid-state laser material. It can output lasers of three wavelengths at room temperature: 1640 nm and 2940 nm. The 2940 nm wavelength is at the hydroxyl absorption peak and can be strongly absorbed by biological tissues. Therefore, the 2940 nm laser is widely used in medical aesthetics, precision machining and other fields.

[0003] For 2940 nm laser output, a high Er³⁺ doping concentration is generally used. High doping can shorten the absorption length, enabling device miniaturization; increase energy density and gain, thus increasing output power; simultaneously, shorter crystals are beneficial for thermal management, reducing thermal lensing effects and improving beam quality. However, the 2940 nm laser transition in Er:YAG exhibits a self-termination effect: the upper energy level... 4 I 11 The fluorescence lifetime of / 2 is only about 100 μs (with high doping), while the lower energy level 4 I 13 The lifetime of / 2 is approximately 2 ms. Long-term accumulation of lower-level particles suppresses laser oscillation. Continuous laser output can only be maintained by effectively depleting these particles through an energy transfer upconversion (ETU) process between high-concentration Er³⁺ particles. However, highly doped Er:YAG lasers suffer from low pump efficiency, energy upconversion losses, and fluorescence quenching. Maintaining efficient 2940nm laser output while achieving an optimal balance between energy efficiency and laser performance is a pressing technical challenge in this field.

[0004] The above background information is provided to facilitate understanding of the present invention and is not intended to be publicly known technology disclosed to the general public prior to the application of this invention. Summary of the Invention

[0005] To address the aforementioned shortcomings, this invention provides a Yb:Er:YAG crystal for 2940nm lasers and its preparation method, solving the problem of concentration quenching under high Er conditions.

[0006] The technical solution is: a Yb:Er:YAG crystal for a 2940nm laser, wherein the Yb:Er:YAG crystal is formed by Czochralski crystal pulling of Yb:Er:YAG ingots, and the Yb:Er:YAG ingots contain: Yb 1 at%~10 at% Er 30 at%~55 at% and The margin is YAG; The atomic percentage of Yb:Er is 1:8~25.

[0007] Furthermore, Yb 2 at%~8 at%.

[0008] Furthermore, Yb 2.5 at%~5.5 at%.

[0009] Furthermore, Er 45 at%~50 at%.

[0010] Furthermore, the atomic percentage of Yb:Er is 1:10~15.

[0011] Furthermore, the Yb:Er:YAG briquettes are prepared by the following steps: M1, according to the formula, take ytterbium oxide, erbium oxide, yttrium oxide and aluminum oxide, mix and ball mill into wet material; M2, wet material is dried and dry-pressed; drying temperature 75℃~85℃, dry pressing pressure 10 MPa~50MPa; M3, solid-phase reaction at 1400℃~1600℃ for 8 to 12 hours, to obtain Yb:Er:YAG blocks.

[0012] Furthermore, the purity of the ytterbium oxide is ≥99.999wt%, the erbium oxide is ≥99.999wt%, the yttrium oxide is ≥99.999wt%, and the aluminum oxide is ≥99.999wt%.

[0013] The present invention also provides a method for preparing Yb:Er:YAG crystals.

[0014] The technical solution is: a method for preparing the above-mentioned Yb:Er:YAG crystal, comprising the following steps: S1, load the Yb:Er:YAG material block into the crucible, and then load the crucible into the crystal pulling furnace; S2, crystal pulling is performed under an atmosphere, with a growth rate of 0.5 mm / h ~ 1.5 mm / h and a rotation speed of 8 rpm ~ 15 rpm; S3. After crystal pulling, anneal at 1200℃~1300℃ for 20~35 hours, and then cool to room temperature at a cooling rate of 0.5°C / min~2°C / min to obtain Yb:Er:YAG crystals.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention simultaneously dops ytterbium with high-concentration erbium doping, and controls the at% ratio of Yb:Er within a specific range. Yb³⁺ (ionic radius 0.086 nm) and Er³⁺ are both rare-earth ions, randomly distributed in the YAG lattice. Each Yb³⁺ is surrounded by an average of 12-13 Er³⁺ ions, increasing the Er-Er spacing from ~0.4 nm in highly doped pure Er to ~0.8 nm, reducing the cross-relaxation probability to <10%. The absorption cross-section of Yb³⁺ for pump light (~10⁻² cm²) is 5 times that of Er³⁺, preferentially absorbing pump energy and rapidly transferring it to Er³⁺, shortening the time required for Er³⁺ to reach its maximum concentration. 4 I 11 The lifetime of the / 2 level is reduced (from ~5ms at low doping to ~1ms), reducing the upconversion quenching time window (upconversion probability is proportional to excited state lifetime); the scope of this invention avoids Yb-Yb self-quenching, ensuring that the energy transferred by each Yb³⁺ can be completely absorbed by the surrounding Er³⁺, without loss due to energy redundancy.

[0016] This invention overcomes the "concentration quenching" bottleneck of high-concentration erbium doping, achieving a balance between miniaturization and high gain. This invention creatively introduces ytterbium (Yb) co-doping into ultra-high concentration erbium doping (30 at% ~ 55 at%), precisely controlling the Yb:Er atomic ratio within a specific window of Yb:Er = 1:8 ~ 1:25. Under this formulation, Yb³⁺ ions (ionic radius 0.086 nm) act as "isolation agents," randomly distributed in the YAG lattice, effectively inserting between Er³⁺ ion clusters and blocking the Er-Er nearest neighbor cross-relaxation (CR) channels that lead to non-radiative transitions. Experiments show that at this ratio, the harmful Er-Er cross-relaxation probability is reduced to below 10%, thus significantly suppressing the concentration quenching effect that inevitably occurs in traditional high-concentration doping while maintaining a high gain coefficient (short crystal length), solving the problem of the incompatibility between device miniaturization and high efficiency.

[0017] This invention optimizes energy transfer balance and avoids secondary quenching. The Yb concentration (1-10 at%) and Yb:Er ratio specified in this invention ensure that there are sufficient Er³⁺ acceptors (approximately 12-13 on average) around each Yb³⁺ ion. This avoids Yb-Yb energy migration quenching caused by excessive Yb concentration and ensures that almost 100% of the absorbed energy is transferred to Er ions, with no energy redundancy or waste.

[0018] This invention achieves the optimal balance of overall performance. Through experiments, this invention has been verified that when the Yb:Er ratio is 1:10 to 1:15 (such as 4at% Yb : 50at% Er in Example 1), the overall performance of the crystal reaches its peak: the slope efficiency is significantly improved compared with the traditional low-concentration Er:YAG, the heat load is greatly reduced, and the beam quality is closer to the diffraction limit. Attached Figure Description

[0019] Figure 1 This is a cross-sectional photograph of the YAG block from Embodiment 1 of the present invention; Figure 2 This is a cross-sectional photograph of YAG crystal B1 in Embodiment 5 of the present invention; Figure 3 This refers to YAG crystal B1 from Embodiment 5 of the present invention. Detailed Implementation

[0020] The invention will now be further described with reference to the accompanying drawings.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection via an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In the description of this invention, "a plurality of" means two or more, unless otherwise precisely specified.

[0023] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0026] In this invention, high purity refers to a purity greater than or equal to 99.999 wt%. Unless otherwise specified, this invention represents common technology in the field.

[0027] Example 1 A method for preparing erbium- and ytterbium-doped YAG pellets includes the following steps: M1, based on 4 at% ytterbium and 50 at% erbium, consists of ytterbium oxide (high purity, purchased from the market), erbium oxide (high purity, purchased from the market), yttrium oxide (high purity, purchased from the market), and alumina (high purity, purchased from the market). These are ball-milled in a ball mill for 24 hours to form a wet material. The ball milling media is ethanol, and the grinding media is alumina grinding balls.

[0028] M2, wet material is dried and dry-pressed; drying temperature 80℃, dry pressing pressure 30MPa.

[0029] M3 was subjected to a solid-phase reaction at 1600℃ for 10 hours to obtain erbium- and ytterbium-doped YAG lumps A1.

[0030] Cross-sectional photos of YAG block A1 are shown below. Figure 1 .

[0031] Example 2 The difference compared to Example 1 is as follows: In M1, ytterbium is 6 at% and erbium is 50 at%.

[0032] In this embodiment, YAG material block A2 with erbium and ytterbium doping was obtained.

[0033] Example 3 The difference compared to Example 1 is as follows: In M1, ytterbium is 2 at%, erbium is 50 at%.

[0034] In this embodiment, YAG material block A3 with erbium and ytterbium doping was obtained.

[0035] Example 4 The difference compared to Example 1 is as follows: In M1, ytterbium is 4.18 at% and erbium is 46 at%.

[0036] This embodiment yields YAG material block A4 containing erbium and ytterbium.

[0037] Comparative Example 1 The difference compared to Example 1 is as follows: In M1, ytterbium is 7.14 at% and erbium is 50 at%.

[0038] This comparative example yielded YAG pellets A doped with erbium and ytterbium. -1 .

[0039] Comparative Example 2 The difference compared to Example 1 is as follows: In M1, ytterbium is 1.67 at% and erbium is 50 at%.

[0040] This comparative example yielded YAG pellets A doped with erbium and ytterbium. -2 .

[0041] Comparative Example 3 The difference compared to Example 1 is as follows: In M1, ytterbium is 2.8 at% and erbium is 35 at%.

[0042] This comparative example yielded YAG pellets A doped with erbium and ytterbium. -3 .

[0043] Comparative Example 4 The difference compared to Example 1 is as follows: In M1, ytterbium is 5.2 at% and erbium is 65 at%.

[0044] This comparative example yielded YAG pellets A doped with erbium and ytterbium. -4 .

[0045] Comparative Example 5 The difference compared to Example 1 is as follows: M1 contains only erbium, i.e., M1 is: based on 5at% erbium, take erbium oxide (high purity, purchased from the market), yttrium oxide (high purity, purchased from the market), and alumina (high purity, purchased from the market), and ball mill them in a ball mill for 24 hours to form a wet material. The ball milling medium is ethanol and alumina grinding balls.

[0046] M3, to obtain erbium-doped YAG block A -5 .

[0047] Comparative Example 6 Compared to Comparative Example 5, the difference is that in M1, erbium is 1.0 at%.

[0048] Obtain erbium-doped YAG pellet A -6 .

[0049] Example 5 Take A1, A2, A3, A4, A respectively. -1 A -2 A -3 A -4、 A -5 And A -6 Each of them produces erbium-doped and ytterbium-doped YAG crystals in the same crystal pulling furnace according to the production method of this embodiment.

[0050] A method for producing erbium-doped and ytterbium-doped YAG crystals includes the following steps: S1, erbium-doped and ytterbium-doped YAG material blocks are loaded into a molybdenum crucible, and the molybdenum crucible is loaded into a crystal pulling furnace.

[0051] S2, crystal pulling is performed under an argon atmosphere using the Czochralski method, with a growth rate of 0.5 mm / h ~ 1.5 mm / h and a rotation speed of 8 rpm ~ 15 rpm.

[0052] S3, after crystal pulling, is annealed at 1250℃ for 30 hours and then cooled to room temperature at a rate of 1°C / min.

[0053] S4 is processed into a Φ4×80mm rod shape and polished at both ends to obtain erbium-doped and ytterbium-doped YAG crystals.

[0054] In this embodiment, erbium-doped and ytterbium-doped YAG crystals B1, B2, B3, B4, and B were obtained respectively. -1 B -2 B -3 And erbium-doped YAG crystal B -4 And B -5 .

[0055] Cross-sectional photograph of YAG crystal B1 as shown Figure 2 YAG crystal B1, such as Figure 3 .

[0056] Detection of B1, B2, B3, B4, B -1 B -2 B -3 B -4 B -5 And B -6 The crystal performance parameters are shown in Table 1 below.

[0057] Table 1 Crystal Properties From Table 1, we can conclude that: Comparative Example 5 shows that at the erbium doping concentration in Comparative Example 5, the concentration quenching effect is already very severe, leading to a sharp decrease in energy efficiency, a significant drop in slope efficiency, and a sharp increase in heat load. In Examples 1-4, ytterbium was doped simultaneously with high concentrations of erbium, and the at% ratio of Yb:Er was controlled within 1:8~25, which suppressed the quenching effect under high Er doping and reduced the heat load. Compared with Comparative Example 1, the performance was greatly improved. Among them, Example 1 achieved the optimal balance between energy transfer efficiency and quenching probability, and the performance was optimized. Although the at% ratio of Yb:Er in Comparative Examples 3 and 4 was within 1:8~25, the Er doping concentration was too high or too low, and the effect of Examples 1-4 was not achieved. Comparative Examples 1-2 had out-of-control at% ratios of Yb:Er, resulting in a "energy transfer efficiency - quenching probability" imbalance and poor performance. Compared with Comparative Example 1, the overall performance was basically not improved.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A Yb:Er:YAG crystal for a 2940nm laser, characterized in that, This Yb:Er:YAG crystal is formed by Czochralski crystal pulling from a Yb:Er:YAG ingot. The Yb:Er:YAG ingot contains: Yb 1 at%~10 at% Er 30 at%~55 at% and The margin is YAG; The atomic percentage of Yb:Er is 1:8~25.

2. The Yb:Er:YAG crystal for a 2940nm laser according to claim 1, characterized in that, Yb 2 at%~8 at%.

3. The Yb:Er:YAG crystal for a 2940nm laser according to claim 2, characterized in that, Yb 2.5at%~5.5 at%.

4. The Yb:Er:YAG crystal for a 2940nm laser according to claim 1, characterized in that, Er 45at%~50at%.

5. The Yb:Er:YAG crystal for a 2940nm laser according to claim 1, characterized in that, The atomic percentage of Yb:Er is 1:10~15.

6. The Yb:Er:YAG crystal for a 2940nm laser according to any one of claims 1-5, characterized in that, Yb:Er:YAG blocks are prepared by the following steps: M1, according to the formula, take ytterbium oxide, erbium oxide, yttrium oxide and aluminum oxide, mix and ball mill into wet material; M2, wet material is dried and dry-pressed; drying temperature 75℃~85℃, dry pressing pressure 10 MPa~50MPa; M3, solid-phase reaction at 1400℃~1600℃ for 8 to 12 hours, to obtain Yb:Er:YAG blocks.

7. The Yb:Er:YAG crystal for a 2940nm laser according to claim 6, characterized in that, The purity of the ytterbium oxide is ≥99.999 wt%, the erbium oxide is ≥99.999 wt%, the yttrium oxide is ≥99.999 wt%, and the aluminum oxide is ≥99.999 wt%.

8. A method for preparing Yb:Er:YAG crystal according to any one of claims 1-7, comprising the following steps: S1, load the Yb:Er:YAG material block into the crucible, and then load the crucible into the crystal pulling furnace; S2, crystal pulling is performed under an atmosphere, with a growth rate of 0.5 mm / h ~ 1.5 mm / h and a rotation speed of 8 rpm ~ 15 rpm; S3. After crystal pulling, anneal at 1200℃~1300℃ for 20~35 hours, and then cool to room temperature at a cooling rate of 0.5°C / min~2°C / min to obtain Yb:Er:YAG crystals.

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