JPH01271946A - Magneto-optical reproducing head - Google Patents

Abstract

PURPOSE:To obtain a reproducing signal of large signal level even in the case of narrow track width by changing the change of the magnetization of a magnetic yoke into the change of the size of light and making it into the reproducing signal of a recording medium by the magneto-optical effect of the magnetic yoke. CONSTITUTION:At the time of reproducing, a signal magnetic field from the recording medium is led in a magnetic yoke 6 and the magnetization of the yoke 6 changes in accordance with the signal magnetic field. On the other hand, light from a laser diode 8 enters an optical waveguide path 7 and is polarized by a mode filter 12. This linearly polarized light is multiply reflected on the border of the yoke in an area just under the yoke 6 and the rotation of polarization plane by Kerr effect occurs. By repeating the multiple reflection, a Kerr rotation angle becomes larger to a size which can be detected as a signal. Polarized light which passes through the yoke 6 enter a photodetector 9 through a mode filter 13 and a reproducing signal is taken out. Thus, even in the case of the narrow track width, the reproducing signal of the large signal level can be obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magneto-optical reproducing head.

[Summary of the invention]

The present invention relates to a magneto-optical reproducing head for reproducing magnetization information of a recording medium, and the present invention relates to a magnetic yoke made of a magnetic material having a magneto-optic effect, an optical waveguide provided in contact with the magnetic yoke, and an optical waveguide. It has an optical input means for introducing linearly polarized light into the waveguide, and an optical detection means for detecting the output light from the optical waveguide. By reproducing the magnetization information of the recording medium instead of the change, it is possible to extract a reproduced signal with a high signal level even with a narrow track width.

[Conventional technology]

As a reproducing head for reproducing magnetization information from a magnetic recording medium, especially for a narrow track width of 10 μm or less,
2. Description of the Related Art Thin film magnetic heads such as an inductive type (so-called wire-wound) thin film magnetic head and an MR type magnetic head that utilizes a magnetoresistive effect (hereinafter referred to as MR) are known.

In an inductive thin film magnetic head, it is necessary to increase the number of windings in order to increase the reproduction signal, but this increases the space factor and reduces efficiency. Furthermore, when the relative speed with respect to the recording medium is low, the reproduced signal becomes small.

On the other hand, in the MR type magnetic head, the magnitude of the reproduced signal does not depend on the relative speed with the recording medium. However, when the track width becomes narrow, crosstalk from adjacent tracks becomes a problem in an MR type magnetic head in which the longitudinal direction of the MR element is parallel to the track width direction. Further, in an MR type magnetic head in which the longitudinal direction of the MR element is perpendicular to the track width direction, the function is to direct the magnetization to the easy axis in the track width direction when there is no external magnetic field.

[Problem to be solved by the invention]

The present invention provides a magneto-optical reproducing head which differs in operating principle from the conventional reproducing head described above and is capable of obtaining a large reproduction signal level even with a narrow track width.

[Means to solve the problem]

The magnetic optical reproducing head of the present invention includes a magnetic yoke (6) made of a magnetic material having a magneto-optic effect into which a signal magnetic field of a recording medium is introduced, and an optical waveguide (6) provided in contact with the magnetic yoke (6). 7), a light input means (8) for introducing linearly polarized light into the optical waveguide (7), and a light detection means (9) for detecting the output light from the optical waveguide (7).

[Effect]

During reproduction, a signal magnetic field from the recording medium (1) is introduced into the magnetic yoke (6), and the magnetic yoke (6)
) changes in magnetization. On the other hand, linearly polarized light is introduced into the optical waveguide (7) from the optical input means (8). Linearly polarized light propagates within the optical waveguide (7), and in the region directly below the magnetic yoke (6), it proceeds while undergoing multiple reflections at the boundary with the magnetic yoke (6), and this multiple reflection causes rotation of the plane of polarization due to the Kerr effect. . The linearly polarized light (22) passes through the optical waveguide (7) directly under the magnetic yoke (6).
), the Kerr rotation angle of the polarization plane becomes large enough to be detected as a signal. Then, the output light from the optical waveguide (7) enters the photodetecting means (9), from which a reproduced signal is obtained.

That is, in this configuration, the magnetization information of the recording medium (1) is reproduced by changing the magnetization of the magnetic yoke (6) into a change in the magnitude of light through the optical waveguide (7).

〔Example〕

Embodiments of the magneto-optical reproducing head according to the present invention will be described below with reference to the drawings.

1 to 4 show an example of the magneto-optical reproducing head of the present invention. In the figure, (1) shows a recording medium, such as a magnetic recording medium, and (2) shows a magneto-optical reproducing head according to the present invention.

As the magnetic recording medium (1), either a magnetic recording medium magnetized in the in-plane direction or a magnetic recording medium magnetized in the perpendicular direction can be applied. The magneto-optical reproducing head (2) has a first
As shown in the figure, the lower magnetic yoke (4) and the upper magnetic yoke (5) are placed on the insulating head substrate (3). ), and an optical waveguide (7) passing through the lower magnetic yoke (4) and upper magnetic yoke (5) of the magnetic yoke (6) in the track width direction is formed, and the optical waveguide (7)
A semiconductor laser diode (8) serving as a light source and a photodetector (9), such as a PIN photodiode or an avalanche photodiode, for detecting output light from the optical waveguide (7) are arranged at one end and the other end, respectively. Become. The insulating head substrate (3) on which the photodetector (9), the laser diode [8), the magnetic yoke (6), and the optical waveguide (7] are formed is provided on the base substrate (21).The magnetic yoke (6) ) is formed of a magnetic material having a magnetic Kerr effect, such as Fe, Co, Ni, Par70, MnB1, etc.The optical waveguide (7) is formed of a magnetic material having a magnetic Kerr effect, such as Fe, Co, Ni, Par70, MnB1, etc.The optical waveguide (7) is formed of one side of the yoke, for example, the upper magnetic York (5
), and the upper magnetic yoke (5) and the optical waveguide (7
) so that light is propagated while undergoing multiple reflections at the boundary. Further, the optical waveguide (7) can be placed close to the magnetic gap (the tip where the pine is formed) of the magnetic yoke (6).

The light emitted from the laser diode (8) is linearly polarized light with a plane of polarization parallel to the active layer, and the polarization ratio representing the degree of linear polarization is 80 to 10 degrees. This laser light is introduced into the optical waveguide (7). For example, the optical waveguide (7) is made by immersing soda glass in a solution of KNO and removing Na in the glass.
It is composed of an ion-exchange waveguide that traps and propagates light by making the refractive index larger than the outer part, so-called substrate (10), which will be described later, by exchanging ``'' ions and K'' ions.Other optical waveguides (7) include For example, Ti diffusion 1iNb0 made by diffusing Ti into an optically anisotropic substrate such as L+NbO, crystal, etc.
It can also be configured with three waveguides. (10) is a glass substrate or LiNb0. A crystal substrate is shown. Also (11
) indicates insulators such as Sin, which serve as spacers formed on both sides of the magnetic yoke (6).

On the other hand, the laser diode (8) is linearly polarized light with a sufficient polarization ratio, but in order to maximize the reproduced signal as described later, the distance between the magnetic yoke (6) of the optical waveguide (7) and the laser diode (8) is A metal clad mode filter (12) serving as a polarizer and a metal clad mode filter (13) serving as an analyzer are provided between the magnetic yoke (6) and the photodetector (9), respectively. These metal clad mode filters (12) and (13) are shown in Fig. 3 (B in Fig. 1).
As shown in FIG. 4 (cross-sectional view along line C-C in FIG. 1), for example,
For example, metal layers (16) (17), such as first grade, are deposited through buffer layers (14), (15) made of insulating layers such as . The metal clad mode filter (12) serving as a polarizer and the metal clad mode filter (13) serving as an analyzer are formed so that the angle between them is 45° or a predetermined angle close to 45°. do. That is, for example, the metal clad mode filter (12) which serves as a polarizer has its metal layer (16) and buffer layer (14) on the reference plane (for example, the plane of the 5 in 2 insulator (11)), as shown in FIG. (1g), and the metal clad mode filter (13) that serves as an analyzer has its metal layer (17) and buffer layer (15) on the reference plane, as shown in Figure 4. (18) at an angle of β, in which case α + β = 45° or α + β;
The angle is 45°. In the illustrated example, metal layers (16) (17) and buffer layers (14) (1) are used as metal clad mode filters (12) and (13).
5), angles α and β were added to satisfy α+β−45° or α+β−45°, but other angles α−0,
The metal clad mode filters (12) and (13) may be configured so that β=45° or β;45°. Here, a metal layer (16) is placed on the optical waveguide (7).
(17) By forming (TE mode transmission, T
This results in M mode absorption.

Next, the operation of the magneto-optical reproducing head having such a configuration will be explained.

During reproduction, signal magnetic flux from the magnetic recording medium (1) is introduced into the magnetic yoke (6) as shown in FIG. The magnetization (M) of the magnetic yoke (6) changes depending on the signal magnetic flux. On the other hand, the light emitted from the laser diode (8) enters the optical waveguide (7) and is polarized by the metal clad mode filter (12), which is a polarizer, so that the plane of polarization faces in the direction of arrow a in Figure 3. Ru. This linearly polarized light (22) is transmitted by the magnetic yoke (
6) In the optical waveguide area immediately below, as shown in FIG. Proceed while reflecting. At this time, the polarization plane of the linearly polarized light (22) varies from angle 10 to angle - depending on the direction of magnetization of the upper magnetic yoke (5).
Kerr rotation of θ occurs, and in particular, multiple reflections cause the Kerr rotation angle of the polarization plane to become large (so large that it can actually be detected as a signal.Then, the linearly polarized light (22) passing directly under the magnetic yoke (6) cannot be detected. The metal clad mode filter (13), which is a photon, enters the analyzer's metal clad mode filter (13).If the sum of the angles α and β shown in FIGS. 13) The subsequent change in light output (with Kerr rotation angle ±θ) is cos2(ψ1θ)−cos2(ψ−θ)=−2si
It is proportional to n(2ψ)sin(2θ), and by setting it near ψ-45°, the degree of change in °C becomes maximum. Then, the output light that has passed through the metal clad mode filter (13) of the analyzer is received by a photodetector (9), from which, for example, differential detection is performed and a reproduced signal is extracted as an electrical signal.

In addition, when the optical waveguide (7) is configured to be in contact with the upper magnetic yoke (5) and the lower magnetic yoke (4), as shown in FIG. In 4), since the directions of the magnetizations M are opposite to each other, the rotation of the plane of polarization cancels each other out due to the upper and lower reflections in FIG. Therefore, in the present invention, the optical waveguide (7) is brought into contact with one side, for example, the upper magnetic yoke (5), and the upper magnetic yoke (5) is brought into contact with the optical waveguide (7).
5) Make it reflect at the boundary with.

According to the magnetic optical reproducing head having such a configuration, the magnetization information of the magnetic recording medium is reproduced by converting the change in the magnetization of the magnetic yoke into a change in the magnitude of the light, so the magnitude of the reproduced signal is different from that of the magnetic recording medium. Depends on the relative speed of the heads. The linearly polarized light introduced into the optical waveguide is multiple-reflected at the boundary with the magnetic yoke, and the Kerr rotation angle of the polarization plane increases, allowing it to be extracted as a large signal. A reproduced signal of signal level can be obtained. In addition, high output can be expected by arranging the optical waveguide (7) close to the magnetic gap (close to the tip of the hot water) where the amount of change in magnetization is large.

In the above example, the present invention is applied to a so-called ring-type head in which the magnetic yoke is formed into a closed magnetic path, but it can also be applied to other single-pole type heads in which the magnetic element has a single magnetic pole.

Further, in the above example, it is also possible to wrap a coil around the magnetic yoke (6) so that it also functions as an inductive recording head.

[Effects of the Invention] According to the above-described magnetic optical reproducing head of the present invention, the magneto-optic effect of the magnetic yoke is used to convert changes in the magnetization of the magnetic yoke into changes in the magnitude of light, thereby obtaining magnetization information of the recording medium. It's playing. Therefore, even in the case of a narrow track width, a reproduced signal with a high signal level can be obtained. Further, the magnitude of the reproduced signal does not depend on the relative speed between the recording medium and the head.

Furthermore, high output can be expected by arranging the optical waveguide close to the tip of the magnetic yoke that faces the recording medium.

[Brief explanation of the drawing]

1 is a perspective view showing an example of a magneto-optical reproducing head according to the present invention, FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1, FIG. 3 is a cross-sectional view taken along the line B-B in FIG. 1, Figure 4 shows C-C in Figure 1.
FIG. 5 is a cross-sectional view along the line for explaining the operation. (1) is a magnetic recording medium, (2) is the entire magneto-optical reproducing head of the present invention, (4) is a lower magnetic yoke, (5) is an upper magnetic yoke, (6) is a magnetic yoke, and (7) is Optical waveguide, (
8) is a laser diode, (9) is a photodetector, (12>
, (13) is a metal clad mode filter. Same as Hide Matsukuma to Mori Aku-ki.
Figure 1

Claims (1)

[Claims] A signal magnetic field of a recording medium is introduced, and linearly polarized light is introduced into a magnetic yoke made of a magnetic material having a magneto-optical effect, an optical waveguide provided in contact with the magnetic yoke, and the optical waveguide. A magneto-optical reproducing head comprising: a light input means for detecting the output light from the optical waveguide; and a light detection means for detecting the output light from the optical waveguide.