JP2888317B2 - Optical pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for reducing the size of an optical pickup device used for an optical disk device or the like.

[0002]

2. Description of the Related Art In recent years, recording / reproducing apparatuses using a laser beam have become widespread, but there is a problem of miniaturization of an optical pickup device used therein.

Hereinafter, a conventional optical pickup device will be described with reference to the drawings. One of means for reducing the size of an optical pickup device is to reduce the size of an optical system, and various optical pickup devices in which a semiconductor laser element and a photodetector are integrated on a silicon substrate have been proposed. For example, JP-A-64-46243 discloses an optical pickup device shown in FIGS.

FIG. 6 is a sectional view showing the structure of the optical system of the above-mentioned conventional optical pickup device. In the figure, a semiconductor substrate 3
4 and the lower surface 3 of the cover member 33
3a are disposed so as to face each other with a space therebetween, and a first light detection unit 35 and a second light detection unit 36 are formed on an upper surface 34a of the semiconductor substrate 34. Are formed with a semiconductor laser element 37 and a monitoring light detection section 38. Top 34b is formed a step to be lower to the upper surface 34a, the total reflection grating portion stepped surface faces the laser light beam L ₁ emitted from the semiconductor laser element 37 (hereinafter, referred to as a reflection mirror) 40 Make up. Upper surface 34a of semiconductor substrate 34
Is precisely processed by, for example, an etching process. Further, a beam splitter 41 formed by a hologram element is provided on the upper surface 33b of the cover member 33.

The operation of the above configuration will be described. The laser light beam L ₁ emitted from the semiconductor laser element 37 will be described.
But by the reflection mirror 40 provided on the upper surface 34a of the semiconductor substrate 34 is divided into three laser light beams L ₂ of, it is reflected upward. They three laser beam L ₂ of respectively incident from the lower surface 33a of the cover member 33, enters the beam splitter 41 provided on the upper surface 33b of the cover member 33 after passing through the cover member 33. A part of the laser light beam L ₂ that has reached the beam splitter 41 passes through the cover member 33 as a laser light beam L ₃ ,
Emitted from 3a. The emitted laser light beam L ₃ is the first
And a part of the light is detected by the first light detection unit 3.
5 and the lower surface 33a of the cover member 33, and is incident on the second light detection unit 36.

FIG. 7 is a sectional view showing the structure of another conventional optical pickup device. This optical pickup device uses a prism 50 instead of the reflection mirror 40 in the optical pickup device shown in FIG.

Hereinafter, the light source used in the optical pickup device will be described. As a light source of the optical pickup device, a gallium aluminum arsenide (hereinafter, referred to as GaAlAs) -based double heterostructure laser epitaxially grown on a gallium arsenide (hereinafter, referred to as GaAs) substrate is generally used. FIG. 8 is a perspective view showing the configuration. In the figure, 81 is gallium aluminum arsenide (G
a _1-x Al _x As), and the oscillation wavelength can be selected in the range of 680 to 880 nm depending on the composition ratio of aluminum. For example, a wavelength of 780 nm is used for compact disks and video disks, and a wavelength of 830 nm or 780 nm is used for high power lasers for optical disks. Reference numerals 82a and 82b _denote cladding layers made of gallium aluminum arsenide (Ga _1-y Al _y As), which serve to confine carriers (electrons and holes) and light in the active layer 81. 83 is Ga
This is a cap layer made of As and provided to reduce electrode resistance.

The normal size of the laser chip, which is an aggregate of the above layers, is about 0.25 × 0.3 × 0.12 mm, which is very small. A pn junction is formed in the active layer 81. Electrons and holes are injected into the active layer 81 by applying a voltage with the p electrode 84 positive and the n electrode 85 negative, and laser oscillation occurs at a certain current value. . Laser chips are usually
With the growth layer side down, it is mounted via a brazing material 87 on a submount 88 made of silicon or the like on a copper block 86. The reflecting mirror 89 necessary for constructing the laser resonator is made using a cleavage plane of the crystal.

FIG. 9 is an enlarged sectional view showing the vicinity of the semiconductor laser element 37 and the reflection mirror 40 in the optical pickup device shown in FIG. In the semiconductor laser element 37, the height Z ₁ until the end face of the active layer 81 and the Kyatsupu layer 83 side with a light-emitting point is usually about 10μm and smaller, the height Z ₁ precision because it is created by epitaxial growth is high, ±
It can be about 1 μm or less. On the other hand, the active layer 81 and GaAs
The height Z ₂ up to the end face on the substrate 80 side is as large as about 100 μm, and its accuracy depends on the thickness accuracy of the GaAs substrate 80. Since the GaAs substrate 80 is processed by polishing or etching the wafer, the thickness accuracy is an order of ± 10 [mu] m, a very high number in comparison with the height Z ₁ accuracy.

The step portion of the silicon semiconductor substrate 34 is processed by etching the upper surface 34a. It is desirable that the etching depth (H ₁ + H ₂ ) be as small as possible in order to shorten the etching time and ensure processing accuracy. However, the outgoing light L ₁ of the semiconductor laser element 37 NA (Numeric
al Aperture) to increase the depth (H ₁ + H
₂ ) needs to be about twice the height of the semiconductor laser element 37, that is, about 200 μm, which is a very large value. In order to increase the NA value while reducing the depth of the etching, as small as possible the distance X ₁ between the light emitting point of the semiconductor laser element 37 and the reflection mirror 40.

[0011]

In such a conventional optical pickup device, in a configuration in which a semiconductor laser device and a photodetector are provided on a semiconductor substrate, return light from the optical disk is divided by a hologram device or the like. When the light is incident on a photodetector and a focusing error signal is detected by, for example, a beam size method, it is necessary to configure one of the two photodetectors so as to receive light before the focus and receive the other light after the focus. In the conventional configuration in which the photodetectors are arranged in parallel with the hologram element, since the distance between the hologram element and the two photodetectors is the same, the division position of the hologram element is operated to set the focal position. A shifting configuration is required. In order to do so, a special hologram element must be created that matches the configuration.

Further, in order to increase the NA value, FIG.
0, the distance X between the light emitting point and the reflecting mirror 40
₁ may be reduced, but if it is too small, the height Z _{2 of the} semiconductor laser device 37 on the GaAs substrate side is large, so that the outgoing light is emitted from the portion 37 d of the emission end face of the semiconductor laser device 37.
Blocked, since the utilization efficiency of light is reduced, to reduce the distance X ₁ there is a limit.

Further, as shown in FIG. 11, in a configuration in which the semiconductor laser device 37 is fixed to the semiconductor substrate 34 on the GaAs substrate side in order to increase the NA value, light is blocked by the semiconductor laser device 37. Is less. In this case, the dimensional accuracy of the Z ₂ of the semiconductor laser element 37 is high-precision light emitting points can not be obtained because worse than the Z _1, of the light spot on the photodetector 35 and the photodetector 36 in FIG. 6 size Is inconvenient to change. Further, it is necessary to increase the height H ₁ of the upper surface 34a, can not be processed by etching, also, there is a problem that it is difficult to process deeply.

Further, in the configuration shown in FIG. 7, NA value since the prism 50 can be easily increased can increase, but poor dimensional accuracy of Z _2, also attach the accuracy of the prism is poor, further, the substrate 34 Since the prism 50 and the prism 50 are separate parts, there is a problem that it is difficult to manufacture.

SUMMARY OF THE INVENTION The object of the present invention is to provide an optical pickup device which can be manufactured with high accuracy while reducing the size and can increase the NA value.

[0016]

In order to achieve the above object, the present invention provides a semiconductor laser device mounted on a semiconductor substrate and emitting a laser beam, and a predetermined height formed by processing the semiconductor substrate. A stepped surface having an inclined surface as a reflection surface, a reflection mirror that reflects light emitted from the semiconductor laser element, a plurality of photodetectors provided on the semiconductor substrate, and a recording medium that reflects the laser light reflected by the reflection mirror. In an optical pickup device including an objective lens that converges light on a surface and a hologram element that splits return light from the recording medium surface and enters the predetermined photodetector, an emission end face of the semiconductor laser element is The laser light reflected by the reflection mirror is reduced by half by arranging it so as to be close to the reflection mirror and the emission optical axis intersects a vertical plane common to the semiconductor substrate and the reflection mirror. The surface on the epitaxial growth layer side of the semiconductor laser element is fixed on the semiconductor substrate so as not to hit the emission end face of the body laser element, and the laser light reflected by the reflection mirror is incident almost perpendicularly on the hologram element. An optical pickup device in which the semiconductor substrate is arranged to be inclined with respect to the hologram element.

[0017]

According to the present invention, in the above structure, the reflected light of the outgoing light having an optical axis which does not include a vertical plane common to the semiconductor substrate and the reflecting mirror is arranged such that the emitting end face of the semiconductor laser element is located close to the reflecting mirror. However, the light is reflected in a direction that does not impinge on the emission end face.

[0018]

【Example】

Embodiment 1 Hereinafter, an optical pickup device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side sectional view showing a configuration of an optical pickup device according to an embodiment of the present invention. First, the positional relationship between the semiconductor substrate 1 and the semiconductor laser element 2 in the optical pickup device of the present invention will be described. FIG. 2A is a partial top view showing the semiconductor laser element and its vicinity in the optical pickup device of the present embodiment, and FIG. 2B is a sectional side view thereof. In the figure, 1
Is a semiconductor substrate, 1a is a surface thereof, 1b is a bottom portion of a concave portion having a predetermined depth formed by etching the semiconductor substrate 1, 2 is a semiconductor laser device, and 3 is an inclined flat step surface in the concave portion. It is a configured reflection mirror. As shown in FIG. 2A, the semiconductor laser element 2 is fixed by attaching the surface on the growth layer side to the bottom 1b, and has a ridge line parallel to the bottom surface of the emission end face of the semiconductor laser element 2. By mounting the semiconductor laser device 2 at an angle with respect to the intersection line 1c between the surface of the bottom portion 1b and the reflection mirror 3, the optical axis of the light emitted from the semiconductor laser element 2 intersects a vertical plane common to the reflection mirror 3 and the semiconductor substrate 1. Placed in With this setting, the reflected light 10 is reflected so as to move away from the emission end face of the semiconductor laser element 2, and even if the distance between the light emitting point of the semiconductor laser element 2 and the reflection mirror is reduced, the reflected light is generated at the end face of the semiconductor laser element 2. Therefore, the angle of incidence of the laser beam on the reflection mirror 3 can be increased to increase the NA value.

Next, the operation of the optical pickup device according to the embodiment of the present invention will be described. In FIG. 1, the reflected light 10
Is emitted obliquely to the semiconductor substrate 1, the semiconductor substrate 1 is tilted, and the setting is made so that the reflected light 10 is perpendicularly incident on the optical disk 11. The two-divided photodetectors 5 and 2 are arranged on the upper surface of the semiconductor substrate 1 so as to sandwich the reflection center on the reflection mirror 3 in the track direction (hereinafter referred to as the X direction).
A split photodetector 6 is disposed, and the reflection mirror 3 is arranged in a radial direction (hereinafter, referred to as a Y direction) of the optical disk 11.
The three-segment photodetector 7 and the three-segment photodetector 8 are arranged so as to sandwich the upper reflection center. Further, of the surfaces of the glass block 12 facing in parallel with each other, the reflection mirror 3
Hologram (hereinafter referred to as HOE) on the surface facing
An element HOE ₁ 13 is formed, and HOE ₂ is formed on the other surface.
14 are formed. Here, the two split photodetectors 5 and 2
Each of the divided photodetectors 6 is divided into two by a dividing line in the X direction.
The three-divided photodetector 7 and the three-divided photodetector 8 respectively constitute three light-receiving regions divided by a dividing line in the Y direction.

In the above configuration, the laser light 9 emitted from the semiconductor laser element 2 is reflected by the reflecting mirror 3, the reflected light 10 passes through the HOE ₁ 13 and the HOE ₂ 14, and the zero-order light is passed through the objective lens 17. The light is focused on the optical disk 11. The return light from the optical disk 11 passes through the objective lens 17, enters the HOE ₁ 13 and is diffracted in the X direction.
The primary light is received by the split photodetector 5 and the split photodetector 6. A tracking error signal and an information signal are extracted from the output signals of the split photodetector 5 and the split photodetector 6 by the push-pull method. The ± first-order light diffracted in the Y direction by the HOE ₂ 14 is received by the three-segment photodetector 7 and the three-segment photodetector 8, and a focusing error signal is extracted from the output signal by the beam size method.

That is, assuming that the photoelectric outputs of the light receiving elements 5A, 5B, 6A, 6B of the split photodetector 5 and the split photodetector 6 are T _5A , T _5B , T _6A , and T _6B , respectively, the tracking error The signal can be obtained by the calculation of ( _T5A - _T5B ) + ( _T6A - _T6B ).

The three-segment photodetector 7 and the three-segment photodetector
Each of the eight light receiving elements 7A, 7B, 7C and 8A, 8B, 8C
And their outputs are F_7A, F_7B, F_7CWhen
F_8A, F _8B, F_8CThen the focusing error signal
Is (F_7B+ F_7C-F_7A)-(F_8B+ F_8C-F_8A) Can be obtained by the following calculation.

As described above, according to this embodiment, the emission optical axis intersects the vertical plane common to the semiconductor substrate and the reflection mirror by inclining the emission end surface ridge of the semiconductor laser element with respect to the reflection mirror ridge. In addition, by arranging the distance between the light emitting point and the reflecting mirror small, the NA value can be increased without the reflected light being blocked by the end face of the semiconductor laser device.

Further, according to the present embodiment, even if the power of division of the HOE ₂ 14 for division for obtaining a focusing error signal is equalized, the distance between the HOE ₂ 14 and the three-divided photodetector 7 can be reduced. Since the distance between the HOE ₂ 14 and the three-segment photodetector 8 is different, the light incident on the three-segment photodetector 7 and the three-segment photodetector 8 can be focused back and forth.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3A is a partial top view showing the semiconductor laser element and its vicinity in the optical pickup device of the present embodiment, and FIG. 3B is a sectional side view thereof. In the figure, the same components as those in the embodiment of FIG. This embodiment is different from the first embodiment in that the secondary cleavage of the semiconductor laser element 2 is not uniform but largely deviated with respect to the laser light emitting portion, and the laser light 9 is near the end of the semiconductor laser element 2. Out of the device. Therefore, since the light emitting point can be set closer to the reflecting mirror 3 than in the case of the first embodiment, even if the NA value is increased, the area of the reflecting surface can be reduced, and the depth of the reflecting mirror processed by etching can be reduced. It is shallower and easier to manufacture.

As described above, according to the present embodiment, the secondary cleavage of the semiconductor laser element 2 is not uniformly and largely deviated with respect to the laser light emitting portion, and the laser light 9 is irradiated near the end of the semiconductor laser element 2. And the ridge line of the emitting end face of the semiconductor laser element is inclined with respect to the ridge line of the reflecting surface so that the optical axis of the emitted light intersects the common vertical plane between the semiconductor surface and the reflecting surface, and By setting the distance between the point and the reflecting mirror small, the NA value can be increased.

Embodiment 3 Hereinafter, an optical pickup device according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a partial top view showing the configuration of the optical pickup device of this embodiment. In FIG. 4, 1 is a semiconductor substrate, 2
Denotes a semiconductor laser element, 3 denotes a reflection mirror constituted by a flat inclined surface of a polygonal concave portion formed by etching the upper surface of the semiconductor substrate 1, and the semiconductor laser element 2 has the same structure as in the first embodiment. By arranging the emission end face ridge line so as to be inclined with respect to the reflection mirror ridge, the reflected laser light 9 is set so as not to interfere with the semiconductor laser element 2. Reference numeral 12 denotes a step provided on the surface of the reflection mirror 3, and only the reflection surface on which the laser light 9 is irradiated is arranged close to the emission end face of the semiconductor laser element, and even if the NA value is increased, the area of the reflection surface is increased. Can be reduced, and the depth of the etching process of the reflection mirror 3 can be reduced, so that the fabrication becomes easy.

Reference numeral 4 denotes a rear monitor photodetector for monitoring the output power of the laser beam 9, 5 and 6 denote two-split photodetectors, and 7 and 8 denote three-split photodetectors. The position of the rear monitor photodetector 4 is divided into two split photodetectors 5 and 6, 3
Since the photodetectors 7 and 8 can be set at positions where they do not interfere with the laser light, the photodetectors can be arranged closer to the concave portions, and the size can be reduced. Further, there is no other photodetector behind the rear monitor photodetector 4, and the rear emission light of the semiconductor laser element 2 does not enter the photodetectors other than the rear monitor photodetector 4, so that the offset or the like is reduced. Will not occur. Further, the direction of the reflected light from the rear monitoring photodetector 4 is shifted by about 90 degrees from the direction of the reflected light 10 from the reflecting mirror 3, so that the backward emitted light from the semiconductor laser element 2 can be prevented from entering the objective lens or the like. .

FIGS. 5A and 5B are top views showing an embodiment in which the semiconductor laser element 2 is mounted obliquely with respect to the reflection mirror 3. FIG.

FIG. 5A shows a bottom surface 1b of a polygonal concave portion having a plurality of step surfaces obtained by processing the semiconductor substrate 1 by etching.
In the same manner as in the first embodiment, when the ridge line of the output end face of the semiconductor laser device 2 is arranged to be oblique to the ridge line of the reflection mirror, the squares 2a, 2b, 2
When the semiconductor laser device 2 is mounted on the bottom surface of the concave portion, the squares 2a, 2b, 2c, 2d, and 4c are set so that c and 2d are substantially located at the ridge line portion of the step surface.
If the gaps La, Lb, Lc, and Ld between the two step surfaces are arranged so as to be uniform, mounting can be easily performed at a predetermined position and angle.

FIG. 5B shows a semiconductor laser when the semiconductor substrate 1 is formed with a recess by etching and the semiconductor laser element 2 is arranged such that the ridge line of the emission end face is oblique to the ridge line of the reflection mirror 3. Squares 2a, 2b, 2 of element 2
Corners Sa, Sb, Sc, Sd are provided at portions facing c and 2d.
Is provided. When mounting the semiconductor laser device 2, if the corners Sa, Sb, Sc, and Sd are arranged so that the squares 2a, 2b, 2c, and 2d of the semiconductor laser device 2 coincide with each other, the desired position and angle can be easily obtained. Can be mounted.

As described above, according to the optical pickup device of the embodiment of the present invention, it is possible to easily mount the semiconductor laser element 2 obliquely and accurately on the reflection mirror 3.

[0033]

As is apparent from the above embodiments, the present invention is directed to a semiconductor laser device mounted on a semiconductor substrate and emitting a laser beam, and a tilt having a predetermined height formed by processing the semiconductor substrate. The stepped surface as a reflection surface, a reflection mirror for reflecting the emitted light of the semiconductor laser element, a plurality of photodetectors provided on the semiconductor substrate, and the laser light reflected by the reflection mirror on a recording medium surface. An objective lens for focusing,
A hologram element for splitting return light from the recording medium surface and making the split light incident on the predetermined photodetector, wherein an emission end face of the semiconductor laser element is brought close to the reflection mirror and an emission optical axis is adjusted. Are arranged so as to intersect a vertical plane common to the semiconductor substrate and the reflection mirror, so that the laser light reflected by the reflection mirror does not hit the emission end face of the semiconductor laser element. A layer-side surface is fixed on the semiconductor substrate, and the semiconductor substrate is inclined with respect to the hologram element such that laser light reflected by the reflection mirror is incident on the hologram element almost perpendicularly. Specially change the split power at the hologram element to obtain the focusing error signal. Also, since the distance between the dividing element are different, can be a proper placement, also eliminates interference with a portion of the laser beam and the semiconductor laser element, a sufficient NA value can be secured.

In addition, by arranging a configuration in which the portion of the reflection mirror on the side of the semiconductor laser element not irradiated with the laser beam is made to escape, the semiconductor laser element and the reflection mirror can be brought closer to each other. The mirrors need only be shallow, making them easier to manufacture. Further, the emission point of the semiconductor laser device is offset closer to the reflection mirror surface than the center when viewed from directly above the semiconductor laser device, so that the emission point of the semiconductor laser device can be closer to the reflection mirror. It becomes possible, and the same effect as above can be obtained. Further, by providing the positioning mark of the semiconductor laser device on the semiconductor substrate by etching, it becomes very easy to position the semiconductor laser device obliquely when mounting the semiconductor laser device. In addition, since it is manufactured at the same time as the reflecting mirror surface by etching, the manufacturing of the positioning mark is easy and the accuracy can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view showing a configuration of an optical pickup device according to an embodiment of the present invention.

FIG. 2A is a partial top view showing a positional relationship between a semiconductor laser device and a reflection mirror in the first embodiment of the present invention; FIG.

FIG. 3 (a) is a partial top view showing a positional relationship near a semiconductor laser device and a reflecting mirror in a second embodiment of the present invention.

FIG. 4 is a top view showing a positional relationship among a semiconductor laser device, a reflection mirror, and a photodetector on a semiconductor substrate according to a third embodiment of the present invention.

FIG. 5A is a top view showing another positional relationship near the semiconductor laser device and the reflection mirror according to the third embodiment of the present invention. FIG. 5B is a top view of the modification.

FIG. 6 is a cross-sectional view showing a configuration example of a conventional optical pickup device.

FIG. 7 is a sectional view showing another configuration example of a conventional optical pickup device.

FIG. 8 is a perspective view showing a configuration near a semiconductor laser element and a reflection mirror in a conventional optical pickup device.

FIG. 9 is an enlarged sectional view showing the vicinity of a semiconductor laser element and a reflection mirror used in an optical pickup device;

FIG. 10 is a partial sectional view showing a positional relationship between a semiconductor laser element and a reflection mirror in a conventional optical pickup device.

FIG. 11 is a partial cross-sectional view showing a positional relationship between a semiconductor laser element and a reflection mirror in a conventional optical pickup device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor substrate 2 semiconductor laser element 3 reflection mirror 5 two-segment photodetector 6 two-segment photodetector 8 three-segment photodetector 9 outgoing light 10 reflected light 11 optical disk 13 hologram element 14 hologram element 17 objective lens

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor ▲ Yoshi ▼ Akio Kawa 1006 Kadoma, Kadoma City, Osaka Inside Matsushita Electronics Corporation (56) References JP 4-216328 (JP, A) JP Hei 4-139628 (JP, A) JP-A-64-46243 (JP, A) JP-A-61-168663 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 7 / 135 G11B 7/125

Claims (4)

(57) [Claims] A semiconductor laser device mounted on a semiconductor substrate and emitting a laser beam; and a stepped surface having a predetermined height formed by processing the semiconductor substrate as a reflection surface. A reflection mirror that reflects light emitted from the element, a plurality of photodetectors provided on the semiconductor substrate, an objective lens that focuses laser light reflected by the reflection mirror on a recording medium surface, and the recording medium A hologram element for splitting the return light from the surface and making the light incident on the predetermined photodetector, wherein the emission end face of the semiconductor laser element is brought close to the reflection mirror and the emission optical axis is the semiconductor. The laser light reflected by the reflection mirror is arranged so as to intersect with a vertical plane common to the substrate and the reflection mirror so that the laser light does not hit the emission end face of the semiconductor laser device. A surface of the semiconductor laser element on the side of the epitaxial growth layer is fixed on the semiconductor substrate, and the semiconductor substrate is moved relative to the hologram element such that the laser beam reflected by the reflection mirror is substantially perpendicularly incident on the hologram element. An optical pickup device arranged at an angle. 2. The optical pickup device according to claim 1, wherein a portion of the reflection mirror which is not irradiated with the laser beam, and a portion near the semiconductor laser element is removed so as to be away from the semiconductor laser element. 3. The optical pickup device according to claim 1, wherein a semiconductor laser element is used in which an emission position of the laser beam is closer to a position closer to the reflection surface of the reflection mirror than a center of the emission end face. 4. The optical pickup device according to claim 1, wherein a part of the step surface forms a step for positioning when the semiconductor laser device is fixed on the semiconductor substrate.