JP2001053380A - Semiconductor laser module and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a semiconductor laser module having high controllability of a normalization coupling coefficient by electrically connecting an electrode of one semiconductor laser section out from among a plurality of those sections to an electrode terminal using a connection means. SOLUTION: A semiconductor chip 10 finds a normalization coupling coefficient from the spectrum of laser light emitted from each semiconductor laser section 11 and specifies a semiconductor laser section 11, whose normalization coupling coefficient agrees with or is closest to the designed value. Thereafter, the semiconductor chip 10 is mounted in side the main body 2 of a package with an electrode terminal and then an upper electrode 132 of the specified semiconductor laser section 11 and the electrode terminal 6 is connected electrically by a connection means, for example, a wire 27. At this time, the semiconductor chip 10 is positioned with respect to a lens 22 and then is fixed to the main body 2 of the package. Thereafter, a cover 3 is installed on the main body 2 of the package so as to enable completion of a distributed feedback semiconductor laser module.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser module and a method of manufacturing the same. A technology that is effective when applied to technology.

[0002]

2. Description of the Related Art In a wavelength division multiplexing (WDM) optical transmission system, a plurality of semiconductor laser devices having different wavelengths are used. A semiconductor light emitting device used for the wavelength multiplexing method is described in Japanese Patent Application Laid-Open No. 7-226563. This document describes a plurality of distributed feedback (DFB) semiconductor lasers and distributed Bragg reflection (DBR) semiconductor lasers having uniform static characteristics and dynamic characteristics and different oscillation wavelengths.

[0003] In addition, the Institute of Electronics, Information and Communication Engineers, “Journal of the Institute of Electronics, Information and Communication Engineers” March 1987, March 25, pp. 369-P3
No. 78 discloses a high power single longitudinal mode (SLM) distributed feedback laser in which the coupling strength κL by the diffraction grating is 1 or 1.2. In addition, the κL
Is 1, the reflectivities of the output end face and the rear end face of the semiconductor laser are 1% and 90%, respectively.

[0004] Also, "Advanced Optical Electronics Series 2 Basics of Semiconductor Lasers" published by Kyoritsu Shuppan Co., Ltd., published on March 25, 1998, P206-P207, states that the diffraction grating depth is proportional to the coupling coefficient κ. I have.

[0005]

SUMMARY OF THE INVENTION In a distributed feedback semiconductor laser (DFB-LD) used for optical fiber communication,
Single mode oscillation (dynamic single mode oscillation) is very important.

[0006] A distributed feedback semiconductor laser has a diffraction grating as a light distributed feedback structure, and its characteristics depend on the end face phase of the diffraction grating (grating). The end face phase of the diffraction grating cannot be controlled because the end face of the semiconductor laser (semiconductor laser chip) is formed by cleaving the compound semiconductor substrate, and whether or not the distributed feedback semiconductor laser satisfies the characteristics is determined by the diffraction grating. Is a probabilistic discussion about the end face phase of

On the other hand, the normalized coupling coefficient κL, which is a structural parameter of a distributed feedback semiconductor laser, is the parameter that has the greatest effect on the product yield, but the depth of a diffraction grating formed by wet etching is several nm. It is necessary to control with precision, and it is very difficult to control the normalized coupling coefficient κL.

An object of the present invention is to provide a distributed feedback semiconductor laser module that can enhance the controllability of the normalized coupling coefficient κL.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0010]

The following is a brief description of an outline of typical inventions disclosed in the present application.

(1) A package with electrode terminals and a plurality of distributed feedback semiconductor lasers arranged in the package and having mutually different normalized coupling coefficients κL which are products of the coupling coefficient κ and the length L of the diffraction grating region. A semiconductor chip having monolithically formed portions in parallel, an optical fiber extending inside and outside the package, and each of the semiconductor lasers interposed between an inner end of the optical fiber and an emission surface of the semiconductor chip. A lens for condensing the laser light emitted from the portion into the optical fiber, and a connecting means for electrically connecting an electrode of one of the plurality of semiconductor laser portions to the electrode terminal. . The normalized coupling coefficient of each of the plurality of semiconductor laser units has a stepwise changed value, and the design normalized coupling coefficient is substantially halfway between the stepwise changed normalized coupling coefficients. The lengths of the diffraction gratings of the respective semiconductor laser portions are different from each other.

Such a semiconductor laser module is manufactured by the following method. Mounting a semiconductor chip having a semiconductor laser portion in a package with electrode terminals, electrically connecting electrodes of the semiconductor laser portion and the electrode terminals by connecting means, extending over the inside and outside of the package A method for manufacturing a semiconductor laser module comprising a step of optically connecting an inner end of an optical fiber attached to a semiconductor laser portion of the semiconductor chip directly or through a lens, wherein a semiconductor substrate is prepared. Forming a semiconductor chip in which a plurality of semiconductor laser sections each including a distributed feedback semiconductor laser having a different normalized coupling coefficient on a main surface of a semiconductor substrate are formed in parallel; and a laser beam emitted from each of the semiconductor laser sections. Measuring the semiconductor laser unit that matches the design value or most closely matches the design value; A step of electrically connecting the electrode of the specified semiconductor laser unit and the electrode terminal by connecting means after mounting the chip in a package with electrode terminals, and connecting the inner end of the optical fiber directly or through a lens to the semiconductor. Optically connecting to a semiconductor laser portion of the chip.

(2) In the configuration of the means (1), the depths of the diffraction gratings of the respective semiconductor laser portions are different from each other.

(3) In the configuration of the means (1) or (2), the semiconductor chip is provided with a modulator for controlling laser oscillation of each semiconductor laser unit.

In the semiconductor laser module of the present invention, when the distributed feedback semiconductor laser section is formed on the semiconductor substrate in the manufacture of the semiconductor laser module of the means (1) or (2), the respective semiconductor laser sections are formed. The modulators to be controlled are simultaneously formed.

(4) In the configuration of the means (1) or the means (2) or the means (3), the semiconductor chip is arranged in the package via an electronic cooling element. That is, the electronic cooling element is directly fixed to the package, and the semiconductor chip is fixed on the electronic cooling element.

According to the semiconductor laser module manufacturing method of the means (1), (2) or (3), after the electronic cooling element is mounted in the package with the electrode terminals, The semiconductor chip is mounted on the electronic cooling element, and at the time of connection by the connecting means, the electrode of the electronic cooling element and the electrode terminal are electrically connected by the connecting means.

According to the means (1), (a) a plurality of distributed feedback semiconductor laser sections having different normalized coupling coefficients κL are formed monolithically in parallel on a semiconductor substrate, and then each semiconductor laser section is formed. Measuring the normalized coupling coefficient of the semiconductor laser part which matches or most closely matches the design value, and then connects the electrode and the electrode terminal of the specified semiconductor laser part by connecting means, and Since the module is manufactured, a distributed feedback semiconductor laser module that oscillates in a single mode can be provided at a high yield and at a low cost.

(B) The length of the diffraction grating of each semiconductor laser portion is different, and the normalized coupling coefficient of each semiconductor laser portion is gradually changed by the difference in the length of the diffraction grating.

According to the means (2), since the depths of the diffraction gratings of the respective semiconductor laser portions are different from each other, and thereby the normalized coupling coefficients are different from each other, the means (1) Has the same effect as the effect of the configuration described above.

According to the means (3), in addition to the effect of the means (1), each semiconductor chip is provided with a modulator for controlling the laser oscillation of each semiconductor laser section. It becomes possible to control the oscillation of the laser light of the laser section.

According to the means (4), in addition to the effects of the means (1) and (3), since the temperature of the semiconductor chip is controlled by the electronic cooling element, the semiconductor chip can be stabilized at a predetermined oscillation wavelength. One mode oscillation can be performed.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

(Embodiment 1) FIGS. 1 to 9 relate to a semiconductor laser module according to an embodiment (Embodiment 1) of the present invention.

The semiconductor laser module 1 of the first embodiment
As shown in FIG. 2, the device has a structure including a package 4 composed of a package body 2 and a lid 3, and an optical cable 5 (optical fiber) extending inside and outside the package 4. .

A plurality of electrode terminals (leads) 6 are arranged on both sides of the package body 2 to form a package with electrode terminals. These leads 6 extend inside and outside the package body 2.

On the upper surface of the center of the package body 2,
The semiconductor chip 10 is fixed via the submount 7. As shown in FIG. 1, a plurality of semiconductor laser units 11 each composed of a distributed feedback semiconductor laser (DFB-LD) are monolithically formed on the semiconductor chip 10 in parallel to form a laser array structure.

In the first embodiment, the normalized coupling coefficient κL, which is the product of the coupling coefficient κ of each semiconductor laser section 11 and the length L of the diffraction grating region, is different from each other.

In the first embodiment, the length L of the diffraction grating region (length of the diffraction grating region) of the normalized coupling coefficient κL is made different in each semiconductor laser unit 11 to change the normalized coupling coefficient κL. ing.

In the first embodiment, the length (diffraction grating region length) L of the diffraction grating (grating) region of each semiconductor laser section 11 is different from each other.

In the first embodiment, although this is not particularly limited, four semiconductor laser units 11 are formed as LD1 to LD4. The lengths of the diffraction grating (grating) regions are different from each other. In FIG. 1, the area inside the thick line frame is the area where the diffraction grating is formed, and no diffraction grating is formed in the area outside the thick line frame. In addition, each LD
The region sandwiched between the two narrow lines at the center becomes an optical waveguide (waveguide) 41.

The length of the diffraction grating region is longest at L1 in the case of LD1, and shortest at L4 in the case of LD4, and the mutual relationship is L1>L2>L3> L4. For example, the diffraction grating region length is L1 = 300 μm for LD1, and L2 is L2 for LD2.
= 267 μm, LD3 is L3 = 233 μm, LD4 is L
4 = 200 μm. The diffraction grating pitch is 24
0 nm.

In the case of the first embodiment, the design oscillation wavelength is LD
2 and the oscillation wavelength of the LD 3. Specifically, the length L2 of the diffraction grating region in the normalized coupling coefficient κL of LD2 and the normalized coupling coefficient κL of LD3
Is set to the middle of the length L3 of the diffraction grating region.

On the other hand, the coupling coefficient κ of the normalized coupling coefficient κL depends on the depth of the diffraction grating.
Becomes larger. The diffraction grating is formed by wet etching, and the depth of the diffraction grating varies by about ± 10 nm due to the wet etching.

In the first embodiment, in order to define a region where a diffraction grating is to be formed, the length of the diffraction grating region is defined by a photolithography technique and a mask made of an SiO ₂ film formed by etching. This variation in the diffraction grating region length depends on the fabrication variation of the mask, and is, for example, ± 1.
It becomes about μm.

Therefore, in the first embodiment, an intermediate value between the oscillation wavelength of LD2 and the oscillation wavelength of LD3 is set as the design oscillation wavelength,
Even if there is a variation in the depth of the diffraction grating and a variation in the length of the diffraction grating region, the normalized coupling coefficient in any one of the LDs LD1 to LD4 matches or approximates the design standardized coupling coefficient. To do.

On the other hand, in the semiconductor chip 10, the upper electrode 12 is provided on the upper part, and the lower electrode 1 is provided on the lower part.
3 are provided (see FIGS. 1 and 3).

The upper electrode 12 is connected to each of the semiconductor laser sections 1.
1, respectively. In the first embodiment, the number of the semiconductor laser portions 11 is four, and therefore, the four upper electrodes 12 are also provided independently. Lower electrode 13
Is fixed on the conductive layer 14 of the submount 7 via a bonding material (not shown). The submount 7 is also mounted on the package body 2 via an adhesive (not shown) having good heat conductivity.
It is fixed to.

The optical cable 5 (optical fiber) is inserted into a guide pipe 20 provided through the package body 2 and is fixed by a bonding material (not shown). The tip of the optical cable 5 is optically connected to the isolator 21. A lens 22 is arranged between the isolator 21 and the emission surface of the semiconductor chip 10.

Further, in the semiconductor chip 10 of the first embodiment, the electrode (upper electrode 12) of the single semiconductor laser unit 11 is connected to the electrode terminal 6 by an electrical connection means, for example, a wire 27. Therefore, wire 2
Only the semiconductor laser unit 11 connected by the laser 7 oscillates, and the light (laser light) 16 (see FIG. 3) emitted by the laser oscillation is transmitted to the lens 22 and the isolator 21.
Through the optical cable 5 and taken into an optical fiber (not shown) located at the center of the optical cable 5.

A light receiving element 26 is fixed to the package body 2 via a submount 25. The electrode of the light receiving element 26 and the submount 25 are electrically connected to each lead 6 via a wire 27. That is, the upper electrode of the light receiving element 26 is electrically connected to the lead 6 by the wire 27 directly connected, and the lower electrode is electrically connected to the lead 6 by the wire 27 connected to the submount 25. ing.

The semiconductor chip 10 has a structure as shown in FIGS. FIG. 4 is an enlarged view of a portion A in FIG. 3, and FIG. 5 is an enlarged view of a portion B in FIG.

As shown in these figures, the semiconductor chip 1
Numeral 0 has a multilayer semiconductor layer including an active layer on the main surface of the semiconductor substrate 30, and has an upper electrode 12 on the upper side and a lower electrode 13 on the lower side.

The semiconductor substrate 30 is made of, for example, n-InP
A substrate 30 is formed on the n-InP substrate 30.
GaAsP waveguide layer 31 (0.15 μm thick), InGaAs
sP / InGaAsP strained MQW active layer 32 (0.1 μm
Thickness), p-InGaAsP waveguide layer 33 (0.15 μm
Thickness), p-InP cladding layer 34 (2.0 μm thickness), p
-InGaAs contact layer 35 (0.25 μm thick) is sequentially laminated.

The p-InGaAs contact layer 35 and the p-InP clad layer 34 are selectively etched away to form a mesa stripe 38 (see FIG. 4). In addition, p-InGaAs other than the mesa stripe is used.
The s-contact layer 35, the p-InP cladding layer 34, and the p-InGaAsP waveguide layer 33 are covered with an insulating film 36. The upper electrode 12 has a structure in which it electrically contacts the p-InGaAs contact layer 35 on the surface of the mesa stripe.

The portion including each mesa stripe becomes the semiconductor laser unit 11. In the first embodiment, four semiconductor laser units 11 are formed monolithically in parallel.

When a predetermined voltage is applied to the upper electrode 12 of each semiconductor laser section 11 and the lower electrode 13 serving as a common electrode,
InGaAsP / corresponding to the p-InP cladding layer 34
InGaAsP strained MQW active layer 32 and its upper and lower p
The laser oscillation is performed with the -InGaAsP waveguide layer 33 and the n-InGaAsP waveguide layer 31 serving as an optical waveguide. Then, the end face of the semiconductor chip 10, that is, the cleavage plane formed by the cleavage of the n-InP substrate 30 becomes the emission plane, and the laser light 16
Is emitted (see FIG. 3).

Semiconductor chip 10 having a width of 300 to 400 μm
In the case of (1), when the size of the electrode pad for connecting the wire 27 is 80 μm square, four mesa stripes for forming the optical waveguide can be formed.

As shown in FIG. 5, the semiconductor substrate 30 and the n-
The pitch between the InGaAsP waveguide layer 31 and the InGaAsP waveguide layer 31 is 240
A diffraction grating (grating) 37 having a thickness of nm is provided.

As described above, the length of the diffraction grating 37 is 300 μm for L1, 267 μm for L2, and 233 μm for L3.
m and L4 are formed to 200 μm.

FIG. 9 is a graph showing the correlation between the normalized coupling coefficient κL and the single mode yield (Sr: side mode suppression ratio). The graph is a graph derived as a result of the study by the present inventor.
The reflectance of the front emission surface of 0 is 0% (AR film 0%),
This is the case where the reflectivity of the rear emission surface is 90%.

As can be seen from the graph of FIG. 9, the single mode yield is 6 at the portion where κL is from 1.0 to 1.5.
It shows the highest value of about 5%.

Therefore, the present inventor has aimed at setting κ as the range in which the single mode yield is the highest.
L = 1.25 ± 0.25. In this case, the depth of the diffraction grating is 30 nm, and L = 250 μm. The diffraction grating region length is LD1 L1 = 300 μm, LD1
2 is L2 = 267 μm, LD3 is L3 = 233 μm, L
D4 was set to L4 = 200 μm.

As described above, it is difficult to control the depth of the diffraction grating, and there is only controllability of about ± 10 nm. When the diffraction grating depth is the shallowest, it is 20 nm. Since the coupling coefficient κ is substantially proportional to the depth of the diffraction grating, when the depth of the diffraction grating is 20 nm, κL for L = 250 μm is 1.25 × 20 /
30 = 0.83, but κL of L = 300 μm (LD1) is 1.25 × 20/30 × 300/250 = 1.0
Becomes

When the depth of the diffraction grating is the deepest, 40
nm. Since the coupling coefficient κ is substantially proportional to the depth of the diffraction grating, when the depth of the diffraction grating is 40 nm, L = 250
The κL for μm is 1.25 × 40/30 = 1.67, while the κL for L = 200 μm (LD4) is 1.25 ×
40/30 × 200/250 = 1.33, and even when the diffraction grating depth is 30 ± 10 nm, κL = 1.25 ±
0.25 can be realized.

Therefore, by setting the design value in the middle of the four semiconductor laser portions 11 where the oscillation wavelength changes stepwise, the variation due to the etching of the diffraction grating depth and the length of the diffraction grating can be reduced. The oscillation wavelength of any one of the semiconductor laser units 11 can be a numerical value that matches or approximates the designed oscillation wavelength, including manufacturing variations.

Therefore, after manufacturing the semiconductor chip 10,
The wavelength of the laser beam 16 emitted from each semiconductor laser unit 11 is measured, the semiconductor laser unit 11 having the wavelength closest to the design value is specified, and the semiconductor chip 10 is attached to the package body 2.
At the time of assembling, the specified electrode (upper electrode 12) of the semiconductor laser unit 11 is connected to the electrode terminal 6 attached to the package body 2 via the wire 27 so that only the specified semiconductor laser unit 11 oscillates. To

Further, as shown in FIG. 1, the semiconductor chip 10 has cleavages 15 at both ends of the optical waveguide. This is to prevent the longest part of the diffraction grating region length from changing due to variations in the cleavage of the crystal.

Next, a method of manufacturing the semiconductor chip 10 will be described with reference to FIGS.

First, after preparing a semiconductor substrate 30 made of an n-InP substrate, as shown in FIG.
An SiO ₂ film is selectively formed on the upper surface of the substrate, a region where a diffraction grating is formed is exposed, and a region where no diffraction grating is formed is
It is covered with a mask 40 made of an O ₂ film.

At this stage, the waveguide 41 has not been manufactured yet, but for convenience of explanation, FIG. 6 shows the waveguide 41. These waveguides 41 form waveguides of LD1 to LD4. In the first embodiment, the length L1 of the diffraction grating of each LD depends on the pattern of the mask 40.
To L4 are sequentially changed in a stepwise manner. That is, the length L1 of the diffraction grating of the LD1 is the longest, the length L4 of the diffraction grating of the LD4 is the shortest, the diffraction grating length L1 is 300 μm,
L2 is 267 μm, L3 is 233 μm, L4 is 200 μm
m.

Thus, the normalized coupling coefficient κL of LD1 to LD4 can be changed mutually. κL is, for example, 1.50 in the LD1 (L1) portion, and 1.K in the LD2 portion.
34, 1.17 for LD3 part, 1.0 for LD4 part
0.

The semiconductor substrate 30 has a large shape in actuality, and a large number of semiconductor chips can be manufactured at one time. However, for convenience of explanation, a description will be given in a state where two adjacent semiconductor chips are formed.

Next, as shown in FIG.
After the photoresist film 42 is formed on the entire upper surface of the semiconductor substrate 30, a diffraction grating pattern of the resist is formed on the entire surface of the semiconductor substrate 30 by an interference exposure method. 240n diffraction grating pitch
m.

Next, after the photoresist film 42 is developed, wet etching is performed using the photoresist film 42 as a mask to form a diffraction grating 37 as shown in FIG. By this wet etching, a diffraction grating 37 is formed in a portion not covered by the mask 40, and the mask 4
No diffraction grating is formed in the area covered by zero. After that, the photoresist film 42 and the mask 40 are removed.

In FIG. 8, the area where the horizontal line is finely inserted is the area where the diffraction grating 37 is present, and the blank area is the area where there is no diffraction grating.

Next, although not shown, the semiconductor substrate 30 is formed by MOCVD (metal organic chemical vapor deposition) or the like.
The n-InGaAsP waveguide layer 31 (0.15 μm)
m), InGaAsP / InGaAsP strained MQW active layer 32 (0.1 μm thick), p-InGaAsP waveguide layer 3
3 (0.15 μm thick), p-InP cladding layer 34
(2.0 μm thick), p-InGaAs contact layer 35
(Thickness: 0.25 μm) to form a multilayer semiconductor layer.

Since the subsequent steps are the same as the conventional method, the description will be made without using a new figure.

After forming the multi-layer semiconductor layer, the mask 4
0 is removed, and then four mesa stripes are formed in the unit semiconductor chip. That is, the p-InGaAs contact layer 35 and the p-InP cladding layer 34 are selectively etched and removed by a common photolithography technique and an etching technique to form a mesa stripe 38 (see FIG. 4).

Next, an insulating film 36 is selectively provided on the upper surface side of the semiconductor substrate 30, and the p-InG
The upper electrode 12 is formed on the aAs contact layer 35.
Also, after removing the back surface of the semiconductor substrate 30 by a predetermined thickness to reduce the thickness, the lower electrode 13 is formed on the back surface of the semiconductor substrate 30, and then the semiconductor substrate 30 is divided vertically and horizontally.
Then, a semiconductor chip 10 as shown in FIG. 3 is formed.

In the division, the semiconductor crystal is cleaved in a direction perpendicular to the optical waveguide, and the cleaved surface is used as an emission surface for emitting the laser light 16.

In such a semiconductor chip 10, a normalized coupling coefficient is obtained from the spectrum of the laser light emitted from each semiconductor laser unit 11, and the semiconductor laser unit 11 that matches or most closely matches the design value is determined. Identify. Then, after mounting the semiconductor chip 10 in the package body 2 with electrode terminals as shown in FIG. 2, the electrode (upper electrode 12) of the specified semiconductor laser unit 11 and the electrode terminal 6 are connected to the wire 27 (connection). Means) for electrical connection. At this time, the semiconductor chip 10 is positioned with respect to the lens 22 and fixed to the package body 2. Further, by attaching the lid 3 to the package body 2, a distributed feedback semiconductor laser module 4 as shown in FIG.
5 is manufactured.

Such a semiconductor laser module (laser module) 45 is connected to a plurality of branch optical fibers 48 connected to a main optical fiber 46 in a wavelength division multiplexing optical transmission system as shown in FIG. Optically connected. A part of the branch optical fiber 48 serves as a modulator 49, which controls the modulation of the laser light emitted from each laser module 45. In the figure, 64 laser modules 45 are provided,
A laser beam having an oscillation wavelength of λ1 to λ64 is emitted, and the transmission light 50 by wavelength multiplexing is transmitted through the main optical fiber 46.

According to the first embodiment, the following effects can be obtained.

(1) A plurality of distributed feedback semiconductor laser sections 11 having different normalized coupling coefficients κL are monolithically formed on a semiconductor substrate 30 in parallel, and then a laser beam 16 emitted from each semiconductor laser section 11 is formed. The standardized coupling coefficient is determined from the spectrum of the semiconductor laser unit 11 to specify the semiconductor laser unit 11 that matches or most closely matches the design value, and then connects the upper electrode 12 and the electrode terminal 6 of the specified semiconductor laser unit 11 to the connection means. The semiconductor laser module 45 is manufactured by connecting the semiconductor laser module 45 with the semiconductor laser module 45. Therefore, a distributed feedback semiconductor laser module that oscillates in a single mode at a desired oscillation wavelength can be provided at a high yield and at low cost.

(2) Diffraction grating 3 of each semiconductor laser unit 11
7, the normalized coupling coefficient of each semiconductor laser unit 11 is gradually changed by the difference in the length of the diffraction grating 37. Therefore, each semiconductor laser section 11 emits laser light 16 having a different oscillation wavelength.

(Embodiment 2) FIGS. 11 to 14 are diagrams relating to a method of manufacturing a semiconductor chip 10 in a semiconductor laser module according to another embodiment (Embodiment 2) of the present invention.

In the second embodiment, a single semiconductor chip has a plurality of semiconductor laser sections, but these semiconductor laser sections have slightly different normalized coupling coefficients κL as in the first embodiment.

In the second embodiment, in order to change the normalized coupling coefficient κL, the length L of the diffraction grating region is the same in all the semiconductor laser portions (LD1 to LD4), but the depths of the diffraction gratings are different from each other. It has become.

In the second embodiment, an example in which four semiconductor laser sections 11 are formed in a single semiconductor chip 10 as in the first embodiment will be described.

As shown in FIG. 11, after preparing the same semiconductor substrate 30 as in the first embodiment, a CVD mask 6 made of, for example, an SiO ₂ film is formed on the upper surface of the semiconductor substrate 30.
0 is selectively formed, and four grooves 61 are formed in portions where the CVD mask 60 is not provided.

Next, as shown in FIG. 12, after a photoresist film 62 is provided on the entire surface of the semiconductor substrate 30,
A diffraction grating pattern of a resist is formed on the entire surface of the semiconductor substrate 30 by a common interference exposure method. The pitch of the diffraction grating is 240 nm.

Next, after developing the photoresist film 62, wet etching is performed using the photoresist film 62 as a mask to form a diffraction grating.

In the second embodiment, the etching area is W
Since the widths are different from 1, W2, W3, and W4, the depths of the diffraction gratings are different. In each groove, the depth of the diffraction grating decreases as the groove width increases.

FIG. 13 is a cross section of the semiconductor substrate 30 along the line aa in FIG. 12, and FIG. 14 is a cross section of the semiconductor substrate 30 along the line bb in FIG. Since the groove width of the line aa is the widest at W4, the depth of the diffraction grating 37 is the shallowest, and that of the line bb is the narrowest at W1 and the depth of the diffraction grating 37 is Be the deepest.

As a result, the normalized coupling coefficient κL of LD1 to LD4 can be changed mutually.

The semiconductor chip 1 manufactured as described above
0 is mounted in the package body 2 as in the first embodiment.

Also in the second embodiment, the wavelength controllability can be improved as in the case of the first embodiment.

(Embodiment 3) FIGS. 15 and 16 relate to a semiconductor laser module according to another embodiment (Embodiment 3) of the present invention.

FIG. 15 is a perspective view showing the laser module 45 with the lid removed. A submount 7 is fixed in the package body 2, and a semiconductor chip 10 having a laser array structure is fixed on the submount 7 by face-down bonding. An inner end of the electrode terminal 6 attached to the package body 2 protruding into the package body 2 and a wiring 70 formed on the submount 7
Is electrically connected to the wire pad 71 by the wire 27.

The end of the optical cable 5 (optical fiber) fixed to the package body 2 faces one end side (front emission surface side) of the semiconductor chip 10. Although not visible in the figure, a condensing lens 22 is arranged between the tip of the optical cable 5 and the emission surface of the semiconductor chip 10.

A light receiving element 26 is disposed on the other end side (rear emission surface side) of the semiconductor chip 10 to receive laser light emitted from the rear emission surface of the semiconductor chip 10 and to emit laser light. The strength is monitored.

FIG. 16 is a view showing the submount 7 and the semiconductor chip 10 mounted on the submount 7 by face-down bonding. The wiring 70 is provided on the surface of the submount 7. In the wiring 70, a connection electrode portion 72 corresponding to the upper electrode of each semiconductor laser portion is formed in a region where the semiconductor chip 10 is face-down bonded, and a wire pad 71 is arranged in a region outside the semiconductor chip 10. . It is to be noted that the semiconductor laser unit 11 and the upper electrode 12
Are omitted in FIG.

In the third embodiment, the upper electrode 12 of each semiconductor laser section 11 of the semiconductor chip 10 is connected to the connection electrode section 72 provided on the submount 7 via a bonding material (not shown). It will be easier.

(Embodiment 4) FIGS. 17 to 21 relate to a semiconductor laser module according to another embodiment (Embodiment 4) of the present invention.

In the fourth embodiment, a semiconductor laser type modulator for controlling each semiconductor laser section of a semiconductor chip is incorporated in the semiconductor laser module of the first embodiment. Therefore, the semiconductor laser module of the fourth embodiment does not require the modulator (optical fiber type modulator) provided in the optical fiber in the wavelength division multiplexing optical transmission system shown in the first embodiment.

FIG. 17 is a plan view of the laser module 45 with the lid removed. The semiconductor laser unit 11 and the modulator 75 for controlling the semiconductor laser unit 11 are provided in a single optical waveguide.

Therefore, as shown in FIG. 17, the electrode 27 of the specified semiconductor laser unit 11 and the upper electrode 76 of the modulator 75 for controlling the semiconductor laser unit 11 (see FIG. 18) also have the wire 27 connected to the electrode terminal 6. Connected through. The lower electrode of the modulator 75 is common to the lower electrode of the semiconductor laser unit 11.

FIG. 18 is a diagram showing the semiconductor chip 10 and the like mounted on the submount 7. As shown in the figure,
A modulator (electroabsorption modulator: EA (Electro Absorpution) modulator section) 75 and a semiconductor laser section 11 are arranged in series along the optical waveguide direction on the semiconductor chip 10, and a structure in which four of them are arranged is provided. ing. This number is not particularly limited.

FIG. 19 is an enlarged view of a portion C in FIG. 18, and FIG. 20 is an enlarged view of a portion D in FIG. Semiconductor laser unit 1
19 and the modulator 75 both have the same cross-sectional configuration as shown in FIG. 19, but as shown in FIG. 20, the semiconductor laser section 11 has a diffraction grating 37 and the EA modulator section 75 has no diffraction grating. It has a structure. Then, when a predetermined voltage is applied to the pair of electrodes of the EA modulator section 75, the emission of the laser light emitted from the semiconductor laser section 11 is stopped.

FIG. 21 shows a state in which a diffraction grating is formed on the upper surface of the semiconductor substrate 30 in the manufacture of the semiconductor chip 10. A region indicated by reference numeral 80 is a region where the diffraction grating 37 is provided (a region having a diffraction grating). ), An area indicated by reference numeral 81 is an area without a diffraction grating provided with the EA modulator section 75 (a modulator formation area without a diffraction grating), and an
The region indicated by is a region without a diffraction grating (region without a diffraction grating). The bold line frame portion is a portion forming a single semiconductor chip. Although not formed at this stage, the optical waveguide 41 is shown for easy understanding of the chip configuration.

Since the laser module 45 of the fourth embodiment has the modulator 75, laser light oscillation can be controlled.

(Embodiment 5) FIG. 22 is a diagram related to a semiconductor laser module according to another embodiment (Embodiment 5) of the present invention.

In the fifth embodiment, a semiconductor chip is mounted on an electronic cooling element, and the temperature of the semiconductor chip is controlled by driving the electronic cooling element to stabilize laser oscillation. That is, for example, the laser beam received by the light receiving element is monitored, and the amount of current for driving the electronic cooling element is controlled by the control circuit based on this information.

As shown in FIG. 22, an electronic cooling element (Peltier element) 90 is fixed to the package body 2, and the semiconductor chip 10 is fixed to the cooling surface side of the electronic cooling element 90. One electrode 91 of the electronic cooling element 90 is connected to the electrode terminal 6 via the wire 27. The lower electrode of the electron cooling element 90 is common to the lower electrode of the semiconductor laser unit 11.

In the laser module 45 of the fifth embodiment, since the temperature of the semiconductor chip 10 is controlled, high-precision laser oscillation becomes possible.

(Embodiment 6) FIG. 23 is a view relating to a semiconductor laser module according to another embodiment (Embodiment 6) of the present invention.

In the sixth embodiment, the electronic cooling element 90 is incorporated in the fourth embodiment, and the temperature of the semiconductor chip 10 is controlled to stabilize the laser oscillation.
That is, the semiconductor chip 10 having the semiconductor laser unit 11 and the modulator 75 is mounted on the electronic cooling element 90. In this structure, one electrode 9 of the electronic cooling element 90 is provided.
1 is connected to the electrode terminal 6 via a wire 27.
The lower electrode of the electron cooling element 90 is common to the lower electrode of the semiconductor laser unit 11.

In the laser module 45 of the sixth embodiment, the temperature of the semiconductor chip 10 is controlled, so that high-precision laser oscillation is possible.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a semiconductor chip according to an embodiment (Embodiment 1) of the present invention.

FIG. 2 is an enlarged plan view of a part of the semiconductor laser module of the first embodiment.

FIG. 3 is an enlarged perspective view showing a fixed state of the semiconductor chip in the semiconductor laser module of the first embodiment.

FIG. 4 is an enlarged view of a portion A in FIG. 3;

FIG. 5 is an enlarged view of a portion B in FIG. 3;

FIG. 6 is a diagram for manufacturing a semiconductor chip to be incorporated in the semiconductor laser module of the first embodiment, and is a schematic plan view in which a mask is selectively formed on a semiconductor substrate.

FIG. 7 is a diagram for manufacturing the semiconductor chip, and is a schematic plan view in which a resist diffraction grating pattern is formed on a semiconductor substrate.

FIG. 8 is a diagram for manufacturing the semiconductor chip, and is a schematic plan view in which a diffraction grating is selectively formed on the surface of a semiconductor substrate.

FIG. 9 is a graph showing a correlation between a normalized coupling coefficient κL and a single mode yield.

FIG. 10 is a schematic diagram showing a part of a wavelength division multiplexing optical transmission system incorporating the semiconductor laser module of the first embodiment.

FIG. 11 shows a CVD used for manufacturing a distributed feedback type semiconductor laser unit according to another embodiment (Embodiment 2) of the present invention.
It is a top view showing a mask.

FIG. 12 is a diagram illustrating a manufacturing state of the distributed feedback semiconductor laser unit according to the second embodiment, and is a schematic plan view in which a diffraction grating pattern of a resist is formed on a semiconductor substrate.

13 is a sectional view taken along the line aa in FIG.

FIG. 14 is a sectional view taken along the line bb in FIG. 12;

FIG. 15 is a schematic perspective view showing the internal structure of a semiconductor laser module according to another embodiment (Embodiment 3) of the present invention.

FIG. 16 is a perspective view showing a correlation between a semiconductor chip and a submount in the semiconductor laser module of Embodiment 3;

FIG. 17 is a schematic plan view showing the internal structure of a semiconductor laser module according to another embodiment (Embodiment 4) of the present invention.

FIG. 18 is a perspective view showing a correlation between a semiconductor chip and a submount in the semiconductor laser module according to the fourth embodiment.

FIG. 19 is an enlarged view of a portion C in FIG. 18;

FIG. 20 is an enlarged view of a portion D in FIG. 18;

FIG. 21 is a schematic plan view of a semiconductor substrate showing a manufacturing state of a distributed feedback semiconductor laser unit incorporated in the semiconductor laser module of Embodiment 4;

FIG. 22 is a schematic plan view showing the internal structure of a semiconductor laser module according to another embodiment (Embodiment 5) of the present invention.

FIG. 23 is a schematic plan view showing the internal structure of a semiconductor laser module according to another embodiment (Embodiment 6) of the present invention.

[Explanation of symbols]

1. Laser module (semiconductor laser module) 2.
.., Package body, 3 lid, 4 package, 5 optical cable, 6 electrode terminal, 7 submount, 10 semiconductor chip, 11 semiconductor laser section, 12 upper electrode,
13 ... lower electrode, 14 ... conductive layer, 15 ... cleavage, 16
... laser light, 20 ... guide pipe, 21 ... isolator, 22 ... lens, 25 ... submount, 26 ... light receiving element, 27 ... wire, 30 ... semiconductor substrate, 31 ... n-In
GaAsP waveguide layer, 32 ... InGaAsP / InGaAs
sP strained MQW active layer, 33 ... p-InGaAsP waveguide layer, 34 ... p-InP cladding layer, 35 ... p-InGa
As contact layer, 36 ... insulating film, 37 ... diffraction grating, 3
8 Mesa stripe, 40 Mask, 41 Waveguide (optical waveguide), 42 Photoresist film, 45 Laser module, 46 Main optical fiber, 47 Coupling section, 48
Branch optical fiber, 49 ... modulator, 50 ... transmission light, 60 ...
CVD mask, 61 groove, 62 photoresist film, 70
... wiring, 71 ... wire pad, 72 ... connection electrode part, 75
... modulator (EA modulator section), 76 ... upper electrode, 80 ... area with diffraction grating, 81 ... modulator formation area without diffraction grating, 82 ... area without diffraction grating, 90 ... electronic cooling element,
91 ... One electrode.

Claims (10)

[Claims] 1. A package with electrode terminals, and a plurality of distributed feedback semiconductor laser units arranged in the package and having mutually different normalized coupling coefficients κL which are products of the coupling coefficient κ and the length L of the diffraction grating region. A semiconductor chip formed monolithically in parallel, an optical fiber extending inside and outside the package, and each of the semiconductor laser portions interposed between an inner end of the optical fiber and an emission surface of the semiconductor chip. A lens for condensing the laser light emitted from the optical fiber into the optical fiber, and a connecting means for electrically connecting an electrode of one of the plurality of semiconductor laser units to the electrode terminal. A semiconductor laser module characterized by the above-mentioned. 2. A package with electrode terminals, and a plurality of distributed feedback semiconductor laser units arranged in the package and having different normalized coupling coefficients κL which are products of the coupling coefficient κ and the length L of the diffraction grating region. A semiconductor chip formed monolithically with a modulator controlling each of these semiconductor laser sections in parallel, an optical fiber extending over the inside and outside of the package, an inner end of the optical fiber, and an emission surface of the semiconductor chip. A lens interposed between the first and second semiconductor laser sections for condensing the laser light emitted from each of the semiconductor laser sections into the optical fiber; an electrode of one of the plurality of semiconductor laser sections and the electrode terminal; And a connecting means for electrically connecting the semiconductor laser module. 3. A package with electrode terminals, and a coupling coefficient κ disposed in the package via an electronic cooling element.
And the length L of the diffraction grating region, the normalized coupling coefficient κL
A monolithically formed semiconductor chip in which a plurality of distributed feedback semiconductor laser sections different from each other are formed, an optical fiber extending over the inside and outside of the package, an inner end of the optical fiber, and an emission surface of the semiconductor chip. A lens interposed between the first and second semiconductor laser sections for condensing laser light emitted from each of the semiconductor laser sections into the optical fiber; an electrode of one of the plurality of semiconductor laser sections; A semiconductor laser module comprising: connection means for electrically connecting an electrode of an element and the electrode terminal. 4. A package with electrode terminals, and a coupling coefficient κ disposed in the package via an electronic cooling element.
And the length L of the diffraction grating region, the normalized coupling coefficient κL
A plurality of distributed feedback semiconductor laser sections different from each other and a semiconductor chip monolithically formed with a modulator for controlling each of these semiconductor laser sections in a monolithic manner, an optical fiber extending over the inside and outside of the package, A lens that is interposed between an inner end of an optical fiber and an emission surface of the semiconductor chip and condenses laser light emitted from each of the semiconductor laser units into the optical fiber; A semiconductor laser module comprising: an electrode of one of the semiconductor laser units, an electrode of the modulator, and an electrode of the thermoelectric cooler, and connection means for electrically connecting the electrode terminal. 5. The standardized coupling coefficient of each of the plurality of semiconductor laser portions has a stepwise changed value, and the design standardized coupling coefficient is substantially in the middle of the stepwise changed standardized coupling coefficient. The semiconductor laser module according to claim 1, wherein: 6. The semiconductor laser module according to claim 1, wherein the lengths of the diffraction gratings of the respective semiconductor laser portions are different from each other. 7. The semiconductor laser module according to claim 1, wherein the depths of the diffraction gratings of the respective semiconductor laser portions are different from each other. 8. A step of mounting a semiconductor chip having a semiconductor laser part in a package with electrode terminals, a step of electrically connecting electrodes of the semiconductor laser part and the electrode terminals by connection means, A method for manufacturing a semiconductor laser module, comprising: a step of optically connecting an inner end of an optical fiber attached so as to extend over a semiconductor chip directly or via a lens to a semiconductor laser portion of the semiconductor chip. After preparing, a step of forming a semiconductor chip in which a plurality of semiconductor laser sections composed of distributed feedback semiconductor lasers having mutually different normalized coupling coefficients on the main surface of the semiconductor substrate are formed in parallel, and from each of the semiconductor laser sections A step of measuring the emitted laser beam and specifying a semiconductor laser portion that matches or is closest to the design value And mounting the semiconductor chip in a package with electrode terminals and then electrically connecting the electrodes of the specified semiconductor laser unit and the electrode terminals by connecting means, and directly connecting the inner end of the optical fiber or a lens. A method of optically connecting to a semiconductor laser portion of the semiconductor chip through a semiconductor laser module. 9. A step of mounting a semiconductor chip having a semiconductor laser part in a package with electrode terminals, a step of electrically connecting electrodes of the semiconductor laser part and the electrode terminals by connection means, A method for manufacturing a semiconductor laser module, comprising: a step of optically connecting an inner end of an optical fiber attached so as to extend over a semiconductor chip directly or via a lens to a semiconductor laser portion of the semiconductor chip. After preparing a semiconductor chip comprising a plurality of semiconductor laser sections comprising distributed feedback semiconductor lasers having mutually different normalized coupling coefficients on the main surface of the semiconductor substrate, and a plurality of modulators for controlling each of these semiconductor laser sections, Forming, and measuring the laser light emitted from each of the semiconductor laser portions to match the design value or most design value And a step of specifying a semiconductor laser unit which is similar to the above, and after mounting the semiconductor chip in a package with electrode terminals, electrically connecting the specified semiconductor laser unit and the electrodes of the modulator and the electrode terminals by connecting means. A method for manufacturing a semiconductor laser module, comprising: a step of connecting; and a step of optically connecting an inner end of the optical fiber to a semiconductor laser portion of the semiconductor chip directly or via a lens. 10. After the electronic cooling element is mounted in the package with the electrode terminals, the semiconductor chip is mounted on the electronic cooling element, and the electrodes of the electronic cooling element and the electrode terminals are connected at the time of connection by the connection means. The method for manufacturing a semiconductor laser module according to claim 8, wherein the connection is performed by the connection unit.