JP3163184B2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used for information equipment such as an optical pickup.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional optical pickup described above. This optical pickup has a semiconductor laser chip 10, and light emitted from the semiconductor laser chip 10 is applied to a tracking beam generating diffraction grating 1 formed on the back surface of a hologram element 12.
1, the light beam is divided into three light beams, two tracking sub-beams and an information signal reading main beam. Then, the light passes through the hologram element 12 on the upper surface as zero-order light,
After being converted into parallel light by the collimating lens 13, the light is condensed on the disk 15 by the objective lens 14. The reflected light modulated by the pits on the disk 15 is transmitted through the objective lens 14 and the collimator lens 13, then diffracted by the hologram element 12, and guided as a first-order diffracted light onto the five-division photodiode 16. The five-division photodiode 16 and the semiconductor laser chip 10 constitute a semiconductor laser device.

The hologram element 12 is composed of two areas having different grating periods. The reflected light of the main beam is incident on one of the areas and is incident on the dividing line of the photodetectors D2 and D3 and on the other area. The light is collected on the photodetector D4. Further, the reflected light of the sub-beams is
1. Focused on D5. These condensed beams change as shown in FIG. 3 according to the convergence state of the beams on the disk 15. 3A shows a case where the focus is too far, FIG. 3B shows a case where the focus is set, and FIG. 3C shows a case where the focus is too close.

At this time, assuming that the output of each segment of the five-division photodiode 16 is S1, S2, S3, S4, S5, the focus error signal FES is given by FES = S2-S3. On the other hand, a tracking error is detected by a so-called three-beam method. Since the tracking sub-beams are condensed on the photodetectors D1 and D5, the tracking error signal TES is given by TES = S1−S5. The reproduction signal RF is given by RF = S2 + S3 + S4.

That is, in a conventional semiconductor laser device, a five-division photodiode 16 is used in which the above-described photodiodes for detecting the focus signal, tracking signal, and reproduction signal are integrated into one chip. This 5
The divided photodiode 16 is used for the semiconductor laser chip 10
In order to perform a stable operation by generally increasing the signal level, one half of the hologram element 12 other than the one half through which light used for the focus signal of the hologram element 12 passes is provided. Is designed to receive even the light that has passed through. Further, in order to detect the light output of the semiconductor laser chip 10, a photodiode 17 for detecting the light output is provided behind the semiconductor laser chip 10.

[0006]

The light emitting point of the semiconductor laser chip 10 is generally located at the center of the stem 18a on which the semiconductor laser chip 10 and the five-division photodiode 16 are installed. Therefore, if the photodiode for signal detection in the five-division photodiode 16 is placed on one side of the semiconductor laser chip 10, the five-division photodiode 16
And need space on the other side. Therefore, since unnecessary space is generated in the stem 18a, the stem 1
However, the size of the package 8a and the size of the entire package including the stem 18a and the cap 18b set thereon cannot be reduced.

The positional accuracy between the light emitting point of the semiconductor laser chip 10 and the photodiode for signal detection is required to be several μm in length and several tens mrad in angle, but in the conventional optical pickup, the stem 18a is required. A method in which the semiconductor laser chip 10 and the signal photodiode chip are separately die-bonded,
It was very difficult to achieve positional accuracy.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and it is an object of the present invention to provide a semiconductor laser device capable of reducing the size of a stem.

[0009]

A semiconductor laser device according to the present invention irradiates a semiconductor laser chip, a light emitted from the semiconductor laser chip onto a recording medium, and a focus signal and a tracking signal based on the light reflected from the recording medium. A signal detection photodiode for detecting a signal and a reproduction signal, a hologram element provided between the semiconductor laser chip and the recording medium, and a monitoring photodiode for detecting an optical output of the semiconductor laser chip are incorporated. In the semiconductor laser device, the monitor photodiode is provided on the side opposite to the emission side of the semiconductor laser chip, and the signal detection photodiode is provided on both sides of the semiconductor laser chip and the monitor photodiode. the first signal detecting photodiode portion are arranged by dividing each of the second signal It includes a detecting photodiode portion, the hologram element is divided, the reflected light from the recording medium, each of the signal detecting photodiode portions of the first and second signal detecting photodiode portion and it includes two areas you irradiated, both the first signal detecting off <br/> photodiode portion and the second signal detecting photodiode portions of the focus signal based on the knife edge method The monitoring photodiode and the signal detecting photodiode are provided on one chip including a photodiode for performing detection, whereby the above object is achieved.

In one embodiment, the first signal detection signal
Photodiode section and second signal detection photoda
Each of the ion sections receives a sub-beam of the three beams.
Photodiode that illuminates and detects tracking signals
May be included .

[0011]

A signal detecting photodiode for detecting a focus signal, a tracking signal and a reproduction signal is provided on both sides of a monitor photodiode for detecting an optical output of a semiconductor laser chip. Therefore, even if the semiconductor laser chip is set so as to be located at the center of the stem, the signal detection photodiodes are present on both sides of the semiconductor laser chip, and the distance from the semiconductor laser chip to the signal detection photodiodes on both sides is set. Can be shortened.
Further, by integrating the monitoring photodiode and the signal detecting photodiode, the distance can be further reduced. In addition, the hologram element is
Signal detection photodiodes that are divided on both sides of the photodiode.
Two areas to irradiate separately for each of the photodiodes
And divided on both sides of the monitor photodiode
Each of the existing signal detection photodiodes
Focus signal detection based on the edge method
Includes photodiode. Therefore, the focus error detection is set to 2
Focus control that can be performed at a location and has higher accuracy
Can be performed.

Also, on both sides of the monitor photodiode,
Each of the divided photodiodes for signal detection
This receives the sub beam of the three beams and tracks it
If a photodiode that detects the signal is included,
Two hologram elements with photodiode for signal detection
Receives light from the area of
The signal level increases . In addition, when a submount with a semiconductor laser chip is provided on a chip on which a monitor photodiode and a signal detection photodiode are provided, the positional relationship between the semiconductor laser chip and the monitor photodiode and the signal detection photodiode can be improved. It can be kept constant.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a perspective view showing an optical pickup to which a semiconductor laser device according to the present invention is applied. In the illustrated example, the optical pickup is a semiconductor laser device 1 from below.
, A tracking beam generating diffraction grating 5, a hologram element 6, a collimating lens 7, and an objective lens 8. The semiconductor laser device 1 includes a semiconductor laser chip 1
The light emitted from the semiconductor laser chip 1b is divided by the tracking beam generating diffraction grating 5 into three light beams, two tracking sub-beams and an information signal reading main beam. Thereafter, the light passes through the hologram element 6 as the 0th-order light, is converted into parallel light by the collimating lens 7, and is then converted into the disk 9 by the objective lens 8.
Focused on top.

The reflected light modulated by the pits on the disk 9 is diffracted by the hologram element 6 after passing through the objective lens 8 and the collimating lens 7. The diffracted light is transmitted to a plurality of signal detection photodiodes 2a, 2b, 3a, 3b, 3c, 3d, 4a provided on the upper surface of the integrated photodiode chip 1d of the semiconductor laser device 1.
4b is guided as first-order diffracted light. Further, on the upper surface of the integrated photodiode chip 1d, a monitoring photodiode 1e for maintaining the output of light emitted from the semiconductor laser chip 1b at a predetermined value is provided.

[0016] The hologram element 6 is comprised of two areas having different grating periods, the reflected light of the main beam is obtained by entering on one area, and 3 b and the signal detecting photodiodes 3a for detecting a focus signal On the parting line, the one that is incident on the other area detects the focus signal
It is focused on the dividing line between the photodiode for signal detection 3c and 3d. The reflected light of the sub beam is a hologram element.
The light incident on one of the areas 6 is on signal detection photodiodes 2a and 4a for detecting a tracking signal ,
The tracking signal is detected if it is incident on the other area
The light is collected on the signal detecting photodiodes 2b and 4b. These condensed beams change in the same manner as before according to the convergence state of the beam on the disk 9.

The configuration of the semiconductor laser device 1 is as follows. A submount 1c is mounted on the upper surface of the integrated photodiode chip 1d at a position substantially at the center in the longitudinal direction (X direction) and closer to one long side in the width direction (Y direction). The semiconductor laser chip 1b is fixed to the submount 1c. In actual mounting, the submount 1c on which the semiconductor laser chip 1b is mounted is connected to the integrated photodiode chip 1
This is performed by die bonding at the above position d.

A monitoring photodiode 1e is provided below the integrated laser diode chip 1d at the lower portion of the semiconductor laser chip 1b, that is, at a position substantially at the center in the X direction and closer to the other long side. ing. Each signal detection photodiode 2 for detecting a focus signal, a tracking signal, and a reproduction signal is provided on one side with the monitor photodiode 1e and the submount 1c interposed therebetween.
a and 2b, 2a, 3a and 3b, 3c and 3d, 3a and 3b, and 4a and 4b, 4a. On the other side, signal detection photodiodes 2b, 3c, 3d, and 4b are provided.
Further, the integrated photodiode chip 1d having such a configuration
The semiconductor laser chip 1b with the submount 1c is die-bonded above the central position of the semiconductor laser chip 1b.

Therefore, the semiconductor laser chip 1b exists above the central position of the integrated photodiode chip 1d. For this reason, even when the light emitting point of the semiconductor laser chip 1b is arranged at the center of the stem 20a, each signal detecting photodiode 2a for detecting a focus signal, a tracking signal, and a reproduction signal on both sides of the semiconductor laser chip 1b, 2b and the like are divided and exist. Therefore, about half of the area of the integrated photodiode chip 1d is arranged on both sides by half, so that one side can be reduced by half of the integrated photodiode chip 1d. Thereby, as a whole, the size of the stem 20a can be reduced to about half as compared with the case where the photodiode chip is arranged on one side. The integrated photodiode chip 1d includes a monitoring photodiode 1e and signal detection photodiodes 2a, 2b, 3a,
3b, 3c, 3d, 4a and 4b are provided in close proximity and integrally. Thereby, the size of the stem 20a can be further reduced. Further, the stem 20a which can be miniaturized in this way.
Similarly, the cap 20b set on the can be reduced in size.

Further, a focus signal, a tracking signal and a reproduction signal are detected on both sides of the semiconductor laser chip 1b. Therefore, when the focus signal is detected, the light transmitting area of the hologram element 6 is divided into two parts, and an asymmetric semicircular beam is formed on the signal detection photodiode at the time of defocusing. Effects can be used. Also, for that,
Normally, it is sufficient to use only the light passing through one side of the hologram surface divided into two. However, in the present invention, the light passing through the two surfaces is used as a signal detection photo-detector disposed on both sides of the semiconductor laser chip 1b. The light is received by the diode 2a or the like, thereby increasing the light use efficiency and increasing the levels of the reproduction signal, the focus signal, and the tracking signal. In particular, since the signal detection photodiodes 3a and the like for detecting the focus signal are provided on both sides, focus error detection can be performed at two places, and focus control with higher accuracy can be performed.

In the above embodiment, an example is shown in which the semiconductor laser device is applied to an optical pickup. However, the present invention is not limited to this, and it is needless to say that the present invention can be applied to other information devices.

[0022]

As described above in detail, in the case of the present invention, since the signal detecting photodiode for detecting the focus signal and the like is divided on both sides of the monitor photodiode, the semiconductor laser chip is located at the center of the stem. Even if it is set to be located at, the photodiode for signal detection will be present on both sides of the semiconductor laser chip,
The distance from the semiconductor laser chip to the signal detection photodiodes on both sides can be shortened, and the size can be reduced. Further, by integrating the monitoring photodiode and the signal detecting photodiode, the size can be further reduced. Further
And the hologram elements are on both sides of the monitor photodiode.
That of the photodiode for signal detection that exists in
Includes two areas to divide and irradiate, for monitoring
For signal detection that exists separately on both sides of the photodiode
Each photodiode is based on the knife-edge method
Includes photodiode that detects focus signal
Therefore, focus error detection can be performed at two places,
Higher precision focus control can be performed.

Further , on both sides of the monitor photodiode,
Each of the divided photodiodes for signal detection
This receives the sub beam of the three beams and tracks it
If a photodiode that detects the signal is included,
Two hologram elements with photodiode for signal detection
Receives light from the area of
The signal level increases. In addition, when a submount with a semiconductor laser chip is provided on a chip on which a photodiode for signal detection and the like is provided, die bonding can be performed while maintaining a constant positional relationship between the semiconductor laser chip and each photodiode. And the positional accuracy of the photodiode pattern can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an optical pickup to which a semiconductor laser device according to the present invention is applied.

FIG. 2 is a perspective view showing an optical pickup using a conventional semiconductor laser device.

FIG. 3 is an explanatory diagram of a beam shape on a photodiode and each signal in the semiconductor laser device of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser device 1b semiconductor laser chip 1c submount 1d integrated photodiode chip 1e monitor photodiode 2a signal detection photodiode 2b signal detection photodiode 3a signal detection photodiode 3b signal detection photodiode 3c signal detection Photodiode 3d Photodiode for signal detection 4a Photodiode for signal detection 4b Photodiode for signal detection 5 Diffraction grating for tracking beam generation 6 Hologram element 7 Collimating lens 8 Objective lens 9 Disk 20a Stem 20b Cap

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-52487 (JP, A) JP-A-64-86337 (JP, A) JP-A-1-260644 (JP, A) JP-A-2- 79231 (JP, A)

Claims (2)

(57) [Claims] 1. A semiconductor laser chip, and a signal detection photodiode for irradiating a recording medium with light emitted from the semiconductor laser chip and detecting a focus signal, a tracking signal, and a reproduction signal based on the light reflected from the recording medium. A hologram element provided between the semiconductor laser chip and the recording medium, and a monitoring photodiode for detecting an optical output of the semiconductor laser chip. The monitor photodiode is disposed on the opposite side to the first side, and the signal detection photodiode is disposed on both sides of the semiconductor laser chip and the monitor photodiode separately from each other. Photodiode section for signal detection and second signal
It includes a detecting photodiode portion, the hologram element, the reflected light from the recording medium, the photodiode portion and the second signal detection for detecting the first signal
It irradiated by dividing each of the photodiode portion for out
It encompasses two regions, the photodiode portion and the second credit detecting the first signal
Semiconductor lasers neither No. detecting photodiode portion comprises a photodiode for detecting a focus signal based on the knife edge method, the monitoring photodiode and the signal detecting photodiode is provided on one chip apparatus. 2. The photodiode for detecting the first signal.
Unit and that of the second signal detecting photodiode unit
Each of them receives the sub beam of the three beams and tracks it
The semiconductor laser device according to claim 1, further comprising a photodiode that detects a switching signal .