JP2000123391A - Optical waveguide unit, and optical head using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide unit which is of a thin type and moreover permits three-dimensional arrangement of an optical waveguide element and connection of electrical wiring with ease. SOLUTION: In this optical waveguide unit 1, a light source 6 like laser, etc., an optical waveguide element 5 for detecting the light reflected from an object irradiated with light by a photo-detector via the optical waveguide, and a light reflecting means 10 for coupling the reflected light to the optical waveguide of the optical waveguide element 5 are mounted in a package 2, and the optical waveguide element 5 is arranged so that the substrate surface 15a forming the optical waveguide thereon is orthogonal to the optical axis of the reflected light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide unit mounted with an integrated optical waveguide element applied to an optical pickup, an optical integrated circuit, an optical sensor and the like of an optical information recording / reproducing apparatus.
And an optical head using the same.

[0002]

2. Description of the Related Art When a signal from a magneto-optical disk is detected by an optical pickup, light from a semiconductor laser is generally reflected by the magneto-optical disk, and the reflected light is used for detecting a servo error signal and detecting the magneto-optical signal. Separated into light for
Use for each purpose. At this time, a beam splitter is used to split the light.

FIG. 8 is a plan view showing an example of an optical pickup for a magneto-optical disk device having such a configuration.
For example, it is disclosed in JP-A-8-171747.

In FIG. 8, a laser beam emitted from a semiconductor laser 6 provided in a package 2 is divided into a main beam and a tracking beam by a grating 25, passes through a hologram 27, and enters a beam splitter 26. Is done. The beam splitter 26 is formed by laminating a flat glass 43 and a prism 44, and the incident light is reflected by a mirror surface M1 at a boundary surface between the flat glass 43 and the prism 44, passes through the collimating lens 22, and then starts up. The light is reflected upward by a mirror 23 perpendicularly to the drawing, and is condensed on a magneto-optical disk (not shown) by an objective lens 24.

The light reflected by the magneto-optical disk again passes through the objective lens 24, the rising mirror 23, and the collimating lens 22 and is incident on the beam splitter 26, and the mirror surfaces M1 and M2 at the upper and lower interfaces of the flat glass 43. Are reflected respectively. The light reflected on one mirror surface M1 is used as the servo error signal detection light L1 as the hologram 27.
, And is diffracted by the photodiode 7 (FIG. 1).
1) and is detected as a servo error signal.

The light reflected by the other mirror surface M2 passes through the right side of the hologram 27 as the magneto-optical signal detection light L2, is guided into the package 2, and enters the prism 10.

Reference numeral 4 denotes a lead pin for electrically extracting the package 2 to the outside.

FIGS. 9 and 10 show portions of the package 2 including the prism 10 and the optical waveguide element 5, respectively. FIG. 9 is a sectional view and FIG. 10 is a plan view.

The optical waveguide element 5 includes a beam splitter 26
The optical waveguide 17, the polarization separation element 11, and the photodetection element 12 are integrally formed on a silicon substrate 15 for detecting the rotation of the polarization plane of the magneto-optical signal detection light L2 branched by.

As the polarization splitting element 11, for example, a mode splitter utilizing a difference in the refraction angle of each polarized light is used (for example, see Japanese Patent Application Laid-Open No. 6-82644). Further, the light detection element 12 functions as a photodiode.

A trapezoidal prism 10 is disposed on the optical waveguide element 5, and a micro lens 47 is provided on the prism 10.

The magneto-optical signal detection light L2 guided into the package 2 as described above is converted into parallel light by the microlens 47, then guided by the prism 10, reflected at a predetermined angle, and reflected by the optical waveguide. No. 17.

The light guided to the optical waveguide 17 is separated into TE light and TM light by the polarization splitting element 11, and a magneto-optical signal is detected by the light detecting element 12.

FIG. 11 is a front view of the optical waveguide element 5, the semiconductor laser 6, and the photodiode 7 for detecting a servo error signal shown in FIG. 8 as viewed from a light input / output direction (Z-axis direction).

The polarization direction of the laser light emitted from the semiconductor laser 6 in the Z-axis direction in the figure is set parallel to the X-axis here. On the other hand, the polarization plane of the magneto-optical signal detection light L2 is rotated by 1 to 2 ° due to the Kerr effect. However, since the rotation angle is very small, a polarization component of ± 45 ° with respect to the polarization direction of the light focused on the magneto-optical disk is detected for the magneto-optical signal detection light L2, It is desirable to detect the differential signal. Therefore, as shown in the figure, when the optical waveguide 17 of the optical waveguide element 5 is arranged at an angle of 45 ° with respect to the Y axis, the TE mode and the TM mode in the optical waveguide 17 are polarized in the polarization direction of the light emitted from the semiconductor laser 6. ±
It corresponds to the polarization component in the direction of 45 °, and S / N
And a reproduced signal having a high

However, in the optical pickup having the above-described configuration, the beam splitter 26 is provided with the collimating lens 2.
2 and the hologram 27, the semiconductor laser 6 as a light source and the beam splitter 26
The distance between them increases, so that the beam splitter 26
The area through which light passes (the required effective diameter) was large.

Accordingly, the convergence point of the magneto-optical signal detection light L2 becomes closer to the lower surface of the member on which the grating 25 is formed, and the magneto-optical signal detection light L2 is directly coupled onto the optical waveguide 17. Could not.

As a countermeasure, the provision of the microlens 47 as described above converts the divergent light from the magneto-optical signal detection light L2 into parallel light and then couples the light onto the optical waveguide 17.

Here, the focal length of the micro lens 47 is about 1 mm, and it is not easy to manufacture such a lens having a short focal length on the prism 10.

In the optical pickup having this configuration, the semiconductor laser 6, the photodiode 7, and the optical waveguide element 5 are arranged in an L-shape in a plane (see FIG. 11). The length in the X-axis direction becomes larger by the arrangement of the photodiodes 7. This has been an obstacle to reducing the thickness of the optical pickup.

Therefore, in order to improve these inconveniences,
The present applicant has proposed an optical pickup having a configuration as shown in FIGS. 12 to 14 (for example, Japanese Patent Application No. 9-04051).
No. 7).

FIG. 12 is a plan view of the optical pickup.
Portions corresponding to the configuration shown in FIG. 8 are denoted by the same reference numerals.

In this optical pickup, the light beam from the semiconductor laser 6 is split by the grating 25 into three light beams consisting of one main beam and two tracking beams. Also, the hologram 27
Is to diffract a part of the reflected light from the magneto-optical disk (not shown).

When the light reflected by the magneto-optical disk passes through the grating 25 again, the tracking beam and the main beam overlap, and the information cannot be reproduced correctly, so that the beam splitter 26 moves between the hologram 27 and the grating 25. Are located in Accordingly, the beam splitter 26 is closer to the semiconductor laser 6 than the hologram 27, unlike the case of the configuration of FIG.

The beam splitter 26 has a first reflecting surface 26a for reflecting a part of the reflected light from the magneto-optical disk which has not been diffracted by the hologram 27, and is arranged in parallel with the first reflecting surface 26a. Thus, a second reflection surface 26b for reflecting the light reflected from the first reflection surface 26a again is formed.

Reference numeral 22 denotes a collimating lens, reference numeral 23 denotes a rising mirror, and reference numeral 24 denotes an objective lens. These components are the same as those shown in FIG.

The beam splitter 26 is mounted on a package 28. This package 28
The package 2 includes a base 13, a cap 3, and a cover glass 46, and a semiconductor laser 6, an optical waveguide element 5, and a photodiode 7 are provided in the package 2.

The semiconductor laser 6 and the photodiode 7 are arranged directly on the base 13, and
Are arranged on the base 13 via a wedge-shaped block 62. Further, a trapezoidal prism 10 is arranged on the optical waveguide element 5.

As shown in FIG. 13, a block 62 is formed so that the reflected light from the magneto-optical disk is perpendicularly incident on the inclined surface of the prism 10 and a predetermined incident angle with respect to the waveguide element 5 is obtained. The shape is designed. That is, the angle of the slope of the prism 10 and the angle of the slope of the block 62 correspond to each other, and the slope of the prism 10 is parallel to the plane of the base 13 (perpendicular to the optical axis of the incident light). .

In the above configuration, the light emitted from the semiconductor laser 6 is divided into three beams of two tracking beams and one main beam by the grating 25, and the collimator lens 22, the rising mirror 23,
Each tracking beam spot and main beam spot are formed on a magneto-optical disk (not shown) by the objective lens 24.

The light reflected by the magneto-optical disk again passes through the objective lens 24, the rising mirror 23, and the collimating lens 22, and is partially diffracted by the hologram 27. The diffracted light is reflected by the beam splitter 26. First
After passing through the reflective surface 26a, the light passes through the right side of the grating 25 and is detected by the photodiode 7 as servo error signal detection light L1.

On the other hand, the light beam not diffracted by the hologram 27 passes through the first reflection surface 26a and the second reflection surface 26b of the beam splitter 26 and passes through the left side of the grating 25, Incident vertically.

Light incident on the prism 10 is coupled to the waveguide element 5 at a predetermined incident angle. Optical waveguide element 5
7 is separated into TE light and TM light by the polarization separation element 11 formed in the element, and then the light is detected by the light detection element 12 as in the configuration shown in FIG. It is detected as the magnetic signal detection light L2.

FIG. 14 is a front view of the optical waveguide device 5, the semiconductor laser 6, and the photodiode 7 shown in FIGS. 12 and 13 as viewed from the light input / output direction (Z-axis direction).

The polarization direction of the laser light emitted from the semiconductor laser 6 in the Z-axis direction in the figure is set parallel to the Y-axis here.

In this case, similarly to the configuration shown in FIGS. 8 to 11, the optical waveguide 17 of the optical waveguide
When disposed at an angle of 45 ° with respect to the axis, the T
The E light and the TM light correspond to polarization components in the direction of ± 45 ° with respect to the polarization direction of the light emitted from the semiconductor laser 6, and a reproduced signal having a high S / N ratio can be obtained.

As described above, in the configuration shown in FIGS. 12 to 14, the beam splitter 26 is located closer to the semiconductor laser 6 than in the configuration shown in FIGS. Therefore, the range through which light passes (the required effective diameter) in the beam splitter 26 can be reduced, and as a result, the reflected light from the magneto-optical disk can be directly transmitted to the optical waveguide element without passing through the microlens 47 as shown in FIG. 5, the size of the entire optical pickup can be reduced.

Furthermore, since the semiconductor laser 6, the optical waveguide element 5, and the photodiode 7 are linearly arranged along the Y axis (see FIG. 14), the X axis becomes the thickness when an optical pickup is formed. There are advantages that the length in the direction can be shortened and the thickness can be reduced.

[0039]

However, FIG.
In the configuration shown in FIG. 14 or FIG. 14, as described above, since the optical waveguide element 5 is disposed obliquely on the block 62, it is difficult to adjust the three-dimensional position of the optical waveguide element 5.

In order to extract the detection output from the light detection element 12 of the optical waveguide element 5, it is necessary to perform electrical wiring. However, as described above, the optical waveguide element 5 is obliquely mounted on the block 62. Due to the leaning, problems such as a complicated process such as wire bonding remain.

An object of the present invention is to provide an optical waveguide unit which is thin and inexpensive, and can easily perform three-dimensional arrangement of optical waveguide elements and connection of electrical wiring, and an optical head using the same. I do.

[0042]

In order to solve the above-mentioned problems, in the optical waveguide unit according to the first aspect of the present invention, light reflected from a light source such as a semiconductor laser and an object to be irradiated is introduced into a package. An optical waveguide element to be detected by a light detection element via a waveguide, and a light reflecting means for coupling reflected light to the optical waveguide of the optical waveguide element are mounted and arranged, and the optical waveguide element is formed by the optical waveguide. The substrate surface is arranged so as to be perpendicular to the optical axis of the reflected light.

Thus, a package including a light source, an optical waveguide element, and the like can be mounted at the lowest height, and light can enter and exit from the side surface of the package. Further, since the optical waveguide element can be arranged in a plane without leaning obliquely, mounting of the optical waveguide element and optical adjustment become easy.

In the optical waveguide unit according to the second aspect of the present invention, in the configuration according to the first aspect, a block in which a wiring pattern for wiring relay is formed is arranged in the package. Features.

As a result, the step between the bonding portion of each element and the wiring pattern formed in the block is reduced, and since the optical waveguide elements are also arranged in a flat plate, wiring in the package becomes easy. .

Further, an optical head according to the third aspect of the present invention is characterized in that the optical waveguide unit according to the first or second aspect is mounted.

Thus, the optical head becomes thin.

[0048]

FIG. 1 is a plan view showing an optical head provided with an optical waveguide unit according to an embodiment of the present invention. Parts corresponding to the prior art shown in FIGS. Assign a sign.

In FIG. 1, reference numeral 1 denotes an optical waveguide unit, 22 denotes a collimating lens, 23 denotes a rising mirror,
Reference numeral 24 denotes an objective lens. 25 is a grating; 26 is a beam splitter; 26a is a first reflecting surface;
Reference numeral 6b denotes a second reflection surface, and 27 denotes a hologram. The configuration and operation thereof are the same as those of the prior art shown in FIG.

The feature of the present invention lies in the configuration of the optical waveguide unit 1. Therefore, in the following, the optical waveguide unit 1
Will be described in more detail.

FIG. 2 is a perspective view showing only the optical waveguide unit constituting the optical head shown in FIG. 1, and FIG. 3 is a front view of the optical waveguide unit shown in FIG. Portions corresponding to the related art shown in FIG. 14 are denoted by the same reference numerals.

The optical waveguide unit 1 includes a package 2
Having. The package 2 is a lead frame type pre-mold type, in which a rectangular frame 20 having one side opened is fixed on a flat base 13, and the lead pins 4 are buried in the frame 20 in an aligned state and integrally formed. The frame 20 is made of resin, and the cap 3 is attached to the frame 20.

The base 13 has a central block 14 protruding substantially at the center thereof. The central block 14 is made of a metal having good thermal conductivity so that the central block 14 can also serve as a heat radiator for the semiconductor laser 6. ing.

The cap 3 is formed of a transparent material such as acryl, and has an L-shaped cross section with a side surface portion 3a located on the opening side of the frame 20 and an upper surface portion 3b arranged orthogonal to the side surface portion 3a. It is bonded and fixed to the frame 20 using an adhesive such as thermosetting or photocuring. A grating 25 is formed on the side surface portion 3a,
It is transparent so that incoming and outgoing light can be transmitted. In addition, the transmittance of light can be improved by applying an anti-reflection coating to the inside or outside of the side surface portion 3a as necessary. Further, the upper surface portion 3b is not necessarily required to be transparent, but is desirably opaque to block external light. Further, when the optical waveguide unit 1 is used alone, the side portion 3a is required for hermetic sealing. However, when the optical component is directly adhered to the opening side of the frame 20, the side portion 3a is not used. It can be omitted.

The above-mentioned lead pin 4 is
An inner end is a wire bonding portion 4a for electrical connection, and an end 4b protruding outward from the frame 20 is electrically connected to a circuit board (not shown) on which the optical waveguide unit 1 is disposed. In order to connect them together, they are bent so as to be at the same height as the bottom surface of the base 13.

Inside the package 2, a semiconductor laser 6, an optical waveguide element 5 for receiving the magneto-optical signal detection light L2,
A photodiode 7 for receiving the servo error signal detection light L1, a photodiode 8 for monitoring the output of the semiconductor laser 6, and a plurality (three in this example) of blocks 9a, 9b and 9c for wiring relay are arranged respectively. I have.

Each of the blocks 9a, 9b, 9c is made of a resin or ceramic base material, and has a wiring pattern 29 formed on a predetermined surface thereof. The bonding surface of each wiring pattern 29 is set to be substantially the same height as the bonding portion 4a of the lead pin 4 in consideration of workability when bonding wires. As a result, it is possible to prevent the wire from being formed on the edges of the blocks 9a, 9b, 9c and the package during wire bonding.

The left and right blocks 9a and 9c are disposed on both sides of the central block 14, and the central block 9b is disposed on the upper surface of the central block 14. The optical waveguide element 5 is fixed on the front surface of the right block 9a. Have been. Also,
A photodiode 8 for monitoring the output of the semiconductor laser 6 is arranged on the front surface of the central block 14.
Is arranged. In this case, the polarization direction of the light emitted from the semiconductor laser 6 is parallel to the Y axis. Block 9 on the left
At the front of c, a photodiode 7 for tracking servo detection is mounted.

As described above, the optical waveguide unit 1 of this embodiment includes the optical waveguide element 5, the semiconductor laser 6, and the photoconductor along the direction (Y-axis direction) orthogonal to the thickness direction (X-axis direction) of the package 2. Since the diodes 7 are arranged in a straight line,
The height of the entire optical waveguide unit 1 can be set low.

FIG. 4 is a plan view showing a state where the optical waveguide element 5 is arranged in the block 9a, and FIG. 5 is a sectional view showing a part of the optical waveguide element 5.

The optical waveguide element 5 has an optical buffer layer 16, an optical waveguide 17, a polarization separation element 11, and a light detection element 12 integrally formed on a silicon substrate 15. As the configuration from the polarization separation element 11 to the light detection element 12, for example, the configuration disclosed in Japanese Patent Application Laid-Open No. 10-78522 can be used. Further, on the silicon substrate 15,
A bonding pad 18 and a marker 19 are formed. The marker 19 gives a reference for dicing when the optical waveguide element 5 is cut into chips from a wafer state.

Further, the optical waveguide 17 of the silicon substrate 15
At the upper position, a prism 10 for coupling light into the same path 17 is arranged. The prism 10 is a so-called reflective coupler prism having a mirror surface M0 formed therein. Since the mirror surface M0 is not contaminated by bonding the prism 10 or other operations, a predetermined reflectance is always ensured. You can do it.

In the optical waveguide element 5 having this configuration, the magneto-optical signal detection light L2 incident on the prism 10 is reflected by the mirror surface M0, is coupled to the optical waveguide 17 at a predetermined angle, and is incident on the optical waveguide 17. The light L <b> 2 undergoes refraction when passing through the polarization separation unit 11 and is separated into TE light and TM light, and each light is detected by the light detection element 12. In this case, the optical buffer layer 16 is gradually thinned in the vicinity of the light detecting element 12, whereby
As light approaches, light starts to leak to the silicon substrate 15 side,
Coupled to photodetector 12. Then, the output of the photodetector 12 is transmitted to the bonding pad 18 and further transmitted to the bonding portion 4a of the lead pin 4 via the wiring pattern 29 of the block 9a. In FIG. 4, wires for electrically connecting the bonding pads 18 and the wiring patterns 29 are omitted.

As described above, in this embodiment, the optical waveguide element 5 is directly mounted on the flat side surface of the block 9a, and the surface 15a of the silicon substrate 15 is perpendicular to the optical axis o of the outgoing and incident light. Since the optical waveguide element 5 is not disposed obliquely leaning as in the prior art shown in FIGS. 12 and 13, the optical waveguide element 5
The arrangement work and the optical adjustment can be performed very easily.

Next, a manufacturing process of the optical waveguide unit of the present invention will be described with reference to FIG.

As shown in FIG. 6A, a central block 14 is mounted near the center of the base 13. The central block 14 can be made by pressing if it is made of metal.

Next, as shown in FIG. 6B, the semiconductor laser 6 and the monitoring photodiode 8 are fixed to the central block 14.

Subsequently, as shown in FIG. 6C, the optical waveguide element 5 to which the prism 10 is fixed in advance is fixed to the block 9a, and wire bonding is further performed. Fix to 13.

Next, as shown in FIG.
Is fixed.

Thereafter, as shown in FIG. 6 (e), the photodiode 7 for servo is fixed to the block 9c and wire bonding is performed. Here, the semiconductor laser 6 and the monitoring photodetector 8 are also subjected to wire bonding.

Thereafter, as shown in FIG. 6F, the frame 20 is bonded, and the bonding portion 4a of the lead pin 4 and the wiring pattern 29 of each of the blocks 9a, 9b, 9c are connected by wire bonding.

Finally, as shown in FIG. 6G, the cap 3 is adhered to the frame 20 to complete the process.

FIG. 7 is a perspective view showing another embodiment of the optical waveguide unit of the present invention, and portions corresponding to those shown in FIG. 1 are denoted by the same reference numerals.

In the optical waveguide unit of this embodiment, the shape and arrangement of the lead pins 4 are different from those shown in FIG.

That is, in the case of FIG.
7 protrudes laterally from the peripheral wall of the frame 20, FIG.
In the case of the embodiment, the lead pins 4 are projected below the base 13, and the lead pins 4 are collectively arranged on one side of the frame 20. According to such a configuration, the outer dimensions of the package 2 can be reduced.

[0076]

According to the present invention, the following effects can be obtained.

(1) According to the first aspect of the present invention, the package including the light source, the optical waveguide element and the like can be mounted at the lowest height, and the optical waveguide unit can be reduced in size and thickness. Further, since the optical waveguide element can be arranged in a plane without leaning obliquely, mounting and optical adjustment of the optical waveguide element are facilitated. (2) In the invention according to claim 2, wiring in the package is easy. Therefore, the cost of manufacturing the optical waveguide unit can be reduced.

(3) According to the third aspect of the present invention, by forming the optical head by mounting the optical waveguide unit, the optical head can be made small and thin, and the manufacturing cost of the optical head can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an optical head including an optical waveguide unit according to an embodiment of the present invention.

FIG. 2 is a perspective view of an optical waveguide unit used in the optical head shown in FIG.

FIG. 3 shows an optical waveguide unit shown in FIG.
(Axial direction)

FIG. 4 is a plan view showing a state where the optical waveguide element is attached to a block with a wiring pattern in the optical waveguide unit of FIG. 2;

FIG. 5 is a sectional view showing an optical waveguide element and a prism used in the optical waveguide unit of FIG. 2;

FIG. 6 is an explanatory view showing a manufacturing process of the optical waveguide unit of the present invention.

FIG. 7 is a perspective view of an optical waveguide unit according to another embodiment of the present invention.

FIG. 8 is a plan view showing an example of a conventional optical pickup for a magneto-optical disk device.

9 is a sectional view showing an optical waveguide element and a prism used in the optical pickup shown in FIG. 8;

FIG. 10 is a plan view showing an optical waveguide element and a prism used in the optical pickup of FIG. 8;

11 is a front view of the semiconductor laser, the optical waveguide element, and the like shown in FIG. 8 as viewed from the light incident / emission direction (Z-axis direction).

FIG. 12 is a plan view showing an example of another conventional optical pickup for a magneto-optical disk device.

FIG. 13 is a plan view showing the optical waveguide element and the prism shown in FIG. 12;

14 is a front view of the semiconductor laser, the optical waveguide device, and the like shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical waveguide unit, 2 ... Package, 5 ... Optical waveguide element, 6 ... Semiconductor laser, 7 ... Photodiode for servo, 8 ... Photodiode for monitor, 9a, 9b, 9
c: block with a wiring pattern, 11: polarization separation element, 12: photodetection element, 15: silicon substrate, 15a ...
Substrate surface, 17: optical waveguide, 22: collimating lens,
23: rising mirror, 24: objective lens, 25: grating, 26: beam splitter, 27: hologram, L1: servo error signal detection light, L2: magneto-optical signal detection light.

Claims (3)

[Claims] 1. A light source such as a semiconductor laser in a package, an optical waveguide element for detecting reflected light from an object to be irradiated by an optical detection element via an optical waveguide, and a light reflected from the optical waveguide of the optical waveguide element. Light reflecting means for coupling light is mounted and arranged, and the optical waveguide element is arranged so that a substrate surface on which the optical waveguide is formed is perpendicular to an optical axis of the reflected light. Characteristic optical waveguide unit. 2. The optical waveguide unit according to claim 1, wherein a block on which a wiring pattern for wiring relay is formed is arranged in the package. 3. An optical head on which the optical waveguide unit according to claim 1 is mounted.