JPH10321961A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow lights emitted from a plurality of laser chips to travel along one and the same axis, by holding, in one laser package, a plurality of laser chips emitting laser lights of different wavelengths and an optical element for adjusting an optical axis, in order to allow transmitted laser light and reflected laser light to travel along one and the same axis. SOLUTION: Laser light emitted from a laser chip 2 preliminarily positioned together with a sub mount 4b and reflected by a wavelength selective optical element 3 is outputted as parallel light through an optical lens or other device. With the parallel light being monitored, light is emitted from another laser chip 1 with the sub mount 4b including the laser chip 2 being moved to make the light emitted from the laser chip 1 into parallel light. The parallel light emitted from the laser chip 1 is aligned with the parallel light preliminarily emitted from the laser chip 2. By this method, the deviation of optical light emitting points between the laser chips 1, 2 can be eliminated, and laser lights emitted from the two laser chips can travel along one and the same optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used as a light source for an optical pickup used in a high-density optical recording / reproducing apparatus such as a digital video disk and a light source having a light receiving element for signal detection. It is about.

[0002]

2. Description of the Related Art In the prior art, a semiconductor laser device used as a light source of an optical pickup used in an optical recording / reproducing device and the like, in which a single laser chip is mounted, has been put into practical use. . Therefore, a single-wavelength laser beam is emitted from one semiconductor laser device (here, “single-wavelength” used means a wavelength determined by a band gap of a crystal constituting a laser chip). However, both the single mode related to the longitudinal mode during oscillation and the multimode in the self-pulsation type laser are included in “single wavelength”.)

A typical example is shown in FIG. this is,
FIG. 2 is a perspective view illustrating a whole structure of a conventional semiconductor laser device with a part thereof cut away. A laser chip 100 that emits a single-wavelength laser beam is provided on an element mounting block 101 a on a stem 101. The laser light of a single wavelength emitted from the laser chip 100 travels in a direction perpendicular to the reference surface 101b provided on the stem 101, and is emitted from an emission window 102 provided on an upper part of the semiconductor laser device. Also,
A light receiving element 100c for monitoring the optical output is provided behind the laser chip 100. Arrow C indicates laser chip 10
It shows how laser light emitted from 0 is emitted. These components are covered with a cap 103 having an emission window 102 and constitute a semiconductor laser device housed in one package. Reference numeral 104 denotes a lead terminal.

[0004] Other conventional examples include: A multi-beam semiconductor laser in which a plurality of laser chips are monolithically integrated is disclosed in JP-A-3-187285. Japanese Patent Application Laid-Open No. 3-112184 discloses a semiconductor laser device in which three semiconductor lasers are integrated in a hybrid manner on a submount by shifting their light emitting point positions. 3. In addition, Japanese Patent Laid-Open No. 6-35 discloses a light-emitting / receiving element capable of three-dimensionally arranging light-emitting points of a plurality of semiconductor lasers.
No. 0187.

[0005] One of these representative examples is disclosed in Japanese Patent Laid-Open Publication No.
FIG. 34 shows a conventional example disclosed in Japanese Patent Publication No. 350187. FIG. 34 shows that the light receiving element 112 is provided on the semiconductor substrate 111.
a, 112b and a recess 113 are formed.
Are provided with laser chips 115 and 116.
The laser chips 115 and 116 are lasers having different wavelengths from each other, and the light emitted from the laser chips 115 and 116 in the horizontal direction (the direction from the bottom to the top of the page) is reflected by the inclined surface of the micro mirror 114, respectively.
The light is emitted in a direction perpendicular to the semiconductor substrate 111 (a direction penetrating from the back side of the paper to the front side).

An optical pickup device in which a laser chip and a light receiving element for receiving light reflected from an optical recording medium are housed in the same package and which has a diffraction element for diffracting the pre-reflected light is disclosed in Japanese Patent Publication No. 5-9851. No. 6,086,045. FIG. 35 is a perspective view, partially cut away, showing an example of a semiconductor laser device as an example in which the present optical pickup device is integrated.

In FIG. 1, a laser chip 120 for emitting a laser beam of a single wavelength is mounted on an element mounting block 121 a on a stem 121. The laser light of a single wavelength emitted from the laser chip 120 travels in a direction perpendicular to the reference plane 121b provided on the stem 121, and is emitted from the diffraction element 125 provided on the upper part of the semiconductor laser device. A light receiving element 123 for receiving light reflected from the optical recording medium is provided in the element attaching block 121a. Behind the laser chip 120, a light receiving element 120c for monitoring an optical output
Is installed. Light reflected from the optical recording medium is diffracted by the diffraction element 125 in the direction of the light receiving element 123. 1
26 indicates a lead terminal. Arrow C indicates laser chip 1
20 shows a state in which the laser light emitted from 20 is emitted from the diffraction element 125 provided on the upper part of the semiconductor laser device, further reflected by the optical recording medium, and returned to the semiconductor laser device;
An arrow D indicates how the light diffracted by the diffraction element 125 is received by the light receiving element 123.

[0008] Conventionally, optical recording media such as CDs (compact disks), video disks, and magneto-optical disks have all used substrates with a thickness of 1.2 mm. On the other hand, in recent years, a technique for increasing the numerical aperture of an objective lens that focuses laser light from a semiconductor laser on an optical recording medium has been introduced in order to achieve higher density. Increasing the aperture of the objective lens improves the optical resolution and is an effective means for high-density optical recording. However, there is a problem in that the convergence performance of a condensed spot is reduced.

That is, in the case of the above-mentioned optical recording medium using a substrate having a thickness of 1.2 mm, coma aberration occurs in the light spot due to the surface runout and the inclination of the objective lens induced by the surface runout of the turntable on which it is mounted. However, it is not possible to obtain a high quality recording / reproducing signal. Therefore, a method using an optical recording medium having a thin substrate is adopted so that the coma of the light spot does not increase even if the numerical aperture of the objective lens is increased.

For example, a DVD (Digital Video Disk) device, which is expected to rapidly spread as a high-density optical recording device in the future, uses a 0.6 mm-thick substrate optical recording medium for the above-described reason. However, an objective lens optimized for recording / reproducing an optical recording medium having a thin substrate has a large spherical aberration with respect to a conventionally used optical recording medium having a thickness of 1.2 mm. There is a problem that recording / reproduction becomes difficult.

Therefore, in order to maintain compatibility with a conventional optical recording medium, an objective lens optimized for an optical recording medium having a different substrate thickness is prepared independently. Alternatively, Japanese Patent Laid-Open No. 7-
No. 182,690 discloses that the focusing state of the objective lens is converted between an objective lens and a semiconductor laser device optimized for an optical recording medium having a thickness of 0.6 mm on a substrate, and that
There is disclosed an example in which a conversion lens for suppressing the occurrence of spherical aberration is provided for an optical recording medium having a thickness of m for a substrate, and the conversion lens is taken in and out according to a difference in the thickness of the substrate.

FIG. 36 shows an example of the present disclosure. In the figure, 131 is a semiconductor laser device, 132 is the semiconductor laser device 13
An objective lens 133 for converging the laser light emitted from the optical disc 1 on the recording surface of the optical recording medium 140, a collimating lens 133 for converting divergent light emitted from the semiconductor laser device 131 into a substantially parallel light beam, and 134 A detection optical system 135 for detecting a laser beam reflected by the optical recording medium 140; a beam splitter 135 for splitting the reflected light from the optical recording medium 140 to the detection optical system 134;
A conversion lens 136 is provided between the objective lens 132 and the beam splitter 135, and is a concave lens for converting the state of light convergence toward the objective lens 132. 137 is a photodetector. FIG.
(A), (b) is a diagram showing the convergence state of the optical recording medium and the optical spot, where 140a is an optical recording medium having a 0.6 mm thick substrate, and 140b is an optical recording medium having a 1.2 mm thick substrate.

[0013]

On the other hand, when recording / reproducing different types of optical recording media which require recording / reproducing using laser beams of different wavelengths as light sources, a single optical recording / reproducing apparatus requires different recording / reproducing. It is necessary to mount a separate semiconductor laser device that emits laser light of a wavelength on an optical pickup and incorporate it into an optical recording / reproducing device, and switch the driving of the semiconductor laser device according to the wavelength required by the optical recording medium. That is, a plurality of semiconductor laser devices having different wavelengths are mounted.

As a specific example, when recording / reproducing the optical recording medium for DVD and the optical recording medium for CD-R described above, the wavelength used differs depending on the material of the optical recording medium. The optical recording medium for DVD has a wavelength of 625 to 660 nm (center wavelength of 650 nm or 635 nm), and the optical recording medium for CD-R has a wavelength of 780 to 790 nm (the center wavelength is slightly different depending on the material, but is about 785 nm). ) Required a semiconductor laser of a certain wavelength. As described above, when the conventional semiconductor laser device is used, at least the semiconductor laser devices having different wavelengths are independently mounted, so that the number of components increases, the device becomes large, and the price is affected. There was a problem.

The conventional examples disclosed in JP-A-3-187285 and JP-A-3-112184 are examples in which independent laser chips are arranged in the horizontal direction. Distance parallel to the width of the laser chip in a direction parallel to
The interval between the light emitting points is increased by about 00 μm. JP 6
A similar problem occurs in the conventional example disclosed in Japanese Patent Application Laid-Open No. 350350/350. As described above, when the interval between the light emitting points is widened, problems such as aberration of the lens occur, and it becomes particularly difficult to use the high density optical recording system.

In a conventional example disclosed in Japanese Patent Publication No. 5-9851, an optical pickup device in which one laser chip and a light receiving element designed according to the wavelength of the laser chip are housed in the same package is used. When recording / reproducing a heterogeneous optical recording medium which is an integrated semiconductor laser device and requires recording / reproducing using laser beams of different wavelengths as light sources with one optical recording / reproducing device,
It was necessary to independently mount semiconductor laser devices in which laser chips of different wavelengths and separate optical pickup devices each mounting one light receiving element optimized according to them were integrated.

In the conventional example disclosed in Japanese Patent Application Laid-Open No. 7-182690, an objective lens optimized for an optical recording medium having a thickness of 0.6 mm and a semiconductor laser device are disposed between the objective lens and the semiconductor laser device. The point that a conversion lens is provided for converting the focusing state and suppressing the occurrence of spherical aberration even for an optical recording medium having a substrate thickness of 1.2 mm, and a mechanism for taking the conversion lens in and out according to the difference in the thickness of the substrate. From the need for parts,
There have been problems such as an increase in the number of parts, an increase in the size of the apparatus, and an increase in cost.

In summary, when recording / reproducing different types of optical recording media that require recording / reproducing using laser beams of different wavelengths as light sources in the prior art with one optical recording / reproducing apparatus, Since laser chips of different wavelengths or laser chips of different wavelengths and light-receiving elements optimized for them are mounted one by one, separately integrated semiconductor laser devices will be mounted independently. There were first problems such as an increase in the number of points, an increase in the size of the apparatus, and an increase in cost.

Further, in a semiconductor laser device in which a plurality of laser chips are integrated, there is a second problem that a problem such as lens aberration occurs due to an increase in intervals between light emitting points.

Further, when recording / reproducing is performed on an optical recording medium having a different substrate thickness, a conversion lens for suppressing the occurrence of spherical aberration is provided, and the conversion lens is moved in and out according to the difference in substrate thickness. The need for a mechanical part
There were third problems, such as an increase in the number of parts, an increase in the size of the device, and an increase in cost.

[0021]

According to a first aspect of the present invention, a plurality of laser chips for emitting laser beams of different wavelengths, and the transmitted laser beam and the reflected laser beam are made identical by transmission and reflection of the laser beam. An optical element for adjusting an optical axis for emitting light on an optical axis is provided in a single laser package.

According to a second aspect of the present invention, a plurality of laser chips for emitting laser beams having different wavelengths, and the transmitted laser beam and the reflected laser beam are emitted on the same optical axis by transmitting and reflecting the laser beam. An optical element for adjusting the optical axis, and a light receiving element for receiving the reflected light from the optical recording medium in one laser package, and the laser package reflects the reflected light from the optical recording medium into a predetermined wavefront. And a diffractive element for diffracting the light in the direction of the light-receiving element, wherein the light-receiving element includes light-receiving portions for respectively receiving reflected light according to different wavelengths.

According to a third aspect of the present invention, there is provided the semiconductor laser device according to the second aspect, wherein each of the light receiving elements has an independent light receiving section optimized according to a wavelength.

According to a fourth aspect of the present invention, there is provided the semiconductor laser device according to the second or third aspect, wherein each of the light receiving portions has its light receiving surface set at a different height in the optical axis direction. .

According to a fifth aspect of the present invention, there is provided the semiconductor laser device according to any one of the second to fourth aspects, wherein a light receiving surface of the light receiving element is provided to be inclined.

According to a sixth aspect of the present invention, the optical element for adjusting the optical axis is any one of a wavelength-selective optical element, a non-polarizing beam splitter, and a polarizing beam splitter. 6. The semiconductor laser device according to any one of 5.

According to a seventh aspect of the present invention, the plurality of laser chips and the optical element for adjusting the optical axis are provided via an L-shaped block. 2. The semiconductor laser device according to item 1.

According to an eighth aspect of the present invention, there is provided an optical path between one of a plurality of laser chips and the optical element for adjusting the optical axis.
8. The semiconductor laser device according to claim 1, further comprising a wavefront converting means for converting a wavefront of the laser light.

According to a ninth aspect of the present invention, there is provided an optical path between one of a plurality of laser chips and the optical element for adjusting the optical axis.
8. The semiconductor laser device according to claim 1, further comprising an aperture limiting means for limiting an aperture of the laser beam.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, two laser chips having different wavelengths are provided in a package of one semiconductor laser device.
By incorporating one, a semiconductor laser device emits a laser beam having a wavelength required by an optical recording medium for recording / reproducing. However, due to the transmission and reflection of laser light using optical elements such as wavelength-selective optical elements, beam splitters, and polarization splitters, the positional relationship in which the transmitted light and the reflected light are emitted from the semiconductor laser device to pass on the same optical axis. It is installed in. As described above, the first and second problems described above are simultaneously solved.

Further, among the laser chips in the package, a wavefront for converting a wavefront of laser light is provided between the laser chip used for recording / reproducing of an optical recording medium of a 1.2 mm thick substrate and the optical element. By providing a conversion means or an aperture limiting means for limiting the aperture, the convergence state of the laser beam toward the objective lens is converted, and the light condensing state of the objective lens is changed, so that the light of the 1.2 mm thick substrate is changed. It is intended to suppress the occurrence of spherical aberration on a recording medium and obtain a good quality recording / reproducing signal.

On the other hand, a semiconductor device comprising a laser chip, a light receiving element for receiving light reflected from an optical recording medium, and a diffraction element for generating a predetermined wavefront of the reflected light and diffracting the light toward the light receiving element in the same apparatus. The laser device includes the above-mentioned means, that is, two laser chips and an optical element, and means for laser light of two wavelengths to pass in the same traveling direction and on the same optical axis, wavefront converting means, or aperture limiting. In addition to the means, in order to receive laser light of two wavelengths, the light receiving area of the light receiving element is lengthened in the diffraction direction, the light receiving position and the light receiving height are changed according to different wavelengths, and the light receiving element is tilted. In this case, the reflected light from the optical recording medium can be received at any of the different wavelengths by using a means such as providing a light receiving element having a spectral sensitivity curve corresponding to the different wavelength. To obtain a semiconductor laser device having a light receiving element for proper signal detection.

According to the present invention, the laser light emitted from the two laser chips can be positioned on the same optical axis by monitoring the position of the laser light emitted from the two laser chips via an optical lens or the like by the above-described configuration. By switching the laser chip to be driven according to the required wavelength, two types of laser light are emitted from one semiconductor laser device as needed.

The optical head using an objective lens optimized for a 0.6 mm-thick substrate optical recording medium has a light head of 1.2 mm.
When recording / reproducing an optical recording medium having a substrate having a thickness of mm, a wavefront converting means built in a semiconductor laser device, or
A method of changing the focusing state of one of the laser beams by the objective lens by the aperture limiting means and providing a conversion lens or the like outside the semiconductor laser device (between the objective lens and the semiconductor laser device); Even without using a large-scale method such as providing a mechanism for taking the conversion lens in and out according to the difference in the thickness of the substrate, it is possible to suppress the occurrence of spherical aberration and obtain a good quality recording / reproducing signal.

Further, a semiconductor device comprising a laser chip and a light receiving element for receiving reflected light from an optical recording medium, and a diffraction element for generating a predetermined wavefront of the reflected light and diffracting the reflected light toward the light receiving element in the same device. In the laser device, while having the above-mentioned means, ie, two laser chips and an optical element, the light receiving area of the light receiving element is elongated in the diffraction direction to receive laser light of two wavelengths,
In either case of different wavelengths, such as by changing the light receiving position or light receiving height at different wavelengths, or by giving a light receiving element having a spectral sensitivity curve corresponding to different wavelengths,
A semiconductor laser device having a light receiving element that receives reflected light from an optical recording medium and performs appropriate signal detection is obtained.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

[Embodiment 1] FIG. 1 is a partially cutaway perspective view showing the entire structure of a semiconductor laser device, and FIG. 2 is a sectional view of the semiconductor laser device.

Laser beams having different wavelengths, that is, a wavelength 65
Laser chip 1 for emitting laser light of 0 nm, wavelength 78
A laser chip 2 that emits 5 nm laser light, and a wavelength-selective optical element 3 that transmits the wavelength of the laser chip 1 and reflects the wavelength of the laser chip 2 are mounted on the submount members 4a, 4b, and 4c, respectively. It is installed on the stem 5 in the positional relationship shown in FIG. This positional relationship is
The emission end face la of the laser chip 1 is parallel to the reference plane 5b provided on the stem 5, the emission end face 2a of the laser chip 2 is perpendicular to the reference plane 5b, and the wavelength-selective optical element 3 is positioned with respect to the reference plane 5b. It is 45 °.

At this time, the laser light emitted from the laser chip 2 previously positioned together with the submount 4b and reflected by the wavelength-selective optical element 3 is converted into parallel light via an optical lens or the like, and the parallel light is monitored. Meanwhile, the sub-mount 4a including the laser chip 1 is moved while emitting the other laser chip 1 so as to be collimated light via the optical lens or the like. The alignment with the parallel light of the chip 2 is performed. This makes it possible to eliminate the optical shift of the light emitting points of the laser chips 1 and 2. In this way, the laser beams emitted from the two laser chips can be passed on the same optical axis, and both are emitted from the emission window 8a provided at the top of the semiconductor laser device in a direction perpendicular to the reference plane 5b. Emit. 1 and 2, the laser light with a wavelength of 650 nm emitted from the laser chip 1 is indicated by a solid line, and the laser light with a wavelength of 785 nm emitted from the laser chip 2 is indicated by a dotted line. After transmission and reflection at the wavelength-selective optical element 3, both are on the same optical axis, and are shown only by solid lines.

The light receiving elements 6a and 6b for monitoring the optical output are provided behind the laser chips 1 and 2. These components are covered with a cap 8 having an emission window 8a and constitute a semiconductor laser device housed in one package. Reference numeral 10 denotes a lead terminal.

FIG. 3 shows a non-polarizing beam splitter 3 instead of the wavelength-selective optical element 3 for adjusting the optical axis in FIGS.
a.

Laser beams of different wavelengths, that is, wavelength 65
Laser chip 1 for emitting laser light of 0 nm, wavelength 78
A laser chip 2 for emitting a laser beam of 5 nm and a non-polarizing beam splitter 3a are respectively provided with a submount member 4a,
It is mounted on 4b, 4d and is installed on stem 5 in the positional relationship shown in FIG. This positional relationship is such that the emission end face la of the laser chip 1 is parallel to the reference plane 5b provided on the stem 5, and the emission end face 2a of the laser chip 2 is
The reflecting surface of the non-deflecting beam splitter 3a has a 45 ° inclination with respect to the reference surface 5b.

FIG. 4 shows a case where a polarizing beam splitter 3b is used as an optical element for adjusting the optical axis.

Laser beams having different wavelengths, that is, a wavelength 65
Laser chip 1 for emitting laser light of 0 nm, wavelength 78
The laser chip 2 that emits 5 nm laser light and the deflection beam splitter 3b are submount members 4a and 4b, respectively.
e and 4d, and are installed on the stem 5 in the positional relationship shown in FIG. This positional relationship is such that the emission end face la of the laser chip 1 is parallel to the reference plane 5b provided on the stem 5, the emission end face 2a of the laser chip 2 is perpendicular to the reference plane 5b, and the bonding plane of the deflection beam splitter 3b is The angle is 45 ° with respect to the reference plane 5b. Note that the direction of the electric field vector of the laser chips 1 and 2 is the direction shown on the side of FIG.

Also in FIGS. 3 and 4, similarly to the case of FIGS. 1 and 2, the laser beam is emitted from the laser chip 2 positioned first together with the submount 4e, and the beam is split by the deflection beam splitter 3a.
The sub-mount 4a including the laser chip 1 is connected to the other laser chip 1 while monitoring the parallel light while converting the laser light reflected by the laser beam into parallel light via an optical lens or the like.
While emitting light, the light is converted into parallel light through the optical lens or the like, thereby aligning with the parallel light of the laser chip 2 that has been already monitored and is positioned earlier. This makes it possible to eliminate the deviation of the optical emission points of the laser chips 1 and 2. In this way, the laser beams emitted from the two laser chips can pass on the same optical axis, and the emission window 8a provided at the upper part of the semiconductor laser device
From both directions in a direction perpendicular to the reference plane 5b.

Embodiment 2 FIGS. 5, 6, and 7 are cross-sectional views showing an embodiment in which a plurality of laser chips and the optical element for adjusting the optical axis are installed via an L-shaped block.

In FIG. 5, a submount 4c 'on which the laser chip 1, the laser chip 2, and an optical element for adjusting an optical axis (a wavelength-selective optical element in the embodiment of FIG. 5) 3 is mounted is an L-shaped block 4f. Mounted on the stem 5
It is installed in the positional relationship shown in FIG. This positional relationship is the same as the positional relationship shown in the first embodiment.

The deviation in the direction perpendicular to the active layer of the semiconductor laser is caused by the variation in the thickness of the substrate (mainly made of GaAs or the like) of the laser chip.
It is about μm. As described above, the laser beams emitted from the two laser chips are emitted from the emission window 8a provided on the upper part of the semiconductor laser device so as to pass on the same optical axis within a range where the optical aberration can be ignored. According to the present embodiment, by attaching the laser chips 1 and 2 to one L-shaped block, the man-hour for the assembly and the man-hour for adjusting the light emitting point can be effectively reduced.

FIG. 6 shows an optical element for adjusting the optical axis (a wavelength-selective optical element in this embodiment) on the L-shaped block 4f.
3 is provided with a notch 4g for positioning and mounting. By fitting the optical element 3 into the notch 4g, it is easy to mount the optical element with high accuracy, and it is possible to reduce the number of assembling and adjusting steps and to reduce the cost.

FIG. 7 shows a pedestal 4h for positioning and mounting an optical element (in this embodiment, a non-deflection beam splitter) 3a for adjusting the optical axis on the L-shaped block 4f.
Is provided. By attaching the optical element 3a to the pedestal portion 4h, it becomes easy to attach the optical element with high accuracy, so that the number of assembling and adjusting steps can be reduced, and the cost can be reduced.

The semiconductor laser device in the embodiments described above is used as a light source in an optical head using an objective lens optimized for a 0.6 mm thick substrate optical recording medium. When recording / reproducing an optical recording medium having a substrate thickness of 2 mm, in order to suppress the occurrence of spherical aberration, a spherical aberration of a conversion lens or the like is provided outside the semiconductor laser device (between the objective lens and the semiconductor laser device). It is used in an optical head using a method of providing a compensation means.

Embodiment 3 The following embodiment shows an example in which the above-mentioned spherical aberration compensating means such as a conversion lens is provided in a laser package.

FIG. 8 is an enlarged view showing an optical system inside the semiconductor laser device of this embodiment, and FIG. 9 is a diagram showing an outline of an optical system of the semiconductor laser device and an external optical head. is there.

The laser chip 1 is used for an optical recording medium 11 having a thickness of 0.6 mm (for example, an optical recording medium for DVD), and the laser chip 2 is used for an optical recording medium 12 having a thickness of 1.2 mm. (CD-R optical recording medium). The objective lens 21 is a lens optimized for recording / reproducing of the optical recording medium 11,
The light is optimally focused on one information signal surface 11a. Further, between the laser chip 2 and an optical element for adjusting the optical axis (in this embodiment, a wavelength-selective optical element) 3, the wavefront of the laser light emitted from the laser chip 2 is converted and A concave lens 14 is provided as a wavefront converting means for converting the convergence state of the traveling laser light and changing the state of focusing by the objective lens 21. Since the wavefront of the laser light passing through the concave lens 14 is converted, the laser light travels along the optical path indicated by the dotted line, and spherical aberration occurs even on the optical recording medium 12 having a thickness of 1.2 mm through the objective lens 21. And the light is optimally focused on the information signal surface 12a.

Reference numeral 4f denotes an L-shaped block, and reference numeral 4i denotes a member for installing the concave lens 14 as a wavefront converting means. 22 is a detection optical system for detecting the laser light reflected on the optical recording medium 11 or 12, 23 is a beam splitter for splitting the laser light reflected on the optical recording medium 11 or 12 to the detection optical system, 24 is a photodetector.

FIG. 10 is an enlarged view of an optical system inside a semiconductor laser device showing another example, and FIG. 11 is a schematic diagram of an optical system of the semiconductor laser device and an external optical head.

8 and 9 is that laser beam aperture limiting means is used instead of laser light wavefront conversion means. The objective lens 21 is provided for the optical recording medium 1.
1 is a lens optimized for recording / reproduction, and converges optimally on the information signal surface 1la of the optical recording medium 11.
The aperture of the laser light emitted from the laser chip 2 is restricted between the laser chip 2 and the optical element 3 for adjusting the optical axis (the wavelength-selective optical element in this embodiment). An aperture 15 is provided as aperture limiting means for restricting the convergence state of the laser beam toward the, and changing the state of focusing by the objective lens 21. The laser beam that has passed through the aperture 15 travels along the optical path indicated by the dotted line due to the aperture being restricted, and has a spherical aberration even with respect to the optical recording medium 12 having a thickness of 1.2 mm through the objective lens 21. Generation is suppressed and the light is optimally condensed on the information signal surface 12a. The opening diameter is about 0.4 mm. The spread of the beam due to the aperture is about 0.45 degrees and can be ignored optically. Reference numeral 4f denotes an L-shaped block, and reference numeral 4i denotes a member on which the aperture 15 is provided as an aperture limiting means.

FIG. 12 shows still another example.
The wavefront of the laser light emitted from the laser chip 2 is converted between the laser chip 2 and an optical element for adjusting the optical axis (in this embodiment, a non-deflection beam splitter) 3a, so that the laser light converges toward the objective lens. Lens 1 as a wavefront converting means for converting the focusing state by the objective lens
4a is fixedly installed on the optical element 3a. The optical element 3a to which the concave lens 14a is fixed is installed on a pedestal 4h installed on an L-shaped block 4f.

The laser light that has passed through the concave lens 14a is converted into a wavefront, so that the focusing state of the laser beam is changed by the objective lens, and spherical aberration is generated even in the optical recording medium having a substrate thickness of 1.2 mm. And the light is optimally focused on the information signal surface. In this way, by fixing the wavefront converting means to the optical element and installing the same, it is not necessary to use a member for installing the wavefront converting means, and it is not necessary to reduce the number of parts and to adjust the position of the member. Becomes

FIG. 13 shows a case where the aperture 15a is used. The aperture of the laser beam emitted from the laser chip 2 is limited between the laser chip 2 and the optical element (in this embodiment, a non-deflection beam splitter) 3a. Then, the aperture 15 as an aperture limiting means for changing the convergence state of the laser beam toward the objective lens and changing the state of focusing by the objective lens
a is fixed and installed on the optical element 3a. The optical element 3a to which the aperture 15a is fixed is installed on a pedestal 4h installed on an L-shaped block 4f.

The aperture of the laser beam passing through the aperture 15a is restricted, so that the focusing state of the laser beam by the objective lens is changed, and the generation of spherical aberration occurs even in the optical recording medium having the 1.2 mm thick substrate. And the light is optimally focused on the information signal surface. Here, the opening diameter is about 0.6 mm. Further, similarly to the example of FIG. 12, by fixing the aperture limiting means to the optical element and installing the same, it is not necessary to use a member for installing the aperture limiting means, thereby reducing the number of parts and reducing the number of components. No time is required for position adjustment.

Fourth Embodiment FIG. 14 shows a package of a semiconductor laser device having a diffraction element for diffracting reflected light from an optical recording medium and a light receiving element for receiving the reflected light diffracted by the diffraction element. FIG. 2 is a perspective view showing the entire structure of the semiconductor laser device with a part cut away.

A laser chip 1 for emitting a laser beam with a wavelength of 650 nm, a laser chip 2 for emitting a laser beam with a wavelength of 785 nm, and a wavelength-selective optical element that transmits the wavelength of the laser chip 1 and reflects the wavelength of the laser chip 2 3 is installed on the element attaching block 9 a on the stem 9.
This positional relationship is such that the emission end face la of the laser chip 1 is parallel to the reference plane 9b provided on the stem 9, the emission end face 2a of the laser chip 2 is perpendicular to the reference plane 9b, and the wavelength-selective optical element 3 is It is at 45 ° to the surface 9b.

A light receiving element 10 for receiving the reflected light from the optical recording medium is installed in the element attaching L-shaped block 9a, and light receiving elements 6a and 6b for monitoring the optical output are provided behind the laser chips 1 and 2. is set up. These components are covered with a cap 17, and a diffraction element 16 that generates a predetermined wavefront and diffracts the reflected light from the optical recording medium toward the light receiving element is provided on the cap 17.

Reference numeral 13 denotes a lead terminal. The arrow A indicates that the laser beams emitted from the two laser chips 1 and 2 travel in the same traveling direction according to the principle described in the embodiment of the first embodiment, that is, in a manner both of which are perpendicular to the reference plane 9b. A state in which the light is emitted from the diffraction element 16 provided on the upper part of the laser device, is further reflected by the optical recording medium, and returns to the semiconductor laser device is shown. Arrow B indicates how the light diffracted by the diffraction element 16 enters the light receiving element 10.

Also in the present embodiment, the laser light emitted from the two laser chips is converted into parallel light via the optical lens or the like from the laser chip 1 positioned first, and the parallel light is monitored. While the other laser chip 2 emits light, the light is converted into parallel light through the optical lens and the like, and is aligned with the parallel light of the laser chip 1 that has been already monitored and is positioned earlier. 2 and 3 can be eliminated in the direction parallel to the active layer. In addition, the shift of the light emitting point in the direction perpendicular to the active layer is caused by the fluctuation of the thickness of the substrate (mainly made of GaAs or the like) of the laser chip.
It is about 0 μm. As described above, the optical axes of the laser beams emitted from the two laser chips can be aligned on the same optical axis within a range where optical aberrations can be ignored.

FIG. 15 is an enlarged view of the internal structure of FIG. 14, and FIG. 16 is a view of the diffraction element 16, the light receiving element 10, and the diffracted light of different wavelengths as viewed from the optical recording medium side (the following figures). Here, unless otherwise specified, a laser beam having a wavelength of 650 nm is represented by a solid line, and a laser beam having a wavelength of 785 nm is represented by a dotted line, and unless otherwise specified, diffracted light means first-order diffracted light.)

The wavelength 650 n emitted from the laser chip 1
m laser light and the wavelength 7 emitted from the laser chip 2
Each of the 85 nm laser beams is applied to the wavelength selective optical element 3.
Is transmitted and reflected, travels on the same optical axis, passes through the diffraction element 16, is reflected by the optical recording medium, generates a predetermined wavefront by the diffraction element 16, is diffracted, and is received by the light receiving element 10. . The diffraction element 16 is divided into three parts 16a, 16e, and 16f.
And the wavelength is 650 nm in each area.
, Three diffracted lights 2a, 2e, and 2f at a wavelength of 785 nm are generated.

The diffracted lights la and 2a are diffracted lights for detecting a focus error signal. The light receiving area 3 of the light receiving element 10 is divided into two by a dividing line in the same direction as the diffracted light.
The light is condensed on the division line 32 of 1a and 31b,
A focus error signal is obtained from the output difference between a and 31b. The diffracted lights le, 2e, if, and 2f are diffracted lights for detecting a tracking error signal, and are detected by light receiving regions 33 and 34 formed in the light receiving element 10, respectively.

In general, when laser light is diffracted by a diffraction grating having a specific lattice constant, the diffraction angle increases as the wavelength increases. Therefore, in the case of the present embodiment, the diffracted lights la, le, lf of the laser light having the wavelength of 650 nm are focused on the side closer to the optical axis in the light receiving areas 31a, 31b, 33, 34, that is, on the left side of the drawing. On the other hand, the wavelength 785n
The diffracted light 2a, 2e, 2f of the m
Light is condensed on the side farther from the optical axis among 1a, 31b, 33, and 34, that is, on the right side of the drawing. Further, the diffraction angle changes with the temperature change of the wavelength. In this embodiment, when the laser light having a wavelength of 650 nm changes in the range of 625 to 660 nm due to a temperature change or the like, the diffraction angles of the diffracted lights la, le, and 1f are 17.3.
で 18.2 °. On the other hand, a wavelength of 785 nm
Is changed in the range of 770 to 790 nm due to a temperature change or the like, the diffraction angles of the diffracted lights 2a, 2e, and 2f are 2
It changes within the range of 0.6 to 21.9 °. Considering the aforementioned difference in diffraction angle due to different wavelengths, spot position fluctuation due to diffraction angle fluctuation due to temperature change, etc., and focus offset due to component tolerance, assembly tolerance, etc., it is formed on the above-described light receiving element 10. Light receiving area 3
The length L in the diffraction direction of 1a, 31b, 33, 34 is 480
μm.

In this embodiment, the focus error signal is detected on one division line 50 for two wavelengths that vary widely from 625 to 660 nm and 780 to 790 nm. By inclining the angle by 0.74 ° with respect to the x direction of the drawing, the focus offset can be extremely reduced with respect to two wavelengths that change in the range of 625 to 660 nm and 770 to 790 nm. If a diffraction grating having a characteristic in which the focus offset amount is 0 μm with respect to a wavelength of 650 nm is designed, 0.017 μm at 625 nm and −0.0 at 790 nm.
077 μm, and takes a value in a range of 0.017 μm to −0.077 μm in a range of 625 nm to 790 nm. As a result, an extremely small focus offset amount was obtained.

The semiconductor laser device of this embodiment is
It is used as a light source in an optical head using an objective lens optimized for a 0.6 mm thick substrate optical recording medium.
In the case of reproduction, in order to suppress the occurrence of spherical aberration, it is used in an optical head using a method of providing spherical aberration compensating means such as a conversion lens outside the semiconductor laser device (between the objective lens and the semiconductor laser device). You.

FIGS. 17 and 18 show a case where a concave lens 14 as a wavefront conversion element or an aperture 15 as an aperture limiting means (Embodiment 3) is added to the above embodiment.

FIG. 17 shows that the wavefront of the laser light emitted from the laser chip 2 is converted between the laser chip 2 of the semiconductor laser device and an optical element (in this embodiment, a wavelength-selective optical element) 3 and A concave lens 14 is provided as a wavefront converting means for converting the convergence state of the laser beam toward the lens and changing the light condensing state by the objective lens. The laser light that has passed through the concave lens 14 has its wavefront converted, and travels along the optical path indicated by the dotted line, and suppresses the occurrence of spherical aberration even with respect to the optical recording medium having a thickness of 1.2 mm through the objective lens. , And the light is optimally focused on the information signal surface.

FIG. 18 shows a state in which the aperture of the laser beam emitted from the laser chip 2 is limited between the laser chip 2 and the optical element (in this embodiment, the wavelength-selective optical element) 3 of the semiconductor laser device. An aperture 15 is provided as an aperture limiting means for limiting the convergence state of the laser beam toward the lens and changing the light collection state by the objective lens. The laser light that has passed through the aperture 15 travels along the optical path indicated by the dotted line by limiting the aperture, and suppresses the occurrence of spherical aberration even with respect to the optical recording medium having a thickness of 1.2 mm via the objective lens. , And the light is optimally focused on the information signal surface.

Here, the objective lens is a lens optimized for recording / reproducing on an optical recording medium having a thickness of 0.6 mm on a substrate, and a laser beam emitted from the laser chip 1 is an information signal of the optical recording medium. It is assumed that light is condensed optimally on the surface. 9
a is an L-shaped block for attaching elements, 4i (FIG. 17),
4j (FIG. 18) is a member for installing the concave lens 14 and the aperture 15, respectively. Element attachment block 9
a is a light receiving element 10 for receiving light reflected from the optical recording medium.
Is installed. Reference numeral 16 denotes a diffraction element that generates a predetermined wavefront of the reflected light from the optical recording medium and diffracts the light toward the light receiving element 10. 41 and 42 are the diffraction elements 16 respectively.
And 650 nm and 785 nm diffracted light.

According to the structure shown in this embodiment, the two laser chips and the light receiving element for receiving the reflected light from the optical recording medium are housed in the same package, and the diffraction element for diffracting the reflected light in the direction of the light receiving element is provided. Also in a semiconductor laser device having the same, by incorporating the wavefront converting means or the aperture limiting means in the same package, the generation of spherical aberration can be suppressed with one semiconductor laser device, and a good quality recording / reproducing signal can be obtained. A semiconductor laser device including a light receiving element for receiving reflected light from an optical recording medium and performing appropriate signal detection in both cases of two different wavelengths is obtained.

FIGS. 19 and 20 show a laser beam between the laser chip 2 and the optical element (non-polarized beam splitter in this embodiment) 3a which converts the wavefront of the laser light emitted from the laser chip 2 and travels toward the objective lens. A concave lens 14a as a wavefront converting means for changing a convergence state of light and changing a light condensing state by an objective lens restricts an opening of the laser beam emitted from the optical element 3a or the laser chip 2 to be an objective lens. An example is shown in which an aperture 15a as an aperture limiting means for changing a convergence state of a traveling laser beam and changing a condensing state by an objective lens is fixed and installed.

In FIG. 19, the laser beam that has passed through the concave lens 14a is converted into a wavefront, so that the focusing state of the laser beam is changed by the objective lens. The generation of aberration is suppressed, and the light is optimally focused on the information signal surface. In FIG. 20, the laser beam that has passed through the aperture 15a has its aperture restricted so that the focusing state of the objective lens is changed and the spherical aberration of the 1.2 mm thick substrate optical recording medium is reduced. The generation is suppressed and the light is optimally focused on the information signal surface.

According to the example shown in the present embodiment, a single semiconductor laser device can suppress the occurrence of spherical aberration and obtain a high-quality recording / reproducing signal. Optical recording can be performed at any of two different wavelengths. A semiconductor laser device having a light receiving element that receives reflected light from a medium and performs appropriate signal detection is obtained. In addition, by fixing and installing the wavefront converting means or the aperture limiting means on the optical element, it is not necessary to use a member for installing the wavefront converting means, reducing the number of parts and time for adjusting the position related to the member. Is also unnecessary.

[Embodiment 5] FIG. 21 is a diagram showing the diffraction element 16, the light receiving element 50, and the diffracted light of the laser light having wavelengths of 650 nm and 785 nm as viewed from the optical recording medium side in the optical axis direction.

Of the diffracted light of the laser light having a wavelength of 650 nm,
la is a light receiving area 51a formed in the light receiving element 50,
Light is condensed on the dividing line 52 of 51b, and le and lf are 53a,
Light is condensed on 53b.

Similarly, out of the diffracted light of the laser beam having a wavelength of 785 nm, 2a is a light receiving region 5 formed in the light receiving element 50.
Light is condensed on the dividing line 55 of 4a and 54b, and 2e and 2f are 5
Light is condensed on 6a and 56b. The method of detecting the focus error signal and the tracking error signal is the same as that of the fourth embodiment.

Further, in this embodiment, the areas of the light receiving areas 51a, 51b, 53a, 53b for the diffracted light of the laser light having a wavelength of 650 nm used for the high-density optical recording medium are set as follows.
Light receiving area 54 for diffracted light of laser light having a wavelength of 785 nm
a, 54b, 56a, 56b
The response speeds of the light receiving regions 51a, 51b, 53a, 53b are higher than the response speeds of the light receiving regions 54a, 54b, 56a, 56b. As described above, the response speed can be improved by separately forming the light receiving region according to the wavelength of the diffracted light and changing the area of the light receiving region.

Reference numeral 16 denotes a diffraction element having three regions 16a, 16e, and 16f. Diffracted light having a wavelength of 650 nm in each region is converted into la, le, If, and diffracted light 2 having a wavelength of 785 nm.
a, 2e, and 2f.

FIG. 22 is a diagram in which the angles rl and r2 of the two division lines in the light receiving element shown in FIG. 21 are separately designed according to the wavelength.

Light receiving area 61 for focus error signal detection
a, 61b and respective dividing lines 6 of 64a, 64b
The angles rl and r2 of 2, 65 are formed to be inclined by 0.78 ° and 0.83 °, respectively, with respect to the direction of the paper surface x. Thus, in the case of a wavelength of 650 nm, 625 to 660 n
The focus offset amount is -0.001 to 0 in the range of m
In the case of μm and a wavelength of 785 nm, the focus offset amount is −0.010 to 0.
007 μm, and the occurrence of focus offset due to wavelength fluctuation can be further reduced.

Reference numerals 63a, 63b, 66a and 66b are light receiving areas for detecting a tracking error signal.

[Embodiment 6] In this embodiment, light-receiving elements are made of different materials and mounted according to the wavelength of the laser light to be received. This will be described with reference to FIGS.

A Si photodiode which is often used as a light receiving element has a spectral sensitivity curve as shown in FIG. 24A and generally has a peak sensitivity in a wavelength range of 800 to 900 nm. For the 785 nm laser light, the light receiving element as described above is often used, and the light receiving element 70b in FIG. 23 has a spectral sensitivity curve as shown in FIG.

However, in the case of FIG.
Since the light receiving sensitivity of the laser beam of nm is 20% or more lower than that of the laser beam of 785 nm, the signal levels of the focus error signal, the tracking error signal, and the like also decrease. For this reason, in the present embodiment, a light receiving element 70a having a spectral sensitivity curve as shown in FIG. 24A is used as a light receiving element for 650 nm laser light by using a material of GaAsP. The light receiving elements 70 of different materials as described above
a, 70b, 650 nm, 785
In either case, an appropriate signal output can be obtained. Reference numeral 16 denotes a diffraction element having three regions 16a, 16e, and 16f, and diffracts the diffracted light having a wavelength of 650 nm in each region into la, le, If, and the diffracted light 2a, 2 having a wavelength of 785 nm.
e and 2f. The signal detection method and the like are the same as those in the previous embodiments.

FIG. 25 shows a light receiving element 80a having a spectral sensitivity curve having a peak sensitivity near the wavelength of laser light by using the same material (for example, silicon Si) and varying the diffusion depth of impurities in the light receiving region. , 80b are mounted in the same device.

In FIG. 25, the light-receiving element 80a for the wavelength of 650 nm has an impurity diffusion region indicated by 81a, the diffusion depth of which is about 1 μm, and a spectral sensitivity curve as shown in FIG. Have. The light-receiving element 80b for the wavelength of 785 nm has a diffusion region of the impurity indicated by 81b, the diffusion depth of which is about 1.2 μm, and has a spectral sensitivity curve as shown in FIG. By mounting the two light receiving elements 80a and 80b as described above, an appropriate signal output can be obtained even in the case of 650 nm. The signal detection method and the like are the same as in the previous embodiments. 41, 42
Indicates diffracted light at 650 nm and 785 nm, respectively.

FIGS. 26 and 27 show the present embodiment in which dielectric films having different thicknesses are formed on the light receiving element in accordance with the wavelength of the laser beam received. For 650 nm and 785
82a and 82b, respectively,
And

In FIG. 26, the light receiving elements 82a, 82b
On top, a two-layer dielectric film of SiO and SiO ₂ is applied to a thickness of λ / 4. Each refractive index is 1.75, 1.
45, the light receiving element 82a
O film 83a has 112. 1 nm, the SiO ₂ film 84a is 9
2.6 nm, and in the case of the light receiving element 82b, SiO 2
The film 83b is 135.3 nm, and the SiO ₂ film 84b is 11
2. 1 nm.

Further, in FIG. 27, the light receiving element 82
An example is shown in which three dielectric films of Al ₂ O ₃ , ZrO ₂ , and MgF ₂ are formed on layers a and 82b at thicknesses of λ / 4, λ / 2, and λ / 4, respectively. That is, since the respective refractive indices are 1.60, 2.00, and 1.28, the film thickness of the light receiving element 82a is Al ₂ O ₃ film 85a, respectively.
Is 101.6 nm, and the ZrO ₂ film 86a is 162.5 n
m, the MgF ₂ film 87a is 127.0 nm, and in the case of the light receiving element 82b, the Al ₂ O ₃ pus 85b is 12
2.7 nm, ZrO ₂ film 86b is 196.3 nm, Mg
The F2 film 87b has a thickness of 153.3 nm.

As described above, by changing the actual film thickness in accordance with the wavelength to be received, a dielectric film having a high transmittance according to the wavelength can be obtained, and the reflection of diffracted light on the surface of the light receiving element can be suppressed. Accordingly, generation of stray light inside the device can be suppressed.

By mounting two light receiving elements 82a and 82b provided with a dielectric film having a high transmittance as described above, 650
nm and 785 nm, an appropriate signal output can be obtained. 41 and 42 are each 650 nm,
The diffraction light of 785 nm is shown.

[Embodiment 7] Generally, a long wavelength diffracted light has a larger diffraction angle than a short wavelength diffracted light with respect to a certain lattice constant. Therefore, when the light receiving surface is adjusted to the beam waist position of one of the wavelengths, the laser light of the other wavelength causes blurring of the beam at the position of the light receiving surface, causing a focus offset.

In the embodiment shown in FIG. 21, the light receiving elements 88a, 88
By relatively changing the light receiving surface position of b, blurring of the beam due to the difference in wavelength is prevented. Specifically, the installation location 9C of the light receiving elements 88a and 88b has a stepped structure, and the step 3
0 μm was provided. Thus, the light receiving element 88b for the 785 nm wavelength laser light has a light receiving surface located at a position about 30 μm higher than the light receiving element 88a for the 650 nm wavelength laser light. The light receiving element 8 having these positional relationships
8a and 88b are mounted in the same device. This allows
The beam waist of the diffracted light 41 having a wavelength of 650 nm and the diffracted light 42 having a wavelength of 785 nm are both light receiving elements 88a,
The structure is located on the light receiving surface 88b, the beam is not blurred, and the occurrence of focus offset due to wavelength fluctuation is reduced. At this time, if the wavelength is 650 nm, 625
The focus offset amount is -0.0 in the range of -660 nm.
001 to 0 μm, wavelength 785 nm, 780 to 7
In the range of 90 nm, the focus offset amount is -0.0
23 to 0.008 μm, and the occurrence of focus offset due to wavelength fluctuation can be extremely reduced.

The angle of the dividing line was 0.78 °.

FIG. 29 shows a configuration in which one light receiving element 89 having a step structure with a step of 30 μm is provided on the surface facing the diffraction element 16. One surface (diffraction element 1) separated by a step
The light receiving area 8 for the wavelength of 650 nm
9a, a light receiving region 89b for a wavelength of 780 nm is formed on the other surface (the surface closer to the diffraction element 16). Thereby, the light receiving area 89 for the laser beam having a wavelength of 785 nm is formed.
b is the light receiving element 89a for laser light having a wavelength of 650 nm.
On the other hand, the light receiving surface is set at a position relatively higher by about 30 μm. Therefore, the diffracted light 41 having a wavelength of 650 nm and the diffracted light 42 having a wavelength of 785 nm both have a structure in which the beam waist is located on the light receiving surfaces of the light receiving regions 89a and 89b, and the beam is not blurred, and a focus offset due to wavelength fluctuation is generated. Becomes smaller.

FIG. 30 is a cross-sectional view of an example of the light receiving element 90 in which the diffusion depth of the impurity in the light receiving region separated by the step of the light receiving element shown in FIG. 29 is different.

That is, the wavelength 650n formed on one surface (the surface farther from the diffraction element 16) separated by the step.
The light receiving region for m has an impurity diffusion region 90a having a diffusion depth of about 1 μm, and has a spectral sensitivity curve as shown in FIG. In the light receiving region for the wavelength of 785 nm formed on the other surface (the surface closer to the diffraction element 16), there is an impurity diffusion region 90b with a diffusion depth of about 1.2 μm. Has a spectral sensitivity curve as shown in FIG. In this manner, by forming a light receiving region having a spectral sensitivity curve corresponding to a different wavelength on each of the surfaces separated by the step, the diffracted light 41 having a wavelength of 650 nm and the diffracted light 42 having a wavelength of 785 nm both have the beam waist. Is located on the light receiving surface of the light receiving area, the beam is not blurred, the occurrence of focus offset due to wavelength fluctuation is reduced, and good signal levels are obtained at both wavelengths.

FIG. 31 shows a structure in which dielectric films having different thicknesses are separately formed on the light receiving surfaces separated by the steps of the light receiving elements shown in FIGS. 29 and 30, and are mounted in the same device.

The light receiving element 91 has two light receiving areas separated by a step, that is, light receiving areas 91a and 91b for 650 nm and 785 nm laser light. In Figure 31, the light receiving regions 91a, Al ₂ O ₃ on the 91b, ZrO
₂ and MgF ₂ are λ / 4 and λ /
An example in which the thickness is 2, λ / 4 is shown. That is, each refractive index is 1.60, 2.00, 1.28.
Therefore, in the case of the light receiving region 91a, the thickness of the Al ₂ O ₃ film 92a is 101.6 nm, and the thickness of the ZrO ₂ film 9 is 91.6 nm.
3a is 162.5 nm, and the MgF ₂ film 94a is 127.0 nm.
nm, and in the case of the light receiving region 91b,
_{The 2} O ₃ film 92 b is 121.8 nm, and the ZrO ₂ film 93 b is 1
The thickness is 95.0 nm, and the thickness of the MgF ₂ film 94b is 152.3 nm.

As described above, by changing the film thickness in accordance with the wavelength to be received, a dielectric film having a high transmittance according to the wavelength can be obtained, and the reflection of diffracted light on the surface of the light receiving element can be suppressed. The generation of stray light inside the device can also be suppressed. As described above, by mounting the light receiving element 91 provided with the dielectric film having a high transmittance corresponding to the wavelength,
In either case of 5 nm, it is possible to prevent the signal level from lowering and obtain an appropriate signal output. The dielectric film used here may be a two-layer dielectric film of SiO and SiO ₂ .

Further, if necessary, as shown in FIG. 30, a method may be used in which the diffusion depth of impurities in the light receiving region separated by the step of the light receiving element is different. As described above, the light receiving region having the spectral sensitivity curve corresponding to the different wavelength is formed on each surface separated by the step, and the dielectric film having the high transmittance according to the wavelength is applied, so that the wavelength 65
The 0 nm diffracted light 41 and the 785 nm wavelength diffracted light 42
Both have a structure in which the beam waist is located on the light receiving surfaces of the light receiving areas 9la and 9lb, and the beam is not blurred.
The occurrence of focus offset due to wavelength fluctuation is reduced, and good signal output is obtained at both wavelengths.

FIG. 32 shows that the installation location 9d of the light receiving element 10 has an inclined structure, and the light receiving surface of the light receiving element 10 is the stem reference surface 9d.
It is inclined at 5 to 6 degrees with respect to b.

Thus, the diffraction light 4 having a wavelength of 650 nm
1. Both the diffracted lights 42 having a wavelength of 785 nm have a structure in which the beam waist is located on the light receiving surface of the light receiving element 10, so that the beam is not blurred and the occurrence of a focus offset due to wavelength fluctuation is reduced. At this time, the wavelength 650n
m, the focus offset amount is −0.001 to 0 μm in the range of 625 to 660 nm, and in the case of wavelength 785 nm, the focus offset amount is −0.008 to 0.008 μm in the range of 780 to 790 nm. The occurrence of the focus offset due to the fluctuation can be extremely reduced. The angle of the dividing line was 0.78 °.

In the present embodiment, as the inclined structure, there is a method of installing the light receiving element 10 on a pedestal having a required inclination, or a method of giving the light receiving element 10 itself an inclination. Also,
Instead of the light receiving element 10 as needed,
The light receiving element 50 or 60 used in 7 may be used.
Alternatively, the method shown in FIGS. 25, 26, 27, and the like may be used.

The material of the light receiving element used in FIGS. 14 to 32 of the present invention may be Ge, GaP, GaAs if necessary.
s, GaASP, AIGAs, AIGAlnP, etc. may be used.

[0113]

As described above, according to the present invention, laser chips of different wavelengths and a wavelength-selective optical element are incorporated in the package of one semiconductor laser device, so that laser lights of different wavelengths It is possible to provide a semiconductor laser device that can accurately emit light on an axis. When recording / reproducing different types of optical recording media that require laser beams of different wavelengths, it is necessary to mount two separate semiconductor laser devices that emit laser beams of different wavelengths by using the present semiconductor laser device. And the effects of reducing the number of parts, miniaturizing the apparatus, and reducing the cost associated therewith are obtained.

Further, by installing a plurality of laser chips in one L-shaped block, the number of steps for assembling and the number of steps for adjusting the light emitting point can be reduced.

Further, wavefront converting means for converting the wavefront of the laser light into the optical path between one of the laser chips and the optical element,
By providing an aperture limiting means for limiting the aperture of the laser beam, for example, an optical head using an objective lens optimized for an optical recording medium having a thickness of 0.6 mm, for example, a substrate having a thickness of 1.2 mm When recording / reproducing the optical recording medium, it is possible to change the focusing state of one laser beam by the objective lens, and to change the state of the laser beam outside the semiconductor laser device (between the objective lens and the semiconductor laser device). It is possible to suppress the occurrence of spherical aberration and achieve high quality recording / reproduction without using a large-scale method such as a method of providing a conversion lens or the like or a mechanism for taking the conversion lens in and out according to the difference in the thickness of the substrate. A signal can be obtained. That is, it is possible to easily provide compatibility with respect to recording / reproduction of optical recording media having different substrate thicknesses.

The same device is provided with a laser chip, a light receiving element for receiving light reflected from the optical recording medium, and a diffraction element for generating a predetermined wavefront of the reflected light and diffracting the light toward the light receiving element. The semiconductor laser device has a light receiving element that receives reflected light from the optical recording medium and performs appropriate signal detection at both different wavelengths, so that different types of light that require laser light of different wavelengths are provided. When recording / reproducing a recording medium with one optical recording / reproducing device, a semiconductor laser device having a light receiving element for performing appropriate signal detection is obtained.

Further, by installing independent light receiving elements at different heights in the optical axis direction according to the wavelength, the beam waist of both wavelengths is located on the light receiving surface of the light receiving element, and the beam is blurred. And a semiconductor laser device in which the occurrence of a focus offset due to wavelength fluctuations is reduced without generation of a laser beam.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a first embodiment of the present invention.

FIG. 2 is a sectional view of FIG.

FIG. 3 is a cross-sectional view illustrating another configuration example of the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing still another configuration example of the first embodiment of the present invention.

FIG. 5 is a sectional view illustrating a second embodiment of the present invention.

FIG. 6 is a sectional view showing another configuration example of the second embodiment of the present invention.

FIG. 7 is a sectional view showing still another configuration example of the second embodiment of the present invention.

FIG. 8 is an enlarged view of an internal optical system for explaining a third embodiment of the present invention.

FIG. 9 is a sectional view showing an outline of an optical system of a semiconductor laser device and an external optical head according to a third embodiment of the present invention.

FIG. 10 is an enlarged view illustrating another configuration example of the internal optical system according to the third embodiment of the present invention.

FIG. 11 is a sectional view showing another schematic example of the optical system of the semiconductor laser device and the external optical head according to the third embodiment of the present invention.

FIG. 12 is a sectional view showing still another configuration example of the third embodiment of the present invention.

FIG. 13 is a sectional view showing still another configuration example of the third embodiment of the present invention.

FIG. 14 is a perspective view illustrating a fourth embodiment of the present invention.

FIG. 15 is an enlarged view showing an example of the internal configuration of a fourth embodiment of the present invention.

FIG. 16 is a diagram illustrating a diffraction element, a light receiving element, and diffracted light having different wavelengths from the optical recording medium side according to a fourth embodiment of the present invention.

FIG. 17 is a sectional view showing another example of the internal configuration of the fourth embodiment of the present invention.

FIG. 18 is a sectional view showing still another configuration example of the fourth embodiment of the present invention.

FIG. 19 is a sectional view showing still another configuration example of the fourth embodiment of the present invention.

FIG. 20 is a sectional view showing still another configuration example of the fourth embodiment of the present invention.

FIG. 21 is a diagram of a diffraction element, a light receiving element, and diffracted light having different wavelengths as viewed from the optical recording medium side in Embodiment 5 of the present invention.

FIG. 22 is a diagram of a diffractive element, a light receiving element, and diffracted light having different wavelengths as viewed from the optical recording medium side in another example of the fifth embodiment of the present invention.

FIG. 23 is a diagram of a diffraction element, a light receiving element, and diffracted light having different wavelengths as viewed from the optical recording medium side in Embodiment 6 of the present invention.

FIG. 24 is a diagram showing a spectral sensitivity curve.

FIG. 25 is a sectional view illustrating a configuration example of a light receiving element according to a sixth embodiment of the present invention.

FIG. 26 is a sectional view showing another configuration example of the light receiving element according to the sixth embodiment of the present invention.

FIG. 27 is a sectional view showing still another example of the configuration of the light receiving element according to the sixth embodiment of the present invention.

FIG. 28 is a sectional view illustrating a seventh embodiment of the present invention.

FIG. 29 is a sectional view showing another configuration example of the seventh embodiment of the present invention.

FIG. 30 is a cross-sectional view illustrating a configuration example of a light receiving element according to a seventh embodiment of the present invention.

FIG. 31 is a cross-sectional view illustrating another configuration example of the light receiving element in Embodiment 7 of the present invention.

FIG. 32 is a cross-sectional view showing still another configuration example of the light receiving element in Embodiment 7 of the present invention.

FIG. 33 is a perspective view illustrating a conventional technique.

FIG. 34 is a top view illustrating another conventional technique.

FIG. 35 is a perspective view illustrating still another conventional technique.

FIG. 36 is a configuration diagram illustrating an optical system according to the related art.

FIG. 37 is a view for explaining the operation of FIG. 37;

DESCRIPTION OF SYMBOLS 1, 2 Laser chip 3 Wavelength-selective optical element 3a Beam splitter 3b Deflection / separation element 14, 14b Wavefront converting means 15, 15a Opening limiting means 4f, 9a L-shaped block 24 Photodetector 10, 50, 60 70a, 70b, 80a, 80b,
82a, 82b, 88a, 88b, 89, 90, 91
Light receiving element 16 Diffraction element

Claims (9)

[Claims] 1. A plurality of laser chips for emitting laser lights of different wavelengths, and an optical element for adjusting an optical axis for emitting transmitted laser light and reflected laser light on the same optical axis by transmitting and reflecting the laser light. And a semiconductor laser device in a single laser package. 2. A plurality of laser chips for emitting laser lights of different wavelengths, and an optical element for adjusting an optical axis for emitting transmitted laser light and reflected laser light on the same optical axis by transmitting and reflecting the laser light. And a light receiving element for receiving the reflected light from the optical recording medium in one laser package, and generating a predetermined wavefront of the reflected light from the optical recording medium in the laser package to produce the light receiving element. A semiconductor laser device comprising: a diffraction element that diffracts light in a direction; and the light receiving elements each include a light receiving unit that receives reflected light according to a different wavelength. 3. The semiconductor laser device according to claim 2, wherein said light receiving element has independent light receiving sections optimized according to wavelengths. 4. The semiconductor laser device according to claim 2, wherein each of the light receiving sections has a light receiving surface set at a different height in the optical axis direction. 5. The semiconductor laser device according to claim 2, wherein a light receiving surface of said light receiving element is provided to be inclined. 6. The optical element according to claim 1, wherein the optical element for adjusting the optical axis comprises any one of a wavelength-selective optical element, a non-polarizing beam splitter, and a polarizing beam splitter. Semiconductor laser device. 7. The semiconductor laser device according to claim 1, wherein the plurality of laser chips and the optical element for adjusting the optical axis are provided via an L-shaped block. 8. A wavefront converting means for converting a wavefront of a laser beam is provided in an optical path between one of a plurality of laser chips and the optical element for adjusting the optical axis. The semiconductor laser device according to any one of the above. 9. An apparatus according to claim 1, wherein an aperture limiting means for limiting an aperture of the laser beam is provided in an optical path between one of the plurality of laser chips and the optical element for adjusting the optical axis. The semiconductor laser device according to any one of the above.