JP3555098B2 - Method for producing garnet-type structure single crystal - Google Patents

Description

【００１７】
【表２】

【００１８】
なお、図３中、２０は＜１００＞方位から１０度の方位を示す線であり、２１は＜１１０＞方位から２０度の方位を示す線であり、さらに２２は＜２１１＞方位から２０度の方位を示す線である。
【００１９】
育成方向が＜１００＞方位や＜１１１＞方位である従来の場合には、育成結晶と溶融部の固液界面がファッセット成長面の（２１１）面、（１１０）面、もしくは（１００）面と浅い角度になるため、ファセット成長が起こり、コアが現れる。それに対し、本発明においては、＜１００＞方位に等価な方位から１０度以上、＜１１０＞方位に等価な方位から２０度以上、および＜２１１＞方位に等価な方位から２０度以上、の角度に結晶を育成するため、固液界面は（２１１）面、（１１０）面、もしくは（１００）面と充分深い角度になり、ファセット成長は起きない。そのためコアのない光学的品質に優れたガーネット型構造単結晶ファイバを作製することができる。
【００２０】
Ｃｒ，Ｃａ：ＹＡＧの他に、不純物を添加しないＹＡＧ単結晶ファイバや、ネオジウムなど他の不純物元素を添加したＹＡＧ単結晶ファイバを育成する際にもこの方法は有効であった。またイットリウム・スカンジウム・アルミニウム・ガーネット（分子式：Ｙ_３ Ｓｃ_ｘ Ａｌ_５−ｘ Ｏ_１２）単結晶ファイバ、イットリウム・ガリウム・アルミニウム・ガーネット（分子式：Ｙ_３ Ｇａ_ｘ Ａｌ_５−ｘ Ｏ_１２）単結晶ファイバ、ルテチウム・アルミニウム・ガーネット（分子式：Ｌｕ_３ Ａｌ_５ Ｏ_１２）単結晶ファイバ、イットリウム・鉄・ガーネット（分子式：Ｙ_３ Ｆｅ_５ Ｏ_１２）単結晶ファイバを育成方位１０１〜１０７に引き上げたところやはりコアは生じなかった。
【００２１】
本発明の製造方法が、ここに挙げた以外のガーネット型構造単結晶ファイバの製造にも適用できることはもちろんである。固体レーザ用ガーネット型構造単結晶ファイバに限らず、アイソレータなどの他の光学素子に用いるガーネット型構造単結晶ファイバにも適用できる。さらに本発明の製造方法を用いて、チョクラルスキー法によるＹＡＧ単結晶ファイバ（直径５００μｍ）育成を行ったところコアは生じなかった。レーザ加熱溶融法、チョクラルスキー法以外の引き上げ方法による、ガーネット型構造単結晶ファイバ育成にも、さらにその他のガーネット型構造単結晶の育成にも、本発明の製造方法が用いられうることもまたもちろんである。
【００２２】
【発明の効果】
以上説明したように、本発明のガーネット型構造単結晶の製造方法によると、育成方向に対する種結晶の方位を＜１００＞方位に等価な方位から１０度以上、＜１１０＞方位に等価な方位から２０度以上、および＜２１１＞方位に等価な方位から２０度以上の角度を持つ方位として、結晶を育成したため、作製されたガーネット型構造単結晶はファセット成長によるコアを含んでおらず、優れた光学的均質性を有していた。
【図面の簡単な説明】
【図１】本発明によるレーザ加熱溶融法を用いたガーネット型構造単結晶ファイバの製造方法を表わす模式図である。
【図２】本発明において引き上げられる結晶の育成方位を示す図である。
【図３】本発明において引き上げられる結晶の育成方位を示す図である。
【図４】従来のレーザ加熱溶融法を用いたガーネット型構造単結晶ファイバの製造方法を示す図である。
【図５】従来法によって作製されたガーネット型構造単結晶のクロスニコル配置による偏光顕微鏡断面写真を示す図である。
【図６】本発明の方法で作成した結晶のクロスニコル配置による偏光顕微鏡断面写真を示す図である。
【符号の説明】
１１ 母材
１２ 溶融部
１３ 育成単結晶ファイバ
１４ 種結晶
１５ 加熱用ＣＯ_２ レーザ光
１６ 育成方向
１７ 結晶軸方向
１８ 検討対象結晶育成方位
１９ 本発明で育成される結晶の育成方位
２０ ＜１００＞方位から１０度の方位を示す線
２１ ＜１１０＞方位から２０度の方位を示す線
２２ ＜２１１＞方位から２０度の方位を示す線
２３ ファセット成長部
１０１〜１０７ コアを生じなかった育成実施方位
２０１〜２０６ コアを生じた育成実施方位[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a garnet-type structure single crystal used for an optical device such as a laser device and an isolator.
[0002]
[Prior art]
In a garnet type single crystal fiber used for an optical device such as a laser device or an isolator, the optical uniformity has a great influence on the performance. In a crystal to be formed, if a refractive index fluctuation portion, that is, a core is formed by facet growth on the (211) plane, the (110) plane, or the (100) plane, optical uniformity is reduced, and as a result, element performance is reduced. Invite. As an example of this problem, the growth of a garnet type single crystal fiber used for a solid-state laser will be described.
[0003]
In general, in a solid-state laser, the laser active species emits a part of the excitation energy in the form of heat, so that the temperature of the laser rod increases during excitation as compared to before the excitation. Since the luminous efficiency of the laser active species decreases as the temperature rises, it is important to dissipate sufficient heat from the laser rod as a condition for efficient laser oscillation. Compared to a standard rod with a diameter of about 5 mm, a fiber-shaped rod with a diameter of about 500 μm or less has a shorter distance from the center of the excited laser active species to the cooling part on the outer edge of the rod, and efficiently dissipates heat. Is performed. Therefore, a single crystal fiber is required for the laser.
[0004]
In a conventional method of manufacturing a garnet-type single crystal fiber for laser, as shown in FIG. 4, laser heating is performed using a seed crystal 14 oriented in a <100> direction or a <111> direction with respect to a growth direction. The crystal 13 produced by a melting method or the like was pulled up. In this case, facet growth on the (211) plane, the (110) plane, or the (100) plane appears at a part 23 of the solid-liquid interface of the crystal 13 to be produced, and as a result, a refractive index fluctuation portion, a so-called core, is formed. . This is the same phenomenon as that observed in a crystal conventionally produced by the Czochralski method. The cause of the refractive index fluctuation is considered to be lattice distortion. (See B. Cockayne et al., J. Material Science 8 (1973) p. 382)
FIG. 5 shows a cross-sectional view of a cross-Nicol arrangement polarizing microscope of the crystal 13 produced. The polarization rotation was caused by the birefringence accompanying the change in the refractive index, and the core was observed. When light was passed through the crystal 13 to be produced, the light was scattered by the core, so that the laser oscillation characteristics were very poor. For example, yttrium aluminum garnet with the addition of calcium and chromium (molecular _{formula: Cr, Ca: Y 3 Al} 5 O 12, Cr, Ca: abbreviated as YaG) For a fiber laser, the gain is <111> orientation is greater than < The single crystal fiber grown in the 100> orientation was assembled in a laser device and excited with light having a wavelength of 1.06 μm and an intensity of 10 W. However, light was strongly scattered in the rod and did not oscillate.
[0005]
[Problems to be solved by the invention]
In such a method of manufacturing a garnet single crystal fiber, a part of a crystal to be manufactured is formed with a refractive index change portion, a so-called core, by facet growth on a (211) plane, a (110) plane, or a (100) plane, and a laser device is formed. When it is used for an optical device such as an optical device or an isolator, there is a problem in optical quality. An object of the present invention is to provide a method for producing a garnet-type single crystal without a core.
[0006]
[Means for Solving the Problems]
The present invention relates to a method for producing a garnet-type structure single crystal in which a seed crystal is brought into contact with a melt of a crystal having a garnet-type structure, and a single crystal is grown by pulling up the seed crystal.
A garnet-type single crystal in which a tip of a base material made of a crystal having a garnet-type structure is melted, a seed crystal is brought into contact with the melted tip, and the seed crystal is pulled up to grow a fiber-like single crystal. In the manufacturing method of
In a method for producing a garnet-type structure single crystal in which a seed crystal is brought into contact with a melt of a crystal having a garnet-type structure stored in a crucible and a rod-shaped single crystal is grown by rotating and pulling up the seed crystal,
A direction in which the seed crystal is pulled in a range 19 which is at least 10 degrees from the <100> direction, at least 20 degrees from the <110> direction, and at least 20 degrees from the <211> direction, or A method for producing a garnet-type structure single crystal, wherein a crystallographically equivalent direction is made to coincide with the one direction.
[0007]
Further, in the method for producing a garnet-type structure single crystal, the crystal having the garnet-type structure is yttrium aluminum garnet.
[0008]
Further, the crystals having the garnet-type structure include yttrium scandium aluminum garnet (molecular formula: Y ₃ Sc _x Al _5-x O ₁₂ ) and yttrium gallium aluminum garnet (molecular formula: Y ₃ Ga _x Al _{5- x} O ₁₂ ), lutetium aluminum garnet (molecular formula: Lu ₃ Al ₅ O ₁₂ ), or yttrium iron garnet (molecular formula: Y ₃ Fe ₅ O ₁₂ ). This is a method for producing a structural single crystal.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
When the growth direction of the garnet crystal is the <100> direction or the <111> direction, the solid-liquid interface has a shallow angle with the (211), (110), or (100) facet growth surface. Although a core due to facet growth appears, in the present invention, 10 degrees or more from the direction equivalent to the <100> direction, 20 degrees or more from the direction equivalent to the <110> direction, and 20 degrees from the direction equivalent to the <211> direction. Since the crystal is grown at an angle of degrees or more, the solid-liquid interface between the grown crystal and the melt has a sufficiently deep angle with the (211) plane, the (110) plane, or the (100) plane, and no facet growth occurs. Accordingly, a garnet-type structure single crystal having no core and excellent in optical quality can be manufactured.
[0010]
【Example】
FIG. 1 schematically shows an outline of a method for manufacturing a garnet-type single crystal fiber according to the present invention. In this embodiment, a case where Cr, Ca: YAG is manufactured by using a laser heating and melting method will be described. The base material 11 is a YAG single crystal in which calcium oxide and chromium oxide are deposited on the surface. The upper end of the base material is heated and melted by the CO ₂ laser beam 15. When the YAG seed crystal 14 is brought into contact with the melted portion 12 and the seed crystal 14 is moved upward, a Cr, Cr: YAG single crystal fiber 13 is grown. The radius R _{f of the} grown crystal is
[0011]
(Equation 1)
_{R f = R s (V s} / V f) 2,
Is determined by Here, R _s is the radius of the base material, V _f is the pulling speed of the seed crystal, V _s is the feeding speed of the base material, and is adjusted so that R _f is 500 μm or less. The crystal orientation of the single crystal fiber 13 is the same as the crystal orientation of the seed crystal 14. The seed crystal 14 is set so that the crystal orientation is perpendicular to the <001> direction and 15 ° from the <100> orientation with respect to the growth direction. The crystal grown in the growth direction 16 had no core due to facet growth, and was excellent in optical uniformity. 17 indicates the crystal axis direction.
[0012]
FIG. 6 shows a cross-sectional microscopic photograph of the produced crystal 13 with the crossed Nicols arrangement. No birefringence with refractive index fluctuation is observed at all. When a laser resonator was formed using the grown crystal, the laser oscillated at a wavelength of 1.34 μm to 1.58 μm with excitation light having a wavelength of 1.06 μm. At an oscillation wavelength of 1.45 μm, the threshold value was 0.3 W, and the slope efficiency was 50%. Since the crystal produced by the conventional method did not oscillate, the effect of the present invention is clear.
[0013]
The result of actually producing a crystal having a growth orientation other than the above is shown in a stereo projection. The crystal structure of the garnet is Ia3d, and considering the symmetry, only the target portion 18 surrounded by the thick frame in FIG. Other directions have equivalent directions in the target portion. In FIG. 3, the target portion is enlarged, and the growth orientation in which no core is formed is indicated by oblique lines 19.
[0014]
First, when the growth orientations indicated by points 101 to 107 including the above example were examined, no core was formed. These directions are (θ, φ) = (90 °, 10 °), (90 °, 15 °), (90 °, 15 °) and (90 °), where θ is the angle from <001> and φ is the angle from the (010) plane. , 25 °), (86 °, 25 °), (84 °, 18 °), (79 °, 11 °), and (83 °, 7 °). Also, azimuths (θ, φ) indicated by points 201 to 206 in FIG. 3 = (90 °, 9 °), (90 °, 26 °), (85 °, 26 °), (83 °, 19 °) ), (78 °, 12 °) and (84 °, 6 °) yielded a core. Furthermore, when the growth orientations around the orientation were examined, no core was formed in the orientations (diagonally shaded portions 19) of 10 degrees or more from the <100> direction, 20 degrees or more from the <110> direction, and 20 degrees or more from the <211> direction. It was confirmed.
[0015]
Next, Table 1 and Table 2 show the growing direction in which the core was not formed and the growing direction in which the core was formed, corresponding to the numbers shown in FIG.
[0016]
[Table 1]

[0017]
[Table 2]

[0018]
In FIG. 3, reference numeral 20 denotes a line indicating an azimuth of 10 degrees from the <100> azimuth, reference numeral 21 denotes a line indicating an azimuth of 20 degrees from the <110> azimuth, and reference numeral 22 denotes a line indicating 20 degrees from the <211> azimuth. It is a line indicating the direction of.
[0019]
In the conventional case where the growing direction is the <100> direction or the <111> direction, the solid-liquid interface between the growing crystal and the melted portion is the (211), (110), or (100) plane of the facet growth plane. The facet growth occurs and the core appears. In contrast, in the present invention, an angle of 10 degrees or more from the direction equivalent to the <100> direction, 20 degrees or more from the direction equivalent to the <110> direction, and 20 degrees or more from the direction equivalent to the <211> direction In order to grow crystals, the solid-liquid interface has a sufficiently deep angle with the (211) plane, the (110) plane, or the (100) plane, and facet growth does not occur. Therefore, a garnet-type structure single crystal fiber having no core and excellent in optical quality can be manufactured.
[0020]
In addition to Cr and Ca: YAG, this method was also effective when growing a YAG single crystal fiber without adding impurities or a YAG single crystal fiber with other impurities added such as neodymium. Further, a single crystal fiber of yttrium scandium aluminum garnet (molecular formula: Y ₃ Sc _x Al _5-x O ₁₂ ) and a single crystal fiber of yttrium gallium aluminum garnet (molecular formula: Y ₃ Ga _x Al _5-x O ₁₂ ) When a lutetium aluminum garnet (molecular formula: Lu ₃ Al ₅ O ₁₂ ) single crystal fiber and an yttrium iron garnet (molecular formula: Y ₃ Fe ₅ O ₁₂ ) single crystal fiber were pulled up to the growth orientations 101 to 107, the core was also increased. Did not occur.
[0021]
It goes without saying that the production method of the present invention can be applied to the production of a single crystal fiber having a garnet-type structure other than those described above. The invention is not limited to the garnet-type single crystal fiber for a solid-state laser, but can be applied to a garnet-type single crystal fiber used for another optical element such as an isolator. Furthermore, when a YAG single crystal fiber (diameter: 500 μm) was grown by the Czochralski method using the manufacturing method of the present invention, no core was formed. Laser heating and melting method, by a pulling method other than the Czochralski method, to grow a garnet-type structure single crystal fiber, and also to grow other garnet-type structure single crystals, the manufacturing method of the present invention can also be used Of course.
[0022]
【The invention's effect】
As described above, according to the method for manufacturing a garnet-type structure single crystal of the present invention, the orientation of the seed crystal with respect to the growth direction is at least 10 degrees from the orientation equivalent to the <100> orientation, and from the orientation equivalent to the <110> orientation. Since the crystal was grown as an orientation having an angle of 20 degrees or more from the orientation equivalent to the <211> orientation or more, the produced garnet-type structure single crystal did not include a core formed by facet growth, and was excellent. It had optical homogeneity.
[Brief description of the drawings]
FIG. 1 is a schematic view illustrating a method for manufacturing a garnet-type structure single crystal fiber using a laser heating and melting method according to the present invention.
FIG. 2 is a view showing a growth orientation of a crystal pulled up in the present invention.
FIG. 3 is a view showing a growth orientation of a crystal pulled up in the present invention.
FIG. 4 is a view showing a method for manufacturing a garnet-type single crystal fiber using a conventional laser heating and melting method.
FIG. 5 is a drawing showing a cross-sectional polarizing microscope photograph of a garnet-type structure single crystal produced by a conventional method, in a crossed Nicol arrangement.
FIG. 6 is a diagram showing a cross-sectional polarizing microscopic photograph of a crystal prepared by the method of the present invention in a crossed Nicols arrangement.
[Explanation of symbols]
Reference Signs List 11 Base material 12 Fused portion 13 Growing single crystal fiber 14 Seed crystal 15 CO ₂ laser beam for heating 16 Growing direction 17 Crystal axis direction 18 Crystal growth direction 19 to be studied Growth direction 20 of crystal grown in the present invention <100> direction Line 21 indicating a direction of 20 degrees from the <110> direction 22 Line indicating a direction of 20 degrees from the <23> facet Growing portions 101 to 107 Growing execution direction 201 in which no core was generated ２０６206 Development direction that produced the core

Claims (5)

In a method for producing a garnet-type structure single crystal, in which a seed crystal is brought into contact with a melt of a crystal having a garnet-type structure and a single crystal is grown by pulling up the seed crystal,
A direction in which the seed crystal is pulled in a range 19 which is at least 10 degrees from the <100> direction, at least 20 degrees from the <110> direction, and at least 20 degrees from the <211> direction of the seed crystal, or A method for producing a garnet-type structure single crystal, wherein a crystallographically equivalent direction is made coincident with the one direction. A garnet-type structure single crystal in which a tip of a base material made of a crystal having a garnet-type structure is melted, a seed crystal is brought into contact with the melted tip, and a fiber-like single crystal is grown by pulling up the seed crystal. The seed crystal is pulled out in a range 19 which is at least 10 degrees from the <100> direction, at least 20 degrees from the <110> direction, and at least 20 degrees from the <211> direction of the seed crystal. A method for producing a garnet-type structure single crystal, wherein one direction or a crystallographically equivalent direction is made coincident with the one direction. In a method for producing a garnet-type structure single crystal in which a rod-shaped single crystal is grown by bringing a seed crystal into contact with a melt of a crystal having a garnet-type structure contained in a crucible and pulling up the seed crystal while rotating,
A direction in which the seed crystal is pulled in a range 19 which is at least 10 degrees from the <100> direction, at least 20 degrees from the <110> direction, and at least 20 degrees from the <211> direction of the seed crystal, or A method for producing a garnet-type structure single crystal, wherein a crystallographically equivalent direction is made coincident with the one direction. 4. The method according to claim 1, wherein the crystal having the garnet-type structure is yttrium aluminum garnet. Crystals having the garnet-type structure include yttrium scandium aluminum garnet (molecular formula: Y ₃ Sc _x Al _5-x O ₁₂ ) and yttrium gallium aluminum garnet (molecular formula: Y ₃ Ga _x Al _5-x O). ₁₂ ), lutetium aluminum garnet (molecular formula: Lu ₃ Al ₅ O ₁₂ ), or yttrium iron garnet (molecular formula: Y ₃ Fe ₅ O ₁₂ ). The method for producing a garnet-type structure single crystal according to any of the above.

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