JP2002261389A - Optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical communication system in which a semiconductor laser can be controlled through a simple driving mechanism. SOLUTION: Since variation in the threshold current due to temperature variation is very small in a long wavelength band surface emission semiconductor laser on contrary to a prior art semiconductor laser, variation width of optical output including the temperature variation does not increase when the semiconductor laser is driven with a constant driving current and thereby a constant current supply can be controlled easily using simple circuitry. When upper and lower limits are set in the optical output and the current is controlled to a constant level x within the range of a current (a) determined by the upper limit optical output and an assumed lower limit temperature and a current (b) determined by the lower limit optical output and an assumed upper limit temperature, an output within the optical output range can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser used for optical communication and the like and an optical communication system therefor, and more particularly to a so-called surface which emits light in a direction perpendicular to the surface of a semiconductor substrate used for manufacturing the semiconductor laser. The present invention relates to an optical communication system in which a plurality of laser elements are formed using a light emitting laser to enable large-capacity communication.

[0002]

2. Description of the Related Art A surface emitting semiconductor laser emits laser light in a vertical direction from the surface of a substrate, so that two-dimensional parallel integration is possible, and the spread angle of the output light is relatively narrow (about 10 degrees). Therefore, it is easy to couple with an optical fiber and easy to inspect the element.
Therefore, in particular, development as an element suitable for configuring an optical transmission module (optical interconnection device) of a parallel transmission type has been actively conducted. The immediate application of the optical interconnection device is parallel connection between housings of computers and the like and between boards, as well as short-distance optical fiber communication, but large-scale computer networks and long distances are expected applications in the future. There is a trunk system for distance and large-capacity communication.

Generally, a surface emitting semiconductor laser is made of GaAs.
Or, it is common to comprise an active layer made of GaInAs, and an optical resonator consisting of an upper semiconductor distributed Bragg reflector disposed above and below the active layer and a lower semiconductor distributed Bragg reflector on the substrate side. However, since the length of the optical resonator is significantly shorter than that of the edge emitting semiconductor laser, it is necessary to set the reflectivity of the reflecting mirror to an extremely high value (99% or more) so as to easily cause laser oscillation. There is. For this reason, a semiconductor distributed Bragg reflector formed by alternately laminating a low-refractive-index material made of AlAs and a high-refractive-index material made of GaAs with a period of 1/4 wavelength is usually used.

By the way, as described above, a long wavelength band laser having a laser wavelength of 1.1 μm or more used for optical communication, for example, a long wavelength band having a laser wavelength of 1.3 μm or 1.55 μm. In the laser, InP is used for the production substrate and InGaAsP is used for the active layer. However, the lattice constant of InP of the substrate is large, and a large difference in the refractive index cannot be obtained with a reflecting mirror material that matches the substrate. Must be more than pairs.

Another problem with semiconductor lasers formed on InP substrates is that the characteristics change significantly with temperature. For this reason, it is necessary to add a device for keeping the temperature constant, and it is difficult to use the device for general purposes such as consumer use. Light emitting semiconductors have not yet been put to practical use.

As an invention made to solve such a problem, one disclosed in Japanese Patent Application Laid-Open No. 9-237942 is known. According to this, a GaAs substrate is used as a production substrate, and a semiconductor layer made of AlInP that can be lattice-matched with the substrate is used as a low refractive index layer of at least one of the semiconductor distributed Bragg reflectors in the lower part on the substrate side. A semiconductor layer made of GaInNAs is used as a high refractive index layer of at least one of the lower and upper semiconductor distributed Bragg reflecting mirrors so that a larger refractive index difference is obtained than in the prior art. It is to realize a mirror.

Further, GaInNAs is used as a material for the active layer. This is because the band gap (forbidden band width) is increased from 1.4 eV to 0 eV by increasing the N composition.
0.85 μm
This is because it can be used as a material that emits a longer wavelength. In addition, since lattice matching with the GaAs substrate is possible, the semiconductor layer made of GaInNAs is 1.3 μm.
Reference is also made to the fact that it is preferable as a material for long-wavelength surface emitting semiconductor lasers in the m-band and 1.55 μm band.

[0008]

However, in the past, this has merely suggested the possibility of realizing a surface emitting semiconductor laser in a wavelength band longer than 0.85 μm, and such a device is actually realized. I haven't. This is because the basic configuration is almost theoretically determined, but a more specific configuration for realizing stable laser emission is still unknown.

As an example, a semiconductor distributed Bragg reflector formed by alternately laminating a low-refractive-index material made of AlAs and a high-refractive-index material made of GaAs at a period of 1/4 wavelength as described above is used. In the case of using a semiconductor layer made of AlInP capable of lattice-matching with the same substrate as the low-refractive index layer of the semiconductor distributed Bragg reflector, as disclosed in Japanese Unexamined Patent Application Publication No. 9-237942, The laser element does not emit light at all,
Alternatively, even if light is emitted, the light emission efficiency is low, which is far from a practical level.

This is because the material containing Al is chemically very active, and crystal defects caused by Al are likely to occur. To solve this, Japanese Patent Application Laid-Open No. 8-34001
There is a proposal to form a semiconductor distributed Bragg reflector from GaInNP and GaAs that do not contain Al as in the inventions disclosed in Japanese Patent Application Publication No. 46-46 and Japanese Patent Application Laid-Open No. 7-307525.

However, the refractive index difference between GaInNP and GaAs is about half of the refractive index difference between AlAs and GaAs, so that the number of stacked reflectors becomes very large, making fabrication difficult. That is, at present, optical fiber communication is expected in computer networks and the like. However, there is no long-wavelength band surface emitting semiconductor laser with a usable laser wavelength of 1.1 μm to 1.7 μm and a communication system using the same. , Its emergence is longing.

The present invention relates to a long-wavelength surface emitting semiconductor laser having a laser oscillation wavelength of 1.1 μm to 1.7 μm used for such optical communication and the like, and an optical communication system therefor. Another object of the present invention is to propose an optical communication system that can control a semiconductor laser with a simple driving mechanism using a surface-emitting type semiconductor laser element chip capable of lowering an operating voltage, an oscillation threshold current and the like as a light emitting light source.

A second object is to use a long-wavelength surface emitting semiconductor laser device chip having a laser oscillation wavelength of 1.1 μm to 1.7 μm, which can be used stably, as a light emitting light source, and to use a semiconductor laser with a simple driving mechanism. To provide an optical communication system capable of controlling the optical communication.

It is a third object of the present invention to provide an optical communication system in which the influence of fluctuations in the threshold current of the semiconductor laser due to aging is reduced.

A fourth object of the present invention is to provide an optical communication system in which the influence of a change in the threshold current of a semiconductor laser due to aging is reduced by a simple mechanism in such an optical communication system.

A fifth object of the present invention is to provide an optical communication system in which the influence of a change in the threshold current of a semiconductor laser due to aging is reduced by a simple mechanism in such an optical communication system.

[0017]

According to the present invention, in order to achieve the above object, first, in a laser chip and an optical communication system connected to the laser chip, the laser chip has an oscillation wavelength of 1.1 μm to 1 μm. 0.7 μm, and the light-generating active layer is a layer whose main element is Ga, In, N, As or a layer consisting of Ga, In, As. What is claimed is: 1. A surface-emitting type semiconductor laser device chip having a resonator structure including a reflecting mirror provided at a lower portion, wherein the reflecting mirror periodically changes the refractive index of a material layer constituting the reflecting mirror to be small / large and is incident. A semiconductor distributed Bragg reflector for reflecting light by light wave interference, and the material layer having a small refractive index is made of Al _x Ga _{1 -x} As.
(0 <x ≦ 1) and then, the material layer of the refractive index is large is Al _y
A reflecting mirror having Ga _1-y As (0 ≦ y <x ≦ 1),
And a material layer Al _z Ga _{1 -z} As (0 ≦ y <z) in which the refractive index takes a value between small and large between the material layers with small and large refractive indexes.
An optical communication system using a surface-emitting type semiconductor laser device chip provided with <x ≦ 1) as an emission light source, wherein an upper limit and a lower limit of an optical output are set using a constant current power supply, and an upper limit and a lower limit of an assumed temperature. to control said semiconductor laser at a current value in the range of the current obtained from the optical output characteristic b - current a and a light output lower limit obtained from the optical output characteristic and temperature upper by a current - current by the light output upper and lower temperature limit by I made it.

Secondly, in a laser chip and an optical communication system connected to the laser chip, the laser chip has an oscillation wavelength of 1.1 μm to 1.7 μm, and the active layer for generating light includes a main element. Is Ga, In, N, As
Or a layer made of Ga, In, As, and a surface emitting semiconductor laser device chip having a resonator structure including reflectors provided above and below the active layer in order to obtain a laser beam. The reflector is a semiconductor distributed Bragg reflector in which the refractive index of the material constituting the reflector changes periodically as small / large and reflects incident light by light wave interference. Al _x Ga _1-x
As (0 <x ≦ 1), the material having a large refractive index is Al
a reflecting mirror with _y Ga _1-y As (0 ≦ y <x ≦ 1),
GaInP or Ga between the active layer and the reflector.
The non-radiative recombination preventing layer formed by providing a surface-emitting type semiconductor laser device chip consisting InPAs a optical communication system and light emission source, using a constant current power supply, to set the upper and lower light output, assume Current obtained from current-light output characteristics by upper and lower temperature limits
The semiconductor laser is controlled by a current value within a range of a current b obtained from a current-light output characteristic based on a, a light output lower limit, and a temperature upper limit.

Thirdly, in the first and second optical communication systems, a mechanism for monitoring the light amount is provided in the communication path, and means for converting the light amount to a current correction value is provided. From the amount of light obtained from
The semiconductor laser control is performed using the current value obtained by correcting the set current.

Fourthly, in the first and second optical communication systems, there is provided a mechanism for monitoring the light quantity of the light receiving element on the receiving side, and means for converting the light quantity into a current correction value. The light amount obtained from the light amount monitoring mechanism of the light receiving element is transmitted as data to the control mechanism on the transmission side, a correction value of the current is obtained from the light amount, and the semiconductor laser control is performed with the current value obtained by correcting the set current. did.

Fifth, in the third optical communication system, the end of the communication path is a receiving light receiving element, the light quantity monitoring mechanism is the light receiving element, and the light quantity of the light receiving element is data. The current is transmitted to a control mechanism on the transmission side, a correction value of the current is obtained from the light amount, and the semiconductor laser is controlled with the current value obtained by correcting the set current.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of a long-wavelength surface emitting semiconductor laser having a small laser oscillation wavelength of 1.1 to 1.7 .mu.m, which is a light emitting element applied to the optical communication system of the present invention, having a small transmission loss. This will be described with reference to FIG. As described above, a long-wavelength surface emitting semiconductor laser having a laser oscillation wavelength of 1.1 μm to 1.7 μm to which the present invention is conventionally applied only suggests the possibility. The material, as well as the more specific and detailed composition, were unknown. In the present invention, a material such as GaInNAs is used for the active layer, and a more specific configuration is clarified. The details are described below.

In the present invention, n-Ga having a plane orientation of (100) is used.
On the As substrate, n-Al _x Ga _{1 -x} A with a thickness (thickness of λ / 4) of 発 振 of the oscillation wavelength λ in each medium.
s (x = 1.0) (low refractive index layer to low refractive index layer) and n−
An n-semiconductor distributed Bragg reflector (AlAs / GaAs lower semiconductor distributed Bragg reflector) in which 35 cycles of Al _y Ga _1-y As (y = 0) (high refractive index layer to high refractive index layer) are alternately stacked. And n-Ga _x In _1-x P _{y having} a thickness of λ / 4 is formed thereon.
As _1-y (x = 0.5, y = 1) layers were laminated. In this example _{n-Ga x In 1-x} P y As 1-y (x = 0.5, y =
1) The layer is also a part of the lower reflecting mirror and is a low refractive index layer (a layer having a small refractive index).

An undoped lower GaAs spacer layer, an active layer (quantum well active layer), which is a three-layer Ga _x In _{1 -x} As quantum well layer, and a GaAs barrier layer (20 n
m) and an undoped upper G layer
The aAs spacer layer is laminated to form a resonator having a thickness of one oscillation wavelength λ (thickness of λ) in the medium.

Further, on top of this, C (carbon) -doped p-
Ga _x In _{1-x Py} As _1-y (x = 0.5, y = 1) layer and Z
A periodic structure (one cycle) in which n-doped p-Al _x Ga _1-x As (x = 0) is alternately stacked with a thickness of １ ／ times the oscillation wavelength λ in each medium is stacked. C-doped p-Al _x Ga _{1 -x} As (x = 0.9) and Zn-doped p
A semiconductor distributed Bragg reflector (a periodic structure (25 periods) in which -Al _x Ga _{1 -x} As (x = 0) is alternately stacked with a thickness of １ ／ times the oscillation wavelength λ in each medium; Al _0.9 Ga _0.1 As / GaAs upper semiconductor distributed Bragg reflector)
Is formed. In this example _{p-Ga x In 1-x} P y As
_{The 1-y} (x = 0.5, y = 1) layer is also a part of the upper reflecting mirror and is a low refractive index layer (a layer having a small refractive index).

Here, both the upper and lower reflectors are formed by alternately laminating a low refractive index layer (a layer having a low refractive index) / a high refractive index layer (a layer having a high refractive index). Between these, the material layer Al _z G whose refractive index takes a value between small and large
a _1-z As (0 ≦ y <z <x ≦ 1) is provided. FIG.
Is a material layer Al _z Ga _{1 -z} As having a refractive index between small and large between a low refractive index layer (a layer with a small refractive index) and a high refractive index layer (a layer with a large refractive index). 1 shows a part of a semiconductor distributed Bragg reflector provided with (0 ≦ y <z <x ≦ 1) (FIG. 1)
Then, the illustration is omitted because the figure becomes complicated).

Conventionally, it has been studied to provide such a material layer for a semiconductor laser having a laser wavelength of 0.85 μm band, but it is still in the stage of study, and the material and its thickness are not described in detail. Not considered. Further, the laser oscillation wavelength as in the present invention is 1.1 μm to 1.7 μm.
No consideration has been given to a long-wavelength surface emitting semiconductor laser having a wavelength of m. The reason for this is that this field (a long-wavelength surface emitting semiconductor laser having a laser oscillation wavelength of 1.1 μm to 1.7 μm) is a new field, and little research has yet been made. The present inventor has quickly noticed the usefulness of this field (a long-wavelength surface emitting semiconductor laser having a laser oscillation wavelength of 1.1 μm to 1.7 μm and optical communication using the same), and intensively studied for realizing it. went.

In such a material layer, the refractive index of the material layer is changed continuously or stepwise by controlling the gas flow rate at the time of formation, so that the Al composition is changed continuously or stepwise. And formed. More specifically, Al _z Ga _{1 -z} As (0 ≦ y <z <x ≦ 1)
The value of z of the layer is changed from 0 to 1.0, that is, G
aAs to AlGaAs to AlAs, and Al and G
It is formed such that the ratio of a is gradually changed. This is created by controlling the gas flow during layer formation as described above. Further, it may be formed so that the ratio of Al and Ga changes continuously as described above, or the same effect can be obtained even if the ratio changes stepwise.

The reason for providing such a material layer is to solve the problem that the electrical resistance of the p-semiconductor distributed Bragg reflector, which is one of the problems of the distributed Bragg reflector, is high. This is due to the hetero barrier generated at the interface between the two types of semiconductor layers constituting the semiconductor distributed Bragg reflector. However, as in the present invention, the interface between the low refractive index layer and the high refractive index layer is changed from one composition to the other. It is possible to suppress the generation of the hetero barrier by changing the Al composition gradually to the composition and changing the refractive index.

Further lasing wavelength, such as such a refractive index takes a value between the small and large material layer _{Al z Ga 1-z As (} 0 ≦ y <z <x ≦ 1) the invention is 1 .1 μm to 1.7 μ
5 nm to 50 nm in the case of a long-wavelength surface emitting semiconductor laser
It is preferable that the thickness is less than 10 nm. If the thickness is smaller than this, there is a problem that the resistance becomes large and the current hardly flows, and the element generates heat and the driving energy becomes high. In addition, when the thickness is large, the resistance becomes small, which is advantageous in terms of heat generation of the element and driving energy, but there is a problem that the reflectance cannot be obtained this time,
As described above, it is necessary to select an optimum range (thickness of 5 nm to 50 nm).

As described above, it has been considered to provide such a material layer for a conventional semiconductor laser having a laser wavelength in the 0.85 μm band. In the case of a long-wavelength surface emitting semiconductor laser having a wavelength of 1.7 μm, it is more effective. This is because, for example, in order to obtain the same reflectance (for example, 99.5% or more), the band from 1.1 μm to 1.0 μm is more than 0.85 μm.
In the case of the 7 μm band, such a material layer can be approximately doubled, so that the resistance value of the semiconductor distributed Bragg reflector can be reduced, the operating voltage, the oscillation threshold current, and the like are reduced, and the laser device This is advantageous in terms of preventing heat generation, stable oscillation, and low energy driving.

That is, providing such a material layer on a semiconductor distributed Bragg reflector is particularly effective in the case of a long-wavelength surface emitting semiconductor laser having a laser oscillation wavelength of 1.1 μm to 1.7 μm as in the present invention. it can be said that Do not twist.

As an example of a more detailed examination result for obtaining an effective reflectance, for example, in a 1.3 μm band surface emitting laser device, Al _x Ga _{1 -x} As (x = 1.0)
(Low refractive index layer to low refractive index layer) and Al _y Ga _1-y As (y
= 0) (in the case of a high refractive index layer-refractive index large layer) 20 period stacking, the reflectance of the semiconductor distributed Bragg reflector is 99.7% or less _{Al z Ga 1-z As (} 0 ≦ y <z
<X ≦ 1) The thickness of the layer is 30 nm. The wavelength band in which the reflectance is 99.5% or more is 53 nm. When the reflectance is designed to be 99.5% or more, it is only necessary to control the film thickness by ± 2%. Therefore, when prototypes of 10 nm, 20 nm, and 30 nm which are equivalent to and thinner than this were prototyped, the reflectivity could be kept to a practically acceptable level, and the resistance value of the semiconductor distributed Bragg reflector could be reduced. A 1.3 μm band surface emitting laser device was realized, and laser oscillation was successful. Other configurations of the prototyped laser element are as described below.

In the multilayer reflector, there is a band having a high reflectance including the design wavelength (assuming that the film thickness can be completely controlled). It is referred to as a high-reflectance band (including a region where the reflectivity is equal to or more than a required value for a target wavelength). This is the region where the reflectance at the design wavelength is the highest and decreases very little as the wavelength increases. It drops off sharply from some area. Originally, it is necessary to completely control the film thickness of the multilayer mirror at the atomic layer level so that the reflectance is higher than the required reflectance for the target wavelength.

However, a film thickness error of about ± 1% actually occurs, so that the target wavelength deviates from the wavelength having the highest reflectance. For example, when the target wavelength is 1.3 μm, when the film thickness control is shifted by 1%, the wavelength having the highest reflectance is shifted by 13 nm. Therefore, it is desirable that the band of the high reflectance (here, the region where the reflectance is equal to or more than a required value with respect to a target wavelength) is wide. However, thickening the intermediate layer tends to narrow this band.

As described above, in the long-wavelength surface emitting semiconductor laser having a laser oscillation wavelength of 1.1 μm to 1.7 μm as in the present invention, the configuration of such a semiconductor distributed Bragg reflector is devised and optimized. Since the resistance value can be reduced while maintaining a high reflectance, the operating voltage, the oscillation threshold current, and the like can be reduced, so that heat generation of the laser element, stable oscillation, and low-energy driving can be achieved.

Referring again to FIG. 1, the uppermost p-Al _x G
The a _1-x As (x = 0) layer also has a role as a contact layer (p-contact layer) for making contact with the electrode. Here, the In composition x of the quantum well active layer is 3
9% (Ga0.61In0.39As). The thickness of the quantum well active layer was 7 nm. The quantum well active layer is made of GaAs.
It had a compression strain of about 2.8% with respect to the substrate.

The entire surface emitting semiconductor laser was grown by MOCVD. In this case, no lattice relaxation was observed. The materials constituting each layer of the semiconductor laser include TMA (trimethylaluminum), TMG (trimethylgallium), TMI (trimethylindium),
AsH ₃ (arsine) and PH ₃ (phosphine) were used. H ₂ was used as a carrier gas. In the case where the strain is large as in the active layer (quantum well active layer) of the device shown in FIG. here,
The GaInAs layer (quantum well active layer) is grown at 550 ° C.

The MOCVD method used here has a high degree of supersaturation and is suitable for crystal growth of a high strain active layer. In addition, high vacuum is not required as in the MBE method, and the supply flow rate and supply time of the source gas may be controlled.

In this example, a portion outside the current path was irradiated with protons (H ⁺ ) to form an insulating layer (high-resistance portion) to form a current narrowing portion. In this example, a p-side electrode is formed on the p-contact layer which is the uppermost layer of the upper reflector and is a part of the upper reflector, excluding the light emitting portion, and an n-side electrode is formed on the back surface of the substrate. Was formed. In this example, the active region (in this embodiment, a resonator composed of the upper and lower spacer layers and the multiple quantum well active layer) sandwiched between the upper and lower reflectors and into which carriers are injected and recombined, has an active region. material containing al (percentage of group III 1% or more) without using a further layer closest to the active layer of the low refractive index layer of the lower and upper reflector _{Ga x in 1-x P y} As 1 _-y (0
<X <1, 0 <y ≦ 1).

Since the carriers are confined between the low-refractive index layers of the upper and lower reflectors, which are the wide gap closest to the active layer, only the active region contains an Al-free layer (II).
Even if it is composed of 1% or less in the group I), the low refractive index layer (wide gap layer) of the reflecting mirror in contact with the active region is made of Al.
The that of the is structure containing, when the carrier is recombined are injected, luminous efficiency occurs non-radiative recombination at the interface is lowered. Therefore, it is desirable that the active region be formed of a layer containing no Al.

The Ga _x In _{1-x Py} As _1-y (0 <x
The non-radiative recombination preventing layer composed of <1, 0 <y ≦ 1)
Its lattice constant is smaller than that of a GaAs substrate and has tensile strain. In the epitaxial growth, the growth is performed by reflecting the information of the base, and if there is a defect on the surface of the substrate, it goes up to the growth layer. However, it is known that the presence of a strained layer is effective in preventing such defects from climbing.

When the defect reaches the active layer, the luminous efficiency is reduced. In the case of an active layer having a strain, there arises a problem that the critical thickness is reduced and a layer having a required thickness cannot be grown. In particular, when the amount of compressive strain of the active layer is large, for example, 2% or more, or when the thickness of the strained layer is larger than the critical thickness, even if non-equilibrium growth such as low-temperature growth is performed, growth cannot be performed due to the presence of defects. This is particularly problematic. If a strained layer is present, such a defect can be prevented from climbing up, so that the luminous efficiency can be improved, a layer having a compressive strain of 2% or more of the active layer can be grown, or the thickness of the strained layer can be reduced to a critical film. It becomes possible to grow thicker than thick.

This Ga _x In _{1-x Py} As _1-y (0 <x <
1,0 <y ≦ 1) layer also has the role of carrier confinement in which the active region in contact with the active region but, Ga _x an In
_{The 1-x Py} As _1-y (0 <x <1, 0 <y ≦ 1) layer can have a larger band gap energy as the lattice constant decreases. For example, in the case of Ga _x In _1-x P (when y = 1), as x increases and approaches x GaP, the lattice constant increases and the band gap increases.

The band gap Eg is determined by the direct transition.
(Γ) = 1.351 + 0.643x + 0.786x^Two, Eg with indirect transition
(X) = 2.24 + 0.02x. Therefore active territory
Area and Ga _xIn_1-xP_yAs_1-y(0 <x <1, 0 <y ≦
1) Carrier confinement because the hetero barrier of the layer becomes large
Becomes better and the threshold current reduction, temperature characteristic improvement, etc.
effective.

Further, the Ga _x In _{1-x Py} As _1-y (0 <
x <1, 0 <y ≦ 1) The non-radiative recombination preventing layer has a larger lattice constant than the GaAs substrate, has a compressive strain, and has a lattice constant of the active layer of Ga _x.
It has a larger compressive strain than the In _{1-x Py} As _1-y (0 <x <1, 0 <y ≦ 1) layer.

The Ga _x In _{1-x Py} As _1-y (0 <x
<1, 0 <y ≦ 1) Since the direction of strain of the layer is the same as that of the active layer, it acts in the direction of reducing the substantial amount of compressive strain felt by the active layer. The larger the strain is, the more easily affected by external factors. Therefore, it is particularly effective when the amount of compressive strain of the active layer is as large as 2% or more, or when it exceeds the critical film thickness.

[0048] For example surface emitting laser with an oscillation wavelength of 1.3μm band is preferably formed on a GaAs substrate, the often used semiconductor multilayer reflector cavity, a total thickness of at 5~8μm It is necessary to grow 50 to 80 semiconductor layers before growing the active layer. (On the other hand, in the case of the edge emitting laser, the total thickness before growing the active layer is about 2 μm, and it is only necessary to grow about three semiconductor layers.)

In this case, even if a high-quality GaAs substrate is used, the surface of the GaAs substrate may have various causes (defects once generated basically crawl in the crystal growth direction and defects are generated at the hetero interface). The defect density on the surface immediately before the growth of the active layer is inevitably higher than the defect density of the active layer.
If the insertion of a strained layer or the substantial amount of compressive strain felt by the active layer is reduced before the growth of the active layer, the influence of defects on the surface immediately before the growth of the active layer can be reduced.

In this example, since Al is not contained in the active region and at the interface between the reflector and the active region, non-radiative recombination caused by crystal defects caused by Al during carrier injection is eliminated. And non-radiative recombination was reduced.

As described above, it is preferable to apply a structure in which Al is not contained at the interface between the reflector and the active region, that is, to provide a non-radiative recombination preventing layer for both the upper and lower reflectors. It is effective even when applied to a reflector. In this example, both the upper and lower reflecting mirrors are semiconductor distributed Bragg reflecting mirrors, but one reflecting mirror may be a semiconductor distributed Bragg reflecting mirror and the other reflecting mirror may be a dielectric reflecting mirror. In the above-described example, only the layer closest to the active layer in the low-refractive index layer of the reflector is Ga _x In _{1-x Py} As _1-y (0 <x <1,
Although a non-radiative recombination prevention layer of 0 <y ≦ 1) is used, a plurality of layers of Ga _x In _{1-x Py} As _1-y (0 <x <1, 0 <y ≦
1) may be a non-radiative recombination preventing layer.

Further, in this example, this idea is applied to the lower reflector between the GaAs substrate and the active layer, and a crystal defect caused by Al, which is a problem during the growth of the active layer, rises into the active layer. The adverse effect is suppressed, and the active layer can be crystal-grown with high quality. As a result, a surface-emitting type semiconductor laser having high luminous efficiency and sufficient reliability for practical use was obtained. In addition, not all of the low refractive index layers of the semiconductor distributed Bragg reflector but at least a portion closest to the active region is Ga _x In _{1 -x Py} As _{1 -y} (0 <x <
Since only 1, 0 <y ≦ 1) layers, the above-described effect can be obtained without particularly increasing the number of stacked reflectors.

The oscillation wavelength of the surface emitting semiconductor laser manufactured as described above was about 1.2 μm. GaInAs on a GaAs substrate has a longer wavelength due to an increase in the In composition, but with an increase in the amount of strain. Conventionally, up to 1.1 μm has been considered to be the limit of a longer wavelength (see the document “IEEE Photo”).
onics. Technol. Lett. Vol. 9
(1997) p. 1319-1321 ").

However, as produced by the present inventors, a high strain GaInAs quantum well active layer can be coherently grown thicker than before by a method of high non-equilibrium growth such as low temperature growth at 600 ° C. or lower. Reached 1.2 μm. This wavelength is transparent to the Si semiconductor substrate. Therefore, light transmission through the Si substrate becomes possible in a circuit chip in which an electronic element and an optical element are integrated on the Si substrate.

As is clear from the above description, it was found that a surface emitting semiconductor laser in a long wavelength band can be formed on a GaAs substrate by using GaInAs having a large In composition and a high compression strain as the active layer. As described above, such a surface emitting semiconductor laser can be grown by MOCVD, but other growth methods such as MBE can also be used. Although the triple quantum well structure (TQW) has been described as an example of the stacked structure of the active layer, a structure (SQW, MQW) using a quantum well of another number of wells may be used.

The structure of the laser may be another structure. Although the length of the resonator is set to the thickness of λ, it can be set to an integral multiple of λ / 2. Desirably, it is an integral multiple of λ. Also, an example in which GaAs is used as the semiconductor substrate has been described.
The above concept can be applied even when another semiconductor substrate such as P is used. The period of the reflecting mirror may be another period.

In this example, as the active layer, a layer whose main element is Ga, In, or As, that is, Ga _x In _{1 -x}
Although an example of As (GaInAs active layer) has been described, in order to perform laser oscillation of a longer wavelength, a layer (GaInNAs active layer) in which N is added and the main element is Ga, In, N, and As is used. Good.

[0058] Indeed, by changing the composition of the GaInNAs active layer, 1.3 .mu.m band, in each of 1.55μm band, it was possible to perform laser oscillation. By studying the composition, a longer wavelength, for example, 1.7
A surface emitting laser in the μm band is also possible.

[0059] Also, by using the GaAsSb in the active layer G
A 1.3 μm band surface emitting laser can be realized on an aAs substrate. As described above, a semiconductor laser having a wavelength of 1.1 μm to 1.7 μm has not conventionally been available with a suitable material.
By using aInAs, GaInNAs, and GaAsSb, and providing a non-radiative recombination preventing layer, a high-performance surface emitting laser in a long wavelength region of the 1.1 μm to 1.7 μm band where stable oscillation has been difficult in the past. Can be realized.

Next, another configuration of a long wavelength band surface emitting semiconductor laser which is a light emitting element applied to the optical transmitting / receiving system of the present invention will be described with reference to FIG. Also in this case, FIG.
As in the case of (1), an n-GaAs substrate having a plane orientation of (100) is used. N-Al _x Ga _{1 -x} A in a thickness of １ ／ of the oscillation wavelength λ (thickness of λ / 4) in each medium.
An n-semiconductor distributed Bragg reflector (Al _0.9 Ga _0.1 As / GaAs lower reflector) in which s (x = 0.9) and n-Al _x Ga _1-x As (x = 0) are alternately stacked for 35 periods. _{formed, n-Ga x in 1-} x P thickness on the lambda / 4 Part _{y As 1-y (x =} 0.
5, y = 1) layers were laminated. In this example, n-Ga _x In
_{The 1-x Py} As _1-y (x = 0.5, y = 1) layer is also a part of the lower reflector and is a low refractive index layer.

On top of that, undoped lower GaAs
A multi-quantum well active layer (a quantum well active layer) composed of a spacer layer, an active layer (quantum well active layer) which is a three-layer Ga _x In _1-x N _y As _1-y quantum well layer, and a GaAs barrier layer (15 nm). In the example, triple quantum well (TQW)) and undoped upper Ga
An As spacer layer is laminated to form a resonator having a thickness (λ thickness) of one oscillation wavelength in the medium.

Further, a p-semiconductor distributed Bragg
A reflecting mirror (upper reflecting mirror) is formed. Top reflector
Is a method in which an AlAs layer to be a selectively oxidized layer is formed as a GaInP layer.
Low refractive index layer having a thickness of 3λ / 4 sandwiched between AlGaAs layers
(C-doped p-Ga having a thickness of (λ / 4-15 nm)_xI
n_1-xP_yAs_1-y(X = 0.5, y = 1) layer, C-doped
p-Al _zGa_1-zAs (z = 1) selective oxidation layer (thickness 3
0 nm) and a C-doped p having a thickness of (2λ / 4-15 nm)
-Al_xGa_1-xAs layer (x = 0.9)) and the thickness is λ /
4 GaAs layer (one period) and C-doped p-Al_xG
a_1-xAs layer (x = 0.9) and p-Al_xGa_1-xAs
The (x = 0) layer has an oscillation wavelength of 1 in each medium.
With a periodic structure (22 periods) alternately stacked with a thickness of / 4 times
Consisting of a semiconductor distributed Bragg reflector (Al_0.9G
a_0.1As / GaAs upper reflector).

[0063] Note that also in this embodiment, it is omitted for illustration since complicated in Figure 3, the structure of a semiconductor distributed Bragg reflector, the low refractive index layer as shown in FIG. 2 (refractive index Small Layer) and a high refractive index layer (high refractive index layer), a material layer Al _z Ga _1-z having a refractive index between low and high
As (0 ≦ y <z <x ≦ 1) is provided.

Then, the uppermost p-Al _x Ga _{1 -x} As
The (x = 0) layer also serves as a contact layer (p-contact layer) for making contact with the electrode. Here, the In composition x of the quantum well active layer is 37%,
(Nitrogen) composition was 0.5%. The thickness of the quantum well active layer was 7 nm.

The surface emitting semiconductor laser was grown by MOCVD. The materials constituting each layer of the semiconductor laser include TMA (trimethylaluminum), TM
G (trimethyl gallium), TMI (trimethyl indium), AsH ₃ (arsine), PH ₃ (phosphine), and DMHy (dimethylhydrazine) were used as raw materials for nitrogen. DMHy decomposes at low temperature, so 600
It is suitable for low-temperature growth at a temperature of less than or equal to ° C., and is particularly preferable when growing a quantum well layer having a large strain that requires low-temperature growth. Note that H ₂ was used as a carrier gas.

In this example, the GaInNAs layer (quantum well active layer) was grown at 540 ° C. The MOCVD method has a high degree of supersaturation and is suitable for crystal growth of a material containing N and another V group simultaneously. In addition, high vacuum is not required as in the MBE method, and the supply flow rate and supply time of the source gas may be controlled.

[0067] Further in this example, the predetermined size mesa portion of the _{p-Ga x In 1-x} P y As 1-y (x = 0.5, y =
Until reaching 1) _{layer, p-Al z Ga 1-} z As (z = 1)
The selective oxidation layer is formed by exposing the side surface, and the Al _x Ga _{1 -z} As (z = 1) layer on the side surface is oxidized from the side surface with water vapor to form an Al _x O _y current narrowing layer. .

Finally, a portion removed by mesa etching with a polyimide (insulating film) is buried and flattened, the polyimide on the upper reflector is removed, and a p-side electrode is formed on the p-contact layer except for the light emitting portion. And n on the back surface of the GaAs substrate.
Side electrodes were formed.

In this example, the lower part of the selectively oxidized layer
Ga as part of the top reflector_xIn_{1 -x}P_yAs_1-y(0 <
x <1, 0 <y ≦ 1) layers are inserted. For example
In the case of etching, a sulfuric acid-based etchant is used.
For example, the GaInPAs system is an etch to the AlGaAs system.
Ga can be used as a stopping layer._xIn
_1-xP_yAs_1-y(0 <x <1, 0 <y ≦ 1) layer inserted
The high mesa etching for selective oxidation.
Can be strictly controlled. Therefore, uniformity and reproducibility are improved.
Cost can be reduced.

When the surface-emitting type semiconductor laser (element) of this example is integrated one-dimensionally or two-dimensionally, the controllability at the time of manufacturing the element is improved, and the uniformity of the element characteristics of each element in the array is improved. In addition, there is an effect that reproducibility becomes extremely good.

In this example, Ga _x In _{1-x Py} As _1-y (0 <x <1, 0 <y ≦
1) Although the layer is provided on the upper reflecting mirror side, it may be provided on the lower reflecting mirror side. Also in this example, in the active region (in this embodiment, a resonator composed of the upper and lower spacer layers and the multiple quantum well active layer) sandwiched between the upper and lower reflectors and into which carriers are injected and recombined, the active region No material containing Al is used, and the lower refractive index layers of the lower and upper mirrors, which are closest to the active layer, are formed of Ga _x In _{1-x Py} As _1-y (0 <
(x <1, 0 <y ≦ 1). That is, in this example, Al is not included in the active region and at the interface between the reflecting mirror and the active region, so that non-radiative recombination caused by crystal defects caused by Al during carrier injection is reduced. Can be done.

[0072] Note that the structure at the interface between the reflector and the active region does not contain Al, it is preferably applied to the upper and lower reflector as in this example, it is effective just to apply either one of the reflecting mirrors . In this example, both the upper and lower reflecting mirrors are semiconductor distributed Bragg reflecting mirrors, but one reflecting mirror may be a semiconductor distributed Bragg reflecting mirror and the other reflecting mirror may be a dielectric reflecting mirror.

[0073] Also further in this embodiment, since the application of the same concept as in the example of FIG. 1 the bottom reflector between the GaAs substrate and the active layer, crystal defects due to Al which is a problem during the growth of the active layer Of the active layer is suppressed, and crystal growth of the active layer with high quality can be achieved.

Incidentally, such a non-radiative recombination preventing layer is
1 and 3, a part of the semiconductor distributed Bragg reflector is formed, and its thickness is 、 of the oscillation wavelength λ in the medium (thickness of λ / 4). ). Alternatively, a plurality of layers may be provided.

As is clear from the above description, a surface-emitting type semiconductor laser having high luminous efficiency and sufficient reliability for practical use was obtained with such a configuration. Also, not all of the low refractive index layers of the semiconductor distributed Bragg reflector, but at least the portion closest to the active region is Ga _x In containing no Al.
_{1-x Py} As _1-y (0 <x <1, 0 <y ≦ 1) is used only as a non-radiative recombination prevention layer, so that the above-described effect can be obtained without particularly increasing the number of stacked reflectors. I was able to.

In addition, even in such a configuration, since the polyimide can be easily embedded, the wiring (p-side electrode in this example) is hardly disconnected, and a device having high reliability can be obtained. The oscillation wavelength of the surface emitting semiconductor laser manufactured in this manner was about 1.3 μm.

In this example, the main elements are Ga, In,
A layer composed of N and As was used as an active layer (GaInNAs
As a result, a long-wavelength surface emitting semiconductor laser could be formed on the GaAs substrate. Further, the current was narrowed by selective oxidation of the selectively oxidized layer containing Al and As as main components, so that the threshold current was low.

According to the current narrowing structure using the current narrowing layer made of the Al oxide film in which the selectively oxidized layer is selectively oxidized,
By forming the current narrowing layer close to the active layer, the spread of current can be suppressed, and carriers can be efficiently confined in a minute region that is not exposed to the atmosphere.

Further, by oxidizing to form an Al oxide film, the refractive index is reduced, and light can be efficiently confined in a minute region in which carriers are confined by the effect of a convex lens. Can be reduced. In addition, since the current narrowing structure can be easily formed, the manufacturing cost can be reduced.

As is clear from the above description, a 1.3 μm band surface emitting semiconductor laser can be realized in the configuration as shown in FIG. Is obtained. The surface emitting semiconductor laser of FIG. 3 can be grown by MOCVD as in the case of FIG. 1, but other growth methods such as MBE can be used. Although DMHy is used as a nitrogen source, activated nitrogen and other nitrogen compounds such as NH ₃ can be used.

Further, although an example of a triple quantum well structure (TQW) is shown as the laminated structure of the active layer, a structure using other quantum wells (SQW, DQW, MQW) or the like may be used. The structure of the laser may be another structure.

In the surface-emitting type semiconductor laser shown in FIG. 3, by changing the composition of the GaInNAs active layer, 1.
A surface emitting semiconductor laser in the 55 μm band, and even in the longer wavelength 1.7 μm band, is also possible. The GaInNAs active layer may contain other III-V elements such as Tl, Sb, and P. Also, even if GaAsSb is used for the active layer, a 1.3 μm band surface emitting semiconductor laser can be realized on a GaAs substrate.

When GaInAs is used for the active layer,
Conventionally, up to 1.1 μm has been considered to be the limit of increasing the wavelength.
The quantum well active layer can be grown thicker than before, and the wavelength can reach up to 1.2 μm.

As described above, the wavelength of 1.1 μm to 1.7 μm
Although the semiconductor laser of the prior art did not have a suitable material, the active layer has a high strain of GaInAs, GaInNAs, and GaAsSb.
By using a non-radiative recombination prevention layer,
Wavelength of 1.1 μm to 1.7 μ for which stable oscillation has conventionally been difficult
In the long wavelength region of the m-band, a high-performance surface emitting laser can be realized, and application to an optical communication system has become possible.

FIG. 4 shows an example in which such a long wavelength band surface emitting semiconductor laser device is formed as a large number of chips on an n-GaAs wafer having a plane orientation of (100), and a laser device chip. In the laser element chip shown here, 1 to n laser elements are formed, and the number n and the arrangement method are determined according to the application.

However, since the threshold current of a conventional semiconductor laser changes due to a change in temperature, it is difficult to control the semiconductor laser with a constant current in a communication system. A light-receiving element (photodiode) is provided on the opposite side
It was necessary to feed back the light amount and control the light amount to be constant. Since a surface emitting laser cannot have a light receiving element on the opposite side, a complicated mechanism is required, such as providing a mechanism to receive light until it reaches the fiber or after the fiber and controlling it in real time so that the amount of light is constant. turn into.

FIG. 5 shows an example of the IL (current-light output) characteristic of the long wavelength band surface emitting semiconductor laser according to the present invention. Unlike a conventional semiconductor laser, the threshold current fluctuates very little due to a temperature change, and the slope of IL is affected by the temperature change. Therefore, when the semiconductor laser is driven with a constant drive current, the fluctuation width of the optical output including the temperature change does not become large.

In FIG. 5, if the semiconductor laser is driven with the current set to 6 mA, the temperature range is from 10 ° to 70 °.
The fluctuation range of the optical output is 0.1mW, and the temperature range is 10 ° to 100 °.
In °, the fluctuation range of the optical output is 0.25 mW. S / N (signal-to-noise ratio) is 26d due to light intensity fluctuation of each signal level
B, which is 18 dB, and sufficient signal quality can be obtained in communication in a general environment of 20 ° to 70 °.

In general, a constant current power supply has a current variation within ± 2 to 3% even if a circuit having a simple structure is used, so that constant current control can be easily performed. As shown in FIG. 6, the upper limit and the lower limit of the light output are set, and the current a obtained by the light output upper limit and the temperature lower limit by the assumed temperature upper limit and the lower limit is within the range of the current b obtained by the light output lower limit and the temperature upper limit. By controlling the current at a constant value x, an output in the light output range of FIG. 6 can be obtained. As described above, if the semiconductor laser of the present invention is driven with a constant current while setting a current with respect to a target optical output, a practical communication system can be constructed.

The threshold current of a semiconductor laser gradually increases with aging and reaches its life. Therefore, means for preventing signal quality from deteriorating due to aging is desired. As shown in FIG. 7, the amount of light is monitored in the middle of the communication path, the value is fed back to the light emission control unit, data for obtaining a correction current from the amount of light monitored by the light receiving element is prepared in advance, and the set current value is periodically changed. Or by correcting at any time, it is possible to eliminate fluctuations in light output due to aging,
It is possible to construct a practical communication system.

In order to monitor the secular change or abnormality of the semiconductor laser, it is sufficient to know the state of the light receiving element on the receiving side, and this can be transmitted by sending it to the transmitting side as data. The data of the light receiving element is sent periodically or as needed separately from the communication data, and the communication control unit sends the monitor light amount data to the light emission control unit, feeds back the value to the LD control unit, and obtains the correction current from the monitor light amount. By preparing data to be used in advance and correcting the set current value, fluctuations in optical output due to aging can be eliminated, and a practical communication system can be constructed.

[0092]

[Effect of the Invention] [Claim 1 to the corresponding Effect] computer networks, the laser oscillation wavelength trunk lines such as fiber optic communications is expected long-distance large-capacity communications 1.1
In the field of the μm band to the 1.7 μm band, there has been no surface emitting semiconductor laser capable of lowering the operating voltage, the oscillation threshold current and the like, generating less heat from the laser element and performing stable oscillation, and a communication system using the same. However, by devising a semiconductor distributed Bragg reflector as in the present invention, the operating voltage, oscillation threshold current, and the like can be reduced, the laser element generates less heat, and stable oscillation can be achieved. The system has been realized.

Further, conventionally, the control of the semiconductor laser has been realized by a complicated mechanism.
An optical communication system capable of controlling a semiconductor laser with a simple mechanism utilizing the L temperature characteristic has been realized.

[0094] [Claim 2 in the corresponding Effect] computer networks, the laser oscillation wavelength trunk lines such as fiber optic communications is expected long-distance high-capacity communication is 1.1μ
In the field of m band to 1.7 μm band, there is no long wavelength band surface emitting semiconductor laser that can be used stably and a communication system using the same. By using the surface emitting semiconductor laser device chip thus provided, stable oscillation became possible, and a practical optical communication system using this as a light emitting light source was realized.

Further, conventionally, the control of the semiconductor laser has been realized by a complicated mechanism.
An optical communication system capable of controlling a semiconductor laser with a simple mechanism utilizing the L temperature characteristic has been realized.

[Effects Corresponding to Claim 3] In such an optical communication system, a mechanism for monitoring the light amount is provided in the communication path, and the control current value is corrected based on the light amount. An optical communication system with reduced noise was realized.

[Effects Corresponding to Claim 4] In such an optical communication system, a mechanism for monitoring the light amount of the light receiving element on the receiving side is provided, the data is transferred to the transmitting side as data, and the control current value is corrected from the light amount. since performed, an optical communication system capable of reducing the effects of aging of the semiconductor laser can be realized.

[Effects Corresponding to Claim 5] In such an optical communication system, a light receiving element for receiving a signal is used as a mechanism for monitoring the light amount of the light receiving element on the receiving side, and the data is transferred to the transmitting side as data. Since the control current value is corrected from the light quantity, an optical communication system in which the influence of the aging of the semiconductor laser is reduced can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of an element part of a long-wavelength band surface emitting semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a configuration of a semiconductor distributed Bragg reflector of a long wavelength band surface emitting semiconductor laser according to an embodiment of the present invention.

FIG. 3 is a sectional view of an element portion of another configuration of a long-wavelength band surface emitting semiconductor laser according to an embodiment of the present invention.

FIG. 4 is a plan view showing a wafer substrate and a laser element chip on which a long wavelength band surface emitting semiconductor laser element according to one embodiment of the present invention is formed.

FIG. 5 is a diagram showing current-light output characteristics at different temperatures of the long-wavelength band surface emitting semiconductor laser device according to one embodiment of the present invention.

FIG. 6 illustrates setting of a current value from an upper limit and a lower limit of an optical output and an upper limit and a lower limit of an assumed temperature when a long wavelength band surface emitting semiconductor laser device according to an embodiment of the present invention is controlled by a current. FIG.

FIG. 7 is a diagram showing an example of a configuration in a case where a long wavelength band surface emitting semiconductor laser device according to an embodiment of the present invention is controlled by current, by monitoring the amount of light in a communication path and performing light emission control.

Continued on the front page (72) Inventor Kazuya Miyagaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Yukie Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Takeshi Kanai 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Watada Atsuyuki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Shunichi Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Satoru Satoru Satoru 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Shuichi Hikichi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Takuro Sekiya 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Shinji Sato Ota-ku, Tokyo 1-3-6 Nakamagome F-term in Ricoh Co., Ltd. (Reference) 5F073 AA51 AA65 AA74 AB17 BA02 CA07 CA17 DA05 DA14 DA27 DA35 EA15 GA12 5K002 AA07 BA13 CA11

Claims (5)

[Claims] In a laser chip and an optical communication system connected to the laser chip, the laser chip has an oscillation wavelength of 1.1 μm to 1.7 μm, and an active layer for generating light includes a main element of Ga, A surface emitting type having a layer structure of In, N, and As or a layer of Ga, In, and As and having a resonator structure including reflectors provided above and below the active layer to obtain a laser beam. A semiconductor laser element chip, wherein the reflecting mirror is a semiconductor distributed Bragg reflecting mirror that periodically changes a refractive index of a material layer constituting the reflecting mirror to small / large and reflects incident light by light wave interference; The material layer having a small ratio is Al _x Ga _{1 -x} As.
(0 <x ≦ 1) and then, the material layer of the refractive index is large is Al _y
A reflecting mirror having Ga _1-y As (0 ≦ y <x ≦ 1),
And a material layer Al _z Ga _{1 -z} As (0 ≦ y <z) in which the refractive index takes a value between small and large between the material layers with small and large refractive indexes.
An optical communication system using a surface-emitting type semiconductor laser device chip provided with <x ≦ 1) as a light emitting light source, wherein an upper limit and a lower limit of an optical output are set using a constant current power supply, and an upper limit and a lower limit of an assumed temperature. Controlling the semiconductor laser with a current value within the range of the current a obtained from the current-light output characteristic by the light output upper limit and the temperature lower limit and the current b obtained from the current-light output characteristic by the light output lower limit and the temperature upper limit. An optical communication system, comprising: 2. In a laser chip and an optical communication system connected to the laser chip, the laser chip has an oscillation wavelength of 1.1 μm to 1.7 μm, and has an active layer for generating light, wherein the main element is Ga, A surface emitting type having a layer structure of In, N, and As or a layer of Ga, In, and As and having a resonator structure including reflectors provided above and below the active layer to obtain a laser beam. A semiconductor laser device chip, wherein the reflecting mirror is a semiconductor distributed Bragg reflecting mirror that periodically changes the refractive index of a material forming the reflecting mirror to small / large and reflects incident light by light wave interference; Is smaller than that of Al _x Ga _{1 -x} As (0 <
x ≦ 1), and the material having a large refractive index is Al _y Ga _1-y A
s (0 ≦ y <x ≦ 1), wherein GaInP or GaInPAs is provided between the active layer and the reflector.
An optical communication system using a surface-emitting type semiconductor laser device chip provided with a non-radiative recombination prevention layer comprising a constant-current power supply, setting upper and lower limits of optical output, and setting an assumed temperature The semiconductor laser has a current value within the range of the current a obtained from the current-light output characteristic by the light output upper limit and the temperature lower limit by the upper limit and the lower limit, and the current b obtained from the current-light output characteristic by the light output lower limit and the temperature upper limit. An optical communication system characterized by controlling. 3. The optical communication system according to claim 1, further comprising a mechanism for monitoring a light amount in a communication path, a unit for converting the light amount into a current correction value, and a current correction value based on the light amount obtained from the light amount monitoring mechanism. 3. The optical communication system according to claim 1, wherein the semiconductor laser control is performed using a current value obtained by correcting the set current. 4. The optical communication system according to claim 1, further comprising a mechanism for monitoring a light amount of the light receiving element on the receiving side, and a means for converting the light amount to a current correction value. 3. The semiconductor laser control device according to claim 1, further comprising: transmitting the light quantity to the control mechanism on the transmission side as data, obtaining a current correction value from the light quantity, and controlling the semiconductor laser with the current value obtained by correcting the set current. The optical communication system according to claim 1. 5. An end portion of the communication path is a light receiving element on a receiving side, the light amount monitoring mechanism is the light receiving element, and the light amount of the light receiving element is transmitted as data to a control mechanism on a transmitting side. 4. The optical communication system according to claim 3, wherein a correction value of a current is obtained, and the semiconductor laser control is performed using the current value obtained by correcting the set current.