JP2000089165A - Production of magneto-optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily, efficiently and inexpensively produce a magneto-optical element which allows the perfect specification of the full six-faced crystal bearings of a rectangular planar chip from the appearance alone. SOLUTION: This process for producing the magneto-optical element 20 consists in subjecting the rectangular planar chip to grooving from one surface along one cutting line at the time of transversely and longitudinally cutting a magnetic garnet single crystal and processing the single crystal to the rectangular planar chip, thereby forming the chip to the shape formed with a notch 22 along one side. A structure of a difference in level is obtd. by forming the notch at the side edge of the one side or a groove structure is obtd. by forming the notch near the side edge on one side. The chip may be rectangular or square. The front and rear of the chip are made identifiable by putting the notch from one side. In addition, the one side may be specified by the notch. The perfect specification of the full six-faced crystal bearings of the chip is eventually made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magneto-optical element made of a magnetic garnet single crystal, and more particularly, to forming a notch along one side of a rectangular plate-shaped magnetic garnet single crystal chip, The present invention relates to a method for manufacturing a magneto-optical element in which the orientations of all six surfaces of a rectangular chip cut out can be completely specified. This technique is particularly useful for a Faraday rotator such as a polarization scrambler or an optical attenuator that continuously varies the rotation angle of a polarization plane.

[0002]

2. Description of the Related Art Faraday rotators are used in optical devices such as optical isolators, optical circulators, and optical switches. The Faraday rotator has a Faraday element (magneto-optical element) that rotates a polarization plane of transmitted light by a fixed angle by applying a magnetic field. Recently, liquid-phase epitaxial (hereinafter abbreviated as “LPE”) has been used as the magneto-optical element. The magnetic garnet single crystal film obtained by the method is often used. Normal,
A magnetic garnet single crystal film is grown on the (111) plane of the nonmagnetic garnet substrate by the LPE method, and cut into squares to produce a magneto-optical element having a predetermined thickness. In this case, the surface of the grown magnetic garnet single crystal is also (11)
1) It becomes a plane.

A Faraday rotator incorporated in an optical isolator or an optical circulator has a structure in which a Faraday element is magnetically saturated by a magnetic field of a permanent magnet and a polarization plane is always rotated by 45 degrees. The magneto-optical element constituting the Faraday element is incorporated so that light is incident almost perpendicularly to the (111) plane of the magnetic garnet single crystal. When used for an optical isolator or optical circulator, (111)
There is no particular problem regardless of the orientation of the magnetic garnet single crystal other than the plane.

As an optical device using a Faraday rotator, a polarization scrambler and an optical attenuator have been developed in addition to the optical isolators and optical circulators described above. In a polarization scrambler that continuously and periodically changes the polarization direction of light, or in an optical attenuator for continuously controlling the amount of transmitted light, a Faraday rotation angle of a light transmitted through the Faraday element is controlled. Incorporate a variable rotation angle device. The Faraday element may be constituted by a single magneto-optical element having a thickness whose polarization plane is rotatable by about 90 degrees, or by stacking a plurality of magneto-optical elements such that the polarization plane is rotatable by about 90 degrees as a whole. It is composed. By applying a magnetic field to the Faraday element from two or more directions and changing the combined magnetic field,
Control the Faraday rotation angle.

However, according to recent research, in a method of using such a polarization scrambler or an optical attenuator to control the intensity of an external magnetic field to continuously change the plane of polarization,
There is a correlation between the crystal orientation of the magneto-optical element constituting the Faraday element and the direction in which the external magnetic field is applied, and it has been found that good characteristics can be obtained only when a magnetic field is applied in a specific direction. Conversely, as in the prior art, if a wafer is simply cut into a square to form a magneto-optical element, which is then incorporated as a Faraday element into a variable Faraday rotation angle device, the characteristics of the manufactured optical device will vary greatly. It is. In order to produce a high-quality optical device, it is necessary to be able to specify the crystal orientation of the magneto-optical element and to arrange the crystal orientation of the magneto-optical element in a specific direction when incorporating the magneto-optical element into the optical device.

As described above, since the magnetic garnet single crystal is LPE-grown on the (111) plane of the nonmagnetic garnet substrate, the surface of the grown single crystal film is (111).
Face. Therefore, if the substrate is removed from the wafer and cut into square chips, the front and back sides cannot be distinguished and the crystal orientation of the cut surface (ie, four side surfaces) cannot be specified. Even if the crystal orientation of a certain side surface is specified by the X-ray diffractometer, the crystal orientation cannot be determined during the subsequent handling.

Therefore, the present inventors have previously prepared a magnetic garnet single crystal produced by the LPE method on the (111) plane of a non-magnetic garnet substrate, with the long side being the (112) plane or the (110) plane. A method of manufacturing a magneto-optical element capable of specifying the crystal orientation on the side surface of the cut chip by cutting the chip into rectangular chips as much as possible has been proposed (Japanese Patent Application No. Hei 10-1998).
No. 12140).

[0008]

However, in a chip cut into a rectangular shape as described above, the front and back of the magneto-optical element cannot be distinguished, and the crystal orientations of the opposing side surfaces cannot be completely specified.

In the case of a device structure or usage method in which it is not necessary to completely specify the crystal orientations of all six surfaces of the chip, no particular problem occurs in the above-described manufacturing method. However, recently, a device structure has been developed in which the orientations of all six surfaces of the magneto-optical element must be completely specified and arranged in a prescribed orientation (see Japanese Patent Application No. 10-67753). A typical example is that when a Faraday element is composed of a plurality of magneto-optical elements, when the angle between the magnetization direction of the magneto-optical element and the light beam direction is α, the Faraday rotation angle due to the temperature dependence of the angle α is obtained. The amount of change,
This is a Faraday rotator that applies an external magnetic field in a direction in which the Faraday rotation angle changes due to the temperature dependence of the Faraday effect have mutually opposite signs and substantially equal absolute values. Although the magneto-optical element is made of a magnetic garnet single crystal, it is necessary to completely specify the crystal orientation of all six faces of the magneto-optical element when the magnetic garnet single crystal is viewed in a direction perpendicular to the (111) plane. This is because it has a crystal structure having a three-fold rotational symmetry axis. That is, the opposing side surfaces are not equivalent surfaces. Therefore, in the above example, in order to be able to determine the crystal orientations of all six surfaces of the magneto-optical element, one corner of the rectangular chip is slightly cut to form an orientation marker (mark).

However, the work of determining the crystal orientation of each of the cut rectangular chips one by one with an X-ray diffraction apparatus and attaching an orientation marker is complicated, time-consuming, and increases the cost.

An object of the present invention is to provide a method capable of easily, efficiently and inexpensively manufacturing a magneto-optical element in which crystal orientations of all six faces of a rectangular plate-like chip can be completely specified only by appearance.

[0012]

SUMMARY OF THE INVENTION According to the present invention, when a magnetic garnet single crystal is cut lengthwise and crosswise into a rectangular plate-like chip, a groove is formed from one side along one cutting line, thereby forming one side. Is a method of manufacturing a magneto-optical element having a chip shape in which a notch is formed along. A notch is formed on one side edge to form a step structure, or a notch is formed near one side edge to form a groove structure. The tip may be rectangular or square. By making a cut from one side, the front and back of the chip can be determined, and one side can be specified by the cut, whereby the crystal orientations of all six surfaces of the chip can be completely specified.

A magnetic garnet single crystal is usually grown on a non-magnetic garnet substrate by the LPE method. When the magnetic garnet single crystal is cut lengthwise and crosswise to be processed into a rectangular chip, a groove is formed from one side along one cutting line to form a chip shape with a cut formed along one side.

The magnetic garnet single crystal is cut by a dicing saw or the like while being bonded to a jig. Therefore, either cutting or groove processing may be performed first. That is, after cutting in advance, a groove may be formed from one surface along one of the cutting lines, or a groove may be formed from one surface in advance along one of the cutting lines, and thereafter, cutting may be performed. Of course, groove processing and cutting may be performed alternately. After the cutting process, the magnetic garnet single crystal adhered to the jig is peeled off to obtain individual rectangular chips.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The nonmagnetic garnet substrate (11)
1) A magnetic garnet single crystal film is grown on the surface by the LPE method. When the substrate with the magnetic garnet single crystal film is cut lengthwise and crosswise into a rectangular plate-shaped intermediate product, a groove is formed from one side along one cutting line, thereby forming a magnetic garnet single crystal along one side. A rectangular intermediate workpiece having a cut formed in the film. The cut intermediate workpiece is
The notch allows all six sides to be completely identified. Next, after polishing the intermediate workpiece to a finished thickness dimension, and further cutting it vertically and horizontally to form a rectangular chip, by performing groove processing from one surface along one cutting line, 1
A chip shape with a cut formed along the side is provided. The cut out chip can completely specify all six sides by cutting. Actually, after the heat treatment of the cut-out intermediate workpiece, mirror polishing is performed to a finished thickness dimension, an antireflection film is formed on the surface thereof, and it is cut to the finished dimension. There is no particular limitation on the cutting direction of the intermediate workpiece and the chip, and the cutting may be performed in any direction such that the finally obtained magneto-optical element can be easily configured as a Faraday element.

[0016]

EXAMPLE A magneto-optical element was manufactured by the steps shown in FIG.
The _{PbO-B 2 O 3 -Bi 2} O 3 as a flux, the LPE method, the lattice constant of 12.496A, the composition (CaGd)
₃ (MgZrGa) ₅ O ₁₂ , diameter 3 inches, thickness 117
B on a (111) plane of a non-magnetic garnet substrate of 0 μm.
i-substituted rare earth iron garnet single crystal (LPE film, composition Tb
_1.00 Y _0.65 Bi _1.35 Fe _4.05 Ga _0.95 O ₁₂ , thickness 450
μm). As shown in FIG. 1A, the nonmagnetic garnet substrate 10 is provided with two large and small flat surfaces (orientation flats) in advance. )
Plane is set. The LPE film is indicated by reference numeral 12. Next, as shown in FIG. 1B, the obtained LPE film is cut by a dicing saw having a blade thickness of 0.2 mm at intervals of 7.6 mm in length and 5.0 mm in width. The substrate with the LPE film is adhered to a jig (not shown) so that the substrate side faces upward, and the blade enters from the substrate side. As it is, the cutting position in the x direction is 0.2
The cut is made by shifting by mm and setting the cutting depth to 1395 μm. In FIG. 1B, a dotted line indicates a cutting line (cutting position), and a solid line indicates a cut. FIG. 1C shows the shape of the cut intermediate workpiece 14. Here, the cut step 16 having a depth reaching the LPE film along one side is formed. (Note that in the notation of the plane and orientation of a crystal, a negative index is represented by drawing a horizontal bar over the numerical value.
In this specification, the exponent is indicated by adding a minus sign because it cannot be performed. )

Next, after the substrate was removed by polishing, the magnetic garnet single crystal was heat-treated at 1100 ° C. for 8 hours in the air. The heat treatment is performed to reduce the uniaxial magnetic anisotropy due to the growth induction. After that, it was re-polished to 7.6mm
Mirror-finished to a shape of × 5.0 mm × 0.33 mm (including a blade thickness of 0.2 mm), and an antireflection film was deposited to obtain a second intermediate workpiece 18. Then, as shown in FIG. 1D, cut with a dicing saw having a blade thickness of 0.2 mm at intervals of 1.0 mm in length and 1.2 mm in width.
The sheet was shifted by mm, and a cut was made at a cutting depth of 50 μm. In FIG. 1D, a dotted line indicates a cutting line (cutting position), and a solid line indicates a cut. After the processing, the chips were separated from the jig. FIG. 1E shows the shape and surface of the magneto-optical element 20 finally obtained. 1.0 mm x 1.2 mm x 0.
It has a rectangular shape of 33 mm (including a blade thickness of 0.2 mm), and has a chip shape in which a notch step 22 is formed on one short side. In this magneto-optical element, the magnetization is changed in the beam direction (<11
1> direction), it has a Faraday rotation angle of about 32 degrees.

A measurement system shown in FIG. 2 was prepared, and the temperature characteristics of the Faraday rotation angle were measured by the orthogonal polarizer method. Next, the light passing through the polarizer and the analyzer was installed so that the angle formed by the polarization plane of the light was 105 degrees, and the temperature characteristics of the light attenuation were measured. This measurement system has basically the same configuration as the magneto-optical variable attenuator. As shown in FIG. 2A, the light emitted from the optical fiber 30 becomes parallel light by the lens 31, passes through the polarizer 32, the Faraday element 33, and the analyzer 34, and is collected by the lens 35 at the incident end of the optical fiber 36. Light. Here, the portion denoted by reference numeral 38 is a Faraday rotator, and an example thereof is shown in FIG. A saturation magnetic field is applied to the Faraday element 33 in a direction parallel to the optical axis by a pair of permanent magnets 40 and 41, and a magnetic field is applied in a direction perpendicular to the optical axis by an electromagnet 42 to change the coil current of the electromagnet 42. Change their combined magnetic field.

The Faraday element was constructed as shown in FIG. 3 by combining three magneto-optical elements 20 manufactured by the method shown in FIG. As shown in FIG. 3A, the foremost magneto-optical element 20
The (-1-112) surface on which the notch is formed is on the S pole side of the electromagnet, and the (-1-112) surface on which the notch is formed on the two rear magneto-optical elements 20 is the N pole of the electromagnet. The orientation of the magneto-optical element was changed so as to be on the side. For comparison, as shown in FIG. 3B, the orientation of the magneto-optical element was changed such that the (-1-12) plane where the cuts of all the magneto-optical elements 20 were formed was located on the S pole side of the electromagnet. They were aligned and arranged. In the relationship between the magneto-optical element and the permanent magnet, the cut (111) surface is disposed on the S pole side of the permanent magnet, and the opposite surface is disposed on the N pole side of the permanent magnet.

FIG. 4 shows the measurement result of the Faraday rotation angle, and FIG. 5 shows the measurement result of the optical attenuation. In each case, A is a case where the orientation is changed (A in FIG. 3), and B is a case where the orientation is aligned (B in FIG. 3). From these results, it can be seen that the temperature characteristics are good when the orientation is changed and the combination is appropriately performed, but the temperature characteristics are poor when the orientation is simply aligned. As described above, since the temperature characteristics are largely different, it is necessary to define the direction of the magnetic field application with respect to the crystal orientation. For that purpose, the shape of the magneto-optical element obtained by the method of the present invention is extremely effective.

FIG. 6 shows another embodiment of the method of the present invention. Since it is basically the same as the embodiment shown in FIG. 1, detailed description is omitted. The difference here is the cutting direction. The cutting direction of this embodiment differs from the cutting direction of the embodiment shown in FIG. 1 by 24 degrees. By doing so, E in FIG.
As shown in the figure, the a-plane, b-plane, c-plane and d-plane of the cut surface of the finally obtained magneto-optical element are as follows. The position is as shown in FIG. a-plane: a plane inclined 24 degrees from (-1-112) to (-101) b-plane: a plane inclined 24 degrees from (-110) to (-12-1) c-plane: (11-2) to ( 10-1) A plane inclined 24 degrees to d plane: A plane inclined 24 degrees from (1-10) to (1-21)

The magneto-optical elements were arranged in the same direction as shown in FIG. 3B to form a Faraday element, which was incorporated in the measurement system of FIG. 2 to measure the temperature dependence of the Faraday rotation angle and the amount of light attenuation. The magneto-optical element was arranged such that the a-plane was on the S pole side of the electromagnet. Note that, in relation to the permanent magnet, the notched (111) surface is disposed on the S pole side of the permanent magnet, and the opposite surface is disposed on the N pole side of the permanent magnet.

FIG. 7 shows the measurement result of the Faraday rotation angle, and FIG. 8 shows the measurement result of the optical attenuation. As can be seen from these results, good temperature characteristics can be obtained by applying a magnetic field in an appropriate direction.

The spectrum of the Faraday rotation angle greatly differs depending on the direction of the applied magnetic field. The observed Faraday rotation angle includes not only the contribution from the Faraday effect but also the contribution from the crystal anisotropy. Because it is. The magnetic garnet single crystal has crystal magnetic anisotropy, whereby the <111> orientation and its symmetrically equivalent orientation are the easy axes of magnetization, and the <100> orientation and its symmetrically equivalent orientation are difficult to magnetize. Axis. The garnet single crystal is cubic, and 3 in the direction perpendicular to the (111) plane.
Due to the rotational symmetry axis, the cut side and the opposite side are not equivalent. From these facts, it is extremely effective to distinguish the side surfaces by the cuts and arrange them in an appropriate direction in terms of improving characteristics. The magnitude of the magnetocrystalline anisotropy increases as the temperature decreases (P. Hansen et al., Thin Solid Films, 114 (1984)
69-107).

[0025]

As described above, according to the present invention, when a magnetic garnet single crystal is cut lengthwise and crosswise and cut into rectangular plate-shaped chips,
This is a method of manufacturing a magneto-optical element in which a groove is formed from one side along one cutting line to cut out into a rectangular plate-shaped chip having a cut formed along one side. Can easily, efficiently, and inexpensively manufacture a magneto-optical element that can be completely specified only by its appearance. By using a magneto-optical element that can determine the crystal orientation of all six surfaces of the chip only by appearance, and properly arranging it,
An optical device having good characteristics and little variation can be configured.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a method for manufacturing a magneto-optical element according to the present invention.

FIG. 2 is an explanatory diagram of a measurement system used in the present invention.

FIG. 3 is an explanatory view showing an arrangement state of a magneto-optical element.

FIG. 4 is a graph showing a relationship between a current value of an electromagnet and a Faraday rotation angle.

FIG. 5 is a graph showing a relationship between a current value of an electromagnet and an optical attenuation.

FIG. 6 is an explanatory view showing another embodiment of the method of manufacturing a magneto-optical element according to the present invention.

FIG. 7 is a stereo projection view showing a surface of a magneto-optical element manufactured by the method.

FIG. 8 is a graph showing a relationship between a current value of an electromagnet and a Faraday rotation angle.

FIG. 9 is a graph showing the relationship between the current value of an electromagnet and the amount of light attenuation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Non-magnetic garnet board 12 LPE film 14 Intermediate work 16 Cut notch 18 Second intermediate work 20 Magneto-optical element 22 Cut notch

Claims (5)

[Claims] When a magnetic garnet single crystal is cut lengthwise and crosswise to form a rectangular plate-like chip, a notch is formed along one side by performing a groove processing from one surface along one cutting line. A method for manufacturing a magneto-optical element, which is formed into a chip shape. 2. A method for growing a magnetic garnet single crystal film on a (111) plane of a nonmagnetic garnet substrate by a liquid phase epitaxial method, and cutting the magnetic garnet single crystal vertically and horizontally to form a rectangular chip. A method of manufacturing a magneto-optical element, wherein a groove is formed from one side along a cutting line to form a chip having a cut formed along one side. 3. A method for growing a magnetic garnet single crystal film on a (111) plane of a nonmagnetic garnet substrate by liquid phase epitaxy, and cutting the substrate with the magnetic garnet single crystal film vertically and horizontally to form a rectangular plate-like intermediate work. When forming a workpiece, a groove is formed from one surface along one cutting line to form a rectangular intermediate workpiece in which a cut is formed in the magnetic garnet single crystal film along one side, and then the intermediate processing is performed. When the object is polished to the finished thickness dimensions, and then cut vertically and horizontally to form a rectangular chip, a notch is formed along one side by applying a groove processing from one side along one cutting line A method for manufacturing a magneto-optical element, comprising: 4. After heat-treating the cut intermediate workpiece,
4. The method of manufacturing a magneto-optical element according to claim 3, wherein the surface is mirror-polished to a finished thickness, an antireflection film is formed on the surface, and the surface is cut to a finished dimension. 5. The method for manufacturing a magneto-optical element according to claim 1, wherein the cut is formed at one side edge to form a step.