CN110760930B

CN110760930B - Alkaline earth metal fluoride laser crystal doped with multiple trivalent modulator ions and preparation method thereof

Info

Publication number: CN110760930B
Application number: CN201911081341.5A
Authority: CN
Inventors: 苏良碧; 李晓辉; 张振; 姜大朋; 吴庆辉; 张中晗; 刘荣荣; 王静雅; 钱小波
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2019-11-07
Filing date: 2019-11-07
Publication date: 2021-10-01
Anticipated expiration: 2039-11-07
Also published as: CN110760930A

Abstract

The invention relates to an alkaline earth metal fluoride laser crystal doped with multiple trivalent modulator ions and a preparation method thereof, wherein the chemical formula of the alkaline earth metal fluoride laser crystal doped with the multiple trivalent modulator ions is Nd³⁺,R³⁺:MeF₂(ii) a Wherein Me is one of Ca, Sr and Ba, and R is³⁺Is Y³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺At least two of them.

Description

Alkaline earth metal fluoride laser crystal doped with multiple trivalent modulator ions and preparation method thereof

Technical Field

The invention relates to a laser crystal material, in particular to an alkaline earth metal fluoride laser crystal doped with various trivalent modulator ions and a preparation method thereof, belonging to the field of artificial laser crystal materials.

Background

The ultrashort laser can create extreme physical conditions, such as ultrastrong electromagnetic field and ultrahigh energy density, and is widely applied to many fields of scientific research and industrial technology, such as particle acceleration, thermonuclear fusion, femtosecond chemistry, ultrafine micromachining, high-density information storage, and the like. As one of the key cores of the ultrafast laser technology, a laser gain medium needs to have a suitable stimulated emission cross section, a long laser upper energy level lifetime, and a wide gain bandwidth.

Nd³⁺Energy level transitions within the 4f shell of the ion are an important source of 1 μm laser light. In Nd³⁺Among the numerous doping matrices, Nd³⁺:YAG、Nd³⁺:YVO₄The crystal has a large emission section and high thermal conductivity, and is an excellent laser material. However, the emission bandwidth of these crystals is very narrow, which limits their application to ultrafast lasers. Fluoride laser crystals are an ideal laser host material because of their high thermal conductivity and broad emission bandwidth.

Due to Nd³⁺Ion in MeF₂Clusters are easily formed in the crystal, so that fluorescence quenching is caused, and the improvement of the fluorescence quantum efficiency is limited. On the contrary, the invention of Chinese patent (patent No. ZL201310027583.2) proposes to add Nd³⁺:MeF₂A modifier ion R is doped into the crystal³⁺(R³⁺Y, La, Gd, Lu or Sc) to break down the structure of the neodymium ion cluster, and also to achieve a range of spectral properties. However, the realization of femtosecond laser requires laser material with broader emission bandwidth and smoother fluorescence spectrum, while Nd is codoped with single modifier ion³⁺,R³⁺:MeF₂The crystal is difficult to realize further regulation and control of the spectrum.

Disclosure of Invention

To overcome the defect of single doping of trivalent conditioning ion pair Nd³⁺:MeF₂The limitation of the regulation and control of the spectral performance of the crystal is realized by adding Nd³⁺:MeF₂Multiple types of trivalent modifier ions are doped in the crystal to grow tri-doped Nd³⁺,R₁ ³⁺,R₂ ³⁺:MeF₂With four doped Nd³⁺,R₁ ³⁺,R₂ ³⁺,R₃ ³⁺:MeF₂Crystal (R)₁ ³⁺、R₂ ³⁺、R₃ ³⁺Are respectively selected from Y³⁺、La³⁺、Gd³⁺、Lu³⁺And Sc³⁺Different kinds of ions) in the crystal, thereby realizing the controllable regulation and control of the absorption, emission spectrum and fluorescence lifetime of the crystal and realizing the designability of the spectrum.

In one aspect, the invention provides an alkaline earth metal fluoride laser crystal doped with multiple trivalent modulator ions, wherein the chemical formula of the alkaline earth metal fluoride laser crystal doped with the multiple trivalent modulator ions is Nd³⁺,R³⁺:MeF₂(ii) a Wherein Me is one of Ca, Sr and Ba, and R is³⁺Is Y³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺At least two of them.

In MeF₂In the crystal, F^-The ions constituting a cubic sublattice, Me²⁺The ions occupy half of the cubic sublattice sites. When doped with Nd³⁺After ionization, Nd³⁺Ionic substitution of Me²⁺Lattice sites of ions, while interstitial fluorine ions F are formed due to charge compensation_i ⁺. Nd composed of trivalent rare earth ions and interstitial fluoride ions³⁺-F_i ⁺The dipoles interact with each other to form agglomerates, so that the energy of the system is reduced. [ Nd ]³⁺-Nd³⁺]The existence of clusters increases Nd³⁺The probability of cross-relaxation between ions, resulting in fluorescence quenching at 1.06 μm. Thus, by incorporating an optically inactive trivalent modulator ion R³⁺To form a new [ Nd ]³⁺-R³⁺]Lattice sites, thereby breaking [ Nd³⁺-Nd³⁺]The role of clustering. In the present invention, MeF is treated on the basis of the above₂The crystal is doped with various types of regulating ions R³⁺(e.g., Y)³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺At least two of which may be sequentially designated as R₁ ³⁺、R₂ ³⁺、R₃ ³⁺… …) to form in the crystalNd³⁺-R₁ ³⁺]、[Nd³⁺-R₂ ³⁺][Nd³⁺-R₁ ³⁺]、[Nd³⁺-R₂ ³⁺]、[Nd³⁺-R₃ ³⁺]And the like. The luminescence centers play a role together in the crystal, so that a 'combination effect' can be formed, the controllable regulation and control of the spectral performance and the fluorescence lifetime of the crystal can be realized, and a smoother emission spectrum and a wider emission bandwidth can be obtained.

Preferably, Nd³⁺The doping concentration of the silicon nitride is 0.1at percent to 1.0at percent; r³⁺The doping concentration of (A) is 0.5at% to 10.0 at%.

Also, preferably, when R is³⁺Is selected from Y³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺In two of (1), each R³⁺The doping concentration of the silicon nitride is 0.5at percent to 10.0at percent; preferably, R³⁺The total doping concentration of (2) is 5 at%.

Also, preferably, when R is³⁺Is selected from Y³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺In three of (1), each R³⁺The doping concentration of the silicon nitride is 0.5at percent to 10.0at percent; (ii) a Preferably, R³⁺The total doping concentration of (2) is 5 at%.

On the other hand, the invention also provides a preparation method of the alkaline earth metal fluoride laser crystal doped with various trivalent modulator ions, and the raw material NdF is weighed according to the stoichiometric proportion₃、RF₃And MeF₂And growing the alkaline earth metal fluoride laser crystal doped with various trivalent modulator ions by adopting a temperature gradient method.

Preferably, the parameters of the temperature gradient method include: vacuum degree is less than or equal to 10^-3Pa; melting at 1400-1500 ℃; the cooling rate during crystal growth is 1-5 ℃/h; the cooling rate after the growth is 10-30 ℃/h.

Preferably, the parameters of the temperature gradient method further include a crystal growth time of 100 to 300 hours.

Preferably, the raw materials0.5-2 wt% of PbF is also added₂Used as an oxygen scavenger.

Preferably, a graphite porous crucible is adopted in the growth process of the temperature gradient method.

Has the advantages that:

in the invention, the prepared alkaline earth metal fluoride crystal material is doped with various modifier ions, and various formed luminescence centers can generate a combined effect, thereby realizing the controllable regulation and control of spectral performance and fluorescence life, and simultaneously obtaining a smoother emission spectrum, which is very beneficial to the output of ultrafast laser.

Drawings

FIG. 1 is a graph of 0.5% Nd, 2.5% Y, 2.5% Gd: CaF prepared in example 1₂Crystals with 0.5% Nd, 5% Y CaF₂Crystal, 0.5% Nd, 5% Gd CaF₂A comparison graph of the room temperature emission spectrum of the crystal;

FIG. 2 shows the results of example 2 with 0.5% Nd, 2.5% Lu, 2.5% Gd: CaF₂Crystals with 0.5% Nd, 5% Lu: CaF₂Crystal, 0.5% Nd, 5% Gd CaF₂A comparison graph of the room temperature emission spectrum of the crystal;

FIG. 3 shows 0.5% Nd, 2.5% Lu, 2.5% La: CaF prepared in example 3₂Crystals with 0.5% Nd, 5% Lu: CaF₂Crystal, 0.5% Nd, 5% La: CaF₂A comparison graph of the room temperature emission spectrum of the crystal;

FIG. 4 is the composition of 0.5% Nd, 2.5% Y, 2.5% Gd to CaF prepared in example 1₂Crystals with 0.5% Nd, 5% Y CaF₂Crystal, 0.5% Nd, 5% Gd CaF₂And (3) contrast graph of fluorescence decay curve of the crystal.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

In the present disclosure, tri-doped Nd is prepared by co-doping multiple types of modifier ions³⁺,R₁ ³⁺,R₂ ³⁺:MeF₂And tetra-doped Nd³⁺,R₁ ³⁺,R₂ ³⁺,R₃ ³⁺:MeF₂Crystal (R)₁ ³⁺，R₂ ³⁺，R₃ ³⁺The method comprises the steps of (1) forming different luminescence centers in a crystal by using 3 different modulator ions in Y, La, Gd, Lu and Sc), thereby generating a spectrum 'combination effect', realizing the controllability of the spectral performance and the fluorescence lifetime of the crystal (namely, realizing the regulation and control of the absorption and emission spectrum and the fluorescence lifetime of the crystal), obtaining a smoother emission spectrum (namely, obtaining a near-flat light output with wider fluorescence bandwidth and smoother spectrum type), and being more beneficial to the spectrum of ultrafast laser output.

In an alternative embodiment, Nd³⁺The doping concentration of (A) can be 0.1at% to 1.0 at%.

In alternative embodiments, R₁ ³⁺、R₂ ³⁺The co-doping concentration can be 0.5at% to 10.0 at%. The combination of the two regulating ions can realize the controllable regulation and control of the spectrum shape.

In alternative embodiments, R₁ ³⁺、R₂ ³⁺、R₃ ³⁺The co-doping concentration can be 0.5at% to 10.0 at%. The combination of the three modulator ions can realize further regulation and control of the spectrum shape.

In one embodiment of the invention, the raw materials are weighed according to the molar ratio and put into a mortar to be ground into powder and mixed uniformly, wherein PbF is added₂Used as an oxygen scavenger. Then, an alkaline earth metal fluoride laser crystal doped with a plurality of trivalent modulator ions is grown by a temperature gradient method. The following is an exemplary description of a method of preparing an alkaline earth metal fluoride laser crystal doped with a plurality of trivalent modulator ions.

And (4) batching. The raw material adopted is MeF₂(Me＝Ca，Sr，Ba)、NdF₃、RF₃(R＝Y，La，Gd，Lu，Sc)、PbF₂。PbF₂The oxygen scavenger is used as an oxygen scavenger, and the addition amount of the oxygen scavenger is 0.5-2.0 wt% of the total mass of the raw materials. The raw materials are weighed according to the calculated mass, then put into a mortar to be ground into powder and mixed uniformly.

Growing crystal in a temperature gradient furnace by using a temperature gradient methodAnd (3) a body. Wherein, the crucible is a graphite porous crucible. The vacuum degree in the temperature gradient furnace can be about 10^-3Pa. The material melting temperature can be 1400-1500 ℃. The material melting time can be controlled according to the amount of the raw materials, and generally can be 10-20 hours. The cooling rate during crystal growth can be 1-5 ℃/h. The growth time can be 100-300 hours. The cooling rate after the growth is 10-30 ℃/h. As an example of growing crystals, there are: loading the mixed raw materials into a graphite porous crucible, loading into a temperature gradient furnace, and vacuumizing to 10%^-3And Pa, raising the temperature from room temperature to 200 ℃ after 2h, then preserving the heat for 10h to remove the moisture and air in the raw materials, then raising the temperature to 800 ℃, preserving the heat for 5h, then raising the temperature to 1400-1500 ℃, preserving the heat for melting the materials for 12h, and then slowly lowering the temperature at the speed of 1.5 ℃/h to grow crystals. After 200h the crystal growth was complete and then allowed to cool to room temperature at a rate of 20 ℃/h. Preferably, a temperature gradient method (TGT) is used to grow multiple fluoride laser crystals simultaneously. The crystal growth does not use seed crystal, and a monocrystal is obtained by utilizing a geometric elimination rule, and the whole growth process is carried out under the condition of high vacuum.

Using MeF₂(Me ═ Ca, Sr, or Ba), NdF₃、R₁F₃、R₂F₃、PbF₂(R₁，R₂Two of Y, La, Gd, Lu and Sc) as raw materials, weighing, uniformly mixing, putting the mixture into a graphite porous crucible, slowly heating to 1400-1500 ℃ to melt the raw materials, and then cooling at a certain speed to grow tri-doped Nd³⁺,R₁ ³⁺,R₂ ³⁺:MeF₂And (4) crystals. Wherein, PbF₂The feedstock acts as an oxygen scavenger.

Using MeF₂(Me ═ Ca, Sr, or Ba), NdF₃、R₁F₃、R₂F₃、R₃F₃、PbF₂(R₁，R₂，R₃Three of Y, La, Gd, Lu and Sc) as raw materials, weighing, uniformly mixing, putting the mixture into a graphite porous crucible, slowly heating to 1400-1500 ℃ to melt the raw materials, and then cooling at a certain speed to grow the four-doped Nd³⁺,R₁ ³⁺,R₂ ³⁺,R₃ ³⁺:MeF₂And (4) crystals.

And (5) processing the crystal. The grown crystal was cut into 2.1mm thick wafers, which were then polished on both sides to clear, resulting in 2mm thick samples for absorption, emission spectra and lifetime testing.

And (3) performance testing:

testing the room temperature absorption spectrum of the sample by using an ultraviolet-visible-near infrared spectrophotometer, wherein the testing wavelength range is 200-1200 nm; exciting a room-temperature emission spectrum of the test crystal at 796nm by using a xenon lamp, wherein the test wavelength range is 830-1450 nm; excitation at 796nm, monitoring fluorescence intensity at 1060nm for Nd³⁺Ion(s)⁴F_3/2Fluorescence lifetime of the energy level.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1: 0.5% Nd, 2.5% Y, 2.5% Gd CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、YF₃3.96g、GdF₃5.81g、CaF₂80g、PbF₂1g, grinding into powder in a mortar, mixing well, placing in a graphite porous crucible, growing by temperature gradient method to obtain desired crystal, and maintaining vacuum degree at 10^-3Pa, raising the temperature from room temperature to 200 ℃ after 2h, then preserving the heat for 10h to remove the moisture and air in the raw materials, then raising the temperature to 800 ℃, preserving the heat for 5h, then raising the temperature to 1430 ℃, preserving the heat for melting the materials for 12h, and then slowly lowering the temperature at the speed of 1.5 ℃/h to grow crystals. After 200h the crystal growth was complete and then allowed to cool to room temperature at a rate of 20 ℃/h. The room temperature emission spectrum around 1060nm is shown by the solid line in FIG. 1In this example, 5% of Gd: CaF based on 0.5% of Nd₂In the case of crystals, the emission peak has no obvious peak valley, becomes smoother and has an emission bandwidth of 33.9 nm. The fluorescence decay curve is shown in FIG. 4, and the average fluorescence lifetime is calculated to be 458. mu.s by the integration method.

Example 2: 0.5% of Nd, 2.5% of Lu, 2.5% of Gd, and CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、LuF₃6.29g、LaF₃5.81g、CaF₂80g、PbF₂1g of the crystal is ground into powder in a mortar and fully mixed evenly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method, wherein the growth process is the same as that of the example 1. The emission spectrum at room temperature around 1060nm is shown by the solid line in FIG. 2, and has a ratio of 0.5% Nd, 5% Lu: CaF₂The crystal has wider emission bandwidth and smooth spectral shape, the emission bandwidth is 33.6nm near 1060nm, and the average fluorescence lifetime is 422 mus.

Example 3: 0.5% of Nd, 2.5% of Lu, 2.5% of La and CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、LuF₃6.29g、LaF₃5.31g、CaF₂80g、PbF₂1g of the crystal is ground into powder in a mortar and fully mixed evenly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method, wherein the growth process is the same as that of the example 1. The emission spectrum at room temperature around 1060nm was shown by the solid line in FIG. 3, and the emission spectrum became flatter, with an emission bandwidth around 1060nm of 32.4nm and a mean fluorescence lifetime of 395. mu.s.

Example 4: 0.5% Nd, 2.5% Y, 2.5% La CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、YF₃3.96g、LaF₃5.31g、CaF₂80g、PbF₂1g of the crystal is ground into powder in a mortar and fully mixed evenly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method, wherein the growth process is the same as that of the example 1. The emission bandwidth of the fluorescent material around 1060nm is 33.5nm and the average fluorescence lifetime is 415 mus.

Example 5: 0.5% Nd, 2.5% Y, 2.5% Lu: CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、YF₃3.96g、LuF₃6.29g、CaF₂80g、PbF₂1g of the crystal is ground into powder in a mortar and fully mixed evenly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method, wherein the growth process is the same as that of the example 1. The emission bandwidth of the fluorescent material around 1060nm is 30.3nm and the average fluorescence lifetime is 386 mu s.

Example 6: 0.5% of Nd, 2.5% of La, 2.5% of Gd, and CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、LaF₃5.81g、GdF₃6.29g、CaF₂80g、PbF₂And 1g of the crystal is ground into powder in a mortar and fully mixed uniformly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method. The emission bandwidth around 1060nm was measured to be 33.5nm and the mean fluorescence lifetime was 468. mu.s.

Example 7: 0.5% of Nd, 2.5% of La, 2.5% of Sc and CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、LaF₃5.31g、ScF₃2.76g、CaF₂80g、PbF₂1g, grinding into powder in a mortar, fully mixing uniformly, placing the powder in a graphite porous crucible, and growing by adopting a temperature gradient method to obtain the required crystal, wherein the growth process is the same as that of example 1. The emission bandwidth of the fluorescent material around 1060nm is 31.7nm and the average fluorescence lifetime is 378 mus.

Example 8: 0.5% of Nd, 2.5% of Gd, 2.5% of Sc and CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.09g、LaF₃5.81g、ScF₃2.76g、CaF₂80g、PbF₂1g of the crystal is ground into powder in a mortar and fully mixed evenly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method, wherein the growth process is the same as that of the example 1. The average fluorescence of the fluorescent material is measured to be 32.9nm of emission bandwidth around 1060nmThe optical lifetime was 427 μ s.

Example 9: 0.5% of Nd, 2% of Y, 1% of Lu, 2% of La and CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.20g、YF₃3.48g、LuF₃2.76g、LaF₃4.67g、CaF₂87.90g、PbF₂1g of the crystal is ground into powder in a mortar and fully mixed evenly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method, wherein the growth process is the same as that of the example 1. The emission bandwidth around 1060nm was 32.4nm and the mean fluorescence lifetime was 432. mu.s.

Example 10: 0.5% Nd, 1% Y, 1% Lu, 3% La: CaF₂Growth of crystals

NdF is weighed according to the chemical formula₃1.19g、YF₃1.73g、LuF₃2.75g、LaF₃6.96g、CaF₂87.38g、PbF₂1g of the crystal is ground into powder in a mortar and fully mixed evenly, the powder is placed in a graphite porous crucible, and the required crystal is obtained by adopting a temperature gradient method, wherein the growth process is the same as that of the example 1. The emission bandwidth around 1060nm was 31.6nm and the mean fluorescence lifetime was 433 mus.

Table 1 shows the components and performance parameters of the alkaline earth metal fluoride laser crystal doped with various trivalent modifier ions prepared according to the present invention:

the test result shows that the crystal grown by the embodiment has adjustable absorption, emission spectrum and fluorescence life, the emission spectrum becomes smoother, and the output of femtosecond laser is expected to be realized.

Finally, it should be noted that the above embodiments are only detailed descriptions of specific implementations of the present invention, and the present invention is not limited to the above described specific embodiments. Equivalent alterations and modifications made by the above-described persons skilled in the art are all within the scope of the invention.

Claims

1. An alkaline earth metal fluoride laser crystal doped with multiple trivalent modulator ions, characterized in that the chemical formula of the alkaline earth metal fluoride laser crystal doped with multiple trivalent modulator ions is Nd³⁺, R³⁺:MeF₂(ii) a Wherein Me is one of Ca, Sr and Ba, and R is³⁺Is Y³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺At least two kinds of (B), Nd³⁺The doping concentration of the silicon nitride is 0.1at percent to 1.0at percent;

when R is³⁺Is selected from Y³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺In two of (1), each R³⁺The doping concentration of the silicon nitride is 0.5at percent to 2.5at percent;

or, when R is³⁺Is selected from Y³⁺、La³⁺、Gd³⁺、Lu³⁺、Sc³⁺In three of (1), each R³⁺The doping concentration of (A) is 0.5at% to 3 at%.

2. The method for preparing the alkaline earth metal fluoride laser crystal doped with multiple trivalent dopant ions according to claim 1, wherein the raw material NdF is weighed according to the stoichiometric ratio₃、RF₃And MeF₂And growing the alkaline earth metal fluoride laser crystal doped with various trivalent modulator ions by adopting a temperature gradient method.

3. The method according to claim 2, wherein the parameters of the temperature gradient method include: vacuum degree is less than or equal to 10^-3Pa; melting at 1400-1500 ℃; the cooling rate during crystal growth is 1-5 ℃/h; the cooling rate after the growth is 10-30 ℃/h.

4. The method according to claim 3, wherein the parameters of the temperature gradient method further include a crystal growth time of 100 to 300 hours.

5. The preparation method according to claim 2, wherein 0.5-2 wt% of PbF is further added to the raw materials₂Used as an oxygen scavenger.

6. A production method according to any one of claims 2 to 5, characterized in that a graphite porous crucible is used in the growth process of the temperature gradient method.