JPH04176040A - Optical pick-up device - Google Patents

Abstract

PURPOSE:To improve the efficiency of utilization of reflected light per the area of a converging grating-coupler, to stabilize a detecting signal and to enhance accuracy by superposing and arranging a plurality of the converging grating-couplers at the same position on an optical guide formed on a waveguide substrate. CONSTITUTION:Outgoing beams from a semiconductor laser 2 are passed through a substrate 10 and converging grating-couplers 11-13, formed in parallel by a collimating-lens 3, and converged and projected onto the surface of a magneto-optical disk 9 by an objective 4. Reflected light from the magneto- optical disk 9 is passed through the objective 4 and the collimating-lens 3 and projected into a region, in which the converging grating-couplers 11-13 are formed, propagated to an optical guide layer 14 and converged, projected to photoelectric transducers 21, 22a and 22b, 23a and 23b respectively, and converted into electric signals, and tracking-error signals are prepared by adders 35-38 and subtracters 31-34. Accordingly, the efficiency of utilization of the converging grating-coupler is improved, a detecting signal is stabilized, and accuracy is enhanced.

Description

[Detailed Description of the Invention] Summary of the Invention A magneto-optical recording medium (magneto-optical disk) or an optical recording medium (
This is an integrated optical beam sofa knob device for use with optical disks (optical disks), in which a plurality of light collecting grating couplers are formed on an optical waveguide layer formed on a substrate, and reflected light from a magneto-optical disk or an optical disk is collected. An optical grating coupler guides light to an optical waveguide layer, separates and focuses the light, and detects the focused reflected light to generate a tracking error signal, a focusing error signal, and an information reading signal. It is characterized in that the light condensing grating coupler is formed on the optical waveguide layer at the same location so as to be superimposed thereon. This increases the utilization efficiency of reflected light per unit area of the condensing grating coupler, making it possible to obtain a stable signal.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium and an optical pickup device for an optical recording medium.

BACKGROUND OF THE INVENTION 2. Description of the Related Art Prior Art and Its Problems Research is being actively conducted with the aim of realizing a compact and lightweight optical pickup device for a magneto-optical disk using optical integration technology. For example, Sunagawa et al. "Waveguide type differential detection device for magneto-optical disk pickup" Institute of Electronics, Information and Communication Engineers, Quantum Electronics Study Group Material 0QE8B-177
The optical pickup device described in TM mode and TE mode
A plurality of condensing grating couplers that excite each mode of light are formed on an optical waveguide layer formed on a substrate,
The reflected light from the magneto-optical disk is guided to the optical waveguide layer by the above-mentioned focusing grating coupler, separated and focused according to the mode, and the focused reflected light is detected to generate a tracking error signal, focusing signal, etc. Generates error signals and information read signals.

The collection grating coupler described in the above-mentioned document is shown in FIG. In this figure.

Three condensing grating couplers 91, 92 and 93 are formed side by side on the optical waveguide layer of the substrate 90. The reflected light from the magneto-optical disk is incident on these condensing grating couplers 91 to 93 from directly above or from diagonally above. The condensing grating coupler 91 has a grating period other than the condensing grating coupler 92 .
The condensing grating couplers 92 and 93 are made to be slightly thicker than 93, and are made to excite 7M mode light and to excite TE mode light, respectively. The reflected light from the magneto-optical disk is composed of the P component (E) of the electric field and the S component of the electric field.
It is expressed as a composite vector of components (E). The E component of the reflected light satisfies the phase matching condition at the condensing grating coupler 91 and excites 7M mode light.

The E component of the reflected light is collected using a condensing grating φ92
, 93 satisfy the phase matching condition and excite the TE mode light. The E component is the condensing grating coupler 92, 9: (
There is almost no optical coupling with the E component, and there is almost no optical coupling of the E component with the condensing grating coupler 91. In this way, the E component and the E component of the reflected light from the magneto-optical disk are separated by the condensing gratings S couplers 91 and 92.93, respectively, and are focused (on the optical waveguide layer or on the substrate 90). (located at the end face of the). This focused light is received by each photodetector, and a read signal, a focusing error signal, and a tracking error signal are generated based on the output signals of these photodetectors.

In the condensing grating coupler as mentioned above,
Since the two types of waveguide modes, TM mode and TE mode, are excited only in separate regions, that is, 7M
The mode light is generated only in the area where the condensing grating coupler 91 is formed.

For TE mode light, condensing grating coupler 92°93
are excited only in the regions where they are formed, so
There is a problem that the light usage efficiency is poor.

Although the reflected light from the magneto-optical disk enters the entire area of these condensing grating couplers 91, 92, 93, it is optically coupled to the optical waveguide layer only in a part of the area. Therefore, fewer reflected light components enter the photodetector, making it difficult to stably detect various signals.

In addition, due to wavelength fluctuations of the light source, expansion and contraction of the grating due to temperature changes, etc., the T
Light other than M mode may be excited.

Since light other than the TE mode is excited in the condensing grating couplers 92 and 93, there is also the problem that complete mode separation is not possible and the detection accuracy of various signals is not sufficiently high.

Similarly, a small and lightweight optical pickup device for an optical disk using optical integration technology has also been proposed. For example, ``Optical concentrator M circuit of optical disk pickup'' Institute of Electronics, Information and Communication Engineers, Quantum Electronics Research Group Material 0QE8
A part of the optical pickup device described in No. 5-72 is shown in FIG. An optical waveguide layer 102 is formed using glass on a Si substrate 100 via a SiO□ buffer layer 101, and patterning is performed on this optical waveguide layer 102 by patterning using electron beam lithography and reactive ion etching technology. .

A Chaves-type condensing grating coupler 103 and a waveguide beam splitter (grating) 104 are formed. A laser beam fixed to the end face of the substrate 100
The light emitted from the diode 105 propagates through the optical waveguide layer 102, is emitted upward by the condensing grating coupler 103, and is focused onto the surface of the optical disk 109. The reflected light from the optical disk 109 is coupled to the optical waveguide layer 102 through the condensing grating coupler 103, and is further split into two by the waveguide beam splitter 104, each of which is focused while propagating through the optical waveguide layer 102.
The light is incident on the two-split photoelectric conversion element 106, respectively. A read signal, a focusing error signal, and a tracking error signal are created using the output signal of the photoelectric conversion element 10B. The waveguide beam splitter 104 has three functions: wavefront splitting, deflection, and focusing. In this way, the information represented by the pit rows formed on the surface of the optical disc 109 is read.

In such an optical pickup device, the light emitted from the laser diode 105 is transmitted to the waveguide beam splitter 1.
04 and condensing grating coupler 103 back and forth 1
Since the light passes through the grating four times and reaches the photoelectric conversion element 108, the light received by the photoelectric conversion element 106 is quite weak, and its output signal is also weak.

In addition, shifts in the periods of various gratings occur due to wavelength fluctuations of the laser diode as a light source, temperature changes, etc.
In particular, a shift in the focusing position of the light incident on the photoelectric conversion element 106 occurs. There is a problem in that these factors make it difficult to stably detect various signals.

SUMMARY OF THE INVENTION OBJECTS OF THE INVENTION The present invention is directed to stabilizing and increasing the precision of tracking error signals, focusing error signals, and information reading signals in the above-mentioned optical pickup device.

Structure of the Invention 2 Functions and Effects This invention provides a light source and a projection optical system for projecting a linearly polarized light beam onto the surface of a magneto-optical recording medium, and a plurality of condensing gratings that respectively excite TM mode and TE mode light.・A waveguide substrate with a coupler formed on the optical waveguide, a light receiving optical system that guides the reflected light from the magneto-optical recording medium to the condensing grating coupler on the waveguide substrate, and condensing the light by the condensing grating coupler, respectively. For magneto-optical recording media, the device is equipped with a plurality of photoelectric conversion elements that detect the reflected light, and a signal processing means that generates a tracking error signal, a focusing error signal, and an information reading signal based on the output signals of the photoelectric conversion elements. In an optical pickup device, the plurality of condensing gratings and
It is characterized in that the couplers are arranged overlappingly at the same location on the optical waveguide formed on the waveguide substrate.

According to this invention, a plurality of condensing grating couplers that excite 7M mode and TE mode light are provided in a superimposed manner at the same location on the optical waveguide, so these condensing grating couplers are provided. Coupling of 7M mode and TE mode light to the optical waveguide is achieved using the entire area, and the light utilization efficiency per area is improved. This increases the amount of reflected light from the magneto-optical recording medium that is guided to the photoelectric conversion element, making it possible to perform stable signal processing.

A polarizing plate may be provided in front of the light-receiving surface of the photoelectric conversion element to allow light having a polarization direction specific to the light coupled to the corresponding condensing grating coupler to pass therethrough.

As a result, light in a mode other than the desired mode is excited by the condensing grating coupler, and even if multiple modes are mixed, only the light in the desired mode passes through the polarizing plate and passes through the photoelectric conversion element. Since it is incident on
It is possible to stabilize the detection signal and improve accuracy.

Furthermore, at least a portion of the light projecting optical system and the light receiving optical system are shared, and the waveguide substrate is sandwiched between the light projecting optical system and the light receiving optical system.

The light source is arranged on the opposite side of the magneto-optical recording medium, and the waveguide substrate is transparent and has a polarization separation function part that allows only light in a specific polarization direction to pass among the light emitted from the light source. It is recommended to adopt it.

This arrangement of the optical system allows the optical system to be configured compactly. Further, the polarization direction of the light emitted from the light source can be controlled by the arrangement of the waveguide substrate. This is particularly effective when the positioning accuracy of the waveguide substrate is higher than that of the light source.

This invention also. A light source that generates a light beam to be projected onto the surface of an optical recording medium, a plurality of photoelectric conversion elements that detect light reflected from the optical recording medium, and a light projection optical system that projects the light from the light source directly onto the surface of the optical recording medium or through a projection optical system. A light-emitting condensing grating coupler for projecting light and a light-receiving condensing grating coupler for receiving reflected light from an optical recording medium directly or through a light-receiving optical system and condensing and guiding it to the photoelectric conversion element. A light beam for an optical recording medium, comprising a waveguide substrate formed on an optical waveguide, and a signal processing means for generating a tracking error signal, a focusing error signal, and an information reading signal based on the output signal of the photoelectric conversion element. The pickup device is characterized in that the light-emitting and light-receiving condensing grating couplers are disposed overlappingly at the same location on an optical waveguide formed on a waveguide substrate.

According to this invention, a plurality of condensing grating couplers for light emission and light reception are formed in one place, so that the light only makes one round trip through this composite grating coupler, so that it is not attenuated much. It is possible to stably detect various signals without any interference.

Preferably, the waveguide substrate is made of a semiconductor material.

It is preferable that a plurality of photoelectric conversion elements be integrally formed on this substrate, and that the optical waveguide is provided with an optical coupler for coupling reflected light propagating through the optical waveguide to the photoelectric conversion element. This enables further integration.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows a first embodiment of an optical pickup device according to the present invention. This optical pickup device is suitable for reading information from a magneto-optical disk.

From now on, the pickup device uses a semiconductor laser 2 as a light source. A substrate 10 on which a composite focusing grating coupler 1 is formed. It includes a collimating lens 3 and an objective lens 4. These optics are integrated into tracking and focusing actuators (paths shown).

Details of the composite collection grating coupler 1 formed on the substrate 10 are shown in FIGS. 3-5. FIG. 3 is a perspective view showing the entire substrate on which the composite condensing grating coupler is formed.

Here, each grating is represented by a solid line with a thickness of 1. FIG. 4 is an enlarged view showing each grating in detail. Further, FIG. 5 is an enlarged sectional view taken along the line v--v in FIG. 3.

An optical waveguide layer 14 is formed on the substrate 10, and this optical waveguide layer 1
Two types of gratings 11 and 12 are placed in a predetermined area on 4,
13 are formed on top of each other. One grating 11 is formed over the entire area, constitutes a condensing grating coupler, and has a period that excites the 7M mode of light having the wavelength of the light emitted from the semiconductor laser 2. E of the reflected light from the magneto-optical disk 9 that enters this area from directly above or diagonally above.

The component is coupled to this grating 11 and the optical waveguide layer 1
4 and is focused at the edge of the substrate 10. The other gratings 12 and 13 are formed at the left and right halves of the area, respectively (their boundary line and its extension line are indicated by T6), and constitute a condensing grating coupler with different condensing positions, It has a period that excites TE mode light. The E component of the reflected light incident on the above region is reflected by the grating 12. ia, propagates through the optical waveguide layer 14, and focuses the light on both sides of the light focusing position of the light collecting grating coupler 11.

When the condensing grating couplers 11 and 12.13 overlap, it means that the protrusions of these gratings cross each other on the same plane, as shown in FIG.

Furthermore, on the optical waveguide layer 14 of the substrate 1O, a photoelectric conversion element 21 is installed at a substantially converging position of the light coupled to the condensing grating coupler 11, and a condensing grating coupler 12.13.
Two-split type photoelectric conversion elements 22a and 22b, and 23a and 23b are provided at substantially the condensing positions of the light coupled to the two.

Returning to FIG. 1, the semiconductor laser 2 is preferably arranged so that the polarization plane of its emitted light (linearly polarized light) is inclined by 45'' with respect to the tangent line (indicated by the symbol TR) of the track of the magneto-optical disk 9. Further, the substrate 10 is arranged between the semiconductor laser 2 and the collimating lens 3, and the boundary line TG between the condensing grating couplers 12 and 13 on the substrate 10 is parallel to the track tangent TR. Furthermore, the optical axis of the emitted light from the semiconductor laser 2 passes through the center of the condensing grating coupler region on the substrate IO (the center on the boundary line Tc), and further passes through the collimating lens 3 and the objective lens 4. The optical system is positioned so as to pass through the center of.

The emitted light from the semiconductor laser 2 spreads through the substrate 10 and the condensing grating couplers 11, 12 .
13 (0th order diffracted light) is collimated by a collimating lens 3, and further condensed by an objective lens 4 and projected onto the surface of a magneto-optical disk 9. The reflected light from the magneto-optical disk 9 passes through the objective lens 4 and the collimating lens 3 and is focused into a region where the focusing grating couplers 11, 12 and 13 are formed. As described above, the E component of the two reflected lights is optically coupled to the condensing grating coupler 11 as 7M mode light.

While being focused through the optical waveguide layer 14 on the substrate 10, the light is detected by the photoelectric conversion element 21 and converted into an electrical signal. The E component of the reflected light from the magneto-optical disk 9 is coupled to the gratings 12 and 13, respectively, and propagated through the optical waveguide layer 14 as TE mode light.

And by condensing the light, each photoelectric conversion element 22
The light enters a and 22b and 23a and 23b and is converted into an electrical signal.

When the spot position of the projected light on the magneto-optical disk 9 deviates from the track, the amount of light incident on the left and right condensing grating couplers 12 and 13 changes depending on the amount of deviation. Therefore, photoelectric conversion elements 22a, 22b and 2
(The amount of light incident on the photoelectric conversion elements 22a and 23b also changes. Therefore, the sum signal of the output signals of the photoelectric conversion elements 22a and 22b is obtained by the adder 38, and the sum signal of the output signals of the photoelectric conversion elements 23a and 23b is obtained by the adder 35. and the difference between these sum signals is subtracted by subtractor 3.
4, a tracking error signal is created. This is tracking error detection using the push-pull method.

Furthermore, if the distance between the magneto-optical disk 9 and the objective lens 4 changes, the condensing grating coupler 12.1
3, the focal position of the light condensed on the optical waveguide layer 14 is shifted in the light propagation direction. Along with this, the focal point position is also slightly shifted in a direction perpendicular to the light propagation direction. Therefore, when the magneto-optical disk 9 moves away from the objective lens 4, the amount of light incident on the inner charge conversion elements '12a, 23a increases, and conversely, the magneto-optical disk 9 moves away from the objective lens 4.
When approaching the outer photoelectric conversion elements 22b, 23
The amount of guided light incident on b increases. An adder 37 obtains a sum signal of the output signals of the inner photoelectric conversion elements 22a and 23a.

The adder 36 obtains a sum signal of the output signals of the outer photoelectric conversion elements 22b and 23b, and the subtracter 33 calculates the difference between these sum signals.
An error signal is obtained. This is focusing error detection using the Foucault method.

Information recorded on the magneto-optical disk 9 is expressed by the rotation angle of the polarization direction of the reflected light (Kerr effect). This rotation angle is the E component of the reflected light and the E component
It is expressed by a change of s minutes. The size of the E component coupled to the condensing grating coupler 11 is the same as that of the photoelectric conversion element 2.
1 is converted into an electrical signal. The magnitude of the E component coupled to the condensing grating coupler 12.13 is that of the four photoelectric conversion elements 22a, 22b, and 23a.

The sum signal of the output signals of 23b is sent to adders 35, 38 and 3.
It can be obtained by calculating 2. Therefore, by calculating the difference between the output signal of the photoelectric conversion element 21 and the output signal of the adder 32 using the subtracter 31, an information read signal can be obtained.

FIG. 2 shows a modification, in which the collimating lens 3 is omitted. The objective lens 4 focuses the projected light and the reflected light. According to this optical system, since the number of lenses is reduced, it is possible to further simplify and reduce the weight of the optical system.

In the optical system shown in FIGS. 1 and 2, a substrate IO having a composite condensing grating coupler 1 is connected to a semiconductor laser 2.
and a collimating lens 3 or an objective lens 4, and the reflected light being collected by these lenses 3 or 4 enters the composite collection grating coupler 1. Therefore, since the aperture of this incident light becomes small, the area in which the grating coupler 1 is formed can be made small, and its fabrication becomes easy.

Of course, the substrate IO may be placed between the collimating lens 3 and the objective lens 4 in FIG.

The above-described composite condensing grating coupler 1 is produced as follows.

An electron beam resist is applied onto a given substrate.

By electron beam writing a composite condensing grating pattern as shown in FIG. 3 and developing it, a composite condensing grating pattern is formed using a residual film resist.

The composite light-concentrating grating pattern made from this residual film resist is transferred using electroforming or other methods to create a nickel film.
Create a standby.

An ultraviolet (UV) curable resin is filled between the standber and the substrate (for example, a glass substrate) 10, and the UV curable resin is cured by pressurizing them and irradiating them with ultraviolet rays. The optical waveguide layer 14 and the condensing grating coupler 11 are made of UV curing resin. , 12 and (3) are integrally formed.

6 and 7 show other examples of composite collection grating couplers.

This composite focusing grating coupler is shown in Figures 3 to 5.
It basically has the same configuration as shown in the figure. That is, the focusing grating coupler IIA, 12A,
13A are the condensing grating couplers 11.
Compatible with 12.13.

Thickness (height of ridges) of grating IIA that excites TM mode and grating 12 that excites TE mode
A, the thickness of 13A is different. The thickness of the grating affects the diffraction efficiency (coupling efficiency). By changing the thickness of grating IIA and gratings 12A and 13A, the intensity of the focused light can be adjusted (eg, made equal). Thereby, when extracting optical differential signals (information reading signals) between the TE mode and the 7M mode, the output levels of both modes can be made equal.

Although a step type grating is shown in the above embodiment, a grating with any cross-sectional shape, such as a blazed grating, may be used.

FIG. 8 shows another example of a waveguide substrate on which a composite concentrating grating coupler is formed. The focus position of each collection grating coupler 11, 12 and 13 is on the substrate lO
These focusing gratings are located at the end face of the
A coupler is formed. Then, at the focal position of each condensing grating coupler, a photoelectric conversion element (for example, a 7t diode) 21.22a is attached to the end surface of the substrate lO.
, 22b, 23a.

23b is attached (eg, glued).

FIGS. 9 and 10 show still other examples. Here, an optical waveguide layer 15 is formed on a substrate 10 by sputtering an inorganic material such as ZnS or ZnO, and condensing grating couplers 11, 12 and 13 made of UV curable resin are formed thereon. .

When producing a gray 5-ting using a UV curable resin, a thin UV curable resin film 16 is inevitably formed on the optical waveguide layer 15.

Such a composite collection grating coupler is also fabricated by a method similar to that described above. That is, the optical waveguide layer 15 is formed on the substrate IO.

A UV curing resin is filled between the optical waveguide layer I5 and the standby of the composite grating, and cured by ultraviolet irradiation.

Since the optical waveguide layer 15 is manufactured by a thin film technique such as sputtering of an inorganic material, the thickness of the optical waveguide layer can be easily controlled.

FIG. 11 shows yet another example.

Here, a polarizing plate 10A is used as the substrate. This polarizing plate LOA transmits light in the polarization direction of the light emitted from the semiconductor laser 2. A polarizing film may be formed on a glass substrate.

By providing the waveguide substrate with a polarization separation function in this manner, even if the light emitted from the semiconductor laser 2 contains some component other than the amount of linearly polarized light, this can be removed.

Furthermore, even if the semiconductor laser 2 is not positioned with high precision so that the polarization direction of the emitted light from the semiconductor laser 2 has an angle of 45'' with the tangent TR direction of the track of the magneto-optical disk 9,
All that is required is to correctly position the polarization direction of the waveguide substrate 10A. This is because the substrate 10A is larger than the semiconductor laser 2.
This is effective when positioning is easy.

In the example shown in FIG. 11, charging conversion elements 21.22g and 22b, and 2
Polarizing plates 24 and 25 are provided in front of the light receiving surfaces of 3a and 23b. The polarizing plate 24 allows only light in the 7M mode polarization direction to pass through. As a result, even if light in a TE mode other than the 7M mode is coupled to the condensing grating φ coupler 11, the photoelectric conversion element 21 can detect only the light in the 7M mode. Similarly, the polarizing plate 25 is T
Only light in the E mode polarization direction is passed through the photoelectric conversion element 22. a, 22b.

Only TE mode light is made to enter 23a and 23b.

Only the polarizing plates 24 and 25 may be provided without using the substrate as a polarizing plate, or the substrate may be used as a polarizing plate without providing the polarizing plates 24 and 25.

FIG. 12 shows a second embodiment of the optical pickup device according to the present invention. This optical pickup device is suitable for reading information from an optical disc.

An optical waveguide layer 43 made of UV curable resin is formed on a glass substrate 40, and a composite condensing grating coupler 50 is formed on this optical waveguide layer 43. The composite condensing grating coupler 50 can be integrally formed with the optical waveguide layer 43 using a UV curable resin by the method described above using a standber. The composite light collecting grating coupler 50 includes a light emitting light collecting grating coupler 51 formed in the entire area, and two light receiving light collecting grating couplers 52 and 53 formed by dividing this area into two parts. These gratings are stacked one on top of the other. The grating periods of the grating couplers 51 to 53 may all be the same. The mode of light propagating through the optical waveguide layer 43 depends on the direction of the polarization plane of the light emitted from the semiconductor laser 41.

A semiconductor laser 41 is fixed to the end face of the substrate 40. The light emitted from the semiconductor laser 4I propagates through the optical waveguide layer 43 while spreading, and is emitted upward and collimated by the light projecting condensing grating coupler 51 of the composite condensing grating coupler 50.

This parallel light is focused by the objective lens 42 and forms a spot near the surface of the optical disk 49.

On the optical disc 49, pit rows representing information are formed. The light projected onto the optical disk 49 is intensity-modulated by the pits and reflected. This reflected light enters the objective lens 42 while being spread, is collimated, and enters the composite condensing grating coupler 50. The light-receiving condensing grating couplers 52 and 53 included in the composite condensing grating coupler 50 have three functions: wavefront division, deflection, and condensing of light. Focusing grating coupler 52.5
The reflected light coupled to the optical waveguide layer 43 by the optical waveguide 3 travels in the optical waveguide layer 43 in separate directions while being condensed.

The light is received by two pairs of two-split type photoelectric conversion elements 62a, 62b and (j3a, 63b, respectively) fixed to the end surface of the substrate 40.These photoelectric conversion elements 62a, 62
b.

A read signal based on the output signals of 83a and 63b.

The focusing error signal and tracking error signal are generated as described above. Here, a read signal is obtained by adding the outputs of adders 35 and 38 in adder 32.

In the embodiment shown in FIG. 12, the objective lens 42 is disposed between the optical disk 49 and the substrate 40.

Focusing control is performed by moving the objective lens 42.

FIG. 13 shows a modification, in which no objective lens is provided. Composite condensing grating coupler 5
0A is of chirve type. That is, the light-emitting condensing grating 51A and the light-receiving condensing gratings 52A and 53A are both formed in a chirve shape, and have a condensing function for emitted light and incident light. The light emitted from the semiconductor laser 41 is emitted upward from the optical waveguide layer 43 by the condensing grating coupler 51A, and is condensed to form a condensed spot on the surface of the optical disk 49. The reflected light from the optical disk 49 enters the condensing grating couplers 52A and 53A, respectively, and propagates through the optical waveguide layer 43 while being condensed, and is transmitted to the photoelectric conversion elements 62a and 53A.
62b, 63a, 63b are reached. In this modification, focusing control is performed by moving the entire substrate 40.

FIG. 14 shows yet another modification. An n-type Si substrate 70 is used as the substrate, on which an optical waveguide layer 72 is formed of a thin film forming material such as ZnO or ZnS with a buffer layer 71 made of UV curable resin interposed therebetween. A composite condensing grating coupler 50 is integrally formed on the optical waveguide layer 72 .

Since the substrate 70 is a Si substrate, a two-part photoelectric conversion element (pn junction photodiode) 82a,
82b, 83a, and 83b are provided. That is, as shown enlarged in FIG. 16, n-type Si
By doping the substrate 70 with p-type impurities, a p region 70a is formed to form a pn junction.

Photoelectric conversion element 82a (82b, 83a, g3
b). The area other than the surface of this p region 70a is covered with a 5i02 insulating film 73, and the p region 70a
An electrode 74 is formed around the . A light reception signal can be extracted from this electrode 74 and an electrode 75 formed on the back surface of the substrate 70. A grating coupler 81 is also formed on the optical waveguide layer 72. The light that is coupled to the optical waveguide layer 72 by the condensing grating coupler 52 (53) and propagated while condensing through the optical waveguide layer 72 is diffracted by the grating coupler 81 and enters the p region 70a. By integrally forming the photoelectric conversion element on the substrate in this manner, further integration can be achieved.

FIG. 15 shows yet another modification. here,
A chirve-shaped composite condensing grating coupler 50A shown in FIG. 13 is provided on an optical waveguide layer 72 on a substrate 70 on which a photoelectric conversion element shown in FIG. 14 is integrally formed, and an objective lens is omitted. .

17a to 17f show the manufacturing process of the optical waveguide layer shown in FIG. 14 or 15. FIG.

Composite focusing grating coupler 50 (or 50A)
Then, a nickel stamper 85 having the same pattern as the linear grating coupler 81 is manufactured (No. 17).
Figure a). This can be produced using a master disc produced by electron beam lithography as described above.

Next, a UV curing resin 86 is injected between the stand bar 85 and the glass substrate 87, and the UV curing resin 86 is cured by ultraviolet irradiation (FIG. 17b).8 The stand bar 85 is peeled off (FIG. 17c).

An optical waveguide layer 72 is formed by sputtering ZnO, ZnS, etc. onto the UV curable resin layer 86 onto which the grating pattern has been transferred (FIG. 17d). Optical waveguide layer 72
The thickness can be controlled with high precision.

Further, a p-type region 70a, a 5i02 film 73. Si substrate 70 on which electrodes 74, 75, etc. are formed and optical waveguide layer 72
A UV curable resin 71A that will become the buffer layer 71 is injected between the
Figure 17e).

Finally, the glass substrate 87 and the UV cured resin layer 8B are separated (FIG. 17f). The UV cured resin layer 8B may be left as is.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the present invention, and is a perspective view of an optical system of an optical pickup device. FIG. 2 is a perspective view showing a modification. Figures 3 to 5 show the waveguide substrate and the composite condensing grating coupler formed thereon. Figure 3 is an overall perspective view, Figure 4 is a partially enlarged perspective view, and FIG. 5 is an enlarged sectional view taken along the line v--v in FIG. 3. FIGS. 6 and 7 show other examples of a waveguide substrate and a composite light collecting grating coupler, with FIG. 6 being a perspective view of the entire structure and FIG. 7 being an enlarged perspective view of a portion thereof. FIG. 8 is a perspective view showing another example of the waveguide substrate. FIG. 9 is a perspective view showing still another example of the waveguide substrate, the first
FIG. 0 is an enlarged sectional view taken along the line X--X in FIG. 9. FIG. 11 is a perspective view showing still another example of the waveguide substrate. FIG. 12 shows a second embodiment of the invention, and is a perspective view of an optical system of an optical pickup device. FIGS. 13, 14, and 15 are perspective views showing modified examples, respectively. FIG. 18 is an enlarged sectional view showing a photoelectric conversion element formed within the substrate. FIGS. 17a to 17f are cross-sectional views showing the manufacturing process of the waveguide substrate shown in FIG. 14 or 15. FIG. FIG. 18 is a plan view of a grating coupler used in a conventional optical pickup device. FIG. 19 is a perspective view showing an optical system of a conventional optical pickup device. 1, 50.50A...Composite condensing grating coupler. 2.41...Semiconductor laser. 3...Collimating φ lens. 4.42...Objective lens. 9... Magneto-optical disk. 10, 40.70...Substrate. 10A...Polarizing plate (substrate). 11, 12.13. IIA, L2A, 13A. 51, 52.53.51A, 52A, 53A...
Concentrating grating coupler. 14, 15.43.72... Optical waveguide layer. 21, 22a, 22b, 23a, 23b. 82a, 82b, 83a, 63b. 82a, 82b, 83a, 83b...photoelectric conversion elements. 24, 25...Polarizing plate. 31, 33.84...Subtractor. 32, 35-38...Adder. 49...Optical disc. 81...Linear grating coupler. Patent applicant: Omron Co., Ltd. Agent: Patent attorney: Ken Ushiku
Fig. 6 Fig. 7 Fig. 11 Fig. 8 Fig. 9 Fig. 10 Fig. 16 Fig. 8I Fig. 14 1115 Fig. 70a Old Fig. 19

Claims (5)

[Claims] (1) A light source and projection optical system for projecting a linearly polarized light beam onto the surface of a magneto-optical recording medium, and a plurality of condensing gratings and couplers that excite TM mode and TE mode light, respectively, are formed on the optical waveguide. waveguide substrate,
a light-receiving optical system that guides reflected light from the magneto-optical recording medium to the condensing grating coupler on the waveguide substrate; a plurality of photoelectric conversion elements each detecting the light condensed by the condensing grating coupler; A device comprising a signal processing means for generating a tracking error signal, a focusing error signal, and an information reading signal based on an output signal of a photoelectric conversion element, wherein the plurality of condensing grating couplers are formed on a waveguide substrate. What is claimed is: 1. An optical pickup device for a magneto-optical recording medium, characterized in that the optical pickup devices are arranged in an overlapping manner at the same location on an optical waveguide. (2) According to claim (1), a polarizing plate is provided in front of the light-receiving surface of the photoelectric conversion element to pass light having a polarization direction specific to the light coupled to the corresponding condensing grating coupler. The optical pickup device for the magneto-optical recording medium described above. (3) At least a portion of the light emitting optical system and the light receiving optical system are shared, the light source is arranged on the opposite side of the magneto-optical recording medium with the waveguide substrate in between, and the waveguide substrate is transparent; The optical pickup device for a magneto-optical recording medium according to claim 1 or 2, further comprising a polarization separation function portion that allows only light in a specific polarization direction to pass among the light emitted from the light source. (4) A light source that generates a light beam to be projected onto the surface of an optical recording medium, a plurality of photoelectric conversion elements that detect reflected light from the optical recording medium, and a light source that directly projects or projects the light from the light source onto the surface of the optical recording medium. A light-projection condensing grating coupler for projecting light through an optical system, and a light-receiving condensing grating for receiving reflected light from an optical recording medium directly or through a light-receiving optical system and condensing and guiding the light to the photoelectric conversion element. - A waveguide substrate in which a coupler is formed on an optical waveguide, and a signal processing means for generating a tracking error signal, a focusing error signal, and an information reading signal based on the output signal of the photoelectric conversion element, An optical pickup device for an optical recording medium, characterized in that the light emitting and light receiving condensing grating couplers are arranged overlappingly at the same location on an optical waveguide formed on a waveguide substrate. (5) The waveguide substrate is made of a semiconductor material, a plurality of photoelectric conversion elements are integrally formed on the substrate, and an optical coupler for coupling reflected light propagating through the optical waveguide to the photoelectric conversion element is attached to the optical waveguide. An optical pickup device for an optical recording medium according to claim 4, further comprising an optical pickup device for an optical recording medium.