DE4447765C2 - Floating optical head integral with light source and photodetector - Google Patents

Abstract

Light from the laser (1) passes through the substrate (2), a first transparent layer (3), a diffraction grating (4), and a second transparent layer (5). The light is focussed by a condenser lens (6) onto a point directly below the lens. A spot of light is formed on an optical storage medium below the condenser lens. The reflected light passes through the condenser lens and second transparent layer and is diffracted by the grating to the light receiving plane of the photodetector. The reflected light passes through the first transparent layer to be received by the photodetector.

Description

The invention relates to an optical head, a method to manufacture such and an optical disk device.

Optical heads, more precisely optical scanning heads, are known from the prior art, for. B. from JP-A-64-46242 and from JP-A-64-43822.

The optical head described in JP-A-64-46242 is so on built that a surface emitting laser and a Pho Todetektor are formed on the same substrate, glass plates stacked or stacked on this substrate are laminated and a focusing grating coupler (Hologram lens) on the surface of a glass plate forms is.

On the other hand, the one described in JP-A-64-43822 is optical Head designed so that the head just described as Main body is used for the optical head and this Main body attached to a floating slide is.  

A focusing grating coupler is used in the optical head described in JP-A-64-46242. In the case of such a coupler, the chromatic aberration is large when the wavelength of the light from the light source changes due to temperature changes or the like. Although this document describes that there is no change in wavelength when a surface emitting laser is used, there is an adverse effect that the wavelength changes depending on temperature, as can be seen from the publication by Iga under the title "Surface Emitting Laser", published in: Applied Physics, 1991, Vol. 60, No. 1, p. 8, Fig. 12. Accordingly, this prior art has the difficulty that no measure against wavelength changes is taken.

Furthermore, the optical described in JP-A-64-46242 Head the optical path inclined towards the optical disc the optical path of the surface emitting laser laser light emitted from the opti towards the optical plate to separate the path for the light from the optical one Plate is returned to the photodetector. If the optical Path is inclined, there is a difficulty that aberration and asymmetrical distribution of strengths also occur easily can, resulting in a large spot diameter of the laser light leads. It should be noted that the use of a SCOOP Structure proposed in this prior art to take into account the difficulties that arise from the inclined optical path. However, in In the case of a SCOOP structure, only differences regarding Re flexibility properties of the medium can be recorded, there are disadvantages in that neither the tracking signal still the optomagnetic signal can be detected.

On the other hand, it is the one described in JP-A-64-43822 optical head because the optical head is separated on one  manufactured floating slide is attached, very difficult, the slide surface and the opti head within the normal focus depth of 2 to 3 µm. When automatic focus control is off would lead to this adjustment of the focal depth not mandatory. However, since JP-A-64-43822 The task is that this automatic focus control is not is carried out, the above must be difficult Focus depth adjustment can be performed.

It is also noted that JP-A-64-43822 is not a ver drive using to manufacture an optical head a surface emitting laser and also no opti cal disc device disclosed for a floating op table head is suitable.  

EP 0 501 477 A2 describes a floating head, which as magnetic or optical read / write head can be. The problems related to the swimming height and their adjustment as well as the focusing of an optical one The read / write head is not mentioned here.

US-4,876,680 A describes a compact integrated opti head, which may include mirrors and detectors.

OBJECT OF THE INVENTION

An object of the present invention is to provide a floating optical head specifying no special setting required. This object is achieved by a device according to claim 1. The subclaims relate to advantageous refinements of the invention.

A first embodiment of the invention gives an optical Head on, capable of chromatic To reduce aberration as it arises when the Wavelength of light emitted by a light source changes due to temperature changes.

A second embodiment of the invention provides an improved one optical head, which explained the above through the SCOOP structure and by tilting the optical Paths related to an optical disc Can avoid difficulties.  

A third embodiment of the invention provides a method for Manufacture an optical head using a surface emitting laser.

Another exemplary embodiment specifies an optical disk device, that for use with a floating opti head is suitable.

According to a first aspect of the invention, there is provided an optical head in which a semiconductor laser is formed on a substrate via a buffer layer and an opening section in the substrate is produced in part under the laser light-emitting surface,

• - The opening section further with a transparent Layer is filled, and
• - a grating lens, a lens with a distributed refractive index or a condenser lens made from a convex lens with a Diameter less than 1 mm at the bottom of the transparent Layer is formed.

According to a second aspect of the invention, there is provided an optical disc in which a semiconductor laser and a photodetector are formed on a buffer layer on the same substrate in such a manner that the laser light emitting surface of the semiconductor laser and the light receiving surface of the photodetector are oriented in the same direction are, with an opening under the laser light emitting surface and the light receiving surface, further having the following properties:

• - It is a first transparent layer for filling the Stacked opening portion;
• - A diffraction grating is on the underside of the first trans parent layer formed;
• - A second transparent layer is on the bottom stacked the first transparent layer; and  
• - a condenser lens consisting of a grating lens, a Distributed refractive index lens or a convex lens is on the underside of the transparent layer educated;
• - Wherein laser light emitted by the semiconductor laser through the Substrate, the first transparent layer, the diffraction grating and the second transparent layer is irradiated and to a location directly under the condenser lens of the the same is bundled, creating a spot of light on one Optical storage medium is formed by the Kon the lens is spaced below this, whereas from reflected light reflected by the optical storage medium the condenser lens and the second transparent layer is transmitted through, from the diffraction grating to light reception plane of the photodetector is deflected by diffraction and further through the first transparent layer is emitted to be received by the photodetector.

According to a third aspect of the invention is a created optical head, which is designed so that it integrally forms a floating slide.

According to a fourth aspect of the invention, there is provided a method of manufacturing an optical head in which a semiconductor laser and a photodetector are formed over a buffer layer on the same substrate in such a manner that the laser light emitting surface of the semiconductor laser and the light receiving surface of the photodetector are in are aligned in the same direction, and an opening is formed under the laser light emitting surface and the light receiving surface by an etching process, characterized by the following steps:

• - Stack the first one, use it to fill the opening det transparent layer by a plasma CVD or Sputtering process;  
• - Create a second transparent layer under the first transparent layer by a plasma CVD or Sputtering process and
• - Make either a grating lens on the bottom the second transparent layer by exposure process with photomask or a lens with spread Bre index or a convex lens at the bottom of the second transparent layer by ion exchange process.

Furthermore, an embodiment of the invention is by the method according to claim Given 12 for manufacturing an optical head.

According to a fifth aspect of the invention, a Optical disk device the features of claim 10.

In the optical head according to the first appearance of the Invention, the attenuation of the laser light is reduced because the semiconductor laser is manufactured over the buffer layer and the opening in the lower portion of the laser light emits renden surface is formed. As discussed above, becomes a condenser lens with a diameter of at most about 1 mm at the bottom of the applied to the substrate stacked transparent layer. If the through knife of the condenser lens is selected so that it is higher is at least about 1 mm, as explained later an accuracy of the wavefront of 0.1λ even then can be realized when wavelength changes Δλ = 3 nm wear so that no difficulty with chromati aberration exists as they change by wavelength conditions caused by the light source emitted light due to temperature changes is coming.

In the optical head according to the second manifestation of  Invention is a diffraction grating between the semiconductor laser and the condenser lens available, and that from the Kon Densor lens emitted and from the optical storage medium reflected light falls on this condenser lens again, whereupon it on the light receiving surface of the photodetector is steered, which is capable of a guidance signal and the optomagnetic signal. As a result of which this optical head can do the conventional Schwie overcome the difficulties caused by the fact that the optical path is set inclined to the optical disk and that a SCOOP structure was used.

In the optical disk according to the third aspect The invention is a one-piece floating slide formed with the main body of the optical head, and the Film thickness of a ceramic material such as zirconium oxide controlled, the production by a sputtering process takes place so that no positioning adjustment between the floating slide and the optical head more is required.

In the method of manufacturing an optical head according to the fourth aspect of the invention can be invented optical head according to the invention are produced in that a semiconductor process such as a photomask exposure process is used. Also, both the surface medium The laser and the photodiode are manufactured simultaneously will.

In the optical disk device according to the fifth appearance form of the invention are a floating optical head, whose swimming height corresponds to a maximum of approximately 20 µm, so as the optical disk mentioned below. The optical plate either has no protective layer on it Information reading page of their storage area or a transparent one  Protective layer whose thickness is less than a value is obtained by the fact that the swimming height of the back focal length of the object lens within a Medium, whose refractive index is 1.0, is subtracted and the subtraction result with the refractive index the protective layer is multiplied. As it explains later if the swimming height is below 26 µm, the change in swimming height below 2.6 microns, so that this Change in the focal depth of the condenser lens is compensated can be. As a result, the recording area can be without Focus deviation control can be read. If the thickness of the Protective layer becomes thin, the optical disc can through Dust will be damaged. However, since this is dustproof ten cassette is included, there is no problem with Ver apply the optical disk in practice.

According to another aspect of the invention is on a head for writing and / or reading at least one very small mirror surface, either in shape a separate mirror or in the form of a surface a magnetic pole. This reflective surface allows reading and Write magnetic domains with a diameter of only about 0.1 µm, in contrast to the 0.8 to 1 µm. The mirror surface is preferably used as a cutting plane through a laminate layer with a thickness of e.g. B. 0.1 µm produced. As a result, the width of the mirror surface is only 0.1 µm. If now laser light from the back of an op table plate on such a mirror surface on one optical head is blasted, the light on this Mirror surface standing just above the front of the plate surface, which makes it particularly high locally Heating the recording layer of the disc in that Area comes that faces the reflecting surface. This allows information to be provided by a thermo-magnetic Effect can be recorded. The size of the area increased  Temperature and thus the size of a magnetic domain does not depend on the size of the laser beam spot, but on the size of the reflecting surface. The power of the laser beam is set so that where the plate only with the laser beam is illuminated, the temperature is not so is greatly increased that a magnetic reversal can take place. Only where there is additional light on the panel because it is is reflected by the mirror surface mentioned, the increases Temperature to sufficiently high values.

This principle can also be used to write data in parallel be used. So far, using a single laser beam only wrote one bit at a time will. Now you can use several small reflective ones Areas within the area of a laser beam spot and with a corresponding number of small magnetic heads on one Write head multiple bits can be recorded simultaneously.

The principle cannot only be used for thermo-magnetic writing of information used, but also for writing of information by means of other thermal effects if e.g. B. color changes are caused thermally or Phase transitions from e.g. B. amorphous to crystalline and vice versa returns to be used. It is featured in all cases that only by irradiating the laser beam generated temperature increase not quite to cause a significant change in a physical property sufficient, but the temperature increase there is sufficient is high where laser light is additionally of the very small Mirror surface is reflected on the recording medium.

The invention is illustrated below by means of figures illustrated embodiments.

Fig. 1 is a cross sectional view of an optical head according to an embodiment of the invention;

Fig. 2 illustrates the relationship between a diffraction grating and a photodiode;

Figure 3 illustrates changes in light distribution on a photodiode caused by defocusing;

Fig. 4 schematically shows a circuit diagram of a signal recording circuit for the optical head of Fig. 1;

Figs. 5A to 5F are cross-sections illustrating a method of manufacturing the optical's head shown in FIG. 1;

Figure 6 is a cross section through a buried layer surface emitting laser;

Fig. 7 is a cross section through a mesa-type surface emitting laser;

Fig. 8 is a cross section through a photodiode;

FIG. 9A to 9D are cross sections for illustrating a method for simultaneously producing a surface emitting laser and a photodiode;

FIG. 10 is a sectional view of an optical head according to another embodiment of the invention;

Fig. 11 schematically illustrates a circuit diagram of a signal pickup circuit for the optical head of Fig. 10;

Fig. 12 is a sectional view of an optical head according to another embodiment of the invention;

Figs. 13A to 13C are cross sections illustrating a method of manufacturing the optical head of Fig. 12;

Fig. 14 is an explanatory diagram of a solenoid and its magnetic field in the op head shown in Fig. 1;

Fig. 15 is a perspective view of an optical disk apparatus according to an embodiment of the invention;

Fig. 16 is a perspective view of an optical disk apparatus according to another embodiment of the invention;

Fig. 17 is a configuration diagram illustrating the overall arrangement of a Ge optical disk apparatus according to any one of the embodiment of the invention;

FIG. 18A is a bottom view of a magnetic head according to an embodiment of the invention;

FIG. 18B is a cross section through this magnetic head;

Fig. 19 is a cross-section through a magnetic head to another embodiment of the invention;

FIG. 20A illustrates a parallel write operation according to an embodiment of the invention;

FIG. 20B illustrates a parallel read operation of this embodiment;

FIG. 21A to 21E are signals illustrative diagrams for measuring, as are obtained during the read operation;

Fig. 22 schematically illustrates the positional relationship between mirrors in the parallel write process and mirrors in the parallel read process; and

FIG. 23A and 23B are cross-sectional views of showing a parallel-in display / output head according to an embodiment of he invention.

Fig. 1 is a cross section illustrating the structure of an optical head 101 according to an embodiment of the invention.

This optical head 101 has the following structure. Both a surface-emitting laser 1 and photo diodes 7 , 7 are produced via a buffer layer 47 made of AlGaAs on a substrate 2 made of n-GaAs in such a way that both the laser light-emitting surface of the semiconductor laser 1 and the light-receiving surface of the photodiodes 7 , 7 are directed towards the substrate 2 . Opening portions are formed in the laser light emitting surface and the substrates under the light receiving surfaces. Furthermore, the opening portions are filled with a first glass layer 3 , and a diffraction grating 4 is formed on the underside of the first glass layer 3 . A second glass layer 5 is layered on the lower portion of the first glass layer 3 . On the underside of this second glass layer 5 , a condenser lens 6 is formed with a diameter of 1 mm or less, which consists of a grating lens.

The laser light emitted by the surface-emitting laser 1 (shown with a broken line in FIG. 1) runs through the buffer layer 47 , the first glass layer 3 , the diffraction grating 4 and the second glass layer 5 . This laser light is then focused by the condenser lens 6 in such a manner that it is directed just under the condenser lens 6 , and a light spot with a diameter of 0.4 to 2 µm is formed on the recording plane of an optical recording medium R which is generated by the condenser lens 6 is located. The distance between the condenser lens 6 and the recording plane of the optical recording medium R is chosen so that it corresponds to 1 mm or less.

Light reflected from the recording plane of the optical recording medium R (shown by a solid line in FIG. 1) is radiated through the condenser lens 6 and the second glass layer 5 and then diffracted by the diffraction grating 4 in such a manner that the diffracted laser light is applied to the Light receiving planes of the photodiodes 7 , 7 is directed. The diffracted laser light is then radiated through the first glass layer 3 and received by the photodiodes 7 , 7 .

The reason why the buffer layer is formed in the lower section of the laser light receiving surface and the light receiving plane and why the opening sections are formed in the substrate 2 is that the GaAs substrate, the laser light at the laser oscillation wavelength (α = 10 ⁴ cm ^{- 1} ) is strongly absorbed, removed and that the laser is carried by the AlGaAs buffer layer, which absorbs the laser light less (α = 20 cm ^-1 ). Even if AlGaAs is used, since the electrical conductivity does not change, the thickness of this buffer layer is chosen to be thick in order to reduce the electrical resistance without loss of light absorption. Also, the reason why the diameter of the condenser lens 6 is chosen to be 1 mm or smaller is that chromatic aberration as it occurs when the wavelength of the laser light changes due to temperature changes is suppressed to a maximum λ / 4.

This means that the spherical aberration "W" of a hologram is given as follows if it is now assumed that the height from the optical axis on the hologram incident light is "h":

W (h) = Ah ⁴ (1)

(see "Optical Engineering Handbook", edited by T. Kase et al., publisher Asakura, p. 180). It is now assumed that the distance between the hologram and an object point is "Ro", the distance between the hologram and a reference light source for the recording is "Rr", the distance between the hologram and a reference light source for the reproduction " Rc ", the distance between the hologram and a reproduced object point is" Ri ", the wavelength for the recording is" λ "and the wavelength for the reproduction is" λ '", whereupon the following applies:

A = {(λ '/ λ) (Rr ³ - 1 / Ro ³ ) - 1 / Rc ³ - 1 / Ri ³ } (2).

On the other hand, an imaginary relationship is given as follows:

1 / Ri = 1 / Rc + (λ '/ λ) (1 / Ro - 1Rr) (3).

Now assume that Rr → -∞ and Rc → -∞, which gives the spherical aberration as follows:

W (h) = (1 / 8th Ro ³⁾ {(λ '/ λ) ³ - (λ' / λ)} h ⁴ (4).

When a change in the wavelength "Δλ" and the numerical aperture "NA" are defined as follows:

λ '/ λ = (λ + Δ / λ) / λ (5)

(NA) = h / Ro (6),

the spherical aberration can be reproduced as follows:

W / h, NA) = {(NA) ³ Δλ / (4λ)} h (7).

In other words, it can be seen that when the numerical aperture NA is constant, the maximum spherical aberration "W", as caused by a change in the wavelength "Δλ", is directly proportional to the height "h" of the incident light opposite the optical axis on the hologram. For example, the spherical aberration "W" is obtained as follows if the different conditions for NA = 0.55, λ = 0.78 µm and Δλ = 3 nm are given:

W (h = 2.0 mm) = 0.41λ

W (h = 1.0 mm) = 0.21λ

W (h = 0.5 mm) = 0.10λ

As a result, the spherical aberration below λ / 10 can be suppressed if the aperture "2h" of the condenser lens 6 is selected to be 1 mm or less even if the wavelength change is 3 nm.

This can be similarly applied to a case where a convex lens is used as the condenser lens. It is now assumed as an example that a lens is made with a spherical surface. The spherical aberration "W" of the same is given as follows if it is assumed that the refractive index in object space is 1 , the refractive index in image space is n and the focal length is f:

W (h) = {3n / (8 (n - 1) ² f ³ )} h ⁴ (8).

If the numerical aperture "NA" too

NA = nh / f (9)

is selected, the spherical aperture is given as follows:

W (h) = - {3 (NA) ³ / (8 (n - 1) ² n ² } h (10).

As a result, it is possible to use the spherical aberration decrease if the numerical aperture "NA" is constant and the aperture "2h" is made small. This fact can not only on such a spherical aberration, but also applied to other types of spherical aberration the.

Since the reflected light is branched by using the diffraction grating 4 so that the optical path is positioned perpendicular to the optical recording medium R, no problems arise from the fact that the optical path is inclined. Note that if it is assumed that the diffraction efficiency together with that for diffracted light ± first order through the diffraction grating 4 is 50%, 25% of the reflected light is returned to the surface emitting laser. Since no light mode jumping occurs due to the reflected light of the surface emitting laser, there is no disadvantageous influence. The amounts of light received at the photodiodes 7 , 7 can be 25%, ie maximum.

Fig. 2 schematically shows the positional relationship between the diffraction grating 4 and a photo diode 7.

The diffraction grating 4 corresponds to a linear diffraction grating ter, in which both sides of the grating intersect at an inclination angle of 45 ° with respect to center lines which lie on a boundary line, parallel to the recording track direction of the optical recording medium R. There are four photodiodes 7 to receive first-order diffracted light from the diffraction grating 4 . These four photodiodes 7 a, 7 b, 7 c, 7 d are further divided along the subdivision direction of the diffraction grating 4 into two sections.

Fig. 3 illustrates the distribution of reflected light, as it falls on each of the four photodiodes 7 a, 7 b, 7 c and 7 d, under the conditions "further away than the focal point", "just in focus", "closer than the focus ".

Fig. 4 shows an example of a signal detecting circuit in the optical head 101.

A defocus signal AF is obtained in such a way that the output signals of the four photodiodes, which are on the outside of the upper stage in Fig. 4 and which are on the inside of the lower stage there, are summed in an adder 8 a, the output signals of four photodiodes, which are on the inside of the upper stage and the outside of the lower stage, are added up in an adder 8 b and then the output signals of the two adders 8 a and 8 b are processed in a subtractor 9 a.

From the difference between the amounts of light of the laser light falling on the right and left sides of the diffraction grating 4 in Fig. 2, a track shift signal TR is obtained, since this track shift signal TR can obtain what unevenness from uneven light distributions of the light reflected from the optical recording medium R. is caused by track shifts. As a result, the track shift signal TR is obtained in such a way that the outputs of the four photodiodes, which are on the left side of the upper stage in Fig. 4 and on the right th side of the lower stage, are summed in an adder 8 c Output signals of the four photodiodes, which are on the right side of the upper stage and the left side of the lower stage, are summed up in an adder 8 d and then the output signals of these are processed at adder 8 c and 8 d in a subtractor 9 b will.

When an optical disc in which the optical recording medium R is of an overwritable type or a type that can only be read is present, a play signal can be obtained by summing the output signals of all the photodiodes. As a result, it can be generated by summing the output signals of the adders 8 c and 8 d in an adder 8 c.

An example of a method of manufacturing the optical head 101 is illustrated in FIGS. 5A-5F. This manufacturing process for the optical head consists in the following.

According to Fig. 5A, a buffer layer is grown of n-type AlGaAs on the underside of a substrate 2 made of n-GaAs 47, a reinforcing glass substrate 11 is fixed close to the bottom of this buffer layer 47, and an Al electrode 12 is from the gas phase at the The top of the substrate 2 is deposited from n-GaAs.

According to Fig. 5B, both the Al electrode which is used for emitting the laser light 12 can be etched and the substrate 2 made of n-GaAs partially, around a hole 2 b to be used.

Referring to FIG. 5C, the first glass layer 3 on the Al-Elek is trode 12 and the substrate 2 made of n-GaAs by a method such as the plasma CVD method or the sputtering method abge eliminated. Then, the deposited first glass layer 3 is smoothed by a polishing method, or a photopolymer or the like is filled in and hardened so that the etching hole described above is filled.

Referring to FIG. 5D, the diffraction grating 4 is formed on the surface of the first glass layer 3 by an exposure process through a photomask. That is, a photoresist is applied to the top of the first glass layer 3 and dried. Thereafter, this dried photoresist is exposed to a diffraction pattern and developed, and the diffraction grating 4 is manufactured using an ion beam processing method.

According to Fig. 5E, the second glass layer 5 having a refracting index from that of the first glass layer 3 is deposited by, for. B. a plasma CVD method or a sputtering method applied to the first glass layer 3 , and a grating lens 6 is produced by an exposure process with a photomask.

Referring to FIG. 5F, the reinforcing glass substrate 11 is Untitled besei, and the surface-emitting laser 1 and the photodiode 7, 7 are formed on the underside of the buffer layer 47.

Fig. 6 schematically illustrates an example of the structure of a surface emitting laser 1 with an engraving layer.

On the buffer layer 47 made of n-AlGaAs, a layer 14 made of n ⁺ -GaAs, to which a large amount of an n-foreign substance has been added in order to increase the conductivity, is grown. On this layer 14 of n ⁺ GaAs is a reflection Spie gel layer 15 a formed, stacked abwech nately in the n-AlAs and GaAlAs. On this reflection mirror layer 15 , a cladding layer 16 of n-GaAlAs is grown. Furthermore, a quantum well layer 17 is produced from p-GaAlAs / GaAs as an activated layer. Although a sufficiently good characteristic could be obtained by forming the activated layer only from GaAlAs, a low threshold current can be achieved if the quantum well is used. A cladding layer 18 made of p-GaAlAs is grown on the quantum well layer 17 , on which a further reflection mirror layer 15 b is formed. In this reflection mirror layer 15 b, n-AlAs and GaAlAs are alternately stacked on top of one another. On this reflection mirror layer 15 b, a layer 19 of p-GaAs, to which a large amount of p-impurity is added, in order to increase the conductivity, is produced. Finally, an electrode 20 is formed.

Fig. 7 shows an example of the structure of a mesa type surface emitting laser 1 .

After a structure similar to that of FIG. 6 has been made, a cylindrical laser section remains when other sections are etched away. The diameter of the cylindrical mesa section is from 2 to 3 µm, and its height is approximately 5 µm. Since the diameter of the mesa section is small, the radiation angle "Θ" of the laser beam from the laser section is approximately 30 ° to 44 °, that is, it is a large value. As a result, e.g. B. if a condenser lens 6 is used, the focal length of which is 0.1 mm and the numerical aperture NA is 0.55, then if the refractive index of the glass layer is chosen to be 1.5, the distance between the surface emitting laser 1 and the condenser lens 6 is 220 to 320 µm, that is, it can be extremely short, so that the optical head 101 can be compact. Since the surface-emitting laser 1 is of the mesa type and accordingly the confinement effects with regard to the photoelectric field and the initiated current are increased, a lower threshold current can also be achieved.

Fig. 8 schematically shows an example of the structure of the Pho todiode. 7

A layer 14 made of n ⁺ GaAs is grown on the buffer layer 47 made of n-AlGaAs, to which a large amount of an n-foreign substance is added. A layer 21 of GaAs, in which no foreign substance is doped, is grown on this layer 14 of n ⁺ -GaAs. Furthermore, a layer 22 of p-GaAs is partially grown on the GaAs layer 21 . Part of the layer 22 made of p-GaAs is masked to form an insulating layer 23 made of SiO ₂ . This mask is then removed to produce an Au electrode 20 .

Note that although the photodiode 7 is normally manufactured after the surface emitting laser 1 has been manufactured, both the laser and the photodiode can be manufactured at the same time.

By FIGS. 9A-9D, a method for the simultaneous production of both the surface-emitting laser 1 is and det photodiode 7 illustrates.

Referring to FIG. 9A, the buffer layer 47 of n-AlGaAs, a layer 14 of n ⁺ GaAs in which a large amount of a n-type impurity is added to adjust the conductivity to hen raised stabili, grown up. On this layer 14 of n ⁺ -GaAs, a reflection mirror layer 15 a by alternately stacking on each other is of n-AlAs layers and AlAs layers forth provided.

Referring to FIG. 9B, the reflecting mirror layer 15 a only removed where the photodiode is to be formed is 7. In the section from which the reflection mirror layer 15 a was removed, a layer 25 of n-AlGaAs is grown.

Referring to FIG 9C on the reflecting mirror layer 15 a and. The layer 25 formed a cladding layer 16 of n-AlGaAs n-AlGaAs. A quantum well layer 17 made of p-GaAlAs / GaAs is grown as an active layer on the reflection mirror layer 15 a and the layer 25 made of n-AlGaAs. A cladding layer 18 made of p-GaAlAs is formed on this active layer. On this cladding layer 18 , a reflection mirror layer 15 b is grown by alternately stacking n-AlAs layers and GaAlAs layers. By a photo-etching process, only a part of the reflecting mirror layer 15 is removed b, in which the photodiode 7 is to be formed. Then, a layer 22 of p-GaAs is formed in the portion in which the reflection mirror layer 15 b has been removed. On the basis vorste said portion from which the reflecting mirror layer 15 b, a layer 22 of p-GaAs is formed. Further, both layer on the reflection mirror 15 b and on the p-GaAs layer 22 is a layer 19 of p ⁺ -GaAs, that of a p-type impurity has been set to a large amount in order to increase the conductivity is formed.

Referring to FIG 9D is formed on the p ⁺ -GaAs layer 19, a Au-Elec trode 20th. Thereafter, the surface-emitting laser 1 is separated from the photodiode 7 by an etching process.

As described above, when the surface emitting laser and the photodiode 7 are simultaneously manufactured, the entire manufacturing process can be significantly simplified, and accordingly, these components can be manufactured at a low cost.

Fig. 10 is a cross-sectional view of an optical head 102 is according to another embodiment of the invention. The same reference numerals as in the previous embodiment shown in Fig. 1 denote the same function parts in Fig. 10.

This optical head 102 uses a convex lens, the currency rend Kon used in the optical head 101 of FIG. 1 densorlinse 6 is a grating lens. Film-shaped polarizers 28 and 29 are attached to a lower substrate 2 a, which is arranged under the photodiode 7 in the optical head 101 shown in FIG. 1. These polarizers 28 and 29 have directions of polarization for the passage of light, which are perpendicular to each other. It should be noted that when the polarization directions of the polarizers 28 and 29 for continuous light are rotated by ± 45 ° with respect to the polarization direction of the reflected light, the highest measurement sensitivity can be achieved (see the Japanese publication by Ozima and Kakuta under the title "Magneto-Optical Recording Techniques", Optics 1989, Vol. 18, No. 11, p. 599).

Fig. 11 shows an example of a signal detection circuit as used in the optical head 102.

A focus deviation signal AF is obtained in such a way that the output signals of the four photodiodes, which are summed on the outside of the upper stage and the inside of the inner stage, as shown in Fig. 11, in an adder 8 a, the Output signals of the four photodiodes, which are on the inside of the upper stage and the outside of the lower stage, are summed in an adder 8 b and the output signals of these adders 8 a and 8 b are subtracted in a subtractor 9 a. A track shift signal TR is generated in such a manner that the outputs of the four photodiodes, which are on the left side of the upper stage in Fig. 11 and the right side of the lower stage, are summed in an adder 8 c, the outputs of the four Photodiode on the right inside of the upper stage and the left side of the lower stage can be summed in an adder 8 d, and the output signals of these adders 8 c and 8 d can be subtracted in a subtractor 9 b.

In the case of an optical disk in which the optical recording medium R is of the rewritable magneto-optical type, a magneto-optical signal MO can be obtained by making the sum of the output signals of the photodiodes contained in the polarizer 28 from the sum of the outputs signals of the photodiodes in the polarizer 29 is subtracted. As a result, the outputs of the four photodiodes located on the left side of the upper stage and the left side of the lower stage are summed in an adder 8 e, the outputs of the four photodiodes located on the right side of the upper stage and the right side of the lower stage, are summed in an adder 8 f, and the output signals obtained from these adders 8 e and 8 f are subtracted in a subtractor 9 d.

This optical head 102 is also provided with an AF actuator 35 .

The optical recording medium R is an optical disk. Generally speaking, an optical disk has a transparent protective layer 34 with a thickness of 1.2 mm with an information reading side on a recording surface 40 .

For example, if a condenser lens 6 is used in a finite system with a numerical aperture NA = 0.3 on the laser side, the distance between the surface-emitting laser 1 and the condenser lens 6 is approximately 2 mm, and the dimension of the optical one Head 104 is approximately 3mm x 3mm x 3mm.

Fig. 12 is a cross-sectional view of an optical head 106 according to another embodiment of the invention.

This optical head 106 is a floating, shaped as a slide optical head, in which further on the bottom of the optical head, a slide base reinforcement layer 13 is formed of a ceramic metal such as zirconium oxide.

Since the floating slide is integral with the optical Head is made through a film formation process no position adjustment of the optical head for the Sliding floor required.

The extent to which the optical head 106 floats depends on its shape and the linear speed of the optical recording medium R, and the height is about 20 µm or less. Changes in swimming height correspond to approximately 10% of them. Accordingly, the change in the floating height at 20 µm is approximately 2.0 µm. The focal depth of the condenser lens 6 is approximately λ / NA ² . Accordingly, when λ = 0.78 µm and NA = 0.55, the focal depth is approximately 2.6 µm. Since the change in swimming height of 2.0 μm is smaller than the focal depth of the condenser lens 6 , no regulation regarding current focus shifts is necessary. In other words, the change in swimming height can be chosen so that it is smaller than the focal depth of the condenser lens 6 . It should be noted that the optical recording medium 6 does not have to have a transparent protective layer on the information reading side of the recording surface, or that the thickness of the transparent protective layer is smaller than a value calculated by taking the floating height from the rear focal distance of the condenser lens in the medium is subtracted with the refractive index 1.0 and that the subtraction value is multiplied with the refractive index of the protective layer. If either the optical recording medium does not have a transparent protective layer or the thickness of the transparent protective layer is less than 100 µm, there will be a problem in information readings when dust adheres to the surface of this optical recording layer, so that this optical recording medium R is in a dustproof manner Housing must be kept.

It should be noted that when no control for correcting a focus deviation is required, the measuring circuit sections for the focus deviation signal as used in the signal detection circuits of FIGS . 4 and 11 are no longer required, and that the up drawing area of the optical recording medium can be read without focus deviation control.

By FIGS. 13A-13C, a method is illustrated for manufacturing the optical head 106th

Fig. 13A shows the construction state as obtained by the manufacturing process explained with reference to Figs. 5A to 5F.

According to FIG. 13B, that portion of the grating lens 6 is masked by which a zirconium oxide ceramic is deposited by a sputtering process, which leads to a sliding carriage base reinforcement layer 13 . The deposition thickness corresponds to a value as calculated by subtracting a thickness value from the rear focus distance (ie the distance between the lens surface and the focal point in air) of the grating lens 6 which is obtained by both the swimming height and the thickness the protective layer of the optical disk can be divided by the refractive index of the protective layer.

Referring to FIG. 13C, the reinforcing glass substrate 11 is removed ent, umn the surface emitting laser 1 and the photodiode 7, trainees at the bottom of the substrate 2 to 7.

It should be noted that there may be a thin film solenoid 39 on the slide carriage bottom reinforcing layer 13 at the bottom of the optical head 15 which is used to apply a magnetic field.

Fig. 14 is an explanatory diagram for the relationship between the solenoid coil 39 and whose magnetic field.

The magnetic field "H" generated by a circular current "I" with the number of turns "n" and the diameter "a" in the central axis Z is as follows:

H = na ² I / 2√ (a² + z²) ²

For example, a magnetic field H = 100 [Oe] can be produced if it is assumed that n = 5, a = 50 µm, z = 1 µm and I = 160 mA.  

Fig. 15 is a perspective view illustrating an optical disc apparatus 201 according to another embodiment of the invention.

This optical disk device 201 is constructed so that an optical recording medium R having either no transparent protective layer on the information recording side of the recording surface or a transparent protective layer having a thickness less than about 20 µm has a floating optical head 106 previously explained in this embodiment Support arm 46 for holding the floating head 106 and a tracking actuator 31 are built into a dustproof housing 37 and a connection terminal 45 for a voltage supply and a signal is present.

The optical disk device 201 can be made very thin and light, and it can also be formed as a portable cassette because there is no thick transparent protective layer on the optical recording medium R and because there is neither a focus deviation detection circuit nor an actuator for correcting a focus deviation be used. In this case, this optical disk device 201 is used so that it can be detachably connected to an optical disk read / write device 33 .

It should be noted that this optical disk read / write device 33 can be made very compact and inexpensive because the drive mechanism and the signal processing circuit for the optical recording medium R also fit into the optical disk read / write device 33 can be built and since neither an optical head nor a track deviation actuator are required.

Fig. 16 is a perspective view of an optical disk device 202 according to another embodiment of the invention.

One point that differentiates this embodiment from the previous embodiment shown in FIG. 15 is that a tracking actuator 31 is provided on an optical disk reader / writer 330 and is connectable to the support arm 46 of the optical disk device 202 . Since the optical disk device 202 does not include a tracking actuator 31 , this optical disk device 202 can be made compact and inexpensive.

In the optical head according to the invention, the weakening of laser light small, and there is no difficulty visually chromatic aberration when the wel length of the laser light source due to temperature changes changes. There is also no interference signal problem is caused by laser light that leads to the semiconductor laser is returned. Furthermore, there is no problem with that is caused to tilt the optical lens with respect is placed on the optical disc and there will be none Difficulty caused by the SCOOP structure. About that In addition, the entire optical head can be made compact because no floating slide is used, of dimensions that are several times larger than that of the optical head.

A description will now be given of a disk recorder for recording a large amount of information, particularly for a high density optical disk recorder according to an embodiment of the invention for realizing high density information recording of several thousand GB / cm ² up to several TB / cm ^{2 is} suitable.

Conventionally, a magneto-optical disc device like it z. Described in JP-A-52-31703, Infor mation recorded in such a way that laser light on the magneto-optical disk is bundled, whereby an Ab cut locally high temperature is formed, and a magnetized magnetic domain along a particular direction is used in this high temperature section a thermal magnetization reaction.

The limitation on the storage density in this magneto-optical disk is determined by the diameter of the laser spot. Typical spot diameters of recently developed recording devices are in the order of 0.8 µm, and accordingly a larger memory capacity of approximately 600 MB / copy is accessible. In order to further increase the storage capacity, the diameter of the laser light spot must be 0.8 µm or smaller. However, since there is an optical limit, the diameter of the laser spot cannot be reduced infinitely. Currently the limit for the spot diameter is approximately 0.5 µm. As a result, it can be assumed that even if such a writing condition as the intensity profile of the laser spot could be optimized, the limit for the magnetic domain is on the order of 0.3 µm. As a result, there is a problem that, in view of the storage capacity, information storage density greater than about 12 GB / cm ² (2 GB / in ² ) cannot be realized.

On the other hand, it is known that the information storage density of a magnetic disk device is generally lower than that of an optical disk device. This is caused by the fact that the smaller the magnetic domain, the weaker the signal strength, where it is quite difficult to detect the signal with small strength and short length. Therefore, the magnetic domain cannot be divided more than to a limit dimension, so the upper limit for the storage density is approximately 6 GB / cm ² (1 GB / in ² ).

According to the embodiment given below, it is possible to provide a storage device having a large storage density of several 10 GB to several TB / cm ² , although this storage device has the same dimensions as a conventional storage device.

In the storage device of this embodiment, a very small mirror facing the optical disc is in air above the surface of the optical disc floating head and uses an optical system that a laser lighting device and an optical detection device includes. Then laser light from the Rear of the optical plate in that area of the irradiated the same, which contains the area which is with overlaps with the very fine mirror, creating memory information tion read in or out of this optical disk area this is read out.

The effective spot diameter of the laser light can thereby be made small that the width of the very small spie gel smaller than the spot diameter of the optical Plate of radiated laser light is made.

The head can have a magnetic pole for writing informa tion, and a mirror surface of this magnetic pole can be used as the very small mirror.

Several information writing magnetic poles that run along one in the essentially at right angles to the relative direction of movement between the optical disc and the head are arranged, are used within a single head, and several  Individual information is used for the parallel magnet Pole implemented to be inscribed in the optical disc too be while the magnetic polarities of the several Magnetic poles under the condition in accordance with a any series of information are inverted that the common laser light, of which at least part is associated with overlapped all of the several very small mirrors from which Back is blasted onto the optical disc.

The information written in parallel can be from be separated from each other and so recorded that several very fine readout mirrors are available, which are positionally along the relative direction of movement between the optical Plate and the head are moved, and the magnetic poles, which are in the area that is just below that very fine mirror, that of the optical laser is illuminated by the photodetector, while the common laser light, of which at least part overlapped with all very fine mirrors, from the back side is irradiated onto the optical disk. The Auftei This information can be carried out in that the output signals of the photodetectors are used, like they are based on the existing number of magnetic domains be obtained, and also using the change the temporal positions of the output signals.

There are both the very small readout levels as well either the writing magnetic poles or the very small ones Writing magnets used, and the very small readout Gel can be from the magnetic poles or the very small ones Writing mirrors by equal distances with regard to the Center of rotation of the recording medium must be separated.

If either the very small mirror mentioned above or the magnetic poles that act as very small mirrors  through sections of metal films that are laminated on a flat substrate was produced would be built could mirrors with thicknesses on the order of 1/10 nm and magnetic poles with Dic ken of the order of 1/10 nm.

If laser light from the back through the opti plate has penetrated, again through the head existing very small mirror to the optical disc too is thrown back is the intensity of the light in the down cut that is limited to the area just below lies on the mirror and onto which the laser light is also radiated has been raised. As a result, only that magnetic domain can ne, which is in the area in which the light intensity is high, using either the Faraday effect or of the Kerr effect can be detected in that the sens Peculiarities of the photodetectors are detected, so that Infor mation of very small size, which is smaller than the size of the Is laser spot that can be read. In other words, can according to the effective spot diameter of the laser be made very small in that the very small mirror can be shared.

Then, as described above, there is an increase in temperature selectively generated in a local area of one size smaller than the spot size of the laser beam, so that the information is placed in a very small magnetic domain can be written that has a size that is 0.5 microns is equal to or smaller than what is conventional magneto-optical disc could not be realized. The Appearance of the reduction of the coercive force of the magneti film, which is caused by such a local temperature increase hung, can be used to Infor mation using the magnetic poles in very small Enroll magnetic domains.  

Also, multiple writes are made within a single head magnetpole used, and the above we Conversations are compared with those in a single head applied magnetic poles executed in parallel, making parallel information can be written with a single header can. The parallel information can be split up and there by reading that several readout mirror positions moderately along the relative movement direction between the op table plate and the head are moved.

If either the readout mirror or the magnetic domains with Mirror function either separately from the write magnetic poles or the writing mirrors would be arranged, with im substantially the same radius distance from the center of rotation of the Medium, the addressing control for the Informa tion can be carried out easily because the magnet described domains with the reading section and also with the laser beam-illuminated section with higher accuracy inside overlap half of an area where there is no thermal interference medium and head.

Fig. 17 shows the overall arrangement of a recording apparatus for information recording high density te on optical disks according to the invention.

This device is formed by an optical disc 1 , a motor 2 for rotatingly driving the optical disc 1 , a laser light source 3 , a photodetector 4 and a beam splitter 6 . This recorder further consists of a lens 7 , an air floating magnetic head 11 , a head arm 12 , a positioning actuator 13 , a head control circuit 14 , an optical system control circuit 15 , a control system main body 20 , etc. The magnetic head 11 is electrically connected to the Control system main body 20 connected to generate a magnetic field depending on input / output operations, if necessary.

As a laser light source 3 z. B. a semiconductor laser can be used to emit laser light with wavelengths of 780 to 830 nm. A photo multiplier, an avalanche photodiode, an electronically cooled photodiode and the like can be used as the photodetector 4 , which have high sensitivity to low light and also a high S / R ratio.

The optical disc 1 is driven by the engine 2 at a speed of z. B. 3000 rpm. The control system main body 20 has a function that it can address memory information with an algorithm similar to that of a conventional disk memory. A communication line used for input / output of information goes away from the control system main body 20 , and this can be electrically connected to an information processing device.

First, a description will be given of an example of a recording medium of the optical disc 1 in which a magnetic film having an axis of magnetization along the vertical direction with respect to the film surface is used as the recording medium. As a magnetic film, who uses the CoFeNi, barium ferrite, hexagonal ferrite and the like. This magnetic film is applied to the glass substrate with a thickness of 50 nm. Note that since the presence of magnetic domains can be detected by the above optical device even when other vertically magnetizable films are used, the invention can be applied to them.

According to the present invention, in order to realize the light detection in the optical disk, as explained above, the air floating magnetic head 11 and an optical system for irradiating the laser light on the optical disk and for detecting the laser light near the surface of the optical disk are used. Laser light 8 is used to read memory bits by illuminating that area from the back of the optical disk which contains at least that part of the surface of the optical disk which overlaps with the magnetic head 11 . The magnetic head was made by both a conductive pattern from a metal film pattern, e.g. B. made of Au, and a magnetic pole pattern made of a magnetic metal, e.g. B. a Ni-Fe alloy, was made on a hard substrate material such as aluminum oxide titanium carbide. Alumina titanium carbide is machined in a similar process to that of a conventional magnetic head, so that this magnetic head can float in air over the surface of the optical disc (less than about 0.1 µm).

In FIGS. 18A-18B, the magnetic head 108 is enlarged is provided. A very small mirror 30 with a thickness of e.g. B. about 100 nm was made on the surface of the magnetic head 108 on the optical disk side. It should be noted that the thickness of this mirror is not limited to this, but that only a reflecting plane has to be created. The mirror 30 has a rectangular shape with a width of approximately 20 nm and a length of approximately 1 μm. A metal film with high reflectivity such as Al and Cr was used to make the mirror. On this mirror 30 , the laser light 8 was irradiated through a recording medium and a plate-shaped glass substrate 100 from the back of the optical disc R, the plate-shaped glass substrate 100 being used to increase the mechanical strength of the recording medium. At the same time, the photodetector 4 was placed on the rear surface side of the optical disk R so that the light intensity of a portion within a region 81 where the laser light was irradiated was limited to another region 82 which was directly under the mirror 30 lay, could be increased. As a result, only one magnetic domain 121 present in area 82 could be detected using either the Faraday effect or the Kerr effect. The amount of reflection light could be reduced in the region without a mirror 30 . This and by adjusting the measuring sensitivity of the control circuit of the optical system prevented the magnetic domain 122 from being detected incorrectly. Therefore, a very small magnetic domain with a diameter of 1 µm or smaller could be read out according to the size of the laser spot.

Fig. 19 represents a magnetic head according to another embodiment of the invention. In this embodiment, a writing magnetic pole 31 of the magnetic head 108 is provided on the medium surface side, and a mirror surface of this writing magnetic pole 31 is used as a mirror. In order to realize this structure of a magnetic head, a metallic material such as Fe, Ni or Cu was used as the material of the magnetic pole 31 on the surface of the magnetic head 108 . Since this writing magnetic pole 31 is used as a mirror in a manner similar to that in the embodiment shown in FIGS. 18A-18B, the light intensity of that section which lies below this mirror and is also limited to the region 83 into which the laser light 8 is irradiated, increased, and only the magnetic domain 84 present in this area 83 is detected by the photodetector, which is located on the back of the medium R, in a similar manner to the previous exemplary embodiment.

The magnetic domain to be read out as described above was inscribed by reversing the magnetization direction of the magnetic pole 31 used in the magnetic head 108 shown in FIG. 19 using an electrical signal 41 . During this writing process, since there is no difficulty during the reading process (ie with the low detection sensitivity of a conventional magnetic disk), a magnetic head can be used which has a narrow magnetic pole in the track direction. In this case, a magnetic pole approximately 20 nm wide and approximately 1 µm long was used. The dimension of the registered magnetic domain was approximately 20 nm.

Also, even if the phenomenon of the reduction in the coercive force of the medium caused by a local temperature rise caused by the laser light 8 coming from the back of the optical disk is reflected, the metallic magnetic pole 31 a very small magnetic domain is det USAGE as a mirror in Fig. 19, to be written. This is the novel writing principle, which differs from conventional writing processes for magneto-optical and magnetic disks. That is, the local reduction area 83 for the coercive force in the optical disk is generated by the laser beam 8 being radiated thereon. The magnetization strength of the magnetic pole is adjusted, and its polarity is reversed depending on an information sequence, so that magnetic domains that are magnetized in a specific direction can only be generated in such a section that is just below a metallic magnetic pole 31 , the Koerzi tivkraft was reduced and is also limited to the area 83 , in which the laser light 8 is irradiated. No magnetic domain is newly generated in the area whose coercive force is not reduced, even if the magnetic field generated by the magnetic pole 31 is applied to it when this magnetic field is below the coercive force.

Referring again to Figs. 18A-18B, a description will now be given of an example in which a thermo-magnetically writable magnetic film is used as the storage medium of the optical disk R. GdFeCo, TbFeCo, a Pt / Co multilayer film or an alloy film was used as the storage medium. These magnetic films corresponding to the storage medium were formed on the glass substrate 100 . The rest of the device structure is similar to that shown in FIG. 17. The magnetic domains present in the magneto-optical film can be detected by a detector using the Kerr effect described above or the Faraday effect in the optical readout of. Information is captured.

As for a writing operation, a new writing method could be achieved when a magneto-optical film is used as a storage medium. As shown in FIG. 18B, laser light 8 fell from the back of the optical disk toward the back of the air floating head 108 toward the mirror 30 in a similar manner to that in the reading operation. It should be noted that the light intensity of the laser light 8 has been increased to a multiple of that during the reading process. Since the laser light is reflected by the mirror 30 , the temperature rose to approximately 200 ° C., causing a thermo-magnetic phenomenon in the section directly below the mirror 30 and delimited by the area 82 into which the laser light was irradiated. Therefore, magnetic domains with an effect similar to that of a conventional magneto-optical disk could be written in this section. Since the area with temperature increase is limited to such an area into which the laser light falls and into which the laser light reflected by the mirror shines, such an increase in temperature can be generated within a small area which is smaller in size than the laser spot, specifically because by that the mirror is made very small or that the laser light is radiated into a very small section of the mirror. As a result, very small magnetic domains with a size of approximately 0.1 µm could be written. Furthermore, the temperature in the thermo-magnetic film can be locally increased even if the mirror 30 is made of AlTi, AlCu or the like for adjusting the reflectivity, and by increasing the temperature of the mirror itself and by transferring its thermal energy to the closely adjacent one optical disc R.

The laser light 8 shown in Figs. 18A-18B is turned ON / OFF depending on an information stream so that it can be judged whether the temperature changed sequentially over time or not. As a result, according to the existence of very small magnetic domains 123, information could be written with a principle very similar to that of a conventional magneto-optical disk. However, in this writing method, the magnetic directions of the storage medium of the optical disk must match each other before information is written. Since the ON / OFF switching of the laser light can only be done to control whether or not there is a magnetic domain, no information can be written into the optical disk where magnetic domains already exist. In order to overcome this difficulty, the old information must be erased by means of means for heating the optical disk or for applying a strong magnetic field to the same. If such an eraser cannot be used, either a magnetic pole for erasing magnetic domains may be present on the head, or a coil for erasing magnetic domains may be arranged close to the optical disk so that the old information can be erased before new information is registered. When such a magnetic domain erasing coil is used as the auxiliary magnetic pole used in the writing operation, a writing operation can be realized using a magnetic modulation method for the magneto-optical disk. In other words, when the polarity of the auxiliary magnetic pole is reversed depending on the information flow under the condition that the laser light 8 shown in Fig. 18 is in the ON state, magnetic domains are generated depending on the polarities of the auxiliary magnetic pole. According to this method, new information can be written on old information.

With reference again to FIG. 19, a description will now be given of another novel writing method for magnetic domains in the event that a magnetic pole is present on the head 108 . If the metallic magnetic pole 31 is used as a mirror and the laser light 8 radiated from the back of the optical plate is reflected on this mirror, as stated above, a local temperature increase in the area 83 of the optical disk R can occur. Accordingly, this writing method for magnetic domains is realized by using the phenomenon of lowering the coercive force in this area 83 , which is caused by the above-mentioned local temperature rise. Since the coercive force is the main parameter for determining the extent for simple generation of a magnetic domain, the magnetization strength of the magnetic pole is set, and the polarity is also reversed depending on the information flow, so that magnetic domains that correspond to the polarities of the magnetic poles are only in that portion which is located directly below the metallic magnetic pole, being limited to the region 83 , the coercive force of which is reduced by the laser light being radiated into it. Here, even if the magnetic field generated by the magnetic pole is applied to areas whose coercive force is not reduced, no magnetic domain is generated if the strength of this magnetic field is smaller than the coercive force, so that a very small magnetic domain can be written.

With this writing method, magnetic domains can be used in a very small magnetic field of the magnetic pole can be produced, d. H. at its very small current, what a difference represents the case of a conventional magnetic disk. This writing method also exists because of magnetic domains at will along the direction of magnetization of the Ma gnetpols can be written, the feature that a new magnetic domain similar to a conventional one magnetic disk in old information that can.

An embodiment of a parallel writing method will now be explained with reference to FIG. 20A. In this embodiment, a plurality of writing magnetic poles 30 -a to 30 -d are used in a single head 108 along a direction substantially perpendicular to the direction of relative movement between the optical disk and the head, and electrical signals can be input to the respective magnetic poles separately. Then the write operation described above was carried out in a parallel mode for the single write head. More specifically, under the condition that the common laser beam 85 overlapped with at least a portion of all the magnetic poles 30 -a to 30 -d arranged in parallel to one another, the respective magnetization directions of the magnetic poles are reversed depending on any information flow, where by several , individual information to be written into the storage medium was converted into a parallel presence of magnetic domains. There could be a large number of magnetic poles within the spot size of a single laser beam when the common laser beam was irradiated. As a result, information could be written in parallel from a single head, that is, an information writing operation with high density and high speed could be realized.

A description will now be given with reference to FIG. 20B for an example in which the information written in parallel is read out sequentially in time with a single detector. Either a plurality of reading mirrors 43 -a to 43 -d or magnetic poles with mirror functions were shifted in position along the relative movement direction between the optical disk and the head 108 . In this arrangement, the magnetic domains 125 to 128 are on the optical disk at different times on the respective mirrors. Laser light 86 is radiated from the back of the optical disk into an area which contains at least one surface of the optical disk which overlaps with this mirror or the magnetic pole with mirror function. As a result, both magnetic domains 125 , which lie in the section directly below these mirrors or magnetic poles and are limited to the area into which the laser light is irradiated, and magnetic domains 126 to 128 , which are present in other areas, with a single detector at different times who captured the. Using this principle idea, information can be read / written with a single head in a parallel mode.

FIG. 21A-21E represent a situation where the laser light 86 from the rear side of the optical disk forth either on the magnetic poles 43-a through 43-d tion with mirror radio or is irradiated to a plurality of read levels, which positionally optical along the direction of relative movement between the Plate and the magnetic head are moved. A method for time-sequentially reading out parallel information by means of a single detector will now be explained with reference to FIGS . 21A and 21B. Fig. 21A shows the case where four magnetic domains 125 , 126 , 127 , 128 are in parallel form. If there are several reading mirrors that are shifted in position along the relative movement direction, the magnetic domains arrive at different times depending on the movement of the optical disk under the mirrors. As a result, the strength of the detection signal output from the photodetector changes in four steps along the time axis, as shown by a solid curve in Fig. 21C. On the other hand, as shown in Fig. 21B, where there are two magnetic domains 129 and 130 , the strengths of the detection signal change in two stages as shown by a broken line in Fig. 21C. As described above, it can be seen that the amplitude of the detection signal depends on the total number of magnetic domains present.

Since the times at which the presence of a magnetic domain from the mirror 43 -a and the times at which the presence of magnetic domains are detected by the other mirrors 43 -b to 43 -d and the like are constant, the positions at which respective magnetic domains can be are available, are calculated on the basis of the times at which the detection signal changes. This acquisition of the times can, for. B. take place in that the detection signal is differentiated and the differentiated signals are compared ver with each other. Fig. 21D shows a differentiated waveform for the above Fig. 21A, and Fig. 21E represents another differential waveform for the above Fig. 21B. It can be seen from FIGS . 21D and 21E that signals which correspond to the presence of magnetic domains are obtained at different times t1, t2, t3 and t4. The spatially parallel information (presence of a magnetic domain) can be read out by converting it into electrical signals that are separated from one another with respect to the time axis, which is achieved by comparing the amplitudes of the signals with a level represented by a dashed line in one Comparator he follows. As a result, information can be read out with a single head at high speed.

The division of the parallel information as it is given by the gradual changes in signal strengths made that can also be realized in that an additional A / D conversion process of the detection signal executed and then the A / D-converted signal in a digital Circuit is processed. The radio explained above tion, through which multiple flows of information in very small Time periods entered / exited via a single signal head can be given with a conventional magneto- optical disc and a conventional magnetic Plate not running.

It should be noted that since the parallel magnetic domains 125 through 128 are arranged in the direction perpendicular to the relative movement direction of the optical disk with respect to the head 11 in the previous embodiment shown in FIG. 21, the reading mirrors 43-a through 43 -d be moved in terms of position along the relative movement direction in order to separate these magnetic domains on the time axis from one another in order to read them out. Alternatively, if e.g. B. several times entered into several write magnetic poles are slightly shifted against each other, and the parallel magnetic domains are not perpendicular to the above-described relative movement direction, but are formed slightly obliquely here, even if the reading mirror 43 -a to 43 -d is not in position are shifted against each other, the parallel information is read out while it is being separated on the time axis.

Furthermore, to realize the above-described parallel information input / output, a pattern having a mirror function can be made for the head unit 108 , as illustrated in FIG. 22. That is, each of the reading mirrors or the magnetic poles 43 -a to 43 -d with mirror function and each of the reading magnetic poles or the writing mirror 30 -a to 30 -d is arranged so that they are radially apart from each other by a substantially same Distance are clearly spaced from the center of rotation of the medium. As a result, information can be read / written by using a single head and a single laser beam, and an addressing mechanism can be used in common for read / write operations, resulting in a simple addressing mechanism. The addressing control of the information can be easily achieved because the written magnetic domains 127 are overlapped with the reading portion and the portion on which the laser light 87 falls, whereby precision can be achieved within a range in which no medium and no thermal disturbance of the Head.

In order to read and write a very small magnetic domain, either mirrors present on the head 108 or magnetic poles 44 -a to 44 -d with the function of the mirrors have a structure as shown in FIGS . 23A and 23B. Fig. 23A is a cross section showing the input / output head as viewed along the direction in which the head is displaced with respect to the optical disk, and Fig. 23B is a cross section as viewed vertically. The pattern with a mirror function was formed in such a manner after laminating metal films of Fe or Ni that a high polymer resin or silicon oxide with a thickness of 20 nm was formed, and a polyimide resin with a thickness of 20 nm was formed as a spacer and then a photo lithography process was carried out as required. After the pattern was completed, coil patterns 56 , 57 , 58 , 59 required to generate magnetic fields were formed. In this case, such a head structure was produced that the magnetic pole 44 -a speaks the coil pattern 56 , the magnetic pole 44 -b corresponds to the coil pattern 57 , the magnetic pole 44 -c corresponds to the coil pattern 58 and the magnetic pole 44 -d corresponds to the coil pattern 59 . After the head was manufactured with such a step, a part of the head was positioned with its surface close to the optical disk. The relative movement direction between the head and the optical disk was chosen to correspond to the longitudinal direction of the pattern obtained by the required photolithography process after the metal films were laminated.

As stated above, the thickness of the laminate films could be used as the width of the magnetic poles, since the cross section of the metal films used by laminating onto the flat substrate is used as mirrors formed on the head 108 or as magnetic poles 44-a to 44- d with mirror function were manufactured. In this case, the laminate thickness can be set within a wide range from a few 1/10 nm to several µm, and there is no difficulty in reproducibility. Conventionally, there has been a major problem in that the width of the magnetic poles is limited by the resolution of light as used during the photolithography process. In contrast, this limitation has been overcome in the present method. Therefore, a magnetic domain of the order of 1 / nm can be written as long as there are no difficulties with the storage medium. It was confirmed in the experiment that magnetic domains with a size of approximately 0.1 μm or smaller can be written.

In the embodiments described above who a magnetic film for magnetically recording Information or a magneto-optical film like that of thermo-magnetic recording material as memory medium used for the optical disc. The invention is not limited to these materials, but can with regard to the storage medium also on a phase change material such as a chalcogenide glass or a photochromic Material can be applied. That is, even if the se storage materials as a storage medium for optical Plate used to make a change in an area can be witnessed of a size corresponding to the beam spot of the laser beam or a smaller one, namely by sharing very small mirrors, which makes Information can be written with very high density. Information written in this way can can be read by using photodiodes changes in the reflectivity of the storage medium to grasp the z. B. by differences in the phase or Color states are caused. The informa tion magnetically or optically inserted into the optical disc be written.

According to this embodiment, the effective spot diameter of the laser beam can be made very small. As a result, the storage capacity of the optical disk can be increased by approximately 10 ² compared to that of a conventional optical disk. In addition, the mirror functions are provided only in addition to the usual functions of a magnetic disk head, so that such a device for high-density information storage on optical disks can be realized with the substantially conventional structure.

Claims (17)

1. Optical disk device with an optical disk (R) and an optical head ( 106 ) floating thereon, as characterized by
that the swimming height of the head ( 106 ) is at most equal to 10 times the focal length of the condenser lens ( 6 ) of the head, and
that the plate (R) has no protective layer or a transparent protective layer ( 34 ) on its recording surface, the thickness of which is smaller than the difference between the swimming height and the focal length of the condenser lens ( 6 ) multiplied by the refractive index of the protective layer ( 34 ) Medium with the refractive index 1.0. 2. Apparatus according to claim 1, characterized in that the protective layer ( 34 ) has a thickness below 26 microns. 3. Optical disk device with an optical disk (R) and a floating over this head ( 108 ), characterized in
that the head ( 108 ) is provided with a plate (R) facing the mirror ( 30 ), and
that an optical system containing a laser device and a photodetector device is provided, which for reading recorded information radiates laser light ( 8 ) from the rear of the plate (R) into an at least partially overlapped area of the plate (R) by the mirror. 4. Apparatus according to claim 3, characterized in that the width of the mirror ( 30 ) is smaller than the spot diameter of the plate (R) irradiating laser light ( 8 ). 5. Apparatus according to claim 4, characterized in that a magnetic domain ( 121 ) which lies directly under the mirror ( 30 ) in a portion of the plate (R) which is limited to the area irradiated by the laser light ( 8 ), from the near the back of the plate (R) arranged Photodetektorein direction is detected using the Faraday or the Kerr effect. In that the head (108) has a Schreibmagnetpol (31) 6. Apparatus according to claim 3, characterized and the Spie a mirror face on the magnetic pole is gel (30) (31). 7. Apparatus according to claim 3, characterized in that the head (108) has a Schreibmagnetpol (31) and the Ma gnetdomäne (22) by inverting the polarity of the write magnetic pole is written (31). 8. Apparatus according to claim 3, characterized in that in formations in the at least partially overlapped by the mirror ( 30 ) area ( 82 ) of the plate (R) is written, while laser light ( 8 ) from the back of the plate (R) is irradiated in the area. 9. Apparatus according to claim 3, characterized in that the head (108) has a Schreibmagnetpol (31) and the Ma gnetdomäne (30) in a GE directly under the magnetic pole (31) superior and of the laser light (8) irradiated region ( 82 ) the plate (R) is thermo-magnetically inscribed while increasing its temperature. 10. Apparatus according to claim 3, characterized in
that the head ( 108 ) has a magnetic writing pole ( 31 ) which serves as a mirror for reflecting laser light ( 8 ) from the back of the head ( 108 ), and
that the polarity of the magnetic pole ( 31 ) is inverted depending on the information current, whereby magnetic domains accordingly the information "1" and "0" in a directly below the magnetic pole ( 31 ) and from the laser light ( 8 ) be irradiated area of the plate (R) can be written. 11. Apparatus according to claim 3, characterized in
that a plurality of magnetic writing poles ( 30-a ... 30- d) are arranged within a single head ( 108 ) along a direction substantially perpendicular to the relative movement between plate (R) and head ( 108 ), and
that several individual pieces of information are written in parallel in that the polarities of the several magnetic poles ( 30-a ... 30- d) are inverted depending on the information stream. 12. Apparatus according to claim 3, characterized in
that a plurality of magnetic writing poles ( 30-a ... 30- d) are arranged within a single head ( 108 ) along a direction substantially perpendicular to the relative movement between plate (R) and head ( 108 ), and
that several individual pieces of information are written in parallel by the fact that a common laser light ( 86 ) partially overlapping all magnetic poles ( 30-a ... 30- d) is radiated into the plate (R) from the rear and the polarities of the several magnetic poles be inverted according to the information flow. 13. Apparatus according to claim 3, characterized in
that several mirrors ( 43-a ... 43- d) are arranged offset in the direction of the relative movement between plate (R) and head ( 108 ), and
that a plurality of individual items of information which have been written into an area directly below the plurality of mirrors and irradiated by the laser light ( 8 ) are detected by the photodetector device in that common laser light ( 8 ), which at least partially overlaps all mirrors, into the plate ( R) is irradiated from the back. 14. Apparatus according to claim 3, characterized in that the several individual pieces of information based on the output signal of the Photodetektoreinrichtung and the change over time this Output signal can be detected separately. 15. Apparatus according to claim 3, characterized in that the head ( 108 ) is provided with a reading mirror ( 43 ) and a writing magnetic pole ( 31 ) or a writing mirror ( 30 ), and in that the reading mirror ( 43 ) and the writing magnetic pole ( 31 ) or writing mirror ( 30 ) around the pivot point of the plate (R) ra dialen distance from each other. 16. Apparatus according to claim 3, characterized in that the mirror ( 30 ) or the magnetic pole ( 31 ) serving as a mirror is formed by a cut surface of a metal film laminated to a flat substrate. 17. Apparatus according to claim 1 or 3, characterized in that the head ( 106 ) has a magnetic coil ( 39 ) which is arranged on the side of the optical plate (R) irradiated by the laser light.