JPH05134221A - Magneto-optical material and production thereof and optical element formed by using this process - Google Patents

Abstract

PURPOSE:To obviate the deterioration in characteristics in spite of a change in the wavelength of a light source and obtain the characteristics sufficient for attaining wavelength multiplex communication by using the bismuth-substd. TbIG expressed by specific formula as a main component compsn. CONSTITUTION:The main component compsn. is expressed by formula I. In the formula I, R denotes a rare earth element or yttrium exclusive of terbium; M denotes gallium, aluminum, indium, etc.; x, y and z are respectively 0.16<=x<=0.18, 1.5<=y<=2.84, 0<=z<=0.3. The bismuth-substd. TbIG can be grown by a flux method, liquid phase epitaxy, etc., of the single crystal. Faraday rotating angles are equaled at about 1.1 to 1.6mum wavelength which can be used in optical communication if the bismuth substitution quantity is within a range from 0.16 to <0.18 per molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a magneto-optical material having extremely good wavelength characteristics, a method for manufacturing the same, an optical isolator, an optical circulator, a magnetic field sensor, an optical switch, etc. using the same. Regarding the optical element of.

[Conventional technology]

In optical communication, optical elements such as optical isolators for long wavelengths in the 1.3 μm band and 1.55 μm band are used for the bismuth-substituted gadolinium iron garnet with a large Faraday effect manufactured by the flux method or floating zone method. _{(Gd 3-x Bi x Fe} 5 O 12;. hereinafter referred to as CdBiIG) or yttrium iron garnet (. hereinafter mounting serial and YIG) the Faraday rotator is used to using a single crystal.

[Problems to be Solved by the Invention]

 However, GdBiIG and YIG have the drawback that the characteristics of optical elements such as optical isolators deteriorate or cannot be used when the wavelength of the light source changes because the wavelength of the Faraday rotation angle changes greatly.

 Furthermore, in the wavelength division multiplexing method, in which light of different wavelengths is transmitted using the same optical fiber in order to increase the transmission capacity in optical communication, the optical isolator for 1.3 μm band cannot be used at the wavelength of 1.55 μm. Further, there is a serious problem that the one for the 1.55 μm band cannot be used at a wavelength of 1.3 μm.

 Therefore, even if the wavelength of the light source changes, the characteristics are not deteriorated, and it is desired to develop an optical element having sufficient characteristics for realizing wavelength division multiplexing communication.

[Means for Solving the Problems]

The inventors of the present invention have developed various materials for the purpose of developing materials having the same Faraday rotation angle at several wavelengths and developing optical elements such as optical isolators having excellent characteristics in a wide wavelength band. As a result of growing a rare earth iron garnet and measuring its magneto-optical effect, terbium iron garnet (Tb ₃ Fe ₅ O ₁₂ ; hereinafter referred to as TbIG) substituted with bismuth and an optical element using the same were used. The inventors have found that the above object can be achieved and reached the present invention.

That is, the gist of the present invention, the main component composition, in _{Tb y Bi x R 3- (x} + y) Fe 5-z M z O 12 ( wherein, R, or rare earth elements except terbium represents yttrium, M Represents gallium, aluminum, indium, chromium or cobalt, and x, y and z are 0.16 ≦ x ≦ 0.18, 1.5 ≦ y ≦ 2.84, 0 ≦ z ≦ 0. 3) The magneto-optical material, the method for manufacturing the same, and the optical element using the same.

 Hereinafter, the present invention will be described in detail.

Magneto-optical material of the present invention, the main component composition, a bismuth-substituted TbIG represented by _{Tb y Bi x R 3- (x} + y) Fe 5-z M z O 12.

 The bismuth substitution amount is in the range of 0.16 or more and less than 0.18 per molecule. When the bismuth substitution amount is within this range, the Faraday rotation angle becomes equal at two wavelengths within the wavelength range of about 1.1 μm to 1.6 μm that can be used in optical communication. In particular, when the bismuth substitution amount is 0.18 (Example 2), considering that the wavelength change under the normal use condition of the semiconductor laser is ± 0.02 μm or less, it is currently used in optical communication. It is very preferable because the Faraday rotation angles are equal at two wavelengths of 1.31 ± 0.02 μm and 1.55 ± 0.02 μm.

 In the present invention, gallium, aluminum, indium, cobalt, chromium, etc. may be replaced with iron sites as long as they contain terbium and bismuth in an appropriate amount ratio. In this case, the substitution amount is preferably 0.3 or less per molecule. It is also possible to substitute other rare earth elements on the terbium site.

 By substituting gallium, aluminum, indium, cobalt, chromium, or a rare earth element in this way, the saturation magnetic field can be reduced and the magnetic properties can be improved.

 The bismuth-substituted TbIG of the present invention can be grown as a single crystal by a flux method, a liquid phase epitaxial method, a bridgeman method, a Czochralski method, or the like. It can also be manufactured as a polycrystalline body by a sintering method. Particularly, it is preferable to grow a single crystal by the flux method and the liquid crystal epitaxial method.

In the case of the flux method, a flux such as lead oxide (PbO), boron oxide (B ₂ O ₅ ), lead fluoride (PbF ₂ ), bismuth oxide (Bi ₂ O ₃ ), potassium fluoride (KF) ( Flux) is used to dissolve the crystal raw material, make a saturated solution at high temperature, and gradually cool this solution to precipitate and grow a single crystal.

In the case of the liquid phase epitaxial method, Gd ₃ Ca ₅ O ₁₂ , (GdCa) ₃ (GaMgZr) ₅ O ₁₂ , S
A nonmagnetic garnet substrate such as m ₃ Ga ₅ O ₁₂ is brought into contact with a saturated solution prepared in the same manner as in the flux method to epitaxially grow a single crystal film on the substrate. If the difference in lattice constant between the substrate and the single crystal film is large, cracks will occur in the single crystal film, so it is necessary to select a substrate that matches the lattice constant of the single crystal film to be grown.

 By using the bismuth-substituted TbIG thus obtained, it is possible to manufacture an optical element having excellent characteristics in a wide wavelength band and capable of wavelength division multiplexing communication.

 Examples of such an optical element include an optical isolator, an optical circulator, an optical switch and a magnetic field sensor.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the Examples without departing from the gist thereof.

Example 1 A single crystal having a composition of Tb _2.84 Bi _0.16 Fe ₅ O ₁₂ was grown by a flux method.

 The obtained single crystal was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical device.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, the Faraday rotation angle was 45 degrees even when the wavelength was 1.18 μm.

A single crystal having the composition of Example _{2 Tb 2.82 Bi 0.18 Fe 5 O} 12 was grown by the flux method.

 The obtained single crystal was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical device.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, the Faraday rotation angle was 45 degrees even when the wavelength was 1.31 μm.

Comparative Example 1 A single crystal having a composition of Tb _2.76 Bi _0.24 Fe ₅ O ₁₂ was grown by the flux method.

 The obtained single crystal was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical device.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, there was no wavelength at which the Faraday rotation angle was 45 degrees in the wavelength range of 1.1 μm to 1.6 μm.

Comparative Example 2 A single crystal having a composition of Tb _2.49 Bi _0.51 Fe ₅ O ₁₂ was grown by the flux method.

 The obtained single crystal was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical device.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, there was no wavelength at which the Faraday rotation angle was 45 degrees in the wavelength range of 1.1 μm to 1.6 μm.

Comparative Example 3 A single crystal having a composition of Tb _2.31 Bi _0.69 Fe ₅ O ₁₂ was grown by the flux method.

 The obtained single crystal was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical device.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, there was no wavelength at which the Faraday rotation angle was 45 degrees in the wavelength range of 1.1 μm to 1.6 μm.

Comparative Example 4 A single crystal having a composition of Y ₃ Fe ₅ O ₁₂ was grown by the flux method.

 The obtained single crystal was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical device.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, there was no wavelength at which the Faraday rotation angle was 45 degrees in the wavelength range of 1.1 μm to 1.6 μm.

 FIG. 1 shows the wavelength dependence of the absolute value of the Faraday rotation angle of the magneto-optical elements obtained in Examples 1 and 2 and Comparative Examples 2 to 4.

Example 3 _Sm 3 _Ga 5 _{O 12} single crystal substrate, a PbO _Bi 2 _{O 3 KeiToruzai,} Tb _{2.82 Bi 0.18} F
A single crystal film having a composition of e ₅ O ₁₂ was grown by a liquid phase epitaxial method.

 The obtained single crystal film was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical element.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, the Faraday rotation angle was 45 degrees even when the wavelength was 1.31 μm.

Example 4 _Sm 3 in _Ga 5 _{O 12} single crystal substrate, PbO- _Bi 2 _{O 3 Tb} from KeiToruzai 2.82 _{Bi 0.18} Fe
A single crystal film having a composition of _4.85 Ga _0.15 O ₁₂ was grown by a liquid phase epitaxial method.

 The obtained single crystal film was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.53 μm and used as a magneto-optical element.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, the Faraday rotation angle was 45 degrees even when the wavelength was 1.29 μm.

Example 5 _Sm 3 _Ga 5 _{O 12} single crystal substrate, PbO- _Bi 2 _{O 3} KeiToruzai from _Tb 2.53 _{Gd 0.30} Bi
A single crystal film having a composition of _0.17 Fe ₅ O ₁₂ was grown by a liquid phase epitaxial method.

 The obtained single crystal film was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.57 μm and used as a magneto-optical element.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, the Faraday rotation angle was 45 degrees even at a wavelength of 1.33 μm.

Comparative Example 5 A single crystal film having a composition of Tb _2.19 Bi _0.81 Fe ₅ O ₁₂ was grown on a (GdCa) ₃ (GaMgZr) ₅ O ₁₂ single crystal substrate by a liquid phase epitaxial method.

 The obtained single crystal film was standardized to have a Faraday rotation angle of 45 degrees at a wavelength of 1.55 μm and used as a magneto-optical element.

 When the wavelength dependence of the Faraday rotation angle of the obtained magneto-optical element was measured, there was no wavelength at which the Faraday rotation angle was 45 degrees in the wavelength range of 1.1 μm to 1.6 μm.

Example 6 In order to investigate the peculiar phenomenon that the Faraday rotation angle becomes equal at two wavelengths, the Faraday rotation angle was measured up to a wavelength of 2 μm for the magneto-optical element obtained in Example 1. As a result, the Faraday effect (there are peaks at wavelengths of 1.74 μm, 1.82 μm, and 1.84 μm) due to the transition of the Tb ion from the ground state ⁷ F ₆ to the excited states ⁷ F ₀ and ⁷ F ₁ . Was measured. It was found that θ _F is negative on the shorter wavelength side than 1.74 μm, and this is superposed on the negative Faraday effect due to the contribution of bismuth extending from the shorter wavelength to the longer wavelength.

〔The invention's effect〕

 According to the present invention, since it can be shared in two wavelengths having the same Faraday rotation coefficient, it can be used as an optical element such as an optical isolator, an optical switch, an optical circulator, and a magnetic field sensor for wavelength multiplexing communication, and thus can be industrially used. Very useful.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a drawing showing the wavelength dependence of the absolute value of the Faraday rotation angle of the magneto-optical elements obtained in Examples 1-2 and Comparative Examples 2-3.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiko Tamaki 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Japan Broadcasting Corporation

Claims (4)

[Claims] 1. A main component _{composition, Tb y Bi x R 3- (} x + y) Fe 5-z M z O
₁₂ (wherein R represents a rare earth element other than terbium or yttrium, M represents gallium, aluminum, indium, chromium or cobalt. X, y and z are each 0.16 ≤ x ≤ 0 .18, 1.5 ≦ y ≦ 2.84, 0 ≦ z ≦ 0.3). Wherein the main component _{composition, Tb y Bi x R 3- (} x + y) Fe 5-z M z O
₁₂ (wherein R represents a rare earth element other than terbium or yttrium, M represents gallium, aluminum, indium, chromium or cobalt. X, y and z are each 0.16 ≤ x ≤ 0 18.18, 1.5 ≦ y ≦ 2.84, 0 ≦ z ≦ 0.3 A method for manufacturing a magneto-optical material, characterized in that the single crystal is manufactured by a flux method. To 3. A non-magnetic garnet substrate, the main component _{composition, Tb y Bi x R 3- (} x + y) Fe 5-z M z O
₁₂ (wherein R represents a rare earth element other than terbium or yttrium, M represents gallium, aluminum, indium, chromium or cobalt. X, y and z are each 0.16 ≤ x ≤ 0 .18, 1.5 ≦ y ≦ 2.84, and 0 ≦ z ≦ 0.3) are grown by a liquid phase epitaxial method. 4. An optical element using the magneto-optical material according to claim 1.