JPS63102053A - Magneto-optical head - Google Patents

Abstract

PURPOSE:To realize overwrite and to accelerate the speed of an information transfer by reflecting and diffracting light coming from a fine lens disposed at the tip of a semiconductor laser and detecting an address signal and a sector servo signal from the sum signal of both photodetectors for the light and a photomagnetic signal from the difference signal of the both photodetectors. CONSTITUTION:The light 37 which comes from the fine lens disposed at the tip of the semiconductor laser is reflected and diffracted by an information track 38 on a photomagnetic recording medium 5. Respective terminals 52-1 and 52-2 detect photoelectric currents that the both photodetectors 35-1 and 35-2 of the reflected and diffracted light 39 output. The address signal and the sector servo signal are detected from the sum signal 54 obtained by summing the both outputs, and the photomagnetic signal (data signal) from the difference signal 55 obtained by subtracting the outputs. A Luneburg lens being the lens 31 is made as follows: dielectric materials whose refraction factor index is higher than that of a guide wave layer 44 are laminated on buffer layer 43 and the guide wave layer 44 stuck to the semiconductor laser substrate 36, and all of them are shaped with the periphery circular and the surface semi-circular. Thus the overwrite can be attained and a magneto-optical head can be obtained which can transfer information at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Description of the field to which the invention pertains The present invention relates to a miniature magneto-optical head of the type that flies close to a magneto-optical recording medium.

(2) Conventional technology Figure 8 shows an example of the optical system of a conventional magneto-optical head (Ishii et al., "Optical head for magneto-optical disks", Journal of the Japan Society of Applied Magnetics, "p" p-351, 1984). ).This optical head operates as follows.

The light emitted from the semiconductor laser 1 is transmitted through a coupling lens 2,
The light passes through the half mirror 3 and is focused and irradiated onto the magneto-optical recording medium 5 by the objective lens 4. An external magnetic field 7 is applied to the magneto-optical recording medium 5 by a magnetic field generator 6 . Recording is performed by utilizing a decrease in the coercive force of the magneto-optical recording medium 5 due to a local temperature rise in the semiconductor laser irradiated area, and by causing local magnetization reversal by an external magnetic field 7.

The rotation of the plane of polarization is used for reproduction. The reflected light from the magneto-optical recording medium 5 is reflected by the half mirror 3, transmitted through the 1/2 wavelength plate 8, partially reflected by the polarizing beam splitter 9, and transmitted to the photodetector 10, where it is optically detected. It reaches vessel 11. In order to reduce the effects of reflectance fluctuations of the magneto-optical recording medium and output fluctuations of the semiconductor laser, a magneto-optical signal (data signal) 12 is detected from the difference signal of the rain detectors 10 and 11. Further, an address signal and a sector servo signal 13 are obtained from the sum signal. In addition, 14, 15, 16 are astigmatism optical systems and the photodetector 10.
A focus error signal 17 is obtained.

Track error signal 18 is obtained from photodetector 11.

``Magneto-optical heads with this conventional structure have the drawbacks of having a large number of parts, complicated assembly and adjustment, and difficulty in reducing size and cost.

Further, in the magneto-optical head of the conventional structure, the distance between the objective lens 3 and the recording layer 19 of the magneto-optical recording medium 5 is about 2.5 m, and the thickness of the magneto-optical recording medium 5 is 1.2 m. Therefore, the magnetic field generating section 6 is separated from the recording layer 19 by several orders of magnitude, whether on the front side or the back side of the magneto-optical recording medium. Therefore, in order to generate the magnetic field (approximately 5000 e) necessary for recording and erasing, the magnetic field generating section 6 must be large in size, and high-speed magnetic field reversal is not possible due to the inductance of the electromagnetic coil. For the above reasons, the conventional magneto-optical head has the disadvantage that the information erasing operation requires rotational waiting time, cannot be overridden, and has a low information transfer speed.

Furthermore, due to the heat generated by the large electromagnetic coil, the temperature inside the device increases, resulting in a decrease in various margins, making recording/reproducing/erasing operations unstable and reducing the reliability of information.

(3) Purpose of the Invention The purpose of the present invention is to solve these problems by disposing a minute magneto-optical head on the surface of a slider that flies close to the optical recording medium, enabling override and high information transfer speed. The objective is to provide a low-cost magneto-optical head.

(4) Structure of the invention (4-1) Differences between features of the invention and conventional technology (means for solving problems) As shown in FIG. It is arranged on the edge 23 or the side surface 24. This slider 22 and gimbal spring 25. It is used by being attached to a positioner (not shown) that can move at high speed in the radial direction of the magneto-optical recording medium 5 via the arm 26.

(4-2) Example (Example 1) FIG. 2 is a configuration diagram of an optical head that best represents the features of the present invention. The dimensions are extremely small, for example, a height of 0.7 mm, a width of 0.5 mm, and a thickness of 0.1 mm.

A semiconductor laser 32 with a microlens 31 disposed at its tip, and an optical polarizing element 34-1, 34-2 and a photodetector 135 via insulating grooves 33-1, 33-2 on both sides of the semiconductor laser, respectively.
-1 and 35-2 are arranged on a semiconductor laser substrate 36. The microlens 31
The emitted light 37 is reflected and diffracted by the information track 38 on the magneto-optical recording medium S, and the reflected and diffracted light 39 is transmitted to both photodetectors 3.
The output of the photocurrent from 5-1.35-2 is detected at each terminal 52-1.52-2, and the sum signal 54 is used to generate an address signal and sector servo signal, and the difference signal 55 is used to generate a magneto-optical signal (data signal). To detect.

Note that current is injected into the semiconductor laser 32 from the terminal 51. 53 is a semiconductor laser 32 and a photodetector 35-1
, 35-2. 40 is an electrode stripe for confining and injecting current into the semiconductor laser; 41
is an active layer, 42 is an etched mirror surface of the semiconductor laser 32 formed by microfabrication technology, and optical width optical elements 34-1,
It touches 34-2. The microlens 31 of this embodiment is a so-called Luneburg lens. This Luneburg lens is a buffer layer 43 (for example, 5IO) on the semiconductor laser substrate 36.
2) A dielectric material having a higher refractive index than the waveguide layer 44 (for example, Si) is placed on the waveguide layer 44 (for example, glass 7059).
N) are laminated, and the circumference is circular and the surface is shaped into a semicircle.

Regarding the shape and manufacturing method of such Luneburg lenses, see, for example, Yao et al.
aveoptical thin-film Lu
neburg lenses fabrication
nteehin 1que and prope
rties, APPLIED 0PTICS.

vol, 18. No, 24. p, 4087.
1979.

The Lunebourg lens has a light-converging effect in a trundle-dimensional manner only for light parallel to the plane of the waveguide layer 440 (parallel to the active layer 41). FIG. 3 is an example of measuring the spot diameter of light emitted from a semiconductor laser. It can be seen from the figure that in the case of an optical head of medium-close flying type, the spot diameter in the direction perpendicular to the active layer is within 1 μm when the flying height is within 3 μm. This B indicates that there is no need for lens action in the linear recording density direction in the case of optical recording. On the other hand, the active layer 41
The spot diameter is large in the direction parallel to . This indicates that a lens action is necessary in the track density direction. Therefore, the light beam is focused in a direction parallel to the active layer 41 by the Luneburg lens.

Further, the optical width optical element 34-1, 34-2 can be a laminated thin film element made of alternating multilayer films of dielectric and metal as shown in FIG. Only light having a polarization plane in a specific direction is defined as transmitted light 61.

For example, the characteristics and manufacturing method of this optical width optical element are as follows.
5iraishi et al Microisola
tor, APPLIKDOPTICS, vol.
25. No, 2. p. 311.1986.

Here, the dielectric layer 62 is made of SiO2 and has a thickness of 0.8 μm.
The metal layer 63 is formed by laminating about 100 layers of A1 with a thickness of 0.005 μm. This element has low loss, high extinction ratio, and is extremely small, so it can be used as a polarizing element for a small magneto-optical head.

(Embodiment 2) FIG. 5 is a configuration diagram of an optical head according to a second embodiment of the present invention. An insulating groove 33-3 is formed at the rear end of the semiconductor laser 32 using the same microfabrication technique as in the first embodiment, such as reactive ion beam etching. The groove width is several μm, and the depth is several μm, passing through the active layer 41 and reaching the semiconductor laser substrate 36. As a result, a photodetector 35-3 is formed at a position facing the rear output end face of the semiconductor laser.

In the signal detection of the first embodiment, a part of the reflected diffraction light 39 passes through the microlens 31 and then returns to the front output end face of the semiconductor laser 32, which may cause the output of the semiconductor laser to fluctuate.

The second embodiment is aimed at preventing deterioration in the quality of the address signal, sector servo signal 54, and magneto-optical signal (data signal) 550 due to this output fluctuation, and operates as if it were under a breath.

First, the output cuff 3 of the semiconductor laser is received by the photodetector N35-3 at the rear end of the semiconductor laser, and its photocurrent is detected through the terminal 71 and the low-pass filter 72. The low-pass filter is used to smooth the high-frequency composite resonance signal in the data signal band due to address information and sector servo information. The address signal and sector servo signal 54 are sent to the divider 7
4 by the output cuff 3 of the semiconductor laser, resulting in an address signal and sector servo signal 76 with no output fluctuation. Similarly, the magneto-optical signal (data signal) 55 is divided by the output cuff 3 of the semiconductor laser by a divider 75, resulting in a magneto-optical signal (data signal) 77 with no output fluctuation.

FIG. 6 is a diagram showing the mounting state of a magneto-optical head according to a third embodiment of the present invention. The magneto-optical head 21 is pushed into the gap of a magnetic circuit 27 integrated with the slider 22. In this example, the magneto-optical head 21 is disposed on the rear edge 23 of the slider 22, but it may be disposed on the side surface 24.

A part of the slider 22 is made of magnetic material and constitutes a common magnetic circuit. 28 is an excitation coil wound around the magnetic circuit 27. An excitation coil is driven to generate an external magnetic field in the gap portion of the magnetic circuit, which is used as a recording or erasing magnetic field.

FIG. 7 shows calculated values in which the perpendicular magnetic field Hy to the magneto-optical recording medium 5 is normalized by the gap center magnetic field HO. Gap length g
= 100 μm 1 If flying height y = 5 μm, gap center x
Hy/Ho at /g=0.5 is y7g=o, o in the same figure.
Since this corresponds to the case of 5, the value is close to 1.0.

That is, it can be seen that Hy has a value comparable to the gap center magnetic field Ho and is sufficiently large. In other words, with this magnetic circuit configuration, the external magnetic field 7 (Fig. 8) is sufficient for recording and erasing information on the magneto-optical recording medium.
can be easily obtained.

Control operations when recording, reproducing, and erasing information on a magneto-optical recording medium using the magneto-optical heads of the first, second, and third embodiments described above are performed as follows. . first.

As mentioned above, the focus servo utilizes the automatic floating of the slider by airflow. Further, a tracking error signal can be detected using the method described below, and track servo can be performed using an actuator (not shown) in the same manner as in the conventional method.

(1) Sector servo method: A method of detecting servo patterns recorded discretely on an information track in advance. (2) Buried servo method: Servo patterns continuously recorded on another layer on the same track as the data signal. (5) Detailed description of the invention As described above, the magneto-optical head according to the present invention is constructed by disposing a semiconductor laser, a photodetector, a microlens, and an optical photometric element on the same substrate of the semiconductor laser. (1) An ultra-compact, highly reliable magneto-optical head that is easy to assemble and adjust can be realized.

(2) In detecting magneto-optical signals by the differential method, a difference signal of track diffracted light is used, so a prism for space division is not required.

Furthermore, the magneto-optical head according to the present invention is used by being inserted into the gap of a magnetic circuit created on the surface of a slider that flies close to the magneto-optical recording medium, and the magnetic field generating part is much smaller than that of conventional magneto-optical heads. Therefore, (3) high-speed magnetization reversal, that is, override is possible,
A magneto-optical head with high information transfer speed that does not require rotational waiting time can be realized.

It has the following advantages.

[Brief explanation of the drawing]

FIG. 1 is a usage state diagram of the magneto-optical head of the present invention, FIG. 2 is a first embodiment of the invention, and is a configuration diagram of the magneto-optical head that best represents the features of the present invention, and FIG. 3 is a semiconductor A graph showing an example of measuring the spot diameter of laser emitted light, FIG. 4 is a block diagram of a photometric element, FIG. 5 is a block diagram of a magneto-optical head showing a second embodiment of the present invention, and FIG. A diagram showing how the magneto-optical head is installed in the gap between the slide and the integrated magnetic circuit in the third embodiment of the invention, FIG. 7 is a graph showing the perpendicular magnetic field strength near the magneto-optical head, and FIG. FIG. 3 is a diagram showing an optical system of a magnetic head. In the figure, 5 is a magneto-optical recording medium, 27 is a magnetic circuit, 31 is a microlens, 32 is a semiconductor laser, 33-1, 33-2.33-3 is an insulating groove, 34-1.3
4-2 is a photometric element, 35-1, 35-2, 35-3 are photodetectors, 36 is a semiconductor laser substrate, 37 is an emitted light, 38 is an information track, 39 is a reflected diffraction light, 54 is a sum 55 is a difference signal, 72 is a low-pass filter, and 73 is an output signal of a semiconductor laser.

Claims (4)

[Claims] (1) A semiconductor laser with a microlens at its tip, and an optical polarizing element on both sides of the semiconductor laser through insulating grooves, respectively.
It is constructed by disposing two sets of light receiving sections consisting of photodetectors on a semiconductor substrate, and the light emitted from the microlens is reflected and diffracted by the information track on the magneto-optical recording medium, and both of the reflected and diffracted lights are separated. A magneto-optical head characterized in that an address signal and a sector servo signal are detected from a sum signal of a detector, and a magneto-optical signal (data signal) is detected from a difference signal. (2) A semiconductor laser with a microlens at its tip, and an optical polarizing element on both sides of the semiconductor laser through insulating grooves, respectively.
Two sets of light-receiving sections each consisting of a photodetector are arranged at the rear end of the semiconductor laser, and the light emitted from the microlens is reflected and diffracted by the information track on the magneto-optical recording medium. and obtains an optical output signal of the semiconductor laser by the feedback light of the reflected and diffracted light to the semiconductor laser by a photodetector at the rear end;
The optical output signal of the semiconductor laser after passing through a low-pass filter is divided by the difference signal of the photodetectors on both sides of the semiconductor laser to obtain a magneto-optical signal (data signal), and the sum signal is divided to produce an address signal and a sector servo signal. A magneto-optical head characterized by: (3) A magneto-optical head according to claim 1, wherein the magneto-optical head is disposed in a gap of a magnetic circuit integrated with a slider that flies close to a traveling magneto-optical recording medium. (4) A magneto-optical head according to claim 2, wherein the magneto-optical head is disposed in a gap of a magnetic circuit integrated with a slider that flies close to a traveling magneto-optical recording medium.