JP2823098B2 - Faraday rotating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a material having a Faraday effect.

[0002]

2. Description of the Related Art The Faraday effect refers to a phenomenon in which, when linearly polarized light travels through a substance in a magnetic field in the direction of the magnetic field, the plane of polarization rotates according to the strength of the magnetic field. This phenomenon can be used for a magnetic field sensor, for example. In optical communication using a semiconductor laser as a light source, oscillation becomes unstable when reflected light from an optical fiber cable, a connector, or the like returns to the semiconductor laser. To prevent this instability, it can be used as an optical isolator. These applications have recently seen rapid progress. As a material for the Faraday effect element, a garnet oxide magnetic material has been proposed. There are two directions when using a garnet-type oxide magnetic material as a Faraday effect element.
One of the methods is to grow a single crystal using a flux method or a zone melt method, and to form an element as a block having a shape of, for example, 1 mm square. The other one is
A single crystal of Gd ₃ Ga ₅ O ₁₂ grown in advance by the pulling method is used as a substrate, and a garnet-type oxide magnetic material is grown on the substrate surface by a flux method to form a thin film single crystal by an epitaxial method. Make up. In these cases, there are some problems at present. The Faraday effect caused by magnetism depends on saturation magnetization, and particularly strongly depends on temperature change of the saturation magnetization. As the temperature rises, the saturation magnetization decreases, and the Faraday rotability also decreases proportionally. At the Curie temperature, the saturation magnetization disappears and the Faraday rotability also disappears. For this reason, the biggest drawback of the Faraday effect element is that the temperature change is large.

[0003] Attempts to improve the temperature fluctuation have been made to improve the temperature change of the saturation magnetization value of a material. This improvement utilizes the properties of ferrimagnetism to reduce the temperature change of the saturation magnetization value by offsetting the ferrimagnetic component. This phenomenon is physically known as a magnetic phenomenon, and a typical example is provided by Gd ₃ Fe ₅ O ₁₂ . For example, in the case of a block single crystal, the A ion of the chemical formula A ₃ B ₅ O ₁₂ having a garnet structure is improved by changing the composition ratio of constituent elements with Gd trivalent ions. However,
There are problems with the restriction on the amount of the substitution element and the uniformity distribution of the substituted element in the block single crystal. On the other hand, in the case of a thin film crystal, it can be said that the degree of freedom in the amount of the substitution element is higher than that of the block single crystal, and the superiority of the thin film crystal also appears, so that the uniformity of the constituent elements in the thin film crystal is extremely excellent. However, there is a temperature change of the saturation magnetization value as a magnetic phenomenon, and it can be said that achieving a zero temperature coefficient is difficult.

[0004]

An object of the present invention is to solve the above-mentioned problems and to provide a temperature characteristic close to a zero temperature coefficient by combining the Faraday rotability in the plus direction and the minus direction of the constituents of an oxide having a garnet structure. An object of the present invention is to provide a Faraday rotation element.

[0005]

[MEANS FOR SOLVING THE PROBLEMS] The present invention provides a method for manufacturing a semiconductor device comprising:
By forming a coating film in which two or more kinds of oxide magnetic fine particles having a garnet structure are dispersed, temperature change due to a change in composition of the saturation magnetization value is not the main means of improvement.
It has been found that the temperature characteristics close to zero temperature coefficient can be realized by combining the Faraday rotation abilities in the plus direction and the minus direction possessed by each of the fine particles having more than one kind of composition. That is, according to the present invention, magnetic fine particles are deposited on a substrate.
Faraday forming a coating film dispersed in
A rotating element, wherein the magnetic fine particles have a general formula of A ₃
B ₅ O ₁₂ (where A represents at least one element selected from the group consisting of a rare earth element which becomes a trivalent ion and Bi which becomes a trivalent ion, and B represents a transition metal which becomes a trivalent ion and a trivalent ion
It represents one or more elements selected from Al, Ga, Sc, and In, and elements that become trivalent by a combination of divalent-tetravalent or divalent-pentavalent. ) Is a garnet-type structure oxide represented by the formula (1), and is composed of fine particles of two or more kinds having an average particle size of 30 to 1000 °, and each fine particle has
Combines Faraday rotation capability in the negative and positive directions
And the variation of the Faraday rotation angle between -20 ° C and 110 ° C
The present invention relates to a Faraday rotating element characterized by being 0.76% or less . A in the above general formula is Y, La, Ce, Pr, Nd, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like are at least one element selected from rare earth elements which become trivalent ions and Bi which becomes trivalent ions. B is a transition metal that becomes a trivalent ion, Al, Ga, Sc, and In that becomes a trivalent ion, and divalent -4.
One or more elements selected from trivalent elements by a combination of divalent or divalent to pentavalent, for example, as a transition metal to be a trivalent ion, Cr, Mn, Fe, Co and the like; Examples of the combination of divalent-tetravalent or divalent-pentavalent include Co, Fe, Cu, Ni,
Examples include a combination of a divalent element such as Zn and a tetravalent element such as Si, Ge, Zr, Ti, Hf, Sn, Pb, and Mo, or a pentavalent element such as V, Nb, and Ta. The average particle diameter of the garnet-type oxide magnetic fine particles of the present invention is 30 to 1000 °, preferably 10 to 100 °.
0-600 °. If the average particle diameter is smaller than 30 °, it becomes superparamagnetic due to thermal disturbance. Also,
If it is larger than 1000 °, light is scattered and noise is generated, which is not preferable. The particle shape is preferably optically symmetric and preferably spherical, but may be polyhedral or plate-like. The method for producing the oxide magnetic fine particles having the garnet-type structure is not particularly limited as long as particles having the above-described characteristics can be obtained, and may be a hydrothermal synthesis method, a coprecipitation method, a melting method, an alkoxide method, a gas phase method, or the like. Is used.

In the present invention, a coating film in which two or more kinds of the garnet-type oxide magnetic fine particles are dispersed is formed on a substrate. Thereby, the Faraday rotation ability of each of the fine particles having two or more compositions in the plus direction and the minus direction can be combined to realize a temperature characteristic close to a zero temperature coefficient. The coating film in the present invention is formed from the garnet-type oxide fine particles and a binder. As the binder, an amorphous binder of an inorganic oxide or an organic binder is used. In particular, in order to reduce noise due to light scattering, it is desirable that the refractive index of the binder matches the refractive index of the garnet-type oxide fine particles,
± 2 deviation of refractive index of garnet-type oxide fine particles
It is preferably 0% or less, particularly preferably ± 10% or less. The coating layer is formed by dispersing or dissolving garnet-type oxide fine particles and a binder in water or an organic solvent, applying the dispersion on a substrate, and then curing the binder by heat treatment or the like. The substrate is not particularly limited, and is a single crystal substrate, a polycrystalline substrate, an amorphous substrate such as glass, an inorganic material substrate such as a composite substrate, or an acrylic resin, a polycarbonate resin, a polyester resin, a polyamide resin, a polyimide resin, or the like. Organic material substrate can be used.

[0007]

The present invention will be described below in detail with reference to examples. Example 1 The following three types of garnet-type oxide fine particles were synthesized by a coprecipitation firing method. Composition 1 Y ₃ (ScGa) _0.7 Fe _4.3 O ₁₂ average particle diameter 450Å Composition 2 Bi ₁ Gd _0.9 Lu _1.1 Fe ₅ O ₁₂ average particle diameter 470Å Composition 3 Bi ₁ Gd _0.7 Lu _1.3 Fe ₅ O ₁₂ average particle diameter 420Å After adding these three kinds of fine particle powders to an aqueous solution containing bismuth nitrate, yttrium nitrate and ferric nitrate in a molar ratio of Bi: Y: Fe = 28: 10: 62 and sufficiently dispersing them,
Amorphous BiYFe containing three types of garnet-type oxide fine particles is applied on a glass substrate having a diameter of 3 inches and a thickness of 0.5 mm and then thermally decomposed at 300 ° C.
An oxide film was formed. FIG. 1 shows a thin film composite system as a Faraday rotator according to one embodiment of the present invention. Reference numeral 14 denotes an amorphous oxide film containing three types of garnet-type oxide fine particles. The ratios of the garnet-type oxide fine particles of composition 1, composition 2 and composition 3 are 0.71, 0.165 and 0.125.
Reference numeral 15 denotes a glass substrate. In FIG. 1, the coating film is formed on only one surface of the substrate 15, but may be provided on both surfaces. FIG. 2 shows the absolute value of the Faraday rotatory power in the minus direction with respect to the substitution amount when the composition was changed by substituting the trivalent ion of Bi used in composition 2 and composition 3. In other words, FIG. 2 shows Y ₃ Fe ₅ O ₁₂ having a garnet-type crystal structure.
Is the magnitude of the Faraday rotation angle of a system in which is replaced by a trivalent ion of Bi. It can be seen that the Faraday rotation angle increases in the negative direction as the Bi substitution amount increases. The wavelength of the light used was 633 nm of a He-Ne laser. Y ₃ (ScGa) _0.7 Fe _4.3 O used in composition 1 at this time
₁₂ has a Faraday rotation capability of about 1/10 in the plus direction. FIG. 3 shows the Faraday rotability according to the temperature in the element thus configured. -Of this composite element
The fluctuation of the Faraday rotation angle between 20 ° C and 110 ° C is 0.76%
Became. Above all, a Faraday rotator having a temperature variation close to zero between 9 ° C. and 44 ° C. was obtained.

[0008]

As described above, according to the Faraday rotator of the present invention, an optical isolator for removing reflection noise which is a problem in an optical fiber communication system using a semiconductor laser can be constructed. Further, the Faraday rotator of the present invention is applied to a magnetic field sensor using the principle of an optical isolator,
Application to a waveguide type TM-TE mode conversion or a waveguide type optical isolator can be achieved. In addition,
The manufacturing technology of many optical element components including related optical devices is steadily progressing, and it is thought that high precision, high performance, high reliability, etc. will be achieved. The Faraday rotator material is exactly in this direction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a Faraday rotation element material according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a composition change of a material and a Faraday rotation ability in the example.

FIG. 3 is a diagram showing a relationship between temperature and Faraday rotation ability.

Claims (1)

(57) [Claims] 1. A Faraday rotator comprising a coating film formed by dispersing magnetic fine particles in a binder on a substrate, wherein the magnetic fine particles are of the general formula A ₃ B ₅ O ₁₂ (where A Represents one or more elements selected from a rare earth element which becomes a trivalent ion and Bi which becomes a trivalent ion, and B represents a transition metal which becomes a trivalent ion, Al, Ga, Sc and In which becomes a trivalent ion, and It is 3 by the combination of divalent-4 valence or divalent-5-valent
Represents one or more elements selected from valence elements. ) Is an oxide having a garnet type structure represented by the formula (1) and is composed of fine particles of two or more kinds having an average particle size of 30 to 1000 °, and combines the Faraday rotation ability of each fine particle in the plus direction and the minus direction. -20 ° C ~
A Faraday rotation element characterized in that the variation of the Faraday rotation angle between 110 ° C. is 0.76% or less.