JP3250111B2 - Magneto-optical disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a magneto-optical disk equipment, suitable magneto-optical disk equipment to read and write information optically by shortening the particular time required for recording with respect to an optical information medium About.

[0002]

2. Description of the Related Art A magneto-optical disk drive records and reproduces information on a magnetic thin film on a substrate in the form of magnetization by optical means. For laser light sources used in magneto-optical disk devices and magneto-optical tape devices, see Kenichi Iga, Fumio Koyama, co-author, `` Surface emitting laser '' issued by Ohmsha, or `` Ryoichi Ito, Michiharu Nakamura, co-editor, published by Baifukan Semiconductor laser ". In addition, Japanese Unexamined Patent Publication No.
Patent applications such as US Pat. No. 11,1783 and JP-A-3-18835 have been filed.

The magnetic effect of circularly polarized light is described in the journal "Journal of the Applied Magnetic Society" (1981, Vol. 5, No. 2, No. 1).
57 to 160).

[0004]

In a conventional magneto-optical disk device or magneto-optical tape device, when recording information,
Apply a magnetic field in a certain direction, irradiate light with a certain intensity to erase the information that was recorded once, and then apply a magnetic field in the opposite direction, and then irradiate light with modulated intensity to record It is carried out. In this method, recording of information takes time, and a magnetic head for applying a magnetic field is required.

An object of the present invention is to use a circularly polarized light at the time of recording information in a magneto-optical disk device, thereby omitting the process of once erasing the recorded information and reducing the time required for recording. with shortened by omitting the magnetic head, there <br/> number of parts and Herasuko.

[0006]

[0007]

[0008]

[0009]

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to provide a disk having a magnetic film on its surface and capable of recording information by irradiating light, a motor for rotating the disk, and a circularly polarized light as the light. A magneto-optical disk device comprising: a light source that emits laser light; and a lens that is positioned with respect to the rotating disk surface, and irradiates the disk surface with the laser light. Means for applying a magnetic field in a direction coincident with the propagation direction of light propagating in the active layer to the radiating active layer, and light having a function of changing the direction of the magnetic field and recording the information on the disk This is achieved by a magnetic disk drive.

[0011] Also, a laser light source, a first optical system for irradiating light emitted from the laser light source to an optical information medium, a photodetector for converting light into an electric signal, and transmission from the optical information medium A second optical system that guides light or reflected light to the photodetector, records information by irradiating the optical information medium with light, and reads information from transmitted light or reflected light from the optical information medium. In the optical pickup for reproducing information, the optical information medium is irradiated with circularly polarized light, and the information is recorded by switching between right circularly polarized light and left circularly polarized light.

In a magneto-optical disk drive for reading and writing information from and to a magneto-optical disk by an optical means from a laser light source, a coil for applying a magnetic field to an active layer of the laser light source is provided. Disk device.

Further, the magneto-optical disk has a quantum well structure which resonates with light incident upon recording.

In the magnetic disk, a multilayer thin film including a magnetic thin film on a base has a periodic multilayer structure, and the period is one quarter of the optical path length of the light incident upon recording. A magnetic disk device having the above configuration is provided.

Also, a magneto-optical disk, a spindle motor for rotating the magneto-optical disk, and recording of information by irradiating the magneto-optical disk with light, and detecting reflected light or transmitted light from the magneto-optical disk. An optical pickup for reproducing information and detecting a servo signal; and an optical pickup for irradiating a predetermined position on the magneto-optical disk with light emitted from the optical pickup. An actuator that moves a part of the spindle motor and the actuator based on a servo signal from the optical pickup and a signal from the outside to supply a current to the spindle motor and control the operation of the actuator. Modulates the light applied to the magneto-optical disk in accordance with the signal of A magneto-optical disc device having a system controller that outputs information reproduced by the optical pickup to the outside when reproducing the information, wherein the magneto-optical disk has a multilayer thin film including a magnetic thin film on a substrate; The structure of the thin film has a quantum well structure that resonates with light having a wavelength applied to the magneto-optical disk during recording, and the optical pickup includes a laser light source and light emitted from the laser light source. A first optical system for irradiating light to the magneto-optical disk, a photodetector for converting the light into an electric signal, and a second optical system for guiding transmitted light or reflected light from the magneto-optical disk to the photodetector
The laser light source, an active layer that emits light by passing a current, an electrode that supplies a current to the active layer, and a reflection that reflects the light emitted from the active layer And a resonator configured to face means around the active layer, wherein the active layer and the resonator are
The coil has an axially symmetric structure with respect to the optical axis of light that causes resonance in the resonator, and a coil for applying a magnetic field to the active layer is provided. The direction is the same as the direction of light propagating in the active layer.

Further, the magneto-optical disk has a multilayer thin film including a magnetic thin film on a substrate, and the structure of the multilayer thin film has a structure in which light having a wavelength applied to the magneto-optical disk during recording is irradiated.
The optical pickup has a quantum well structure that causes resonance, and a first light source that irradiates the magneto-optical disk with a laser light source and light emitted from the laser light source.
An optical system, a photodetector that converts light into an electric signal, and a second optical system that guides transmitted light or reflected light from the magnetooptical disk to the photodetector. Irradiating circularly polarized light on the optical disk and recording information by switching between right circularly polarized light and left circularly polarized light.

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

According to the above arrangement, when a magnetic field is applied to the active layer of the laser light source, a difference in energy level occurs depending on the direction of spin of electrons in the active layer. When the structure of the laser light source is substantially axially symmetric with respect to the optical axis, the gain of the active layer with respect to light becomes different between right-handed circularly polarized light and left-handed circularly polarized light due to this difference in energy level and the law of conservation of angular momentum. When the laser light source oscillates, the mode in which oscillation occurs is determined by a slight difference in gain. For this reason, when the structure of the laser light source is substantially axially symmetric with respect to the optical axis, circularly polarized light can be obtained by applying a magnetic field to the active layer, and the direction of the magnetic field applied to the active layer is reversed. Thereby, the polarization direction can be reversed.

When a substance absorbs circularly polarized light, the substance is magnetized in the optical axis direction of the incident light according to the law of conservation of angular momentum. The multilayer structure including the magnetic thin film has a quantum well structure that resonates with incident light at a wavelength, and the multilayer structure has a periodic structure. So that it becomes 1. Then, strong absorption occurs for incident light, and large magnetization can be generated. The direction of magnetization of the magnetic thin film can be changed by the magnetic field generated at this time.

In a magneto-optical disk drive, a laser light source emits circularly polarized light and its polarization direction is variable. Further, the magneto-optical disk has a quantum well structure that causes resonance with respect to light incident upon recording, and has a periodic multilayer structure. The period of the period is such that the optical path length of one period is four minutes of the wavelength of light incident upon recording. So that it becomes 1. Then, by switching the light emitted from the laser light source to right circularly polarized light and left circularly polarized light, it is possible to write magneto-optical disk information.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below with reference to the drawings. One embodiment of the present invention will be described with reference to FIGS. 1 is a schematic view of an optical system showing the principle of operation, FIG. 2 is an enlarged sectional view and a band diagram of a magneto-optical disk, and FIG. 3 is a partially enlarged view of FIG.

As shown in FIG. 1, the active layer 4 is sandwiched between Bragg reflectors 5 and 6 composed of semiconductor multilayer films having different compositions. The film thickness and composition of the Bragg reflectors 5 and 6 are selected so as to cause Bragg reflection with respect to light emitted from the active layer 4, and constitute a resonator. Electrode 8,
An electric current is supplied from 9 to the active layer 4 via the substrate 12 and the Bragg reflectors 5 and 6, and light is emitted from the active layer 4. The current is concentrated at the center of the active layer 4 by the insulating layer 7, and light emission mainly occurs at the portion where the current is concentrated. Light emitted from the active layer 4 resonates with the resonator constituted by the Bragg reflectors 5 and 6, and laser oscillation occurs.

The laser light source 1 is provided with coils 10 and 11. When a current flows through the coils 10 and 11, a magnetic field is generated, and a magnetic field in the optical axis direction acts on the active layer 4 and the Bragg reflectors 5 and 6. When a magnetic field acts, the active layer 4
The energy levels of the electrons in the Bragg reflectors 5, 6 are separated by their spin directions. The structure of the laser light source 1 is generally axially symmetric with respect to the optical axis, and both right circularly polarized light and left circularly polarized light can be emitted from the laser light source 1. However, due to the difference between the energy level due to the law of conservation of angular momentum and the direction of spin, there is a difference between the gain for the light of the active layer 4 and the reflectivity of the Bragg reflectors 5 and 6 for the right circularly polarized light and the left circularly polarized light.

In general, when a laser light source oscillates, a mode in which oscillation occurs is determined by a slight difference in gain. Therefore, by applying a magnetic field in the direction of the optical axis to the active layer 4, it is possible to generate circularly polarized light in a specific direction, and further by switching the direction of the magnetic field,
Right circular polarization and left circular polarization can be switched. Light emitted from the laser light source 1 is condensed by the objective lens 2 and is irradiated on the magneto-optical disk 3.

FIG. 2 is an enlarged sectional view and a band diagram of the magneto-optical disk 3. As shown in FIG. The vertical axis of the band diagram is the coordinate axis in the direction perpendicular to the magneto-optical disk, the horizontal axis is the energy of electrons, the left side is the valence band, and the right side is the conduction band. On the transparent substrate 13, a multilayer film in which semiconductor thin films 14 and dielectric thin films 15 are alternately deposited, a magnetic film 16, and a protective film 17 are provided. The semiconductor thin film 14 has a quantum well structure. A set of energy gaps whose transposition is not prohibited from each other is defined as Eg.
The thickness of the semiconductor thin film is determined so that the light emitted from the substrate causes resonance. This film thickness is several tens of nm, which is much smaller than the wavelength of ordinary light. The thickness of the dielectric thin film 15 is 、 of the wavelength when light emitted from the laser light source 1 propagates in the film, that is, the refractive index of the dielectric is n,
The wavelength of the light emitted from the laser light source 1 in vacuum is λ
Λ / 4n. Since the thickness of the semiconductor thin film is sufficiently small with respect to the wavelength, light absorption can be increased by doing so.

FIG. 3 is an enlarged view of the band diagram of FIG. 2 and shows how the semiconductor thin film 14 absorbs light. Only a set of levels that cause resonance with light emitted from the laser light source 1 will be considered. The valence band level includes an electron 19 having an upward spin and an electron 18 having a downward spin. Here, consider the case where the circularly polarized light 20 is incident. Circularly polarized light 20
Has angular momentum, ie, spin. For example, when light 20 having an upward spin is incident as shown in FIG. 3, this light 20 is absorbed by an electron 18 having a downward spin in a valence band, and the electron 18 is excited to a conduction band.
At this time, the excited electrons 18
Spins up. Similarly, the electrons 19 are not excited by the law of conservation of angular momentum. Before being absorbed, the number of electrons having an upward spin was the same as the number of electrons having a downward spin. After absorption, an electron having an upward spin was generated each time one electron was excited. Is increased by two. Since an electron has a negative charge, an upward spin becomes a downward magnetic moment. Due to the magnetic moment due to this spin imbalance,
The semiconductor thin film is magnetized and creates a magnetic field around it.

The temperature of the magnetic film rises due to light irradiation, and loses magnetism beyond the Curie point. Here, the light is weakened and the temperature is lowered. At this time, the magnetization direction of the magnetic film is determined by the magnetic field of the semiconductor thin film. In the generation of spontaneous magnetization due to a decrease in temperature, the symmetry of the system is spontaneously broken, and the direction of magnetization can be aligned even by a weak magnetic field. The spin of the irradiated light can be switched by switching between right circularly polarized light and left circularly polarized light. By switching the direction of spin, the direction of magnetization generated in the semiconductor film can be switched, and the direction of magnetization finally generated in the magnetic film can be switched.

Although the embodiment of the multilayer structure of the dielectric thin film and the semiconductor thin film has been described here, the same can be applied to a semiconductor multilayer film having a different composition. It is also possible to absorb circularly polarized light in a multilayer structure in which the magnetic film itself has a quantum well structure, and to switch the direction of magnetization depending on the generated magnetization.

Another embodiment of the present invention will be described with reference to FIGS. 4 is a perspective view of a magneto-optical disk drive using the present invention, FIG. 5 is a schematic view of an optical pickup optical system, FIG. 6 is a plan view of the optical pickup optical system, FIG. 7 is a perspective view of a laser light source, and FIG. It is sectional drawing of a laser light source.

The light emitted from the laser light source 21 shown in FIG. 4 enters the prism 22 provided with the diffraction grating 26.
This light is reflected by the diffraction grating 26, condensed by the objective lens 23, and irradiated onto the magneto-optical disk 24. The reflected light from the magneto-optical disk 24 passes through the objective lens, is diffracted by the diffraction grating 26, and is irradiated on the optical integrated circuit 25.

As shown in FIG. 5, the optical integrated circuit 25 has a structure in which a dielectric film 29 having a high refractive index is sandwiched between dielectric films 30 and 31 having a low refractive index on a silicon substrate 28. ing. A grating coupler 27 is provided in a portion where the light diffracted by the diffraction grating 26 is incident, and the incident light is converted into a dielectric film 2 having a high refractive index.
Lock it in part 9.

As shown in FIG. 6, optical waveguides 34, 35, 36 having a linear waveguide mirror 32 and a parabolic waveguide mirror 33 formed on a silicon substrate 28 by etching dielectric films 29, 30, 31. Is provided. Grating coupler 2 provided in waveguides 34 and 36
Numeral 7 indicates that the TE mode component of the incident light is confined in the dielectric film 29, and the grating coupler 27 provided in the waveguide 35 has the pitch and pattern so as to confine the TM mode component of the incident light in the dielectric film 29. Is determined. The optical waveguide 3 confined in the dielectric film 29
The light propagating in 4, 35 and 36 is reflected by the linear waveguide mirror 3
2. Reflected and condensed by the parabolic waveguide mirror 33, near the boundary between the photodetectors 37 and 38 provided adjacent to each other,
The light enters near the boundary between the photodetectors 39 and 40 and near the boundary between the photodetectors 41 and 42.

Since the TE mode component of the light incident on the grating coupler 27 propagates through the waveguides 34 and 36, the sum signal of the photodetectors 37, 38, 41 and 42 is taken, and the light enters the grating coupler 27. The TE mode component of the emitted light can be known. Since the TM mode component of the light incident on the grating coupler 27 propagates in the waveguide 35, the TM mode component of the light incident on the grating coupler 27 is obtained by taking the sum signal of the photodetectors 39 and 40. Can be. Therefore, the outputs of the photodetectors 37, 38, 39, 40, 41, and 42 are set as a, b, c, d, e, and f, respectively, and (a + b + e +
By taking the signal of f)-(c + d), the polarization direction of the light incident on the grating coupler 27 can be known. That is, when linearly polarized light is emitted from the laser light source 21, a magneto-optical signal can be obtained.

When the magneto-optical disk 24 is deviated from the focus by the objective lens 23, the focus near the boundary between the photodetectors 37 and 38 and the focus near the boundary between the photodetectors 41 and 42 are shown in FIG.
To move up and down. For example, when the magneto-optical disk 24 moves away from the position of the focal point with respect to the objective lens 23, the focal points near the photodetectors 37 and 38 move upward in FIG. 6 moves down. That is, the outputs of the photodetectors 38 and 41 increase, and the outputs of the photodetectors 37 and 42 decrease. When the magneto-optical disk 24 approaches the objective lens from the focal point, the opposite occurs. That is, by taking the signal of (a + f)-(b + e), a signal of defocus and a focus error signal can be obtained.

The focus of the objective lens is the magneto-optical disk 2.
4, the optical waveguides 34 and 36
And the amount of light incident on the grating coupler 27 provided in the above. That is, the sum signal of the photodetectors 37 and 38 and the sum signal of the photodetectors 41 and 42 relatively change.
That is, by taking the signal of (a + b)-(e + f), a signal of a deviation from the recording track and a track error signal are obtained.

As shown in FIG. 7, the laser light source 21 is provided with a light emitting section 45 for reproduction and a light emitting section 46 for recording. The light emitting section for reproduction 45 has an elliptical opening, and the light emitting section for recording 46 has a circular opening.

FIG. 8 is a sectional view of the laser light source 21.
At the time of reproducing information, a current is supplied from the electrodes 56 and 58 to the active layer 51 via the substrate 49 and the Bragg reflectors 52 and 53 made of a semiconductor multilayer film. At this time, current is collected near the Bragg reflector 53 of the active layer 51 by the insulating layer 55. Since the reproducing light emitting section 45 has an elliptical shape, linearly polarized light is emitted from the reproducing light emitting section 45. At the time of information recording, a current is supplied from the electrodes 57 and 58 to the active layer 51 via the substrate 49 and the Bragg reflectors 52 and 54 made of a semiconductor multilayer film. At this time, current is collected near the Bragg reflector 54 of the active layer 51 by the insulating layer 55. At the same time, current is also supplied to the coils 59 and 60, and a magnetic field in the optical axis direction is applied to the active layer 51. Because of the influence of the magnetic field and the circular shape of the recording light emitting unit 46, the recording light emitting unit 46 emits circularly polarized light. The polarization direction of this light can be changed by changing the direction of the magnetic field applied to the active layer 51.

The magneto-optical disk 24 has the same structure as the magneto-optical disk 3 described with reference to FIGS. 2 and 3, and can write in magneto-optical recording by injecting circularly polarized light. At the time of reproducing information, linearly polarized light emitted from the reproducing light emitting section 45 is used, and information is reproduced by changing the polarization direction due to the Kerr effect. Since no magnetization occurs with linearly polarized light, information is not destroyed.

In FIG. 4, commands for recording and reproducing information are input to the system controller 68 from the outside of the apparatus via a terminal 69. Regardless of whether the command is information recording or information reproduction, the system controller 68
A predetermined operation is performed on the outputs of 7, 38, 39, 40, 41 and 42 to detect a focus error signal and a track error signal. In response to these signals and a command from the outside of the apparatus, current is supplied to the coarse actuator 63 and the fine actuator 64 to move the focal point of the objective lens 23 to a predetermined position on the magneto-optical disk 24. At the same time, a current is supplied to the spindle motor 62 to rotate the magneto-optical disk 24.

When the command is information recording, the system controller 68 responds to the information to be recorded via the cable 67 to the electrode 57 of the laser light source 21 and the coil 5.
A current is supplied to 9 and 60 to perform writing. If the command is information reproduction, the system controller 68 supplies power to the electrode 56 of the laser light source 21 via the cable 67. Further, the photodetectors 37, 38, 39, 40, 4
A predetermined calculation is performed on the outputs from 1, 42 to detect a magneto-optical signal and output it to the outside of the device. The magneto-optical disk 24 is fixed by a magnet chuck 61 and can be easily detached.

[0046]

As described above, according to the present invention, high-speed writing in a magneto-optical disk drive can be realized, and a magnetic head can be eliminated to reduce the number of parts.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical system showing one embodiment of the present invention.

FIG. 2 is a sectional view and a band diagram of a magneto-optical disk showing one embodiment of the present invention.

FIG. 3 is a partially enlarged view of the band diagram of FIG. 2;

FIG. 4 is a perspective view of a magneto-optical disk drive showing one embodiment of the present invention.

FIG. 5 is a schematic view of an optical system of an optical pickup showing one embodiment of the present invention.

FIG. 6 is a plan view of an optical integrated circuit of an optical pickup optical system showing one embodiment of the present invention.

FIG. 7 is a perspective view of a laser light source showing one embodiment of the present invention.

FIG. 8 is a sectional view of a laser light source showing one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 laser light source 2 objective lens 3 magneto-optical disk 4 active layer 5, 6 Bragg reflector 7 insulating layer 8, 9 electrode 10, 11 coil 12 substrate 13 transparent substrate 14 semiconductor thin film 15 dielectric thin film 16 magnetic film 17 protective film 18, REFERENCE SIGNS LIST 19 electron 20 light 21 laser light source 22 prism 23 objective lens 24 magneto-optical disk 25 optical integrated circuit 26 diffraction grating 27 grating coupler 28 silicon substrate 29 high-refractive-index dielectric film 30, 31 low-refractive-index dielectric film 32 linear conduction Waveguide mirror 33 Parabolic waveguide mirror 34, 35, 36 Optical waveguide 37, 38, 39, 40, 41, 42 Photodetector 45 Light emitting unit for reproduction 46 Light emitting unit for recording 49 Substrate 51 Active layer 52, 53, 54 Bragg reflection Container 55 Insulating layer 56, 57, 58 Electrode 59, 60 Coil 61 Magne Tochakku 62 spindle motor 63 coarse actuator 64 fine actuator 67 cable 68 system controller 69 pin

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-203582 (JP, A) JP-A-55-58834 (JP, A) JP-A-63-187442 (JP, A) JP-A-61-1987 36985 (JP, A) JP-A-62-119992 (JP, A) JP-A-63-164032 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/125 G11B 11 / 10 H01S 5/06 H01S 5/183

Claims (5)

(57) [Claims] 1. A disk having a magnetic film on its surface and capable of recording information by being irradiated with light, a motor for rotating the disk, a light source for emitting circularly polarized laser light as the light, A lens positioned with respect to the rotating disk surface and irradiating the disk surface with the laser light, wherein the active layer provided on the light source for emitting light has the active layer; A magneto-optical disk device having means for applying a magnetic field in a direction coinciding with the propagation direction of light propagating in the layer, and a function of changing the direction of the magnetic field and recording the information on the disk. 2. A light source comprising: an active layer that emits light by passing an electric current; and a resonator in which means for reflecting light emitted from the active layer are arranged to face each other with the active layer interposed therebetween. 2. The magneto-optical disk drive according to claim 1, wherein said active layer and said resonator are arranged substantially symmetrically with respect to an optical axis of light emitted by causing resonance in said resonator. 3. The means for applying a magnetic field includes a coil, and switches the direction of the current flowing through the coil to switch the circularly polarized light between right circularly polarized light and left circularly polarized light, thereby converting the information into the light. 2. The magneto-optical disk device according to claim 1, wherein recording is performed on a magnetic disk. 4. The magneto-optical disk device according to claim 1, wherein the disk has a quantum well structure that resonates with light incident upon recording. 5. The disk has a periodic multilayer structure including a multilayer thin film including a magnetic thin film on a base, and the period is set so that the optical path length of one period is ４ of the wavelength of light incident upon recording. 2. The magneto-optical disk drive according to claim 1, wherein: