CN110158150B

CN110158150B - ABAlO for active ion doping4Single crystal optical fiber and preparation method and application thereof

Info

Publication number: CN110158150B
Application number: CN201910419165.5A
Authority: CN
Inventors: 贾志泰; 陶绪堂; 张娜; 张健
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2019-05-20
Filing date: 2019-05-20
Publication date: 2021-04-09
Anticipated expiration: 2039-05-20
Also published as: CN110158150A

Abstract

The invention relates to ABAlO for activating ion doping₄Single crystal optical fiber and preparation method and application thereof, wherein the chemical composition of the optical fiber is CaGdAlO doped with active ions₄The activating ion is Yb³⁺Or Er³⁺And Yb³⁺And (4) double doping. The CGA single crystal optical fiber grown by adopting a laser heating pedestal method belongs to a tetragonal crystal system, has a melting point of 1840 ℃, a wide transmission spectrum and no self-absorption in a visible light band; maximum phonon energy of 618cm^‑1Lower than a portion of the oxide crystals. Combines the excellent thermal property of CGA crystal and the unique large length-diameter ratio of single crystal optical fiber, ABAlO₄The quasi-crystal has excellent application value in ultrafast laser output and mid-infrared wave band.

Description

ABAlO for active ion doping4Single crystal optical fiber and preparation method and application thereof

Technical Field

The invention relates to a novel single crystal optical fiber and a preparation method and application thereof, belonging to the technical field of crystals and devices.

Background

The ultrafast laser has ultrashort pulse and ultrastrong characteristics, and can obtain extremely high peak light intensity with lower pulse energy. Therefore, ultrafast laser crystal materials have become a hot research point in the crystal field. Yb-doped³⁺The ultrafast laser substrate is one of the main development directions in the future laser field, Yb compared with the titanium sapphire laser³⁺The ions can be directly pumped by a commercial LD light source, the energy level structure is simple, the quantum defect is small, and most importantly, the absorption emission spectrum of the ions is wider compared with other active ions. Therefore, more and more research is focused on Yb³⁺A doped ultrafast laser crystal. It is expected to be able to achieve shorter pulse widths, higher energies and wider spectral rangesThe ultrafast laser matrix meets a plurality of new research fields such as ultrafast X-ray spectrum, soft X-ray nonlinear optics, nanoscale imaging, plasma imaging and diagnosis and the like.

Relating to doping Yb³⁺There are also many reports of ultrafast laser crystal of (1), for example: chinese patent document CN 102086531a (application number: 200910200061.1) discloses a wide tuning ultrafast laser crystal material. The composition of the laser crystal material is Yb³⁺Doped bismuth silicate laser crystal (Yb: Bi)₁₂SiO₂₀) Can be obtained by various crystal growth methods such as a pulling method, a Bridgman method and the like. However, since the growth of the BSO crystal is extremely difficult, it is difficult to grow a large-sized high-quality crystal, and the output optical power is low, which limits the application of the crystal.

Mid-infrared band laser light around 3.0 μm is in the strongly absorbing region of water, making this band important in ophthalmology, dentistry and surgery. The band laser has stronger penetrating power to smoke dust and the like, so the high-power mid-infrared laser has a plurality of potential applications in military countermeasure. In addition, the laser in the wave band has extremely important value in the aspects of atmospheric pollution monitoring, ocean detection, basic scientific research and the like. Therefore, the development of the mid-infrared band crystal is of great significance.

ABCO₄The (A ═ Ca, Sr, Ba; B ═ Y and lanthanides; C ═ Al, Gd) series of crystals belong to the tetragonal system with K₂NiF₄The structure is I4/mmm space group. The crystal of the system has relatively high melting point (about 1800 ℃), good physical and chemical properties and high laser damage threshold. In addition, the crystal of the system has the greatest characteristic of disordered structure, can increase the non-uniform broadening of absorption and emission spectrums, and is favorable for realizing tunable or ultrafast laser. But current research on such crystals has focused primarily on conventional bulk crystals. In order to further improve the ultrafast characteristic of the crystal and the output of special wave band, the development of a combined ABCO is urgently needed₄The crystal has excellent thermal property, and the single crystal fiber has unique material with large length-diameter ratio and the preparation technology.

The gallate has volatility and relatively great growth difficulty, and the preparation of single crystal fiber is also very easyIt is difficult. ABAlO of aluminate system₄We have carried out this system for the first time (CaGdAlO) for the easier growth than gallate₄) The growth and optimization of the single crystal optical fiber have the advantages of uniform crystal diameter, smooth and transparent surface, uniform distribution of doped ions and high crystal quality. The single crystal property is characterized by good single crystal property by adopting a Laue diffractometer, the measured absorption and emission spectrum has a half-peak width of 151.88nm, which is far larger than that of the similar crystal. Further, the search for the kind and concentration of the dopant ion is also an important matter for those skilled in the art to study. ABAlO represented by CGA matrix is provided₄Class (CaLaAlO)₄,CaYAlO₄Etc.) has high thermal conductivity and wide emission spectrum, and will have great application value in the fields of ultrafast laser and mid-infrared band fiber laser. The invention is therefore proposed.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides ABAlO for activating ion doping₄A single crystal optical fiber, a preparation method and an application thereof; especially Yb³⁺Doped CGA single crystal fiber (Yb: CGA), and Er³⁺、Yb³⁺Double-doped CGA single crystal fiber (Er, Yb: CGA).

The technical scheme of the invention is as follows:

ABAlO for activating ion doping₄A single crystal optical fiber having a chemical composition of CaGdAlO doped with active ions₄(hereinafter abbreviated as CGA) and the activating ion is Yb³⁺Or Er³⁺、Yb³⁺Two ions.

According to the invention, it is preferred when the activating ion is Yb, based on the molar content of the total starting material³⁺The doping molar ratio of the active ions is as follows: 4% Yb₂O₃(ii) a When the active ion is Er³⁺、Yb³⁺In the case of two ions, the doping molar ratio of the active ions is 1% Yb₂O₃And 20% Er₂O₃。

According to the present invention, preferably, the optical fiber has a circular cross section.

According to the present invention, it is preferable that the optical fiber has a diameter of 1 to 1.5 mm;

preferably, the length of the optical fiber is more than or equal to 12 cm.

According to the invention, the length-diameter ratio of the optical fiber is preferably more than or equal to 100: 1.

According to the invention, the CGA single crystal is preferably tetragonal, with a melting point of 1840 ℃ and a density of 5.9535g/cm³Thermal conductivity (5.3) w/(m.K), refractive index @1013nm (1.91), maximum phonon energy 618cm^-1The CGA crystal transmits in the spectral range (227-.

The CGA single crystal optical fiber doped with the active ions can be grown by a Laser Heating Pedestal (LHPG) method.

According to the invention, the preparation method of the CGA single crystal optical fiber doped with the active ions comprises the following steps:

preparing a doped CGA source rod;

laser melting of the doped CGA source rod;

and (3) neck-collecting, shouldering, isometric growth and stripping of the doped CGA seed crystal in the doped CGA molten material.

According to the method for manufacturing an optical fiber of the present invention, preferably, the crystal extraction step further includes a high temperature annealing step.

According to the preparation method of the optical fiber, preferably, in the step of laser melting of the doped CGA source rod, the center of the source rod is placed at the laser center for melting, and through neck closing, shoulder placing and equal diameter growth, at the power of 70-80W, the pulling speed is 0.05-0.2mm/min, the feeding speed is 0.0125-0.05mm/min, and the ratio of the pulling speed to the feeding speed is 4:1, crystals can stably grow. When the crystal grows to the required length in an equal diameter way, the feeding is stopped, and the crystal is lifted off.

According to the preparation method of the optical fiber, preferably, in the high-temperature annealing step, the crystal is subjected to medium-high temperature annealing treatment in the air, the annealing temperature is 900-.

According to the preparation method of the optical fiber, a preferable scheme comprises the following steps:

(1) with high purity Al₂O₃、CaCO₃、Gd₂O₃、Er₂O₃、Yb₂O₃The powder is taken as raw material and mixed according to the stoichiometric ratio to respectively obtain Yb doped with 4 percent of Yb₂O₃CGA powder of (1%) and Yb doped with₂O₃And 20% Er₂O₃The CGA powder of (4); then putting the mixture into a mixer for full mixing for 48h, pressing the raw materials into a cylinder shape by a hydraulic press, calcining the raw materials in a corundum crucible at 900 ℃ for 10h by a sintering furnace, and discharging CO₂Heating to 1400 ℃, and fully calcining for 30h to obtain the CGA polycrystal material doped with active ions; obtaining seed crystals and source rods with uniformly distributed active ions;

the sintering temperature and the holding time in the step can be adjusted according to the material and the doping ion species and concentration of the source rod and the size of the raw material rod, and the aim is to obtain high-quality seed crystals and source rods with uniform diameter and uniformly distributed doping.

(2) Crystal growth

a. Cleaning the furnace chamber and the laser reflector, modulating the light path uniformly, fixing the prepared source rod on the feeding device, and fixing the prepared seed crystal on the upper pulling device; increasing the power of the laser to make the focus of the laser fall on the center of the source rod, so that the source rod is uniformly heated to form a melting zone with a stable shape, and keeping the temperature for 6-8 min;

b. adjusting the position of the seed crystal to enable the seed crystal to be in contact with the melting zone and be positioned in the center of the melting zone, adjusting the heating power parameter to enable the melting zone and the growth interface to be stable, starting the pulling device, gradually increasing the power, and performing neck collection; carrying out shouldering and equal-diameter growth; upper pulling speed in the growth process: 0.05-0.2mm/min, lower feed rate: 0.0125-0.05mm/min, the ratio of lifting speed to feeding speed is 4: 1; closing the feeding device, and continuing pulling to pull off the crystal;

c. after the crystal growth is finished, reducing the laser power at the speed of 5-40W/min, closing the laser, and then opening the growth furnace after flowing a flowing atmosphere for 5-12 min;

d. after the growth is finished, the crystal is taken down from the upper pulling device, and medium-high temperature annealing treatment is carried out in the air, so that the thermal stress in the crystal is eliminated, and the cracking is prevented.

The active ion doped CGA single crystal optical fiber has a melting point as high as 1840 ℃, is a tetragonal system, has better strength, hardness, thermal conductivity, wear resistance and corrosion resistance, and is an ideal material for laser crystals.

The CGA single crystal fiber is a disordered crystal, and the absorption and emission spectrums of the active ions are usually subjected to non-uniform broadening under the action of a disordered lattice field, so that the pumping and mode locking processes of ultrafast laser are facilitated. The crystal is colorless and transparent, has wide transmission spectrum and has no self-absorption in visible light wave band; maximum phonon energy of 618cm^-1Lower than a portion of the oxide crystals. The unique large length-diameter ratio of the single crystal optical fiber is combined, the thermal management capability of the laser is greatly improved, the heat dissipation problem of the laser is favorably solved, the structure of the laser is more compact, and the development trend of miniaturization and integration of the laser is met. Yb of³⁺The doped CGA can be directly pumped by a commercial LD light source, has simple energy level structure and small quantum loss, and most importantly has wider absorption emission spectrum compared with other active ions. Yb of³⁺、Er³⁺The co-doped CGA can realize laser output of a 3.0um waveband and becomes an excellent host material of a mid-infrared laser. And ABAlO represented by CGA substrate₄Class (CaLaAlO)₄,CaYAlO₄Etc.) has high thermal conductivity and wide emission spectrum, and will have great application value in the fields of ultrafast laser and mid-infrared band fiber laser.

The invention has the following characteristics and beneficial effects:

1. the invention utilizes the laser heating base technology to obtain the CGA single crystal optical fiber doped with active ions, the diameter of the optical fiber is within the range of 1-1.5mm, the length of the optical fiber reaches more than 12cm, the optical fiber has a great aspect ratio, the crystal diameter is uniform, the surface is smooth, the crystal is transparent, the doped ions are uniformly distributed, and the crystal quality is high. Is a brand new ultrafast laser crystal material with excellent performance.

2. Compared with other materials, the CGA single crystal optical fiber prepared by the invention has the following advantages: transparent filmThe over-spectrum is wide, and self-absorption is avoided in a visible light band; maximum phonon energy of 618cm^-1Lower than most oxide crystals. The crystal has excellent thermal properties and excellent thermal management properties of the optical fiber structure.

3. The invention is advantageous in Yb₂O₃(molar ratio: 4%), and Yb₂O₃(molar ratio 1%) and Er₂O₃The CGA single crystal optical fiber prepared by taking (the molar ratio is 20%) as the active ion has good spectral characteristics and has great application prospect in the fields of ultrafast laser crystals and 3.0 mu m laser output.

Drawings

FIG. 1 shows a tetragonal phase Yb obtained in example 1 of the present invention³⁺Doped CGA (CaGdAlO)₄) Single crystal fiber photo.

FIG. 2 shows a tetragonal phase Yb obtained in example 2 of the present invention³⁺And Er³⁺Doped CGA (CaGdAlO)₄) Single crystal fiber photo.

FIG. 3 shows a tetragonal phase Yb obtained in example 2 of the present invention³⁺And Er³⁺Doped CGA (CaGdAlO)₄) Absorption spectrum of the wafer.

FIG. 4 shows a tetragonal phase Yb obtained in example 2 of the present invention³⁺And Er³⁺Doped CGA (CaGdAlO)₄) Emission spectrum of the wafer.

FIG. 5 shows a tetragonal phase Yb obtained in example 2 of the present invention³⁺And Er³⁺Doped CGA (CaGdAlO)₄) Upper level lifetime of the wafer.

FIG. 6 shows a tetragonal phase Yb obtained in example 2 of the present invention³⁺And Er³⁺Doped CGA (CaGdAlO)₄) Lower energy level lifetime of the wafer.

FIG. 7 shows a tetragonal phase Yb produced in example 1 of the present invention³⁺Doped CGA (CaGdAlO)₄) The Laue diffraction pattern of a single crystal.

Detailed Description

The present invention is further illustrated by, but not limited to, the following examples.

The source rod and the seed crystal described in the examples were prepared as follows:

with high purity Al₂O₃、CaCO₃、Gd₂O₃、Er₂O₃、Yb₂O₃The powder is used as raw material and is mixed according to a certain stoichiometric ratio. Respectively obtain Yb with a molar ratio of 4%₂O₃、1％Yb₂O₃And 20% Er₂O₃The CGA of (1); then putting the mixture into a mixer to be fully mixed for 48 hours, pressing the raw materials into compact round rods by using an isostatic press, calcining the round rods in a corundum crucible at 900 ℃ for 10 hours by using a sintering furnace, and discharging CO₂And then heating to 1400 ℃ and fully calcining for 30h to obtain the CGA polycrystal material, and obtaining seed crystals and source rods with uniformly distributed active ions.

Example 1

Yb-doped₂O₃The preparation method of the CGA single crystal optical fiber comprises the following steps:

(1) selection and treatment of source rods and seed crystals

Preparing a doped CGA (Yb) with the diameter of 2mm₂O₃The molar ratio is 4 percent) is used as a raw material and seed crystal, and the raw material and the seed crystal are fixed on the Al with the groove by high-temperature ceramic glue₂O₃Dried on the rod for 6h at 70 ℃.

(2) Crystal growth

a. Cleaning the furnace chamber and the laser reflector, modulating the light path uniformly, fixing the prepared source rod on the feeding device, and fixing the prepared seed crystal on the upper pulling device; increasing the power of a laser to 60W to melt the material rod, enabling the focal point of the laser to fall on the center of the material rod to obtain uniform heating, continuously increasing the power to 72W to form a stable hemispherical melting zone, and keeping the temperature constant for 8 min;

b. adjusting the position of the seed crystal to enable the seed crystal to be in contact with the melting zone and be positioned in the center of the melting zone, adjusting the heating power parameter to enable the melting zone and the growth interface to be stable, starting the pulling device, gradually increasing the power, and performing neck closing, shoulder setting and equal-diameter growth; upper pulling speed in the growth process: 0.2mm/min, lower feed rate: 0.05 mm/min; the crystal has stable diameter and proper length. Closing the feeding device, and continuing pulling to pull off the crystal;

c. after the crystal growth is finished, reducing the laser power at the rate of 20W/min, turning off the laser, and then opening the growth furnace after flowing a flowing atmosphere for 5-12 min;

d. after the growth is finished, the crystal is subjected to medium-high temperature annealing treatment in the air to eliminate the thermal stress in the crystal and prevent cracking. The specific annealing procedure is as follows: heating the grown doped CGA single crystal optical fiber to 1400 ℃ in a sintering furnace, keeping the temperature for 24 hours, and then slowly cooling to room temperature for 20 hours.

Example 2

Yb-doped₂O₃、Er₂O₃The preparation method of the CGA single crystal optical fiber comprises the following steps:

(1) selection and treatment of source rods and seed crystals

Prepared CGA (Yb) doped with 2mm diameter₂O₃1% by mole, Er₂O₃The molar ratio is 20 percent) of the material rods are used as raw materials and seed crystals, and the raw materials and the seed crystals are fixed on the Al with the grooves by high-temperature ceramic glue₂O₃Dried on the rod for 6h at 70 ℃.

(2) Crystal growth

a, cleaning a furnace chamber and a laser reflector, and uniformly modulating a light path. The prepared source rod is fixed on the feeding device, and the prepared seed crystal is fixed on the upper pulling device. Increasing the power of a laser to 65W to melt the material rod, enabling the focal point of the laser to fall on the center of the material rod to obtain uniform heating, continuously increasing the power to 80W to form a stable hemispherical melting zone, and keeping the temperature constant for 8 min;

b. adjusting the position of the seed crystal to enable the seed crystal to be in contact with the melting zone and be positioned in the center of the melting zone, adjusting the heating power parameter to enable the melting zone and the growth interface to be stable, starting the pulling device, gradually increasing the power, and performing neck closing, shoulder setting and equal-diameter growth; upper pulling speed in the growth process: 0.1mm/min, lower feed rate: 0.025 mm/min; the crystal has stable diameter and proper length. Closing the feeding device, and continuing pulling to pull off the crystal;

c, after the crystal growth is finished, reducing the laser power at the speed of 10W/min, closing the laser, and then opening the furnace after flowing a flowing atmosphere for 15 min.

d, after the growth is finished, carrying out medium-high temperature annealing treatment on the crystal in the air to eliminate the thermal stress in the crystal and prevent cracking. The specific annealing procedure is as follows: heating the grown doped CGA single crystal optical fiber to 1400 ℃ in a sintering furnace, keeping the temperature for 48h, and then slowly cooling to room temperature for 20 h.

Example 3

Yb-doped₂O₃,Er₂O₃The preparation method of the CGA single crystal optical fiber comprises the following steps:

(1) selection and treatment of source rods and seed crystals

(2) Crystal growth

b. adjusting the position of the seed crystal to enable the seed crystal to be in contact with the melting zone and be positioned in the center of the melting zone, adjusting the heating power parameter to enable the melting zone and the growth interface to be stable, starting the pulling device, gradually increasing the power, and performing neck collection; carrying out shouldering and equal-diameter growth; upper pulling speed in the growth process: 0.05mm/min, lower feed rate: 0.0125 mm/min; the crystal has stable diameter and proper length. Closing the feeding device, and continuing pulling to pull off the crystal;

Comparative example 1

As described in example 1, except that:

the pulling speed in the growth process in the step (2) b is as follows: 0.2mm/min, the feeding speed is also 0.2 mm/min. The crystal diameter is too coarse, the stress is too large, and the crystal is cracked.

Comparative example 2

As described in example 1, except that:

and (3) in the annealing process in the step (2), heating to 1000 ℃, keeping the temperature for 24 hours, and then slowly cooling to room temperature for 20 hours. The sintering temperature is too low, the thermal stress is large, and the surface of the crystal has micro-cracks, so that the quality of the crystal is influenced.

Comparative example 3

As described in example 2, except that:

the upper part pulling speed in the growth process of the step (2) b is as follows: 0.2mm/min, the feeding speed is 0.05 mm/min. The pulling rate is too high, resulting in slight cracking of the grown crystal.

Comparative example 4

As described in example 2, except that:

and (3) in the annealing process in the step (2), heating to 1400 ℃, keeping the temperature for 24 hours, and then slowly cooling to room temperature for 20 hours. Even though the same sintering procedure as in example 1 was used, since the doping ion concentration was too high (Yb)₂O₃Doping molar ratio of 1%, Er₂O₃Doping molar ratio 20%), cracking still occurred.

Comparative example 5

As described in example 3, except that:

the pulling speed in the growth process in the step (2) b is as follows: 0.05mm/min and the feeding speed is also 0.025 mm/min. According to the following steps: 1, the diameter is larger and fine cracks appear.

Comparative example 6

As described in example 3, except that:

the pulling speed in the growth process in the step (2) b is as follows: 0.05mm/min, and the feeding speed is also 0.05 mm/min. Even though the growth rate is slow, the diameter is too large to cause cracking.

Test example 1

The products obtained in examples 1 to 3 and comparative examples 1 to 6 were tested for physical properties as shown in Table 1.

TABLE 1

Number/item	Fusion furnacePoint/. degree.C	Transverse sectionNoodleShape ofForm of	Straight barDiameter of a pipe	Crack (crack)Grain patternIn a state of being immersed in
					Practice ofExample (b) 1	1841	Circular shape	1mm	Is free of
Practice ofExample (b) 2	1845	Circular shape	1mm	Is free of
					Practice ofExample (b) 3	1842	Circular shape	1mm	Is free of
Comparison ofExample (b) 1	1840	Cracking of	2mm	MacroApparent cracking
					Comparison ofExample (b) 2	1841	Circular shape	1mm	MacroApparent cracking
Comparison ofExample (b) 3	1840	Circular shape	1mm	Light and slightCracking of
					Comparison ofExample (b) 4	1841	Circular shape	1mm	Light and slightCracking of
Comparison ofExample (b) 5	1842	Circular shape	1.414mm	Light and slightCracking of
					Comparison ofExample (b) 6	1839	Cracking of	2mm	MacroApparent cracking

As can be seen from Table 1, the diameter of the CGA single crystal optical fiber doped with active ions prepared in the embodiments 1, 2 and 3 of the invention is uniform, the length is more than 12cm, and the aspect ratio is more than or equal to 100: 1.

Comparing example 1 with comparative example 1, and example 3 with comparative examples 5 and 6, it was found that when the crystal diameter was too large, cracking of the crystal was also caused, and the larger the diameter was, the more severe the cracking was. Analysis of example 1 compared to comparative example 4, when the dopant ion concentration is too high, the growth rate should be decreased and the annealing time should be increased. By analyzing the example 1 and the comparative example 2, the annealing temperature is not properly controlled, and the stress is large, so that the cracking can be caused.

Test example 2

The absorption spectrum of the Yb, Er: CGA crystal obtained in example 2 at a wavelength band of 1.2-2.6um was tested at room temperature. The samples were Φ 2 x 2mm wafers, double-sided polished, as shown in fig. 3. The crystal has a characteristic absorption peak near 1.5um, has no obvious absorption peak after 2.0um, and the absorption spectrogram can be in one-to-one correspondence with theoretical results.

The emission spectrum refers to the distribution of fluorescence intensity under excitation of a specific wavelength. The emission spectrum of the Yb, Er: CGA crystal obtained in example 2 was measured at room temperature. The excitation wavelength was 970nm, the test wavelength range was 2450 and 3050nm, the test sample size was Φ 2 × 2mm wafer, the sample was double-side polished, and the results are shown in fig. 4. The emission peak is near 2720nm, and the laser output of the wave band is expected to be realized. The half-peak width is 151.88nm, which is far larger than that of the similar crystal, and the disordered structure of the CGA increases the nonuniform broadening of the spectrum. The disordered structure crystal has great application value in ultrafast laser application.

The upper and lower energy lifetimes of the Yb, Er: CGA crystal prepared in example 2 were measured at room temperature, and as shown in FIGS. 5 and 6, it was found that the upper and lower energy lifetimes increased to 0.55ms and 5.1ms, respectively.

Claims

1. ABAlO for activating ion doping₄A single crystal optical fiber having a chemical composition of CaGdAlO doped with active ions₄(CGA), said activating ion is Er³⁺、Yb³⁺Two ions, based on the molar content of the total raw material, the doping molar ratio of the active ions is 1% Yb₂O₃And 20% Er₂O₃The length-diameter ratio of the optical fiber is more than or equal to 100: 1;

the cross section of the optical fiber is circular, and the diameter of the optical fiber is 1-1.5 mm.

2. Activated ion doped ABAlO according to claim 1₄A single crystal optical fiber, wherein the CGA single crystal is a tetragonal system, has a melting point of 1840 ℃ and a density of 5.9535g/cm³Thermal conductivity (5.3) w/(m.K), refractive index 1.91@1013nm, maximum phonon energy 618cm^-1The CGA crystal transmits in the spectral range of 227 and 714 nm.

3. A method of preparing an active ion doped CGA single crystal optical fiber according to any one of claims 1 to 2, comprising:

preparing a doped CGA source rod;

a step of laser melting of a doped CGA source rod, which is to place the center of the source rod at the center of a laser with the power of 70-80W for melting;

and (3) neck closing, shouldering, isodiametric growth and lifting-off of the doped CGA seed crystal in the doped CGA molten material, wherein the lifting speed is 0.05-0.1 mm/min, the feeding speed is 0.0125-0.025 mm/min, and the ratio of the lifting speed to the feeding speed is 4: 1.

4. The method of claim 3, wherein the step of high temperature annealing is further included after the step of crystal extraction.

5. The preparation method according to claim 4, wherein in the high-temperature annealing step, the crystal is subjected to medium-high temperature annealing treatment in air, the annealing temperature is 1400 ℃, the constant temperature time is 24-48h, and the temperature is reduced at the rate of (1-1.5) DEG C/min after the annealing is finished.

6. Use of the active ion doped CGA single crystal fiber of any one of claims 1-2 as an ultrafast laser crystal and mid-ir band crystal.