JP3477214B2 - Optical unit for magneto-optical - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical unit.

[0002]

2. Description of the Related Art As a magneto-optical pickup device, various proposals have been made for technologies aiming at reduction in size and weight.

For example, Japanese Patent Laid-Open No. 4-74333 (Reference 1)
Discloses a device having the following configuration. As shown in FIG. 2 of the publication, the device has a beam splitter for separating the reflected light from the magneto-optical recording medium and the emitted light from the semiconductor laser inside the cap, which is located above the semiconductor laser. It is installed at a position where the emitted light is emitted as divergent light. The reflected light from the magneto-optical recording medium, which is reflected by the beam splitter and separated from the light emitted from the semiconductor laser, further passes through the half-wave plate and is incident on the polarization beam splitter to be split into two polarization components. . The light transmitted through the polarization beam splitter is directly received, the reflected light is further reflected by the total reflection surface, and then received by the photodetector.

The photodetector is installed on the table so as to be in front of the converging position of the transmitted light of the polarization beam splitter and behind the converging position of the reflected light. The beam splitter and half-wave plate are bonded together and the polarizing beam splitter is bonded onto the photodetector. The semiconductor laser and the photodetector are mounted on the same stem via the respective stands, and are hermetically sealed with a cap together with the beam splitter, the half-wave plate, and the polarization beam splitter.

The technique disclosed in Japanese Patent Laid-Open No. 4-38628 (Reference 2) is also known. This one discloses the use of a uniaxial birefringent plate as an optical member for magneto-optical detection in an attempt to realize a simple device configuration while solving difficulties such as assembly accuracy when using a large number of optical systems. To do.

That is, in the device, photodetectors for ordinary light and extraordinary light are arranged on a semiconductor substrate, and a uniaxial birefringent plate wafer having a required thickness is bonded thereon by an adhesive, and A half mirror film is formed on the upper surface. The semiconductor laser is arranged facing the window portion of the submount laminated on the uniaxial birefringent plate,
Laser light is emitted obliquely from above the half mirror film, reflected by the half mirror film, and irradiated onto the magneto-optical recording medium.

The return light from the magneto-optical recording medium is transmitted through the half mirror film and is separated into ordinary light and extraordinary light by a uniaxial birefringent plate, and a photodetector for ordinary light and extraordinary light (photo It is received by the detector). This allows
It is used for detection of focus and tracking control signals, and an information signal can be detected by a difference signal.

In this device, by adopting the above-mentioned structure, an integrated pickup device as shown in FIG. 2 of the same publication (reference 2), that is, a semiconductor for distributing return light to two detecting portions, is used. We are trying to solve the drawbacks of forming a thin film (half mirror) for adjusting the reflectance on the substrate and forming a total reflection film on the upper surface of a prism (trapezoidal prism) to be bonded onto it.

In Japanese Laid-Open Patent Publication No. 64-46243 (Reference 3), a detection prism (39) and a pair of photodetectors are provided on a semiconductor substrate on which a semiconductor laser is arranged, as shown in FIG. 1 of the publication. (3
5,36) The position of the hologram element is arranged on the back surface of the transparent substrate (glass plate).

Further, Japanese Patent Laid-Open No. 3-212828 (Reference 4) discloses
The following structure is disclosed. A semiconductor laser that emits laser light parallel to the bottom surface of the package is placed on a submount (heat sink) having a predetermined height. On the other hand, a trapezoid formed by forming a birefringent trapezoidal prism on a semiconductor substrate on which a photodetector is arranged and forming a half mirror film on the upper surface of the prism, or by using a non-birefringent material such as optical glass or transparent plastic. A prism is used and a flat plate having birefringence is provided on the upper surface of the prism, and a half mirror film is formed on the flat plate, and the half mirror film is opposed to the semiconductor laser on the submount at a predetermined angle. , 7
(Figure).

[0011]

[Problems to be Solved by the Invention] JP-A-4-74333
According to (Reference 1), everything except the objective lens is hermetically sealed by a cap, and the polarization beam splitter, photodetector, and semiconductor laser are arranged on the upper part of the stem, but they are bonded to the beam splitter and polarization prism. 1/2
The configuration uses a wave plate, and the half wave plate and the polarizing prism with a multilayer coating increase the manufacturing cost.
Moreover, they are expensive optical components.

The one disclosed in JP-A-4-38628 (reference 2) is
Although the uniaxial birefringent plate is used, the uniaxial birefringent plate wafer is simply bonded on the photodetector arranged on the semiconductor substrate with an adhesive from above, and the half The structure is such that the semiconductor laser mounted on the submount faces the mirror film from diagonally above, and no special means for positioning the uniaxial birefringent plate is taken. Also requires man-hours.

Japanese Unexamined Patent Publication No. 64-46243 (Reference 3) discloses a structure in which a horizontally long trapezoidal prism is adhered on each photodetector on a semiconductor substrate. There is no special means for positioning and there is no need for positioning, and on the semiconductor substrate, a thin film for reflectance adjustment that allows 1/2 transmission and 1/2 reflection of light is formed, or a trapezoidal prism is used. It is also necessary to form a total reflection film on the top surface, and in addition, in order to actually extract the magneto-optical signal, 1 /
A two-wave plate or a beam splitter that separates light is required, and the number of man-hours required for manufacturing is high and the cost is high.

Further, in the combination of Japanese Patent Laid-Open No. 64-46243 (Reference 3) and Japanese Patent Laid-Open No. 3-212828 (Reference 4), a structure using a mount is used, and the birefringence is different from that on the semiconductor laser side. The optical axis of the submount and the birefringent optical member are adjusted by aligning them with the side of the birefringent optical member so that the laser beam is emitted from the semiconductor laser on the submount to the inclined half mirror film. Required.
For example, as shown in FIG. 7 (a) of JP-A-3-212828, a flat plate having birefringence is provided between a trapezoidal prism made of a material having no birefringence such as optical glass or transparent plastic and a half mirror film. In this case, the position of the reflection surface is high because the optical member with the reflection surface is bonded on the semiconductor substrate via the trapezoidal prism, and the upper surface of the heat sink (submount) is required on the semiconductor laser side. This is a structure in which the position of the semiconductor substrate on which the photodetector and the photodetector are arranged needs to be adjusted, and therefore, the number of assembling steps is also increased.

The present invention has been made in view of the above points, and is easy to manufacture and can be constructed at a low cost, and the assembly such as position adjustment is easy and the optical unit for magneto-optical can be miniaturized. It is intended to provide.

[0016]

SUMMARY OF THE INVENTION The present invention is a semiconductor substrate.
A semiconductor laser and an analyzer arranged in the
A first photodetector and a second photodetector formed on a substrate;
Provided on the body substrate, the semiconductor laser has a predetermined angle
Away from the semiconductor substrate
Installed on the transparent substrate combined with the package
Beam splitter, and the semiconductor laser
The light beam emitted from the
Guide to the magnetic recording medium and return from the magneto-optical recording medium
Light through a different optical path from the light beam from the reflecting surface.
The analyzer and the first and second photodetectors.
A magneto-optical optical unit, comprising:
The analyzer is made of a different optical material, and
It is characterized in that it is joined at the back surface of the shooting surface portion. Well
Also, the optical material of the reflective surface of the reflective surface portion is glass or semi-finished.
It consists of a conductor substrate, and the optical material of the analyzer is not a crystal.
It is characterized by Further, the analyzer is the beam
On the surface where the return light deflected by the splitter is incident, the polarization
It is characterized in that a program is formed.

[0017]

According to the present invention, the semiconductor laser having the above-described structure is not mounted on the submount on the semiconductor substrate, and the hologram element having the beam splitter function is formed on the surface (collimator lens side) of the transparent substrate for positioning. The above-mentioned effect is remarkable because the size is simple and easy to assemble, the miniaturization can be realized, and the reflecting surface portion can be effectively used to join the optical member for magneto-optical detection to the back surface by the reflecting surface portion. Furthermore, there is no need to use optical components such as a polarizing prism coated with a multilayer film and a half-wave plate, and it is possible to make the structure easy and inexpensive.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the configuration of a magneto-optical pickup device according to an embodiment (first embodiment) of the present invention. In the figure, reference numeral 1 denotes a semiconductor substrate, a semiconductor laser 2 is arranged on the surface of the semiconductor substrate 1, and a photodetector 3 is formed and arranged on the surface of the semiconductor substrate 1. The photodetector 3 comprises a first photodetector 3a and a second photodetector 3b.

The semiconductor substrate 1 also has a reflecting surface portion 4 facing the semiconductor laser 2 at a predetermined angle on the semiconductor substrate 1 and behind the reflecting surface portion 4 (a semiconductor facing the reflecting surface 4a of the reflecting surface portion 4). At a position on the light receiving surface of the photodetector 3 at a position (opposite to the laser 2), the uniaxial crystal plate 5 is bonded to the reflecting surface portion 4 on the semiconductor substrate 1 by back bonding as shown in the figure. There is.

In this embodiment, the reflecting surface portion 4 is formed of the semiconductor substrate itself (for example, a Si wafer), and the reflecting surface 4a having a predetermined angle and the bonding back surface of the uniaxial crystal plate 5 are formed by etching. And the vertical surface 4b which becomes
The reflecting surface 4a is coated with a multilayer film.

The uniaxial crystal plate 5 which is separate from the reflecting surface portion 4 in the semiconductor substrate has an upper surface 5a which serves as an optical path surface for returning light from a magneto-optical recording medium, which will be described later, and a photodetector 3 which receives light. Lower surface 5b placed on the surface and side surfaces orthogonal to these upper and lower surfaces
5c and 5d are prepared by preparing from a material such as TiO ₂ (rutile), and at the right angle part of the back surface (vertical surface) 4b of the reflection surface part 4 and the lower surface 5b of the crystal plate 5 and in the figure. The surfaces 4b and 5c of the semiconductor substrate 1 are bonded to each other with an adhesive 6 so that the right-angled corners of the left side surface 5c are aligned with each other using the reflection surface portion itself of the semiconductor substrate 1 as a positioning reference.
The details of bonding the back surface of the reflecting surface portion 4 and the surface of the semiconductor substrate will be described later.

The semiconductor laser 2, the uniaxial crystal plate 5, and the reflecting surface portion 4 (in this example, a part of the semiconductor substrate itself) are all formed on the same surface of the semiconductor substrate 1 as shown in the figure. The uniaxial crystal plate 5 is located as close to the semiconductor laser 2 as possible due to the above-described rear surface bonding to the reflecting surface portion 4.

On the surface of the semiconductor substrate 1, a photodetector 7 for monitoring is arranged so as to face the rear surface of the semiconductor laser 2. The photodetector 7 for monitor is the semiconductor laser 2
The semiconductor laser 2 receives the light beam emitted from the rear surface of
The semiconductor laser 2, the reflecting surface portion 4 facing the semiconductor laser 2, and the uniaxial crystal plate 5 back-bonded behind the semiconductor laser 2 are compactly arranged on the semiconductor substrate 1 even if they are included. The width of the semiconductor substrate 1 itself used (the size in the left-right direction in the figure) is also small,
Such a component is mounted on the bottom of the package 8.

On the other hand, the glass substrate 9 is provided on the upper surface of the package.
And a beam splitter formed by the hologram element 10 is provided on the surface of the glass substrate. This is located above the reflective surface portion 4 in the semiconductor substrate. Semiconductor laser 2 on semiconductor substrate 1, uniaxial crystal plate
5 and the like are hermetically sealed by the package 8. With these components, a magneto-optical unit can be constructed.

Outside the package 8, a collimator lens 12 and an objective lens 13 are provided in the optical path between the hologram element 10 and the magneto-optical recording medium 11 on the glass substrate 9, and the reflecting surface portion 4 emitted from the semiconductor laser 2 is provided. The more reflected light beam passes through the hologram element 10 and is sequentially collimated by a collimator lens.
12, the objective lens 13 is guided so as to be focused on the magneto-optical recording medium 11, and the return light reflected by the magneto-optical recording medium 11 is sequentially transferred to the objective lens 13,
When passing through the collimator lens 12 and the hologram element 10, the light is deflected at a predetermined diffraction angle and is incident on the uniaxial crystal plate 5 back-bonded to the reflecting surface section 4. A magneto-optical pickup device can be configured by including these collimator lenses and the like.

Next, the signal reading from the magneto-optical recording medium by the apparatus of this embodiment will be described. In FIG.
A light beam emitted from the semiconductor laser 2 disposed on the semiconductor substrate 1 along the surface of the semiconductor substrate (horizontally) is reflected by the total reflection surface 4a of the reflection surface portion 4 built in by the semiconductor substrate 1, and the reflection is performed. It goes toward the hologram element 10 on the surface of the glass substrate 9 arranged at a position apart from the semiconductor substrate 1 at the upper portion of the surface portion 4.

The uniaxial crystal plate 5 back-bonded to the reflecting surface portion 4 is manufactured in a shape as shown in the figure, but the incident light from the reflecting surface portion 4 to the hologram element 10 is the uniaxial crystal plate. It is set so that it does not hit the upper part of 5. The light transmitted through the hologram element 10 and emitted to the outside of the package 8 becomes parallel light by the collimator lens 12, is condensed by the objective lens 13, and is focused on the magneto-optical recording medium 11.

The light reflected on the magneto-optical recording medium 11 passes through the objective lens 13 and the collimator lens 12, is focused again, and is deflected by the hologram element 10 at a predetermined angle as shown in the drawing to be focused inside the package 8. Incident on. In this way, the return light from the magneto-optical recording medium 11 is reflected
Incident on the uniaxial crystal plate 5 as an optical member for magneto-optical detection through an optical path different from that of the light beam from, but the diffraction angle at the hologram element 10 in this case is uniaxially bonded to the reflecting surface section 4 at the back surface. The size is small according to the position of the crystal plate 5 on the semiconductor substrate 1.

When the deflected light is incident on the uniaxial crystal plate 5, it is separated into ordinary light and extraordinary light due to the difference in refractive index between ordinary light and extraordinary light, and the light receiving surface of the photodetector 3 is shown in the figure. And is received by the first photodetector 3a and the second photodetector 3b, respectively. The return light from the magneto-optical recording medium 11 has its polarization direction rotated by Kerr rotation according to the magnetization direction of the irradiation position of the light beam, and thus has a Kerr rotation component. Then, when returning to the above-mentioned return optical system, the return light incident on the uniaxial crystal plate 5 is decomposed into light amounts determined by the extraordinary light and the ordinary light with respect to the crystal optical axis direction, and changes depending on the Kerr rotation angle. Therefore, the information signal on the magneto-optical recording medium 11 can be read by the differential signal of the amount of light received by the first and second photodetectors 3a and 3b.

According to this embodiment, it is possible to detect a signal as described above, and in extracting a magneto-optical signal, a polarizer such as a polarizing prism coated with a multilayer film and a 1/2 wavelength plate is used as an analyzer. It is possible to realize a miniaturized magneto-optical pickup device which is easy to manufacture and does not require the use of expensive optical parts and has an inexpensive structure.

FIG. 4 is a diagram for explaining the principle for realizing miniaturization and the like according to the present invention. In the figure, the semiconductor laser LD directly installed on the silicon substrate (semiconductor substrate) is shown as an example in which the light emitting surface (active layer) is arranged on the lower side. The reflection surface portion facing the front surface of the semiconductor laser is formed by etching a part of the silicon substrate, and the reflected light is reflected to the extent that it does not hit the corners of the semiconductor laser. In the figure, x ₁ is the distance between the front facet of the laser diode and the reflection surface, and Z ₁ is the height of the laser diode.
(For example, 120 μ), Z ₂ indicates the distance to the light emitting surface. Further, t1 represents the thickness of the uniaxial crystal plate (for example, 2 mm as described later).

Here, the hatched portion in the figure is shown from the viewpoint of what happens when the uniaxial crystal plate is attached onto the substrate as described above, and according to the present apparatus configuration, this portion is unnecessary. Means that. If the trapezoidal optical member for detecting magneto-optical field (trapezoidal prism), whose reflective surface is also formed by the uniaxial birefringent plate itself, is bonded to the substrate, the direction of 90 ° with respect to the optical axis of the crystal in that case. Therefore, the optical member originally needs to have a large shape including the shaded portion, but in this configuration, there is no such a case, and the shaded portion can be removed and can be removed. Therefore, the uniaxial crystal plate itself can be made small.

Further, specifically, it is not necessary to attach the uniaxial crystal plate portion to the shaded portion, and therefore the point A _{0 in} the figure can be moved to A ₁ . That is, a uniaxial crystal plate having no hatched portion in the figure (that is, a side surface that passes through A ₀ in the figure and is orthogonal to the silicon substrate surface (note that such a side surface is not used as an optical path surface and is therefore used as an optical path) (A uniaxial crystal plate having a shape that does not require polishing as in the case of) is used, and the uniaxial crystal plate having a thickness t ₁ is located at a position where the reflected light from the reflecting surface of the silicon substrate does not interfere (Fig. The uniaxial crystal plate can be brought closer to the semiconductor laser side by the dimension of x ₂ up to the middle A ₁ ) (see also Fig. 1).

In this way, the uniaxial crystal plate used can be small, and the size of the uniaxial crystal plate itself can be reduced, so that the overall lateral size can be reduced and the base portion, that is, the semiconductor laser, and the uniaxial crystal plate can be reduced. The silicon substrate itself on which the crystalline film is arranged can be made smaller accordingly, and the lateral dimension of the package 8 is also made smaller (FIG. 1).

If the thickness of the uniaxial crystal plate used is made small (that is, to make it small), the width of separation of extraordinary light and ordinary light becomes narrow. , The return light from the magneto-optical recording medium that enters the package through the hologram is first reflected by the uniaxial crystal plate.
And when directed to the second photodetector the problem arises that the respective light beams are not separated. On the other hand, in the case of this configuration, without causing such a problem, as a result of being able to achieve miniaturization of the uniaxial crystal plate as described above, a thickness t that can secure a required separation width. ₁ (for example, 2 mm) is sufficient, and it is not necessary to reduce the size in the direction of reducing the thickness. The uniaxial crystal plate 5 in FIG. 1 has a thickness that allows a necessary separation width, and ordinary light and extraordinary light can be well separated on the first and second photodetectors 3a and 3b.

Further, as described above, with respect to the optical axis direction of the crystal,
When it is necessary to cut in the 90 ° direction, cutting itself at 90 ° with respect to the optical axis of the crystal of the above optical component is also difficult to manufacture. That is, it is cut in a certain desired direction with respect to the optical axis of the crystal, since it is necessary to polish the cut surface to be 90 ° with respect to the optical axis of the crystal, the processing becomes complicated, That much
Although it takes a lot of man-hours, this configuration is easy to manufacture.
The upper and lower surfaces 5a and 5b of the uniaxial crystal plate 5 are sufficient for polishing, and the surface 5c that joins the reflecting surface 4 and the back surface is used for positioning. It can be easily obtained at low cost with few processing steps.

Moreover, in the case of using the uniaxial crystal plate 5, a film that transmits 1/2 of light and reflects 1/2 of light, as in the case of the horizontally long trapezoidal prism of the above-mentioned document 3, for example.
(Half mirror) and the structure of using the front reflection film on the upper surface side and reflecting between the upper and lower surfaces of the prism are not required. Therefore, also in this respect, the manufacturing can be made easy and inexpensive. .

Further, since the uniaxial crystal plate 5 can be back-joined to the reflecting surface portion 4 on the semiconductor substrate 1 by skillfully utilizing the back surface portion thereof, the positioning can be easily performed and the uniaxial crystal plate 5 can be positioned at the time of assembly. The surface 5c (vertical surface) of the crystal plate 5 is simply replaced by the rear surface (vertical surface) 4 at the rear corner of the reflecting surface portion 4.
By bonding and adhering both back surfaces so that they are pressed against b, the semiconductor laser 2 and the uniaxial crystal plate 5 can be positioned on the same semiconductor substrate surface. Therefore, of course, there is no troublesome alignment when using a submount like the one of the above-mentioned document 4 (JP-A-3-212828).
In addition to the above-mentioned positioning function, such a structure of backside bonding has a uniaxial crystal plate 5 with a required thickness dimension (t ₁ ),
Furthermore, it is possible to position the semiconductor laser 2 closer to it. In the present embodiment, the reflecting surface portion 4 is formed by etching, but the back surface of the reflecting surface portion is formed during etching so that the installation surface of the uniaxial crystal plate 5 on the substrate becomes the same as the semiconductor laser mounting surface. then, without reducing the thickness of the uniaxial crystal plate having a thickness of t ₁ (FIG. 4), closer only be a semiconductor laser side uniaxial crystal plate to be bonded to the back (see the one-dot chain lines in FIG. 4) Therefore, the size can be reduced, and the required separation width can be obtained.

As described above, according to the present embodiment, it is not necessary to use expensive optical parts such as a multi-layer coating polarizing prism and a half-wave plate, and the manufacture is easy.
The structure is inexpensive, and as described with reference to FIG. 4, the reflecting surface portion 4 is formed by the semiconductor substrate 1 itself, and the uniaxial crystal plate 5 is back-bonded to the reflecting surface portion 4 to realize miniaturization. The reflecting surface portion 4 does not need to be cut in the direction of 90 ° with respect to the optical axis direction of the crystal by using a separate material different from the crystal plate, and the thickness of the crystal plate can be reduced. Instead, the first and second photodetectors 3a, 3b can detect the ordinary light and the extraordinary light satisfactorily, that is, while maintaining the necessary separation width, and also the position of the uniaxial crystal plate 5 can be simply and surely maintained. It can be taken out and is easy to assemble.

Next, a description will be given of the mode of adhesion when the back surface of the uniaxial crystal plate 5 is joined, and a preferred example in that case.
Basically, the back surface 4b of the reflecting surface portion 4 and the surface 5c of the uniaxial crystal plate 5 are bonded by the adhesive 6, and the uniaxial crystal plate 5 is also used.
The lower surface 5b of the above and the surface of the semiconductor substrate 1 corresponding thereto are bonded by the adhesive 6. At this time, the portion facing the photodetector 3 may be masked. Further, the lower right end of the crystal plate 5 may be bonded entirely or partially for reinforcement so as to securely fix it (note that this point is
The same applies to each of the examples described later).

Further, in the case of this embodiment, as described above,
Since the reflecting surface portion 4 is provided by etching, there is a possibility that an undesired radius R may be formed on the right-angled portion of the rear vertical surface 4b of the reflecting surface portion 4, so that the right-angled portion has a curved groove 14 as shown in the figure.
Is provided to prevent the tilt of the uniaxial crystal plate 5 from being caused by a right angle of the uniaxial crystal plate 5 (a corner portion at the lower left end in the figure) on R. The groove 14 can also have a function as an escape of the adhesive. That is, when the crystal plate 5 is bonded to the back surface of the reflection surface 4 of the semiconductor substrate 1, the curved groove 14 provided at the right angle portion is useful in order to reduce the swelling due to the adhesive 6. It is possible to allow an extra adhesive 6 to enter, and the tilt of the uniaxial crystal plate 5 caused by this can be minimized. Further, instead of or together with the groove 14, a corner of the uniaxial crystal plate 5 to be joined may be chamfered (this point may be the same in each of the examples described later).

The apparatus according to the present invention can be applied to a three-beam type magneto-optical pickup apparatus including each of the embodiments described later. When applied to a three-beam type magneto-optical pickup device, for example, the above-mentioned JP-A-64-46243.
Grading similar to the technique described in the publication can be used. That is, this is achieved by forming a grading on the reflection surface portion 4 and converting the light beam emitted from the semiconductor laser 2 into three light beams and guiding them to the recording track surface of the magneto-optical recording medium 11. In this case, the return light from the magneto-optical recording medium 11 is detected by being guided by the photodetector 3 provided on the semiconductor substrate 1 having the same configuration as that of FIG. 13 of the publication. Will be performed.

FIG. 2 shows another embodiment (second embodiment) of the present invention. In this embodiment, similarly, the reflecting surface portion and the optical member (crystal plate) for magneto-optical detection are made of different optical materials, and these are back-bonded to each other, but as shown in FIG. A reflective surface member of different material, for example, BK7 glass material, is provided as the reflective surface portion 4 on the flat semiconductor substrate 1, and the reflective surface portion 4 and the uniaxial crystal plate 5 are bonded at the back surface. Is configured as follows. Regarding the adhesion of the semiconductor substrate 1, the uniaxial crystal plate 5 and the separate reflection surface section 4 (prism), the points already described in the first embodiment are basically the same, but the separate reflection The surface portion 4 is adhered to the bottom surface (prism bottom surface) of the flat semiconductor substrate 1.

In this embodiment, a polarization-dependent hologram element is further provided between the hologram element 10 attached to the glass substrate 10 on the upper surface of the package 8 and the incident surface of the uniaxial crystal plate 5. . That is, the uniaxial crystal plate 5
A surface 5e is formed on the surface of the optical element, and this is used as an incident surface, and the polarization-dependent hologram element 21 is provided on the incident surface.
Other parts may be the same as in the first embodiment of FIG.

In this embodiment, the same effect as that of the first embodiment can be obtained, and in addition, a separate reflecting surface member is used for the reflecting surface part 4. By doing so, in the first embodiment The etching process of the semiconductor substrate can be omitted. That is, a flat semiconductor substrate can be used without such processing. Therefore, as compared with the first embodiment, the inclination of the crystal plate 5 due to the adhesive 6 or the like at the time of bonding can be well prevented. Furthermore, the hologram element mounted on the return optical system from the magneto-optical recording medium, that is, on the upper surface of the package 8.
A polarization-dependent hologram element 21 is provided between 10 and the incident surface of the uniaxial crystal plate 5. This has the effect of increasing the Kerr rotation angle, and for example, of the linearly polarized light component incident on the magneto-optical recording medium (disk), 60% is transmitted and 40% is diffracted. On the other hand, 100% of the Kerr rotation component polarized light is transmitted.
Thus, the so-called Kerr rotation increasing function for apparently increasing the Kerr rotation angle is exhibited, and the polarization-dependent hologram element 21 has such a function. Accordingly, since the return optical system has the polarization-dependent hologram element 21 that increases the Kerr rotation angle, the SN ratio of the magneto-optical signal can be improved when the magneto-optical signal is taken out.

Next, still another embodiment (third embodiment) of the present invention is shown in FIG. Similar to the second embodiment, this embodiment provides a separate reflection surface member as the reflection surface portion 4 on the flat semiconductor substrate 1 and shows an optical member for magneto-optical detection to be back-bonded in FIG. The Wollaston prism 31 is used as described above, and between the hologram element 10 mounted on the upper surface of the package 8 and the incident surface of the Wollaston prism 31, the polarization-dependent hologram element 21, that is, the Kerr rotation angle described above. A polarization-dependent hologram element 21 having an increasing effect is provided. Other parts may be the same as the first embodiment of FIG. 1 or the second embodiment of FIG.

In the present embodiment, the Wollaston prism 31 and the photodetector 3 are configured as follows to perform magneto-optical signal detection and servo signal detection. That is, the return light from the magneto-optical recording medium is separated by an optical path different from that of the light beam from the reflecting surface portion 4, and goes to the Wollaston prism 31. In a return light detection optical system that reproduces information recorded on a magneto-optical recording medium by using separated light and detects a focus error signal and a track error signal, a wallace having the polarization-dependent hologram element 21. Ton Prism 31
Is provided at a position where the separated light enters as convergent light, and separates the converged light into two orthogonal polarization components. The photodetector 3 is located in front of the condensing point of one polarization component and behind the condensing point of the other polarization component in the plane including the optical axes of the two polarization components transmitted through the Wollaston prism 31. It has a photodetector 3a, 3b that is provided at a position and is composed of a plurality of light receiving elements for receiving both of the two polarization components, and by the output from each light receiving element of the photodetector, The information recorded on the magneto-optical recording medium is reproduced, and the focus error signal is detected by the spot size detection method based on the difference in the size of the light spot formed on the photodetector.

According to the present embodiment, the same effects as the effects of the first and second embodiments, that is, the positioning by the back bonding and the improvement of the SN ratio of the magneto-optical signal by the Kerr rotation angle increasing function can be obtained. In addition, in the case of the Wollaston prism 31, the thickness of the crystal plate as an optical member for magneto-optical detection that is back-bonded to the reflecting surface portion 4 is reduced because the dispersion angle can be made larger than that of the uniaxial crystal plate. be able to. The size in the height direction of the optical member for magneto-optical detection to be used can be reduced, and therefore, the size in the width direction of the package 8 can be reduced as already described in the first embodiment.
The dimension of the package 8 in the optical axis direction can be reduced. In this way, by using the Wollaston prism 31 as the crystal plate and integrating the hologram having polarization dependence, the crystal plate, and the photodetector as shown in FIG. Therefore, the size can be further reduced. Furthermore, Wollaston prism 31
Is excellent in mass productivity, and therefore is very practical because it can be easily manufactured and can be constructed at low cost.

Further, 2 having different refractive index anisotropies from each other
A larger trapezoidal prism shape can be obtained by combining triangular prisms using different types of birefringent materials, and thus a smaller size can be achieved in this case.

The present invention is not limited to the above-mentioned embodiments and modifications. For example, it is of course possible to adopt a mode in which the reflecting surface portion of the semiconductor substrate according to the first embodiment and the Wollaston prism according to the third embodiment are combined.

[0051]

According to the present invention, the reflection part (example
For example, a mirror) and an optical material different from the reflection part (for example,
(For example, crystals), the return light from the magneto-optical recording medium reflects
Incident on the photodetector through a different optical path without going through the lens
Can be joined in place and can be joined on the back side of the reflective part
Allows easy positioning, easy assembly, small size and light weight
Can be realized. Furthermore, there is no need to use optical components such as a polarizing prism with a multi-layer coating and a half-wave plate, and it is possible to make the structure easy and inexpensive.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a magneto-optical pickup device relating to a magneto-optical unit of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing still another embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining the principle of the configuration according to the present invention.

[Explanation of symbols]

1 semiconductor substrate 2 semiconductor laser 3 photodetector 3a first photodetector 3b second photodetector 4 reflecting surface 5 uniaxial crystal plate 6 adhesive 7 monitor photodetector 8 package 9 glass substrate 10 hologram element 11 magneto-optical recording medium 12 collimator lens 13 objective lens 14 groove 21 polarization dependence of the hologram element 31 Wollaston prism

Claims (3)

(57) [Claims] 1. A semiconductor laser arranged on a semiconductor substrate.
And an analyzer, and first and second electrodes formed on the semiconductor substrate.
A second photodetector and a semiconductor device provided on the semiconductor substrate,
Reflective surface part facing the semiconductor laser at a predetermined angle
And a package arranged at a position away from the semiconductor substrate.
Beam splitter on a transparent substrate combined with
And the reflection surface portion emitted from the semiconductor laser.
When the more reflected light beam is guided to the magneto-optical recording medium,
The return light from the magneto-optical recording medium from the reflecting surface portion
Through the optical path different from the light beam of
Magneto-optical unit for guiding to first and second photodetectors
And The reflecting surface section and the analyzer are made of different optical materials.
And both are joined at the back of its reflective surface.
And an optical unit for magneto-optical characteristics. 2. The optical material of the reflecting surface of the reflecting surface portion is glass.
The optical material of the analyzer is
The magneto-optical device according to claim 1, which is made of a crystal.
Optical unit. 3. The analyzer comprises the beam splitter.
A polarizing hologram is formed on the surface on which the deflected return light is incident.
The magneto-optical device according to claim 2, characterized in that
Optical unit.