JP2003172960A - Babf nonlinear optical crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel BaAlBO<SB>3</SB>F<SB>2</SB>nonlinear optical crystal which is easily grown and makes it possible to produce vacuum-ultraviolet light, to provide a manufacturing method therefor and to provide a wavelength conversion element and a wavelength conversion device using the crystal. <P>SOLUTION: This BABF nonlinear optical crystal has a composition represented by Ba<SB>1+</SB>αAl<SB>1+</SB>βB<SB>1+</SB>γO<SB>3+</SB>δF<SB>2+</SB>ε (wherein, α, β, γ, δ and ε each denotes a value of >-0.2 and <0.2) and nonlinear optical properties. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The invention of this application is based on BABF.
It relates to a nonlinear optical crystal. For more details,
The invention of this application relates to a new BABF nonlinear optical crystal that can be easily grown and can also generate vacuum ultraviolet light, a manufacturing method thereof, a wavelength conversion element using the crystal, and a wavelength conversion device.

[0002]

2. Description of the Related Art The application of laser technology is rapidly expanding in the fields of medical care, semiconductors, information communication, etc., and ultraviolet light is often required.
In recent years, there has been a demand for the development of a solid-state laser technology capable of realizing higher efficiency, smaller size, and longer life in place of the conventional liquid laser. This UV solid state laser is
Generally, Y that enables stable high-power oscillation in the near infrared region
Since solid-state laser light such as AG laser is obtained through a wavelength conversion element, it is indispensable to use an optical material capable of wavelength conversion to a shorter wavelength, and many organizations are actively developing this optical material. Has been done.

The inventors of this application have searched for an optical material in consideration of generation of vacuum ultraviolet light having a wavelength of 200 nm or less, which is on the shorter wavelength side even in the ultraviolet light region. As a result, K ₂ Al ₂ B _{2 has} already been used as a new nonlinear optical crystal.
We have provided O ₇ (KAB) crystals. This KA
The B crystal is the conventionally known KBe ₂ BO ₃ F ₂ (K
BBF) crystal and Sr ₂ Be ₂ B ₂ O ₇ (SBBO) crystal are similar in structure to each other, so that they are expected to have vacuum ultraviolet light generation characteristics similarly to these crystals,
It was revealed that the absorption edge of the KAB crystal is on the relatively long wavelength side, and only the second harmonic up to the wavelength of 232.5 nm in the deep ultraviolet region can be generated. Thus, the solid-state laser capable of generating vacuum ultraviolet light is far from practical use, and a new wavelength conversion optical material capable of generating vacuum ultraviolet light is required.

Therefore, the invention of this application has been made in view of the above circumstances, and it is a new solution that solves the problems of the prior art, is easy to grow, and is capable of generating vacuum ultraviolet light. It is an object to provide a BABF nonlinear optical crystal, a wavelength conversion element and a wavelength conversion device using the crystal.

[0005]

Therefore, the invention of this application provides the following invention in order to solve the above problems.

Namely, the first first invention of this application, in the composition _{Ba 1+ αAl 1+ βB 1+ γO 3+} δF 2+ ε ( wherein, α, β, γ, δ , ε is A BABF nonlinear optical crystal characterized by having nonlinear optical properties, each of which is represented by values greater than -0.2 and less than 0.2).

Secondly, the invention of this application relates to the above invention, wherein the crystal point groups are trigonal system point groups C ₃ , D ₃ ,
Thirdly, a BABF nonlinear optical crystal characterized by belonging to C _3v or one of the hexagonal point groups C _3h and D _3h is used. BA, where is about 0.05
A BF nonlinear optical crystal is provided.

In addition, a fourth aspect of the invention of this application is a wavelength conversion element characterized in that the above-mentioned BABF nonlinear optical crystal is used as a laser light wavelength conversion element. Provided is a wavelength conversion device having a conversion element incorporated therein.

Further, the invention of this application is a method for manufacturing the above-mentioned nonlinear optical crystal, and sixthly, Ba: Al: B: O: F = 1: 1: 1: 3 in stoichiometric ratio. : A starting material and a solvent component, which are blended so as to be 2, are melted to form a melt, and a crystal growth point is brought into contact with the liquid surface of the melt, and the melt is cooled from the saturation temperature while the crystal is grown. A method of manufacturing a BABF nonlinear optical crystal, which comprises:
Seventh, the cooling rate of the melt is 0.1 ° C to 0.5 ° C /
There is also provided a method of manufacturing a BABF nonlinear optical crystal, characterized in that

The above-mentioned BaAlBO ₃ F ₂ of the invention of this application
Regarding the (BABF) nonlinear optical crystal, the existence of the BABF crystal itself is described in H. H. et al. Together with the BaGaBO ₃ F ₂ crystal. Reported in 2000 by Park et al. However, according to a study by Park et al., Since this crystal has a central symmetric structure, it is said that the second-order nonlinear optical effect which is indispensable for generation of higher harmonics is not expressed.

On the other hand, the inventors of the present application
Non-linear optical crystal KBB whose BF crystal has been reported in the past
Focusing on the fact that it is similar to F in terms of chemical formula and crystal structure, the crystal was actually grown, and as a result of more detailed investigation, it was discovered that this crystal exhibits nonlinear optical characteristics. It is a thing. This BABF crystal as a completely new optical material was first presented by the inventors of this application.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION That is, the invention of this application is provided.
The BABF nonlinear optical crystal has a composition of Ba ₁₊αAl₁₊
βB₁₊γO₃₊δF₂₊is represented by ε and has nonlinear optical properties
It is characterized by that. Α, β, γ in the above equation
δ and ε are acceptable for this BABF nonlinear optical crystal.
It shows the range of composition, each of which exceeds -0.2
And less than 0.2. That is, this BAB
The F nonlinear optical crystal has a composition of BaAlBO.₃F₂The crystals of
Basically, compositional deviation that can have the same crystal structure as this,
That is, a composition deviation of less than 20% is allowed for each component
can do. Of course, this BABF nonlinear optics
Says that inevitable impurities may be mixed into the crystal
There is no end.

According to a detailed X-ray crystal structure analysis, this BABF nonlinear optical crystal has an AlBO ₃ F ₂ bond, and the BO ₃ plane structure in the AlBO ₃ F ₂ bond is distorted in the c-axis direction and F It was revealed that the -Al-F bond is asymmetric in the c-axis direction. Due to such an asymmetric structure, the nonlinear optical crystal of the invention of this application develops nonlinear optical characteristics. For example, this BAB
When the F powder microcrystal is irradiated with laser light, it is possible to confirm the generation of second harmonic light due to the nonlinear optical effect.

Further, for example, in the optical evaluation using a thin plate crystal, it can be estimated that the thin plate surface is the c-plane, considering that the BO ₃ plane forms a layered structure, and an actual polarization microscope is used. It is also confirmed from the extinction experiment by the method that the thin plate surface is the optical axis direction, that is, the c-plane. These results also suggest that the crystals may be optically uniaxial.

Further, when a linearly polarized laser is incident from the c-axis direction, a harmonic component parallel to the incident polarized light is observed, and when the polarization direction of the incident light is rotated within the incident plane, it is 60.
A strong signal can be obtained at intervals. Since these harmonic lights are signals obtained from a thin plate crystal having a plate thickness of 0.35 mm, they are not generated under normal phase matching conditions.

From the above-mentioned and the nonlinear optical constants for the crystal point group, the correct point group to which the BABF crystal belongs can be inferred. From the present results, it can be judged that this BABF crystal belongs to at least one of the trigonal system point groups C ₃ , D ₃ and C _3v or the hexagonal system point groups C _3h and D _3h .
From such a crystal structure, there is a possibility that polarization reversal may occur due to application of an electric field.

The BABF nonlinear optical crystal of the invention of this application has an absorption edge at or near 165 nm and has a birefringence of about 0.05. Specifically, these values cannot be strictly specified because they are affected by the composition, crystallinity, etc., but the absorption edge of the BABF nonlinear optical crystal of the invention of this application appears in the range of about 160 to 170 nm, and the birefringence The rate is about 0.05 ± 0.01.
Therefore, it is also a material that can be expected as a new nonlinear optical crystal for generating vacuum ultraviolet light.

For example, the laser wavelength conversion element of the invention of this application is composed of the above BABF nonlinear optical crystal. Further, the wavelength conversion device of the invention of this application,
The wavelength conversion element is incorporated. In these optical components and optical devices such as a laser wavelength conversion element and a wavelength conversion device, vacuum ultraviolet light up to a wavelength of 165 nm can be generated by wavelength conversion, and optical components and optics capable of generating vacuum ultraviolet light. The equipment will be realized. On the other hand, materials for optical fiber for vacuum ultraviolet light,
The use as a surface acoustic wave material or the like can also be illustrated as a concrete example.

The BABF nonlinear optical crystal of the invention of this application as described above is considered to be an anharmonic melting crystal, and can be suitably manufactured by the flux method. More specifically, for example, the stoichiometric ratio of Ba: Al: B: O: F =
A starting material and a solvent component, which were blended so as to have a ratio of 1: 1: 1: 3: 2, were melted to form a melt, and a crystal growth point was brought into contact with the liquid surface of the melt, and the melt was saturated while being pulled For example, a BABF crystal is obtained by cooling from the temperature and growing the crystal. Here, the starting materials are compounded with the stoichiometric ratio as a target, but, of course, inevitable compositional deviation and inclusion of impurities are allowed.

As the starting material, powders of oxides or fluorides of Ba, Al and B can be used. In this case, the solvent components include NaF and Ba.
_{F 2, B 2 O 3,} LiCl, PbO, can be used PbF _2, NaCl, etc., when considering the viscosity and impurity N
It is more preferably aF. The amount of the solvent component added may be, for example, BABF:
It is suitable to set NaF = 1: 1 to 1: 2.
These starting materials and solvent components may be ground to a size of several microns in order to make the melting and reaction sufficient and easy.

The heating is not particularly limited as long as the raw materials can be melted. As a guide, for example, 1000 to 11
For example, heating at about 00 ° C. for about 1 to 2 hours is exemplified. After confirming that the starting materials and solvent components have completely melted, the crystal surface of this melt is brought into contact with a crystal growth point such as a seed crystal or the tip of a platinum wire, which serves as a nucleus for crystal growth, and the melt is pulled up. Is cooled from saturation temperature to allow BABF crystals to grow.

The cooling rate of the melt cannot be generally stated because it can be adjusted depending on the quality and size of the desired crystal, but it is adjusted within the range of about 0.1 to 0.5 ° C./day. can do. For example, the cooling rate can be set low for growing high quality crystals, and the cooling rate can be set high for growing large crystals, which is ideally about 0.2 ° C./day. More specifically, for example, when the cooling rate is about 0.3 ° C./day, a BABF crystal having a diameter of about 9.0 mm and a thickness of about 2 mm can be obtained. Further, by optimizing the above conditions and further extending the growing time while stirring the solution, the diameter of 30
It is also possible to obtain a BABF crystal having a thickness of about 10 mm and a thickness of about 10 mm.

As a result, the BABF nonlinear optical crystal of the invention of this application can be obtained simply and easily.
The nonlinear optical crystal of the invention of this application will be described in more detail below.

[0024]

Example 1 As a starting material, burr fluoride was used.
Umm (BaF₂), Aluminum oxide (Al₂O ₃),acid
Boron Bromide (B₂O₃) In stoichiometric ratio to BaAlBO₃F₂When
Sodium fluoride as a solvent component
(NaF) was added and pulverized and mixed. this
It was filled in a platinum crucible and melted in a cylindrical electric furnace. White
The gold wire is immersed in the solution surface, and the temperature inside the furnace is adjusted from the saturation temperature to 0.
The temperature was lowered at 3 ° C / day. Colorless and transparent in the supersaturation temperature range
BaBO₃AlF₂(BABF) single crystal is immersed in white
Natural nucleation was formed on the gold wire.

As a result of continuing the temperature decrease as it was, after 7 days, a single crystal having a size of 9.5 × 9.0 × 1.5 mm ³ could be obtained. The obtained BABF single crystal is shown in FIG.

The results of differential thermal analysis of this BABF single crystal in an air atmosphere at a temperature rising rate of 10 ° C./min are shown in FIG. It was found that the melting point of this BABF single crystal was 973.6. (Example 2) When the BABF crystal obtained in Example 1 was subjected to inductively coupled plasma (ICP) emission analysis and four-axis X-ray analysis, the crystal was found to be almost BaAlBO _3.
It was confirmed to have a composition of F ₂ . Approximately 0.25 x 0.25 x 0.25 mm sample was cut out from this BABF crystal,
Detailed X-ray structural analysis was performed. The reflection data were all measured using a diffractometer AFC5R manufactured by Rigaku Corporation. As the radiation source, Mo-Kα rays monochromatized with a graphite monochromator by a rotating anticathode X-ray generator were used. FIG. 3 shows the result of X-ray diffraction of the BABF crystal.

The obtained reflection data was refined by the method of least squares to obtain the lattice constant and orientation matrix. As a result, the crystallographic parameter of the BABF crystal was a = 4.8.
860 (8) Å, c = 9.402 (1) Å, α = 90.
0000 ° V = 194.38 (5) Å ³ , Z (number of molecules per unit cell) = 2, F.I. W. (Formula amount) = 261.12
Met. Moreover, when the density was calculated, 4.46 g /
It was cm ³ .

Crystal structure analysis was performed from the collected diffraction line data of 1205. The analysis is performed by the direct method, and the calculation is made by Molecular Stracture, a program for crystal structure analysis.
This was done using eXsan. This B obtained by crystal structure analysis
From the results of coordinates of each atom in the ABF crystal, occupancy, anisotropic displacement parameter, bond distance, bond angle, etc., BAB
The crystal point group of the F crystal is a trigonal point group C ₃ , D ₃ , C _3v ,
Alternatively, it was confirmed to correspond to either of the hexagonal point groups C _3h and D _3h . In addition, the molecular structure of BABF is shown in FIG.
In addition, a BO ₃ plane structure is drawn in FIG.

Although it is difficult to understand from the figure, this BaAlBO
_In the AlBO ₃ F ₂ bond of the ₃ F ₂ (BABF) crystal,
B is 0.1 upward from the BO ₃ plane centered on the B # atom.
637Å deviation, and the bond lengths of F1 # -Al and Al-F2 are different from 1.65Å and 1.98Å, respectively. That is, the BO ₃ plane structure is distorted in the c-axis direction and the F-
It was revealed that the Al-F bond is asymmetric in the c-axis direction. (Example 3) A thickness of 1 mm obtained in the same manner as in Example 1.
The BABF crystal of No. 2 was used to measure the transmission spectrum when irradiated with ultraviolet light having a wavelength of 140 to 240 μm. The results are shown in Fig. 6. This BABF crystal has an absorption edge of 16
It was confirmed to be 5 nm.

Further, when the birefringence was measured by the oil immersion method, it was found that n _e = 1.588 and n _O = 1.637, and the difference (birefringence)
Was 0.049. Of course, the present invention is not limited to the above examples, and it goes without saying that various aspects are possible in details.

[0031]

As described in detail above, according to the present invention, a new BABF nonlinear optical crystal which is easy to grow and can also generate vacuum ultraviolet light, a manufacturing method thereof, and a wavelength conversion element using the crystal, A wavelength conversion device is provided.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a BABF single crystal obtained in an example.

FIG. 2 is a diagram illustrating the results of differential thermal analysis of the BABF single crystal of the invention of this application.

FIG. 3 is a diagram illustrating the result of an X-ray diffraction analysis of a BABF crystal of the invention of this application.

FIG. 4 is a diagram illustrating the molecular structure of BABF of the invention of this application.

FIG. 5 is a view exemplifying a BO ₃ plane structure in BABF of the invention of this application.

FIG. 6 is a diagram illustrating the ultraviolet light transmission characteristics of the BABF crystal of the invention of this application.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor, Sho Akira             1-20-306 Shin-Koriyama, Ibaraki City, Osaka Prefecture F term (reference) 2K002 AB12 BA03 CA02 FA13 HA20                       HA21                 4G077 AA02 BE02 CF10 EA02 HA01                       PF55

Claims (7)

[Claims] 1. A composition _{Ba 1+ αAl 1+ βB 1+ γO 3+} δF
₂₊ ε (where α, β, γ, δ, ε are -0.2, respectively)
And a value of less than 0.2), and having a non-linear optical property. 2. A point group C ₃ , D ₃ , C having a trigonal crystal point group.
_{3 v,} or hexagonal point group C _3h, BABF nonlinear optical crystal according to claim 1, characterized in that it belongs to one of the D _3h. 3. The BABF nonlinear optical crystal according to claim 1, which has an absorption edge of 160 nm or near and a birefringence of about 0.05. 4. The BA according to any one of claims 1 to 3.
A wavelength conversion element, wherein the BF nonlinear optical crystal is a laser light wavelength conversion element. 5. A wavelength conversion device comprising the wavelength conversion element according to claim 4 incorporated therein. 6. The BA according to any one of claims 1 to 3.
A method for producing a BF nonlinear optical crystal, comprising: melting a starting material and a solvent component, which are blended to have a stoichiometric ratio of Ba: Al: B: O: F = 1: 1: 1: 3: 2. As a melt, a crystal growth point is brought into contact with the liquid surface of the melt, and the melt is cooled from the saturation temperature and crystal is grown while pulling up the crystal growth point. 7. The cooling rate of the melt is 0.1 ° C. to 0.5 ° C. /
7. The method for manufacturing a BABF nonlinear optical crystal according to claim 6, wherein the date is set to day.