JPH0447984Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention will be explained in the following order.

A. Field of industrial application B. Outline of the invention C. Prior art [Figure 6] D. Problem that the invention attempts to solve E. Means for solving the problem F. Effect G. Example [Figures 1 to 5] H. Effects of the invention (A. Field of industrial application) The present invention relates to a semiconductor laser, and particularly to a semiconductor laser that generates a plurality of laser beams that are controlled independently of each other.

(B. Summary of the invention) The invention provides a semiconductor laser that generates multiple laser beams that are controlled independently of each other.
In order to eliminate crosstalk and improve performance safety, a plurality of photodiodes are formed side by side on the surface of a semiconductor substrate, and a single laser diode or a laser diode having a plurality of light generating sections on one side of the photodiode forming section is formed. A plurality of laser diodes having one light generation section are fixed, and a plurality of light guide grooves are provided on the photodiode forming section for guiding the laser beam from each light generation section to the photodiode corresponding to the light generation section. A beam separator made of a light-shielding material is fixed.

(C. Prior Art) [Fig. 6] In recent years, there has been an increasing need for semiconductor lasers that can generate a plurality of laser beams, for example, three laser beams, which can be controlled separately. This is because read-after-write technology is being developed in recording systems for recording media such as optical disks, and read-after-write technology requires the use of one laser beam each for reading, erasing, and writing. , and each laser beam must be able to be controlled independently of each other.
In addition, a plurality of laser beams that can be independently controlled are also required in multi-track technology for recording AND/OR reading in recording systems for optical disks and the like. Furthermore, as the use of three-beam optical systems in optical pickups is progressing, the need for semiconductor lasers that generate multiple laser beams is gradually increasing.

FIG. 6 shows an example of a semiconductor laser developed to meet this need. The semiconductor laser is constructed by growing a semiconductor layer on one n-type semiconductor substrate a made of GaAs to form a double heterostructure diode, and etching a separation groove c deeper than the active layer b on the surface of the diode. The surface of the semiconductor substrate a is divided into a laser diode formation region d and a photodiode formation region e by a separation groove c, and three laser diodes LD1, LD2, and LD3 are formed in the laser diode formation region d, and a photodiode formation region d is formed. Three photodiodes PD1, PD2, PD3 are formed in the diode formation region e, and each laser diode LD1, LD2,
The light generating section of LD3 and each photodiode PD1,
The light generating portions of PD2 and PD3 face each other with a separation groove c in between. f, f, ... are stripes,
Each laser diode LD1, LD2, LD3 receives an independent drive voltage, and each photodiode
PD1, PD2, and PD3 each independently output a photodetection signal.

The distance between each photodiode is about 100 μm, and the three laser beams emitted from the end faces of the laser diodes LD1, LD2, and LD3 on the side opposite to the photodiodes can be optically processed by one focusing lens.

(D. Problems to be Solved by the Invention) By the way, the semiconductor laser shown in FIG. 6 has a problem in that crosstalk occurs. That is,
The laser beam emitted from a laser diode, for example LD1, is the laser diode laser LD1.
must be monitored by the photodiode PD1 corresponding to the photodiode PD1, but part of it is incident on the PD2 adjacent to the photodiode PD1, and the laser output from the laser diode LD2 Since a portion of the beam is incident, it is not possible to control the output of each laser diode LD1, LD2, and LD3 completely independently and with high precision.

Further, although the original laser beam is emitted from the cleavage plane, the separation groove c can only be formed by etching, so the etched plane becomes the emission end face of the monitoring laser beam. However, unlike a cleavage plane, an etched surface is inherently unreliable as a laser beam emission end face, and has the disadvantage that its properties tend to fluctuate due to the concentration of output on the end face when using a semiconductor laser, resulting in problems. I was getting used to it.

The present invention has been devised to solve these problems, and aims to stabilize the performance by eliminating crosstalk between semiconductor lasers that can be controlled independently of each other.

(E. Means for Solving Problems) In order to solve the above problems, the semiconductor laser of the present invention has a plurality of photodiodes arranged side by side on the surface of a semiconductor substrate, and a plurality of photodiodes are formed on one side of the photodiode forming part. A laser diode having a light generating section or a plurality of laser diodes having one light generating section is fixed, and a laser beam from each light generating section is directed onto the photodiode forming section so as to correspond to the light generating section. The device is characterized in that a beam separator made of a light-shielding material and provided with a plurality of light guide grooves that guide light to the photodiode is fixed.

(F Effect) According to the semiconductor laser of the present invention, a plurality of monitoring photodiodes are formed on one surface portion, and a laser diode is fixed to one side of the photodiode formation portion, so that it can be cleaved as a laser diode. An ordinary type that emits a monitoring laser beam from a surface can be used. Therefore, it is possible to stabilize the performance with less deterioration than the conventional semiconductor laser shown in FIG. 6 which emits a laser beam from the etched surface.

In addition, a beam separator blocks light between the photodiodes, and each laser beam from each light generating section is guided to the photodiode corresponding to that light generating section through a light guiding groove, effectively and reliably reducing crosstalk. It can be prevented.

(G Embodiment) [FIGS. 1 to 5] The semiconductor laser of the present invention will be described in detail below according to the illustrated embodiment.

1 to 3 show one embodiment of the semiconductor laser of the present invention, FIG. 1 is an exploded perspective view, and FIG. 2 is a cross-sectional view of the photodiode forming portion of the semiconductor substrate (see FIG. 2-2 line),
FIG. 3 is a cross-sectional view (a cross-sectional view taken along line 3--3 in FIG. 1) of the laser diode fixing portion of the semiconductor substrate.

In the drawing, 1 is a semiconductor substrate made of silicon Si, 2 is a photodiode forming part, and this part 2
3 photodiodes PD1, PD2, PD inside
3 is formed. Reference numeral 3 denotes an end face of the semiconductor substrate 1 on the front side (the side from which the original laser beam is emitted).

A multi-laser diode 4 is soldered onto the surface of the semiconductor substrate 1 at the diagonally upper right side of the photodiode forming portion 2 in FIG. The multi-laser diode 4 is formed by growing an appropriate semiconductor layer on the surface of an n-type semiconductor substrate 5 made of GaAs to form a diode with a double heterostructure.
Three stripes 6, 6, 6 extending in the width direction of the semiconductor substrate 5 are provided on the surface at equal intervals. 7
is the active layer. And stripes 6, 6, 6
Above photodiodes PD1, PD2, PD3 below
Compatible laser diodes LD1, LD2, LD
3 is formed. Then, the multi-laser diode 4 has the surface on which the stripes 6, 6, 6 are formed facing downward, and the photodiode forming portion 2 is connected to the multi-laser diode 4 on that surface.
It is soldered on top.

8 is a beam separator made of silicon Si, for example, and light guiding grooves 9, 9, 9 extending in the width direction thereof are formed on the lower surface of the beam separator.
9 is positioned on the extension line of the stripes 6, 6, 6 of the multi-laser diode 4, and is soldered onto the photodiode forming portion 2. 10, 10, . . . are metal films formed on the lower surface of the beam separator 8 for soldering, and the metal films 10, 10, . It is attached.

Next, according to FIGS. 2 and 3, the semiconductor substrate 1
Explain the internal structure of. First, the cross-sectional structure of the photodiode forming portion 2 shown in FIG. 2 will be explained.

12 is an n ^- type semiconductor layer formed on the surface of the n ⁺ type semiconductor substrate 1, and 13, 13, . . . are n ⁺ type isolation layers formed on the surface of the semiconductor substrate 1 to separate each photodiode. It is formed deeper than the n ^- type semiconductor layer 12 described above. 14,14,1
Reference numeral 4 denotes a p ⁺ -type semiconductor region selectively formed on the surface of the n ^- -type semiconductor layer 12 in a region surrounded by the n ⁺ -type isolation layers 13, 13, . . . , 14, 14, the n ^- type semiconductor layer 12, and the substrate 1 constitute a PIN type photodiode. 11, 11, . . . are the aforementioned solder layers, and 15, 15, . . . are their base films.

Next, the laser diode fixing portion shown in FIG. 3 will be explained. 16, 16 is n ^- type semiconductor layer 1
The p ⁺ -type semiconductor region is selectively formed on the surface portion of the p + -type semiconductor region 2 and can be formed simultaneously with the p ⁺ -type semiconductor regions 14, 14, . . . . 17, 17 are n which are selectively formed on the surface portions of the semiconductor regions 16, 16.
The semiconductor regions 17, 17 are junction-separated regions from the semiconductor substrate 1.
Note that 13a is an n ⁺ point for electrically connecting the stripe of the laser diode LD2 to the semiconductor substrate 1.
This is a type semiconductor layer and is formed simultaneously with the isolation layer 13. 18, 18, 18a are semiconductor regions 17, 17, and a base film 19 is provided on the surface of the semiconductor layer 13a.
This is a solder layer formed through the solder layer 1.
8, 18, 18a, each stripe 6, 6, 6 of the multi-laser diode 4 is connected to the semiconductor region 1.
7, 17, and are connected on the semiconductor layer 13a.

The film 19 underlying the solder layers 18, 18 extends to the bonding pad portions 20, 20. The laser diodes LD1 and LD3 are driven by applying a driving voltage between the bonding pad parts 20 and 20 and the surface (back surface) of the multi-laser diode 4 on the side opposite to the stripe. Further, the laser diode LD2 is connected to the semiconductor substrate 1,
It is driven by applying a driving voltage between the multi-laser diode 4 and the surface (back surface) on the side opposite to the stripe. A connect line is bonded to the surface of the multi-laser diode 4 on the side opposite to the stripe.

In addition, 21, 21, 21 are each photodiodes.
This is a bonding pad for bonding the connect wires connected to the P-side electrodes of PD1, PD2, and PD3.

The illustrated semiconductor laser can generate a monitoring laser beam from the cleavage plane 22 of the multi-diode 4 like a normal laser diode, and can generate a monitoring laser beam from the etched plane like the conventional semiconductor laser shown in FIG. There is no restriction that a monitoring laser beam must be emitted. Therefore, there is less risk of deterioration due to power concentration on the laser beam emitting end face, and performance stability is increased.

The photodiodes PD1, PD2, and PD3 are separated by a beam separator 8, and the laser beams output from the laser diodes LD1, LD2, and LD3 are connected to the respective laser diodes by light guide grooves 9, 9, and 9, respectively. Light can be guided to corresponding photodiodes PD1, PD2, and PD3. Therefore, crosstalk can be effectively and reliably prevented by the beam separator 8.

Since the beam separator 8 is made of silicon Si having light absorption properties, the monitoring laser beams emitted from the laser diodes LD1, LD2, and LD3 are reflected by the beam separator 8, and the laser beams emitted from the laser diodes LD1, LD2, and LD3 are
It is possible to prevent the amount of return light returning to the third side from increasing unnecessarily.

In the beam separator 8 in the above embodiment, the light guide grooves 9, 9, 9 are formed by isotropic etching, but the light guide grooves may be formed by anisotropic etching. Then, the end of the light guide groove on the side opposite to the laser diode may be closed. FIGS. 4A and 4B show an example 8a in which the beam separator is modified in this way. FIG. 4A is a cross-sectional view, and FIG. 4B is a front view. It is a closed surface. In this way, the light can pass through the light guide groove and be connected to the photodiode.
It is possible to eliminate unnecessary monitoring laser beams that are not received by the PD.

Incidentally, the light guide groove 9b having a rectangular cross section may be formed by half-cutting using a saw instead of etching as shown in FIG. In this way, the beam separator 8 can be relatively easily
b can be obtained.

Further, in the above embodiment, a multi-laser diode in which a plurality of laser diodes were integrated was fixed on the semiconductor substrate 1, but separate laser diodes LD1, The LD2 and LD3 may be fixed onto the semiconductor substrate 1.

(H Effect of the invention) As stated above, the semiconductor laser of the invention has the following effects:
One laser diode or one light beam, in which a plurality of photodiodes are formed side by side on a surface portion of a semiconductor substrate, and a plurality of light generating portions are driven separately from each other on one side of the photodiode forming portion on the surface portion. A plurality of laser diodes each having a light-emitting part are fixed on the semiconductor substrate so that each light-generating part faces each photodiode, and one main surface made of a light-shielding material is placed on the photodiode forming part of the surface part. A beam separator has a plurality of light guide grooves on the light guide groove forming surface so that the laser beam from each light generating part can be guided by the light guide groove to a photodiode corresponding to the light generating part. It is characterized by being fixed.

Therefore, according to the semiconductor laser of the present invention, a plurality of monitoring photodiodes are formed on one surface portion, and a laser diode is fixed to one side of the photodiode formation portion, so that the cleavage plane can be used as a laser diode. An ordinary type of device that emits a monitoring laser beam can be used. Therefore, it is possible to stabilize the performance with less deterioration than the conventional semiconductor laser shown in FIG. 6 which emits a laser beam from the etched surface.

In addition, a beam separator blocks light between the photodiodes, and each laser beam from each light generating section is guided to the photodiode corresponding to that light generating section through a light guiding groove, effectively and reliably reducing crosstalk. It can be prevented.

[Brief explanation of the drawing]

Figures 1 to 3 are for explaining one embodiment of the semiconductor laser of the present invention, with Figure 1 being an exploded perspective view and Figure 2 showing a cross-sectional structure of a photodiode forming portion of a semiconductor substrate. 2-2 in Figure 1 of
3 is a sectional view taken along line 3-3 of FIG. 1 showing the cross-sectional structure of the laser diode fixing portion of the semiconductor substrate, and FIGS. 4A and 4B show modified examples of the beam separator. Figure A is a sectional view, Figure B is a front view, Figure 5 is a front view showing another modification of the beam separator, and Figure 6 is a perspective view of a conventional example. Explanation of symbols, 1... Semiconductor substrate, 2... Photodiode forming section, 4... (multi) laser diode, 6... Light generating section, 8... Beam separator, 9... Light guide groove, PD... photodiode,
LD...Laser diode.

Claims (1)

[Claims for Utility Model Registration] A plurality of photodiodes are formed side by side on a surface portion of a semiconductor substrate, and a plurality of light generating portions that are driven separately from each other are provided on one side of the photodiode forming portion on the surface portion. One laser diode or a plurality of laser diodes each having one light generating part are fixed on the semiconductor substrate so that each light generating part faces each photodiode, and a light shielding plate is placed on the photodiode forming part of the surface part. The beam separator is made of a transparent material and has a plurality of light guiding grooves on one main surface, so that the laser beam from each light generating part can be guided by the light guiding grooves to a photodiode corresponding to the light generating part. is fixed to the light guide groove forming surface. A semiconductor laser characterized by: