Visible laser materials and laser devices

Abstract

To provide a visible range laser material which is capable of oscillating and amplifying a short pulse in a plurality of wavelengths in a visible range, and which makes it possible to obtain ultraviolet and deep ultraviolet continuous laser beams and short pulse laser beam by a single wavelength conversion (twice harmonic), thereby improving energy conversion efficiency.SOLUTION: The invention is a visible range laser material containing an alkali earth metal fluoride, Pr, and at least one of rare earth elements selected from the group consisting of Y, La, Gd and Lu. The invention is also a visible range laser material containing an alkali earth metal fluoride and Tb.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a visible laser material and a method for producing the same. [Background technology]

[0002] Microfabrication using lasers has progressed rapidly in recent years, and important technical issues include increasing the output of visible to ultraviolet lasers with high processing efficiency and shortening the pulse width for microfabrication. Attempts have been made to solve this issue by using harmonic conversion (2nd to 4th harmonics) of solid-state or fiber lasers in the near-infrared region (wavelength approximately 1 μm) that use Nd or Yb as light-emitting elements, but this has not been sufficient for industrial use in terms of improving the energy conversion efficiency of the laser device and making the system more compact.

[0003] Additionally, in the fields of dermatology and beauty, ruby ​​lasers (wavelength 694 nm) and alexandrite lasers (wavelength 755 nm) are used, taking advantage of the laser absorption properties of melanin and oxidized hemoglobin in capillaries. However, because these lasers are three-level systems, they are pulse-excited by a flash lamp, and there is little freedom in adjusting the oscillation pulse width and pulse energy.

[0004] Light-emitting elements for visible lasers include Dy, Pr, Tb, etc. In order to improve the light-emitting efficiency required for laser oscillation, fluoride crystals have been studied as a base material to which light-emitting elements are added (Non-Patent Documents 1 to 3), but these laser materials have a narrow fluorescence spectrum width and are not suitable for high-output operation of short pulses of picoseconds to subpicoseconds.

[0005] Patent Documents 1 to 3 disclose fluoride crystals doped with trivalent Pr ions, but do not examine the use of such crystals as materials for achieving high-output, short-pulse visible lasers.

[0006] As a measure to broaden the fluorescence spectrum, AlF 3Although fluoride glasses such as those based on the fluoride-based fluoride glass have been developed (Non-Patent Document 4), they are used as fiber lasers due to their low thermal conductivity, and it has been difficult to achieve high average power operation of the high-power pulses essential for high-speed processing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2013 / 073592 [Patent Document 2] U.S. Patent No. 8,506,844 [Patent Document 3] JP 2006-342051 A [Non-patent literature]

[0008] [Non-Patent Document 1] K.Iijima,et al.,Appl.Opt.,55,7782(2016) [Non-Patent Document 2] Y. Zhang,et al.,Opt.Lett.,44,3665(2019) [Non-Patent Document 3] F.Reichert,et al.,Opt.Exp.,20,20387(2012) [Non-Patent Document 4] J. Nakanishi,et al.,Opt.Lett.36,1836(2011) Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a visible range laser material that can oscillate and amplify short pulses at multiple wavelengths in the visible range, can produce continuous ultraviolet or deep ultraviolet laser light or short pulse laser light in a single wavelength conversion (second harmonic), and can improve energy conversion efficiency. [Means for solving the problem]

[0010] The present invention is as follows. [1] A visible laser material containing an alkaline earth metal fluoride, Pr, and at least one element selected from the group consisting of Y, La, Gd, and Lu among rare earth elements other than Pr (abbreviated as rare earth element).

[0011] [2] The visible laser material according to [1], wherein the Pr content is from 0.5 mol% to 2 mol% based on the total of Pr, the alkaline earth metal, and the rare earth element, and the rare earth element content (mol%) is from 3 to 10 times the Pr content (mol%).

[0012] [3] The alkaline earth metal fluoride is CaF 2 , SrF 2 , and BaF 2 The visible laser material according to [1] or [2], which is at least one selected from the group consisting of:

[0013] [4]Pr ax R a(1-x) Ca (1-a) F (2+a) A layer having a composition of Pr by R b(1-y) Sr (1-b) F (2+b) A layer having a composition of Pr cz R c(1-z) Ba (1-c) F (2+c) The visible laser material according to any one of [1] to [3], comprising at least two layers selected from the group consisting of layers having the following composition: (In the composition formula, R represents a rare earth element; x, y, and z represent the content ratio (molar ratio) of Pr to the total of Pr and R, and may be the same or different; a, b, and c represent the content ratio (molar ratio) of the total of Pr and R fluorides to the total of Pr and R fluorides and alkaline earth metal fluorides, and may be the same or different.)

[0014] [5] A visible laser material containing alkaline earth metal fluoride and Tb.

[0015] [6] The visible laser material according to [5], wherein the Tb content is 5 mol % or more and 20 mol % or less based on the total content of Tb and the alkaline earth metal.

[0016] [7] The visible laser material according to [5] or [6], further containing at least one element selected from the group consisting of Y, La, Gd, and Lu among rare earth elements other than Tb (abbreviated as rare earth element).

[0017] [8] The visible laser material according to [7], wherein the Tb content is from 5 mol% to 20 mol% of the total of Tb, the alkaline earth metal, and the rare earth element, and the rare earth element content (mol%) is from 0.2 to 2 times the Tb content (mol%).

[0018] [9] The alkaline earth metal fluoride is CaF 2 , SrF 2 , and BaF 2 The visible laser material according to any one of [5] to [8], which is at least one selected from the group consisting of:

[0019]

[10] The visible laser material according to any one of [1] to [4] and [7] to [9], wherein the rare earth element is La.

[0020]

[11] A visible laser material comprising a layer having the visible laser material according to any one of [1] to [3] and a layer having the visible laser material according to any one of [5] to

[10] laminated together.

[0021]

[12] A visible laser material, the outer edge of which is covered with a layer (cladding layer) of the visible laser material according to any one of [1] to [3].

[0022]

[13] Provided is a laser device comprising the visible laser material according to any one of [1] to

[12] and operating in a wavelength range of 480 nm to 730 nm.

[0023]

[14] Pr x R (1-x) F 3 (R represents a rare earth element), and preparing a fine powder of an alkaline earth metal fluoride MF 2 (M represents an alkaline earth metal element) x R (1-x) F 3 and a step of sintering the first material powder compact to produce a sintered ceramic.

[0024]

[15] The above Pr x R (1-x) F 3 The step of preparing the fine particle powder of the compound represented by the above Pr x R (1-x) F 3 A method for producing a visible laser material according to

[14] , comprising the step of liquid-phase synthesis of fine particles of a compound represented by the following formula (1):

[0025]

[16] PrF 3 Preparing fine powder and fluoride RF of rare earth element 3 and preparing a fine powder of alkaline earth metal fluoride MF. 2 preparing a fine particle powder of the above PrF 3 A manufacturing method for a visible range laser material, comprising: a step of forming a compact of a second material powder obtained by mixing a fine particle powder, a fine particle powder of a rare earth element fluoride, and a fine particle powder of the alkaline earth metal fluoride; and a step of sintering the compact of the second material powder to produce a sintered ceramic.

[0026]

[17] The above alkaline earth metal fluorides MF2 The step of preparing the fine powder of CaF 2 , SrF 2 , and BaF 2 The method for producing a visible laser material according to any one of

[14] to

[16] , comprising a step of liquid-phase synthesis of fine fluoride powder containing two or more alkaline earth metal fluorides selected from the group consisting of by a coprecipitation method.

[0027]

[18] A mixture of a Pr compound, a rare earth element compound, and an alkaline earth metal compound is mixed with a fluorine compound to produce a Pr alloy containing both Pr and rare earth elements and alkaline earth metal elements. ax R a(1-x) M (1-a) F (2+a) A method for producing a visible range laser material, comprising the steps of: producing a third material powder by liquid phase synthesis of a fluoride fine particle powder having a composition represented by the following formula (I) by a coprecipitation method; forming a compact of the third material powder; and sintering the compact of the third material powder to produce a sintered ceramic.

[0028]

[19] The method for producing a visible laser material according to

[18] , wherein the alkaline earth metal elements are two or more alkaline earth metals selected from the group consisting of Ca, Sr, and Ba.

[0029]

[20] The method for producing a visible laser material according to any one of

[14] to

[19] , wherein the temperature in the sintering step is 850°C or higher and 1000°C or lower, and the time is 1 hour or higher and 10 hours or lower.

[0030]

[21] A method for producing a visible laser material according to any one of

[14] to

[20] , further comprising a step of subjecting the sintered ceramic to high-temperature isostatic pressing, wherein the temperature in the high-temperature isostatic pressing step is 900°C or higher and 1100°C or lower, and the time is 1 hour or higher and 5 hours or lower. Effect of the Invention

[0031] The visible laser material of the present invention, with the above-mentioned configuration, can oscillate and amplify short pulses at multiple wavelengths in the visible range, and can obtain short pulses in the ultraviolet or deep ultraviolet range with one wavelength conversion (double harmonic). As a result, the system efficiency can be improved, and deterioration of the laser output and life due to heat generation and deterioration of the wavelength conversion crystal can be prevented. Furthermore, since it is possible to oscillate a laser with short pulses in a wide wavelength range, the wavelength options according to the application are expanded, making it possible to use it in a wide range of fields. [Brief description of the drawings]

[0032] [Figure 1] The crystal structure of an alkaline earth metal M fluoride is shown. [Diagram 2] This shows an example of a cluster generated when M2+ in the fluoride of alkaline earth metal M shown in FIG. 1 is replaced with Pr3+. [Diagram 3] This shows another example of a cluster formed when M2+ in the fluoride of alkaline earth metal M shown in FIG. 1 is replaced with Pr3+. [Figure 4] FIG. 3 is a schematic diagram of the arrangement of the clusters shown in FIG. 2 in the crystal lattice of an alkaline earth metal fluoride. [Diagram 5] FIG. 4 shows a schematic diagram of the clusters shown in FIG. 3 arranged in a crystal lattice of an alkaline earth metal fluoride. [Figure 6] This represents a cluster obtained by replacing all but one of the Pr3+ atoms in the cluster shown in Figure 2 with R3+ atoms. [Figure 7] This represents a cluster obtained by replacing all but one of the Pr3+ atoms in the cluster shown in Figure 3 with R3+ atoms. [Figure 8] 3 shows the powder X-ray diffraction patterns of PrF3 and LaF3. [Figure 9] 1 illustrates a cross-sectional view of a laminate according to one embodiment of the present invention. [Figure 10] 1 illustrates a cross-sectional view of a visible laser material according to another embodiment of the present invention. [Figure 11] 1 illustrates a cross-sectional view of a visible laser material according to yet another embodiment of the present invention. [Figure 12] 1 shows a photograph of the visible laser material of Example 1. [Figure 13] 13 shows the fluorescence spectrum of the visible laser material shown in FIG. 12. [Figure 14] 13 shows the absorption spectrum of the visible laser material shown in FIG. 12. [Figure 15] 1 shows the fluorescence spectra of visible laser materials of Examples 2 and 3 and Comparative Example 1. [Figure 16] 4 shows the fluorescence spectrum of the visible laser material of Example 4. [Figure 17] 1 is a graph showing the relationship between Pr concentration and fluorescence intensity in Pr,La:SrF2. [Figure 18] 1 is a graph showing the relationship between the La concentration and the fluorescence intensity in Pr,La:SrF2 and Pr,La:CaF2. [Figure 19] 1 shows the fluorescence spectra of visible laser materials of Comparative Example 6 and Examples 11 to 14. [Figure 20] 1 is a graph showing the relationship between the Tb concentration and the fluorescence intensity in Tb,La:CaF2. [Figure 21] 1 is a graph showing the relationship between the La concentration and the fluorescence intensity in Tb,La:CaF2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The present invention will be described below based on the embodiments, but the present invention is not limited to the following embodiments, and can be modified as appropriate within the scope of the above and below, and all of these are included in the technical scope of the present invention. In addition, hatching and component symbols may be omitted in each drawing for convenience, but in such cases, the specification and other drawings should be referred to. Furthermore, the dimensions of various components in the drawings may differ from the actual dimensions, since priority is given to helping understand the features of the present invention.

[0034] The first visible laser material according to an embodiment of the present invention contains a fluoride of an alkaline earth metal element (hereinafter sometimes referred to as M), and contains Pr as well as at least one element selected from the group consisting of Y, La, Gd, and Lu among rare earth elements other than Pr (abbreviated as rare earth element, hereinafter sometimes referred to as R).

[0035] By including alkaline earth metal fluorides, which have high thermal conductivity and are less susceptible to the thermal lens effect, it is possible to achieve continuous excitation and produce a high-output laser. In addition, fluorides have smaller multiphonon relaxation nonradiative transition losses and excited state absorption than oxides, which can improve the luminous efficiency. Furthermore, alkaline earth metal fluorides have the advantage that they are isotropic crystals, making it easy to obtain transparent ceramics.

[0036] By including Pr as a light-emitting element in such an alkaline earth metal fluoride base material, it becomes possible to emit light at multiple wavelengths in the visible range, and a single wavelength conversion (double harmonic) can produce ultraviolet or deep ultraviolet laser light. In addition, because it can be excited by an inexpensive blue semiconductor laser, it is possible to manufacture a compact laser at low cost.

[0037] In this case, by containing at least one rare earth element selected from the group consisting of Y, La, Gd, and Lu, which are optically inactive in the visible range, clustering of Pr ions accompanying charge compensation when replacing divalent alkaline earth metal ions with trivalent Pr ions can be suppressed, and quenching caused by clustering can be prevented. Furthermore, by containing Pr as a light-emitting element and at least one rare earth element selected from the group consisting of Y, La, Gd, and Lu in the base material of the alkaline earth metal fluoride, a wide spectrum width can be obtained, and therefore a short pulse can be achieved.

[0038] Clustering of Pr ions and suppression of clustering by including at least one rare earth element selected from the group consisting of Y, La, Gd, and Lu will be described with reference to Figs. 1 to 7. Fig. 1 shows a fluoride MF of an alkaline earth metal M. 2 Figure 2 shows the crystal structure of M 2+ Pr 3+ Figure 3 shows an example of a cluster generated when replacing 2+ Pr 3+ Figure 4 shows another example of a cluster generated when replacing 2 Fig. 5 shows a schematic diagram of the arrangement of the clusters shown in Fig. 2 in the crystal lattice of MF. 2 Fig. 6 shows a schematic diagram of the cluster shown in Fig. 3 arranged in the crystal lattice of Pr. 3+ Leave one of them and put the other in R 3+ Figure 7 shows the clusters when the clusters shown in Figure 3 are replaced with the clusters shown in Figure 3. 3+ Leave one of them and put the other in R 3+ This represents the cluster when replaced with

[0039] As shown in Figure 1, fluorides MF of alkaline earth metals M 2 has a cubic structure when M is Ca, Sr, or Ba (tetragonal when M is Mg). When divalent M ions are replaced by trivalent Pr ions, the divalent M ion sites are occupied by trivalent Pr ions, and F is charged for charge compensation. i - Ions intercalate into the interstitial sites, and this F i - A cluster is generated in which multiple Pr ions share the same ion. Here, F i - The ions refer to fluorine ions that are interstitial rather than occupying their original lattice sites. Clusters can have a variety of forms, but typically, the Pr clusters shown in Figures 2 and 3 are 6 F 37 and Pr 4 F 26 As shown in Figs. 4 and 5, clusters with the structure of MF 2Clusters are arranged in the crystal lattice of Pr 3+ When photoexcited, the excited Pr 3+ From the adjacent Pr 3+ In response to this phenomenon, strong quenching occurs due to the energy transfer to Pr 3+ Another rare earth that does not receive energy supply from Pr 3+ By arranging it in the vicinity of, it is possible to suppress quenching.

[0040] The rare earth element is at least one selected from the group consisting of Y, La, Gd, and Lu, which are optically inactive in the visible range.

[0041] Among them, the rare earth element is preferably La. 3+ is the fluoride LaF 3 The crystal structure of PrF 3 Since it is the same hexagonal crystal as Pr x La (1-x) F 3 The powder is easy to synthesize, and La 3+ The ionic radius of Pr 3+ The ionic radius of the Pr cluster is close to that of the 3+ Near La 3+ Fig. 8 shows the PrF 3 and LaF 3 The powder X-ray diffraction patterns of PrF are compared. 3 and LaF 3 It can be seen that they have the same crystal structure and almost the same lattice constants.

[0042] In one embodiment of the present invention, the alkaline earth metal fluoride is CaF 2 , SrF 2 , and BaF 2 It is preferable that the metal oxide is at least one selected from the group consisting of CaF 2 , SrF 2 , and BaF 2 CaF is an isotropic crystal, and it is possible to produce transparent ceramics that are not polarization dependent. 2 , SrF2 , and BaF 2 and CaF 2 , SrF 2 , and BaF 2 Two of the above may be combined. The peak of the fluorescence spectrum of the visible laser material shifts depending on the type of alkaline earth metal, so by combining two or more types of alkaline earth metals, the peaks can be added together to expand the spectral width and shorten the pulse. The type of alkaline earth metal to be combined can be selected according to the desired pulse width, but when combining two or more types, CaF 2 and SrF 2 This combination makes it possible to broaden the peak widths around 640 nm and 730 nm. The combination of two or more alkaline earth metal fluorides can be in any content ratio, but CaF 2 and SrF 2 In the case of the combination, the molar ratio of the content of Ca to the total content of Sr, Pr and rare earth elements can be 50:50 to 70:30, and more preferably 60:40 to 65:35. 2 and BaF 2 In the case of the combination, the molar ratio of the Ca content to the total content of Ba, Pr and rare earth elements can be 40:60 to 60:40, and more preferably 45:55 to 55:45. 2 and SrF 2 In the case of this combination, the molar ratio of the content of Ba to the total content of Sr, Pr and rare earth elements can be from 50:50 to 70:30, and more preferably from 50:50 to 55:45.

[0043] In one embodiment of the present invention, the Pr content is preferably 0.5 mol% or more and 2 mol% or less with respect to the total of Pr, alkaline earth metal elements, and rare earth elements, and the rare earth element content (mol%) is preferably 3 times or more and 10 times or less than the Pr content (mol%). The Pr content is more preferably 0.7 mol% or more with respect to the total of Pr, the alkaline earth metal elements, and the rare earth elements, more preferably 0.8 mol% or more, particularly preferably 1.0 mol% or more, and may be 1.2 mol% or more. The Pr content is more preferably 1.8 mol% or less with respect to the total of Pr, the alkaline earth metal elements, and the rare earth elements, more preferably 1.7 mol% or less, and may be 1.6 mol% or less. If the Pr content is 0.5 mol% or more, a sufficient luminescence rate can be ensured. If the Pr content is 2 mol% or less, a transparent ceramic can be obtained without excessively forming clusters. The content (mol%) of the rare earth element is more preferably 4 times or more, more preferably 5 times or more, and may be 6 times or more, the content (mol%) of Pr. The content (mol%) of the rare earth element is more preferably 9 times or less, and more preferably 8 times or less, the content (mol%) of Pr. As described above, the clusters generated by including Pr in the alkaline earth metal fluoride are Pr 6 F 37 and Pr 4 F 26 Since these clusters have structures such as 3+ A rare earth trivalent ion R 3+ In the former structure, Pr 3+ Five times the R 3+ But in the latter structure, Pr 3+ Three times the R 3+ is required. All R 3+ Pr 3+ Since it is not placed in the neighborhood of R 3+ The above-mentioned range is preferable for the content of Pr. If the total content of Pr and rare earth elements exceeds 20 mol %, the crystal structure will be distorted, and there is a risk that a transparent ceramic will not be obtained.

[0044] In one embodiment of the present invention, Prax R a(1-x) Ca (1-a) F (2+a) A layer having a composition of Pr by R b(1-y) Sr (1-b) F (2+b) A layer having a composition of Pr cz R c(1-z) Ba (1-c) F (2+c) (In the composition formula, R represents a rare earth element. x, y, and z represent the content ratio (molar ratio) of Pr to the total of Pr and R, and may be the same or different. a, b, and c represent the content ratio (molar ratio) of Pr and R fluorides to the total of Pr, R fluorides, and alkaline earth metal, and may be the same or different.)

[0045] Figure 9 shows an example of a visible laser material in which the above two layers are stacked. ax R a(1-x) Ca (1-a) F (2+a) and Pr by R b(1-y) Sr (1-b) F (2+b) 9 is shown as an example of a laminate. By laminating layers whose base materials are alkaline earth metal fluorides containing different types of alkaline earth metals, the fluorescence spectra of the different base materials can be added together as shown in FIG. 16, which will be described later, so that the spectral width can be expanded and the pulse can be shortened. Depending on the desired pulse width, the content ratio of each alkaline earth metal in the entire laser material shown in FIG. 9 can be adjusted by selecting the types of alkaline earth metal elements to be combined and adjusting the thickness of each layer in the laminate.

[0046] The thickness ratio of each layer is preferably 20:80 to 80:20, more preferably 30:70 to 70:30, further preferably 40:60 to 60:40, and may be 50:50.

[0047] The second visible laser material according to the embodiment of the present invention contains an alkaline earth metal fluoride and Tb. By containing Tb as a light-emitting element in the alkaline earth metal fluoride base material, it is possible to emit light at multiple wavelengths in the visible range, and ultraviolet or deep ultraviolet laser light can be obtained by one wavelength conversion. In addition, since it can be excited by a blue-green semiconductor laser or the like, a compact laser can be manufactured at low cost.

[0048] The second visible laser material according to the embodiment of the present invention, which contains Tb as a light-emitting element, can emit light in the visible range even without containing any rare earth element other than the light-emitting element. This is because, although clustering occurs when divalent alkaline earth metal ions are replaced with trivalent Tb ions in the same way as when they are replaced with Pr ions, the photoexcited Tb 3+ From adjacent Tb 3+ This is thought to be because the efficiency of energy transfer to is less than that in the case of Pr substitution, and therefore the quenching is not as strong as when Pr is substituted.

[0049] In one embodiment of the present invention, the content of Tb in the second visible laser material is preferably 5 mol% or more and 20 mol% or less with respect to the total of Tb and alkaline earth metals. The content of Tb is more preferably 6 mol% or more with respect to the total of Tb and alkaline earth metals, more preferably 7 mol% or more, particularly preferably 8 mol% or more, and may be 10 mol% or more. The content of Tb is more preferably 18 mol% or less with respect to the total of Tb and alkaline earth metals, more preferably 16 mol% or less, and may be 15 mol% or less. If the lower limit of the content of Tb is within the above range, a sufficient emission rate can be ensured. If the upper limit of the content of Tb is within the above range, excessive cluster formation and crystal distortion can be suppressed, and transparent ceramics can be obtained.

[0050] In one embodiment of the present invention, the second visible laser material may further contain at least one element selected from the group consisting of Y, La, Gd, and Lu among rare earth elements other than Tb (abbreviated as rare earth element). By containing at least one rare earth element selected from the group consisting of optically inactive Y, La, Gd, and Lu, clustering of Tb ions accompanying charge compensation when replacing divalent alkaline earth metal ions with trivalent Tb ions can be suppressed, and quenching caused by clustering can be prevented, so that the luminous efficiency can be further improved. Furthermore, by containing Tb as a luminescent element and at least one rare earth element selected from the group consisting of Y, La, Gd, and Lu in the base material of the alkaline earth metal fluoride, a wide spectrum width can be obtained, so that a short pulse can be achieved. For example, it is considered that adding La, which has a large ionic radius, can expand the emission spectrum width due to appropriate distortion of the crystal structure.

[0051] In the above case, the content of Tb is preferably 5 mol% or more and 20 mol% or less with respect to the total of Tb, alkaline earth metal, and rare earth element, and the content (mol%) of rare earth element is preferably 0.2 times or more and 2 times or less of the content (mol%) of Tb. The content of Tb is more preferably 6 mol% or more with respect to the total of Tb, alkaline earth metal, and rare earth element, more preferably 7 mol% or more, particularly preferably 8 mol% or more, and may be 10 mol% or more. The content of Tb is more preferably 18 mol% or less with respect to the total of Tb, alkaline earth metal, and rare earth element, more preferably 16 mol% or less, and may be 15 mol% or less. If the lower limit of the content of Tb is within the above range, a sufficient luminescence rate can be ensured. If the upper limit of the content of Tb is within the above range, a transparent ceramic can be obtained without forming excessive clusters. The content (mol%) of rare earth element is more preferably 0.3 times or more with respect to the content (mol%) of Tb, more preferably 0.5 times or more, and may be 1 times or more. The content (mol%) of the rare earth element is more preferably 1.8 times or less, further preferably 1.6 times or less, and may be 1.5 times or less, the content (mol%) of Tb. If the content of the rare earth element is within the above range, it is possible to suppress quenching and improve the luminous efficiency, while suppressing distortion of the crystal structure to obtain a transparent ceramic.

[0052] In one embodiment of the present invention, the alkaline earth metal fluoride of the second visible laser material is CaF 2 , SrF 2 , and BaF 2 It is preferable that the metal oxide is at least one selected from the group consisting of CaF 2 , SrF 2 , and BaF 2 CaF is an isotropic crystal, and it is possible to produce transparent ceramics that are not polarization dependent. 2 , SrF 2 , and BaF 2 and CaF 2 , SrF 2 , and BaF 2Two of the above may be combined. The peak of the fluorescence spectrum of the visible laser material shifts depending on the type of alkaline earth metal, so by combining two or more types of alkaline earth metals, the peaks can be added together to expand the spectral width and shorten the pulse. The type of alkaline earth metal to be combined can be selected according to the desired pulse width, but when combining two or more types, CaF 2 and SrF 2 The combination of two or more alkaline earth metal fluorides may be in any content ratio, but CaF 2 and SrF 2 In the case of the combination, the molar ratio of the content of Ca to the total content of Sr, Pr and rare earth elements can be 50:50 to 70:30, and more preferably 60:40 to 65:35. 2 and BaF 2 In the case of the combination, the molar ratio of the Ca content to the total content of Ba, Pr and rare earth elements can be 40:60 to 60:40, and more preferably 45:55 to 55:45. 2 and SrF 2 In the case of this combination, the molar ratio of the content of Ba to the total content of Sr, Pr and rare earth elements can be from 50:50 to 70:30, and more preferably from 50:50 to 55:45.

[0053] One embodiment of the present invention provides a visible laser material in which a layer having the first visible laser material containing Pr and a layer having the second visible laser material containing Tb are laminated. As shown in FIG. 10, in one embodiment of the present invention, Pr ax R a(1-x) M (1-a) F (2+a) and a layer with a composition of Tb by R b(1-y) M (1-b) F (2+b)In the composition formula, R represents a rare earth element, and M represents an alkaline earth metal. x represents the content ratio (molar ratio) of Pr to the total of Pr and R, and is less than 1. y represents the content ratio (molar ratio) of Tb to the total of Tb and R, and is 1 or less. a represents the content ratio (molar ratio) of Pr and R fluorides to the total of Pr and R fluorides and alkaline earth metal fluorides. b represents the content ratio (molar ratio) of Tb and R fluorides to the total of Tb and R fluorides and alkaline earth metal fluorides. By laminating a layer having a first visible range laser material and a layer having a second visible range laser material, the wavelength range that can be covered can be expanded. The thickness ratio of each layer is preferably 20:80 to 80:20, more preferably 30:70 to 70:30, further preferably 40:60 to 60:40, and may be 50:50.

[0054] One embodiment of the present invention provides a visible laser material in which the outer edge of the first visible laser material containing Pr is covered with a layer (cladding layer) of the second visible laser material containing Tb. As shown in FIG. 11, in one embodiment of the present invention, Pr ax R a(1-x) M (1-a) F (2+a) The outer edge of the first visible laser material has a composition of Tb by R b(1-y) M (1-b) F (2+b)It is preferable that the first visible laser material is covered with a layer (cladding layer) of the second visible laser material having the composition. In the composition formula, R represents a rare earth element, and M represents an alkaline earth metal. x represents the content ratio (molar ratio) of Pr to the total of Pr and R, and is less than 1. y represents the content ratio (molar ratio) of Tb to the total of Tb and R, and is 1 or less. a represents the content ratio (molar ratio) of Pr and R fluorides to the total of Pr and R fluorides and alkaline earth metal fluorides. b represents the content ratio (molar ratio) of Tb and R fluorides to the total of Tb and R fluorides and alkaline earth metal fluorides. By covering the first visible laser material with a layer (cladding layer) of the second visible laser material, an amplification medium structure having a function of preventing parasitic oscillation in the 480 nm wavelength band can be obtained, and the amplification efficiency can be improved. The thickness of the second visible laser material that covers the first visible laser material is desirably adjusted so that the transmittance of light in the 480 nm wavelength band is 50% or less.

[0055] The present invention also provides a laser device that includes the first visible laser material described above and operates in a wavelength range of 480 nm to 730 nm. The laser device that includes the first visible laser material described above can perform laser operation (oscillation and amplification) in five wavelength bands in the visible wavelength range of 480 nm to 730 nm, and can obtain ultraviolet to deep ultraviolet laser light by one harmonic conversion. In addition, since the spectral width in each wavelength band is wide, it can be made into a short pulse laser. The present invention further provides a laser device that includes the second visible laser material described above and operates in a wavelength range of 530 nm to 630 nm. The laser device that includes the first visible laser material described above can perform laser operation (oscillation and amplification) in three wavelength bands in the visible wavelength range of 530 nm to 630 nm, and can obtain ultraviolet to deep ultraviolet laser light by one harmonic conversion. In addition, since the spectral width in each wavelength band is wide, it can be made into a short pulse laser.

[0056] The present invention also provides a first method for producing a visible range laser material according to one embodiment of the present invention, the first method for producing a visible range laser material of the present invention comprising the steps of: x R (1-x) F 3 (R represents a rare earth element), a step of preparing a fine powder of an alkaline earth metal fluoride, and x R (1-x) F 3 and mixing fine particle powder of a compound represented by the formula (I) with fine particle powder of the alkaline earth metal fluoride to form a green compact of a first material powder, and sintering the green compact of the first material powder to produce a sintered ceramic.

[0057] In the stage of preparing the fine powder, Pr 3+ and R 3+ Fluoride microcrystals containing Pr and x in the concentration ratio x:(1-x) x R (1-x) F 3 By obtaining Pr x R (1-x) F 3 The fine powder of the first material is mixed with the fine powder of the fluoride of the alkaline earth metal M to obtain a first material powder. The first material powder is molded to form a first material powder compact, which is then sintered to obtain a first material powder compact, as shown in the following formula (1): ax R a(1-x) M (1-a) F (2+a) It is possible to produce transparent ceramics having a composition of: where a is Pr 3+ and R 3+ and M. 2+ Pr when the sum of 3+ and R 3+ The total content ratio (molar ratio) of a(Pr x R (1-x) F 3 ) Fine particles + (1-a)MF 2 Fine particles → Molding → Sintering → Pr ax R a(1-x) M (1-a) F (2+a) Ceramics (1)

[0058] The above Pr x R (1-x) F 3 The step of preparing the fine particle powder of the compound represented by the above Pr x R (1-x) F 3 It is preferable to include a step of synthesizing a fine powder of a compound represented by the following formula (1) by a liquid phase coprecipitation method. This makes it easy to adjust the ratio of Pr to R.

[0059] In the liquid phase synthesis, as shown in the following formula (2), a salt of Pr and a salt of R are reacted with a fluorine compound to give Pr x R (1-x) F 3 The following formula (2) shows the case where chloride is used as the Pr salt and R salt, La is used as R, and potassium fluoride is used as the fluorine compound, but other inorganic salts such as sulfate, nitrate, and carbonate, and organic salts such as acetate and oxalate can also be used as the Pr salt and R salt, and other fluorine compounds such as hydrofluoric acid and sodium fluoride can also be used. xPrCl 3 +(1-x)LaCl 3 +3KF→Pr x R (1-x) F 3 ↓Fine particles +3KCl (2)

[0060] The second method for producing the visible laser material of the present invention is to use PrF 3 Preparing fine powder and fluoride RF of rare earth element 3 and preparing a fine powder of alkaline earth metal fluoride MF. 2 preparing a fine particle powder of the above PrF 3 Fine particle powder and fluoride RF of the above rare earth elements 3 and the above alkaline earth metal fluoride MF 2 and forming a green compact of the second material powder obtained by mixing the first powder with the fine particle powder of the first material. The green compact of the second material is sintered to produce a sintered ceramic.

[0061] In the second manufacturing method of the present invention, as shown in the following formula (3), fluorides of Pr, a rare earth element R, and an alkaline earth metal M are separately prepared, and then mixed in a desired ratio to produce a second material powder, and a compact of the second material powder is formed and sintered to produce Pr. ax R a(1-x) M (1-a) F (2+a) It is possible to produce a transparent ceramic having the composition: where the definitions of a and x are the same as those in the first production method. axPrF 3 Fine particles +a(1-x)RF 3 Fine particles +(1-a)MF 2 Fine particles → Molding → Sintering → Pr ax R a(1-x) M (1-a) F (2+a) Ceramics (3)

[0062] In the first and second manufacturing methods of the present invention, the step of preparing the fine powder of alkaline earth metal fluoride is 2 , SrF 2 , and BaF 2 The method may include a step of liquid-phase synthesis of fine fluoride powder containing two or more alkaline earth metal fluorides selected from the group consisting of:

[0063] The third method for producing the visible range laser material of the present invention is to mix a mixture of a Pr compound, a compound of a rare earth element R, and a compound of an alkaline earth metal M with a fluorine compound, and produce a Pr ax R a(1-x) M (1-a) F (2+a) The method includes the steps of: synthesizing a fluoride fine particle powder having the composition by a coprecipitation method to produce a third material powder; forming a compact of the third material powder; and sintering the compact of the third material powder to produce a sintered ceramic. The definitions of a and x are the same as those in the first manufacturing method.

[0064] The third manufacturing method of the present invention can obtain a precipitate by liquid phase synthesis using a mixture of a Pr compound, a compound of a rare earth element R, a compound of an alkaline earth metal element M, and a fluorine compound, as shown in the following formula (4). In the following formula (4), chlorides are used as the salts of Pr, R, and alkaline earth metal M, La is used as R, and potassium fluoride is used as the fluorine compound, but inorganic salts such as sulfates, nitrates, and carbonates, and organic salts such as acetates and oxalates can also be used as the salts of Pr, R, and alkaline earth metal M, and hydrofluoric acid, sodium fluoride, etc. can also be used as the fluorine compound. axPrCl 3 +a(1-x)RCl 3 +(1-a)MCl 2 +(2+a)KF→Pr ax R a(1-x) M (1-a) F (2+a) ↓Fine particles+(2+a)KCl (4)

[0065] In the first to third production methods of the present invention, the alkaline earth metal fluoride is CaF 2 , SrF 2 , and BaF 2 It is preferable that the fluoride contains two or more alkaline earth metals selected from the group consisting of: 2 and SrF 2 The combination of the above is preferable. By containing two or more alkaline earth metal fluorides, the peaks in the respective fluorescence spectra shown in FIG. 16 described later can be added together, so that the spectral width can be expanded and the pulse can be shortened. The ratio of the alkaline earth metal fluorides to be combined can be determined according to the desired pulse width. CaF 2 and SrF 2 The molar ratio of CaF can be 50:50 to 70:30, and more preferably 60:40 to 65:35. 2 and BaF 2In the case of the combination, the molar ratio of the Ca content to the total content of Ba, Pr and rare earth elements can be 40:60 to 60:40, and more preferably 45:55 to 55:45. 2 and SrF 2 In the case of this combination, the molar ratio of the content of Ba to the total content of Sr, Pr and rare earth elements can be from 50:50 to 70:30, and more preferably from 50:50 to 55:45.

[0066] According to the first to third methods for producing the visible laser material of the present invention, Pr ax R a(1-x) Ca (1-a) F (2+a) A layer having a composition of Pr by R b(1-y) Sr (1-b) F (2+b) A layer having a composition of Pr cz R c(1-z) Ba (1-c) F (2+c) It is possible to manufacture a visible laser material having at least two laminated layers selected from the group consisting of layers having the following compositions. Each layer may be formed by laminating the powder material as it is, or at least two powder materials from the group consisting of the powder material may be molded first and then laminated to form a laminated molded body.

[0067] In the first to third manufacturing methods of the visible laser material of the present invention, the temperature in the sintering step is preferably 850°C or higher and 1000°C or lower, and the time is preferably 1 hour or higher and 10 hours or lower. The sintering temperature is more preferably 880°C or higher, even more preferably 900°C or higher, and may be 920°C or higher, and is particularly preferably 950°C or higher. The sintering temperature is more preferably 990°C or lower, and even more preferably 980°C or lower. By sintering at a temperature lower than the melting point of the crystal (about 1400°C), excessive ion movement during grain growth is suppressed, and Pr 3+ and R 3+ This prevents the Pr from diffusing to distant locations. 3+ In the neighborhood of R 3+ The Pr contained in the alkaline earth metal fluoride can be placed 3+If the sintering temperature is lower than the above range, the grain growth is hindered. If the sintering temperature is higher than the above range, the migration of ions is promoted, and the Pr 3+ and R 3+ There is a risk that the fluorine may diffuse to distant positions. In addition, fluorine may be released, making it difficult to obtain transparent ceramics. The sintering time is more preferably 2 hours or more, and even more preferably 3 hours or more. In addition, the sintering time is more preferably 9 hours or less, and even more preferably 8 hours or less. If the sintering time is within the above range, ceramicization by crystal growth becomes easy, and transparent ceramics can be obtained.

[0068] The first to third manufacturing methods of the first visible laser material according to the embodiment of the present invention preferably further include a step of subjecting the sintered ceramic to high-temperature isostatic pressing. The high-temperature isostatic pressing is so-called hot isostatic pressing. The temperature in the high-temperature isostatic pressing step is preferably 900°C or higher and 1100°C or lower, and the time is preferably 1 hour or higher and 5 hours or lower. The temperature in the high-temperature isostatic pressing is more preferably 920°C or higher, and more preferably 950°C or higher. Also, it is more preferably 1050°C or lower, and even more preferably 1000°C or lower. The time in the high-temperature isostatic pressing is more preferably 1.5 hours or higher, and even more preferably 2 hours or higher. Also, it is more preferably 4.5 hours or lower, and even more preferably 4 hours or lower. By setting the temperature and time in the high-temperature isostatic pressing within the above ranges, it is possible to reduce voids in the ceramic and improve transparency.

[0069] In the first to third manufacturing methods of the present invention, the rare earth element R is at least one rare earth element selected from the group consisting of Y, La, Gd, and Lu, and among them, it is particularly preferable to use La, which has an ionic radius approximately equal to that of Pr and whose fluoride crystal structure is a hexagonal system.

[0070] The first to third manufacturing methods of the present invention can be used to manufacture the visible laser material according to the embodiment of the present invention. According to the manufacturing method of the present invention, it is possible to oscillate and amplify short pulses at multiple wavelengths in the visible range, obtain short ultraviolet or deep ultraviolet pulses in one wavelength conversion (second harmonic), and manufacture a laser with high system efficiency.

[0071] The second visible laser material according to the embodiment of the present invention, which uses Tb instead of Pr, can also be manufactured using the above-mentioned first to third manufacturing methods, except that there are cases in which rare earth elements (other than Tb) are not required to be contained. EXAMPLES

[0072] The present invention will be described below with reference to examples. The present invention is not limited to the following examples, and can of course be modified within the scope of the above and below-described aims, and all such modifications are within the technical scope of the present invention.

[0073] Example 1 Praseodymium acetate was mixed with ultrapure water to obtain a 0.1 mol / L solution, and hydrogen fluoride water (1.2 mol% / L) was added dropwise at a stoichiometric ratio of 1.5 times to the solution to obtain a precipitate of praseodymium fluoride. The precipitate separated from the supernatant by centrifugation was suspended in ultrapure water and dispersed using a homogenizer, and then separated from the supernatant by centrifugation again. This operation was repeated until the ion concentration of the supernatant was 100 ppm or less. The precipitate washed with water by the above method was suspended in ultrapure water and freeze-dried. A 1 mol / L potassium fluoride aqueous solution was added dropwise to a 1 mol / L solution of lanthanum chloride mixed with ultrapure water until the pH value of the reaction solution reached 7, and a lanthanum fluoride precipitate was obtained. Lanthanum fluoride powder was then obtained by the same operation as for praseodymium fluoride. A 1 mol / L potassium fluoride aqueous solution was added dropwise to a 1 mol / L solution of calcium chloride mixed with ultrapure water until the pH value of the reaction solution reached 7, and a calcium fluoride precipitate was obtained. Then, calcium fluoride powder was obtained by the same operation as praseodymium fluoride. The produced praseodymium fluoride, lanthanum fluoride, and calcium fluoride powders were adjusted so that the total of praseodymium, lanthanum, and calcium was 100 mol%, and added to ultrapure water together with a dispersant (Toagosei Co., Ltd. AS-1100), subjected to ultrasonic treatment, and then freeze-dried. 8 wt% of binder (Toagosei Co., Ltd. Aron A-30SL) was added to the dried powder, mixed with an agate mortar and pestle for 20 minutes to granulate, then passed through a sieve with a mesh size of 212 μm, and dried in a vacuum dryer at a constant temperature of 40°C for 18 hours or more. The dried powder was pressed with a uniaxial press and a cold isostatic press (held at 300 MPa for 10 minutes) to produce a pellet-shaped material powder compact. This material powder compact was degreased in an oxygen atmosphere at 400°C for 40 hours, and then dried in a vacuum (10 -3 The sintered ceramics were then subjected to high-temperature isostatic pressing in an argon gas atmosphere at 200 MPa and 1100°C for 3 hours to obtain Pr,La:CaF with a praseodymium content of 1.0 mol% and a lanthanum content of 10 mol% relative to the total of praseodymium, lanthanum, and calcium. 2 A photograph of the obtained ceramics is shown in Figure 12. As shown in Figure 12, the ceramics were transparent.

[0074] The transparent ceramic Pr,La:CaF obtained above 2 The fluorescence spectrum of the obtained transparent ceramics Pr,La:CaF was measured using a high-resolution fluorescence spectrometer (JASCO SS-25), and the absorption spectrum was measured using a spectrophotometer (Hitachi U-4100). The results are shown in Fig. 13 and Fig. 14. 2 It was found that the obtained transparent ceramic Pr,La:CaF can oscillate and amplify in five wavelength bands in the wavelength range from 480 nm to 730 nm, and has a wide fluorescence spectrum width in the 480 nm, 525 nm, and 605 nm bands in particular, and can oscillate and amplify picosecond pulse lasers. 2 The absorption spectrum of has a peak at 442 nm, and it was found that it can be excited by a commercially available blue semiconductor laser.

[0075] Example 2 Strontium fluoride powder, praseodymium fluoride powder (manufactured by Kojundo Chemical Co., Ltd.), and lanthanum fluoride powder (manufactured by Kojundo Chemical Co., Ltd.) prepared in the same manner as in Example 1 were used. The praseodymium fluoride powder, lanthanum fluoride powder, and strontium fluoride powder were adjusted so that the total of praseodymium, lanthanum, and strontium was 100 mol%, and were added to ultrapure water together with a dispersant (Toagosei Co., Ltd. AS-1100), subjected to ultrasonic treatment, and then freeze-dried. 8 wt% of binder (Toagosei Co., Ltd. Aron A-30SL) was added to the dried powder, mixed with an agate mortar and pestle for 20 minutes to granulate, and then sieved with a 212 μm mesh sieve and dried in a vacuum dryer at a constant temperature of 40° C. for 18 hours or more. The dried powder was pressed (held at 300 MPa for 10 minutes) using a uniaxial press and a cold isostatic press to produce a pellet-shaped powder compact. -3 The praseodymium content was 1 mol% and the lanthanum content was 5 mol% relative to the total of the praseodymium, lanthanum, and strontium. 2 Ceramics were obtained.

[0076] The Pr,La:SrF obtained above 2 The fluorescence spectrum of the above was measured using a high-resolution fluorescence spectrometer (JASCO SS-25). The results are shown in FIG. 15. The dashed line in FIG. 15 indicates the ceramic Pr,La:SrF produced in Example 2. 2 From Figure 15, the fluorescence spectrum of the obtained transparent ceramic Pr,La:SrF 2 It was found that the laser was capable of oscillating and amplifying in five wavelength bands in the wavelength region of 480 nm to 730 nm, and that broad peaks in the fluorescence spectrum were observed particularly in the 480 nm, 525 nm, and 605 nm bands, making it possible to oscillate and amplify picosecond pulse lasers.

[0077] Example 3 In the same manner as in Example 2, Pr,La:SrF was prepared, in which the praseodymium content was 1 mol % and the lanthanum content was 10 mol % relative to the total of praseodymium, lanthanum, and strontium. 2 Ceramics were obtained.

[0078] The Pr,La:SrF obtained above 2 The fluorescence spectrum of the above was measured using a high-resolution fluorescence spectrometer (JASCO SS-25). The results are shown in FIG. 15. The thin solid line in FIG. 15 indicates the ceramic Pr,La:SrF produced in Example 3. 2 15 shows the fluorescence spectrum of the laser. Although the intensity was slightly decreased compared to when the lanthanum content was five times that of the praseodymium content, it was found that oscillation and amplification were possible in five wavelength bands in the wavelength range of 480 nm to 730 nm, and that broad peaks in the fluorescence spectrum width were observed especially in the 480 nm, 525 nm, and 605 nm bands, making it possible to oscillate and amplify a picosecond pulse laser.

[0079] Example 4 Using the same manufacturing method as in Examples 2 and 3, ceramics were produced by changing the base material to calcium. Pr,La:CaF 2Using a high-resolution fluorescence spectrometer (JASCO SS-25), the Pr,La:CaF 2 The fluorescence spectrum of the above was measured. The results are shown in FIG. 16. The solid line in FIG. 16 indicates the fluorescence spectrum of the above-produced Pr,La:CaF 2 16 shows the fluorescence spectrum of the ceramics. 2 The fluorescence spectrum of the ceramic is also shown by the dashed line. From FIG. 16, it can be seen that in the vicinity of wavelengths of 640 nm and 725 nm, Pr,La:CaF 2 The fluorescence peak of ceramics is Pr,La:SrF 2 The wavelength shifts to the longer wavelength side compared to ceramics, and it was found that the fluorescence spectrum width can be expanded at wavelengths of around 640 nm and 725 nm by using these two materials in combination.

[0080] Comparative Example 1 In the same manner as in Example 2, Pr,La:SrF was prepared, in which the praseodymium content was 0.2 mol % and the lanthanum content was 5 times (1.0 mol %) the praseodymium content relative to the total of praseodymium, lanthanum, and strontium. 2 Ceramics were obtained.

[0081] Example 5 In the same manner as in Example 2, Pr,La:SrF was prepared, in which the praseodymium content was 0.5 mol % and the lanthanum content was 5 times (2.5 mol %) the praseodymium content relative to the total of praseodymium, lanthanum, and strontium. 2 Ceramics were obtained.

[0082] Example 6 In the same manner as in Example 2, Pr,La:SrF was prepared, in which the praseodymium content was 2.0 mol % and the lanthanum content was 5 times (20 mol %) the praseodymium content relative to the total of praseodymium, lanthanum, and strontium. 2 Ceramics were obtained.

[0083] The Pr,La:SrF obtained in Examples 5 and 6 and Comparative Example 1 2The fluorescence spectrum of the ceramics was measured using a high-resolution fluorescence spectrometer (JAPAN SS-25). From this result and the result of the fluorescence spectrum measured in Example 2, the relationship between the fluorescence intensity at a fluorescence wavelength of 470 to 500 nm and the fluorescence intensity (relative value) at a fluorescence wavelength of 595 to 625 nm and the praseodymium content (mol%) was investigated. The results are shown in FIG.

[0084] Comparative Example 2 A material powder compact was produced in the same manner as in Example 2, except that lanthanum fluoride was not used. This material powder compact was placed in a vacuum (10 -3 The praseodymium content was 1 mol% relative to the total of praseodymium and strontium. 2 Ceramics were obtained.

[0085] Using a high-resolution fluorescence spectrometer (JASCO SS-25), the Pr:SrF 2 The fluorescence spectrum of the ceramic was measured. The results are shown in Fig. 15. The thick solid line in Fig. 15 indicates the Pr:SrF produced in Comparative Example 1. 2 This is the fluorescence spectrum of the ceramics. Since La was not added, quenching due to Pr clustering occurred, and almost no peaks were observed in the fluorescence spectrum. 3+ The addition of Pr 3+ It can be seen that the clustering and quenching of the fluorescein are effectively suppressed.

[0086] Comparative Example 3 In the same manner as in Example 2, Pr,La:SrF having a praseodymium content of 1 mol% and a lanthanum content of 1 mol% relative to the total of praseodymium, lanthanum, and strontium was prepared. 2 Ceramics were obtained.

[0087] Examples 7 and 8 In the same manner as in Example 2, Pr,La:SrF was prepared, in which the praseodymium content was 1 mol % and the lanthanum content was 3 mol % and 7 mol %, respectively, relative to the total of praseodymium, lanthanum, and strontium. 2 Ceramics were obtained.

[0088] Comparative Example 4 The same procedure as in Example 1 was repeated except that the operation for obtaining lanthanum fluoride was not performed, and Pr:CaF, which has a praseodymium content of 1 mol% relative to the total of praseodymium and calcium and does not contain La, was obtained. 2 Ceramics were obtained.

[0089] Comparative Example 5 In the same manner as in Example 1, Pr,La:CaF was prepared, which has a praseodymium content of 1 mol% and a lanthanum content of 1 mol% relative to the total of praseodymium, lanthanum, and calcium. 2 Ceramics were obtained.

[0090] Examples 9 and 10 In the same manner as in Example 1, Pr,La:CaF was prepared, in which the praseodymium content was 1 mol % and the lanthanum content was 3 mol % and 7 mol %, respectively, relative to the total of praseodymium, lanthanum, and calcium. 2 Ceramics were obtained.

[0091] The fluorescence spectra of the ceramics obtained in Comparative Examples 3 to 5 and Examples 7 to 10 were measured using a high-resolution fluorescence spectrometer (JAPAN SS-25), and the relationship between the fluorescence intensity at fluorescence wavelengths of 470 to 500 nm and 595 to 625 nm (relative values) and the lanthanum content (mol%) was investigated in conjunction with the results of Comparative Example 2 and Examples 1 to 4. The results are shown in Figure 18. The relationship between the lanthanum content and the fluorescence lifetime is shown in Table 1.

[0092] [Table 1]

[0093] 18 and Table 1, it can be seen that the emission intensity is weak and the emission lifetime is short when La is not added. In addition, since Pr located near La mainly emits light, the fluorescence lifetime does not depend strongly on the La content, but it can be seen that both the fluorescence intensity and the fluorescence lifetime can be improved by adding La in an amount three times or more the amount of Pr.

[0094] Comparative Example 6 A transparent Tb,La:CaF solution having a terbium content of 1 mol% and a lanthanum content of 10 mol% relative to the total of terbium, lanthanum, and calcium was obtained in the same manner as in Example 1, except that terbium acetate was used instead of praseodymium acetate to obtain a precipitate of terbium fluoride. 2 Ceramics were obtained.

[0095] Examples 11 to 14 In the same manner as in Comparative Example 6, Tb,La:CaF with a lanthanum content of 10 mol% and a terbium content of 5 mol%, 10 mol%, 15 mol%, and 20 mol%, respectively, based on the total of terbium, lanthanum, and calcium, was prepared. 2 Ceramics were obtained.

[0096] The Tb,La:CaF obtained in Comparative Example 6 and Examples 11 to 14 2 The fluorescence spectrum of the ceramics was measured using a high-resolution fluorescence spectrometer (JASCO SS-25). The results are shown in Figure 19.

[0097] Examples 15 and 16 In the same manner as in Comparative Example 6, Tb,La:CaF was prepared, in which the lanthanum content was 10 mol % and the terbium content was 7 mol % and 13 mol %, respectively, relative to the total of terbium, lanthanum, and calcium. 2 Ceramics were obtained.

[0098] The Tb,La:CaF obtained in Examples 15 and 16 2 The fluorescence spectrum of the ceramics was measured using a high-resolution fluorescence spectrometer (JAPAN SS-25), and the relationship between the fluorescence intensity at a fluorescence wavelength of 542 nm and the fluorescence intensity at a fluorescence wavelength of 586 nm (relative value) and the terbium content (mol%) was investigated, along with the results of Comparative Example 6 and Examples 11 to 14. The results are shown in FIG.

[0099] Example 17 The same procedure as in Comparative Example 6 was repeated except that lanthanum fluoride was not used, and a Tb:CaF 2 Ceramics were obtained.

[0100] Examples 18 to 23 In the same manner as in Comparative Example 6, Tb,La:CaF were prepared with a terbium content of 10 mol% and lanthanum contents of 3 mol%, 5 mol%, 7 mol%, 13 mol%, 15 mol%, and 20 mol%, respectively, based on the total of terbium, lanthanum, and calcium. 2 Ceramics were obtained.

[0101] Examples 24 and 25 In the same manner as in Comparative Example 6, Tb,La:CaF was prepared, in which the terbium content was 15 mol % and the lanthanum content was 3 mol % and 5 mol %, respectively, relative to the total of terbium, lanthanum, and calcium. 2 Ceramics were obtained.

[0102] The Tb,La:CaF obtained in Examples 18 to 25 2 The fluorescence spectrum of the ceramics was measured using a high-resolution fluorescence spectrometer (JASCO SS-25), and the relationship between the fluorescence intensity (relative value) at a fluorescence wavelength of 542 nm and the lanthanum content (mol%) was investigated in conjunction with the results of Examples 13 and 15. The results are shown in FIG. [Explanation of symbols]

[0103] L, L1, L2: Crystal lattice of alkaline earth metal fluoride C1~C4: Examples of clusters of trivalent ions of Pr or rare earth elements R

Claims

1. The alkaline earth metal fluoride contains CaF2 or SrF2, and contains Pr and at least one element selected from the group consisting of Y, La, Gd, and Lu as a rare earth element other than Pr; A visible range laser material in which the Pr content is 0.5 mol % or more and 2 mol % or less with respect to the total of the Pr, the alkaline earth metal, and the rare earth elements other than Pr, and the content (mol %) of the rare earth elements other than Pr is 3 times or more and 9 times or less the Pr content (mol %).

2. The alkaline earth metal fluoride contains CaF2, contains Tb, and contains at least one element selected from the group consisting of Y, La, Gd, and Lu as a rare earth element other than Tb; A visible range laser material in which the content of Tb is 5 mol % or more and 20 mol % or less with respect to the total of the Tb, the alkaline earth metal, and the rare earth element other than Tb, and the content (mol %) of the rare earth element other than Tb is 0.2 times or more and 2 times or less the content (mol %) of Tb.

3. A laser device comprising the visible laser material according to claim 1 or 2 and operating in the wavelength range of 480 nm to 730 nm.

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