JP2001250255A - Optical apparatus and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and effectively shorten the wavelength of a laser beam without using a semiconductor laser of a short wavelength, for example in an optical apparatus or an optical disk device that uses a two wavelength laser. SOLUTION: Plural laser diodes LD3, LD2 that emit plural mutually different laser beams L3, L2 respectively are parallelly placed in a direction crossing the emitting direction; and an SHG element 100 for changing the wavelength of the light is provided on the outgoing light side of the laser diodes LD3, LD2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device (particularly a laser coupler) in which a plurality of light emitting elements respectively emitting a plurality of different lights are juxtaposed in a direction intersecting the light emitting direction, and the plurality of lights. The present invention relates to an optical disc device that irradiates a disc-shaped information recording medium with light and reads information with the reflected light.

[0002]

2. Description of the Related Art CD (Compact Disk), DVD
(Digital Video Disc) or MD (Mini Disc)
Read (reproduce) information recorded on an optical recording medium for optically recording and / or reproducing information (hereinafter, may be referred to as an optical disk), or write (record) information to or from them. (Hereinafter, may be referred to as an optical disk device) has a built-in optical pickup.

In such an optical disk device or optical pickup, laser beams having different wavelengths are generally used when the type of optical disk (optical disk system) is different. For example, a laser beam having a wavelength of 780 nm is used for reproducing a CD, and a laser beam having a wavelength of 650 nm is used for reproducing a DVD.

In such a situation where the wavelength of the laser beam differs depending on the type of the optical disk, a compatible optical pickup which enables reproduction of a CD by an optical disk device for a DVD, for example, is desired.

[0005] Fig. 14 shows a conventional laser diode LD1 (emission wavelength 780 nm) for a CD and a laser diode LD2 (emission wavelength 650 nm) for a DVD as described above, which enable reproduction of a CD and a DVD. FIG. 1 is a schematic configuration diagram of a compatible optical pickup 100.

The optical pickup 100 is, for example, 78
A first laser diode LD1, a grating G, a first beam splitter BS1, a first mirror M1, a first objective lens OL1, a first laser diode LD1, which emits a laser beam having a wavelength of 0 nm band.
Multi-lens ML1 and first photodiode PD1
Have a CD optical system individually (ie, discretely) disposed at predetermined positions.

Further, the optical pickup 100 has a second laser diode LD2, a second beam splitter BS2, a collimator C, a second mirror M2, a second objective lens OL2, which emits a laser beam having a wavelength in the 650 nm band, for example.
Second multi-lens ML2 and second photodiode P
D2 has DVD optical systems individually (ie, discretely) arranged at predetermined positions.

[0008] The optical pickup 10 thus configured
0, the first laser diode LD
The first laser light L1 from 1 passes through the grating G, is partially reflected by the first beam splitter BS1, bends the path by the first mirror M1, and is condensed on the optical disk D by the first objective lens OL1. Is done.

The reflected light from the optical disc D passes through the first multi-lens ML1 via the first objective lens OL1, the first mirror M1, and the first beam splitter BS1, and
The light is incident on the first photodiode PD1, and the information recorded on the CD recording surface of the optical disk D is read by the change in the reflected light.

Also in the DVD optical system of the optical pickup 100, the second laser beam L2 from the second laser diode LD2 is partially reflected by the second beam splitter BS2 and passes through the collimator C in the same manner as described above. Then, the path is bent by the second mirror M2, and the light is focused on the optical disk D by the second objective lens OL2.

The reflected light from the optical disk D is transmitted to the second objective lens OL2, the second mirror M2, the collimator C, and the second objective lens OL2.
Through the beam splitter BS2, the second multi-lens M
After passing through L2, it is incident on the second photodiode PD2, and the information recorded on the DVD recording surface of the optical disk D is read by the change of the reflected light.

According to the optical pickup 100, the CD
A laser diode for DVD and a laser diode for DVD are mounted, and the respective optical systems enable reproduction of CD and DVD.

FIG. 15 shows a laser diode LD1 for a CD (oscillation wavelength of 780 nm) and a DVD as described above.
Configuration diagram of another conventional compatible optical pickup 101 mounted with a laser diode LD2 (oscillation wavelength 650 nm) for reproducing CDs and DVDs.

The optical pickup 101 is, for example, 78
A first laser diode LD1, a grating G, a first beam splitter BS1, a dichroic beam splitter DBS, a collimator C, a mirror M, an aperture limiting aperture R for CD, an objective lens OL, a first multi, which emits a laser beam having a wavelength of 0 nm band. The lens ML1 and the first photodiode PD1 each have a CD optical system individually (ie, discretely) disposed at predetermined positions.

Further, the optical pickup 101 includes, for example, a second laser diode LD2, a second beam splitter BS2, a dichroic beam splitter DBS, a collimator C, which emits a laser beam having a wavelength in the 650 nm band.
Mirror M, objective lens OL, second multi-lens ML2,
And the second photodiode PD2 individually (ie, discretely) disposed at a predetermined position.
Optical system.

In each of these optical systems, some optical members are shared, for example, a dichroic beam splitter DBS, a collimator C, a mirror M, and an objective lens OL.
Is shared by both optical systems. Further, since the optical axis is shared between the dichroic beam splitter DBS and the optical disk D, the aperture limiting aperture R for CD is D
It is also arranged on the optical axis of the VD optical system.

The optical pickup 10 constructed as described above
In the optical system for one CD, the first laser diode LD
The first laser beam L1 from No. 1 passes through the grating G, is partially reflected by the first beam splitter BS1, passes or reflects through the dichroic beam splitter DBS, the collimator C, and the mirror M, and returns to the CD.
The light is condensed on the optical disk D by the objective lens OL1 via the aperture limiting aperture R.

The reflected light from the optical disk D passes through the first multi-lens ML1 via the objective lens OL, the aperture limiting aperture R for CD, the mirror M, the collimator C, the dichroic beam splitter DBS and the first beam splitter BS1. Is incident on the first photodiode PD1, and the change in the reflected light causes the CD
The information recorded on the data recording surface is read.

In the DVD optical system of the optical pickup 101, the second laser diode L
The second laser light L2 from D2 is partially reflected by the second beam splitter BS2, passes or reflects through the dichroic beam splitter DBS, the collimator C, and the mirror M, respectively, and passes through the aperture limiting aperture R for CD. The light is focused on the optical disk D by the lens OL1.

The reflected light from the optical disc D passes through the second multi-lens ML2 via the objective lens OL, the CD aperture limiting aperture R, the mirror M, the collimator C, the dichroic beam splitter DBS and the second beam splitter BS2. Is incident on the second photodiode PD2, and the change in the reflected light causes the DVD of the optical disc D to
The information recorded on the data recording surface is read.

According to the optical pickup 101, FIG.
Similarly to the optical pickup 100 shown in FIG. 4, a laser diode for a CD and a laser diode for a DVD are mounted, and a CD and a DVD are provided by having respective optical systems.
It is possible to play.

[0022]

The present inventor can construct an optical disk system having a different wavelength, such as a CD or a DVD, with respect to such a conventional optical pickup. We have already proposed an optical device capable of realization and cost reduction and an optical disk device using the same.

FIGS. 16 to 19 show an example thereof. According to the compatible optical pickup 1a shown in FIG.
Laser diode LD1 for CD (oscillation wavelength 780n
m) and a laser diode LD2 for DVD (oscillation wavelength 6
50 nm).

The optical pickup 1a has an optical system individually (ie, discretely) or on a common substrate (ie, monolithically), and is formed adjacent to each other and in parallel, for example, at 780 nm. 780, a laser diode LD having a first laser diode LD1 for emitting laser light of a wavelength in the band and a second laser diode LD2 for emitting laser light of a wavelength in the 650 nm band.
A grating G, a beam splitter BS, a collimator C, a mirror M, an aperture limiting aperture R for CD, an objective lens OL, a multi-lens ML, and a photodiode P for the nm band and transparent to the 650 nm band.
D are respectively provided at predetermined positions. In the photodiode PD, a first photodiode that receives light in the 780 nm band and a second photodiode that receives light in the 650 nm band are formed adjacent to and parallel to each other.

In the optical pickup 1a, the first laser light L1 from the first laser diode LD1 passes through the grating G, is partially reflected by the beam splitter BS, and has an aperture limiting aperture for the collimator C, mirror M, and CD. R passes through (reflects) with the objective lens O
L converges on the optical disc D.

The reflected light from the optical disk D passes through the multi-lens ML via the objective lens OL, the CD aperture limiting aperture R, the mirror M, the collimator C, and the beam splitter BS, and passes through the photodiode PD (first photodiode). ), And this change in reflected light causes C
The information recorded on the recording surface of the optical disc D, such as D, is read.

Then, in the optical pickup 1a, the second laser light L2 from the second laser diode LD2 is also
The light is condensed on the optical disk D by following the same path as described above, and the reflected light is incident on the photodiode PD (second photodiode). Due to the change in the reflected light, the light is reflected on the recording surface of the optical disk D such as a DVD. Reading of the recorded information is performed.

According to this optical pickup 1a, a laser diode for CD and a laser diode for DVD are mounted, and the reflected light is coupled to the photodiode for CD and the photodiode for DVD by a common optical system.
It enables playback of CDs and DVDs.

FIG. 17 is a perspective view of a main part of the laser diode LD. For example, a semiconductor block 13 in which a PIN diode 12 as a photodetection element for monitoring is formed on a protrusion 21 a provided on a disc-shaped base 21.
Is fixed, and the first laser diode 14 (L
D1) and the second laser diode 15 (LD2). Further, a terminal 22 is provided through the base 1 and is connected to the first and second laser diodes 14, 15 or the PIN diode 12 by a lead 23 to supply power for driving each diode. Is done.

FIG. 18A is a plan view of a main part of the laser diode taken from a direction perpendicular to the laser beam emission direction. FIG. 18B is a plan view of the laser diode taken from the laser beam emission direction. FIG. A first laser diode 14 (LD1) and a second laser diode 15 (LD2) are discretely disposed above a semiconductor block 13 on which a PIN diode 12 is formed. These laser diodes may be monolithically arranged as shown at 14a in FIG.

Here, the PIN diode 12 has, for example, two divided regions, and the first and second laser diodes 14, 15 or each of LD1, LD2 are emitted toward the rear (rear) side. Sensing the laser light,
The intensity is measured and the first and second laser diodes 14, 15 or LD are controlled so that the intensity of the laser light is constant.
1. APC (Automatic Po
wer Control) control.
The PIN diode 12 may be one without being divided (can be used by switching).

The laser beam emitting portion E1 of the first laser diode 14 and the laser beam emitting portion E of the second laser diode 15
The interval d of 2 is set, for example, in a range of about 200 μm or less (eg, about 100 μm). Each laser beam emitting part E
For example, laser beams L1 and L2 having a wavelength of 780 nm and 650 nm, respectively, are emitted from E1 and E2 in the same direction (parallel).

FIG. 19A is a plan view of a main part of the photodiode PD. For example, a first photodiode 16 for receiving light in the 780 nm band and a second photodiode 18 for receiving light in the 650 nm band are formed adjacent to and parallel to each other.

Here, the first photodiode 16 is divided into six parts (a1, b1, c1, d1, e1,.
f1). The laser light in the 780 nm band emitted from the first laser diode 14 is split into three laser lights by the grating G, passes through the optical system, and is reflected as light reflected from an optical disk D such as a CD in FIG. As shown in (a), the first photodiode 1
The light is incident on the light spot 6 as three spots (S1a, S1b, S1c).

The second photodiode 18 has a configuration divided into four parts (a2, b2, c2, d2) as shown in the drawing. The laser light in the 650 nm band emitted from the second laser diode 15 passes through the above optical system and
As reflected light from an optical disk D such as VD, FIG.
As shown in (a), the light is incident on the second photodiode 18 as one spot S2.

First and second photodiodes 16 and 18
, That is, the distance d between the center line of the first photodiode 16 and the center line of the second photodiode 18, for example.
Is, for example, in the range of about 200 μm or less (for example, 100 μm).
m). Here, for example, the first
The distance between the laser light emitting portion E1 of the laser diode 14 and the laser light emitting portion E2 of the second laser diode 15 is set to be substantially equal.

As described above, by setting the distance between the laser light emitting portions of the first and second laser diodes and the distance between the first and second photodiodes, the first laser can be used by using a common optical member. It is possible to irradiate the light emitted from the diode and the second laser diode to an optical disc such as a CD or DVD, and to make the reflected light from the optical disc enter the first photodiode and the second photodiode, respectively.

In the photodiode PD (the first photodiode 16 and the second photodiode 18), the spot S1 of the incident laser beam as described above.
a, S1b, S1c, the spot diameter of S2, a change in position, and the like can be detected.

As an optical pickup of an optical disk device,
From the signal obtained by the photodiode PD,
The tracking error signal, the focus error signal, and the information signal recorded on the optical disk are read. Extraction of these signals is performed as follows.

That is, in the first photodiode 16, the signal a 1 obtained at the central spot S 1 a incident on the six divided first photodiode 16,
Using b1, c1 and d1, the following equation (1) gives C
An information signal RF1 recorded on an optical disk such as D can be obtained. RF1 = a1 + b1 + c1 + d1 (1)

The signals a1, b1, c1 and d
1, the focus error signal FE1 can be obtained by the following equation (2). FE1 = (a1 + c1)-(b1 + d1) (2)

Using the signals e1 and f1 obtained at the spots S1b and S1c on both sides incident on the first photodiode 16 divided into six, a tracking error signal TE1 is obtained by the following equation (3). be able to. TE1 = e1-f1 (3)

On the other hand, in the second photodiode 18, the signals a2 and b obtained at the central spot S2 incident on the quadrant divided second photodiode 18 are obtained.
2, c2, and d2, and DV
An information signal RF2 recorded on an optical disk such as D can be obtained. RF2 = a2 + b2 + c2 + d2 (4)

The signals a2, b2, c2 and d
2, a focus error signal FE2 can be obtained by the following equation (5). FE2 = (a2 + c2)-(b2 + d2) (5)

The signals a2, b2, c2 and d
19, the tracking error signal TE2 can be obtained by the DPD (Differential Phase Detection) method as shown in FIG. 19B. For example, signals a2 and b2 and signals c2 and d
After comparing the two phases, the adder AD performs an addition operation to obtain a tracking error signal TE2. According to the DPD method, stable tracking without offset in one spot can be performed.

In the optical disk reproducing / recording apparatus having a built-in optical pickup, as described above, the focus error signal due to the vertical shake of the optical disk such as a CD or DVD is detected, and the focusing is performed according to the obtained focus error signal. Apply servo. Further, a tracking error signal is detected, and a tracking servo is applied according to the obtained tracking error signal.

The optical pickup 1a is composed of a laser diode LD1 for CD (oscillation wavelength 780 nm) and a DV
Laser diode LD2 for D (oscillation wavelength 650 nm)
Is a compatible optical pickup capable of reproducing CDs and DVDs.

This optical pickup comprises a first laser diode LD1 and a second laser diode LD2 arranged adjacently and in parallel, and a first photodiode 16 and a second photodiode 18 arranged adjacently and in parallel. There is no need to align optical axes from laser diodes having different oscillation wavelengths, and the light emitted from the first laser diode LD1 and the second laser diode LD2 can be converted to a CD or DVD using a common optical member. And the reflected light from the optical disk is incident on the first photodiode and the second photodiode, respectively. Therefore, the number of parts is smaller than that shown in FIGS. 14 and 15, and it is easy to assemble, and it is possible to reduce the size and cost.

[0049]

In order to further increase the density of an information recording medium such as an optical disk, it is necessary to shorten the wavelength of laser light emitted from a light emitting element such as a laser diode.

That is, when a short-wavelength laser beam is used,
The diameter of the laser beam spot formed on the optical disk or the like becomes smaller, and the amount of information that can be picked up from the optical disk or the like can be increased.

However, in an optical device using a "two-wavelength laser" in which a 780 nm band semiconductor laser for a CD and a 650 nm band semiconductor laser for a DVD are integrated on a single chip, it is necessary to shorten the wavelength of laser light. No effective proposal has yet been made.

Therefore, an object of the present invention is to provide an optical device or an optical disk device using a two-wavelength laser, which can effectively shorten the wavelength of light such as laser light without using a short-wavelength semiconductor laser. Device and an optical disk device.

[0053]

That is, an optical device according to the present invention is an optical device in which a plurality of light emitting elements respectively emitting a plurality of lights having different wavelengths are juxtaposed in a direction intersecting a light emitting direction. A wavelength conversion element for converting the wavelength of the light is provided on the light emission side of the light emitting element.

Also, in the optical disk device of the present invention, a plurality of light emitting elements respectively emitting a plurality of lights having different wavelengths are juxtaposed in a direction intersecting the light emitting direction, and the plurality of lights are transferred to a disk-shaped information recording medium. In an optical disc apparatus provided with a plurality of light receiving elements for receiving the reflected light and receiving the reflected light, a wavelength conversion element for converting the wavelength of the light is provided on the light emission side of the light emitting element. It is characterized by.

According to the optical apparatus and the optical disk apparatus of the present invention, the wavelength conversion element for converting the wavelength of the light is provided on the light emission side of the light emitting element. For example, in the case of an optical device or an optical disk device using a two-wavelength laser, the light emitted from at least one of the lasers can be easily and effectively shortened without using a special short-wavelength laser. It is possible to increase the density of an information recording medium such as an optical disk.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described based on embodiments. Unless otherwise specified, the following description is common to both the optical device and the optical disk device.

In the present invention, a predetermined coating is applied to the light incident surface and / or the light output surface of the wavelength conversion element, so that light of a predetermined wavelength can be emitted.

Further, a filter may be provided for selectively transmitting light emitted from the wavelength conversion element according to the wavelength.

Further, the plurality of light emitting elements and the wavelength conversion element are preferably fixed on a base.

The light emitted from the plurality of light emitting elements is generally guided to a plurality of light receiving elements through an objective lens. In this case, the light emitted from the plurality of light emitting elements is transmitted to the objective lens. Through the objective lens, in particular, a disc-shaped information recording medium, and the reflected light is preferably incident on the plurality of light receiving elements through the objective lens.

The light emitting element is not particularly limited by the type of emitted light, but is preferably practically capable of emitting laser lights of mutually different wavelengths.

On the other hand, in the optical device of the present invention, the plurality of light-emitting elements and the respective emitted lights are guided to the irradiation object or the disc-shaped information recording medium, and the reflected light is guided to the plurality of light-receiving elements. And a light receiving element are provided on a common base, and are configured as an optical coupler.

Further, it is preferable that the optical disk device is configured as an optical pickup.

Specifically, according to the present invention, G
Even if a short wavelength laser such as an aN-based semiconductor laser is not used, a laser of a different wavelength is formed on a conventional GaAs substrate by a method such as a vapor phase growth method, and a short wavelength laser is formed by a combination with a wavelength conversion element. Wavelength lasers can be made. This allows G
The growth of the conventional GaAs-based and AlGaInP-based two-wavelength lasers (or three-wavelength lasers or the like) in combination with the short-wavelength lasers using the wavelength conversion element is performed without growing the different crystal properties of aAs and GaN. A laser having a combination of the above wavelengths is also possible: the same applies hereinafter, but a two-wavelength laser will be described as a representative example). That is, an AlGaAs system (for example, 800
nm: for long wavelength) and AlGaInP-based (for example, 650)
Even if a two-wavelength laser using a semiconductor of (nm: for short wavelength) is used, a two-wavelength laser that can be used in, for example, the 650 nm band and the 400 nm band can be produced by combining this with a wavelength conversion element. .

As a short wavelength laser, a 410 nm band laser using a GaN-based material has been developed. However, since this semiconductor laser is made of a GaN-based semiconductor (hexagonal), the type of the crystal is different from that of a GaAs-based (zinc-blende), and the lattice constant is small. There is a problem that can not be created.

That is, to produce a GaN laser, Ga
Since it is necessary to use a substrate (for example, a sapphire substrate or a GaN substrate) different from the As-based laser, it is difficult to create another GaAs-based semiconductor laser on the same substrate. 2 capable of emitting laser beams having different short wavelengths on the same substrate
A laser having a wavelength (a plurality of wavelengths) can be produced. In the present invention, the semiconductor growth on a GaAs substrate, which has been widely used, the two-wavelength laser technique described above, and SH
By combining with the technology of G (Second Harmonic Generation), a two-wavelength laser that can be used at a shorter wavelength can be easily supplied.

Next, a preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a main part of a laser diode according to a first embodiment of the present invention, as viewed from a direction perpendicular to a laser light emitting direction. A first laser diode LD3 and a second laser diode LD2 are monolithically arranged above a semiconductor block 13 on which a PIN diode 12 is formed. These laser diodes are shown in FIG.
As shown in (a), they may be arranged discretely.

The PIN diode 12 has, for example, two divided regions, and detects the laser light emitted to the rear (rear) side of each of the first and second laser diodes LD3 and LD2. Then, the intensity is measured, and the APC (Automatic Power Control) that controls the drive current of the laser diodes LD3 and LD2 so that the intensity of the laser light becomes constant.
matic Power Control) control.

On the light emitting surface side of the first diode LD3 and the second diode LD2, an SHG element (wavelength conversion element for generating second harmonic: hereinafter abbreviated as SHG for short) 100 is provided to face the light emitting surface. A coating (R coating) having a specific reflectance is provided on the incident surface (back surface) of the SHG100.
However, the emission surface (front surface) is provided with a coating (F coat) having a specific reflectance. Note that the first diode LD3 and the second diode LD2 are SHG1
00 and may be fixed on the same substrate or may be separately fixed.

Now, the second laser diode LD2 is made of, for example, an AlGaInP system,
Consider a case where a laser beam L2 of nm is emitted. As shown in the table of FIG. 1, the SHG 10
The reflectance of the R coat of 0 is 0%, and the reflectance of the F coat is 0%.
In the case of, the laser light L2 remains at 650 nm and the SHG
Pass 100.

The first laser diode LD3 is made of, for example, an AlGaAs-based material.
When the laser light L3 of 0 nm is emitted, the laser light L3 is 波長 wavelength (400 nm) by the SHG 100.
Is converted into a laser beam L3 ′. For this reason, as shown in the table of FIG. 1, the reflectance of the R coat of SHG100 is 0%, the reflectance of the F coat is 100%,
When the reflectance of the F coat is 0% with respect to nm, the laser light L
3 is a laser beam L3 ′ having a wavelength of 400 nm,
Emitted from 100.

As described above, by disposing the SHG 100, the wavelength of one laser beam emitted from the laser diode can be reduced to half. Therefore 650
The laser beam of nm is used for DVD, and the laser beam of 400 nm is used for next-generation DVD.

Next, FIG. 2 shows another embodiment of the present invention. In addition to the configuration shown in FIG. 1, a light filter 200 is further provided on the emission side of the SHG 100. . The light filter 200 selectively transmits light emitted from the SHG 100 according to the wavelength.

Now, the reflectivity of the F coat of the SHG 100 is set to 80% with respect to the laser beam having a wavelength of 800 nm, and the reflectance of the laser beam having a wavelength of 400 n
0% with respect to the laser beam of m
1 except that the laser beam L2 passes through the SHG 100 without changing the wavelength of 650 nm. On the other hand, since the laser light L3 is reflected by the F coat by 80%, when the laser light L3 passes through the SHG 100, the emitted light becomes light L3 ′ having a mixed wavelength of 400 nm and 800 nm.

If the upper portion of the filter 200 is configured to transmit a wavelength of 800 nm and the lower portion is configured to transmit a wavelength of 400 nm, for example, by moving the filter 200 in a direction perpendicular to the plane of the drawing, a laser having the above-described wavelengths is mixed. Laser light having a wavelength of 400 nm and 800 nm can be selected and extracted from the light L3 '.

FIG. 3A shows a main part of still another embodiment, in which a first laser diode LD4 (wavelength 880 nm, AlGaAs
System), the second laser diode LD5 (wavelength 780 nm,
AlGaAs), third diode LD2 (wavelength 650)
nm) is formed. Here, if the reflectance of the R coat and the F coat of the SHG 100 is set as shown in the table of FIG. 3, the laser light L2 having a wavelength of 650 nm and the wavelength 780
nm laser light L5 is transmitted as it is and has a wavelength of 880 n.
m is reflected 100% by the F coat, and as a result, the wavelength 4
It becomes a laser beam L4 'of 40 nm.

Therefore, in this example, three types of laser beams can be extracted, and two types of laser beams are used for CD (7
80 nm) and for DVD (650 nm), and the other type is reduced to half (440 nm) of the wavelength of the emitted light of the laser diode of 880 nm, so that it can be used for next-generation DVD.

In FIG. 3B, a filter 200 having the same function as described above is provided on the emission surface side of the SHG 100, and laser beams having different wavelengths are selectively selected according to the wavelength. Laser light can be extracted.

Next, a configuration common to the above-described embodiments will be described.

FIG. 4 shows first laser diodes LD3 and 650n which emit laser light having a wavelength in the 800 nm band, for example.
A monolithic laser diode 14a on which a second laser diode LD2 that emits laser light of an m-band wavelength is mounted on one chip is shown.
5 shows the SHG 100 mounted on the emission side of FIG.

For example, a PI as a photodetector for monitoring is provided on a projection 21a provided on a disc-shaped base 21.
A semiconductor block 13 on which an N diode 12 is formed is fixed, and first and second laser diodes L
The monolithic laser diode 14a having D1 and LD2 on one chip and the SHG 100 are arranged.
Further, a terminal 22 is provided through the base 21,
The leads 23 are connected to the first and second laser diodes LD3 and LD2 or the PIN diode 12 to supply drive power for the respective diodes.

FIG. 5 is a cross-sectional view taken on a plane perpendicular to the direction in which the laser diode emits laser light. The first laser diode LD3 and the second laser diode LD2 are mounted on the semiconductor block 13 on which the PIN diode 12 is formed.
Monolithic laser diode 14a on chip
Is arranged.

The PIN diode 12 senses the laser light emitted to the rear side of the first and second laser diodes LD3 and LD2, measures the intensity thereof, and measures the intensity so that the intensity of the laser light becomes constant. APC control for controlling the drive current of the first and second laser diodes LD1 and LD2 is performed.

The above monolithic laser diode 14
a will be described. As the first laser diode LD3, an n-type GaAs buffer layer 31, an n-type AlGaAs cladding layer 32, and an active layer 3 are formed on an n-type GaAs substrate 30.
3. A p-type AlGaAs cladding layer 34 and a p-type GaAs cap layer 35 are laminated. The region 41 is insulated from the surface of the p-type GaAs cap layer 35 to a depth in the middle of the p-type AlGaAs cladding layer 34 to form a stripe having a current confinement structure.

On the other hand, as the second laser diode LD2, an n-type GaAs buffer layer 31, an n-type InGaP buffer layer 36, an n-type AlGa
InP clad layer 37, active layer 38, p-type AlGaIn
A P cladding layer 39 and a p-type GaAs cap layer 40 are laminated. From the surface of the p-type GaAs cap layer 40 to the p-type A
The region 41 is insulated to a certain depth in the 1GaInP cladding layer 39 to form a stripe having a current confinement structure.

In the first laser diode LD3 and the second laser diode LD2, the p-type GaAs cap layers 35 and 40 are formed with the p-electrode 42 connected thereto, and the n-type GaAs substrate 30 is formed with the n-electrode 43 connected thereto. ing. The monolithic laser diode 14a is connected and fixed to the electrode 13a formed on the semiconductor block 13 from the p-electrode 42 side by soldering or the like.

The distance d between the laser beam emitting portion of the first laser diode LD3 and the laser beam emitting portion of the second laser diode LD2 is set in a range of, for example, about 200 μm or less (eg, about 100 μm). For example, the laser beams L1 and L6 having a wavelength of 800 nm
Laser light L2 having a wavelength in the 50 nm band is emitted in substantially the same direction (substantially parallel).

On the other hand, the distance between the first and second photodiodes 16-17 and 18-19 is also 2 in the same manner as described above.
The light emitted from the first laser diode and the second laser diode is applied to an optical disc such as a CD or DVD using a common optical member, and the reflected light from the optical disc is set to a range of about 00 μm or less (for example, about 100 μm). Can be coupled to the first photodiode and the second photodiode, respectively.

Next, the first laser diode LD3
A method for forming the monolithic laser diode 14a in which the second laser diode LD2 and the second laser diode LD2 are mounted on one chip will be described.

First, as shown in FIG. 6A, an n-type GaAs buffer layer 31 and an n-type AlGaAs cladding are formed on an n-type GaAs substrate 30 by an epitaxial growth method such as a metal organic chemical vapor deposition (MOVPE) method. A layer 32, an active layer (a multiple quantum well structure having an oscillation wavelength of 800 nm) 33, a p-type AlGaAs cladding layer 34,
Type GaAs cap layers 35 are sequentially stacked.

Next, as shown in FIG. 6B, a region left as the first laser diode LD1 is protected by a resist film (not shown), and sulfuric acid-based non-selective etching and
The first laser diode L is formed by wet etching (EC1) such as hydrofluoric acid-based AlGaAs selective etching.
The n-type AlGaAs cladding layer 32 is formed in a region other than the D1 region.
The above laminate up to is removed.

Next, as shown in FIG. 7C, an n-type InGaP buffer layer 36 and an n-type InGaP buffer layer 36 are formed on the n-type GaAs buffer layer 31 by an epitaxial growth method such as a metal organic vapor phase epitaxy (MOVPE). AlG
aInP cladding layer 37, active layer (oscillation wavelength 650 nm)
), A p-type AlGaInP cladding layer 39, and a p-type GaAs cap layer 40.

Next, as shown in FIG. 7D, a region left as the second laser diode LD2 is protected by a resist film (not shown), and a sulfuric acid-based cap etching and a phosphate-hydrochloric acid-based quaternary are used. The n-type InGaP is formed in a region other than the region of the second laser diode LD2 by wet etching (EC2) such as selective etching or hydrochloric acid-based separation etching.
The stacked body up to the buffer layer 36 is removed, and the first laser diode LD1 and the second laser diode LD2 are separated.

Next, as shown in FIG. 8E, a portion to be a current injection region is protected by a resist film (not shown).
Impurity D is introduced by ion implantation or the like, and p-type GaAs
A region 4 insulated from the surface of the cap layers 35 and 40 to a depth in the middle of the p-type AlGaAs cladding layers 34 and 39
1 to form a stripe having a current confinement structure.

Next, as shown in FIG.
Ti / P to connect to the As cap layers 35 and 40
A p-type electrode 42 such as t / Au is formed, while an n-type Ga
AuGe / Ni / Au so as to be connected to the As substrate 30.
After forming an n-type electrode 43 such as
A desired first laser diode LD1 and a desired second laser diode LD2 are mounted on a single chip as a monolithic laser diode 14a.

FIG. 9 shows the arrangement (a) of the above-mentioned photodiode, and a tracking error signal, a focus error signal, and an information signal recorded on an optical disk are read from a signal obtained by the photodiode.

Then, as described above, a focus error signal due to a vertical shake of an optical disk such as a DVD is detected, and a focusing servo is applied according to the obtained focus error signal. Further, a tracking error signal is detected, and a tracking servo is applied according to the obtained tracking error signal.

That is, the front and rear first photodiodes 16,
At 17, the signals a 1, b 1, c obtained at the spots S 1 a, S 1 b incident on the front and rear first photodiodes 16, 17 divided into eight and four, respectively.
1, d1, e1, f1, g1, h1, i1, j1, k1
And l1 and the next-generation DVD by the following equation (6):
The information signal RF1 recorded on an optical disk such as the above can be obtained. RF1 = a1 + b1 + c1 + d1 + e1 + f1 + g1 + h1 + i1 + j1 + k1 + 11 (6)

The signals a1, b1, c1, d
1, e1, f1, g1, h1, i1, j1, k1, and l
1, the focus error signal FE1 can be obtained by the following equation (7). FE1 [(a1 + d1 + e1 + h1)-(b1 + c1 + f1 + g1)]-[(i1 + 11)-(j1 + k1)] (7)

The signals a1, b1, c1, d1, e1, f1, and
Using g1 and h1, the same DPD (Differential Phase Detec) as shown in FIG.
The tracking error signal TE1 can be obtained by the method. For example, a first adder (wideband) AD1
, Signals a1 and b1, signals c1 and d1, and signals e1 and f
1. The signal g1 and the signal h1 are subjected to an addition operation, and the phase comparator PC uses the signal a1 and the signal b1 and the signal c1 and the signal d1 and the signal g1 and the signal h1 and the signals e1 and f1.
After the phase of the sum signal is compared with the sum, a second adder AD2 performs an addition operation to obtain a tracking error signal TE1. According to the DPD method, stable tracking without offset in one spot can be performed.

On the other hand, the front and rear second photodiodes 18,
In 19, the signals a2, b2, obtained at the spots S2a, S2b incident on the front and rear second photodiodes 18, 19 divided into eight and four, respectively.
c2, d2, e2, f2, g2, h2, i2, j2, k
The information signal RF2 recorded on an optical disk such as a DVD can be obtained by the following equation (9) using 2 and l2. RF2 = a2 + b2 + c2 + d2 + e2 + f2 + g2 + h2 + i2 + j2 + k2 + l2 (9)

The signals a2, b2, c2, d
2, e2, f2, g2, h2, i2, j2, k2 and l
2, a focus error signal FE2 can be obtained by the following equation (10). FE2 = [(a2 + d2 + e2 + h2)-(b2 + c2 + f2 + g2)]-[(i2 + 12)-(j2 + k2)] (10)

The signals a2, b2, c2, d2, e2, f2, and
Using g2 and h2, the same DPD (Differential Phase Detec) as shown in FIG.
The tracking error signal TE2 can be obtained by the method. For example, a first adder (wideband) AD1
, Signals a2 and b2, signals c2 and d2, signals e2 and f
2. The addition operation of the signals g2 and h2 is performed, and the phase comparator PC sums the signals a2 and b2, the signals c2 and d2, the signals g2 and h2, and the signals e2 and f2.
After the phase of the sum signal is compared with the sum, a second adder AD2 performs an addition operation to obtain a tracking error signal TE2. According to the DPD method, stable tracking without offset in one spot can be performed.

In the optical disk reproducing / recording apparatus using this laser coupler, as described above, the focus error signal due to the vertical shake of the optical disk such as a DVD is detected, and the focusing servo is performed in accordance with the obtained focus error signal. Multiply. Further, a tracking error signal is detected, and a tracking servo is applied according to the obtained tracking error signal.

This laser coupler is composed of a next-generation DVD laser diode LD3 (oscillation wavelength: 400 nm) and a DVD.
A laser diode LD2 (oscillation wavelength: 650 nm) is mounted, and a compatible optical pickup capable of reproducing two types of DVDs can be configured.

The laser coupler comprises a first laser diode LD3 and a second laser diode LD2 which are arranged adjacently and in parallel, and front and rear first photodiodes 16 and 17 which are arranged adjacently and in parallel. And the front and rear second photodiodes 18 and 19, there is no need to align optical axes from laser diodes having different oscillation wavelengths, and the first laser diode LD1 and the second laser The light emitted from the diode LD2 is applied to an optical disc such as a DVD, and the reflected light from the optical disc is made incident on the front and rear first photodiodes 16 and 17 and the front and rear second photodiodes 18 and 19, respectively. Therefore, the number of parts is smaller than that shown in FIGS. 14 and 15, and it is easy to assemble, and it is possible to reduce the size and cost.

FIG. 10 shows the configuration of an optical pickup using the laser coupler according to the present embodiment. Laser beams L1 and L2 emitted from the first and second laser diodes incorporated in the laser coupler 1a are transmitted to an optical disc D such as a DVD via a collimator C, a mirror M, a CD aperture limiting aperture R and an objective lens OL. Incident. The reflected light from the optical disc D follows the same path as the incident light, returns to the laser coupler, and is received by the first and second photodiodes built in the laser coupler.

In this laser coupler, the first and second photodiodes can be divided as shown in FIG. In this case, the front first photodiode 1
The region d1 of No. 6 and the regions a2 and e2 of the front second photodiode 18 are shared, and the signal d1 is obtained by adding the signals a2 and e2. Further, the region 11 of the rear first photodiode 17 and the region i2 of the rear second photodiode 19 are shared.

FIG. 12A is an explanatory diagram showing a schematic configuration of a laser coupler 1a according to the present embodiment. The laser coupler 1a is loaded in a concave portion of the first package member,
It is sealed by a transparent second package member 3 such as glass.

FIG. 12B is a perspective view of a main part of the laser coupler 1a. For example, a semiconductor block 13 on which a PIN diode 12 as a photodetection element for monitoring is formed is disposed on an integrated circuit substrate 11 which is a substrate obtained by cutting out a single crystal of silicon. First laser diode L as light emitting element
A monolithic laser diode 14a that mounts D3 and the second laser diode LD2 on one chip is arranged.

The laser beam L3 emitted from the first laser diode LD3 is wavelength-converted as L3 ', and then partially reflected on the spectral surface 20a of the prism 20, bends in the traveling direction, and is formed in the second package. The light exits from the exit window in the exit direction, and is irradiated onto an irradiation target such as an optical disk (next generation DVD) via a reflection mirror, an objective lens (not shown), or the like.

The reflected light from the object to be irradiated travels in the direction opposite to the direction of incidence on the object to be irradiated, and enters the spectral surface 20a of the prism 20 from the direction of emission from the laser coupler 1a. While focusing on the upper surface of the prism 20, the light is incident on the front first photodiode 16 and the rear first photodiode 17 formed on the integrated circuit substrate 11, which is the lower surface of the prism 20.

On the other hand, the laser beam L2 emitted from the second laser diode LD2
Is partially reflected on the spectral surface 20a of the first lens, and the traveling direction is bent.
The light exits from the exit window formed in the package in the emission direction,
The light is irradiated onto an irradiation target such as an optical disk (DVD) via a reflection mirror, an objective lens, etc. (not shown).

The reflected light from the object to be irradiated travels in the direction opposite to the direction of incidence on the object to be irradiated, and enters the spectral surface 20a of the prism 20 from the direction of emission from the laser coupler 1a. While focusing on the upper surface of the prism 20, the front second photodiode 18 and the rear second photodiode 18 formed on the integrated circuit substrate 11 serving as the lower surface of the prism 20 are formed.
The light enters the photodiode 19.

As described above, the laser coupler of the present embodiment comprises a laser diode LD3 (oscillation wavelength: 800 nm) for the next generation DVD and a laser diode LD2 for the DVD.
(Oscillation wavelength 650nm), different types of DVD
It is possible to compose a compatible optical pickup that enables reproduction of data. Further, since a monolithic laser diode in which the first laser diode and the second laser diode are mounted on one chip is used, assembly of the optical system is further facilitated.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments.

For example, the light emitting element used in the present invention is not limited to a laser diode, and a light emitting diode (LED) can be used.

The oscillation wavelengths of the first and second laser diodes are not limited to the 800 nm band and the 650 nm band described above, but may be wavelengths employed in other optical disk systems. That is,
Other combinations of optical disc systems, including different types of DVDs and even CDs, using combinations of various wavelengths can be employed. Further, the light having different wavelengths is not limited to two types, and may be more than two types.

The PIN diode for performing the APC control may be formed on an integrated circuit substrate on which the first and second photodiodes are formed. In this case, it is preferable that the configuration of the prism is changed so that a part of the emitted light on the front side of the first and second laser diodes is extracted and coupled to the PIN diode. Reading of the reproduction signal, tracking, and focus error signal may be performed as described with reference to FIG.

Further, as shown in FIG. 13, the laser diode LD3 and LD2 may be separately (ie, discretely) manufactured, and the laser coupler 1b may be configured to mount each of them.

Further, the wavelength conversion element 100 and the coating (R-coat, F-coat) described above can be partially provided on the emission side or the incidence side (that is, only for the wavelength light that requires processing).

[0123]

As described above, according to the present invention, the wavelength conversion element for converting the wavelength of the light is provided on the light emission side of the plurality of light emitting elements. For example, in the case of an optical device or an optical disk device using a two-wavelength laser, the wavelength of emitted light from at least one of the lasers can be easily and effectively reduced without using a special short-wavelength laser. It is possible to increase the density of an information recording medium such as an optical disk.

[Brief description of the drawings]

FIG. 1 is a main part plan view showing a laser light emitting direction of a laser diode according to an embodiment of the present invention.

FIG. 2 is a main part plan view showing a laser light emitting direction of the laser diode according to the embodiment of the present invention.

FIG. 3 is a main part plan view showing a laser beam emission direction of a laser diode according to still another embodiment of the present invention.

FIG. 4 is a perspective view of a main part of a laser diode used in each embodiment of the present invention.

FIG. 5 is a cross-sectional view in a direction perpendicular to the emission direction of laser light from the laser diode.

FIG. 6 is a cross-sectional view showing a method for manufacturing the laser diode in the order of steps.

FIG. 7 is a cross-sectional view showing a method for manufacturing a laser diode in the order of steps.

FIG. 8 is a cross-sectional view showing a method for manufacturing the laser diode in the order of steps.

FIG. 9 is a plan view of a main part of the photodiode (a) DP.
It is a block diagram (b) for explaining a D method.

FIG. 10 is a schematic configuration diagram of an optical pickup using the laser coupler.

FIG. 11 is a plan view of an essential part of a modified example of the photodiode.

FIG. 12A is a perspective view of a package of the laser coupler, and FIG. 12B is a perspective view of the laser coupler.

13A is a perspective view of another package of the laser coupler, and FIG. 13B is a perspective view of the same laser coupler.

FIG. 14 is a schematic configuration diagram of an optical pickup according to a conventional example.

FIG. 15 is a schematic configuration diagram of an optical pickup according to another conventional example.

FIG. 16 is a schematic configuration diagram of an optical pickup already proposed by the present inventors.

FIG. 17 is a perspective view of an essential part of the laser diode.

FIG. 18 is a plan view (a) of a main part showing an emission direction of laser light of the laser diode, and a side view (b) of the main part on the same emission side.
FIG. 9C is a main part plan view (c) showing the emission direction of the laser light from another laser diode.

FIG. 19 is a plan view (a) of a main part of a photodiode and a block diagram (b) for explaining a DPD method.

[Explanation of symbols]

1a, 1b: laser coupler, 11: integrated circuit board, 12
... PIN diode, 13 ... Semiconductor block, 14, L
D1, LD3: first laser diode, 14a: monolithic laser diode, 15, LD2: second laser diode, 16: front first photodiode, 17: rear first photodiode, 18: front second photodiode, 19: rear second photodiode, 20: prism, 20a: spectral surface, E1, E2: laser beam emitting portion, B
S: beam splitter, C: collimator, R: aperture limiting aperture for CD, ML: multi-lens, PD: photodiode, G: grating, M: mirror, OL
... Objective lens, D ... Optical disk, L1 ... First laser beam,
L2: second laser beam, PC: phase comparator, AD: adder, S1a, S1b, S2a, S2b: spot, 10
0: SHG, 200: Optical filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 31/12 H01L 31/12 H H01S 5/022 H01S 5/022 5/0683 5/0683 5/22 610 5/22 610 F term (reference) 2H048 GA13 GA23 GA24 GA48 GA62 2K002 AA05 AB12 BA03 HA20 5D119 AA01 AA04 AA41 BA01 CA10 EC45 EC47 FA09 FA36 JA10 JA29 JA63 JA64 KA02 KA20 LB05 5F073 AA13 AA55 A05 CB05 CA05 CB05 DA05 FA05 FA15 5F089 AA10 AB03 AB17 AC02 AC11 CA15 FA03

Claims (17)

[Claims] 1. An optical device in which a plurality of light emitting elements respectively emitting a plurality of light beams having different wavelengths are arranged side by side in a direction intersecting a light emitting direction. An optical device provided with a wavelength conversion element for converting light. 2. The optical device according to claim 1, wherein a predetermined coating is applied to a light incident surface and / or a light output surface of the wavelength conversion element, so that light of a predetermined wavelength is emitted. . 3. The optical device according to claim 1, further comprising a filter that selectively passes light emitted from the wavelength conversion element according to the wavelength. 4. The optical device according to claim 1, wherein the plurality of light emitting elements and the wavelength conversion element are fixed on a base. 5. The light emitted from the plurality of light emitting elements is guided to a plurality of light receiving elements through an objective lens, respectively.
The optical device according to claim 1. 6. The optical device according to claim 5, wherein the plurality of light emitting elements emit laser beams having different wavelengths from each other. 7. The light emitting device according to claim 5, wherein light emitted from the plurality of light emitting elements is incident on the irradiation target through the objective lens, and reflected light is incident on the plurality of light receiving elements through the objective lens. Optical device. 8. A common light-receiving element, wherein the plurality of light-emitting elements, an optical member for guiding each of these emitted lights to the object to be irradiated, and the reflected light to the plurality of light-receiving elements, and a common light-receiving element The optical device according to claim 7, wherein the optical device is provided on a base and configured as an optical coupler. 9. The optical device according to claim 7, wherein the optical device is configured as an optical pickup of an optical disk device. 10. A plurality of light emitting elements respectively emitting a plurality of light beams having different wavelengths are juxtaposed in a direction intersecting a light emitting direction. An optical disk device provided with a plurality of light receiving elements for receiving light, wherein a wavelength conversion element for converting a wavelength of the light is provided on a light emission side of the light emitting element. 11. A predetermined coating is applied to a light incident surface and / or a light emitting surface of the wavelength conversion element, so that light of a predetermined wavelength is emitted.
An optical disk device according to claim 1. 12. The optical disk device according to claim 10, further comprising a filter that selectively passes light emitted from the wavelength conversion element according to the wavelength. 13. The optical disk device according to claim 10, wherein said plurality of light emitting elements and said wavelength conversion element are fixed on a base. 14. The light emitted from the plurality of light emitting elements,
The optical disk device according to claim 10, wherein the optical disk device is guided to each of the plurality of light receiving elements through an objective lens. 15. The optical disk device according to claim 14, wherein the plurality of light emitting elements emit laser beams having different wavelengths from each other. 16. The light emitting device according to claim 14, wherein the light emitted from the plurality of light emitting elements is incident on the irradiation target through the objective lens, and the reflected light is respectively incident on the plurality of light receiving elements through the objective lens. Optical disk device. 17. The plurality of light emitting elements, an optical member for guiding each emitted light to the disc-shaped information recording medium, and guiding the reflected light to the plurality of light receiving elements, and the light receiving element 17. The optical disk device according to claim 16, comprising an optical coupler provided on a common base.