JP2000151025A - Optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system driven with low power consumption, such as an optical information processing device and optical communication system. SOLUTION: For an optical system, a light source is a semiconductor light- emitting device wherein a waveguide structure of an embedded structure comprising at least a light-absorbing layer 6, a transparent layer 7, and a crystal relaxation layer 8 is applied. An optical system of low power consumption is provided by applying a semiconductor laser device of low-threshold high-efficiency operation to the optical system. In the semiconductor light-emitting device, a waveguide of lower defective, higher crystal quality, and significantly smaller optical loss than the waveguide of conventional technology is formed for good reproducibility. A part of the embedded layer is utilized as a channel for current injection, for suppressing element resistance and satisfying the system operation voltage specifications.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system. Representative forms of the optical system according to the present invention are an optical information processing apparatus and an optical communication system. Further, the present invention relates to a semiconductor light emitting device, particularly a semiconductor laser device, most suitable for providing a light source for these optical systems.

[0002]

2. Description of the Related Art An optical information processing apparatus and an optical communication system, which are typical forms of an optical system according to the present invention, will be exemplified.

Examples of the optical information processing apparatus according to the present invention include an optical disk apparatus such as a compact disk (CD) and a digital video disk (DVD) and an optical recording apparatus such as a laser beam printer. it can. An optical disc device is an optical recording device having at least a light source for irradiating a recording medium with light and a detector for detecting reflected light from the recording medium. Needless to say, there is an optical information processing apparatus that performs recording by changing the state of a part of a recording medium by light. On the other hand, a laser beam printer is a printing apparatus that irradiates a laser beam to write print information on a photoconductor as a recording medium and obtains a printed image by an electrophotographic method.

An example of the configuration of the optical information processing apparatus so far is as follows. The basic configuration includes a disk provided with an optical recording medium for optical recording, a motor for rotating the disk, an optical pickup, and a control unit for controlling these. The optical pickup includes a lens system, a light source such as a semiconductor laser device, and a photodetector.

[0005] There are various reports on the general matters of such optical disk devices, but they will be briefly described. Depending on the type of recording material, optical disc devices are roughly classified into read-only type (R
OM type), write-once type, and rewritable type. The reproduction of information is performed by optically reading a change in the reflected light from the minute holes (the state change portion of the recording medium) recorded on the disk with a photodetector. Incidentally, an ordinary optical recording medium can be used.

[0006] In the case of the read-only type, the recording information is recorded in advance on a recording medium. For example, aluminum, plastic, and the like can be given as typical examples of the read-only type recording medium.

In recording, the laser light is focused on a recording medium on the disk to a fine light spot, and the laser light is modulated according to the information to be recorded, thereby thermally changing the state of the recording material. Record in rows. This recording is performed while the disk is rotated (moved) by a motor.

As a light source of such an optical information processing device, a semiconductor light emitting device, especially a semiconductor laser device is used.

The outline of the optical transmission, transmission and reception system is as follows. Since an optical input is generally multiplex-transmitted, light having a predetermined wavelength is split by a splitter. Then, the light from the semiconductor laser device, which is the light source, and the laser light for amplifying the fiber amplifier and the input light are mixed by a mixer and input to the fiber amplifier. The semiconductor laser device is generally cooled by a cooling device, and these components are controlled by an automatic control device.

In general, on the transmitting side, each channel is arranged on a frequency axis with a carrier modulated by original information according to an allocation order, and a transmission signal is synthesized by an optical multiplexer.
On the receiving side, on the other hand, the original signal is reproduced by passing the signal separated in frequency by the optical demultiplexer through an optical detection / demodulation circuit provided for each channel. Two-way transmission over one fiber is performed.

As a light source of such an optical transmission system, a semiconductor light emitting device, especially a semiconductor laser device is used.

Next, a semiconductor light emitting device used as a light source of the above various optical systems will be described.

Conventionally, various attempts have been made to improve the performance of a semiconductor light emitting device, particularly a semiconductor laser device, but there are few cases in which a highly reliable technology has reached a commercialization level. A typical example of a device-level manufacturing technology at the product level for increasing the output of a laser device serving as a light source of an optical information processing device is a method of forming a transparent window structure at an end face of a resonator by impurity diffusion. An example of this is Iii Journal Quantum Electronics, Vol. 29, 1993, 6
No. 1874-1879 (IEEE J. Quantum Electron. 1993, vol.2
9, No. 6, pp. 1874-1879) [Reference 1]. In Document 1, although the contribution to the improvement of the high output characteristics is made, the operation current and the operation voltage at the time of the high output are increased, and thus the contents of the system device are not satisfied.

Further, as a waveguide structure of a laser element, it has been studied to reduce the internal light loss of guided laser light by using a material having a large band gap for a buried layer. An example of this is Electronics Letters 1996.
Vol. 32, No. 10, pp. 894-896 (Electron. Lett. 1996, vol. 32,
No. 10, pp. 894-896) [Reference 2].
Here we report that the threshold current was improved by 10-20% and the internal light loss was improved by 30-40%. However, this example cannot be applied to a waveguide structure that achieves high output characteristics of an optical output of 10 mW or more, and has a sufficiently large effect on reduction of threshold current and internal optical loss and increase of efficiency. I can't say.

[0015]

Problems of the prior art will be described with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing an example of the configuration of a ridge stripe which is the basis of the present invention. Based on this state, an embedded semiconductor laser device is formed. 2 and 3 are views showing an example of a conventional embedded semiconductor laser device. These are all cross-sectional views on a plane intersecting the optical axis of the laser resonator.

A typical example of a waveguide in a semiconductor laser device is a buried structure in which both sides of the waveguide are buried. As shown in FIG. 1, an optical waveguide layer 2, a light emitting active layer 3 and an optical waveguide layer 4 are provided on a semiconductor substrate 1, and for example, each semiconductor layer is formed on the optical waveguide layer 4 by using an insulating film mask 5. Are etched to form a so-called ridge stripe, and a buried structure is formed with respect to this waveguide shape.

FIG. 2 shows an example of a conventional waveguide.
In this example, a complex refractive index waveguide structure mainly utilizing absorption loss has been adopted by embedding a laser light absorbing layer 6 such as a GaAs semiconductor on both sides of the waveguide. This prior art is also described in the aforementioned reference 1.
Although a refractive index waveguide structure is provided by a GaAs buried layer that absorbs laser light, there is a limit to improving the threshold current and the slope efficiency because the internal light loss due to the absorption layer is large.

The example shown in FIG. 3 is a structure that compensates for the disadvantage of the example shown in FIG. That is, the internal light loss is reduced by using a transparent layer 7 using a material having a large forbidden band width that does not absorb laser light.

This prior art is disclosed in the aforementioned reference 2. That is, as shown in FIG. 3, an AlInP semiconductor transparent layer, which is a material having a large forbidden band width and a small refractive index, is used as the above-mentioned transparent layer 7 as a part of the buried layer. For this reason, it becomes possible to reduce internal light loss,
It is possible to reduce the threshold current and increase the slope efficiency.

However, A used for the buried layer
Since the lInP semiconductor layer has a high aluminum (Al) composition, reproducibility is poor for maintaining a good surface state. This is because oxygen is more likely to be taken in than in the initial growth to form a deep level, crystal defects are likely to be generated at a high density, and the surface morphology is easily affected by the state of the underlayer. For this reason, a new method is desired in order to manufacture the buried layer with high quality and to further reduce internal light loss in the waveguide.

[0021]

SUMMARY OF THE INVENTION An optical system according to the present invention is to provide an optical system having stable transmission characteristics and lower power consumption. In the present specification, a system or an apparatus having a semiconductor light emitting device as a light source is generally called an optical system. Representative forms of the optical system according to the present invention are an optical communication system and an optical information processing device. Further, examples of such an optical information processing device include an optical disk device such as a compact disk (CD) and a digital video disk (DVD) and an optical recording device such as a laser beam printer device.

The semiconductor light emitting device of the present invention, particularly a semiconductor laser device, provides a semiconductor light emitting device that achieves a high output stable operation and reduces the operating current during the high output operation.

Further, the semiconductor light emitting device of the present invention, particularly a semiconductor laser device, provides a semiconductor laser device which achieves a low threshold and high efficiency operation, reduces an operating current at the time of a high output operation, and reduces an operating voltage. It is something you want to do.

The main modes of the present invention are as follows.

(1) A first embodiment of the present invention is an optical system having a semiconductor light emitting device having a waveguide structure on a top of an active layer, which enables a laser to oscillate in a transverse fundamental mode. In the waveguide structure of the semiconductor light emitting device, the lateral basic mode of the oscillating light is substantially controlled by a real refractive index difference, and a gap between a material layer for providing the real refractive index difference and the active layer. An optical system comprising at least a crystal relaxation layer.

(2) A second aspect of the present invention is the optical system according to the above (1), wherein the crystal relaxation layer has lattice distortion.

(3) In a third mode of the present invention, the crystal relaxation layer is composed of a compound semiconductor layer containing substantially no aluminum. (1) or (2). Optical system.

(4) In a fourth mode of the present invention, the crystal relaxation layer has a desired conductivity type, and the crystal relaxation layer forms a part of a carrier injection path of the semiconductor light emitting device. (1), (2), or (3)
An optical system according to (1).

(5) A fifth aspect of the present invention is the optical system according to the above (1), (2), (3) or (4), wherein the active layer has a quantum well structure. It is.

(6) A sixth embodiment of the present invention is an optical information processing apparatus having a semiconductor light emitting device having a waveguide structure on a top of an active layer, which enables a laser to oscillate in a transverse fundamental mode. The waveguide structure of the semiconductor light emitting device controls the lateral fundamental mode of the oscillating light substantially by the real refractive index difference, and the material layer for providing the real refractive index difference and the active layer An optical information processing device comprising at least a crystal relaxation layer between the two.

(7) An optical information processing apparatus according to the above (6), wherein the crystal relaxation layer is composed of a compound semiconductor layer containing substantially no aluminum. It is.

(8) An eighth aspect of the present invention is an optical communication system having a semiconductor light emitting device having a waveguide structure on a top of an active layer, which enables a laser to oscillate in a transverse fundamental mode, In the waveguide structure of the semiconductor light emitting device, a lateral basic mode of oscillation light is substantially controlled by a real refractive index difference, and a material layer for providing the real refractive index difference and the active layer are different from each other. An optical communication system comprising at least a crystal relaxation layer in between.

(9) The optical communication system according to the above item (8), wherein the crystal relaxation layer is formed of a compound semiconductor layer containing substantially no aluminum.

Next, main modes of the semiconductor light emitting device according to the present invention will be enumerated.

(10) In the first embodiment of the semiconductor light emitting device according to the present invention, the waveguide structure forming the light emitting region is formed by setting a buried structure, and the buried structure has a laminated structure and has a crystal structure. An optical waveguide with low optical loss is formed by a combination of a relaxation layer and a transparent layer or a combination of a crystal relaxation layer, a transparent layer, and a light absorption layer. A semiconductor light emitting device having a waveguide structure having a self-aligned structure for current operation.

(11) A second embodiment of the semiconductor light emitting device according to the present invention is the semiconductor light emitting device according to the above item (10), wherein the semiconductor laser element is formed by forming the waveguide structure. is there.

(12) A third embodiment of the semiconductor light emitting device is as follows.
In the above item (11), lattice strain may be introduced into the crystal relaxation layer which is a part of the buried structure having the laminated structure, and tensile or compression strain is introduced into the crystal relaxation layer itself. It is a semiconductor light emitting device.

(13) A fourth embodiment of the semiconductor light emitting device is as follows.
In the above item (10) or (11), the crystal relaxation layer which is a part of the buried structure having a laminated structure is a semiconductor layer containing no Al as a constituent element, and the crystal relaxation layer itself is a laser propagating through the waveguide. It is a semiconductor light emitting device that may be a layer that absorbs light or is formed of a layer that is transparent to laser light.

(14) A fifth embodiment of the semiconductor light emitting device is as follows.
In the above paragraph (13), conductivity-type impurities are introduced into the crystal relaxation layer which is a part of the buried structure having a laminated structure, and the crystal relaxation layer serves as a current path to inject carriers into the light emitting active layer. A semiconductor light emitting device characterized in that the light emitting device is capable of:

(15) A sixth embodiment of the semiconductor light emitting device is as follows.
In the above item (10), the transparent layer which is a part of the buried structure having the laminated structure is constituted by a transparent layer which does not absorb the laser light propagating through the waveguide, and the transparent layer is made of Al as a constituent element. May be formed by a semiconductor layer containing.

(16) A seventh embodiment of the semiconductor light emitting device is as follows.
In the preceding items (10) and (11), the waveguide structure is
A ridge stripe is formed in the optical waveguide layer for the light emitting active layer having a small forbidden band width and a high refractive index and a low refractive index for the optical waveguide layer constituting the semiconductor laser element, A semiconductor light emitting device in which both sides of the ridge stripe are formed by the buried structure.

(17) An eighth embodiment of the semiconductor light emitting device is as follows.
In the above items (10), (11) and (16), the transparent layer which is a part of the buried structure having the laminated structure is smaller than the refractive index of the optical waveguide layer forming the ridge stripe of the semiconductor laser device, or It is the same semiconductor light emitting device.

(17) A ninth embodiment of the semiconductor light emitting device is as follows.
The buried structure constitutes a refractive index guide for stably controlling the fundamental transverse mode, and the refractive index guide is achieved by providing a difference in the real part of the refractive index in the lateral direction of the active layer. A semiconductor light emitting device characterized in that a stripe structure is formed.

(18) In a tenth embodiment of the semiconductor light emitting device, the light emitting active layer uses a multiple quantum well structure.
More preferably, the semiconductor light emitting device is provided as a strained multiple quantum well structure in which lattice strain is introduced.

(19) In the eleventh embodiment of the semiconductor light emitting device, a single crystal substrate provided with an optical waveguide layer and a light emitting active layer has a substrate plane orientation of 54.7 degrees (0) from 0 from the (100) plane.
1) A substrate having an off-orientation in the range up to the plane and preferably having an off-orientation in the range of 5 to 16 degrees is used. A semiconductor light emitting device having a waveguide.

[Detailed Description of Semiconductor Light Emitting Device] First, a semiconductor light emitting device according to the present invention will be described in detail with reference to FIGS. These are all cross-sectional views on a plane intersecting the optical axis of the laser resonator. FIG. 6 shows an example of a conventional embedded semiconductor laser device.

The object of the present invention is to improve basic characteristics such as threshold current and efficiency while ensuring high output characteristics. Still another means of the present invention is to achieve low power consumption driving of the semiconductor laser device by reducing the operating voltage. The method will be described below in comparison with a conventional semiconductor laser device.

The essence of the semiconductor light emitting device of the present invention is based on the waveguide structure illustrated in FIG. 3 as a conventional technique, and the buried layers on both sides of the ridge stripe are made of GaAs containing no aluminum (Al) element. GaInP,
The purpose is to introduce a compound semiconductor material such as GaInAsP as a crystal relaxation layer of a thin film. This crystal relaxation layer may be a thin film layer and may have a forbidden band width lower than the energy of the laser beam. This crystal relaxation layer is approximately 10n
m to 100 nm, more preferably 20 nm to 50 n
Set to a thickness of about m.

Since the crystal relaxation layer does not substantially contain the Al element, it is difficult for crystal defects to occur in the compound semiconductor layer on which the crystal is grown, specifically, in each buried layer on both sides of the ridge stripe. The surface condition of the crystal growth surface can be favorably maintained. The thickness of the crystal relaxation layer is set to such an extent that its optical characteristics do not basically affect the laser oscillation. Therefore, while ensuring sufficient crystallinity of the buried layer, which has been a problem in the conventional buried semiconductor laser device, it is possible to control the transverse fundamental mode of the laser by the difference in the real refractive index with respect to the laser light, and It is possible to suppress an increase in the oscillation threshold value due to the insertion of the transparent layer for providing the difference.

In the specification of the present application, a layer which changes the complex refractive index difference for controlling the transverse fundamental mode of the laser beam is generally called an "absorption layer". In general, the horizontal basic mode of laser light
A layer that causes a difference in the actual refractive index for controlling the wavelength is generally called a “transparent layer”.

In general, a GaAs layer that absorbs laser light from the active layer is used for controlling the transverse fundamental mode of the laser by controlling the complex refractive index. According to the example of FIG. Here, light absorption corresponds to a change in the complex part of the refractive index. On both sides of the step portion of the semiconductor layer 4 constituting the waveguide, the complex refractive index differs between the central portion and the outer portion, and the horizontal fundamental mode of the laser light is controlled based on this difference. For controlling the lateral fundamental mode, stable control can be performed not only by setting the complex refractive index by the absorption layer but also by setting the real part difference of the refractive index. .

The buried layer according to the present invention includes:
A layer called "transparent layer" is inserted. Even with the introduction of the transparent layer 7, the lateral basic mode of the laser light is stably controlled to a waveguide structure having a real refractive index difference. Also,
Introducing this transparent layer can be regarded as a layer for adjusting and designing the degree of change of the complex refractive index by the above-mentioned absorption layer. AlGaIn for the transparent layer
P, AlInP, AlGaAs, or the like is used. The crystal quality of these transparent layers depends on the introduction of the crystal relaxation layer and the growth conditions including the film thickness. In order to reduce the defect density of the transparent layer and reduce the scattering loss of the waveguide, it is important to control the material and thickness of the crystal relaxation layer. The thickness of the transparent layer is set in consideration of the distance between the active layer and the absorption layer, the thickness of the crystal relaxation layer, and the like.

That is, the absorption layer is moved away from the active layer by the transparent layer, and the complex refractive index difference is weakened to form a waveguide structure based on the actual refractive index difference. The waveguide light loss of the absorption layer is reduced by the thickness of the transparent layer. An adjustable waveguide can be formed. At this time, it is very important to reduce the optical loss of the waveguide by introducing the waveguide in order to achieve low threshold and high efficiency operation of the laser element. At this time, the design of the waveguide structure is determined mainly by the thickness of the transparent layer and the real part of the refractive index, and the optical loss of the waveguide depends on the thickness of the transparent layer and the good crystal quality that causes scattering loss. I do.

The structure of the active layer may be a bulk active layer or a quantum well structure depending on the purpose of use, and may be a single quantum well, a multiple quantum well, a quantum well that becomes a strained superlattice, or the like. It is of course possible.

In the following example of a semiconductor laser device, an example of a Fabry-Perot resonator is shown, but the present invention does not depend on the type of the resonator. That is, the semiconductor laser device according to the present invention is a distributed feedback (DFB) type or a Bragg (DB) type.
Naturally, it is also possible with an R) type laser. Also,
Naturally, means of a general semiconductor laser device such as protection of the light emitting surface of the resonator and use of various buffer layers for improving the crystallinity of each crystal layer can be used.

Hereinafter, various examples of the semiconductor laser device according to the present invention will be described.

FIG. 4 shows a basic example of the present invention. In the present invention, AlGaAs or AlGaIn
After forming a ridge stripe on the optical waveguide layer of a laser element made of a P material or the like, as shown in FIG. 4, the buried layer contains GaAs, GaInP or G containing no Al element.
First, a thin film of an aInAsP layer is introduced as a crystal relaxation layer 8, and thereafter, AlGaAs or AlGaI having a large forbidden band width is used.
This was a step of providing a transparent layer 7 of an nP layer and an absorption layer 6 of a GaAs layer. It has been found that the crystal quality of the transparent layer 7 containing the Al element can be remarkably improved by providing the crystal relaxation layer 8 according to the present method. When the crystal relaxation layer 8 is provided, according to microscopic observation, the crystal defects of the transparent layer 7 are 105 / cm ^2.
From the order of 102 / cm ² to the order of 102 / cm ² . Also, the surface irregularities were reduced, the surface morphology was improved, and the flatness of the crystal surface was improved.

FIGS. 7 and 8 show an example of a structure for effectively increasing the width of the current constriction. In this example, the barrier relaxation layer (1
0, 11). The barrier relaxation layers (10, 11) mainly include GaInP and GaInA.
A compound semiconductor of s or GaInAsP can be used. Its thickness is about 10 nm to about 100 nm. It is also possible to adopt a structure in which the above-mentioned crystal relaxation layer has the role of this barrier relaxation layer.

FIGS. 7 and 8 show the embedded structure of this method.
When fabricated in the form of an element described above, it was found that the internal optical loss of the waveguide can be reduced by 60-70% as compared with the element having the conventional structure. In the conventional device having the embedded structure shown in FIG. 2, the internal optical loss of the waveguide is 21 / cm-25 / cm, whereas in the device having the embedded structure of the present invention shown in FIGS. Was able to be reduced to 6 / cm-9 / cm. As a result, the threshold current of the laser element can be reduced,
Efficiency can be expected to be improved, and low threshold and high efficiency operation of the device can be achieved. In the characteristics of this device, it was possible to reduce the threshold current by 30-40% and improve the slope efficiency by 30-40%.

Another example is shown in FIG. This example has a structure that is advantageous for suppressing a reactive current that does not contribute to laser light oscillation. As shown in FIG. 5, after the ridge stripe is formed so as to reach the light emitting active layer 3, a crystal relaxation layer 8 is first provided, and then the thick transparent layer 7 is extended to the height of the absorbing layer 6 in FIG. Then, the absorbing layer 6 is provided as in FIG. Thereby, the reactive current which does not contribute to the oscillation of the laser light, which is generated in the optical waveguide layer 4 on both sides of the ridge stripe in FIG. 4, is extremely suppressed, and almost no current is injected into the light emitting active layer 3 through the ridge stripe. It can be used to effectively generate laser light gain. as a result. With the framed structure shown in FIG. 5, it becomes possible to operate the laser element with a low threshold and low operating current. As compared with the case of FIG. 4, a current of 5 to 10 mA could be suppressed.

Further, introducing lattice strain into the crystal relaxation layer 8 of FIGS. 4 and 5 is also effective for improving the characteristics of the laser device. That is, when lattice strain is introduced into the crystal relaxation layer 8, the stress applied in the lateral direction of the light emitting active layer 3 can be adjusted, and the carrier confinement in the lateral direction of the active layer can be improved. By introducing a tensile strain into the crystal relaxation layer 8, a compressive stress is generated in the region on both sides of the ridge stripe, and the band gap of the region of the light emitting active layer can be increased. For this reason, in the light emitting active layer region immediately below the ridge stripe that is not subjected to the compressive stress by the crystal relaxation layer 8, a barrier is formed in the lateral direction, thereby improving the effect of confining injected carriers. By improving the confinement of the injected carriers, the low threshold current, the low operating current, and the temperature characteristics of the laser element can be improved.

Next, it will be described that the operating voltage can be reduced by the present method as compared with the conventional device.

It is clear that the operation voltage of the device can be lower than that of the conventional device because a low operation current can be achieved based on the low threshold value and high efficiency operation by the above effect of the present method. In addition, in the present method, a further lower operating voltage is possible by applying the crystal relaxation layer 8 to the current injection path. In the conventional device, for example, when the contact layer 9 is provided as shown in FIG. 6 to form the device with respect to the buried structure of FIG. 3, the confinement is performed by the buried layers 6 and 7 which also serve as a current confinement layer. The width is the width W1 above the ridge stripe. On the other hand, in the present method, in consideration of the barrier difference between the optical waveguide layer 4 and the contact layer 9 during carrier injection, the layer 1 is formed on the ridge stripe shown in FIGS.
By providing a barrier relaxation layer of 0 or layer 11 and further providing the crystal relaxation layer 8 with the effect of a barrier relaxation layer, the confinement width of carrier injection is made wider than the width W1 of the upper part of the ridge stripe. We were able to.
In FIG. 7, after the buried structure of FIG. 4 is formed, only the layer 6 and the layer 7 are partially removed as shown in FIG. 7 to selectively leave the crystal relaxation layer 8 acting as a barrier relaxation layer. Keep it. By providing the layer 10 acting as a barrier relaxation layer and the contact layer 9 similarly to the crystal relaxation layer 8,
The constriction width can be set to a width W2 wider than the width W1 of the upper part of the ridge stripe. In FIG. 8, the barrier mitigation layer 11 is first provided on the optical waveguide layer 4, so that the buried structure of FIG. 4 is formed in the same manner as in FIG. The width W2 can be wider than the width W1 above the ridge stripe.
7 and 8, it is possible to increase the constriction width in the waveguide and increase the area for injecting carriers by using the crystal relaxation layer 8 as a current path. Therefore, the resistance of the element can be suppressed, and the voltage in the diode characteristics can be reduced. In the laser element, the voltage at the time of operating current can be reduced. The reduction of the operating voltage is a content that can be dealt with independently of the effect of the reduction of the operating current.

With these techniques, it is possible to reduce the operating current and the operating voltage in the high-power operation of the laser device, thereby achieving low power consumption of the device and a driver for driving the laser device. This can lead to a reduction in power consumption of the device.

In the buried structure of the present invention, a high-output stable operation can be obtained by the above-mentioned characteristic improvement, and an operating current at the time of high output required for the system device is reduced by 20-30%. , A 10-20% improvement was possible. Further, in a drive device for driving a laser element,
With this method, low power consumption of 25% to 30% was achieved.

By using the semiconductor laser device as a light source, it is possible to provide an optical information processing device that satisfies all of the special system practical specifications in an environment where it is actually used.

The optical information processing device and the optical communication system have been specifically exemplified as particularly effective examples of the application of the semiconductor light emitting device according to the present invention. Needless to say, it can be applied to a corresponding use.

[0068]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

The present invention relates to an optical recording light source and a system device constituting an optical pickup system as shown in FIG. 14, and a signal communication light source and a system device for fiber communication constituting a signal transmission amplifier system as shown in FIG. Can be applied to
Provided are a driver device for driving this element with low power consumption and a system device for low power consumption.

<Embodiment 1> One embodiment of the present invention will be described below with reference to FIG.

In this example, from the (100) plane orientation,
An n-type GaAs tilted substrate turned off by 10 degrees in the [011] direction is used. This is because, as a single crystal substrate on which an optical waveguide layer and a light emitting active layer are provided, the substrate plane orientation is set to 0 to 5 from (100) plane.
A substrate having a plane orientation turned off in a range of up to 4.7 degrees (111) plane, and preferably having a plane orientation turned off in a range of 5 degrees to 16 degrees is used. This is because it is preferable to provide a waveguide having a buried structure in the following point of view. That is, the crystal growth using the tilted substrate can improve the quality of the optical waveguide, the light emitting active layer and the buried layer, and reduce the defect density, so that the waveguide layer with the smallest optical loss can be formed and the waveguide can be formed. The lateral asymmetry in the cross-sectional shape is not made extremely small, and the problem of the shape of the laser light used in the system device can be avoided as much as possible.

In FIG. 9, [0]
11], an n-type GaAs relaxation layer 13 (thickness: 0.5 μm, impurity: Si, concentration: 1 × 10 ¹⁸ cm ⁻³ to 2 × 10 ¹⁸ c)
m ^-3 ), n-type AlGaInP optical waveguide layer 14 (thickness: 1.
5 μm to 2.5 μm, impurity: Si, concentration 5 × 10 ¹⁷ c
m ⁻³ -9 × 10 ¹⁷ cm ⁻³ ), compressive strain (or tensile strain) Ga
Three InP quantum well layers (thickness: 3 nm to 15 nm), four tensile strain (or compression strain) AlGaInP quantum barrier layers (thickness: 3 nm to 10 nm), and strain-free AlGaInP on both sides
A strain-compensated multiple quantum well structure active layer 15 composed of an optical isolation confinement layer (thickness: 5 nm to 50 nm), p-type AlGaIn
P optical waveguide layer 16 (thickness: 0.05 μm to 0.3 μm, impurity: Zn or Mg, concentration: 3 × 10 ¹⁷ cm ^{−3 to} 7 × 10
¹⁷ cm ⁻³ ), p-type AlGaInP layer 17 (thickness: 0.0
1 μm to 0.09 μm, impurity: Zn or Mg, concentration 3
× 10 ¹⁷ cm ^{-3 to} 7 × 10 ¹⁷ cm ^-3 ), p-type AlGaI
nP optical waveguide layer 18 (thickness: 0.7 μm to 1.5 μm, impurity: Zn or Mg, concentration: 5 × 10 ¹⁷ cm ^{−3 to} 9 × 10
¹⁷ cm ^-3 ), p-type GaInP barrier relaxation layer 19 (thickness: 1)
0 nm to 50 nm, impurity: Zn or Mg, concentration 1 × 1
0 ¹⁸ cm ^{−3 to} 2 × 10 ¹⁸ cm ⁻³ ) are successively epitaxially grown by metal organic chemical vapor deposition (MOVPE).
A transparent window waveguide that does not absorb laser light is formed in the cavity end face region by ion implantation or impurity diffusion. Next, after an insulating film mask is formed, a layer 19 is formed by photolithography and etching until the layer 17 is reached.
And 18 are removed to form a regular mesa-shaped ridge stripe shown in FIG. Next, the p-type GaInP crystal relaxation layer 2
0 (thickness: 10 nm to 100 nm, impurity: Zn or M
g, concentration 3 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁸ cm ⁻³ , n-type Al
GaAs or AlGaInP transparent current confinement layer 21 (thickness: 0.1 μm to 1.2 μm, impurity: Si, concentration 5 ×
10 ¹⁷ cm ^{−3 to} 2 × 10 ¹⁸ cm ⁻³ ), n-type GaAs current confinement layer 22 (thickness: 0.5 μm to 1.2 μm, impurity:
Si, the concentration of 5 × 10 ¹⁷ cm ⁻³ to 2 × 10 ¹⁸ cm ⁻³ )
Embedded selective growth is performed by OVPE. Here, layer 2
The film thickness of 0 is the same as or larger than that of the layer 19. Further, the layer 21 is formed of a semiconductor layer having a band gap larger than the energy of the laser beam and having a smaller refractive index than the optical waveguide layer 18. As a result, the ridge stripe has a refractive index waveguide structure, and a waveguide structure having a real refractive index waveguide component having a real refractive index difference in the lateral direction of the active layer becomes possible. Further, the buried layer serving as the current confinement layer is partially removed by etching as shown in FIG. 9 to remove the insulating film mask, and then p-type GaAs is formed by MOVPE.
The contact layer 23 is embedded. Finally, the p-side electrode 24 and the n-side electrode 25 are vapor-deposited, and the device is cut out by cleavage scribing to obtain the device cross section shown in FIG.

This device was able to oscillate in the wavelength range of 640 to 690 nm by the design of the quantum well layer of the light emitting active layer, and achieved a maximum light output of 150 to 200 mW. Room temperature threshold current is 30-4
0mA and slope efficiency of 0.9-1.1mW / mA could be obtained. In this device, the threshold current is reduced by 20-30% and the slope efficiency is reduced by 30-40% compared to the conventional device with the embedded absorption layer.
It means that it has been improved. At least 80 at 70 degrees Celsius
High-power stable operation of mW was possible, and operation continued for more than 10,000 hours. With the stripe structure using this method, the optical output characteristics required from the optical recording system can be satisfied even when driven by continuous current or pulse current, and the power consumption of the driver device that drives this element is reduced by 15%.
From 25% to 25%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 2> Another embodiment of the present invention will be described with reference to FIG. An element is manufactured in the same manner as in the first embodiment, but after the crystal is grown up to the layer 15, the layers 18 and 19 are subsequently epitaxially grown by the MOVPE method. At this time, the thickness of the layer 18 is set to a value obtained by adding the thickness of the layer 16 in Embodiment 1. Thereafter, a ridge stripe is formed in the same manner as in the first embodiment, but the layer 18 is etched away until the layer 15 is reached. Next, as in the first embodiment, the layers 20, 21 and 22 which are buried layers are selectively grown using an insulating film mask. In this case, the film thickness of the layer 21 is made larger than that of the first embodiment and is approximately equal to the film thickness obtained by adding the thickness of the layer 16. After that, an element is manufactured in exactly the same manner as in Embodiment 1, and the element cross section of FIG. 11 is obtained.

According to the present embodiment, the same characteristics as those of the first embodiment can be obtained, and further, a lower threshold operation can be realized, and a threshold current of 20 to 30 mA at room temperature is achieved.
In this device, the threshold current is reduced by 30 to 40% as compared with the device having the conventional absorption layer buried structure. High power stable operation of at least 80 mW was possible at a temperature of 70 degrees Celsius, and the operation continued for more than 10,000 hours. With the stripe structure using this method, the optical output characteristics required from the optical recording system can be satisfied even when driven by continuous current or pulsed current, and the power consumption of the driver device that drives this element is reduced by 20%. From 25%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 3> Another embodiment of the present invention will be described with reference to FIG. An element is manufactured in the same manner as in the second embodiment, but a p-type GaInP crystal relaxation layer 26 to which a tensile strain is introduced is provided when the layer 20 is selectively grown. Subsequently, an element is manufactured through the same steps as in Embodiment 2 to obtain the element cross section of FIG.

According to the present example, the same characteristics as those of the second embodiment can be obtained, and further, a lower threshold operation and a higher temperature operation can be realized by improving the carrier confinement in the lateral direction of the active layer. A threshold current of 15 to 25 mA was achieved at room temperature, and the threshold current was reduced by 40 to 50% as compared with the conventional device having the embedded absorption layer structure. In addition, high-power stable operation of at least 80 mW was possible at a temperature of 90 degrees Celsius, and the operation continued for 10,000 hours or more. With the stripe structure using this method, the optical output characteristics required from the optical recording system can be satisfied even when driven by continuous current or pulse current, and the power consumption of the driver device that drives this element is reduced by 25%. Was able to be reduced by 30%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 4> Another embodiment of the present invention will be described below with reference to FIG. In FIG. 9, first, an n-type GaAs substrate 1 having a (100) plane orientation is used.
2, an n-type GaAs relaxation layer 13, an n-type AlGaAs optical waveguide layer 14, three compression-strained AlGaInAs quantum well layers, and Al
A strained multiple quantum well structure active layer 15 comprising four GaAs quantum barrier layers and unstrained AlGaAs optical isolation confinement layers on both sides,
p-type AlGaAs optical waveguide layer 16, p-type GaInP layer 17,
The p-type AlGaAs optical waveguide layer 18 and the p-type GaAs barrier relaxation layer 19 are sequentially epitaxially grown by MOVPE. A transparent window waveguide that does not absorb laser light is formed in the cavity end face region by ion implantation or impurity diffusion. Next, after forming an insulating film mask, the layers 19 and 18 are removed by photolithography and etching until the layer 17 is reached, thereby forming a forward mesa-shaped ridge stripe shown in FIG. Next, the p-type GaAs crystal relaxation layer 20, the n-type AlGaAs or AlGaInP transparent current confinement layer 21, and the n-type GaAs current confinement layer 22 are buried and selectively grown by MOVPE. Here, the thickness of the layer 20 is the same as or larger than that of the layer 19. Further, the layer 21 is formed of a semiconductor layer having a band gap larger than the energy of the laser beam and having a smaller refractive index than the optical waveguide layer 18. As a result, the ridge stripe has a refractive index waveguide structure, and a waveguide structure having a real refractive index waveguide component having a real refractive index difference in the lateral direction of the active layer becomes possible. Further, the buried layer serving as the current confinement layer is partially removed by etching as shown in FIG. 9 to remove the insulating film mask, and then the p-type GaAs contact layer 23 is buried by MOVPE. Finally, the p-side electrode 24 and the n-side electrode 2
5 is vapor-deposited and cleaved and scribed to cut out the device to obtain a cross section of the device shown in FIG. Note that the specific conditions of each of the above semiconductor layers may be set in accordance with Embodiment Mode 1.

This device can oscillate in the wavelength range of 780 to 830 nm by designing the quantum well layer of the light emitting active layer, and has achieved a maximum light output of 200 to 250 mW. Room temperature threshold current is 30-
40mA and slope efficiency of 0.9-1.1mW / mA could be obtained. In this device, the threshold current is reduced by 20-30% and the slope efficiency is reduced by 30-40%, compared to the device with the embedded absorption layer structure.
That is, the percentage has been improved. At least 70 degrees Celsius
High output stable operation of 100mW was possible, and operation continued for more than 10,000 hours. With the stripe structure using this method, the optical output characteristics required from the optical recording system can be satisfied even when driven by continuous current or pulse current, and the power consumption of the driver device that drives this element is reduced by 15%. From 25%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 5> Another embodiment of the present invention will be described with reference to FIG. An element is manufactured in the same manner as in the fourth embodiment, but after the crystal is grown up to the layer 15, the layers 18 and 19 are subsequently epitaxially grown by the MOVPE method. At this time, the thickness of the layer 18 is set to a value obtained by adding the thickness of the layer 16 in Embodiment 4. Thereafter, a ridge stripe is formed in the same manner as in Embodiment 4, but the layer 18 is removed by etching until the layer 15 is reached. Next, as in the fourth embodiment, the layers 20, 21 and 22 which are buried layers are selectively grown using an insulating film mask. In this case, the thickness of the layer 21 is set to be about the thickness obtained by adding the thickness of the layer 16 larger than that of the fourth embodiment. After that, an element is manufactured in exactly the same manner as in Embodiment 4, and the element cross section of FIG. 10 is obtained.

According to the present embodiment, characteristics similar to those of the fourth embodiment can be obtained, and further, a lower threshold operation can be realized, and a threshold current of 20 to 30 mA at room temperature is achieved.
In this device, the threshold current is reduced by 30 to 40% as compared with the device having the conventional absorption layer buried structure. High-power stable operation of at least 100 mW was possible at a temperature of 70 degrees Celsius, and the operation continued for more than 10,000 hours. With the stripe structure using this method, the optical output characteristics required from the optical recording system can be satisfied even when driven by continuous current or pulsed current, and the power consumption of the driver device that drives this element is reduced by 20%. From 25%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 6> Another embodiment of the present invention will be described with reference to FIG. An element is manufactured in the same manner as in the fifth embodiment, but a p-type GaInAsP crystal relaxation layer 26 to which a tensile strain is introduced is provided when the layer 20 is selectively grown.
Subsequently, through the same steps as in Embodiment 5, an element is manufactured, and the element cross section of FIG. 11 is obtained.

According to the present embodiment, the same characteristics as those of the fifth embodiment can be obtained, and further, the lower threshold operation and the higher temperature operation can be realized by improving the carrier confinement in the lateral direction of the active layer. Was. Room temperature threshold current 15-25mA
Is achieved, compared to the conventional absorption layer embedded structure device,
The threshold current was reduced by 40-50%. In addition, the temperature 90 degrees Celsius
High power stable operation of at least 100mW per degree is possible,
The operation continued for more than 10,000 hours. With the stripe structure using this method, the optical output characteristics required from the optical recording system can be satisfied even when driven by continuous current or pulse current, and the power consumption of the driver device that drives this element is reduced by 25%. Was able to be reduced by 30%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 7> Another embodiment of the present invention will be described below with reference to FIG. In FIG. 12, an n-type GaAs substrate 27 having a (100) plane orientation is shown.
On top of this, an n-type GaAs relaxation layer 28, an n-type GaInP optical waveguide layer 29, two compression-strained GaInAs quantum well layers, and a tensile strain G
a strain-compensated multiple quantum well structure active layer 30 including three aInAsP quantum barrier layers and a strain-free GaAs optical isolation / confinement layer;
p-type GaInP optical waveguide layer 31, p-type GaAs layer 32, p-type
GaInP optical waveguide layer 33 and p-type GaInAsP barrier relaxation layer 34 are epitaxially grown sequentially by MOVPE. A transparent window waveguide that does not absorb laser light is formed in the cavity end face region by ion implantation or impurity diffusion. Next, after forming an insulating film mask, the layers 34 and 33 are removed by photolithography and etching until reaching the layer 32, thereby forming an inverted mesa-shaped ridge stripe shown in FIG. Next, p-type GaInAs
P crystal relaxation layer 35, n-type AlGaAs or AlGaIn
The P transparent current confinement layer 36 and the n-type GaAs current confinement layer 37 are buried and selectively grown by MOVPE. Here, the thickness of the layer 35 is the same as or larger than that of the layer 34. Further, the layer 36 is formed of a semiconductor layer having a forbidden band width larger than the energy of the laser beam and having a smaller refractive index than the optical waveguide layer 33. As a result, the ridge stripe has a refractive index waveguide structure, and a waveguide structure having a real refractive index waveguide component having a real refractive index difference in the lateral direction of the active layer becomes possible. Further, the buried layer serving as the current confinement layer is removed by etching halfway as shown in FIG. 12 to remove the insulating film mask, and then the p-type Ga is removed by MOVPE.
The As contact layer 38 is buried. Finally, the p-side electrode 2
4 and the n-side electrode 25 are vapor-deposited and cleaved and scribed to cut out the device to obtain the device cross section shown in FIG.
Note that the specific conditions of each of the above semiconductor layers may be set in accordance with Embodiment Mode 1.

This device can oscillate in the wavelength range of 970 to 990 nm by the design of the quantum well layer of the light emitting active layer, and has achieved a maximum light output of 600 to 700 mW. Room temperature threshold current is 20-
30mA and slope efficiency of 0.9-1.3mW / mA could be obtained. In this device, the threshold current is reduced by 20 to 30% and the slope efficiency is improved by 30 to 40% as compared with the device having the embedded absorption layer. At least 300m at 80 ° C
High output stable operation of W was possible, and operation continued for 100,000 hours or more. Due to the stripe structure using this method, even when driven by continuous current or pulse current,
The optical output characteristics required for the amplifier of the optical communication system can be satisfied, and the power consumption of the driver device for driving the device can be reduced by 15% to 25%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 8> Another embodiment of the present invention will be described with reference to FIG. An element is manufactured in the same manner as in the seventh embodiment, but after the crystal is grown up to the layer 30, the layers 33 and 34 are subsequently epitaxially grown by MOVPE. At this time, the thickness of the layer 33 is set to a value obtained by adding the thickness of the layer 31 in Embodiment 7. Thereafter, a ridge stripe is formed in the same manner as in the seventh embodiment, but the layer 33 is removed by etching until the layer 30 is reached. Next, similarly to the seventh embodiment, the layers 35, 36, and 37, which are buried layers, are selectively grown using an insulating film mask. In this case, the thickness of the layer 36 is set to be approximately the thickness of the layer 31 which is thicker than that of the seventh embodiment and is added to the thickness of the layer 31. After that, an element is manufactured in the same manner as in Embodiment 7, and the element cross section of FIG. 13 is obtained.

According to the present example, characteristics similar to those of the seventh embodiment can be obtained, and further, a lower threshold operation can be realized, and a threshold current of 10 to 20 mA at room temperature has been achieved. In this device, the threshold current is reduced by 30 to 40% as compared with the device having the conventional absorption layer buried structure. High-power stable operation of at least 300 mW at a temperature of 90 degrees Celsius is possible.
The operation continued for more than 10,000 hours. With the stripe structure using this method, the optical output characteristics required for the amplifier of the optical communication system can be satisfied even when driven by continuous current or pulse current, and the power consumption of the driver device that drives this element is reduced. It was possible to reduce from 20% to 25%. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 9> Another embodiment of the present invention will be described with reference to FIG. An element is manufactured in the same manner as in the eighth embodiment, but a p-type GaInAsP crystal relaxation layer in which a tensile strain is introduced is provided when the layer 35 is selectively grown. Subsequently, through a process similar to that of the eighth embodiment, an element is manufactured to obtain an element cross section.

According to the present embodiment, the same characteristics as those of the eighth embodiment can be obtained, and further, the lower threshold operation and the higher temperature operation can be realized by improving the carrier confinement in the lateral direction of the active layer. Was. Room temperature threshold current 5-15mA
Is achieved, compared to the conventional absorption layer embedded structure device,
The threshold current was reduced by 40-50%. In addition, the temperature 10 degrees Celsius
High-power stable operation of at least 300 mW was possible at 0 degrees, and operation continued for 100,000 hours or more. With the stripe structure using this method, the optical output characteristics required for the amplifier of the optical communication system can be satisfied even when driven by continuous current or pulse current, and the power consumption of the driver device that drives this element is reduced. A reduction of 25% to 30% was possible. According to the present content, it is possible to provide a system device equipped with a low-power-consumption driving device equipped with the present element.

<Embodiment 10> The semiconductor laser device described in, for example, Embodiments 1 to 6 of the present invention is mounted on a light source of an optical recording system, and an optical pickup system as shown in FIG. Can be configured.

[Configuration Example of Optical Information Processing Apparatus] A configuration example of the optical information processing system will be described. FIG. 14 is a basic configuration diagram showing an example of the optical disk device. The optical disk device has a disk 39 provided with an optical recording medium for optical recording, an optical pickup, and a control unit for controlling these. The disk is rotated by a motor. Optical pickup is lens system 4
6, 40, rising mirror 41, beam splitter 4
2, a λ / 4 plate 43, a polarization separation diffraction grating 44, a light source 45 such as a semiconductor laser device, and a photodetector 47.

Various reports have been made on general matters of such an optical disk device, but they will be briefly described. Depending on the type of recording material, optical disc devices are roughly classified into read-only type (R
OM type), write-once type, and rewritable type. The reproduction of information in the example of FIG. 14 is performed by optically reading the change in the reflected light from the minute holes (the state change portion of the recording medium) recorded on the disk 39 by the photodetector 47. still,
As the optical recording medium, a usual one can be used.

In the case of the read-only type, the recording information is recorded on the recording medium in advance, and examples of the read-only type recording medium include aluminum and plastic.

When recording, the laser beam is focused on a recording medium on the disk to a fine light spot, and the laser beam is modulated according to the information to be recorded, thereby thermally changing the state of the recording material. Record in rows. This recording is performed while the disk is rotated (moved) by a motor. The light source of the present invention can be used for such a light source.

The semiconductor laser device of the present invention can be used for a laser beam printer. In a laser beam printer (LBP) device, a beam of a semiconductor laser device scans a photosensitive drum using a mirror and a lens system to record information. Then, the information recorded on the photosensitive drum is transferred to photosensitive paper or the like and printed.

The laser element as a light source has an ambient temperature of 7 degrees Celsius.
It can be confirmed that it can operate at a light output of 80-100mW even at 0 to 90 degrees, and to obtain high-speed modulation characteristics for pulse driving at a frequency of 2 GHz or more, and low noise characteristics of -135 dB / Hz or less even at a return light amount of 5%. It was possible to satisfy all system requirements. Further, by improving the characteristics of the semiconductor laser device of the present invention, it is possible to reduce the power consumption of a driver power supply for driving the device, and to reduce power consumption by 25% to 30% compared to driving a conventional device. An optical recording system device having this element mounted on an optical pickup as a light source achieved a rewrite count of 106 times or more and stably continued for a continuous operation of 10,000 hours or more.

<Eleventh Embodiment> An optical communication system can be configured by mounting the semiconductor laser devices according to the seventh to ninth embodiments of the present invention as a light source in a transmission system device system.

[Configuration Example of Optical Communication System] FIG. 15 is a diagram showing an outline of an optical transmission, transmission and reception system. Since the optical input 201 is generally multiplex-transmitted, the demultiplexer 2
02 separates light of a predetermined wavelength. Then, the laser light for amplifying the fiber amplifier 204 from the semiconductor laser device 208 and the input light are mixed by the mixer 203 and input to the fiber amplifier. Semiconductor laser device 2
06 is generally cooled by a cooling device 207, and these components are controlled by an automatic control device 208.

In general, on the transmitting side, each channel is arranged on a frequency axis with a carrier modulated by original information in accordance with an allocation order, and a transmission signal is synthesized by an optical multiplexer.
On the receiving side, on the other hand, the original signal is reproduced by passing the signal separated in frequency by the optical demultiplexer through an optical detection / demodulation circuit provided for each channel. Two-way transmission over one fiber is performed.

It was confirmed that the laser device operates at least with an optical output of 300 mW or more. The optical amplifier device using this element as a light source was able to sufficiently amplify the 1.55 μm laser signal light for transmission by achieving an optical output of 200 mW even at the fiber emission end, and was able to satisfy the required specifications in the system. In this description, the power consumption of the driver power supply for driving the laser device can be reduced, and the power consumption can be reduced by 25% to 30% compared to the conventional device. Also achieved that can be secured.

<Summary> According to the present invention, the present laser element is mounted on a rewritable optical disk drive such as a DVD-RAM system or a magneto-optical recording system, which is an optical recording device, and the number of recording / reproduction is increased by 106. It is possible to operate even if it is performed more than once, and it is possible to stably secure continuous operation for 10,000 hours or more.

Further, a 980 nm band semiconductor laser device to which the present invention is applied is mounted on an optical amplifier of a transmission system device, and an optical output of 200 mW can be obtained at a fiber emission end. It was possible to sufficiently achieve the signal amplification of the laser light. The present contents can also be applied to a light source suitable for a system device for optical communication.

According to the present invention, a semiconductor light emitting device, in particular, a semiconductor laser element has a lamination structure in which the structure of the buried layer of the stripe is improved and the crystal quality is improved, so that the laser element can be operated with a low threshold value and high efficiency. The device operating current at the time of output has been significantly reduced. This is suitable for a light source of a system device that performs optical signal processing. Of course, it goes without saying that the semiconductor laser device according to the present invention can be used for purposes other than those described above.

By using a part of the buried layer as a current injection path, the element resistance was suppressed and the operating voltage was reduced. Regarding the characteristics of this device, the internal optical loss of the waveguide is lower than that of the conventional device without the embedded structure of this method.
Based on the 60-70% reduction, the threshold current is 40-50
% Reduction and 30-40% improvement in efficiency.

In the buried structure of the present invention, a high output stable operation can be obtained by the above-mentioned characteristic improvement, and the operating current at the time of high output of 70 mW or more required for the optical recording system device is reduced by 20-30%
It is possible to reduce. The operating voltage at high output could be improved by at least 10% or more. In a drive device that drives a semiconductor laser device, this method has achieved low power consumption of 25% to 30%.

[0106]

The optical system according to the present invention can provide an optical system having stable transmission characteristics and lower power consumption. Representative forms of the optical system according to the present invention are an optical communication system and an optical information processing device.

The semiconductor light-emitting device of the present invention can provide a semiconductor light-emitting device that achieves high-output stable operation and reduces the operating current during high-output operation.

Further, the semiconductor light emitting device of the present invention can provide a semiconductor laser device which achieves a low threshold and high efficiency operation, reduces an operation current at the time of a high output operation, and reduces an operation voltage.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a ridge stripe waveguide in a manufacturing process of a semiconductor laser device.

FIG. 2 is a cross-sectional view of a structure showing a technique for fabricating a buried structure according to the prior art in a ridge stripe waveguide.

FIG. 3 is a cross-sectional view of a structure showing a technique for fabricating a buried structure according to the prior art in a ridge stripe waveguide.

FIG. 4 is a sectional view of a structure showing a method of applying the buried structure ridge stripe waveguide according to the present invention.

FIG. 5 is a sectional view of a structure showing a technique for applying a buried structure according to another example of the present invention to a ridge stripe waveguide.

FIG. 6 is a cross-sectional view of a structure of a ridge stripe waveguide semiconductor laser device having a buried structure according to the prior art.

FIG. 7 is a structural sectional view showing a ridge stripe waveguide semiconductor laser device having a buried structure according to the present invention.

FIG. 8 is a structural sectional view showing a ridge stripe waveguide semiconductor laser device having a buried structure according to the present invention.

FIG. 9 is a cross-sectional view of a structure showing a ridge stripe waveguide semiconductor laser device showing an example of the present invention.

FIG. 10 is a sectional view of a structure showing a ridge stripe waveguide semiconductor laser device showing another example of the present invention.

FIG. 11 is a sectional view of a structure showing a ridge stripe waveguide semiconductor laser device showing another example of the present invention.

FIG. 12 is a cross-sectional view of a structure showing a ridge stripe waveguide semiconductor laser device showing another example of the present invention.

FIG. 13 is a sectional view of a structure showing a ridge stripe waveguide semiconductor laser device showing another example of the present invention.

FIG. 14 is a system schematic diagram showing an optical pickup system of the present invention.

FIG. 15 is a system schematic diagram showing an optical fiber amplifier system of the present invention.

[Explanation of symbols]

1: semiconductor substrate, 2: optical waveguide layer, 3: light emitting active layer, 4:
Optical waveguide layer, 5: insulating film mask, 6: light absorbing layer, 7: transparent layer, 8: crystal relaxation layer 9: contact layer, 10: barrier relaxation layer, 11: barrier relaxation layer 12: semiconductor substrate (example: n) Tilt angle GaAs), 13: relaxation layer (example: n-type GaAs) 14: optical waveguide layer (example: n-type AlGaAs or AlGaInP) 15: strained multiple quantum well structure active layer (example: AlGaInAs / AlGaA)
s or GaInP / AlGaInP), 16: optical waveguide layer (example: p-type AlGaAs or AlGa)
InP) 17: p-type semiconductor layer (example: p-type GaInP or AlGaInP) 18: optical waveguide layer (example: p-type AlGaAs or AlGaInP) 19: barrier relaxation layer (example: p-type GaAs or GaInP) 20: crystal relaxation thin film Layer (example: p-type GaAs or GaInP) 21: Current confinement layer (example: n-type AlGaAs or AlGaInP) 22: Current confinement layer (example: n-type GaAs), 23: contact layer (example: p-type GaAs) 24: p-side electrode, 25: n-side electrode 26: tensile strained crystal relaxation thin film layer (example: p-type GaInP or GaInA
sP) 27: semiconductor substrate (example: n-type GaAs), 28: relaxation layer (example: n-type GaAs) 29: optical waveguide layer (example: n-type GaInP) 30: strained multiple quantum well structure active layer (example: GaInAs) / GaInAsP
/ GaAs) 31: Optical waveguide layer (example: p-type GaInP), 32: p-type layer (example: GaAs) 33: optical waveguide layer (example: p-type GaInP), 34: barrier relaxation layer (example: p-type GaInAsP) 35: crystal relaxation layer (example: p-type GaInAsP) 36: current confinement layer (example: n-type AlGaAs or AlGaInP) 37: current confinement layer (example: n-type GaAs), 38: contact layer (example: p-type GaAs) 39: optical disk, 40: optical convex lens, 41: rising mirror 42: beam splitter, 43: λ / 4 plate, 44: polarization separation diffraction grating 45: semiconductor laser element, 46: optical convex lens, 47:
Light receiving element 48: laser light path, 49: laser light signal input, 50: duplexer 51: mixer, 52: fiber amplification, 53: mixer, 5
4: Demultiplexer 55: Laser light signal output, 56: Semiconductor laser element 57: Cooling device, 58: Automatic control device.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Momose 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo F-term in Central Research Laboratory, Hitachi, Ltd. 5D119 AA33 AA37 AA42 FA05 FA18 FA20 5F073 AA13 AA45 AA55 AA74 BA05 BA07 CA15 CB02 DA05 DA21 EA15 EA24

Claims (11)

[Claims] 1. An optical system comprising a semiconductor light emitting device having a waveguide structure enabling oscillation in a transverse fundamental mode of a laser above an active layer, wherein the waveguide structure of the semiconductor light emitting device has an oscillation. The lateral basic mode of light is substantially controlled by the real refractive index difference, and at least a crystal relaxation layer is provided between the material layer for providing the real refractive index difference and the active layer. An optical system, characterized in that: 2. The optical system according to claim 1, wherein the crystal relaxation layer has a lattice strain. 3. The optical system according to claim 1, wherein the crystal relaxation layer is formed of a compound semiconductor layer containing substantially no aluminum. 4. The semiconductor device according to claim 1, wherein the crystal relaxation layer has a desired conductivity type, and the crystal relaxation layer forms a part of a carrier injection path of the semiconductor light emitting device.
The optical system according to claim 2 or claim 3. 5. The semiconductor device according to claim 1, wherein said active layer has a quantum well structure.
An optical system according to claim 1. 6. An optical information processing device having a semiconductor light emitting device having a waveguide structure enabling oscillation in a transverse fundamental mode of a laser above an active layer, wherein the waveguide structure of the semiconductor light emitting device is provided. Has a lateral basic mode of oscillation light substantially controlled by a real refractive index difference, and has at least a crystal relaxation layer between a material layer for providing the real refractive index difference and the active layer. An optical information processing apparatus, comprising: 7. The optical information device according to claim 6, wherein the crystal relaxation layer has a lattice strain. 8. The optical information processing apparatus according to claim 6, wherein said crystal relaxation layer is formed of a compound semiconductor layer containing substantially no aluminum. 9. An optical communication system having a semiconductor light emitting device having a waveguide structure enabling oscillation in a transverse fundamental mode of a laser above an active layer, wherein the waveguide structure of the semiconductor light emitting device is The transverse fundamental mode of the oscillating light is controlled substantially by the real refractive index difference, and at least a crystal relaxation layer is provided between the material layer for providing the real refractive index difference and the active layer. An optical communication system, comprising: 10. The optical information device according to claim 9, wherein the crystal relaxation layer has a lattice strain. 11. The optical communication system according to claim 9, wherein said crystal relaxation layer is composed of a compound semiconductor layer containing substantially no aluminum.