JP2003174230A - Semiconductor laser device, semiconductor laser module and optical fiber amplifier using the semiconductor laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device suitable for a light source for a Raman amplifier capable of obtaining a stable and high gain and to provide a semiconductor laser module. <P>SOLUTION: An n-type InP clad layer 2, a GRIN-SCH-MQW active layer 3, a p-type InP spacer layer 4, a p-type InP clad layer 6 and a p-type InGaAsP contact layer 8 are sequentially laminated on an n-type InP substrate 1, and an n-type electrode 11 is disposed on the lower part of the substrate 1. Diffraction gratings 13a, 13b are disposed on the partial region of the layer 4, an insulating film 16 is disposed on the layer 8 corresponding to the grating 13a to prevent the injection current from flowing to the grating 13a. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a first conductivity type semiconductor substrate, a first conductivity type semiconductor buffer layer laminated on the semiconductor substrate, and an active layer laminated on the semiconductor buffer layer. A semiconductor laser device having a first electrode laminated on the active layer and a second electrode arranged on the lower surface of the semiconductor substrate, a semiconductor laser module, and an optical fiber amplifier using these, particularly, The present invention relates to a semiconductor laser device suitable for a pumping light source of an optical fiber amplifier that is stable and capable of obtaining an optical gain, a semiconductor laser module, and an optical fiber amplifier using these.

[0002]

2. Description of the Related Art In recent years, with the widespread use of various multimedia such as the Internet, there has been an increasing demand for a large capacity for optical communication. Conventionally, in optical communication,
1310, which has a wavelength at which light absorption by an optical fiber is small
In the band of nm or 1550 nm, transmission with a single wavelength is common. With this method,
In order to transmit a lot of information, it is necessary to increase the number of cores of the optical fiber laid in the transmission path, and there is a problem that the cost increases as the transmission capacity increases.

Therefore, dense wavelength division multiplexing (DWDM:
Dense-Wavelength Division Multiplexing) communication method has come to be used. This DWDM communication system is a system that mainly uses an EDFA and performs transmission using a plurality of wavelengths in the 1550 nm band, which is the operating band. In this DWDM communication system or WDM communication system, since optical signals of a plurality of different wavelengths are simultaneously transmitted using one optical fiber, it is not necessary to lay new lines, and the transmission capacity of the network is dramatically increased. It is possible to bring an increase.

In this general WDM communication system using the EDFA, it is put to practical use from the 1550 nm band where gain flattening is easy, and recently expanded to the 1580 nm band which has not been used because of its small gain coefficient. There is. However, since the low-loss band of the optical fiber is wider than the band that can be amplified by the EDFA, interest is increasing in the optical fiber amplifier that operates outside the band of the EDFA, that is, the Raman amplifier.

The Raman amplifier has a characteristic that the gain wavelength band is determined by the wavelength of the pumping light, while the optical fiber amplifier using a rare earth ion such as erbium determines the gain wavelength band by the energy level of the ion. Any wavelength band can be amplified by selecting the excitation light wavelength.

In Raman amplification, when strong pumping light is incident on the optical fiber, a gain appears on the long wavelength side of about 100 nm from the pumping light wavelength due to stimulated Raman scattering, and this gain is applied to the optical fiber in this pumped state. When the signal light in the wavelength band that it has is incident, this signal light is amplified. Therefore, in the WDM communication system using the Raman amplifier, the number of channels of signal light can be further increased as compared with the communication system using the EDFA.

FIG. 42 is a block diagram showing the configuration of a conventional Raman amplifier used in a WDM communication system.
In FIG. 42, a Fabry-Perot type semiconductor light emitting device 1
80a to 180d and fiber grading 181a to
The semiconductor laser modules 182a to 182d, each paired with 181d, output the laser light that is the source of the pumping light to the polarization beam combiners 61a and 61b. Although the wavelengths of the laser lights output from the respective semiconductor laser modules 182a and 182b are the same, lights having different polarization planes are combined by the polarization combining coupler 61a. Similarly, the wavelengths of the laser lights output from the semiconductor laser modules 182c and 182d are the same, but lights having different polarization planes are combined by the polarization combining coupler 61b. The polarization combining couplers 61 a and 61 b output the polarization-combined laser lights to the WDM coupler 62. In addition,
The wavelengths of the laser lights output from the polarization combining couplers 61a and 61b are different.

The WDM coupler 62 multiplexes the laser beams output from the polarization combining couplers 61a and 61b via the isolator 60 and outputs the multiplexed laser beams to the amplification fiber 64 via the WDM coupler 65 as pumping light. The signal light to be amplified is input to the amplification fiber 64 to which the pumping light is input from the signal light input fiber 69 via the isolator 63, and is multiplexed with the pumping light and Raman-amplified.

The signal light Raman-amplified in the amplification fiber 64 (amplified signal light) is transmitted through a WDM coupler 65 and an isolator 66 to a monitor light distribution coupler 67.
Entered in. The monitor light distribution coupler 67 outputs a part of the amplified signal light to the control circuit 68, and outputs the remaining amplified signal light to the signal light output fiber 70 as output laser light.

The control circuit 68 controls the light emitting state of each of the semiconductor light emitting elements 180a to 180d, for example, the light intensity, based on a part of the input amplified signal light, so that the Raman amplification gain band has a flat characteristic. Feedback control.

FIG. 43 is a diagram showing a schematic structure of a semiconductor laser module using fiber grading.
In FIG. 43, this semiconductor laser module has a semiconductor light emitting element 202 and an optical fiber 203. The semiconductor light emitting device 202 has an active layer 221. Active layer 2
21, the light reflecting surface 222 is provided at one end and the light emitting surface 223 is provided at the other end. The light generated in the active layer 221 is reflected by the light reflecting surface 222 and output from the light emitting surface 223.

An optical fiber 203 is arranged on the light emitting surface 223 of the semiconductor light emitting device 202 and is optically coupled to the light emitting surface 223. The core 232 in the optical fiber 203 has a fiber grading 2 at a predetermined position from the light emitting surface 223.
33 is formed, and the fiber grading 233 selectively reflects light having a characteristic wavelength. That is, the fiber grading 233 functions as an external resonator, forms a resonator between the fiber grading 233 and the light reflecting surface 222, and a laser light of a specific wavelength selected by the fiber grading 233 is amplified to output laser. It is output as light 241.

Similarly, FIG. 44 is a block diagram showing a schematic structure of a conventional Raman amplifier. In FIG. 44, the Raman amplifier includes an optical multiplexer 120 provided on the transmission path 99, optical isolators 111 to 113, and a high output pumping light source (HPU: High-power Pumping Unit) 130.

FIG. 45 is a diagram showing a configuration example of the above-mentioned HPU 130. In FIG. 45, the HPU 130 includes six laser units LD1 to LD having different oscillation center wavelengths.
6 and a Mach-Zehnder type WDM coupler 131. Further, the laser units LD1 to LD6 are
Two Fabry-Perot type semiconductor laser modules 134 having the same oscillation center wavelength are provided, and the laser output of each semiconductor laser module 134 is wavelength-stabilized by the fiber Bragg grating 133 (FBG) and combined by the polarization combiner (PBC) 132. Waved as one output.

The polarization combination by the PBC 132 is a measure for increasing the output power of each oscillation center wavelength and reducing the polarization dependence of the Raman gain.
Specifically, by using polarization combination, TE mode laser light and TM mode laser light having the same wavelength can be combined without interference, and light loss can be reduced.

As described above, since the HPU 130 needs to perform amplification over the multiplexed signal lights of a plurality of wavelengths (channels), it is composed of a plurality of laser units having different oscillation center wavelengths. Each laser unit L
The laser outputs output from D1 to LD6 are further multiplexed by the WDM coupler 131 and output as high-power multiplexed pumping light. The pumping light output from the HPU 130 passes through the optical multiplexer 120 and the optical fiber that is the transmission path 99. Note that FIG. 44 shows an example of backward pumping, and the pumping light multiplexed by the optical multiplexer 120 passes through the transmission path 99 in the opposite direction to the signal light.

Since high-power pumping light passes through the transmission path 99, Raman scattering is performed in a wavelength range shifted by 110 nm to the longer wavelength side than the pumping light based on the material characteristics of the optical fiber as the transmission medium. Light is generated, and the energy of the excitation light transits to the signal light through the stimulated Raman scattering process. As a result, the signal light is amplified.

As described above, the Raman amplifier is an amplifier capable of amplifying the signal light as it is by using the already laid optical fiber as an amplification medium. It differs from the EDFA in the amplification medium, the number of pumping light sources used, the pumping power, and the like. The light source for exciting the erbium-doped fiber in the EDFA may have the same structure as the HPU 130 described above.

[0019]

[Patent Document 1] Japanese Patent Laid-Open No. 8-97517

[0020]

However, the above-mentioned semiconductor laser modules (182a to 182d) have the following problems.
Fiber grading 233 and semiconductor light emitting device 202
Since the distance between the fiber grading 233 and the light reflecting surface 222 is long, the relative intensity noise (R
IN: Relative Intensity Noise) increases. In Raman amplification, the process of amplification occurs quickly, so if the pumping light intensity fluctuates, the Raman gain also fluctuates, and this fluctuation of Raman gain is output as it is as fluctuation of the amplified signal strength, There was a problem that stable Raman amplification could not be performed.

Further, in the above-mentioned semiconductor laser module, it is necessary to optically couple the optical fiber 203 having the fiber grading 233 and the semiconductor light emitting element 202, and it takes time and labor to align the optical axis at the time of assembly. , Because it is a mechanical optical coupling in the resonator,
There is a problem in that the oscillation characteristics of the laser may change due to mechanical vibration and the like, and stable excitation light may not be provided in some cases.

As the Raman amplifier, in addition to the backward pumping method for pumping the signal light from the rear as in the Raman amplifier shown in FIG. 42, the forward pumping method for pumping the signal light from the front and both There is a bidirectional excitation method that excites from the direction. At present, the backward pumping method is widely used as the Raman amplifier. The reason is that the forward pumping method in which the weak signal light travels in the same direction as the strong pumping light has a problem that the pumping light intensity fluctuates.
Therefore, the emergence of a stable pumping light source applicable to the forward pumping method is desired. That is, when the conventional semiconductor laser module using the fiber grading is used, there is a problem that applicable pumping methods are limited.

Further, Raman amplification in the Raman amplifier is conditioned on that the polarization direction of the signal light and the polarization direction of the pumping light match. That is, in Raman amplification, there is a polarization dependency of the amplification gain, and it is necessary to reduce the influence of the deviation between the polarization direction of the signal light and the polarization direction of the pump light. Here, in the case of the backward pumping method, there is no problem because the polarization of the signal light becomes random during propagation, but in the case of the forward pumping method, the polarization dependence is strong and the orthogonal polarization combining of the pumping light is performed. , It is necessary to reduce the polarization dependence by devolatization. That is, the degree of polarization (DOP: Degree Of Po)
larization) needs to be small.

Further, since Raman amplification has a relatively low amplification factor, the emergence of a high-output pumping light source for Raman amplification has been desired.

The present invention has been made in view of the above,
An object of the present invention is to provide a semiconductor laser device and a semiconductor laser module suitable for a Raman amplifier light source that is stable and can obtain a high gain.

[0026]

In order to achieve the above object, a semiconductor laser device according to a first aspect of the present invention is a semiconductor laser device of a first conductivity type, and a semiconductor buffer of a first conductivity type stacked on the semiconductor substrate. A semiconductor laser device having a layer, an active layer laminated on the semiconductor buffer layer, a first electrode laminated on the active layer, and a second electrode arranged on the lower surface of the semiconductor substrate, A second conductive type spacer layer laminated on the active layer and a laser beam having a plurality of oscillation longitudinal modes arranged in a partial region of the second conductive type spacer layer and having a specific center wavelength. It is characterized by comprising a diffraction grating to be selected and a non-current injection region where an injection current does not flow into a part of the diffraction grating.

According to the first aspect of the present invention, by providing the non-current injection region in which the injection current does not flow into a part of the diffraction grating, even if the diffraction grating has a single period, the non-current injection Different from the center wavelength selected by the diffraction grating in the injection region and the center wavelength selected by the diffraction grating in the region into which the current is injected, the same function as providing a plurality of diffraction gratings can be achieved.

According to a second aspect of the present invention, there is provided a semiconductor laser device further comprising an insulating film arranged on a partial region of an upper portion of the diffraction grating in the above invention, and the existence of the insulating film causes the diffraction grating of the diffraction grating to exist. It is characterized by preventing the injection current from flowing into a part.

According to the second aspect of the invention, by disposing the insulating film, it is possible to effectively prevent the injection current from flowing into the non-current injection region.

A semiconductor laser device according to a third aspect of the present invention is a semiconductor substrate of a first conductivity type, a first conductivity type semiconductor buffer layer laminated on the semiconductor substrate, and a semiconductor buffer layer laminated on the semiconductor buffer layer. An active layer, a first electrode laminated on the active layer, and a second electrode disposed on the lower surface of the semiconductor substrate.
And a second conductive type spacer layer laminated on the active layer, and a plurality of plurality of electrodes each having a specific center wavelength are arranged in a partial region of the second conductive type spacer layer. And a diffraction grating for selecting a laser beam having an oscillation longitudinal mode, the first electrode being disposed in a region corresponding to a part of the diffraction grating, and the diffraction grating. A second portion arranged in a region corresponding to a portion in which the first portion does not exist, and the first portion and the second portion are spatially or electrically separated from each other. And

According to the invention of claim 3, the first electrode is spatially separated into the first portion and the second portion, whereby the optical output of the oscillated laser light is controlled. ,
The central wavelength selection can be controlled independently by passing a current through a part of the diffraction grating.

Further, in the semiconductor laser device according to a fourth aspect of the present invention, in the above invention, the first electrode further has a third portion arranged in a region corresponding to another portion of the diffraction grating. , The third portion is spatially separated from the first portion and the second portion.

According to the invention of claim 4, by further providing the third portion for the first electrode, the refractive index of the diffraction grating can be controlled more efficiently, and the desired wavelength can be obtained. Therefore, the yield of the semiconductor laser device can be improved.

According to a fifth aspect of the present invention, in the semiconductor laser device according to the above invention, the first conductivity type clad layer is laminated between the first conductivity type semiconductor buffer layer and the active layer, and It further comprises a second conductivity type spacer layer and a second conductivity type clad layer laminated between the first electrode and the first electrode.

According to the fifth aspect of the present invention, the active layer is sandwiched from the upper and lower sides by the clad layer, so that a double hetero structure is formed and carriers are concentrated in the active layer, so that the semiconductor laser oscillates with high efficiency. The device can be realized.

Further, a semiconductor laser module according to claim 6 is the semiconductor laser device according to any one of claims 1 to 5, a temperature control module for controlling the temperature of the semiconductor laser device, and the semiconductor laser device. An optical fiber for guiding the laser light emitted from the device to the outside, and an optical coupling lens system for optically coupling the semiconductor laser device and the optical fiber are provided.

According to the invention of claim 6, by using the above semiconductor laser device, there is no need to perform fiber grading, there is no need to perform optical axis alignment, etc., and assembly is easy, and oscillation characteristics are generated by mechanical vibration or the like. It is possible to realize a semiconductor laser module that does not change.

The semiconductor laser module according to claim 7 further comprises a photodetector for measuring the optical output of the semiconductor laser device, and an isolator for suppressing the incidence of reflected return light from the optical fiber side. Is characterized by.

According to the invention of claim 7, the light output can be monitored by providing the photodetector, and the light output can be stabilized. The provision of the isolator prevents the reflected light from the outside. Can be prevented.

An optical fiber amplifier according to claim 8 is a semiconductor laser device according to any one of claims 1 to 5, or an excitation light source using the semiconductor laser module according to claim 6 or 7. , And a coupler for combining the signal light and the pumping light, and an amplification optical fiber.

According to the invention of claim 8, an optical fiber amplifier having a high amplification factor and capable of performing stable amplification can be realized by including the semiconductor laser device or the semiconductor laser module. .

The optical fiber amplifier according to claim 9 is characterized in that the amplification optical fiber amplifies light by Raman amplification.

According to the ninth aspect of the present invention, the Raman amplification can be used to more suitably perform the optical amplification.

According to a tenth aspect of the present invention, in the semiconductor laser device, the active layer formed between the first reflection film provided on the emission end face of the laser light and the second reflection film provided on the reflection end face of the laser light. In a semiconductor laser device having a diffraction grating partially provided in the vicinity of, and outputting laser light having a desired oscillation longitudinal mode by at least the wavelength selection characteristic of the diffraction grating, the diffraction grating has the first reflection It is characterized in that it is provided in the vicinity of the film and is formed so as to be separated from the first reflective film by 50 μm or less.

According to the tenth aspect of the present invention, the diffraction grating is provided in the vicinity of the first reflection film and is formed so as to be separated from the first reflection film by 50 μm or less, and by this separation, the first reflection film is formed. The wavelength instability caused by the change in the refractive index of the diffraction grating due to the temperature rise of the end face of the
By not separating over, the kink caused by the oscillation longitudinal mode hop is eliminated, and stable longitudinal multimode oscillation is realized.

According to an eleventh aspect of the semiconductor laser device, the separation distance between the diffraction grating and the first reflective film is
It is characterized in that it is in the range of 10 to 20 μm.

According to the invention of claim 11, the separation distance between the diffraction grating and the first reflection film is 10 to 20 μm.
To achieve high wavelength stability and stable vertical multimode operation.

According to a twelfth aspect of the present invention, the semiconductor laser device is characterized in that the desired number of oscillation longitudinal modes is two or more within the half-width of the oscillation wavelength spectrum.

According to the twelfth aspect of the present invention, due to the wavelength selection characteristic of the diffraction grating, the number of the desired oscillation longitudinal modes is set to be two or more within the half-width of the oscillation wavelength spectrum, and a high output is obtained. The laser light is output.

According to a thirteenth aspect of the present invention, in the above-mentioned invention, the semiconductor laser device is characterized in that the diffraction grating has a diffraction grating length of 300 μm or less.

According to the thirteenth aspect of the invention, the diffraction grating length of the diffraction grating provided on the first reflection film side is 300
μm or less.

According to a fourteenth aspect of the present invention, in the above-mentioned invention, the semiconductor laser device is characterized in that the diffraction grating length of the diffraction grating is not more than (300/1300) times the resonator length. .

According to the fourteenth aspect of the present invention, the diffraction grating length of the diffraction grating provided on the first reflection film side is set to a value that is (300/1300) times the resonator length or less.

According to a fifteenth aspect of the present invention, in the above-mentioned invention, the semiconductor laser device is characterized in that the diffraction grating has a multiplication value of the coupling coefficient of the diffraction grating and the diffraction grating length of 0.3 or less. To do.

According to the fifteenth aspect of the present invention, in the diffraction grating, the multiplication value of the coupling coefficient of the diffraction grating and the diffraction grating length is 0.3 or less, and the linearity of the drive current-optical output characteristic is good. To increase the stability of the light output.

According to a sixteenth aspect of the present invention, in the above-mentioned invention, the semiconductor laser device is characterized in that the diffraction grating changes the grating period randomly or at a predetermined period.

According to the sixteenth aspect of the present invention, the grating period of the diffraction grating is changed randomly or at a predetermined period to cause fluctuation in wavelength selection of the diffraction grating.
The half-width of the oscillation wavelength spectrum is widened.

According to a seventeenth aspect of the present invention, in the semiconductor laser device according to the above invention, the first reflection film and the second reflection film are provided.
The resonator formed by the active layer formed between the reflective film and the reflective film has a length of 800 μm or more.

According to the invention of claim 17, the first
The resonator formed by the active layer formed between the reflective film and the second reflective film has a length of 800 μm or more,
It enables high output operation.

A semiconductor laser module according to an eighteenth aspect is the semiconductor laser device according to any one of the first to eighth aspects, and a light for externally guiding the laser light emitted from the semiconductor laser device. A fiber and an optical coupling lens system for optically coupling the semiconductor laser device and the optical fiber are provided.

According to the eighteenth aspect of the invention, since the resonator of the semiconductor laser device is not physically separated by using the semiconductor laser device which does not use the fiber grating, it is not necessary to perform optical axis alignment or the like. Assembling the semiconductor laser module is easy, and the oscillation characteristics of the laser are less likely to change due to mechanical vibration, etc., and stable laser light can be output reliably and stably, and further cost reduction can be realized. be able to.

According to a nineteenth aspect of the present invention, in the semiconductor laser module according to the above-mentioned invention, the temperature control device for controlling the temperature of the semiconductor laser device and the optical coupling lens system are provided to reflect from the optical fiber side. An isolator that suppresses incidence of return light is further provided.

According to the nineteenth aspect of the invention, since the semiconductor laser device which does not use the fiber grating is used, the polarization dependent isolator can be used unlike the in-line type fiber type, and the insertion loss is small. Further, it is possible to realize a semiconductor laser module having a small RIN.

An optical fiber amplifier according to claim 20 is the semiconductor laser device according to any one of claims 10 to 17 or the semiconductor laser module according to claim 18 or 19 for wideband Raman amplification. It is characterized by being used as an excitation light source.

According to the invention of claim 20, claim 1
The semiconductor laser device according to any one of 0 to 17 or the semiconductor laser module according to claim 18 or 19 is used as an excitation light source for wideband Raman amplification, and the semiconductor laser device or semiconductor laser module described above is I am trying to have an effect.

An optical fiber amplifier according to a twenty-first aspect is the semiconductor laser device according to any one of the tenth to seventeenth aspects, or the semiconductor laser module according to the eighteenth or nineteenth aspect is for wideband Raman amplification. And is used as a forward pumping light source or a forward pumping light source in a bidirectional pumping method.

According to the invention of claim 21, claim 1
The semiconductor laser device according to any one of 0 to 17 or the semiconductor laser module according to claim 18 or 19 is used as a pumping light source for wideband Raman amplification in a forward pumping light source or a bidirectional pumping system. It is used as a forward excitation light source so as to achieve the effects of the above-mentioned semiconductor laser devices or semiconductor laser modules.

According to a twenty-second aspect of the present invention, there is provided a semiconductor laser device in which a compressive strain quantum well active layer, a tensile strain quantum well active layer, a laser light emitting end face and a laser light emitting end face, and the compressive strain quantum well active layer are provided. A well active layer and / or a diffraction grating formed in the vicinity of the tensile strained quantum well active layer,
A laser beam in which a TE mode laser beam generated in the compressive strained quantum well active layer and a TM mode laser beam generated in the tensile strained quantum well active layer are polarization-combined. It is characterized in that a plurality of oscillation longitudinal mode laser lights having a predetermined output value or less are output according to the wavelength selection characteristic of the diffraction grating.

According to the twenty-second aspect of the invention, it is possible to output the TE mode laser light generated in the compressive strain quantum well active layer and the TM mode laser light generated in the tensile strain quantum well active layer. .

According to a twenty-third aspect of the present invention, in the semiconductor laser device according to the above-mentioned invention, the compressive strain quantum well active layer and the tensile strain quantum well active layer are vertically stacked, and the compressive strain quantum well active layer is formed. A tunnel junction layer is formed between one of the cladding layers sandwiching the layer and one of the cladding layers sandwiching the tensile strain quantum well active layer.

According to the twenty-third aspect of the present invention, a reverse bias current is applied to either one of the compression strain quantum well active layer and the tensile strain quantum well active layer stacked in the vertical direction via the tunnel junction layer. be able to.

A semiconductor laser device according to a twenty-fourth aspect of the present invention is characterized in that, in the above-mentioned invention, the compressive strain quantum well active layer and the tensile strain quantum well active layer are stacked vertically adjacent to each other. To do.

According to the twenty-fourth aspect of the present invention, the compressive strained quantum well active layer and the tensile strained quantum well active layer constitute one active layer, and the active layer is sandwiched by a pair of clad layers to realize laser oscillation. can do.

According to a twenty-fifth aspect of the invention, in the semiconductor laser device according to the above-mentioned invention, the compressive strain quantum well active layer and the tensile strain quantum well active layer are butt-joined in the laser beam emitting direction. And

According to the twenty-fifth aspect of the invention, the laser light generated in one of the compressive strain quantum well active layer and the tensile strain quantum well active layer is converted into the laser light generated in the other active layer. At the same time, the light can be emitted to the outside through the other active layer.

According to a twenty-sixth aspect of the present invention, in the semiconductor laser device according to the above invention, at least one electrode of an electrode pair for applying a current to the compressive strain quantum well active layer and the tensile strain quantum well active layer. At least one electrode of the electrode pair for applying a current to, is electrically separated by a separation groove formed on the coupling boundary between the compressive strain quantum well active layer and the tensile strain quantum well active layer. It is characterized by being

According to the twenty-sixth aspect of the present invention, the electrodes electrically isolated by the isolation groove are formed in the compressive strain quantum well active layer and the tensile strain quantum well active layer which are butt-coupled on the same semiconductor substrate. With the provision of, the laser light generated in both active layers can be controlled by different applied currents or applied voltages.

A semiconductor laser module according to a twenty-seventh aspect of the present invention is a semiconductor laser device according to any one of the twenty-second to twenty-sixth aspects, and a light for guiding the laser light emitted from the semiconductor laser device to the outside. A fiber, and an optical coupling lens system for optically coupling the semiconductor laser device and the optical fiber are provided.

According to the invention of claim 27, claim 2
The semiconductor laser device described in any one of 2 to 26 can be provided in a package housing, and a low DOP module can be realized.

An optical fiber amplifier according to a twenty-eighth aspect of the invention is provided with a pumping light source for outputting pumping light obtained by multiplexing a plurality of laser lights having different oscillation center wavelengths, and a signal light propagating on the transmission line. In an optical fiber amplifier that performs amplification with a desired amplification band and a desired gain determined by the pumping light, the pumping light source comprises:
7. The semiconductor laser module described in 7 is provided.

According to the invention of claim 28, claim 2
The semiconductor laser module described in 7 can be used as an excitation light source for an EDFA or a Raman amplifier.

[0082]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a semiconductor laser device, a semiconductor laser module and an optical fiber amplifier according to the present invention will be described below with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and width of layers, the ratio of the thickness of each layer, and the like are different from actual ones. Further, it is needless to say that the drawings include parts in which dimensional relationships and ratios are different from each other.

(First Embodiment) First, a semiconductor laser device according to the first embodiment of the present invention will be described.
1 is a side sectional view of the semiconductor laser device according to the first embodiment, and FIG. 2 is a sectional view taken along line AA of the semiconductor laser device shown in FIG.

In the semiconductor laser device according to the first embodiment, as shown in FIG. 1, (100) of the n-InP substrate 1 is used.
N-InP clad layer 2, GRIN-SCH-
MQW (Graded Index-Separate Confinement Heteros)
tructure Multi Quantum Well: Active layer 3, p-InP spacer layer 4, p-InP clad layer 6, p-InGaAsP contact layer 8, and p-side electrode 10 are sequentially stacked. . An n-side electrode 11 is arranged below the n-InP substrate 1.

The n-InP clad layer 2 has a function as a buffer layer and a function as a clad layer. n-InP cladding layer 2 and p-In
Since the GRIN-SCH-MQW active layer 3 is sandwiched by the P clad layer 6, the semiconductor laser device according to the first embodiment has a double hetero structure, and effectively confines the carriers to have a high luminous efficiency.

As shown in FIG. 2, the upper part of the n-InP clad layer 2, the GRIN-SCH-MQW active layer 3, the p-InP spacer layer 4, and the lower part of the p-InP clad layer 6 are irradiated with laser light. The structure is narrower than the n-InP substrate 1 in the direction perpendicular to the emission direction.
Then, the upper part of the n-InP clad layer 2 and GRIN
-SCH-MQW active layer 3, p-InP spacer layer 4,
And contacting the bottom of the p-InP cladding layer 6 to form p-I
nP blocking layer 9b, n-InP blocking layer 9
a is arranged in order. The p-InP blocking layer 9b and the n-InP blocking layer 9a are for blocking the current so that the injected current does not leak, and by adopting such a structure (BH structure), the GRI is formed.
The structure is such that the density of the current flowing through the N-SCH-MQW active layer 3 is increased and the luminous efficiency is improved. Also, B
The H structure enables horizontal single transverse mode operation and stable operation of the laser.

Further, in the semiconductor laser device according to the first embodiment, the low reflection film 15 is disposed over the entire surface of the emitting side end face (right side face in FIG. 1), and the reflecting side end face (left side face in FIG. 1). In, the high reflection film 14 is arranged over the entire surface.

The high reflection film 14 has a light reflectance of 80% or more, preferably 98% or more. On the other hand, the low reflection film 15 is for preventing reflection of the laser light on the end face on the emission side. Therefore, the low reflection film 15 has a film structure having a low reflectance, and has a light reflectance of 2% or less, preferably 1% or less.

Furthermore, inside the p-InP spacer layer 4 and in the vicinity of the end face on the emission side, the diffraction gratings 13a and 13a are formed.
b is arranged. The diffraction gratings 13a and 13b have a structure in which rectangular parallelepiped gratings are arranged in series along the laser light emission direction. The diffraction gratings 13a and 13b have a film thickness of 20 nm.
And has a length of Lg = 50 μm in the laser beam emitting direction. Further, since the period is about 220 nm and has a periodic structure, laser light having a plurality of oscillation longitudinal modes with a center wavelength of 1480 nm is selected.

The gratings forming the diffraction gratings 13a and 13b are made of p-InGaAsP, and in the first embodiment, the diffraction gratings 13a and 13b are formed by arraying the gratings having the same period. . The end of the diffraction grating 13a on the low reflection film 15 side is preferably in contact with the low reflection film 15, but may be separated from the low reflection film 15 as long as the distance is within 100 μm.

Above the diffraction grating 13a, p-In
An insulating film 16 is arranged between the GaAsP contact layer 8 and the p-side electrode 10. The insulating film 16 is the p-side electrode 1
This is for preventing the current injected from 0 from flowing near the low reflection film 15 including the diffraction grating 13a. In addition,
The insulating film 16 is formed by depositing an insulating material such as AlN, Al ₂ O ₃ , MgO, and TiO ₂ .

Next, the operation of the semiconductor laser device according to this embodiment will be described. The current injected from the p-side electrode 10 causes radiative recombination of carriers in the GRIN-SCH-MQW active layer 3, and the emitted light has a specific wavelength component selected by the diffraction gratings 13a and 13b, and is emitted from the emission-side end face. To be done. The diffraction grating 13a
Does not receive a current due to the insulating film 16, while the diffraction grating 13b receives a current. Therefore, p-InGaA forming the diffraction gratings 13a and 13b is formed.
The refractive indexes of sP have different values, and the characteristics of the present embodiment resulting from this will be described later. First, in order to facilitate understanding, features of providing a single-period diffraction grating will be described below.

The semiconductor laser device according to the first embodiment is premised on being used as a pumping light source for a Raman amplifier, and its oscillation wavelength λ ₀ is 1100 nm to 15 nm.
50 nm and the cavity length L is 800 μm or more and 320
It is set to 0 μm or less. By the way, in general, the mode interval Δλ of the longitudinal mode generated by the resonator of the semiconductor laser device can be expressed by the following equation when the effective refractive index is “n”. That is, Δλ = λ ₀ ² / (2 · n · L). Here, when the oscillation wavelength λ ₀ is 1480 μm and the effective refractive index is 3.5, when the resonator length L is 800 μm, the mode interval Δλ of the longitudinal mode is about 0.39 nm, and the resonator length is 3200 μm. At this time, the mode interval Δλ of the longitudinal mode is about 0.1 nm. That is, the longer the resonator length L, the longer the mode interval Δλ of the longitudinal mode.
Becomes narrower, and the selection condition for oscillating a single longitudinal mode laser beam becomes stricter.

On the other hand, in the first embodiment, the diffraction gratings 13a and 13b select the longitudinal mode according to the Bragg wavelength. One of the diffraction gratings 13a and 13b
The selected wavelength characteristic according to the above is represented as an oscillation wavelength spectrum 20 shown in FIG.

As shown in FIG. 3, in the first embodiment,
A plurality of oscillation longitudinal modes are allowed to exist within the wavelength selection characteristic represented by the half-width Δλh of the oscillation wavelength spectrum 20 by the semiconductor laser device having the diffraction grating. In a conventional DFB (Distributed Feedback) semiconductor laser device or a DBR (Distributed Bragg Reflector) semiconductor laser device, it is difficult to oscillate in a single longitudinal mode when the resonator length L is set to 800 μm or more. The semiconductor laser device used was not used.
However, in the semiconductor laser device according to the first embodiment, the resonator length L is positively set to 800 μm or more so that the laser output is performed by including a plurality of oscillation longitudinal modes within the half-width Δλh of the oscillation wavelength spectrum. I have to. In FIG. 3, the half-width Δλh of the oscillation wavelength spectrum 20
It has three oscillation longitudinal modes 21 to 23 therein.

When the laser light having a plurality of oscillation longitudinal modes is used, the peak value of the laser output can be suppressed and a high laser output value can be obtained as compared with the case where the laser light of the single longitudinal mode is used. . For example, the semiconductor laser device shown in the first embodiment has the profile shown in FIG. 4B and can obtain a high laser output with a low peak value. On the other hand, FIG. 4A shows a profile of a semiconductor laser device of single longitudinal mode oscillation when obtaining the same laser output, and has a high peak value.

Here, when the semiconductor laser device is used as a pumping light source for a Raman amplifier, it is preferable to increase the pumping light output power in order to increase the Raman gain, but if the peak value is high, stimulated Brillouin scattering occurs. However, there is a problem that noise is increased. The occurrence of stimulated Brillouin scattering has a threshold value Pth at which stimulated Brillouin scattering occurs, and when the same laser output power is obtained, as shown in FIG.
As shown in (b), by providing a plurality of oscillation longitudinal modes and suppressing their peak values, it is possible to obtain high pumping light output power within the threshold Pth of stimulated Brillouin scattering, and as a result, high Raman Gain can be obtained.

The wavelength interval (mode interval) Δλ of the oscillation longitudinal modes 21 to 23 is set to 0.1 nm or more. This is because when the semiconductor laser device is used as a pumping light source for a Raman amplifier, if the mode interval Δλ is 0.1 nm or less, stimulated Brillouin scattering is likely to occur. As a result, it is preferable that the above-described resonator length L is 3200 μm or less according to the above-described equation of the mode interval Δλ.

From this point of view, it is desirable that the number of oscillation longitudinal modes included in the half-width Δλh of the oscillation wavelength spectrum 20 is plural. By the way, in Raman amplification, since the amplification gain has polarization dependence, it is necessary to reduce the influence of the deviation between the polarization direction of the signal light and the polarization direction of the pump light. As a method for this, there is a method of depolarizing the pumping light. Specifically, in addition to the method of using the output light from two semiconductor laser devices, a polarization maintaining fiber of a predetermined length is used as a depolarizer. Use 1
There is a method of propagating laser light emitted from the semiconductor laser device of the table to the polarization maintaining fiber. When the latter method is used as the depolarization method, the coherency of the laser light decreases as the number of oscillation longitudinal modes increases, so the length of the polarization-maintaining fiber required for depolarization should be reduced. Can be shortened. In particular, when the number of oscillation longitudinal modes is 4 or 5, the required length of the polarization maintaining fiber is drastically shortened. Therefore, when depolarizing the laser light emitted from the semiconductor laser device for use in the Raman amplifier, the emitted light from the two semiconductor laser devices need not be polarization-combined and used. Since it becomes easy to depolarize the emitted laser light of the semiconductor laser device and use it, it is possible to reduce the number of parts used in the Raman amplifier and promote miniaturization.

Here, if the oscillation wavelength spectrum width is too wide, the multiplexing loss due to the wavelength synthesizing coupler becomes large, and noise or gain fluctuation is caused by the movement of the wavelength within the oscillation wavelength spectrum width. Therefore, the full width at half maximum Δλh of the oscillation wavelength spectrum 20 is 3 nm.
Hereafter, it is necessary to set it to preferably 2 nm or less.

Further, in the conventional semiconductor laser device, as shown in FIG. 43, since the semiconductor laser module uses the fiber grading, the resonance between the fiber grading 233 and the light reflecting surface 222 causes the relative intensity noise ( RIN) becomes large and stable Raman amplification cannot be performed. However, in the semiconductor laser device shown in the first embodiment, the fiber grading 2
Since the laser light emitted from the low-reflection film 15 is used as it is as a light source for pumping the Raman amplifier without using 33, the relative intensity noise is reduced, and as a result, the fluctuation of the Raman gain is reduced and a stable Raman gain is obtained. Amplification can be performed.

Further, in the semiconductor laser device according to the first embodiment, the diffraction grating 13a is not affected by the injection current due to the existence of the insulating film 16, whereas the diffraction grating 13b is directly affected by the injection current. There is a difference. The effect of this on the semiconductor laser device according to the first embodiment will be described below.

In general, p-I constituting the diffraction grating 13b
Regarding the region of the nGaAsP and p-InP spacer layer 4 excluding the portion forming the diffraction grating 13a,
The refractive index changes due to the injection of current. Therefore, since the diffraction gratings 13a and 13b originally have the same physical structure but different refractive indexes, the optical path lengths thereof are different from each other. Therefore, two different center wavelengths are selected.
There will be two diffraction gratings. Hereinafter, for simplicity, it is assumed that the diffraction grating 13a has a period Λ ₁ and the diffraction grating 13b has a period Λ ₂ (≠ Λ ₁ ). It should be noted that these periods refer to effective values in consideration of the refractive index.

FIG. 5 schematically shows a spectrum of laser light emitted from the semiconductor laser device according to the first embodiment when the center wavelength λ ₁ and the center wavelength λ ₂ are selected.

In FIG. 5, the diffraction grating with the period Λ ₁ forms an oscillation wavelength spectrum of wavelength λ ₁ and selects three oscillation longitudinal modes within this oscillation wavelength spectrum. On the other hand, the diffraction grating with the period Λ ₂ forms an oscillation wavelength spectrum of the wavelength λ ₂ , and forms three oscillation longitudinal modes in this oscillation wavelength spectrum. Further, in FIG. 5, the oscillation longitudinal mode on the short wavelength side of the central wavelength λ ₁ and the oscillation longitudinal mode on the long wavelength side of the central wavelength λ ₂ overlap each other.

Therefore, the composite oscillation wavelength spectrum 24 formed by the diffraction grating having the periods Λ ₁ and Λ ₂ includes 4 to 5 oscillation longitudinal modes in the composite oscillation wavelength spectrum 24. As a result, compared with the case of forming a plurality of oscillation longitudinal modes based on a single center wavelength, a larger number of oscillation longitudinal modes can be easily selected and output, and the optical output can be increased.

As described above, although the diffraction gratings 13a and 13b are diffraction gratings having a single period, due to the existence of the insulating film 16, diffraction gratings having different periods and selecting different center wavelengths are used. It has the same function as two. In the graph of FIG. 5, the wavelength difference between λ ₁ and λ ₂ is about 0.2 nm, and in order to realize such a wavelength difference, it is necessary to set the period difference of the diffraction grating to 0.028 nm.

However, in the semiconductor laser device according to the first embodiment, it is not necessary to provide a plurality of diffraction gratings having such a period difference, and the insulating film 16 is arranged above a part of the diffraction grating having a single period. It is sufficient if the structure is made. This facilitates manufacturing and can provide a semiconductor laser device with high yield.

Further, the diffraction grating 13b and the diffraction grating 13
Since the refractive index of the p-InP spacer layer 4 around b increases in proportion to the intensity of the current, the central wavelength λ ₁ selected by the diffraction grating 13a and the central wavelength λ ₂ selected by the diffraction grating 13b. Can be controlled by the magnitude of the injected current. Therefore, by controlling the injection current value, laser oscillation can be performed with a wavelength difference different from the center wavelength difference assumed at the design stage.

Further, the GRIN-SCH-MQW active layer 3
In the low reflection film 15 arranged on the end face of the
(Catastrophic Optical Damage) may occur. In the vicinity of the low reflection film 15, the COD is increased in the temperature of the end face → reduced the band gap of the active layer → light absorption →
This is a phenomenon in which a feedback cycle occurs in which current is concentrated on the end face → temperature of the end face rises again, and the positive face of this cycle causes the end face to melt and instantly deteriorate. By the way, in the semiconductor laser device according to the first embodiment, since the region where the injection current does not flow exists near the end face due to the existence of the insulating film 16, it is expected that heat generation is suppressed and the probability of COD occurrence is reduced.

(Second Embodiment) Next, a semiconductor laser device according to a second embodiment will be described. FIG. 6 is a side sectional view showing the structure of the semiconductor laser device according to the second embodiment. The semiconductor laser device according to the second embodiment is similar to the semiconductor laser device according to the first embodiment in that
On the (100) plane of the n-InP substrate 1, the n-InP clad layer 2, GRIN-SCH-MQW active layer 3, p-I.
nP spacer layer 4, p-InP clad layer 6, p-In
The GaAsP contact layer 8 is sequentially stacked. An n-side electrode 11 is arranged below the n-InP substrate 1. Furthermore, the laser beam emission side (right side in FIG. 6)
The low reflection film 15 is arranged on the end face, and the high reflection film 14 is provided on the reflection side (left side in FIG. 6) end face. The high reflection film 14 has a light reflectance of 80% or more, and the low reflection film 15 has a light reflectance of It is the same as in the first embodiment that the content is set to 2% or less. Further, inside the p-InP spacer layer 4,
Diffraction gratings 13a and 13b having the same structure with respect to the period and the like are arranged near the low reflection film 15.

The structure of the cross section perpendicular to the laser emission direction is similar to that of the semiconductor laser device according to the first embodiment.

An insulating film 31b is arranged on the p-InGaAsP contact layer 8 in a region corresponding to the upper part of the diffraction grating 13a. Also, p-
Diffraction grating 1 on the InGaAsP contact layer 8
The p-side electrode 30b is arranged in a region corresponding to 3b,
The current I _b flows through the side electrode 30 _b . Further, the p-side electrode 30a is arranged on the other region of the p-InGaAsP contact layer 8, and the current _Ia flows in through the p-side electrode 30a. here,
The p-side electrode 30a and the p-side electrode 30b are insulated from each other by the insulating film 31a. The p-side electrodes 30a, 30
b are connected to respective independent current sources, and the current I _a injected from the p-side electrode 30a and the current I _b injected from 30b are different from each other.

In the semiconductor laser device according to the second embodiment, the electrode on the p-InGaAsP contact layer 8 is divided into the p-side electrode 30a and the p-side electrode 30b, and the following advantages are brought about.

First, it is possible to independently control the selective center wavelength of the diffraction grating 13b and the oscillation output of the semiconductor laser device. In the semiconductor laser device according to the second embodiment, the diffraction grating 13b is controlled by controlling _Ib.
Around each diffraction grating and the diffraction grating 13b forming the
The refractive index of the P spacer layer 4 can be changed. Therefore, the central wavelength selected by the diffraction grating 13b is controlled. On the other hand, the oscillation output of the semiconductor laser device is I _a
Can be changed by controlling. And p
Since the side electrodes 30a, 30b are electrically insulated by the insulating film 31a, it is possible to control without depending on each other the values of I _a and I _b. Therefore, the semiconductor laser device according to the first embodiment can independently control the selective center wavelength and the oscillation output.

Further, by stabilizing the I _b flowing into the diffraction grating 13b, a stable oscillation wavelength can be easily obtained. As a result, when the semiconductor laser device according to the second embodiment is used as a pumping light source for a Raman amplifier, output control of pumping light becomes easy. Especially 300
In a high power semiconductor laser device of about mW, particularly when the value of the injection current becomes large, a slight fluctuation easily occurs in the optical output characteristic of the monitor current, but as shown in FIG.
Even in the vicinity of the optical output of 00 mW, a fine fluctuation does not occur in the monitor current, and the output control of the excitation light becomes simple and easy.

(Third Embodiment) Next, a third embodiment will be described with reference to FIG. FIG. 8 shows the third embodiment.
FIG. 3 is a side cross-sectional view showing the structure of the semiconductor laser device according to the present invention. Regarding the basic structure of the semiconductor laser device according to the third embodiment, description of the same or similar portions as those in FIGS. 1 and 6 will be omitted.

In the semiconductor laser device according to the third embodiment, the p-side electrode 32c is arranged on the p-InGaAsP contact layer 8 in a region corresponding to the upper part of the diffraction grating 13a. Similarly, a p-side electrode 32b is arranged in a region on the p-InGaAsP contact layer 8 and above the diffraction grating 13b, and a current p-side electrode 32b,
The p-side electrode 32a is arranged in the other region where the 32c does not exist. Further, the p-side electrodes 32a and 32b are electrically insulated from each other by the insulating film 33a, and
2b and 32c are insulated by the insulating film 33b.
Further, p-side electrodes 32a, 32b, 32c are respectively connected to a separate independent current source, respectively I _a, I _b, the current I _c is assumed to flow.

The semiconductor laser device according to the third embodiment has the following advantages by disposing three electrodes on the p-InGaAsP contact layer 8. First, the diffraction grating 1
Since currents can be independently injected into the electrodes 3a and 13b through the electrodes, it is possible to change the refractive index of each of the diffraction gratings 13a and 13b and the surrounding regions. Due to the change in the refractive index, the optical path lengths of the diffraction gratings 13a and 13b change, and the effective period and period length also change. Therefore, the diffraction gratings 13a and 13b
Are different from each other in the center wavelength to be selected as compared with the case where no current is injected. Since the value of the selected central wavelength changes according to the density of the injected current, the p-side electrode 32c,
The central wavelength selected by the diffraction gratings 13a and 13b can be controlled by controlling the magnitude of the current injected from 32b.

Furthermore, since the currents I _c and I _b flowing into the diffraction gratings 13a and 13b can be controlled independently,
The center wavelength selected by the diffraction grating 13a and the diffraction grating 13b
The center wavelength selected in can be different.

Further, since the currents I _c and I _b flowing into the diffraction gratings 13a and 13b and the current I _a flowing into a portion where the diffraction grating does not exist are independent of each other, the semiconductor laser according to the third embodiment The control of the optical output of the device and the control of the selected central wavelength can be performed independently. As a result, as described with reference to FIG. 7 in the second embodiment, it is possible to output laser light with stable output even when a large current is injected.

Furthermore, since the value of the central wavelength selected by the diffraction gratings 13a and 13b can be controlled, the yield of the semiconductor laser device can be improved. That is,
Even if the center wavelength assumed at the design stage cannot be selected, a desired center wavelength can be selected by applying a current through the p-side electrodes 32b and 32c. Therefore, according to the third embodiment, it is possible to use even a light source that could not be used as the excitation light source due to the shift of the center wavelength in the related art, by controlling the selected center wavelength.

The semiconductor laser device according to the first to third embodiments is not limited to the above structure.
For example, in the semiconductor laser device according to the first embodiment, the n-InP clad layer 2 has both the function as a clad layer and the function as a buffer layer. The n-InP buffer layer may be separately arranged.

Also, the p-InGaAsP contact layer 8
As for the insulating film disposed above, for example, the insulating film 16 may be made of an n-type semiconductor other than an insulating material such as AlN. Generally, the p-InGaAsP contact layer 8 is p
This is because the insulating film 6 is made of an n-type semiconductor because it is made of a type semiconductor, so that a current hardly flows vertically downward due to the pn junction. In addition, a non-injection structure having a multi-layer structure made of an npn semiconductor or an insulating film made of an intrinsic semiconductor may be used. Although the contact layer located under the groove between the p-side electrodes and the structure in which a part of the p-InP clad layer is removed are complicated steps in manufacturing, in order to realize electrical insulation, This is a more suitable structure.

Further, the semiconductor laser device is capable of wavelength selection by the diffraction grating without the double hetero structure. Therefore, it is possible to have a so-called homojunction laser or single hetero laser structure in which there is no difference in bandwidth between the active layer and the other layers. For the same reason, the active layer may have any structure other than the GRIN-SCH-MQW structure as long as it is capable of radiative recombination. Similarly, in the first embodiment, GRIN-SCH-M
Although the p-InP blocking layer 9b and the n-InP blocking layer 9a are arranged to increase the density of carriers flowing into the QW active layer 3, the wavelength can be selected even if these structures are omitted. .

Furthermore, it is possible to reverse the conductivity type in the above example. That is, GRIN-SCH-M
The layer below the QW active layer 3 is a p-type, and GRIN-SC
The layer above the H-MQW active layer 3 may be n-type.
In that case, the conductivity types of the diffraction gratings 13a and 13b are set to n.
Need to be mold.

Regarding the diffraction gratings 13a and 13b,
In the above example, the structure having the same period and the like has been described, but this is introduced as a simple example for facilitating the description, and the diffraction gratings 13a and 13b are provided in a state where no current flows. Of course, the structures may be different from each other. Also, the diffraction grating 1
Also inside 3a and 13b, not only a diffraction grating having a single period but also a chirped grain structure or a structure in which gratings having different periods are mixed may be used.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, the semiconductor laser device shown in the first to third embodiments described above is modularized.

FIG. 9 is a vertical sectional view showing the structure of the semiconductor laser module according to the fourth embodiment of the present invention. The semiconductor laser module according to the fourth embodiment has a semiconductor laser device 51 corresponding to the semiconductor laser device described in the first to third embodiments. The semiconductor laser device 51 has a junction-down structure in which the p-side electrode is joined to the heat sink 57a. As a housing of the semiconductor laser module, a Peltier element 58 as a temperature control device is arranged on the inner bottom surface of a package 59 formed of ceramic or the like. A base 57 is arranged on the Peltier element 58.
A heat sink 57a is arranged above. An electric current (not shown) is applied to the Peltier element 58, and cooling and heating are performed depending on its polarity. However, the Peltier element 58 mainly functions as a cooler in order to prevent the oscillation wavelength shift due to the temperature rise of the semiconductor laser device 51. That is, the Peltier element 58 is
When the laser light has a longer wavelength than the desired wavelength, it is cooled and controlled to a low temperature, and when the laser light has a shorter wavelength than the desired wavelength, it is heated to a higher temperature. To control. This temperature control is specifically performed by the heat sink 5
7a and is controlled based on the detection value of the thermistor 58a arranged in the vicinity of the semiconductor laser device 51, and a control device (not shown) normally controls the Peltier element so that the temperature of the heat sink 57a is kept constant. Control 58. In addition, the control device (not shown) increases the drive current of the semiconductor laser device 51 as the heat sink 57a increases.
The Peltier element 58 is controlled so that the temperature of the Peltier element decreases. By performing such temperature control, the output stability of the semiconductor laser device 51 can be improved, which is also effective in improving the yield. The heat sink 57a is
For example, it is desirable to use a material having a high thermal conductivity such as diamond. This is the heat sink 5
This is because when 7a is formed of diamond, heat generation when a high current is applied is suppressed.

The semiconductor laser device 51 is provided on the base 57.
And the heat sink 57 in which the thermistor 58a is arranged.
a, the first lens 52, and the current monitor 56 are arranged. The laser light emitted from the semiconductor laser device 51 is
The light is guided onto the optical fiber 55 via the first lens 52, the isolator 53, and the second lens 54. The second lens 54 is on the optical axis of the laser light and has a package 59.
It is optically coupled to an optical fiber 55 which is provided above and is externally connected. The current monitor 56 is used for the semiconductor laser device 5.
The light leaked from the reflection film side of No. 1 is detected by the monitor.

Here, in this semiconductor laser module, the semiconductor laser device 51 and the optical fiber 55 are arranged so that the return light reflected by other optical parts does not return to the inside of the resonator.
An isolator 53 is interposed between the and. Unlike the conventional semiconductor laser module using fiber grading, the isolator 53 is not an in-line type fiber type, but a polarization dependent type isolator that can be built in the semiconductor laser module can be used. Losses can be reduced, lower relative intensity noise (RIN) can be achieved, and the number of parts can be reduced.

In the fourth embodiment, the first to third embodiments are provided.
Since the semiconductor laser device shown in 1 is modularized, a polarization-dependent isolator can be used, insertion loss can be reduced, noise reduction and reduction in the number of components can be promoted.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described. In the fifth embodiment, the semiconductor laser module shown in the above-described fourth embodiment is applied to a Raman amplifier.

FIG. 10 is a block diagram showing the structure of a Raman amplifier according to the fifth embodiment of the present invention. This Raman amplifier is used in a WDM communication system. Figure 10
In this Raman amplifier, the Raman amplifier according to the fourth embodiment
The semiconductor laser modules 60a to 60d having the same structure as that of the semiconductor laser module shown in FIG. 42 are used, and the semiconductor laser modules 182a to 182d shown in FIG. 42 are replaced with the above-mentioned semiconductor laser modules 60a to 60d.

Each semiconductor laser module 60a, 60b
Outputs a laser beam having a plurality of oscillation longitudinal modes to the polarization beam combiner 61a via the polarization maintaining fiber 71, and each of the semiconductor laser modules 60c and 60d outputs a plurality of laser beams via the polarization maintaining fiber 71. The laser light having the oscillation longitudinal mode is output to the polarization beam combiner 61b. Here, the laser lights oscillated by the semiconductor laser modules 60a and 60b have the same wavelength. The laser light emitted by the semiconductor laser modules 60c and 60d has the same wavelength, but is different from the wavelength of the laser light emitted by the semiconductor laser modules 60a and 60b. This is because the Raman amplification has polarization dependence, and the polarization combining coupler 61
A laser beam whose polarization dependence is eliminated by a and 61b is output.

The laser lights having different wavelengths output from the respective polarization combining couplers 61a and 61b are combined by the WDM coupler 62, and the combined laser lights are WDM.
The excitation light for Raman amplification is output to the amplification fiber 64 via the coupler 65. The signal light to be amplified is input to the amplification fiber 64 to which the pumping light is input,
Raman amplified.

The signal light Raman-amplified in the amplification fiber 64 (amplified signal light) is transmitted through the WDM coupler 65 and the isolator 66 to the monitor light distribution coupler 67.
Entered in. The monitor light distribution coupler 67 outputs a part of the amplified signal light to the control circuit 68, and outputs the remaining amplified signal light to the signal light output fiber 70 as output laser light.

The control circuit 68 controls each of the semiconductor laser modules 60a-60d based on a part of the amplified signal light input.
Is controlled by feedback control so that the gain band of Raman amplification has a flat characteristic.

In the Raman amplifier shown in the fifth embodiment, for example, the semiconductor laser module 182a in which the semiconductor light emitting device 180a shown in FIG. 42 and the fiber grading 181a are coupled by the polarization maintaining fiber 71a.
However, since the semiconductor laser module 60a incorporating the semiconductor laser device shown in the first to third embodiments is used instead of the above, the use of the polarization maintaining fiber 71a can be reduced. As described above, since each of the semiconductor laser modules 60a to 60d has a plurality of oscillation longitudinal modes, the polarization maintaining fiber length can be shortened. As a result, it is possible to reduce the size and weight of the Raman amplifier and reduce the cost.

In the Raman amplifier shown in FIG. 10,
Although polarization polarization couplers 61a and 61b are used,
, The semiconductor laser modules 60a and 60c are directly connected to the WD through the polarization maintaining fiber 71, respectively.
The light may be output to the M coupler 62. In this case, the polarization planes of the semiconductor laser modules 60a and 60c are incident on the polarization-maintaining fiber 71 at 45 degrees. This makes it possible to eliminate the polarization dependence of the optical output output from the polarization maintaining fiber 71,
It is possible to realize a more compact Raman amplifier with a smaller number of components.

In addition, the semiconductor laser modules 60a-6
If a semiconductor laser device having a large number of oscillation longitudinal modes is used as the semiconductor laser device built in 0d, the required length of the polarization maintaining fiber 71 can be shortened. In particular, when the number of oscillation longitudinal modes becomes 4 or 5, the required length of the polarization-maintaining fiber 71 is drastically shortened, so that simplification and downsizing of the Raman amplifier can be promoted. Furthermore, as the number of oscillation longitudinal modes increases, the coherence length becomes shorter, and the degree of polarization (DOP: De
gree of polarization) can be reduced, and the polarization dependence can be eliminated, which also facilitates simplification and miniaturization of the Raman amplifier.

Further, in this Raman amplifier, the optical axis alignment is easier than in a semiconductor laser module using fiber grading, and there is no mechanical optical coupling in the resonator. The stability and reliability of can be improved.

Furthermore, since the semiconductor laser devices of the first to third embodiments described above have a plurality of oscillation modes, it is possible to generate high-power pumping light without causing stimulated Brillouin scattering. Therefore, stable and high Raman gain can be obtained.

Although the Raman amplifier shown in FIGS. 10 and 11 is of the backward pumping type, it is of the forward pumping type because the semiconductor laser modules 60a-60d output stable pumping light as described above. Also, stable Raman amplification can be performed even with the bidirectional pumping method.

The Raman amplifier shown in FIG. 10 or 11 can be applied to the WDM communication system as described above. FIG. 12 is a block diagram showing a schematic configuration of a WDM communication system to which the Raman amplifier shown in FIG. 10 or 11 is applied.

In FIG. 12, a plurality of transmitters Tx1 to Tx are provided.
The optical signals of wavelengths λ _{1 to} λ _n sent from xn are combined by the optical combiner 80 and integrated into one optical fiber 85. On the transmission path of the optical fiber 85, a plurality of Raman amplifiers 81 and 83 corresponding to the Raman amplifier shown in FIG. 10 or FIG. 11 are arranged according to the distance to amplify the attenuated optical signal. The signal transmitted on the optical fiber 85 is demultiplexed by the optical demultiplexer 84 into optical signals having a plurality of wavelengths λ _{1 to} λ _n , and received by the plurality of receivers Rx1 to Rxn. In addition, an ADM (Add / Drop Multi) that adds and takes out an optical signal of an arbitrary wavelength on the optical fiber 85.
plexer) may be inserted.

In the fifth embodiment described above, the semiconductor laser device shown in the first to third embodiments or the semiconductor laser module shown in the fourth embodiment is used as a pumping light source for Raman amplification. However, not limited to this, it is obvious that it can be used as a light source for EDFA excitation such as 980 nm and 1480 nm.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described. FIG. 13 is a cutaway view of a semiconductor laser device according to a sixth embodiment of the present invention when viewed obliquely. FIG. 14 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device shown in FIG. FIG. 15 is a sectional view taken along the line AA of the semiconductor laser device shown in FIG. FIG.
In FIG. 15, this semiconductor laser device 1020 is
On the (100) plane of the n-InP substrate 1001, n
N-InP clad layer 1002 which also serves as a buffer layer and a lower clad layer made of InP, and GRI having compressive strain
N-SCH-MQW (Graded Index-Separate Confinem
ent Heterostructure Multi Quantum Well) Active layer 10
03, a p-InP spacer layer 1004, a p-InP clad layer 1006, and a p-InGaAsP contact layer 1007 are laminated.

The p-InP spacer layer 1004 has a film thickness of 20 nm, Ls = 15 μm from the reflection side end face, and the length Lg = 50 μm separated toward the reflection film 1014 side.
The diffraction grating 1013 of
Are periodically formed with a pitch of about 220 nm and select the wavelength of laser light having a center wavelength of 1.48 μm. P-InP spacer layer 1004 including this diffraction grating 1013, GRI
N-SCH-MQW active layer 1003, and n-InP
The upper portion of the buffer layer 1002 is processed into a mesa stripe shape, and the p-InP blocking layer 1008 and the n-InP blocking layer 1009 formed as current blocking layers are buried on both sides in the longitudinal direction of the mesa stripe. . A p-side electrode 1010 is formed on the upper surface of the p-InGaAsP contact layer 1007.

A reflecting film 1014 having a high light reflectance of 80% or more, preferably 98% or more is formed on the light reflecting end surface which is one end surface in the longitudinal direction of the semiconductor laser device 1020, and the other end surface of the light 2% reflectance on the exit end,
An emission side reflection film 1015 having a low light reflectance of 1%, 0.5% or less, and most preferably 0.1% or less is formed. Reflection film 1014, diffraction grating 1013, emission side reflection film 101
The light generated in the GRIN-SCH-MQW active layer 1003 of the optical resonator formed by the spacer layer 1004 on the emitting side end face side having 5 is reflected by the reflecting film 1014, and passes through the emitting side reflecting film 1015. It is emitted as laser light, and at this time, the wavelength is selected by the diffraction grating 1013 and emitted.

The semiconductor laser device 1020 in the sixth embodiment is premised on being used as a pumping light source for a Raman amplifier, and its oscillation wavelength λ ₀ is 1100n.
m to 1550 nm, and the resonator length L is set to 800 μm or more and 3200 μm or less. By the way, in general, the mode interval Δλ of the longitudinal mode generated by the resonator of the semiconductor laser device can be expressed by the following equation when the effective refractive index is “n”. That is, Δλ = λ ₀ ² / (2 · n · L). Here, when the oscillation wavelength λ ₀ is 1480 μm and the effective refractive index is 3.5, when the resonator length L is 800 μm, the mode interval Δλ of the longitudinal mode is about 0.39 nm, and the resonator length is 3200 μm. At this time, the mode interval Δλ of the longitudinal mode is about 0.1 nm. That is, the longer the resonator length L, the longer the mode interval Δλ of the longitudinal mode.
Becomes narrower, and the selection condition for oscillating a single longitudinal mode laser beam becomes stricter.

On the other hand, the diffraction grating 1013 selects the longitudinal mode according to its Bragg wavelength. This diffraction grating 101
The selected wavelength characteristic according to No. 3 is represented as an oscillation wavelength spectrum 1030 shown in FIG.

As shown in FIG. 16, in the sixth embodiment, semiconductor laser device 102 having diffraction grating 1013 is provided.
A plurality of oscillation longitudinal modes are allowed to exist in the wavelength selection characteristic indicated by the half-width Δλh of the oscillation wavelength spectrum 1030 of 0. Conventional DBR (Distributed Brag
g Reflrector) Semiconductor laser device or DFB (Dist
ributed feedback) In the semiconductor laser device, the cavity length L
Is 800 μm or more, it is difficult to oscillate in a single longitudinal mode, so that the semiconductor laser device having such a cavity length L is not used. However, in the semiconductor laser device 1020 of the sixth embodiment, by positively setting the cavity length L to 800 μm or more, a plurality of oscillation longitudinal modes are included in the half-width Δλh of the oscillation wavelength spectrum, and laser output is performed. I am trying. In FIG. 16, three oscillation longitudinal modes 1 are set in the half width Δλh of the oscillation wavelength spectrum.
031 to 1033 are included.

When the laser light having a plurality of oscillation longitudinal modes is used, the peak value of the laser output can be suppressed and a high laser output value can be obtained as compared with the case where the laser light of the single longitudinal mode is used. . For example, the semiconductor laser device shown in the sixth embodiment has the profile shown in FIG. 17B and can obtain a high laser output with a low peak value. On the other hand, FIG. 17A shows a profile of a semiconductor laser device of single longitudinal mode oscillation when obtaining the same laser output, which has a high peak value.

Here, when the semiconductor laser device is used as a pumping light source for a Raman amplifier, it is preferable to increase the pumping light output power in order to increase the Raman gain, but if the peak value is high, stimulated Brillouin scattering will occur. However, there is a problem that noise is increased. The occurrence of stimulated Brillouin scattering has a threshold value Pth at which stimulated Brillouin scattering occurs, and if the same laser output power is obtained, then FIG.
As shown in FIG. 7 (b), a plurality of oscillation longitudinal modes are provided,
By suppressing the peak value, a high pump light output power can be obtained within the threshold value Pth of stimulated Brillouin scattering, and as a result, a high Raman gain can be obtained.

The wavelength interval (mode interval) Δλ of the oscillation longitudinal modes 1031 to 1033 is 0.1 nm or more. This is because when the semiconductor laser device 1020 is used as a pumping light source for a Raman amplifier, stimulated Brillouin scattering is likely to occur when the mode interval Δλ is 0.1 nm or less. As a result, the above-mentioned resonator length L is 32 by the above-mentioned equation of the mode interval Δλ.
It is preferable that the thickness is 00 μm or less.

From this point of view, it is desirable that the number of oscillation longitudinal modes included in the half-width Δλh of the oscillation wavelength spectrum 1030 is plural. By the way, in Raman amplification, since the amplification gain has polarization dependence, it is necessary to reduce the influence of the deviation between the polarization direction of the signal light and the polarization direction of the pump light. As a method for this purpose, there is a method of depolarizing the excitation light.
In addition to a method of polarization-combining the output light from the semiconductor laser devices 1020 using a polarization combining coupler, a polarization-maintaining fiber having a predetermined length is used as a depolarizer and emitted from one semiconductor laser device 1020. There is a method of propagating laser light through this polarization maintaining fiber. When the latter method is used as the depolarizing method, the coherency of the laser light decreases as the number of oscillation longitudinal modes increases, so the length of the polarization maintaining fiber required for depolarizing is shortened. can do. In particular, when the number of oscillation longitudinal modes is 4 or 5, the required length of the polarization maintaining fiber is drastically shortened. Therefore, when the laser light emitted from the semiconductor laser device 1020 is depolarized for use in the Raman amplifier, the emitted light of the two semiconductor laser devices is not combined by polarization and used. Since it becomes easy to depolarize the laser light emitted from the semiconductor laser device 1020 and use it, it is possible to reduce the number of components used in the Raman amplifier and promote miniaturization.

Here, if the oscillation wavelength spectrum width is too wide, the multiplexing loss due to the wavelength synthesizing coupler becomes large, and noise or gain fluctuation is caused by the movement of the wavelength within the oscillation wavelength spectrum width. Therefore, the half-width Δλh of the oscillation wavelength spectrum 1030 is 3
It is necessary to set the thickness to nm or less, preferably 2 nm or less.

Further, in the conventional semiconductor laser device, as shown in FIG. 43, since the semiconductor laser module uses the fiber grating, the resonance between the fiber grating 233 and the light reflecting surface 222 causes the relative intensity noise ( RIN) becomes large, and stable Raman amplification cannot be performed. However, in the semiconductor laser device 1020 shown in the sixth embodiment, the laser light emitted from the emission side reflection film 1015 is directly used without using the fiber grating 233. Since it is used as a pumping light source for a Raman amplifier, relative intensity noise is reduced, and as a result, fluctuations in Raman gain are reduced, and stable Raman amplification can be performed.

Further, the semiconductor laser module shown in FIG. 43 requires mechanical coupling in the resonator,
There are cases where the oscillation characteristics of the laser change due to vibrations, but in the semiconductor laser device of the sixth embodiment,
A stable optical output can be obtained without changing the oscillation characteristics of the laser due to mechanical vibration or the like.

In FIG. 18, κi = 20 cm ⁻¹ , Lg
It is a figure which shows IL (optical output Po with respect to drive current Iop) characteristic at the time of = 30micrometer. This IL characteristic shows that a large kink does not occur from several tens of mA to about 1500 mA, and the driving current Iop is about 40 mA at around 1200 mA.
It enables high output of 0 mW and high efficiency operation.

Here, the separation distance Ls from the exit side end face of the diffraction grating 13 in the sixth embodiment will be considered. The diffraction grating 1013 has a coupling coefficient κi = 26.5 cm.
^-1 , diffraction grating length Lg = 50 μm, resonator length L = 1300
When the distance Ls from the end face on the output side is 0 μm,
Three types, 0 μm and 100 μm, were examined. FIG. 19 is a diagram showing the wavelength dependence of the oscillation threshold gain difference. In FIG. 19, the bandwidth of the oscillation threshold gain difference tends to become narrower as the separation distance Ls becomes longer from the emitting end facet. This is because the end face on the exit side and the diffraction grating 1013
This is considered to be because the resonator is formed between and and between the diffraction grating 1013 and the reflection-side end surface to form a composite resonator.

Further, in order to realize stable longitudinal multimode oscillation, assuming that a plurality of longitudinal modes exist with an oscillation threshold gain difference of 0.5 cm -1 or less, the diffraction grating 1
When 013 is in contact with the emitting end face (Ls = 0 μm), the number of modes is 13, and Ls = 50 μm, 1
At 00 μm, the number of modes is 6. Particularly, when Ls = 100 μm, 1 near 1484 nm
Two longitudinal modes appear at a position 3 nm away from 481 nm. This is considered to be due to the above-mentioned composite resonator. As a result, when Ls = 100 μm, there is a high possibility that a kink due to the longitudinal mode hop will occur at a high driving current. Therefore, it is desirable to arrange the diffraction grating 1013 on the emitting end face without any gap.

FIG. 20 is a diagram showing the wavelength dependence of the front-to-rear end face ratio of the optical output with the arrangement position of the diffraction grating 1013 as a parameter. In FIG. 20, the front-to-rear end face ratio of the optical output in the oscillation mode is about 350 regardless of the position of the diffraction grating 1013. However, the bandwidth becomes narrower as the position of the diffraction grating 1013 is separated from the end face on the emission side, and stable vertical multimode oscillation operation becomes difficult. Therefore, from the results shown in FIGS. 19 and 20, the separation distance L from the exit side end face of the diffraction grating 1013 is L.
s is preferably 50 μm or less, and more preferably 0 μm.

On the other hand, the temperature on the emission side end face is high at the time of laser oscillation, and if the diffraction grating 1013 is arranged without being separated from the emission side end face, the refractive index of the diffraction grating 1013 changes due to heat generation, resulting in a high wavelength. It becomes impossible to secure stability. Therefore, considering the consideration results of FIGS. 19 and 20, the separation distance Ls is 10 to 20 μm.
The optimum value is about m, and as a result, stable longitudinal multimode operation and wavelength stability can be secured. Therefore, the separation distance Ls shown in FIGS. 13 to 15 is 15 μm.
And

By the way, each semiconductor laser device is collectively formed on a semiconductor wafer. FIG. 21 is a plan view of a semiconductor wafer on which the semiconductor laser devices are collectively formed. 22 is a partial cross-sectional view of the semiconductor wafer. Figure 2
1, a semiconductor laser device group LD formed of semiconductor laser devices LD1 and LD2 and the like is formed on a semiconductor laser device group LD formed on a semiconductor wafer W so as to face each other. Therefore, even if the position of the cleaved surface C12 between the laser bars LB1 and LB2 is displaced, when the margin of the cleaved surface actually cleaved is ± 5 μm, the diffraction grating 1013 is separated from the emitting side end surface. Separation distance Ls
= 10 to 20 μm. Further, even if the reflection-side end surface is displaced, the original function is not lost.

The length Lg of the diffraction grating 1013 is 50.
Since it is as short as μm, the electron beam drawing time required for forming the diffraction grating can be extremely shortened.

In the sixth embodiment, the diffraction grating 1013
By setting the separation distance Ls from the emission side end face to 50 μm or less, particularly 10 to 20 μm, the influence of the change in the refractive index of the diffraction grating due to the temperature rise of the end face near the emission side end face is eliminated and high wavelength stability is secured. While being able to
Since formation of the composite resonator and generation of kinks associated therewith are reduced, stable longitudinal multimode operation can be performed.

Further, the semiconductor laser device 20 selects the wavelength by the diffraction grating 1013 and sets the oscillation wavelength to 1100.
μm to 1550 μm band, and resonator length L is 800 μm to
By using the 3200 μm band, laser light having a plurality of oscillation longitudinal modes, preferably three or more oscillation longitudinal modes, more preferably four or more oscillation longitudinal modes within the half-width Δλh of the oscillation wavelength spectrum 1030 is output. So
When used as a pumping light source for a Raman amplifier, stable Raman gain can be obtained without generating stimulated Brillouin scattering.

Further, unlike the semiconductor laser module using the fiber grating, the optical coupling between the optical fiber having the fiber grating and the semiconductor light emitting element is not performed in the resonator, so that the assembly is easy and the mechanical vibration causes Unstable output can be avoided.

In the sixth embodiment described above, the diffraction grating 1013 outputs a plurality of oscillation longitudinal modes by the wavelength selectivity having fluctuation with respect to the center wavelength. It is possible to obtain a semiconductor laser device capable of positively fluctuating and increasing the number of oscillation longitudinal modes.

FIG. 23 is a diagram showing periodic changes in the grating period of the diffraction grating 1013. This diffraction grating 1
013 is a chirped grating in which the grating period is changed periodically. In FIG. 24, fluctuations are generated in the wavelength selectivity of the diffraction grating 1013, the half width Δλh of the oscillation wavelength spectrum is widened, and the number of oscillation longitudinal modes within the half width Δλh is increased.

As shown in FIG. 23, the diffraction grating 1013
Has an average period of 220 nm, and has a structure in which a period fluctuation (deviation) of ± 0.02 nm is repeated in a period C. Due to this periodic fluctuation of ± 0.02 nm, it is possible to have about 3 to 6 oscillation longitudinal modes within the half-width Δλh of the oscillation wavelength spectrum.

For example, FIG. 24 shows that different periods Λ ₁ and Λ ₂
FIG. 6 is a diagram showing an oscillation wavelength spectrum of a semiconductor laser device having the diffraction grating of FIG. In FIG. 24, the diffraction grating with the period Λ ₁ forms an oscillation wavelength spectrum of wavelength λ ₁ and selects three oscillation longitudinal modes within this oscillation wavelength spectrum. On the other hand, the diffraction grating with the period Λ ₂ forms an oscillation wavelength spectrum of wavelength λ ₂ , and selects three oscillation longitudinal modes within this oscillation wavelength spectrum. Therefore, the composite oscillation wavelength spectrum 45 formed by the diffraction grating with the periods Λ ₁ and Λ ₂ includes 4 to 5 oscillation longitudinal modes in the composite oscillation wavelength spectrum 45. As a result, more oscillation longitudinal modes can be easily selected and output as compared with the case where a single oscillation wavelength spectrum is formed, and the optical output can be increased.

The structure of the diffraction grating 1013 is as follows.
Not only the chirped grating that changes the grating period with a constant period C but also the grating period,
Period Λ ₁ (220 nm + 0.02 nm) and period Λ ₂ (22
0 nm-0.02 nm) may be randomly changed.

Furthermore, as shown in FIG. 25 (a), a periodic fluctuation may be provided as a diffraction grating in which different periods Λ ₃ and Λ ₄ are alternately repeated once. Further, as shown in FIG. 25B, a periodic fluctuation may be provided as a diffraction grating in which different periods Λ ₅ and periods Λ ₆ are alternately repeated a plurality of times. further,
As shown in FIG. 25C, a plurality of consecutive cycles Λ ₇
And a period Λ ₇ and a plurality of periods Λ ₈ consecutively different from each other may be given as a diffraction grating having a period fluctuation. Also, the periods Λ ₃ , Λ ₅ , Λ ₇ and the periods Λ ₄ , Λ ₆ ,
Between Λ ₈ and δ _8, it is possible to complement the periods having discrete discrete values and to arrange the periods stepwise.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described. In the seventh embodiment, the semiconductor laser device shown in the sixth embodiment is modularized.

FIG. 26 is a longitudinal sectional view showing the structure of the semiconductor laser module according to the seventh embodiment of the present invention.
In FIG. 26, this semiconductor laser module 1050
Has a semiconductor laser device 1051 corresponding to the semiconductor laser device shown in the sixth embodiment. The semiconductor laser device 1051 has a junction-down structure in which the p-side electrode is joined to the heat sink 1057a. A package 10 formed of ceramic or the like as a housing of the semiconductor laser module 1050.
A Peltier element 1058 as a temperature control device is arranged on the inner bottom surface of 59. A base 1057 is arranged on the Peltier element 1058, and a heat sink 1057a is arranged on the base 1057. Peltier element 1
A current (not shown) is applied to 058, and cooling and heating are performed depending on its polarity.
In order to prevent the oscillation wavelength shift due to the temperature rise of 1, it mainly functions as a cooler. That is, the Peltier device 1
Reference numeral 058 indicates that when the laser light has a longer wavelength than the desired wavelength, it is cooled and controlled to a low temperature, and when the laser light has a shorter wavelength than the desired wavelength, it is heated. Control to high temperature. This temperature control is specifically controlled on the heat sink 1057a based on the detection value of the thermistor 1058a arranged in the vicinity of the semiconductor laser device 51, and a control device (not shown) normally controls the temperature of the heat sink 1057a. The Peltier element 1058 is controlled so that is maintained constant. In addition, the control device (not shown)
The Peltier element 1058 is controlled so that the temperature of the heat sink 1057a decreases as the drive current of the semiconductor laser device 1051 increases. By performing such temperature control, the output stability of the semiconductor laser device 1051 can be improved, which is also effective in improving the yield. The heat sink 1057a is preferably formed of a material having a high thermal conductivity such as diamond. This is because when the heat sink 1057a is formed of diamond, heat generation during high current driving is suppressed.

On the base 1057, the heat sink 1057a in which the semiconductor laser device 1051 and the thermistor 1058a are arranged, the first lens 1052, and the current monitor 1056 are arranged. Semiconductor laser device 1051
The laser light emitted from the laser beam passes through the first lens 1052, the isolator 1053, and the second lens 1054,
It is guided on the optical fiber 1055. Second lens 105
4 is on the optical axis of the laser beam, and is the package 1059.
It is optically coupled to an optical fiber 1055 which is provided above and is externally connected. The current monitor 1056 monitors and detects light leaking from the reflection film side of the semiconductor laser device 1051.

Here, the semiconductor laser module 10
In 50, an isolator 1053 is interposed between the semiconductor laser device 1051 and the optical fiber 1055 so that the reflected return light from other optical components does not return to the resonator. Unlike the conventional semiconductor laser module using a fiber grating, the isolator 1053 is not an in-line fiber type, but a polarization dependent type isolator that can be built in the semiconductor laser module 1050 can be used. Small insertion loss and lower relative intensity noise (RI
N) can be achieved and the number of parts can be reduced.

In the seventh embodiment, since the semiconductor laser device shown in the sixth embodiment is modularized, a polarization dependent isolator can be used, insertion loss can be reduced, and low noise can be achieved. And the reduction of the number of parts can be promoted.

(Embodiment 8) Next, an embodiment 8 of the invention will be described. In the eighth embodiment, the semiconductor laser module shown in the seventh embodiment is applied to a Raman amplifier.

FIG. 27 is a block diagram showing the structure of the Raman amplifier according to the eighth embodiment of the present invention. This Raman amplifier is used in a WDM communication system. FIG. 27
In this Raman amplifier, the Raman amplifier is
42 using semiconductor laser modules 1060a to 1060d having the same configuration as the semiconductor laser module shown in FIG.
Laser diode modules 182a to 182d shown in FIG.
The semiconductor laser modules 1060a to 1060 described above.
The configuration is replaced with 60d.

Each semiconductor laser module 1060a, 1
Reference numeral 060b is a polarization beam combiner 61a for converting laser light having a plurality of oscillation longitudinal modes via the polarization maintaining fiber 71.
To each semiconductor laser module 1060c, 10
60d outputs a laser beam having a plurality of oscillation longitudinal modes to the polarization beam combiner 61b via the polarization maintaining fiber 71. Here, the semiconductor laser module 1060
a, 1060b oscillate the laser light having the same wavelength, and the semiconductor laser modules 1060c, 106
The laser light emitted by 0d has the same wavelength, but is different from the wavelength of the laser light emitted by the semiconductor laser modules 1060a and 1060b. This is because the Raman amplification has polarization dependence, and the polarization combining couplers 61a and 61b.
Therefore, the laser light is output as a laser beam whose polarization dependence is eliminated.

The laser beams having different wavelengths output from the respective polarization combining couplers 61a and 61b are transmitted by the WDM coupler 6
The laser light combined by 2 is output to the amplification fiber 64 as Raman amplification pumping light via the WDM coupler 65. The signal light to be amplified is input to the amplification fiber 64 to which the pumping light is input, and Raman amplification is performed.

The signal light (amplified signal light) that has been Raman-amplified in the amplification fiber 64 passes through a WDM coupler 65 and an isolator 66, and a monitor light distribution coupler 67.
Entered in. The monitor light distribution coupler 67 outputs a part of the amplified signal light to the control circuit 68, and outputs the remaining amplified signal light to the signal light output fiber 70 as output laser light.

The control circuit 68 controls each of the semiconductor laser modules 1060a to 1060a-1 based on a part of the input amplified signal light.
The laser output state of 060d, for example, the light intensity is controlled,
Feedback control is performed so that the gain band of Raman amplification has a flat characteristic.

In the Raman amplifier shown in the eighth embodiment, for example, the semiconductor laser module 182a in which the semiconductor light emitting device 180a shown in FIG. 42 and the fiber grating 181a are coupled by the polarization maintaining fiber 71a.
Since the semiconductor laser module 1060a in which the semiconductor laser device shown in the sixth embodiment is incorporated is used instead of the above, the use of the polarization maintaining fiber 71 can be reduced, and the Raman amplifier is small and lightweight. And cost reduction can be realized.

In the Raman amplifier shown in FIG. 27,
Although the polarization combining couplers 61a and 61b are used in FIG.
The semiconductor laser modules 1060a, 1060a, 10
Alternatively, the light may be directly output from the 60c to the WDM coupler 62 via the polarization maintaining fiber 71.
In this case, the semiconductor laser modules 1060a and 106
The polarization plane of 0c is 45 with respect to the polarization-maintaining fiber 71.
It is incident so that it becomes a degree. Here, as described above, since each of the semiconductor laser modules 1060a and 1060c has a plurality of oscillation longitudinal modes, the polarization plane maintaining fiber length 71 can be shortened. As a result, it is possible to eliminate the polarization dependence of the optical output from the polarization maintaining fiber 71, and it is possible to realize a more compact Raman amplifier with a smaller number of components.

Further, the semiconductor laser module 1060a
If a semiconductor laser device having a large number of oscillation longitudinal modes is used as the semiconductor laser device incorporated in each of ˜1060d, the required length of the polarization maintaining fiber 71 can be shortened. Especially when the oscillation longitudinal mode becomes 4 or 5,
Since the required length of the polarization maintaining fiber 71 is shortened,
The Raman amplifier can be simplified and downsized. Furthermore, as the number of oscillation longitudinal modes increases, the coherence length becomes shorter, and the polarization degree (D
OP: Degree Of Polarization) becomes smaller, and it becomes possible to eliminate the polarization dependence, which also facilitates simplification and miniaturization of the Raman amplifier.

Further, in this Raman amplifier, the optical axis alignment is easier than in a semiconductor laser module using a fiber grating, and there is no mechanical optical coupling in the resonator. The stability and reliability of can be improved.

Furthermore, since the semiconductor laser device of the sixth embodiment described above has a plurality of oscillation modes, it is possible to generate high-power pumping light without causing stimulated Brillouin scattering. Stable and high Raman gain can be obtained.

The Raman amplifiers shown in FIGS. 27 and 28 are of the backward pumping type, but are of the forward pumping type because the semiconductor laser modules 1060a to 1060d output stable pumping light as described above. Also, stable Raman amplification can be performed even with the bidirectional pumping method.

For example, FIG. 29 is a block diagram showing the configuration of a Raman amplifier when the forward pumping method is adopted. The Raman amplifier shown in FIG. 29 has the WDM coupler 65 ′ provided near the isolator 63 in the Raman amplifier shown in FIG. 27. The WDM coupler 65 'includes semiconductor laser modules 1060a to 1060d, semiconductor laser modules 1060a' to 1060d corresponding to the polarization combining couplers 61a and 61b and the WDM coupler 62, respectively.
′, A circuit having polarization combining couplers 61 a ′, 61 b ′ and a WDM coupler 62 ′ is connected, and the WDM coupler 62
Forward pumping is performed in which the pumping light output from ′ is output in the same direction as the signal light. In this case, the semiconductor laser module 1
Since 060a 'to 060d' use the semiconductor laser device used in the sixth embodiment, the RIN
Is small, and forward excitation can be effectively performed.

Similarly, FIG. 30 is a block diagram showing the structure of a Raman amplifier adopting the forward pumping method. Figure 30
In the Raman amplifier shown in FIG. 28, the WDM coupler 65 ′ is provided near the isolator 63 in the Raman amplifier shown in FIG. 28. The WDM coupler 65 'includes semiconductor laser modules 1060a and 1060c and a WDM coupler 6.
2 laser diode module 1060
A circuit having a ′, 1060c ′ and the WDM coupler 62 ′ is connected to perform forward pumping in which the pumping light output from the WDM coupler 62 ′ is output in the same direction as the signal light. In this case, the semiconductor laser modules 1060a ', 106
0c 'uses the semiconductor laser device used in the sixth embodiment described above, so that RIN is small and forward pumping can be effectively performed.

FIG. 31 is a block diagram showing the structure of a Raman amplifier when the bidirectional pumping method is adopted. Figure 3
The Raman amplifier shown in FIG. 1 has the same structure as the Raman amplifier shown in FIG. 27 except that the WDM coupler 65 ′ shown in FIG. 29, the semiconductor laser modules 1060a ′ to 1060d ′, the polarization combining couplers 61a ′ and 61b ′, and the WDM coupler. 62
′ Is further provided to perform backward excitation and forward excitation. In this case, the semiconductor laser modules 1060a 'to 1060d
In ′, since the semiconductor laser device used in the above-described sixth embodiment is used, RIN is small, and forward pumping can be effectively performed.

Similarly, FIG. 32 is a block diagram showing the structure of a Raman amplifier adopting the bidirectional pumping method. Figure 3
The Raman amplifier shown in FIG. 1 further includes a WDM coupler 65 ′ shown in FIG. 30, semiconductor laser modules 1060a ′ and 1060c ′, and a WDM coupler 62 ′ in the configuration of the Raman amplifier shown in FIG. Excite and perform. In this case, the semiconductor laser module 1060
Since a ′ and 1060c ′ use the semiconductor laser device used in the sixth embodiment described above, RIN is small and forward pumping can be effectively performed.

The Raman amplifiers shown in FIGS. 29 to 32 described above can be applied to the WDM communication system as described above. FIG. 33 is a block diagram showing a schematic configuration of a WDM communication system to which the Raman amplifier shown in FIGS. 29 to 32 is applied.

In FIG. 33, a plurality of transmitters Tx1 to Tx are provided.
The optical signals of wavelengths λ _{1 to} λ _n transmitted from xn are combined by the optical multiplexer 1080, and one optical fiber 1085
Are summarized in. On the transmission path of the optical fiber 1085, a plurality of Raman amplifiers 1081 and 1083 corresponding to the Raman amplifiers shown in FIGS. 29 to 32 are arranged according to the distance to amplify the attenuated optical signal. This optical fiber 1
The signal transmitted over 085 is demultiplexed by the optical demultiplexer 1084 into optical signals having a plurality of wavelengths λ _{1 to} λ _n , and received by the plurality of receivers Rx1 to Rxn. The optical fiber 1
In some cases, an ADM (Add / Drop Multiplexer) for adding and extracting an optical signal of an arbitrary wavelength is inserted on the 085.

In the eighth embodiment described above, the semiconductor laser device shown in the sixth embodiment or the seventh embodiment is used.
Although the case where the semiconductor laser module shown in (4) is used as a pumping light source for Raman amplification is shown, it is obvious that the semiconductor laser module can be used as a light source for pumping EDFA such as 980 nm and 1480 nm without being limited to this.

(Ninth Embodiment) Next, a semiconductor laser device according to a ninth embodiment will be described. In the semiconductor laser device according to the eighth embodiment, by stacking two types of active layers, a compressive strain quantum well active layer and a tensile strain quantum well active layer, a TE mode laser beam and a TM mode laser beam are polarized. It is characterized in that wave synthesis is performed in the package, and laser light with low DOP, low cost, and high output power is output.

FIG. 34 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the ninth embodiment. Furthermore, FIG.
FIG. 35 is a cross-sectional view taken along the line AA of the semiconductor laser device shown in FIG. 34. Referring to FIG. 34, the semiconductor laser device according to the ninth embodiment includes an n-InP buffer layer 2002a, which sequentially serves as a buffer layer of n-InP and a lower cladding layer, on the (100) plane of the n-InP substrate 2001. , Compression strain GRIN-SCH-MQW (Graded Index-Separate
Confinement Heterostructure Multi QuantumWell) Active layer 2003a, p-InP spacer layer 2004a, p
-InP clad layer 2006a, tunnel junction layer 2005, n-InP clad layer 2002b, tensile strain GRIN-SCH-MQW active layer 2003b, p
An -InP spacer layer 2004b and a p-InP clad layer 2006b are laminated and configured.

A p-InGaAsP cap layer 2007 and a p-side electrode 2010 are sequentially stacked on the p-InP clad layer 2006b, and an n-side electrode 2011 is formed on the back surface of the n-InP substrate 2001.

Further, as shown in FIG. 34, a reflection film 2014 having a high light reflectance of 80% or more is formed on the light reflection end surface which is one end surface in the longitudinal direction of the semiconductor laser device, and the other end surface is formed. A certain light emitting end face has a reflectance of 2% or less,
Emission side reflection film 2 having a low light reflectance of preferably 1% or less
015 is formed. Reflection film 2014 and emission side reflection film 2
Compressive strain GRIN of the optical resonator formed by
-SCH-MQW active layer 2003a and tensile strain G
The light generated in the RIN-SCH-MQW active layer 2003b is reflected by the reflection film 2014, and the light is emitted from the emission side reflection film 2.
It is emitted as laser light via 015.

Further, the semiconductor laser device shown in FIG. 34 has diffraction gratings 2013a and 2013b of p-InGaAsP periodically arranged in p-InP spacer layers 2004a and 2004b, respectively. In particular, here, the diffraction gratings 2013a and 2013b have a central wavelength of 1.48 μm in the laser light generated in each gain region of the compressive strain GRIN-SCH-MQW active layer 2003a and the tensile strain GRIN-SCH-MQW active layer 2003b.
Light having a thickness of 20 nm and a pitch of about 2 over the length of about 100 μm from the exit end face.
It is assumed that the thickness is 20 nm. It is desirable that the diffraction gratings 2013a and 2013b are arranged from the position in contact with the emission end face, but the diffraction gratings 2013a and 2013b do not necessarily have to be arranged in contact with each other within a range in which the functions of the diffraction gratings 2013a and 2013b are exhibited, for example, about 20 μm to 100 μm It can also be arranged at a position separated from the central surface within the range of.

As shown in FIG. 35, the upper portion of the n-InP buffer layer 2002a, the compressive strain GRIN-SCH-.
MQW active layer 2003a, diffraction grating 2013a described above
Containing p-InP spacer layer 2004a, p-InP clad layer 2006a, tunnel junction layer 200
5, n-InP clad layer 2002b, tensile strain GR
IN-SCH-MQW active layer 2003b, p-InP spacer layer 2004b including the above-mentioned diffraction grating 2013b.
Are processed into a mesa stripe shape, and p-InP formed on both sides of the mesa stripe as a current blocking layer.
Blocking layer 2008 and n-InP blocking layer 2
It is embedded by 009.

Here, the strained quantum well will be briefly described. The double hetero structure including quantum wells is usually composed of a combination of lattice-matched semiconductor mixed crystals.
A thin quantum well of 0 nm or less can be formed with a crystal composition having a slight lattice mismatch with the semiconductor substrate. When the lattice constant of the well is larger than that of the barrier, the strained quantum well has a compressive strain, and when the lattice constant of the well is reversed, the strained quantum well has a tensile strain.

A typical example is InGaAs well layer / Ga.
It is an As substrate and an InGaAs (or InGaAsP) well layer / InP substrate. The former is a compression strain type, and the latter can realize both types depending on the composition. Since such strain deforms the band structure of the quantum well, it is possible to realize characteristics useful for improving the performance of the semiconductor laser device by appropriate design.

In particular, due to the band structure, the upper end of the heavy hole band is the upper end of the valence band in compression strain, and the transition between the electron and the heavy hole is the main transition. It is known that this transition mainly contributes to oscillation of TE mode laser light. On the other hand, due to the band structure, at the tensile strain, the upper end of the light hole band becomes the upper end of the valence band, and the transition between the electron and the light hole becomes the main transition.
It is known that this transition mainly contributes to oscillation of TM-mode laser light. Therefore, from the compressive strain GRIN-SCH-MQW active layer 2003a shown in FIG.
Mode laser light can be selectively emitted, and TM mode laser light can be selectively emitted from the tensile strain GRIN-SCH-MQW active layer 2003b.

The characteristics of this semiconductor laser device will be described below. When the semiconductor laser device described above is used as a pumping light source for a Raman amplifier, its oscillation wavelength λ
₀ is set to 1100 nm to 1550 nm, and the resonator length L determined by the interval between the reflection film 2014 and the emission side reflection film 2015 is set to 800 μm or more and 3200 μm or less.
By the way, in general, the mode interval Δλ of the longitudinal mode generated by the resonator of the semiconductor laser device can be expressed by the following equation, where the equivalent refractive index is “n”. That is, Δλ = λ ₀ ² / (2 · n · L). Here, when the oscillation wavelength λ0 is 1480 nm and the effective refractive index is 3.5, when the cavity length L is 800 μm, the mode interval Δλ of the longitudinal mode is about 0.39 nm, and when the cavity length is 3200 μm. The mode interval Δλ of the longitudinal mode is about 0.1 nm. That is, the longer the resonator length L, the longer the mode interval Δλ of the longitudinal mode.
Becomes narrower, and the selection condition for oscillating a single longitudinal mode laser beam becomes stricter.

On the other hand, the diffraction gratings 2013a and 2013b
Selects the longitudinal mode according to its Bragg wavelength. FIG. 36 is a graph for explaining the selection wavelength characteristic of the diffraction gratings 2013a and 2013b.
The selected wavelength characteristics of 3a and 2013b are represented as an oscillation wavelength spectrum 2030 as illustrated.

In particular, in this semiconductor laser device, as shown in FIG. 36, due to the existence of the diffraction gratings 2013a and 2013b, there are a plurality of oscillation longitudinal modes within the wavelength selection characteristic indicated by the half width Δλh of the oscillation wavelength spectrum 2030. Designed to do. In the conventional semiconductor laser device, when the resonator length L is 800 μm or more, single longitudinal mode oscillation is difficult, and therefore the semiconductor laser device having such resonator length L is not used, but this semiconductor laser device is not used. Then, by positively setting the cavity length L to 800 μm or more, laser light including a plurality of oscillation longitudinal modes is output within the half-width Δλh of the oscillation wavelength spectrum. In FIG. 36,
There are three oscillation longitudinal modes 2031 to 2033 within the half width Δλh of the oscillation wavelength spectrum.

When the laser light having a plurality of oscillation longitudinal modes is used, the peak value of the laser output can be suppressed and a high laser output value can be obtained as compared with the case where the laser light of the single longitudinal mode is used. . FIG. 37 is an explanatory diagram for describing each profile of laser light of a single longitudinal mode and laser light of a plurality of oscillation longitudinal modes. For example, the semiconductor laser device section described above has the profile shown in FIG. 37 (b), and a high laser output can be obtained with a low peak value. On the other hand, FIG. 37A shows a profile of a semiconductor laser device section of single longitudinal mode oscillation when the same laser output is obtained, and has a high peak value.

Here, when the semiconductor laser device according to the ninth embodiment is used as a pumping light source of a Raman amplifier,
It is preferable to increase the pumping light output power in order to increase the Raman gain, but if the peak value is high, stimulated Brillouin scattering occurs and noise increases. Stimulated Brillouin scattering occurs when the laser output exceeds a threshold Pth at which stimulated Brillouin scattering occurs, as shown in FIG. Therefore, in this semiconductor laser device, in order to obtain the same laser output power as the profile shown in FIG. 37A, as shown in FIG. 37B, a plurality of peak values are suppressed below the threshold value Pth of stimulated Brillouin scattering. The laser light is emitted in the oscillation longitudinal mode of. Thereby, high pumping light output power can be obtained, and as a result, high Raman gain can be obtained.

Further, in FIG. 36, the oscillation longitudinal mode 20
The wavelength intervals (mode intervals) Δλ of 31 to 2033 are 0.
It is set to 1 nm or more. This is because when this semiconductor laser device is used as a pumping light source for a Raman amplifier, if the mode interval Δλ is 0.1 nm or less, stimulated Brillouin scattering is likely to occur. As a result,
According to the above equation of the mode interval Δλ, it is preferable that the above-mentioned resonator length L is 3200 μm or less. From such a viewpoint, the oscillation wavelength spectrum 2030
It is desirable that the number of oscillation longitudinal modes included in the half-width Δλh of is plural.

Therefore, as described above, in the semiconductor laser device according to the ninth embodiment, the arrangement positions of the diffraction gratings 2013a and 2013b are set so that two or more oscillation longitudinal modes are included in the half width of the oscillation wavelength spectrum. Since the resonator length L is set, the laser output of high output can be stably obtained without causing stimulated Brillouin scattering.

In the structure shown in FIG. 34, the p-side electrode 2
010 and the n-side electrode 2011, the current applied between the p-InP cladding layer 2006b and the tensile strain G
RIN-SCH-MQW active layer 2003b, n-InP
The TM-mode laser light is emitted from the tensile strain GRIN-SCH-MQW active layer 2003b biased in the forward direction to the cladding layer 2002b. However, the n-InP cladding layer 2002b and p-In located under the tensile strain GRIN-SCH-MQW active layer 2003b.
Since the P clad layer 2006a is joined with a reverse bias, if the two are joined as they are, the compressive strain GR in the lower layer is
No current is injected into the IN-SCH-MQW active layer 2003a.

Therefore, as shown in FIG. 34, n-InP
Cladding layer 2002b and p-InP cladding layer 2006
A tunnel junction layer 2005 is provided between a and a. As a result, a tunnel current is effectively flowed from the n-InP cladding layer 2002b to the tunnel junction layer 2005, and the tunnel junction layer 2005 is formed.
Through the p-InP clad layer 2006a and compressive strain G
RIN-SCH-MQW active layer 2003a, n-InP
A forward bias current can be supplied to the buffer layer 2002a. The tunnel junction layer 2005 is
For example, it can be formed of n-type and p-type semiconductors that are heavily doped with impurities.

As a result, the emitting side reflection film 2 which becomes the emitting end face.
Although TM mode and TE mode laser beams are emitted from 015, since the emission end positions of the compressive strain GRIN-SCH-MQW active layer 2003a and the tensile strain GRIN-SCH-MQW active layer 2003b are close to each other, this semiconductor From the laser device, high-power laser light in a state where both are combined without interference can be obtained.

That is, this semiconductor laser device can output polarization-combined high-power laser light without using a polarization combiner. In other words, this semiconductor laser device can output laser light with DOP reduced by orthogonal polarization combining.

As described above, according to the semiconductor laser device of the ninth embodiment, in the semiconductor laser device which outputs a plurality of oscillation longitudinal mode laser beams below the threshold value at which stimulated Brillouin scattering occurs, the compressive strain quantum By stacking two types of active layers, that is, a well active layer and a tensile strained quantum well active layer, polarization synthesis of TE mode laser light and TM mode laser light is performed, and thus DOP can be reduced. It is possible to emit a laser beam having a large output.

(Embodiment 10) Next, Embodiment 1 will be described.
A semiconductor laser device according to No. 0 will be described. The semiconductor laser device according to the tenth embodiment has a compressive strain in comparison with the ninth embodiment, which has independent compressive strain quantum well active layer and tensile strain quantum well active layer with the cladding layer interposed therebetween. It is characterized in that a quantum well active layer and a tensile strained quantum well active layer are continuously laminated, and a set of clad layers is provided for the laminated portion.

FIG. 38 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the tenth embodiment. Note that FIG.
In FIG. 34, the same parts as those in FIG. 34 are designated by the same reference numerals and the description thereof will be omitted. In the semiconductor laser device shown in FIG. 38, the difference from FIG. 34 is tensile strain GR.
IN-SCH-MQW active layer 2003b and compressive strain GRI
N-In between N-SCH-MQW active layer 2003a
P buffer layer 2002b, tunnel junction layer 2
005, p-InP cladding layer 2006a and p-I
The nP spacer layer 2004a is eliminated, and the tensile strain GR
IN-SCH-MQW active layer 2003b and compressive strain GRI
This is a point where the N-SCH-MQW active layer 2003a is adjacent to the N-SCH-MQW active layer 2003a.

That is, in the semiconductor laser device according to the tenth embodiment, on the (100) plane of the n-InP substrate 2001, an n-InP buffer layer which serves as a buffer layer and a lower cladding layer of n-InP are sequentially formed. 2002, compressive strain GRIN-SCH-MQW active layer 2003a, tensile strain GRIN-SCH-MQW active layer 2003b, p-I
nP spacer layer 2004, p-InP clad layer 200
It is configured by laminating 6 layers. Regarding the cross-sectional view of the semiconductor laser device according to the tenth embodiment,
As shown in FIG. 35, a buried hetero structure is formed in which both sides are filled with a blocking layer.

Therefore, in this semiconductor laser device, compressive strain GRIN-SCH-MQW stacked vertically adjacent to each other.
Active layer 2003a and tensile strain GRIN-SCH-MQ
By considering the W active layer 2003b as one active layer and sandwiching the active layer between the clad layers, high output power obtained by polarization-combining the TM mode laser light and the TE mode laser light as in the ninth embodiment. The laser light of is output. Note that FIG.
Similarly, the tensile strain GRIN-SCH-MQW between the active layer 2003b and the p-InP cladding layer 2006 is p.
Since the -InP spacer layer 2004 is provided and the diffraction grating 2013 is formed in the p-InP spacer layer 2004 under the conditions described in the ninth embodiment, the laser light output from this semiconductor laser device has a plurality of oscillation longitudinal directions. Have a mode.

As described above, according to the semiconductor laser device of the tenth embodiment, the compressive strain quantum well active layer and the tensile strain quantum well active layer are continuously laminated, and one set is provided for the laminated portion. With the configuration having the clad layer, the effect similar to that of the ninth embodiment can be obtained.

(Embodiment 11) Next, Embodiment 1 will be described.
The semiconductor laser device according to No. 1 will be described. In the semiconductor laser device according to the eleventh embodiment, the compressive strain quantum well active layer and the tensile strain quantum well active layer are vertically stacked in the above-described ninth and tenth embodiments, but both are arranged in the emitting direction. It is characterized by matching.

FIG. 39 is a longitudinal sectional view of the semiconductor laser device according to the eleventh embodiment in the longitudinal direction. The semiconductor laser device shown in FIG. 39 has (10) of an n-InP substrate 2001.
0) plane, the n-InP buffer layer 2002a, the compressive strain GRIN-SCH-MQW active layer 2003a, and the p-In.
A laminated structure composed of a P clad layer 2006a,
n-InP clad layer 2002c and tensile strain GRIN
A laminated structure composed of the -SCH-MQW active layer 2003b, the p-InP spacer layer 2004b, and the p-InP clad layer 2006b is a so-called butt-bonded form.

Particularly, in this butt coupling, at least the compressive strain GRIN-SCH-MQW active layer 200.
3a and tensile strain GRIN-SCH-MQW active layer 20
Place it so that it is connected to 03b. Thereby, the compressive strain GRIN-SCH-MQW active layer 2003
The TE-mode laser light generated in a has tensile strain G
The light is transmitted through the RIN-SCH-MQW active layer 2003b and is emitted to the outside in a state of being polarization-combined with the TM mode laser light generated in the tensile strain GRIN-SCH-MQW active layer 2003b.

Further, a p-InGaAsP cap layer 2007a and a p-side electrode 2010a are sequentially stacked on the p-InP clad layer 2006a, and a p-InGaAsP cap layer 20 is formed on the p-InP clad layer 2006b.
07b and p-side electrode 2010b are sequentially stacked. Furthermore, the set of the p-InGaAsP cap layer 2007a and the p-side electrode 2010a, and the p-InGaAsP cap layer 2
A separation groove 2022 is formed at the boundary between the set of 007b and the p-side electrode 2010b, as shown in the drawing. By this separation groove 2022, both sets are arranged in a state of being substantially electrically insulated. An n-side electrode 2011 is formed on the back surface of the n-InP substrate 2001.

That is, the injection current is controlled by the voltage applied between the p-side electrode 2010a and the n-side electrode 2011, and the compressive strain GRIN-SCH-MQW active layer 2003 is formed.
It is possible to adjust the output power of the TE-mode laser light generated by a.
The output power of the TM-mode laser light generated in the tensile strain GRIN-SCH-MQW active layer 2003b can be adjusted by controlling the injection current by the voltage applied to the side electrode 2011.

[0232] The p-InGaAsP cap layers 2007a and 2007 described above were formed without providing the isolation groove 2022.
b is a continuous p-InGaAsP cap layer, and on the p-InGaAsP cap layer,
One p-side electrode is provided instead of the above-mentioned p-side electrodes 2010a and 2010b, and the compressive strain GRIN-SCH-MQW active layer 2003a and the tensile strain GRIN-SCH-M are provided.
The same applied voltage may be always applied to the QW active layer 2003b.

As for the sectional view of the semiconductor laser device according to the eleventh embodiment, as shown in FIG. 35, it has a buried hetero structure in which both sides are filled with blocking layers.
With such a structure, the light whose single transverse mode is controlled is emitted. Further, since the diffraction grating 2013 is formed in the p-InP spacer layer 2004 under the conditions described in the ninth embodiment, the laser light output from this semiconductor laser device is
It has a plurality of oscillation longitudinal modes.

As described above, according to the semiconductor laser device of the eleventh embodiment, the compressive strain quantum well active layer and the tensile strain quantum well active layer are abutted in the emitting direction to be coupled to each other, so that the embodiment It is possible to enjoy the same effect as in item 9.

In the ninth to eleventh embodiments described above, compressive strain GRIN-SCH-MQW active layer 2003a.
And the number of pairs of the tensile strain GRIN-SCH-MQW active layer 2003b do not have to be the same, and may be different so that the laser light of each mode is optimally output.

(Embodiment 12) Next, Embodiment 1 will be described.
The semiconductor laser module according to No. 2 will be described.
The semiconductor laser module according to the twelfth embodiment is a form in which the semiconductor laser device according to the ninth to eleventh embodiments is enclosed in a package together with various optical components, and the laser light generated by the semiconductor laser device is sent to an optical fiber. It is modularized for the purpose of making it easily incident.

FIG. 40 is a longitudinal sectional view showing the structure of the semiconductor laser module according to the twelfth embodiment. Figure 40
In the semiconductor laser module 2080, the Peltier element 2094 described above is arranged on the inner bottom surface of the package 2081 formed of ceramic or the like. On the Peltier element 2094, the above-mentioned base 209 is provided.
2 is arranged, and the semiconductor laser device 2090 is arranged on the base 2092. Here, semiconductor laser device 2090 corresponds to the semiconductor laser device shown in the ninth to eleventh embodiments.

The Peltier element 2094 and the base 20
In the configuration including the 92 and the semiconductor laser device 2090, a current (not shown) is applied to the Peltier element 2094, and cooling and heating are performed depending on the polarity thereof.
The semiconductor laser device 2090 mainly functions as a cooler in order to prevent oscillation wavelength shift due to temperature rise. That is, the Peltier device 2094 cools the laser light to a low temperature when the wavelength of the laser light is longer than the desired wavelength, and controls the laser light to a low temperature when the wavelength of the laser light is shorter than the desired wavelength. Is heated and controlled to a high temperature. This temperature control is controlled based on a detection value of a thermistor (not shown) arranged near the semiconductor laser device 2090, and the control device (not shown) normally keeps the temperature of the semiconductor laser device 2090 constant. The Peltier device 2094 is controlled. Further, the control device (not shown) controls the Peltier element 20 so that the temperature of the semiconductor laser device 2090 decreases as the drive current of the semiconductor laser device 2090 increases.
Control 94. By performing such temperature control, the wavelength stability of the semiconductor laser device 2090 can be improved, which is also effective in improving the yield.

In FIG. 40, on the base 2092,
In addition to the semiconductor laser device 2090, an optical monitor 208
3, the first lens 2084 and the isolator 2085 are arranged. Further, in the semiconductor laser module 2080, the second lens 2086 is arranged inside the portion where the optical fiber 2082 is loaded.

The laser light emitted from the semiconductor laser device 2090 is the first lens 2084 and the isolator 208.
5 and the second lens 2086, the optical fiber 208
Guided in 2. The second lens 2086 is provided on the package 2081 on the optical axis of the laser light, and is optically coupled to the optical fiber 2082 connected to the outside. The optical monitor 2083 monitors and detects the light leaked from the reflective film side of the semiconductor laser device 2090.

Further, by the isolator 2085 between the semiconductor laser device 2090 and the optical fiber 2082,
Reflected return light from other optical components returns to the resonator,
This prevents stray light from adversely affecting the oscillation and detection operations.

FIG. 41 is an explanatory diagram for explaining a case where this semiconductor laser module is used in a Raman amplifier or an HPU used in an EDFA. Note that, in FIG. 34, 2080a to 2080f correspond to the semiconductor laser module 2080 shown in FIG. As described above, the semiconductor laser device according to the ninth to eleventh embodiments is
Since DOP can be reduced without using a polarization combiner,
P required in each laser unit shown in FIG.
Since the BC 132 can be eliminated and the output power can be increased by increasing the injection current, a plurality of semiconductor laser modules 134 and the WDM coupler 132 can be included in one laser unit that outputs laser light of the same wavelength. No need to provide. Furthermore, the ninth embodiment
Since the semiconductor laser devices according to Nos. 11 to 11 can output a laser beam having a stable wavelength by including a diffraction grating therein, the FBG 133 is not an essential element.

As described above, according to the semiconductor laser module of the twelfth embodiment, the ninth embodiment is described.
Since the semiconductor laser devices shown by 11 to 11 are modularized, it is possible to suppress the returning light by using the polarization-dependent isolator, and it is possible to promote the reduction of noise and the reduction of the number of components.

In the twelfth embodiment described above, the example in which the isolator 2085 is provided in the module has been shown, but the isolator is not necessarily an essential structure. Further, in the present embodiment, the semiconductor laser element includes the diffraction grating, but when the FBG is used, the semiconductor laser device may have a structure not including the diffraction grating.

Further, in the ninth to twelfth embodiments described above.
And the oscillation wavelength λ of the semiconductor laser device ₀Is 1480 nm
However, for example, 980 nm, etc.
Even if a semiconductor laser device with another oscillation wavelength is
It goes without saying that the invention can be applied. It
Moreover, the present invention is applied not only to Raman amplifiers but also to EDFAs.
It goes without saying that it can be applied.

[0246]

As described above, according to the first aspect of the invention, by providing the non-current injection region in which the injection current does not flow into a part of the diffraction grating, the diffraction having a single period, for example. Even if the grating is different from the center wavelength selected by the diffraction grating in the non-current injection region and the center wavelength selected by the diffraction grating in the region where current is injected, it performs the same function as having multiple diffraction gratings. There is an effect that can be.

According to the second aspect of the invention, by arranging the insulating film, it is possible to effectively prevent the injection current from flowing into the non-current injection region.

According to the third aspect of the present invention, the optical output of the oscillating laser light is controlled by providing the first electrode with the structure in which the first portion and the second portion are spatially separated. With this, it is possible to independently control the central wavelength selection by passing a current through a part of the diffraction grating.

Further, according to the invention of claim 4, the third electrode is further provided with the third portion, whereby the refractive index of the diffraction grating can be controlled more efficiently.
The yield of the semiconductor laser device can be improved.

Further, according to the invention of claim 5, since the active layer is sandwiched from above and below by the clad layers, a double hetero structure is formed and carriers are concentrated in the active layer.
The semiconductor laser device that oscillates laser with high efficiency can be realized.

According to the invention of claim 6, by using the above semiconductor laser device, it is not necessary to perform fiber grading, there is no need to perform optical axis alignment, etc., and it is easy to assemble and oscillates due to mechanical vibration or the like. It is possible to realize a semiconductor laser module whose characteristics do not change.

According to the invention of claim 7, the light output can be monitored by providing the photodetector, the light output can be stabilized, and the light reflected from the outside can be provided by providing the isolator. There is an effect that can be prevented.

According to the invention of claim 8, an optical fiber amplifier having a high amplification factor and capable of stable amplification can be realized by including the semiconductor laser device or the semiconductor laser module. It has the effect of being able to.

Further, according to the invention of claim 9, there is an effect that the optical amplification can be more preferably performed by performing the Raman amplification.

According to the invention of claim 10, the diffraction grating is provided in the vicinity of the first reflection film, and is formed at a distance of 50 μm or less from the first reflection film.
The wavelength instability caused by the change in the refractive index of the diffraction grating due to the temperature rise of the end surface of the first reflective film is eliminated, and
Since the kink caused by the oscillating longitudinal mode hop is eliminated by not separating over m, stable longitudinal multimode oscillation is realized, so that high wavelength stability and stable longitudinal multimode operation are realized. There is an effect that can be.

According to the invention of claim 11, the separation distance between the diffraction grating and the first reflection film is 10 to 20 μm.
With the range of m, high wavelength stability and stable vertical multi-mode operation can be realized.

According to the twelfth aspect of the present invention, the number of the desired oscillation longitudinal modes is set to be two or more within the half-width of the oscillation wavelength spectrum by the wavelength selection characteristic of the diffraction grating, and the high number of oscillation longitudinal modes is increased. Since the output laser light is output, even in a high-output semiconductor laser device,
The effect that the oscillation wavelength selected by the diffraction grating can be output stably and highly efficiently is obtained.

According to the thirteenth aspect of the invention, the diffraction grating length of the diffraction grating provided on the first reflection film side is 30
Since the thickness is 0 μm or less, it is possible to easily generate two or more oscillation longitudinal modes and to improve the efficiency of light output.

According to the fourteenth aspect of the present invention, the diffraction grating length of the diffraction grating provided on the first reflection film side is set to a value equal to or less than (300/1300) times the resonator length. With respect to the resonator length of 1), it is possible to easily generate two or more oscillation longitudinal modes and to improve the optical output efficiency of high output.

According to the fifteenth aspect of the present invention, in the diffraction grating, the multiplication value of the coupling coefficient of the diffraction grating and the diffraction grating length is 0.3 or less, and the linearity of the drive current-optical output characteristic is set. Since it is improved and the stability of the optical output is improved, the dependency of the oscillation wavelength on the driving current can be reduced, and a semiconductor laser device with high output stability can be realized.

According to the sixteenth aspect of the present invention, the grating period of the diffraction grating is changed randomly or at a predetermined period to cause fluctuations in the wavelength selection of the diffraction grating and to widen the half value width of the oscillation wavelength spectrum. Therefore, the number of oscillation longitudinal modes included in the half-width of the oscillation wavelength spectrum can be easily increased, and a stable and highly efficient semiconductor laser device can be realized.

According to the seventeenth aspect of the invention, the resonator formed by the active layer formed between the first reflective film and the second reflective film has a length of 800 μm or more, Since the output operation is possible, there is an effect that a high output operation is possible and the oscillation wavelength selected by the diffraction grating can be stably and efficiently output.

Further, according to the eighteenth aspect of the invention, since the resonator of the semiconductor laser device is not physically separated by using the semiconductor laser device which does not use the fiber grating, it is necessary to perform optical axis alignment or the like. , The semiconductor laser module can be easily assembled, the oscillation characteristics of the laser are less likely to change due to mechanical vibration, etc., and stable laser light can be output reliably and stably, further reducing cost. The effect is that a semiconductor laser module that can be realized can be realized.

According to the nineteenth aspect of the invention, since the semiconductor laser device which does not use the fiber grating is used, the polarization dependent isolator can be used unlike the in-line type fiber type, and the insertion loss is reduced. The semiconductor laser module having a small size and a small RIN can be realized.

According to the invention of claim 20, the semiconductor laser device according to any one of claims 10 to 17,
Alternatively, the semiconductor laser module according to claim 18 or 19 is used as an excitation light source for wideband Raman amplification,
The semiconductor laser device or the semiconductor laser module described above is brought into effect, and the oscillation wavelength selected by the diffraction grating can be output stably and highly efficiently.

According to the invention of claim 21, the semiconductor laser device according to any one of claims 10 to 17,
Alternatively, the semiconductor laser module according to claim 18 or 19 is a pumping light source for wideband Raman amplification,
It is used as a forward pumping light source or a forward pumping light source in a bidirectional pumping system, and the above-mentioned semiconductor laser device or each semiconductor laser module is made to exhibit the action and effect, and the oscillation wavelength selected by the diffraction grating is stable and highly efficient. The effect that it can output is produced.

Further, according to the semiconductor laser device of the present invention, in the semiconductor laser device which outputs a plurality of oscillation longitudinal mode laser beams below the threshold value at which stimulated Brillouin scattering occurs, the compressive strain quantum well active layer and the tensile strain By stacking two types of active layers of the quantum well active layer, polarization synthesis of the TE mode laser light and the TM mode laser light is performed, so that DOP can be reduced and
It is possible to emit a laser beam having a large output.

Further, according to the semiconductor laser module of the present invention, it is possible to provide the above-mentioned semiconductor laser device in the state of being enclosed in the package housing.

Further, according to the optical fiber amplifier of the present invention, by using the semiconductor laser module as the excitation light source of the EDFA or the Raman amplifier, it is possible to reduce the noise and the number of parts. Play.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a structure of a semiconductor laser device according to a first embodiment.

2 is a cross-sectional view of the semiconductor laser device shown in FIG. 1 taken along the line AA.

FIG. 3 is a relationship diagram between an oscillation wavelength spectrum and an oscillation longitudinal mode for one center wavelength in the semiconductor laser device shown in FIG.

FIG. 4 is a diagram showing a relationship between laser light output powers in a single-oscillation longitudinal mode and a plurality of oscillation longitudinal modes and thresholds of stimulated Brillouin scattering.

FIG. 5 is a diagram showing a composite oscillation wavelength spectrum composed of laser light having two central wavelengths emitted from the semiconductor laser device according to the first embodiment, and a plurality of oscillation longitudinal modes.

FIG. 6 is a side sectional view showing a structure of a semiconductor laser device according to a second embodiment.

FIG. 7 is a diagram showing a light output characteristic of the semiconductor laser device according to the second embodiment.

FIG. 8 is a side sectional view showing a structure of a semiconductor laser device according to a third embodiment.

FIG. 9 is a side sectional view showing a configuration of a semiconductor laser module according to a fourth embodiment.

FIG. 10 is a block diagram showing a configuration of a Raman amplifier according to a fifth embodiment.

FIG. 11 is a block diagram showing a configuration of a modified example of the Raman amplifier according to the fifth exemplary embodiment.

FIG. 12 is a block diagram showing a schematic configuration of a WDM communication system using a Raman amplifier according to a fifth embodiment.

FIG. 13 is a cutaway view of a semiconductor laser device according to a sixth embodiment of the present invention when viewed obliquely.

FIG. 14 is a longitudinal sectional view in the longitudinal direction showing the configuration of a semiconductor laser device according to a sixth embodiment of the present invention.

15 is a sectional view of the semiconductor laser device shown in FIG. 14 taken along the line AA.

16 is a diagram showing a relationship between an oscillation wavelength spectrum and an oscillation longitudinal mode of the semiconductor laser device shown in FIG.

FIG. 17 is a diagram showing a relationship between laser light output powers in a single-oscillation longitudinal mode and a plurality of oscillation longitudinal modes and a threshold value for stimulated Brillouin scattering.

FIG. 18 is a diagram showing IL characteristics of a semiconductor laser device according to a sixth embodiment of the present invention.

FIG. 19 is a diagram showing the wavelength dependence of the oscillation threshold gain difference with the separation distance from the exit side end face of the diffraction grating as a parameter.

FIG. 20 is a diagram showing the wavelength dependence of the front-to-rear end face ratio of the light output with the distance from the end face on the exit side of the diffraction grating as a parameter.

21 is a plan view of a semiconductor wafer on which the semiconductor laser device shown in FIG. 13 is formed.

22 is a sectional view of the semiconductor wafer shown in FIG. 21. FIG.

FIG. 23 is a diagram showing a configuration of a chirped grating applied to a diffraction grating.

FIG. 24 is a diagram showing an oscillation wavelength spectrum when a chirped grating is applied to a diffraction grating.

FIG. 25 is a diagram showing a modified example of a grating having periodic fluctuation.

FIG. 26 is a vertical sectional view showing a structure of a semiconductor laser module according to a seventh embodiment of the present invention.

FIG. 27 is a block diagram showing the configuration of a Raman amplifier that is Embodiment 8 of the present invention.

28 is a block diagram showing an application example of the Raman amplifier shown in FIG. 27.

FIG. 29 is a block diagram showing a modification of the Raman amplifier shown in FIG. 27 and showing a configuration of a Raman amplifier adopting a forward pumping method.

30 is a block diagram showing an application example of the Raman amplifier shown in FIG. 29. FIG.

FIG. 31 is a block diagram showing a modification of the Raman amplifier shown in FIG. 27 and showing a configuration of a Raman amplifier adopting a bidirectional pumping method.

FIG. 32 is a block diagram showing an application example of the Raman amplifier shown in FIG. 31.

FIG. 33 is a block diagram showing a schematic configuration of a WDM communication system using the Raman amplifier shown in FIGS. 27 to 32.

FIG. 34 is a longitudinal cross-sectional view in the longitudinal direction of the semiconductor laser device according to the ninth embodiment.

35 is a sectional view taken along the line AA of the semiconductor laser device shown in FIG.

FIG. 36 is a diagram showing a graph for explaining selective wavelength characteristics by the diffraction grating of the semiconductor laser device according to the ninth embodiment.

FIG. 37 is an explanatory diagram for explaining each profile of laser light of a single longitudinal mode and laser light of a plurality of oscillation longitudinal modes in the semiconductor laser device according to the ninth embodiment.

FIG. 38 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the tenth embodiment.

FIG. 39 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the eleventh embodiment.

FIG. 40 is a vertical sectional view showing the structure of the semiconductor laser module according to the twelfth embodiment.

FIG. 41 is an explanatory diagram for explaining a case where the semiconductor laser module according to the twelfth embodiment is used in an HPU used in a Raman amplifier or EDFA.

FIG. 42 is a block diagram showing a schematic configuration of a conventional Raman amplifier.

FIG. 43 is a diagram showing a configuration of a semiconductor laser module used in a conventional Raman amplifier.

FIG. 44 is a block diagram showing a schematic configuration of a conventional Raman amplifier.

FIG. 45 is a diagram showing a configuration example of an HPU of a conventional Raman amplifier.

[Explanation of symbols]

1 n-InP substrate 2 n-InP cladding layer 3 GRIN-SCH-MQW active layer 4 p-InP spacer layer 6 p-InP cladding layer 8 p-InGaAsP contact layer 9a n-InP blocking layer 9b p-InP blocking layer 10 p-side electrode 11 n-side electrodes 13a, 13b diffraction grating 14 high reflection film 15 low reflection film 16 insulating film 20 oscillation wavelength spectra 21, 22, 23 oscillation longitudinal mode 24 composite oscillation wavelength spectrum 1001 n-InP substrate 1002 n-Inp buffer Layer 1003 GRIN-SCH-MQW active layer 1004 p-InP spacer layer 1006 p-InP clad layer 1007 p-InGaAsP contact layer 1008 p-InP blocking layer 1009 n-InP blocking layer 1010 p-side electrode 1011 n-side electrode 1013 diffraction Lattice 1014 Reflective film 1015 Emission side reflective film 1020 Semiconductor laser device 1030 Oscillation wavelength spectrum 1031 to 1033 Oscillation longitudinal mode 1045 Composite oscillation wavelength spectrum 1050, 1060a to 1060d, 1060a 'to 1
060d ′ Semiconductor laser module 1052 First lens 1053, 1063, 1066 Isolator 1054 Second lens 1055 Optical fiber 1056 Current monitor 1057 Base 1057a Heat sink 1058 Peltier element 1058a Thermistor 1059 Package 1061a, 1061b, 1061a ′, 1061b ′
Polarization combiner 1062, 1065, 1062 ', 1065' WDM
Coupler 1064 Amplifying fiber 1067 Monitor light distributing coupler 1068 Control circuit 1069 Signal light input fiber 1070 Signal light output fiber 1071 Polarization plane maintaining fibers 1081 and 1083 Raman amplifier Ls Separation distance Lg Diffraction grating length W Semiconductor wafer 2001 n-InP substrate 2002 , 2002a, 2002c n-InP buffer layer 2002b n-InP clad layer 2003a compressive strain GRIN-SCH-MQW active layer 2003b tensile strain GRIN-SCH-MQW active layer 2004, 2004a, 2004b p-InP spacer layer 2005 tunnel junction layer 2006 , 2006a, 2006b p-InP clad layer 2007, 2007a, 2007b p-InGaAs
P cap layer 2008 p-InP blocking layer 2009 n-InP blocking layers 2010, 2010a, 2010b p-side electrode 2011 n-side electrodes 2013, 2013a, 2013b Diffraction grating 2014 Reflective film 2015 Emission-side reflective film 2022 Separation grooves 2080, 2080a to 2080f Semiconductor laser module 2081 Package 2082 Optical fiber 2083 Optical monitor 2084 First lens 2085 Isolator 2086 Second lens 2090 Semiconductor laser device 2092 Base 2094 Peltier device 2130 HPU 2131 WDM coupler

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Irino             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. F-term (reference) 5F072 AB07 AK06 JJ05 JJ20 KK30                       PP07 QQ07 RR01 YY17                 5F073 AA22 AA46 AA65 AA74 AA83                       AA87 AB27 AB28 AB30 BA03                       CA07 CB10 CB22 EA01 EA15                       EA22 FA02 FA25 GA38

Claims (28)

[Claims] 1. A semiconductor substrate of a first conductivity type, a semiconductor buffer layer of a first conductivity type stacked on the semiconductor substrate, an active layer stacked on the semiconductor buffer layer, and an active layer on the active layer. A semiconductor laser device having a laminated first electrode and a second electrode disposed on the lower surface of the semiconductor substrate, comprising: a second conductive type spacer layer laminated on the active layer; A diffraction grating arranged in a partial region of a spacer layer of the mold for selecting laser light having a plurality of oscillation longitudinal modes having a specific center wavelength, and a non-injection current that does not flow into a part of the diffraction grating. A semiconductor laser device comprising: a current injection region; 2. An insulating film disposed on a partial region above the diffraction grating, the presence of the insulating film preventing an inflow of an injection current to a part of the diffraction grating. The semiconductor laser device according to claim 1, which is characterized in that. 3. A first conductivity type semiconductor substrate, a first conductivity type semiconductor buffer layer stacked on the semiconductor substrate, an active layer stacked on the semiconductor buffer layer, and an active layer on the active layer. A semiconductor laser device having a laminated first electrode and a second electrode disposed on the lower surface of the semiconductor substrate, comprising: a second conductive type spacer layer laminated on the active layer; A diffraction grating which is arranged in a partial region of a spacer layer of a mold and which selects a laser beam having a plurality of oscillation longitudinal modes having a specific center wavelength, and the first electrode is one of the diffraction gratings. A first portion arranged in a region corresponding to a portion of the portion, and a second portion arranged in a region corresponding to a portion where the diffraction grating does not exist, the first portion and the second portion Is separated spatially or electrically from And a semiconductor laser device. 4. The first electrode further has a third portion arranged in a region corresponding to the other portion of the diffraction grating, the third portion including the first portion and the third portion. The semiconductor laser device according to claim 3, wherein the semiconductor laser device is spatially separated from the second portion. 5. A clad layer of a first conductivity type laminated between the semiconductor buffer layer of the first conductivity type and the active layer, a spacer layer of the second conductivity type, and the first electrode. The semiconductor laser device according to claim 1, further comprising: a second conductive type clad layer laminated between the two. 6. The semiconductor laser device according to claim 1, a temperature control module for controlling the temperature of the semiconductor laser device, and a laser beam emitted from the semiconductor laser device to the outside. A semiconductor laser module comprising: an optical fiber that guides light; a semiconductor laser device; and an optical coupling lens system that optically couples with the optical fiber. 7. The photodetector for measuring the optical output of the semiconductor laser device, and an isolator for suppressing the incidence of reflected return light from the optical fiber side, further comprising: Semiconductor laser module. 8. A pumping light source using the semiconductor laser device according to claim 1 or the semiconductor laser module according to claim 6 or 7, and combining the signal light and the pumping light. An optical fiber amplifier comprising a coupler for amplification and an amplification optical fiber. 9. The optical fiber amplifier according to claim 8, wherein the amplification optical fiber amplifies light by Raman amplification. 10. A diffraction partly provided in the vicinity of an active layer formed between a first reflection film provided on a laser light emission end face and a second reflection film provided on the laser light reflection end face. In a semiconductor laser device having a grating and outputting a laser beam having a desired oscillation longitudinal mode by at least the wavelength selection characteristic of the diffraction grating, the diffraction grating is provided in the vicinity of the first reflection film, and the first reflection film is provided. A semiconductor laser device characterized in that it is formed so as to be separated from the film by 50 μm or less. 11. The semiconductor laser device according to claim 10, wherein a separation distance between the diffraction grating and the first reflective film is in a range of 10 to 20 μm. 12. The semiconductor laser device according to claim 10, wherein the desired number of oscillation longitudinal modes is two or more within a half width of an oscillation wavelength spectrum. 13. The diffraction grating has a diffraction grating length of 300.
13. The semiconductor laser device according to claim 10, wherein the semiconductor laser device has a thickness of μm or less. 14. The semiconductor laser according to claim 10, wherein a diffraction grating length of the diffraction grating is equal to or less than a value of (300/1300) times the cavity length. apparatus. 15. The semiconductor according to claim 10, wherein a multiplication value of a coupling coefficient of the diffraction grating and a diffraction grating length of the diffraction grating is 0.3 or less. Laser device. 16. The semiconductor laser device according to claim 10, wherein the diffraction grating has a grating cycle changed randomly or in a predetermined cycle. 17. The resonator formed by an active layer formed between the first reflective film and the second reflective film has a length of 800 μm or more.
16. The semiconductor laser device according to any one of 16 to 16. 18. The semiconductor laser device according to claim 10, an optical fiber that guides laser light emitted from the semiconductor laser device to the outside, the semiconductor laser device, and the light. A semiconductor laser module comprising: an optical coupling lens system for optically coupling with a fiber. 19. A temperature control device for controlling the temperature of the semiconductor laser device, and an isolator arranged in the optical coupling lens system for suppressing incidence of reflected return light from the optical fiber side. The semiconductor laser module according to claim 18, wherein: 20. The semiconductor laser device according to any one of claims 1 to 8 or the semiconductor laser module according to claim 18 or 19 is used as an excitation light source for wideband Raman amplification. Optical fiber amplifier. 21. The semiconductor laser device according to claim 10, or claim 18 or 19.
2. The optical fiber amplifier according to claim 1, wherein the semiconductor laser module is a pumping light source for broadband Raman amplification and is used as a forward pumping light source or a forward pumping light source in a bidirectional pumping system. 22. A compressive strain quantum well active layer, a tensile strain quantum well active layer, a laser light emitting end face and a reflecting end face, and the compressive strain quantum well active layer and / or the tensile strain quantum well. A diffraction grating formed in the vicinity of the well active layer, and a TE mode laser beam generated in the compressive strain quantum well active layer and a T mode generated in the tensile strain quantum well active layer.
A semiconductor laser device which is a laser beam obtained by polarization-combining an M-mode laser beam and outputs a plurality of oscillation longitudinal mode laser beams having a predetermined output value or less depending on the wavelength selection characteristics of the diffraction grating. . 23. The compressive strain quantum well active layer and the tensile strain quantum well active layer are vertically stacked, and one of clad layers sandwiching the compressive strain quantum well active layer,
23. The semiconductor laser device according to claim 22, wherein a tunnel junction layer is formed between the tensile junction quantum well active layer and one of the cladding layers sandwiching the tensile strain quantum well active layer. 24. The semiconductor laser device according to claim 22, wherein the compressive strained quantum well active layer and the tensile strained quantum well active layer are stacked vertically adjacent to each other. 25. The semiconductor laser device according to claim 22, wherein the compressive strained quantum well active layer and the tensile strained quantum well active layer are butt-joined to each other in the laser beam emitting direction. 26. At least one electrode of an electrode pair for applying a current to the compressive strain quantum well active layer, and at least one electrode of an electrode pair for applying a current to the tensile strain quantum well active layer. 26. The semiconductor laser device according to claim 25, wherein is electrically isolated by an isolation groove formed above a coupling boundary between the compressive strained quantum well active layer and the tensile strained quantum well active layer. . 27. The semiconductor laser device according to claim 22, an optical fiber that guides laser light emitted from the semiconductor laser device to the outside, the semiconductor laser device, and the light. A semiconductor laser module comprising: an optical coupling lens system for optically coupling with a fiber. 28. A pump light source for outputting pump light obtained by multiplexing a plurality of laser lights having different oscillation center wavelengths, and a desired amplification determined by the pump light for signal light propagating on a transmission line. An optical fiber amplifier that performs amplification with a band and a desired gain, wherein the pumping light source includes the semiconductor laser module according to claim 27.