JP2002252429A - Optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical communications system which uses a surface light-emitting semiconductor laser chip whose operating voltage, lasing threshold current and the like can be reduced as a light-emitting light source and by which low-cost and high-capacity optical transmission can be performed. SOLUTION: The surface light-emitting semiconductor laser device chip is used as a light-emitting light source. An optical transmission line used for the communications system is an optical fiber which has a core and a grid. If the diameter of the core is D and the length of the optical fiber is L, 10<5> <=L/D<=10<9> is set.

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 the semiconductor laser formed on the InP substrate is that the characteristics greatly change 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.

[0007] However, conventionally, this only suggests the possibility of realizing a surface emitting semiconductor laser in a wavelength band longer than 0.85 µm, and such a device is not actually realized. 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. Or a device using a semiconductor layer made of AlInP, which is lattice-matched to the same substrate as the low refractive index layer of the semiconductor distributed Bragg reflector, as disclosed in JP-A-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 due to Al are likely to occur. In order to solve this problem, it is necessary to use a GaInNP containing no Al as disclosed in Japanese Patent Application Laid-Open Nos. 8-340146 and 7-307525.
There is a proposal for forming a semiconductor distributed Bragg reflector from GaAs and GaAs. However, the refractive index difference between GaInNP and GaAs is about half of the refractive index difference between AlAs and GaAs, and the number of stacked reflectors is very large, making it difficult to manufacture.

That is, at present, optical fiber communication is expected in a computer network or the like. However, a long wavelength band surface emitting semiconductor laser having a laser wavelength of 1.1 μm to 1.7 μm and a communication system using the same can be used. It does not exist and its appearance is longing for.

[0010]

According to the present invention, a laser oscillation wavelength used for such optical communication or the like is 1.1 μm or more.
1. Field of the Invention The present invention relates to a long-wavelength surface emitting semiconductor laser having a wavelength of 1.7 μm and an optical communication system using the same. The first object of the present invention is to use a surface emitting semiconductor laser device chip capable of lowering an operating voltage, an oscillation threshold current and the like as an emission light source. It is an object of the present invention to propose an optical communication system that enables large-capacity optical transmission at low cost. 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 that can be used stably as a light emitting light source, and to provide a practical long-wavelength surface emitting semiconductor laser. And an optical communication system that enables stable optical transmission using the same. A third object is to propose high-precision optical transmission in such an optical communication system.

[0011]

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.
<X ≦ 1) is used as a light emitting light source, and an optical transmission line used in the communication system is an optical fiber composed of a core and a clad. Is D and the length of optical fiber is L
In this case, 10 ⁵ ≦ L / D ≦ 10 ⁹ .

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.
A surface-emitting type semiconductor laser device chip provided with a non-radiative recombination preventing layer made of InPAs is used as a light emitting source, and an optical transmission line used in the communication system is an optical fiber including a core and a clad, When the diameter of the core is D and the length of the optical fiber is L, 10 ⁵ ≦ L /
D ≦ 10 ⁹ .

Thirdly, in the first and second optical communication systems, the optical transmission line amplifies a signal level via a repeater, and retransmits the signal to the next optical transmission line for transmission. did.

[0014]

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, a C (carbon) doped p-type
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, 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 study stage, 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 or by changing the Al composition continuously or stepwise. And formed.

More specifically, Al _z Ga _{1 -z} As (0 ≦
(y <z <x ≦ 1) The layer is formed so that the value of z of the layer changes from 0 to 1.0, that is, the ratio of Al to Ga gradually changes, such as GaAs to AlGaAs to AlAs. This is created by controlling the gas flow during layer formation as described above. Al and G
The ratio a may be formed so as to change 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 of 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.

In other words, providing such a material layer on a semiconductor distributed Bragg reflector is particularly effective for 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 it is a device.

As an example of a more detailed examination result for obtaining an effective reflectance, for example, for 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. But actually ± 1
Since a film thickness error of about% occurs, the target wavelength deviates from the wavelength having the highest reflectance. For example, if the target wavelength is 1.3
In the case of 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 structure 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.

Returning 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 whole surface-emitting type 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.

Further, in this example, the 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, except for the light emitting portion. An n-side electrode 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 is used. In the material containing Al (II
The ratio of the low refractive index layer of the lower and upper reflecting mirrors closest to the active layer is G.
It is set to _{a x In 1-x P y} As 1-y (0 <x <1,0 <y ≦ 1) non-radiative recombination preventing layer. Since the carriers are confined between the low-refractive index layers of the upper and lower reflecting mirrors which are closest to the active layer and have a wide gap, only the active region is constituted by a layer containing no Al (the percentage of group III is 1% or less). However, if the low-refractive index layer (wide gap layer) of the reflector in contact with the active region has a structure including Al, when carriers are injected and recombined, non-radiative recombination occurs at this interface, and the luminous efficiency is reduced. Will drop. 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, so that if there is a defect on the substrate surface, the growth proceeds 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. Band gap E
g is a direct transition, Eg (Γ) = 1.351 + 0.643x + 0.786
x ² , and Eg (X) = 2.24 + 0.02x in the indirect transition. Therefore, the active region and Ga _x In _{1-x Py} As _1-y (0
<X <1, 0 <y ≦ 1) The hetero barrier in the layer is large, so that the carrier confinement is good, the threshold current is reduced,
This has the effect of improving temperature characteristics.

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.

For example, a surface emitting laser having an oscillation wavelength of 1.3 μm band is preferably formed on a GaAs substrate, and a semiconductor multilayer mirror is often used as a resonator, and the total thickness is 5 to 8 μm. It is necessary to grow 50 to 80 semiconductor layers before growing the active layer. (On the other hand, in the case of an 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, various methods are used. Due to the cause (defects once generated basically creep up in the crystal growth direction and defects are generated at the hetero interface).
The defect density on the surface immediately before the active layer growth is inevitably higher than the defect density on the s substrate surface. 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, Al is not contained in the active region and at the interface between the reflecting mirror and the active region. Therefore, non-radiative recombination due to 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 that does not contain Al 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 at the time of growing 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 manufactured by the present inventors, a highly strained GaInAs quantum well active layer can be coherently grown thicker than before by a growth method with a high degree of non-equilibrium, such as growth at a low temperature of 600 ° C. or less. 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 has been found that a long-wavelength surface-emitting type semiconductor laser can be formed on a GaAs substrate by using GaInAs having a high In composition and a high compression strain for 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, the main elements of the active layer are Ga, In, and A.
s, that is, Ga _x In _{1 -x} As (GaInA
Although the example of the (s active layer) was shown, in order to perform laser oscillation of a longer wavelength, N was added, and the main elements were Ga, In, and
What is necessary is just to make it the layer (GaInNAs active layer) which consists of N and As.

By actually changing the composition of the GaInNAs active layer, it was possible to perform laser oscillation in each of the 1.3 μm band and the 1.55 μm band. By studying the composition, a longer wavelength, for example, 1.7
A surface emitting laser in the μm band is also possible.

Also, when GaAsSb is used for the active layer,
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.

In this case, as in the case of FIG.
00) is used. N-Al _x Ga _{1 -x} As (x = 0.9) and n-A at a thickness of 1/4 (λ / 4 thickness) of the oscillation wavelength λ in each medium.
n in which l _x Ga _1-x As (x = 0) are alternately stacked for 35 periods
Forming a semiconductor distributed Bragg reflector (Al _0.9 Ga _0.1 As / GaAs lower reflector) on which a λ / 4 thick n-Ga _{x
In 1-x P y As 1} -y (x = 0.5, y = 1) was laminated layer. In this example _{n-Ga x In 1-x} P y As 1-y (x = 0.
5, y = 1) layer is also a part of the lower reflecting mirror 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 reflector (upper reflector) is formed thereon.

The upper reflecting mirror is made of AlA to be a selectively oxidized layer.
s layer is sandwiched between a GaInP layer and an AlGaAs layer by 3λ /
4 low refractive index layer (thickness of (λ / 4-15 nm)
C-doped p-Ga_xIn_1-xP_yAs_1-y(X = 0.5, y
= 1) layer, C-doped p-Al _zGa_1-zAs (z = 1)
Selective oxidation layer (thickness 30 nm), thickness (2λ / 4-15)
nm) C-doped p-Al_xGa_1-xAs layer (x = 0.
9)), a GaAs layer having a thickness of λ / 4 (one period), and C
Doped p-Al_xGa_1-xAs layer (x = 0.9) and p-
Al_xGa_1-xAs (x = 0) layer in each medium
Periodic structure laminated alternately with a thickness of 1/4 times the oscillation wavelength
Structure (22 cycles)
Reflector (Al_0.9Ga_0.1As / GaAs upper reflector). What
Also in this example, since it becomes complicated in FIG. 3, it is illustrated.
Although omitted, the structure of the semiconductor distributed Bragg reflector is omitted.
The structure is a low refractive index layer (low refractive index layer) as shown in FIG.
Between the low refractive index and the high refractive index layer (high refractive index layer)
Material layer Al with a value between_zGa_1-zAs (0 ≦ y <z <
x ≦ 1).

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
%, And the N (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.

[0060] 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, the portion removed by mesa etching with polyimide (insulating film) is buried and flattened, the polyimide on the upper reflector is removed, and the 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 layer to be selectively oxidized is
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 semiconductor lasers (elements) of this example are integrated one-dimensionally or two-dimensionally, the controllability at the time of manufacturing the elements 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 <
Although the y ≦ 1) 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, No material containing Al is used in the active region, 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.

It is preferable to apply a structure in which Al is not contained at the interface between the reflecting mirror and the active region to the upper and lower reflecting mirrors as in this example, but it is effective to apply the structure to only 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.

Further, also in this example, the same idea as in the case of the example of FIG. 1 is applied to the lower reflector between the GaAs substrate and the active layer, so that crystal defects caused by Al which are problematic at the time of growing the active layer. Of the active layer is suppressed, and crystal growth of the active layer with high quality can be achieved.
Note that such a non-radiative recombination preventing layer forms a part of the semiconductor distributed Bragg reflecting mirror in any of the configurations shown in FIGS. 1 and 3, and thus has a thickness of one of the oscillation wavelength λ in the medium. / 4 times the thickness (thickness of λ / 4). Alternatively, a plurality of layers may be provided.

As is clear from the above description, a surface emitting semiconductor laser having high luminous efficiency and sufficient reliability for practical use was obtained by 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 obtained by selectively oxidizing the selectively oxidized layer,
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 oxidized to Al
By forming an 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 the convex lens, and the efficiency is extremely improved, and the threshold current 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, even in the configuration shown in FIG. 3, a 1.3 μm band surface emitting semiconductor laser can be realized similarly to the case of 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, the example of the triple quantum well structure (TQW) as the stacked structure of the active layer has been described, but a structure using other quantum wells (SQW, DQW, MQW) or the like can also 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. in this way,
Conventionally, there is no suitable material for the semiconductor laser having a wavelength of 1.1 μm to 1.7 μm, but GaInAs, G
By using aInNAs and GaAsSb and providing a non-radiative recombination prevention layer, a high-performance surface-emitting laser can be realized in the long wavelength region of the 1.1 μm to 1.7 μm wavelength band where stable oscillation has conventionally been difficult. As a result, application to optical communication systems 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.

FIG. 5 shows an example of an optical fiber used in a communication system using a long wavelength band surface emitting semiconductor laser, which functions as an optical transmission line for receiving laser light emitted from a laser element light emitting section and transmitting it. An optical fiber comprising a core and a cladding, wherein the diameter of the core is D and the length of the optical fiber is L, the fiber length is set such that 10 ⁵ ≦ L / D ≦ 10 ⁹ 1 shows a cross section of an optical fiber intended to guide light along. Conventionally, an optical communication system with a laser oscillation wavelength in the 0.85 μm band has been studied, but the transmission loss of the optical fiber is large and is not practical. Although a stable laser element could not be obtained in a practical long wavelength band where transmission loss was small, the present invention devised a semiconductor distributed Bragg reflector or provided a non-radiative recombination prevention layer as described above. The laser oscillation wavelength from 1.1 μm band
Energy saving 1.7 μm surface emitting semiconductor laser
Low heat generation and stable driving have become possible, and a practical long wavelength band optical communication system has become possible.

FIG. 6 shows an application of the above-described long-wavelength-band surface-emitting type semiconductor laser LD chip and optical fiber to long-distance communication. The first optical fiber having an optical fiber core diameter D of 50 μm and an optical fiber length L of 5 km, which receives the emitted laser light and serves as a transmission path for transmitting the laser light, and the first optical fiber A second optical fiber having an optical fiber core diameter D of 50 μm and an optical fiber length L of 5 km acting as a transmission path for receiving the emitted laser light and transmitting the laser light, and an output from the second optical fiber. And a photodiode chip having a photodetector unit for receiving the laser beam.

There is a connection module between the LD and the first optical fiber between the semiconductor laser LD chip and the first optical fiber, and the two are optically coupled.
Similarly, between the second optical fiber and the photodiode chip, a connection module between the second optical fiber and the photodiode is interposed and optically coupled. First
A repeater is installed between the second optical fiber acting as a transmission path for receiving and transmitting the laser light emitted from the optical fiber, and amplifies the signal to the original signal output here, and the second optical fiber. Since the signal is transmitted to an optical fiber, long-distance transmission is possible without lowering the output signal. The first and second optical fibers used here are usually manufactured with a winding unit of several thousand km, but due to quality defects such as the generation of air bubbles in the optical fiber generated during the manufacturing process, several 100 km
Winding up in units. Further, the transmission length L to the relay device due to propagation loss or the like is generally used for communication as a practical length of 5 m to 50 km when the core diameter is 50 μm, for example. If the transmission distance is longer than 50 km, transmission becomes impossible due to transmission loss. Therefore, it is necessary to provide a relay point and amplify the signal. Also 5
If it is shorter than m, other means exist even if it is not necessarily such an optical communication system.

The diameter D of the optical fiber core used here can be a single glass fiber having a diameter of several μm to a plastic optical fiber having a diameter of several hundred μm.

FIG. 7 shows a silica glass optical fiber having an optical fiber core diameter D of 50 μm. Two optical fibers having a transmission length L of 500 m are bundled, separated at a light receiving end and a light emitting end, respectively, and bidirectional light is emitted. Communicating.

Here, a long wavelength band surface emitting semiconductor laser L
A D chip and a photodiode chip having a photodetector unit for receiving laser light emitted from the optical fiber are paired,

The first laser beam emitted from the light emitting section of the laser element serves as a transmission path for receiving and transmitting the laser beam.
Optical fiber and

A photodiode chip having an optical detector for receiving the laser light emitted from the first optical fiber,

A connection module between the LD and the first optical fiber is provided between the long wavelength band surface emitting semiconductor laser LD chip and the first optical fiber, and both are optically coupled.

Similarly, between the first optical fiber and the photodiode chip, a connection module for connecting the first optical fiber and the photodiode is interposed and optically coupled.

This configuration is installed in reverse, and bidirectional optical communication is enabled.

The number of combinations of a long wavelength band surface emitting semiconductor laser LD chip, a photodiode chip, and a fiber as one unit is not limited to this, and one surface emitting laser as in the present invention is used. Since a plurality of (n) light-emitting elements can be formed on the laser chip, a large-capacity communication system can be realized by a combination of n light-emitting elements and n fibers.

FIG. 8 shows an application example of a fluorinated plastic optical fiber having a core diameter of 100 μm to a high-speed multimedia network having a transmission length of less than 100 m. Here, the optical fiber core diameter D is 50 μm and the length is 50K from the optical line terminal.
and a second optical fiber having a diameter D of 50 μm and a length of 1 km acting as a transmission path for receiving and transmitting the laser light emitted from the first optical fiber and the first optical fiber. Fifty fusion-spliced fiber lengths of 50 km are used to transmit high-speed information on the order of Gbps over a total length of 100 km over a long distance. Since signal attenuation occurs due to the propagation loss of the silica glass optical fiber, the optical signal is amplified to the original output by a repeater with the function of amplifying the optical signal,
Transmitting to a second optical fiber.

The optical signal from the second optical fiber once enters a network terminator, is converted into an optical-electrical signal, is divided into the required number of terminals on an electric circuit, and then is converted into an optical signal as shown in FIG. Light is output to each port using the communication system. For optical transmission to each port, a third optical fiber having an optical fiber core diameter of 100 μm and a length of 10 m, a fourth optical fiber having an optical fiber core diameter of 100 μm and a length of 50 m,
A fifth optical fiber having an optical fiber core diameter of 100 μm and a length of 100 m is used. Laser light emitted from the third, fourth, and fifth optical fibers is received by a photodiode chip (not shown) having a light detector unit for receiving light, and is converted into an electric signal. On the other hand, the transmission from the terminal device also receives the laser light emitted from the laser element light emitting unit (not shown), and the second optical fiber acting as a transmission path for transmitting the laser light, and the second optical fiber emerges from the second optical fiber. Laser light is received by a photodiode chip having a photodetector section. Since the core diameter is as large as 100 μm, alignment with a high-precision lens system is not required, and it is possible to connect to office and home equipment very easily.

Also in this case, the relationship between the diameter D of the core and the length L of the optical fiber satisfies 10 ⁵ ≦ L / D ≦ 10 ⁹ . In other words, if the transmission distance is longer than 100 km, transmission becomes impossible due to transmission loss. Therefore, it is necessary to provide a relay point and amplify the signal. In the case where the length is shorter than 10 m, other means exist even if it is not necessarily such an optical communication system.

FIG. 9 shows an example of application to a hybrid optical integrated device using a long wavelength band surface emitting semiconductor laser. The long wavelength band surface emitting semiconductor laser of the present invention is mounted on a ceramic substrate.
A rectangular core having a 7 × 7 μm core dimension and a diagonal length D of about 10 μm, which functions as a transmission path for receiving the laser light emitted from the laser element light emitting section and transmitting it, and having a length L of the optical waveguide Is 1 cm, a first optical waveguide having an optical fiber core diameter D of 100 μm, and an optical fiber length L acting as a transmission path for receiving and transmitting laser light emitted from the first optical waveguide. A 100 m first optical fiber, a rectangular core having a 7 × 7 μm core dimension and a diagonal length D of about 10 μm, which functions as a transmission path for reception installed on a ceramic substrate, and the length L of the optical waveguide is It comprises a 1 cm second optical waveguide, a photodiode chip having a photodetector for receiving laser light emitted from the second optical waveguide, and a preamplifier.

Further, a connection module for connecting light emitted from the first optical waveguide to the first optical fiber is interposed between the first optical waveguide and the first optical fiber, and optically coupled.

At the end of the first optical fiber, there is provided a photodiode chip having an optical detector for receiving light and a connection module for connecting light emitted from the first optical fiber to the photodiode. It is coupling. Similarly, a connection module for receiving the laser light emitted from the laser element light emitting unit and connecting to the first optical fiber is interposed and optically coupled.

Similarly, between the second optical fiber and the second optical waveguide, a connection module for connecting the light emitted from the second optical fiber to the second optical waveguide enters and optically couples. .

At the end of the second optical fiber, a long wavelength band surface emitting semiconductor laser of the present invention and a connection module for connecting to the second optical fiber acting as a transmission path for transmitting the laser are provided. It is coupling.

As the optical waveguide, a quartz optical waveguide composed of a core and a clad was formed by photolithography using a silicon wafer substrate, and a preamplifier was installed on a ceramic substrate on which the quartz optical waveguide was mounted.

[0097]

(Effect corresponding to Claim 1) The laser oscillation wavelength at which optical fiber communication is expected, such as a computer network or a trunk system for long-distance large-capacity communication, is 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, by defining the length of the optical fiber with respect to the core diameter of the optical fiber, efficient terminal processing of the optical fiber becomes easy, and highly reliable and low-cost optical communication can be realized.

(Effect Corresponding to Claim 2) The laser oscillation wavelength at which optical fiber communication is expected to be 1.1 μm, such as a computer network or a trunk system for long-distance large-capacity communication, is 1.1 μm.
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. Furthermore, by defining the length of the optical fiber with respect to the core diameter of the optical fiber, the mechanical strength of the optical fiber was secured and stable optical communication was realized.

(Effect Corresponding to Claim 3) In such an optical communication system, the transmission path amplifies the signal level via the repeater, and retransmits and transmits the signal to the next optical transmission path, thereby achieving high precision and high accuracy. Stable optical communication was 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 the long-wavelength band surface emitting semiconductor laser according to one 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 sectional view of an optical fiber connected to a long wavelength band surface emitting semiconductor laser according to an embodiment of the present invention.

FIG. 6 is a plan view showing an optical communication system using a long wavelength band surface emitting semiconductor laser according to an embodiment of the present invention and an optical fiber to be connected.

FIG. 7 is a plan view showing a bidirectional optical communication system using a long-wavelength band surface emitting semiconductor laser according to an embodiment of the present invention and a connecting optical fiber.

FIG. 8 is a plan view showing a long-wavelength band surface emitting semiconductor laser according to an embodiment of the present invention and an in-building LAN in which functions of an optical fiber to be connected are separated.

FIG. 9 is a plan view showing a long wavelength band surface emitting semiconductor laser and an integrated optical communication device according to an embodiment of the present invention, and a cross-sectional view of an optical waveguide.

Continued on the front page (72) Inventor Masayoshi Kato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Kazuya Miyagaki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company (72) Inventor Akira Sakurai 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Atsuyuki Watada 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Shinji Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Shunichi Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Satoru Sugawara, Inventor 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Yukie Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Takuro Sekiya, Inventor Takuro Sekiya, Tokyo 1-3-6 Nakamagome F-term in Ricoh Co., Ltd. (Reference) 5F073 AA74 AB17 AB28 BA01 CA07 CB02 DA05 DA22 EA23 FA07

Claims (3)

[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.
<X ≦ 1) is used as a light emitting light source, and an optical transmission line used in the communication system is an optical fiber composed of a core and a clad. Is D and the length of optical fiber is L
An optical communication system, wherein 10 ⁵ ≦ L / D ≦ 10 ⁹ . 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 transmission line used in the communication system is an optical fiber comprising a core and a clad, the surface emitting type semiconductor laser device chip provided with a non-radiative recombination prevention layer comprising a core and a clad. Where D is the diameter of the optical fiber and L is the length of the optical fiber, and 10 ⁵ ≦ L / D ≦ 10 ⁹ . 3. The optical communication system according to claim 1, wherein the optical transmission line amplifies a signal level via a repeater, and retransmits the signal to a next optical transmission line for transmission.