JP2003086887A - Semiconductor laser device, semiconductor laser module, and optical fiber amplifier using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain induction Brillouin scattering from occurring and to enable exciting light of high power to impinge on an optical fiber. SOLUTION: A semiconductor laser device 21 is equipped with a Fabry-Perot resonator formed of a GRIN-SCH-MQW active layer 3 provided between an output-side reflecting film 15 provided on the laser ray projection end face and a laser ray reflecting film 14 provided on the reflecting end face and outputs laser rays at least in a plurality of oscillation vertical modes. A non-current injection region E1 which restrains a current from being injected into a certain region of the GRIN-SCH-MQW active layer 3 is provided so as to form a supersaturated absorption region E10.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an erbium-doped fiber amplifier (EDFA).
The present invention relates to a semiconductor laser device, a semiconductor laser module, and an optical fiber amplifier using the semiconductor laser device, which are suitable for a pumping light source such as ier) or Raman amplifier.

[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 has been put to practical use from 1550 nm, which is easy to flatten the gain, and has recently been expanded to the 1580 nm band which has not been used because of its small gain coefficient. . However, since the low-loss band of the optical fiber is wider than the band that can be amplified by the EDFA, there is an increasing interest in optical amplifiers that operate outside the band of the EDFA, that is, Raman amplifiers.

The Raman amplifier is characterized in that the gain wavelength band is determined by the wavelength of the pump light, whereas the gain wavelength band is determined by the energy level of the ion in an optical amplifier using a rare earth ion such as erbium as a medium. An arbitrary wavelength band can be amplified by selecting the pumping 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. 31 is a block diagram showing the configuration of a conventional Raman amplifier used in a WDM communication system.
In FIG. 31, the Fabry-Perot type semiconductor light emitting device 1 is shown.
80a to 180d and fiber grating 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. 32 is a diagram showing a schematic structure of a semiconductor laser module using a fiber grating.
In FIG. 32, this semiconductor laser module 201
Has a semiconductor light emitting element 202 and an optical fiber 203. The semiconductor light emitting device 202 has an active layer 221.
The active layer 221 has a light reflecting surface 222 at one end and a light emitting surface 223 at the other end. The light generated in the active layer 221 is reflected by the light reflecting surface 222, and the light emitting surface 223
Is output from.

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 grating 2 at a predetermined position from the light emitting surface 223.
33 is formed, and the fiber grating 233 selectively reflects light having a characteristic wavelength. That is, the fiber grating 233 functions as an external resonator, forms a resonator between the fiber grating 233 and the light reflecting surface 222, and a laser beam of a specific wavelength selected by the fiber grating 233 is amplified to output laser light. It is output as light 241.

[0013]

However, the above-mentioned semiconductor laser module 201 (182a to 182) is used.
In d), since the distance between the fiber grating 233 and the semiconductor light emitting element 202 is long, the resonance between the fiber grating 233 and the light reflecting surface 222 causes a relative intensity noise (RIN) to increase. 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.

Here, as the Raman amplifier, in addition to the backward pumping method that pumps the signal light from the rear like the Raman amplifier shown in FIG. 31, there is a forward pumping method that pumps the signal light from the front and There is a bidirectional excitation method that excites from both directions. 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 grating is used, there is a problem that the applicable pumping method is limited.

Further, the semiconductor laser module 2 described above
01 is required to optically couple the optical fiber 203 having the fiber grating 233 and the semiconductor light emitting element 202, and since it is mechanical optical coupling in the resonator, the oscillation characteristic of the laser is mechanical vibration or the like. However, there is a problem in that stable excitation light may not be provided in some cases.

Further, the 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,
Since the amplification gain has polarization dependency, 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 depolarizing. That is, the degree of polarization (DOP: Degree Of Po)
larization) needs to be small.

Since Raman amplification and the like are used in the WDM communication system, the amplification gain characteristic may be changed depending on the number of wavelengths of the input signal light, and for this reason, a high dynamic range with a wide dynamic range is obtained. Output operation is required. However, in this case, a slight fluctuation actually occurs in the drive current dependency of the monitor current, and there is a problem that stable optical amplification control becomes complicated or difficult. The monitor current is a current obtained when the light output leaked from the rear end of the semiconductor laser device is received by the photodiode (PD).

For example, FIG. 33 shows the monitor current (Im).
It is a figure which shows the optical output (Lo) dependence of. FIG. 33 (a)
According to the optical output dependence of the monitor current shown in (1), when the optical output exceeds a certain optical output, a wave is generated as the optical output increases, and wobble occurs. In this case, since the optical amplification control of the semiconductor laser device is performed based on the monitor current, the correspondence with the optical output becomes complicated, and as a result, the optical amplification control becomes complicated. On the other hand, in the light output dependency of the monitor current shown in FIG. 33B, when the light output exceeds a certain light output, the monitor current increases stepwise as the light output increases. In this case, the optical amplification control of the semiconductor laser device is performed based on the monitor current, and thus becomes unstable.

By the way, with the increase in the output of the semiconductor laser device constituting the pumping light source, new problems have arisen. The excitation light emitted from the excitation light source enters the optical fiber for transmission amplification through the optical fiber, but when light having an intensity higher than a certain threshold enters the optical fiber, stimulated Brillouin scattering occurs. Stimulated Brillouin scattering is a nonlinear optical phenomenon in which incident light interacts with an acoustic wave (phonon) to cause scattering (reflection). It is observed as a phenomenon in which light having a frequency lower by about 11 GHz is reflected in the direction opposite to the incident light due to the loss of phonon energy.

In the optical fiber amplifier using the Raman amplification, when the stimulated Brillouin scattering of the excitation light occurs as described above, a part of the incident excitation light is reflected backward. Therefore, it does not contribute to Raman gain generation. In addition, this scattered light may generate unintended noise. This decrease in pumping light intensity does not pose a problem when the pumping light transmission distance is short. However, in the above-described optical fiber amplifier using the remote pump, since it is necessary to transmit the pumping light over a long distance before reaching the amplification optical fiber from the pumping light source, the decrease in the light intensity cannot be ignored. In the case of an optical fiber amplifier using a remote pump, the intensity of the pumping light is reduced at a rate higher than the optical loss in a normal optical fiber, so that the amplification gain is reduced in the amplification optical fiber. Occurs.

In order to solve the above-mentioned problems of the prior art, the present invention suppresses the occurrence of stimulated Brillouin scattering and allows high-power pumping light to be incident on an optical fiber, a semiconductor laser module. Another object of the present invention is to provide an optical fiber amplifier using the same.

[0022]

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 in which a first reflecting film is provided on a laser light emitting end face and a second reflecting film is provided on the laser light reflecting end face. A semiconductor laser device which has a diffraction grating partially provided in the vicinity of an active layer formed between the reflection film and a laser and outputs a laser beam having a desired oscillation longitudinal mode by at least the wavelength selection characteristic of the diffraction grating. In the above, the non-current injection region is formed to suppress the injection current into a partial region of the active layer except the active layer near the diffraction grating.

According to the invention of claim 1, the vicinity of 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. Of the active layer excluding the active layer in the vicinity of the diffraction grating when outputting laser light having a desired oscillation longitudinal mode by at least the wavelength selection characteristic of the diffraction grating. A non-current injection region that suppresses an injection current to a partial region is formed. The non-current injection region absorbs the light emitted in the current injection region and generates carriers. When light is absorbed until a population inversion occurs, stimulated emission occurs in this region, light absorption in this region does not occur, and it acts as a supersaturated absorption layer that is transparent to oscillation light. Therefore, a partial region of the active layer is set to a supersaturated absorption region, and the photon lifetime is reduced by light absorption in the supersaturated absorption region to increase the spectral line width.

According to a second aspect of 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 that forms a Fabry-Perot resonator by using a laser diode and outputs a laser beam having at least a plurality of oscillation longitudinal modes, a non-current injection region that suppresses an injection current to a partial region of the active layer is formed. Characterize.

According to the second aspect of the present invention, the fabric is formed by 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. When a Perot resonator is formed and laser light having at least a plurality of oscillation longitudinal modes is output, a non-current injection region that suppresses an injection current into a partial region of the active layer is formed,
Part of the active layer is made into a supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region to increase the spectral line width.

Further, a semiconductor laser device according to a third aspect of the present invention is characterized in that, in the above-mentioned invention, the non-current injection region is formed by an insulating film covering an upper portion of a partial region of the active layer.

According to the third aspect of the present invention, the non-current injection region is formed by the insulating film covering the partial region of the active layer, and the active layer in the non-current injection region is made into the supersaturation absorption region. The spectral line width is increased by reducing the photon lifetime in the supersaturated absorption region.

Further, a semiconductor laser device according to a fourth aspect is characterized in that, in the above invention, the electrode to which the injection current is applied is provided except at least an upper surface of a partial region of the active layer.

According to the invention of claim 4, the electrode to which the injection current is applied is provided except at least the upper surface of the partial region of the active layer, and the partial region of the active layer is used as a supersaturation absorption region, By reducing the photon lifetime in this supersaturated absorption region, the spectral line width is increased.

According to a fifth aspect of the present invention, in the semiconductor laser device according to the above invention, the contact resistance of the injection current is provided between the upper cladding layer for confining light in the active layer and the electrode for applying the injection current. It is characterized in that a contact layer to be reduced is provided except at least an upper surface of a partial region of the active layer.

According to the fifth aspect of the present invention, at least a contact layer provided between the upper clad layer for confining light in the active layer and the electrode for applying the injection current to reduce the contact resistance of the injection current is formed. Provided except the upper surface of a partial region of the active layer, the partial region of the active layer is made into a supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region so that the spectral line width is increased. ing.

According to a sixth aspect of the present invention, in the semiconductor laser device according to the above-mentioned invention, a portion of the active layer between the upper clad layer for confining light in the active layer and the electrode for applying the injection current is formed. A current blocking layer for forming a diode junction that blocks a current flowing from the electrode toward the partial region of the active layer with respect to the upper cladding layer, at a position corresponding to an upper portion of the partial region. To do.

According to the invention of claim 6, it is between the upper clad layer for confining light in the active layer and the electrode for applying the injection current, and corresponds to the upper part of the partial region of the active layer. A current blocking layer for forming a diode junction that blocks a current flowing from the electrode toward the partial region of the active layer with respect to the upper cladding layer is provided at a position, and the partial region of the active layer is used as a supersaturation absorption region. In this supersaturation absorption region, the photon lifetime is reduced to increase the spectral line width.

According to a seventh aspect of the present invention, in the semiconductor laser device according to the above invention, a portion of the active layer between the upper clad layer for confining light in the active layer and the electrode for applying the injection current is formed. A high contact resistance layer formed of a material having a high contact resistance to the electrode is provided at a position corresponding to an upper portion of the partial region.

According to the invention of claim 7, it is between the upper cladding layer for confining light in the active layer and the electrode for applying the injection current, and corresponds to the upper part of the partial region of the active layer. A high contact resistance layer made of a material having a high contact resistance to the electrode is provided at a position, and a partial region of this active layer is made into a supersaturation absorption region, and the photon lifetime is reduced in this supersaturation absorption region. By doing so, the spectral line width is increased.

According to an eighth aspect of the present invention, in the semiconductor laser device according to the above-mentioned invention, the contact layer formed on the upper surface of the upper clad layer for confining light in the active layer is formed,
The first contact layer corresponding to the upper part of the partial area of the active layer and the second contact layer not corresponding to the upper part of the partial area of the active layer are spatially separated from each other, and the upper surface of the first contact layer and the The groove formed by the separation is covered with an insulating film or a current blocking layer, and the electrode is formed on the entire upper surface of the second contact layer and the insulating film or the current blocking layer.

According to the invention of claim 8, the contact layer formed on the upper surface of the upper clad layer for confining light in the active layer is the first contact layer corresponding to the upper part of the partial region of the active layer. And a second contact layer that does not correspond to an upper part of the active layer in a partial area, and the upper surface of the first contact layer and the groove formed by the separation are covered with an insulating film or a current blocking layer, The electrode is formed on the entire upper surface of the second contact layer and the insulating film or the current blocking layer, and a partial region of the active layer is made into a supersaturation absorption region, and a photon lifetime is reduced in the supersaturation absorption region. To increase the spectral line width.

According to a ninth aspect of the present invention, in the semiconductor laser device according to the above-mentioned invention, the contact layer formed on the upper surface of the upper clad layer for confining light in the active layer is formed,
The first contact layer corresponding to the upper part of the partial area of the active layer and the second contact layer not corresponding to the upper part of the partial area of the active layer are spatially separated, and the first contact layer and the second contact layer are separated from each other. It is characterized in that electrodes are formed on the upper surface of the contact layer.

According to the invention of claim 9, the contact layer formed on the upper surface of the upper clad layer for confining light in the active layer is the first contact layer corresponding to the upper part of the partial region of the active layer. And a second contact layer which does not correspond to an upper portion of a part of the active layer, are spatially separated, and electrodes are formed on the upper surfaces of the first contact layer and the second contact layer, respectively. Part of the region is made into a supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region to increase the spectral line width.

According to a tenth aspect of the present invention, in the semiconductor laser device according to the above-mentioned invention, the carrier concentration of the region located on the upper surface of a partial region of the active layer of the cladding layer and / or the first contact layer. Is smaller than the carrier concentration of the cladding layer.

According to the tenth aspect of the present invention, the carrier concentration of the region of the clad layer located on the upper surface of the partial region of the active layer and / or the first contact layer is the carrier concentration of the clad layer. It is made smaller than the concentration, and a partial region of this active layer is made into a supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region to increase the spectral line width.

Further, in the semiconductor laser device according to an eleventh aspect of the present invention, in the above invention, a region of the clad layer located on an upper surface of a partial region of the active layer and / or the first contact layer is formed of a proton. It is characterized in that the resistance is increased by irradiation.

According to the eleventh aspect of the present invention, the region of the cladding layer located on the upper surface of the partial region of the active layer and / or the first contact layer has a high resistance due to proton irradiation. Part of the active layer is made into a supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region to increase the spectral line width.

According to a twelfth aspect of the present invention, in the semiconductor laser device according to the above invention, the region located on the upper surface of the partial region of the active layer in the cladding layer and / or the first contact layer is n. A current blocking layer is formed on the cladding layer by adding and diffusing a type impurity.

According to the twelfth aspect of the present invention, the region of the cladding layer located on the upper surface of the partial region of the active layer and / or the first contact layer is formed by adding and diffusing an n-type impurity. A current blocking layer is formed on the cladding layer, a partial region of this active layer is made into a supersaturation absorption region, and the photon lifetime is reduced in this supersaturation absorption region to increase the spectral line width. There is.

According to a thirteenth aspect of the present invention, in the semiconductor laser device according to the above invention, the diffraction grating is the first
It is characterized in that it is provided on the reflective film side or in the vicinity of the first reflective film.

According to a fourteenth aspect of the present invention, in the semiconductor laser device according to the above invention, the diffraction grating is the second laser diode.
It is characterized in that it is provided on the reflective film side or in the vicinity of the second reflective film.

According to a fifteenth aspect of the present invention, in the semiconductor laser device according to the above invention, the diffraction grating is the first
It is characterized in that it is provided on the reflection film side or in the vicinity of the first reflection film and on the second reflection film side or in the vicinity of the second reflection film.

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

According to a seventeenth 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.

Further, a semiconductor laser device according to an eighteenth aspect of the present invention is characterized in that, in the above invention, the diffraction grating length of the diffraction grating is not more than (300/1300) times the resonator length. .

According to a nineteenth 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 a twentieth 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 a twenty-first 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.

A semiconductor laser module according to claim 22 is the semiconductor laser device according to any one of claims 1 to 21, an optical fiber for guiding the laser light emitted from the semiconductor laser device to the outside, and the semiconductor. It is characterized by comprising a laser device and an optical coupling lens system for optically coupling the optical fiber.

According to a twenty-third aspect of the 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, and reflection from the optical fiber side is performed. It is characterized by further comprising an isolator for suppressing the incidence of return light.

A semiconductor laser module according to a twenty-fourth aspect of the present invention is characterized in that, in the above invention, an optical fiber grating for wavelength selection is connected to the output side of the optical fiber.

An optical fiber amplifier according to a twenty-fifth aspect of the invention is a semiconductor laser module according to any one of the twenty-second to twenty-fourth aspects, an amplification optical fiber, and pumping light output from the semiconductor laser module. And a coupler for multiplexing the signal light propagating in the amplification optical fiber.

According to a twenty-sixth aspect of the present invention, in the above invention, the amplification optical fiber is
It is characterized in that the signal light is amplified by Raman amplification.

An optical fiber amplifier according to a twenty-seventh aspect of the present invention is the above-mentioned invention, wherein the amplification optical fiber is
It is an erbium-doped fiber, and the semiconductor laser module and the amplification optical fiber are arranged remotely.

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a semiconductor laser device, a semiconductor laser module and an optical fiber amplifier using the same according to the present invention will be described below with reference to the accompanying drawings.

(Embodiment 1) First, Embodiment 1 of the present invention will be described. 1 is a longitudinal sectional view in the longitudinal direction of a semiconductor laser device according to a first embodiment of the present invention. Further, FIG. 2 shows the semiconductor laser device A shown in FIG.
FIG. In FIG. 1 and FIG. 2, this semiconductor laser device 20 comprises a (100) n-InP substrate 1.
N-InP clad layer 2 also serving as a buffer layer and a lower clad layer made of n-InP on the surface, and GRIN-SCH-MQW (Graded Index-Separat) having compressive strain.
e Confinement Heterostructure Multi Quantum Well)
The active layer 3, the p-InP spacer layer 4, the p-InP clad layer 6, and the InGaAsP contact layer 7 are laminated.

A film thickness of 20 is formed in the p-InP spacer layer 4.
nm, the length Lg from the emitting side reflection film 15 toward the reflection film 14 side is 50 μm, and the coupling coefficient κ is 25 cm ⁻¹ (κL
= 0.125), and the diffraction grating 13 is periodically formed with a pitch of about 220 nm and wavelength-selects a laser beam having a center wavelength of 1.48 μm. The p-InP spacer layer 4 including the diffraction grating 13, the GRIN-SCH-MQW active layer 3 having compressive strain, and the n-I.
The upper portion of the nP buffer layer 2 is processed into a mesa stripe shape, and the p-InP blocking layer 9 formed as a current blocking layer is formed on both sides of the mesa stripe in the longitudinal direction.
b and the n-InP blocking layer 9a. This current blocking layer is GRIN-SC
This structure is effective not only for efficiently injecting current into the H-MQW active layer 3 but also for realizing a stable horizontal single transverse mode.

60 μm on the upper surface of the InGaAsP contact layer 7 from the reflection film 15 on the emission side toward the reflection film 14.
The insulating film 8 is formed up to m. The insulating film 8 is made of SiN. It is preferable that the insulating film 8 has good thermal conductivity. In addition, AlN, Al
_It may be made of ₂ O ₃ , MgO, TiO _2, or the like.
Further, the insulating film 8 may have a stripe shape having a width exceeding the width of the mesa stripe structure because it is sufficient that current is not injected into the mesa stripe structure below the insulating film 8.

The p-InGaAsP contact layer 7 in the upper surface of the insulating film 8 and in the region other than the region covered with the insulating film 8
A p-side electrode 10 is formed on the upper surface of the. It is desirable that a bonding pad (not shown) be formed on the p-side electrode 10. The thickness of this bonding pad is
It is desirable to set the thickness to about 5 μm. For example, when assembling a semiconductor laser device by a junction down method, this bonding pad functions as a cushioning material for cushioning the shock at the time of assembly by this thickness, and this thickness also serves as a heat sink. It is possible to prevent the solder from wrapping around at the time of joining and to prevent a short circuit due to the wraparound of the solder (see FIGS. 13 and 14). On the other hand, n
An n-side electrode 11 is formed on the back surface of the -InP substrate 1. Each semiconductor laser device in which the p-side electrode 10 and the n-side electrode 11 are formed on a semiconductor wafer is separated by cleavage.

After that, a reflection film 14 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 20, and the other end surface is formed. An emission side reflection film 15 having a low light reflectance of 2% or less, preferably 0.1% or less is formed on a certain light emitting end face. Reflection film 14 and emission side reflection film 1
GRIN-SCH- of the optical resonator formed by
The light generated in the MQW active layer 3 is reflected by the reflection film 14 and emitted as laser light through the emission-side reflection film 15. At this time, the wavelength is selected by the diffraction grating 13 and emitted.

The semiconductor laser device 20 according to the first embodiment is premised on being used as a pumping light source for a Raman amplifier, and its oscillation wavelength λ0 is 1100 nm to
1550 nm, and the resonator length L is 800 μm or more 3
It is set to 200 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 = λ02 / (2 · n · L). Here, when the oscillation wavelength λ0 is 1480 μm 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 grating 13 selects the longitudinal mode according to its Bragg wavelength. The selected wavelength characteristic by the diffraction grating 13 is represented as an oscillation wavelength spectrum 30 shown in FIG.

As shown in FIG. 3, in the first embodiment, a plurality of oscillation longitudinal modes are included in the wavelength selection characteristic represented by the half-width Δλh of the oscillation wavelength spectrum 30 by the semiconductor laser device 20 having the diffraction grating 13. I try to make it exist. Conventional DBR (Distributed Feedback) semiconductor laser device or DFB (Distributed Bragg Reflre)
ctor) In the semiconductor laser device, the cavity length L is 800 μm.
In the above case, since it was difficult to oscillate in the single longitudinal mode,
A semiconductor laser device having such a cavity length L was not used. However, in the semiconductor laser device 20 of the first embodiment, the half-width Δ of the oscillation wavelength spectrum is set by positively setting the cavity length L to 800 μm or more.
A plurality of oscillation longitudinal modes are included in λh for laser output. In FIG. 3, there are three oscillation longitudinal modes 31 to 33 within the half width Δλh of the oscillation wavelength spectrum.

When a laser beam 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 a laser beam having a 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 between the oscillation longitudinal modes 31 to 33 is set to 0.1 nm or more. This is because, when the semiconductor laser device 20 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 30 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 the two semiconductor laser devices 20, a polarization maintaining fiber having a predetermined length as a depolarizer is used. Is used to propagate the laser light emitted from one semiconductor laser device 20 to the 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, in the case where the laser light emitted from the semiconductor laser device 20 is depolarized for use in the Raman amplifier, the emitted lights of the two semiconductor laser devices are not polarization-synthesized and used by one unit. Since it becomes easy to depolarize the laser light emitted from the semiconductor laser device 20 and to 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 full width at half maximum Δλh of the oscillation wavelength spectrum 30 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. 32, 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 20 shown in the first embodiment, the laser light emitted from the emitting side reflection film 15 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. 32 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 first embodiment,
A stable optical output can be obtained without changing the oscillation characteristics of the laser due to mechanical vibration or the like.

By the way, in the first embodiment, the InGaAsP contact layer 7 is located above the diffraction grating 13.
The insulating film 8 having a length of Li = 60 μm is formed between the emission side reflection film 15 and the reflection film 14 between the p-side electrode 10 and the p-side electrode 10. Therefore, the injection current applied from the p-side electrode 10 to the n-side electrode 11 flows in the current injection region E2 below the region not covered with the insulating film 8 and the insulating film 8
The inflow to the non-current injection region E1 below which is covered by the is suppressed.

By suppressing the injection current in the vicinity of the diffraction grating 13 in the non-current injection region E1, as shown in FIG. 5, the optical output of the monitor current leaked from the rear end of the semiconductor laser device 20, that is, the reflection film 14 side. Fine fluctuations in dependence are reduced, optical amplification control becomes simple and easy, and as a result, stable optical output can be easily obtained. As a result, the semiconductor laser device 20 shown in the first embodiment
When used as a pumping light source for a Raman amplifier, amplification control becomes easy. In particular, in a high-power semiconductor laser device of about 300 mW or more, especially 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, the monitor current does not fluctuate slightly, and the optical amplification control becomes simple and easy. Incidentally, in the conventional semiconductor laser device in which the non-current injection region is not formed, the semiconductor laser device having the optical output dependency of the monitor current shown in FIG. 5 can be obtained by only about 20%. By forming the non-current injection region shown in the first embodiment, about 70% of the semiconductor laser device having the optical output dependence of the monitor current shown in FIG. 5 could be obtained.

The GRIN-SCH-MQW active layer 3
At the end surface of the exit side reflection film 15 of COD (Catastrophic O
ptical damage) is likely to occur. COD is GRIN
At the end face of the emitting side reflection film 15 of the -SCH-MQW active layer 3, a feedback cycle occurs in which the end face temperature rises → the band gap decreases → the light absorption → the recombination current → the end face temperature rises, and this cycle is called positive feedback. This is a phenomenon in which the end face melts and deteriorates in an instant. By the way, in the first embodiment, since the end surface of the emitting side reflection film 15 is in the non-current injection region E1, it is expected that the injection current is suppressed and the generation probability of COD is reduced by suppressing the heat generation. Here, in the InP-based semiconductor laser device, COD is less likely to occur than in the GaAs-based semiconductor laser device.
In a high-power semiconductor laser device of about 300 mW or more, even if it is an InP system, the temperature rise of the end face becomes large, and COD is likely to occur.

The GRIN-SC in the current injection region E2 is
The H-MQW active layer 3 emits light by an injection current, while the GRIN-SCH-MQW active layer 3 in the non-current injection region E1 is GRIN-SCH-MQ in the current injection region E2.
Since the photon recycling is performed by the light from the W active layer 3, it functions as a buffer amplifier for transmitting and outputting the laser light to the emitting side reflection film 15 side even if there is no injection current, and does not attenuate the laser light.

In particular, GRIN-S in the non-current injection region E1
In the CH-MQW active layer 3, the GRI of the current injection region E2 is
The energy of light from the N-SCH-MQW active layer 3 is G
Since the band gap energy of the RIN-SCH-MQW active layer 3 is almost equal to that of the RIN-SCH-MQW active layer 3, it absorbs the energy of the input light even if no current is injected, and functions as a saturable absorption region in which stimulated emission and spontaneous emission are repeated. Photon lifetime is reduced. As a result, the spectral line width of each oscillation longitudinal mode is widened, and as shown in FIG. 4B, the peak value of each oscillation longitudinal mode is further reduced, and the occurrence of stimulated Brillouin scattering can be suppressed.

Further, the non-current injection region E1 formed by the insulating film 8 is at most 70 μm, and considering that the resonator length L is 3200 μm ≧ L ≧ 800 μm, it is a small region. The laser output of the semiconductor laser device 20 according to the first embodiment is the same as the non-current injection region E1
It is possible to obtain almost the same laser output as that of a semiconductor laser device in which no laser is formed.

The length Li of the insulating film 8 is determined by the diffraction grating 1
It is preferable that the length exceeds the length Lg of 3. However, if the length Li of the insulating film 8 is made too long, the GRIN-SCH-MQW active layer 3 portion in the current injection region E2 becomes small and the output of the laser light is reduced. It is preferable to set the length Li to such a length that the diffusion of the injection current from the end point of the InGaAsP contact layer 4 on the side of the reflection film 14 toward the n-side electrode 11 does not affect the diffraction grating 13. Therefore, in the first embodiment, the length Li of the insulating film 8 is equal to the length L of the diffraction grating 13.
It is set to 60 μm, which is longer than g = 50 μm by 10 μm. As described above, since the GRIN-SCH-MQW active layer 3 in the non-current injection region E1 functions as a supersaturation absorption region, even if the insulating film 8 has a length exceeding the length of the diffraction grating 13, The GRIN-SCH-MQW active layer 3 covered with the insulating film 8 has a role of at least suppressing the occurrence of stimulated Brillouin scattering.

In the semiconductor laser device 20 shown in FIGS. 1 and 2, the diffraction grating 13 has a length Lg = 50 μm and the insulating film 8 has a length Li = 60 μm. 100 μm, coupling coefficient κ = 25 cm ⁻¹
It was found that a certain effect can be obtained even when the length Li of the insulating film 8 is set to Li = 130 μm. FIG. 6A is a diagram showing the optical output dependence of the monitor current when the length Lg of the diffraction grating is 100 μm and the insulating film 8 is not provided. In this case, the monitor current Im has a fluctuation that changes stepwise as the optical output increases over the entire optical output Po. On the other hand, FIG.
FIG. 6 is a diagram showing the optical output dependence of the monitor current when the length Lg of the diffraction grating is 100 μm and the length Li of the insulating film 8 is 130 μm. As shown in FIG. 6B, even when the length Lg of the diffraction grating is as long as 100 μm,
By providing the insulating film 8, the fluctuation of the monitor current Im is eliminated in the high output region of the optical output Po. Therefore, although the optical output Po cannot be used practically in the low output region, when the optical output Po is used in the high output region, the semiconductor laser device is suitable for practical use. That is, it is understood that the optical output dependency of the monitor current is improved by providing the insulating film 8 and forming the non-current injection region.

In the first embodiment, GRIN-SCH
Since the insulating film 8 is provided above the diffraction grating 13 so as to suppress the inflow of the injection current in the vicinity of the diffraction grating 13 partially provided along the MQW active layer 3, the monitor for the optical output is performed. Even in a semiconductor laser device with a stable current and a high output, the optical amplification control is simple and easy.

Further, from the exit side reflection film 15 to the diffraction grating 1
3 and the insulating film 8 extend, the GRI
It is expected that the injection current applied to the end face of the emission-side reflection film 15 of the N-SCH-MQW active layer 3 is also suppressed and the probability of occurrence of COD is reduced.

Further, the semiconductor laser device 20 selects the wavelength by the diffraction grating 13, and the oscillation wavelength is 1100 μm.
˜1550 μm band, resonator length L is 800 μm to 32
The oscillation wavelength spectrum 3
It is also considered that a laser beam having a plurality of oscillation longitudinal modes, preferably four or more oscillation longitudinal modes is output within a half-value width Δλh of 0 to form a supersaturated absorption region to broaden the spectral line width. , When used as a pumping light source for a Raman amplifier, stable and high 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 facilitated and mechanical vibration or the like may occur. Unstable output can be avoided.

In the first embodiment, GRIN-SC
Although the semiconductor laser device 20 has the diffraction grating 13 formed along the H-MQW active layer 3, the invention is not limited to this. The semiconductor laser device 20 has an optical waveguide adjacent to the active layer and diffracts along the optical waveguide. It is obvious that the same can be applied to the semiconductor laser device in which the grating is formed.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the first embodiment described above, the insulating film 8 is provided above the diffraction grating 13 between the InGaAsP contact layer 7 and the p-side electrode 10 to form the non-current injection region E1, and the vicinity of the diffraction grating 13 is formed. In the second embodiment, the p-side electrode 10 is not provided on the upper surface of the InGaAsP contact layer 7, which is the upper portion of the diffraction grating 13.
As a result, the non-current injection region E1 is formed.

FIG. 7 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the second embodiment of the present invention. In FIG. 7, the diffraction grating 13 is the same as that of the first embodiment and has a length Lg = 50 μm. An InGaAsP contact layer 7 is formed on the entire upper surface of the p-InP clad layer 6, and p is formed on the upper surface of the InGaAsP contact layer 7.
Although the side electrode 10 is formed, the p-side electrode 10 is not formed on the upper surface of the InGaAsP contact layer 7, which is a portion corresponding to the upper portion of the diffraction grating 13. Other configurations are the same as those in the first embodiment, and the same components are designated by the same reference numerals.

The region where the p-side electrode 10 is not formed is
This is the same as the insulating film 8 shown in the first embodiment, and is a region of 60 μm from the emitting side reflecting film 15. Therefore, the current injection into the vicinity of the diffraction grating 13 is suppressed, the optical amplification control becomes simple and easy as in the first embodiment, and as a result, a stable optical output can be obtained and the occurrence of stimulated Brillouin scattering can be prevented. It is possible to realize a semiconductor laser device that can be suppressed.

(Third Embodiment) Next, a third embodiment of the present invention will be described. In the first embodiment described above, the insulating film 8 is positively provided on the diffraction grating 13 between the InGaAsP contact layer 7 and the p-side electrode 10 to form the non-current injection region E1. Although the current injection into the vicinity of 13 is suppressed, in the third embodiment, the InGaAsP contact layer 7 in the region above the diffraction grating 13 where the insulating film 8 is formed is not formed, As a result, the non-current injection region E1 is formed.

FIG. 8 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the third embodiment of the present invention. In FIG. 8, the diffraction grating 13 is the same as that of the first embodiment and has a length Lg = 50 μm. The InGaAsP contact layer 7 is not formed on the entire upper surface of the p-InP cladding layer 6, but is formed except for the portion corresponding to the upper portion of the diffraction grating 13. That is, the same as the insulating film 8 shown in the first embodiment, and in the region 60 μm from the emitting side reflection film 15,
The InGaAsP contact layer 7 is not formed. This I
Since the nGaAsP contact layer 7 is not formed, p-InP
The upper surface of the exposed region of the cladding layer 6 and InG
On the upper surface of the region where the aAsP contact layer 7 is formed,
The p-side electrode 10 is formed. Other configurations are the same as those in the first embodiment, and the same components are designated by the same reference numerals.

As a result, the p-side electrode 10 and the p-InP cladding layer 6 are directly joined to each other to have a high resistance value, but the p-side electrode 10 joined via the InGaAsP contact layer 7 is formed. And the p-InP clad layer 6 exhibit a low resistance value. Therefore, the current injection into the vicinity of the diffraction grating 13 is suppressed, the monitor current with respect to the optical output is stable, and the optical amplification control is simple and easy even in a high-output semiconductor laser device, as in the first embodiment. In addition, the occurrence of stimulated Brillouin scattering can be suppressed.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. In the above-described first embodiment, p-type InGa that is the upper part of the diffraction grating 13 is used.
An insulating film 8 is provided between the AsP contact layer 7 and the p-side electrode 10.
Although the non-current injection region E1 is formed to suppress the current injection into the vicinity of the diffraction grating 13, in the fourth embodiment, the n-InP layer 18 is formed instead of the insulating film 8. By doing so, the current blocking layer is formed, and thereby the non-current injection region E1 is formed.

FIG. 9 is a longitudinal sectional view in the longitudinal direction of a semiconductor laser device according to the fourth embodiment of the present invention. In FIG. 9, the diffraction grating 13 is the same as that of the first embodiment and has a length Lg = 50 μm. An InGaAsP contact layer 7 is formed on the entire upper surface of the p-InP clad layer 6, and the InGa corresponding to the upper portion of the diffraction grating 13 is InGa.
An n-InP layer 18 is formed on the upper surface of the AsP contact layer 7. That is, the insulating film 8 shown in the first embodiment
The n-InP layer 18 is formed at the same position as. n-In
A p-side electrode 10 is formed on the upper surface of the P layer 18 and the upper surface of the InGaAsP contact layer 7 where the n-InP layer 18 is not formed. Other configurations are the same as those of the first embodiment.
The same components are denoted by the same reference numerals.

As a result, the n-InP layer 18 and the p-InP layer are formed.
The junction with the cladding layer 6 is n in the direction of the diffraction grating 13.
It becomes a p-junction and functions as a current blocking layer. Therefore, the current injection into the vicinity of the diffraction grating 13 is suppressed,
Similar to the first embodiment, the monitor current with respect to the optical output is stable, and even in a high-output semiconductor laser device, optical amplification control is simple and easy.

In the configuration of the fourth embodiment, n-
The increase in contact resistance between the InP layer 18 and the electrode 10 and the reverse bias between the n-InP layer 18 and the InGaAsP contact layer 7 result in n-I.
The current injection into the lower part of the nP layer 18 is suppressed. Therefore, the contact resistance between the n-InP layer 18 and the electrode 10 is large, such as between the n-InP layer 18 and the electrode 10.
Instead of the InP layer 18, for example, i-InP (intrinsic In
P) layer, p-InP layer, n-InGaAsP layer, i-I
nGsAsP layer, n-InGaAs layer, i-InGaA
The s layer may be formed to increase the contact resistance to suppress the current injection into the vicinity of the diffraction grating 13. Even with such a configuration, the monitor current with respect to the optical output is stable, and even with a high-output semiconductor laser device, simple and easy optical amplification control can be realized and the occurrence of stimulated Brillouin scattering can be suppressed. You can

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described. In the above-described fourth embodiment, p-type InGa that is the upper part of the diffraction grating 13 is used.
N-In is formed between the AsP contact layer 7 and the p-side electrode 10.
Although the non-current injection region E1 is formed by providing the P layer 18 and forming the current blocking layer, the current injection into the vicinity of the diffraction grating 13 is suppressed, but in the fifth embodiment, the diffraction grating 13 is formed. Corresponding to the top of the InGaA
An n-type impurity is diffused into the sP contact layer 7 to change it into an n-type semiconductor, and a current blocking layer is formed by the p-InP clad layer 6, whereby a non-current injection region E1 is formed.

FIG. 10 is a longitudinal sectional view in the longitudinal direction of a semiconductor laser device according to the fifth embodiment of the present invention. Figure 10
In, the diffraction grating 13 is the same as that of the first embodiment and has a length Lg = 50 μm. An InGaAsP contact layer 7 is formed on the entire upper surface of the p-InP clad layer 6. Of this InGaAsP contact layer 7,
InGaAsP contact layer 7 corresponding to the diffraction grating 13
Of the p-InP clad layer 6 in contact with the InGaAsP contact layer 7 by adding and diffusing n-type impurities.
The n-type region 17a is formed by changing to a mold. Note that n
The addition and diffusion of the type impurities can be performed by combining various methods such as ion implantation and annealing.
After that, on the upper surface of the InGaAsP contact layer 7, p
The side electrode 10 is formed. The other configuration is the same as that of the fourth embodiment, and the same components are designated by the same reference numerals.

As a result, an np junction is formed in the direction of the diffraction grating 13 without newly providing the n-InP layer 18, and this np junction functions as a current blocking layer. Therefore, the current injection into the vicinity of the diffraction grating 13 is suppressed, the monitor current with respect to the optical output is stable, and the optical amplification control is simple and easy even in a high-output semiconductor laser device, as in the first embodiment. In addition, the occurrence of stimulated Brillouin scattering can be suppressed.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described. In the fifth embodiment described above, by forming the n-type region 17a, n-In
Although no new semiconductor layer such as the P layer 18 is provided, in the sixth embodiment, the non-current injection region E is formed by increasing the resistance of the region corresponding to the n-type region 17a.
1 is formed.

FIG. 11 is a longitudinal sectional view in the longitudinal direction of a semiconductor laser device which is Embodiment 6 of the present invention. Figure 11
In, the high resistance region 17b having the increased resistance is formed at the same position as the n-type region 17a shown in the fifth embodiment. The other configuration is the same as that of the sixth embodiment, and the same components are designated by the same reference numerals. As shown in FIG. 12, the high resistance region 17b is formed by ion-implanting protons (H +) into the portion corresponding to the diffraction grating 13 from above after the InGaAsP contact layer 7 is formed. .

As a result, the current injected from the p-side electrode 10 is generated by the diffraction grating 13 due to the existence of the high resistance region 17b.
It becomes difficult to flow into the vicinity, and the current injection into the vicinity of the diffraction grating 13 is suppressed without newly providing the n-InP layer 18 and the like, so that the monitor current with respect to the optical output becomes stable as in the first embodiment. Even in a high-output semiconductor laser device, optical amplification control can be simplified and facilitated, and the occurrence of stimulated Brillouin scattering can be suppressed.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described. In the first embodiment described above, the insulating film 8 is provided to form the non-current injection region E1, but in the seventh embodiment, the groove portion is further provided near the end of the insulating film 8 on the reflection film 14 side. 40 is formed to further suppress the injection current from flowing into the diffraction grating 13.

FIG. 13 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the seventh embodiment of the present invention. FIG.
In, the InGaAsP contact layer 7 is spatially separated from the InGaAsP contact layers 7 a and 7 b in the vicinity of 60 μm from the emitting side reflection film 15. InGaAsP
When the contact layer 7 is formed, the lateral groove 40 is formed.
Are formed, whereby the InGaAsP contact layer 7 is separated. At this time, a part of the p-InP clad layer 6 is also scraped off to form the groove 40.

After the groove 40 is formed, the insulating film 8 is formed.
InGaAsP contact layer 7a, InGaAsP
The contact layer 7b is formed on the ends of the contact layer 7b on the emitting side reflection film 15 side and on the upper surfaces of the groove 40 sandwiched therebetween. Further, the p-side electrode 10 is formed on each upper surface of the insulating film 8 and the InGaAsP contact layer 7b.

As a result, the current injected from the p-side electrode 10 depends on the structure of the insulating film 8 formed in the groove 41.
Since the inflow of the injection current in the direction of the diffraction grating 13 is suppressed, the monitor current with respect to the optical output is stable as in the first embodiment, and the optical amplification control is simple and easy even in a high-output semiconductor laser device. And the occurrence of stimulated Brillouin scattering can be suppressed.

(Embodiment 8) Next, an embodiment 8 of the invention will be described. Embodiments 1 to 7 described above
In the above, the p-side electrode 10 is formed as an integrated thin film, but in the eighth embodiment, the two electrodes spatially corresponding to the non-current injection region E1 and the current injection region E2 are spatially formed. Separated and electrically isolated.

FIG. 14 is a longitudinal sectional view in the longitudinal direction of a semiconductor laser device according to the eighth embodiment of the present invention. 14
In the above, between the non-current injection region E1 and the current injection region E2, the groove 41 is formed from a part of the upper surface of the p-InP cladding layer 6 to the upper side and in the vicinity of 60 μm from the emitting side reflection film 15. Has been done. An InGaAsP contact layer 7a is formed on the upper surface of the p-InP clad layer 6 on the non-current injection region E1 side, and I is formed on the upper surface of the current injection region E2 side.
The nGaAsP contact layer 7b is formed. On the non-current injection region E1 side, an electrode 8a is further formed on the InGaAsP contact layer 7a, and a plating 12a is formed on the upper surface of the electrode 8a. On the other hand, the current injection region E
On the second side, an electrode 8b is further formed on the upper surface of the InGaAsP contact layer 7b, and a plating 12b is further formed. Other configurations are the same as those in the first embodiment, and the same components are designated by the same reference numerals.

The groove 41 is formed by forming the p-InP cladding layer 6 and then forming the InGaAsP contact layer 7 corresponding to the InGaAsP contact layers 7a and 7b on the entire upper surface of the p-InP cladding layer 6. ,
InGaA in the vicinity of 60 μm from the emitting side reflection film 15
It is formed by etching the sP contact layer 7. After that, the InGaAsP contact layers 7a, 7
Electrodes 8a and 8b are formed on each upper surface of b, and platings 12a and 12b are further formed. This plating 12b is p
Form a side electrode. A wire (not shown) for supplying an injection current is bonded to the plating 12b side. Therefore, the plating 12a is not energized, and the injection current is applied to the GRIN-SCH-MQW active layer 3 on the plating 12b side.

As a result, since the injection current is applied only from the side of the plating 12b and the presence of the groove 41 suppresses the inflow of the injection current in the direction of the diffraction grating 13, the light output is the same as in the first embodiment. Even when the semiconductor laser device has a stable monitor current and a high output, the optical amplification control can be simplified and facilitated, and the occurrence of stimulated Brillouin scattering can be suppressed.

Here, in the semiconductor laser device shown in FIG. 14, normally, as shown in FIG.
Is used by being joined (junction down) to the heat sink 57a side. In this junction down method, G as a heat source is used in the entire semiconductor laser device.
RIN-SCH-MQW active layer 3 is plated 12a, 12
Since it is arranged on the b side, the temperature control becomes easy by bringing the GRIN-SCH-MQW active layer 3 closer to the heat sink 57 side. However, if the structure of the semiconductor laser device shown in FIG. 14 is subjected to a junction down as it is, the plating 12a and 12b become conductive, so that the conduction pattern 16 of Au is formed at the contact portion of the heat sink 57a on the plating 12b side. It Here, since the heat sink 57a has a high thermal conductivity and is made of an insulating material, the plating 12a side and the plating 12b side are insulated from each other. The plating 12a, the electrode 8a, the InGaAsP contact layer 7a
Has a high thermal conductivity, so that the heat on the non-current injection region E1 side can be efficiently conducted to the heat sink 57a side. The conductive pattern 16 extends on the heat sink 57a other than the joint between the semiconductor laser device and the heat sink 57a, is bonded to the wire 16a, and is supplied with an injection current. If such a junction down method is adopted, as described above, GR with a large amount of heat is generated.
The IN-SCH-MQW active layer 3 side is provided with a heat sink 57a.
The temperature control of the semiconductor laser device 20 is facilitated and the output stability can be further maintained.

It is preferable to adopt the junction down method also in the first to seventh embodiments described above or the embodiments described later. This is because the temperature control of the semiconductor laser device 20 is facilitated as described above, and the output stability can be further maintained.

(Ninth Embodiment) Next, a ninth embodiment of the present invention will be described. Embodiments 1 to 8 described above
In each of the above, the diffraction grating 13 is provided on the emission side reflection film 15 side, but in the ninth embodiment, the diffraction grating 13 is also provided on the reflection film 14 side.

FIG. 16 is a longitudinal sectional view in the longitudinal direction of a semiconductor laser device which is Embodiment 9 of the present invention. FIG.
In this semiconductor laser device, the diffraction grating 13 having the length Lga from the reflection film 14 side is also provided on the reflection film 14 side.
The insulating film 8a is provided in order to prevent the decrease of the refractive index of the diffraction grating 13a. This insulating film 8a is
Similar to the insulating film 8, the upper part of the diffraction grating 13a, p
It is provided between the InP clad layer 6 and the p-side electrode 10 and has a length Lia. This length Lia is the length Lg
Is the same as the relationship between the length L and the length Li, and is set to a minimum length that can cover the length Lga. The diffraction grating 13a on the side of the reflection film 14 has wavelength selectivity and reflection characteristics.
The product of the length and the length Lga may be set to a large value, for example, “2” or more.

As a result, the non-current injection region E3 can be formed also on the diffraction grating 13a side, and the diffraction grating 13a can be formed.
Since the inflow of the injection current into the vicinity is suppressed, the monitor current with respect to the optical output becomes stable, as in the first embodiment.
Even in a high-power semiconductor laser device, optical amplification control becomes simple and easy. Further, it is possible to prevent end face deterioration on the end face on the reflective film 14 side. Even in the semiconductor laser device provided with only the diffraction grating 13a, by applying the ninth embodiment, the monitor current with respect to the optical output is stable, and even in the high output semiconductor laser device, the optical amplification is performed. The control is simple and easy, and the occurrence of stimulated Brillouin scattering can be suppressed.

In the above-described first to ninth embodiments, the diffraction grating 13 or the diffraction grating 13a outputs a plurality of oscillation longitudinal modes by the wavelength selectivity having fluctuation with respect to the center wavelength. Alternatively, it is possible to obtain a semiconductor laser device capable of increasing the number of oscillation longitudinal modes by positively giving fluctuations to the diffraction grating 13 or the diffraction grating 13a.

FIG. 17 is a diagram showing a periodical change in the grating period of the diffraction grating 13. This diffraction grating 13
Is a chirped grating in which the grating period is periodically changed. In FIG. 17, fluctuations are caused in the wavelength selectivity of the diffraction grating 13, 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. Other configurations are the same as those of the first to ninth embodiments, and the same components are designated by the same reference numerals.

As shown in FIG. 17, the diffraction grating 13 has a structure in which the average period is 220 nm and the period fluctuation (deviation) of ± 0.02 nm is repeated in the 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. 18 shows different periods Λ1 and Λ2.
FIG. 6 is a diagram showing an oscillation wavelength spectrum of a semiconductor laser device having the diffraction grating of FIG. In FIG. 18, the diffraction grating with period Λ1 forms an oscillation wavelength spectrum of wavelength λ1 and selects three oscillation longitudinal modes within this oscillation wavelength spectrum. On the other hand, the diffraction grating with the period Λ2 forms the oscillation wavelength spectrum of the wavelength λ2, and selects three oscillation longitudinal modes within this oscillation wavelength spectrum. Therefore, the periods Λ1 and Λ2
The complex oscillation wavelength spectrum 45 by the diffraction grating of No. 4 includes four to five oscillation longitudinal modes in the complex 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 13 is not limited to the chirped grating in which the grating period is changed at a constant period C, and the grating period is set to the period Λ1 (220 nm + 0.02 nm) and the period Λ2 (220n).
m-0.02 nm) may be randomly changed.

Further, as shown in FIG. 19A, a periodic fluctuation may be provided as a diffraction grating in which the period Λ1 and the period Λ2 are alternately repeated once. Further, as shown in FIG. 19B, a period fluctuation may be provided as a diffraction grating in which the period Λ1 and the period Λ2 are alternately repeated a plurality of times. Further, as shown in FIG. 19C, a diffraction grating having a plurality of continuous cycles Λ1 and a plurality of continuous cycles Λ2 may be provided with periodic fluctuations. Further, the periods having discretely different values between the period Λ1 and the period Λ2 may be complementarily arranged.

(Tenth Embodiment) Next, a tenth embodiment of the present invention will be described. Embodiment 1 described above
9 to 9, the diffraction grating 13 is formed in the non-current injection region E1.
However, in the tenth embodiment,
A non-current injection region is provided in a region where the diffraction grating 13 does not exist to positively suppress the generation of stimulated Brillouin scattering.

FIG. 20 is a longitudinal sectional view in the longitudinal direction of the semiconductor laser device according to the tenth embodiment of the present invention. Further, FIG. 21 is a cross sectional view of the semiconductor laser device shown in FIG.
It is an A line sectional view. 20 and 21, the semiconductor laser device 21 is a Fabry-Perot type semiconductor laser device, and has a configuration in which the diffraction grating 13 of the semiconductor laser device shown in FIGS. 1 and 2 is removed. As a result, the GRIN-SCH-M located under the insulating film 8
No current is injected into the QW active layer 3, and the GRIN-SCH-MQW active layer 3 located under the region other than the insulating film 8 is located.
A supersaturated absorption region E10 that absorbs light from is formed.

In the supersaturated absorption region E10, the photon lifetime is reduced, and as a result, the spectral line width of each oscillation longitudinal mode is widened and the peak value of each oscillation longitudinal mode is reduced, so that the stimulated Brillouin scattering occurs. Is suppressed.

The semiconductor laser device 21 is a Fabry-Perot type semiconductor laser device. For example, as shown in FIG. 32, an optical fiber 203 having a fiber grating 233 is connected for wavelength selection.
It is used as a pumping light source for DFA and Raman amplifiers.

Here, the insulating film 8 can be arranged without being influenced by the positional relationship of the diffraction grating 13, and the GRI
The N-SCH-MQW active layer 3 can be disposed at any position on the active layer 3. For example, as shown in FIG. 22, the insulating film 8 may be provided on the reflective film 14 side and the supersaturated absorption region E11 may be formed on the reflective film 14 side. Also,
As shown in FIG. 23, the insulating film 8 is formed near the center in the longitudinal direction.
And the GRIN-SCH located under the insulating film.
The supersaturated absorption region E12 may be formed in the MQW active layer 3.

Further, as the insulating film 8a shown in FIG. 24, an insulating film may be formed in a partial region in the lateral direction above the GRIN-SCH-MQW active layer 3. In this case, the region of the GRIN-SCH-MQW active layer 3 where the current is not injected by the provided insulating film 8a becomes the supersaturation absorption region E10a.

Further, in each of the semiconductor laser devices shown in FIGS. 20 to 24, the insulating film 8 corresponding to the first embodiment is provided to form the supersaturation absorption region, but the present invention is not limited to this. The supersaturated absorption region can be formed in the same manner as the formation of the non-current injection region shown in the second to ninth embodiments described above.

For example, FIG. 25 is a longitudinal cross-sectional view showing the structure of a semiconductor laser device showing a modification corresponding to the second embodiment of the present invention. In this case, the p-side electrode 1
The region of the GRIN-SCH-MQW active layer 3 which is not covered with 0 becomes the supersaturation absorption region E21.

FIG. 26 is a diagram showing the results of measurement of the reflected light of stimulated Brillouin scattering with and without the supersaturation absorption region E10 shown in the semiconductor laser device 21. The measurement condition is as follows: drive current Iop =
It is 100 mA, and the resonator length L is 1500 μm.
In FIG. 26, the reflected light level of stimulated Brillouin scattering at which the occurrence of stimulated Brillouin scattering starts is about −28 dB or more, and when the supersaturated absorption region E10 is provided, the reflected light level of stimulated Brillouin scattering is −28 dB. It is below, but stimulated Brillouin scattering is suppressed, but in the case where the supersaturated absorption region E10 is not provided, the reflected light level of stimulated Brillouin scattering is -28 dB or more and is dispersed in the range of -28 dB to -10 dB, Brillouin scattering is occurring. From this result, it is understood that the stimulated Brillouin scattering can be effectively suppressed by providing the supersaturated absorption region E10.

(Embodiment 11) Next, an embodiment 11 of the invention will be described. In the eleventh embodiment, the semiconductor laser device shown in the above-described first to tenth embodiments is modularized. However, in the semiconductor laser device shown in the tenth embodiment, an optical fiber (not shown) having a fiber grating is connected to the outside.

FIG. 27 is a longitudinal sectional view showing the structure of the semiconductor laser module according to the eleventh embodiment of the present invention. In FIG. 27, this semiconductor laser module 50
Has a semiconductor laser device 51 corresponding to the semiconductor laser device shown in the above-described first to tenth embodiments. In addition,
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 50, 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. The base 57 is arranged on the Peltier element 58,
A heat sink 57a is arranged on the base 57. 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 cools the laser light to a lower temperature when the wavelength of the laser light is longer than the desired wavelength, and controls the temperature to a low temperature when the laser light has a shorter wavelength than the desired wavelength. Is heated and controlled to a high temperature. This temperature control is specifically controlled on the heat sink 57a 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 temperature of the heat sink 57a. The Peltier element 58 is controlled so that is maintained constant. In addition, the control device (not shown) causes the temperature of the heat sink 57a to decrease as the drive current of the semiconductor laser device 51 increases, and the Peltier element 58 is then included.
To control. 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 preferably formed of a material having a high thermal conductivity such as diamond. this is,
This is because if the heat sink 57a is made 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, the semiconductor laser module 50
Then, the semiconductor laser device 51 and the optical fiber 5 are arranged so that the return light reflected by other optical components does not return to the inside of the resonator.
An isolator 53 is interposed between the isolator 53 and the element 5. Unlike the conventional semiconductor laser module using a fiber grating, the isolator 53 is not an in-line fiber type, but a polarization-independent type isolator that can be built in the semiconductor laser module 50 can be used. It is possible to reduce insertion loss due to, to achieve lower relative intensity noise (RIN), and to reduce the number of parts.

In the eleventh embodiment, the first to the first embodiments are described.
Since the semiconductor laser device shown by 10 is modularized, a polarization-independent isolator can be used, insertion loss can be reduced, and noise reduction and the number of parts can be promoted. .

(Twelfth Embodiment) Next, a twelfth embodiment of the present invention will be described. In the twelfth embodiment, the semiconductor laser module described in the eleventh embodiment is applied to a Raman amplifier.

FIG. 28 is a block diagram showing the structure of the Raman amplifier according to the twelfth embodiment of the present invention. This Raman amplifier is used in a WDM communication system. Figure 2
8, the Raman amplifier uses semiconductor laser modules 60a to 60d having the same configuration as the semiconductor laser module shown in the eleventh embodiment, and the semiconductor laser modules 182a to 182d shown in FIG. It has a configuration in which the modules 60a to 60d are replaced.

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 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 the WDM coupler 65 and the isolator 66, and 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 twelfth embodiment, for example, the semiconductor light emitting device 180a shown in FIG.
And a fiber grating 181a are coupled by a polarization maintaining fiber 71a to a semiconductor laser module 182.
Since the semiconductor laser module 60a incorporating the semiconductor laser device shown in the first to ninth embodiments is used instead of a, it is possible to reduce the use of the polarization maintaining fiber 71a. 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. 28,
The polarization combining 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.

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

The Raman amplifiers shown in FIGS. 28 and 29 are of the backward pumping type, but are 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. 28 or 29 can be applied to the WDM communication system as described above. FIG. 30 is a block diagram showing a schematic configuration of a WDM communication system to which the Raman amplifier shown in FIG. 28 or 29 is applied.

In FIG. 30, a plurality of transmitters Tx1 to Tx are provided.
The optical signals of wavelengths λ1 to λn transmitted 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. 28 or 29 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 λ1 to λn and received by the plurality of receivers Rx1 to Rxn. An ADM (Add / Drop Mul) for adding and extracting an optical signal of an arbitrary wavelength is provided on the optical fiber 85.
tiplexer) may be inserted.

In the twelfth embodiment described above, the semiconductor laser device shown in the first to tenth embodiments or the semiconductor laser module shown in the eleventh 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 of 0.98 μm or the like, for example. Particularly, in the remote pump EDFA in which the transmission distance of the pumping light to the EDF is several kilometers to several tens of kilometers, by using the semiconductor laser device according to the first to tenth embodiments or the embodiment as the pumping light source, It is possible to effectively suppress a decrease in amplification gain due to stimulated Brillouin scattering during transmission.

[0153]

As described above, according to the invention of claim 1, between the first reflective film provided on the emitting end face of the laser beam and the second reflective film provided on the reflective end face of the laser beam. Having a diffraction grating partially provided in the vicinity of the formed active layer,
Non-current injection that suppresses injection current to a partial region of the active layer except the active layer near the diffraction grating when outputting laser light having a desired oscillation longitudinal mode by at least the wavelength selection characteristic of the diffraction grating A region is formed, a partial region of the active layer is made into a supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region to increase the spectral line width, so that the occurrence of stimulated Brillouin scattering occurs. There is an effect that can suppress.

According to the second aspect of the invention, the active layer is 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. When a Fabry-Perot resonator is formed and a laser beam having at least a plurality of oscillation longitudinal modes is output, a non-current injection region that suppresses an injection current to a partial region of the active layer is formed, and one of the active layers is formed. The partial region is made into a supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region to increase the spectral line width, so that it is possible to suppress the occurrence of stimulated Brillouin scattering. .

According to the third to twenty-fourth aspects of the present invention, all of the regions of the active layer are made into the supersaturated absorption region, and the photon lifetime is reduced in this supersaturated absorption region to increase the spectral line width. Therefore, it is possible to suppress the occurrence of stimulated Brillouin scattering.

According to the inventions of claims 25 to 27,
Since a semiconductor laser device or a semiconductor laser module that outputs a laser beam capable of suppressing the occurrence of stimulated Brillouin scattering is used, optical output can be achieved, which is suitable for a remote pump EDFA or a Raman amplifier, and WDM communication with a reduced number of amplifiers. The effect that a system can be built is produced.

[Brief description of drawings]

FIG. 1 is a longitudinal cross sectional view showing a configuration of a semiconductor laser device according to a first embodiment of the present invention.

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

FIG. 3 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. 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 a threshold value for stimulated Brillouin scattering.

FIG. 5 is a diagram showing optical output dependence of a monitor current in the semiconductor laser device according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a difference in optical output dependency of a monitor current depending on the presence / absence of a non-current injection region when the diffraction grating length is 100 μm.

FIG. 7 is a longitudinal cross-sectional view showing a structure of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 8 is a longitudinal sectional view in a longitudinal direction showing a configuration of a semiconductor laser device which is Embodiment 3 of the present invention.

FIG. 9 is a longitudinal sectional view in a longitudinal direction showing a configuration of a semiconductor laser device which is Embodiment 4 of the present invention.

FIG. 10 is a longitudinal cross-sectional view showing the structure of a semiconductor laser device according to a fifth embodiment of the present invention.

FIG. 11 is a longitudinal cross-sectional view showing the structure of a semiconductor laser device according to a sixth embodiment of the present invention.

12 is an enlarged cross-sectional view of the vicinity of the emitting side reflection film of the InGaAsP contact layer shown in FIG.

FIG. 13 is a longitudinal cross-sectional view showing the structure of a semiconductor laser device according to a seventh embodiment of the present invention.

FIG. 14 is a longitudinal cross-sectional view showing the structure of a semiconductor laser device according to an eighth embodiment of the present invention.

FIG. 15 is a cross-sectional view showing a configuration when the semiconductor laser device shown in FIG. 13 is joined to a heat sink by junction down.

FIG. 16 is a longitudinal cross-sectional view showing the structure of a semiconductor laser device according to a ninth embodiment of the present invention.

FIG. 17 is a diagram showing a configuration of a chirped grating applied to a diffraction grating.

FIG. 18 is a diagram showing an oscillation wavelength spectrum when a chirped grating is applied to a diffraction grating.

FIG. 19 is a diagram showing a modified example of a grating having periodic fluctuation.

FIG. 20 is a longitudinal cross-sectional view showing the structure of a semiconductor laser device according to a tenth embodiment of the present invention.

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

FIG. 22 is a longitudinal sectional view in the longitudinal direction showing the configuration of a modification of the semiconductor laser device according to the tenth embodiment of the present invention.

FIG. 23 is a longitudinal cross sectional view in the longitudinal direction showing the configuration of a modification of the semiconductor laser device according to the tenth embodiment of the present invention.

FIG. 24 is a longitudinal sectional view in the longitudinal direction showing the configuration of a modification of the semiconductor laser device according to the tenth embodiment of the present invention.

FIG. 25 is a longitudinal cross-sectional view showing the structure of a modification of the semiconductor laser device according to the tenth embodiment of the present invention in the longitudinal direction.

FIG. 26 is a diagram showing experimental results of reflected light of stimulated Brillouin scattering in the semiconductor laser device shown in FIG. 20 with and without a supersaturated absorption region.

FIG. 27 is a vertical sectional view showing a structure of a semiconductor laser module according to an eleventh embodiment of the present invention.

FIG. 28 is a block diagram showing the configuration of a Raman amplifier that is Embodiment 12 of the present invention.

FIG. 29 is a diagram showing an application example of the twelfth embodiment of the present invention.

30 is a block diagram showing a schematic configuration of a WDM communication system using the Raman amplifier shown in FIG. 28 or FIG. 29.

FIG. 31 is a block diagram showing a schematic configuration of a conventional Raman amplifier.

32 is a diagram showing a configuration of a semiconductor laser module used in the Raman amplifier shown in FIG.

FIG. 33 is a diagram showing optical output dependence of a monitor current in a conventional semiconductor laser device.

[Explanation of symbols]

1 n-InP substrate 2 n-InP buffer layer 3 GRIN-SCH-MQW active layer 4 p-InP spacer layer 6 p-InP clad layer 7 InGaAsP contact layer 8 insulating film 9a n-InP blocking layer 9b p-InP blocking layer 10 p side electrode 11 n-side electrode 12a, 12b plating 13,13a Diffraction grating 14 Reflective film 15 Emitting side reflective film 16 conduction patterns 16a wire 17a n-type region 17b High resistance area 18 n-InP layer 20,51 Semiconductor laser device 30 oscillation wavelength spectrum 31-33 Oscillation longitudinal mode 40, 41 groove 45 Compound oscillation wavelength spectrum 50, 60a-60d Semiconductor laser module 52 First lens 53,63,66 Isolator 54 second lens 55 optical fiber 56 Current monitor 57 base 57a heat sink 58 Peltier element 58a thermistor 59 packages 61a, 61b Polarization combining coupler 62,65 WDM coupler 64 amplification fiber 67 Monitor Optical Distribution Coupler 68 Control circuit 69 optical signal input fiber 70 signal light output fiber 71 Polarization maintaining fiber 81,83 Raman amplifier E1 Non-current injection area E2 Current injection area E11-E12, E10a, E21 Supersaturated absorption region

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasushi Oki             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. F-term (reference) 2H037 AA01 BA03 DA38                 5F073 AA03 AA11 AA21 AA46 AA64                       AA74 BA01 CA12 EA01 FA06                       FA25 FA30 GA22

Claims (27)

[Claims] 1. Diffraction partially 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, in a partial region of the active layer except the active layer near the diffraction grating, A semiconductor laser device characterized by forming a non-current injection region for suppressing an injection current. 2. A Fabry-Perot resonator is formed by 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, and at least a Fabry-Perot resonator is formed. A semiconductor laser device for outputting a laser beam having a plurality of oscillation longitudinal modes, characterized by forming a non-current injection region for suppressing an injection current to a partial region of the active layer. 3. The semiconductor laser device according to claim 1, wherein the non-current injection region is formed by an insulating film which covers an upper portion of a partial region of the active layer. 4. The semiconductor laser device according to claim 1, wherein the electrode to which the injection current is applied is provided except at least an upper surface of a partial region of the active layer. . 5. A contact layer, which is provided between an upper clad layer for confining light in the active layer and an electrode for applying the injection current, and which reduces a contact resistance of the injection current, at least in a partial region of the active layer. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is provided excluding an upper surface. 6. The upper clad layer is formed between the upper clad layer for confining light in the active layer and the electrode for applying the injection current, at a position corresponding to an upper portion of a partial region of the active layer. 6. A semiconductor according to claim 1, further comprising a current blocking layer that forms a diode junction that blocks a current flowing from the electrode toward a partial region of the active layer. Laser device. 7. The electrode is located between the upper clad layer for confining light in the active layer and the electrode for applying the injection current, at a position corresponding to an upper portion of a partial region of the active layer with respect to the electrode. 7. The semiconductor laser device according to claim 1, further comprising a high contact resistance layer formed of a material having a high contact resistance. 8. A contact layer formed on an upper surface of an upper clad layer for confining light in the active layer, a first contact layer corresponding to an upper portion of a partial region of the active layer, and a partial region of the active layer. Is spatially separated from a second contact layer that does not correspond to the upper part of the first contact layer, and the upper surface of the first contact layer and the groove formed by the separation are covered with an insulating film or a current blocking layer. The semiconductor laser device according to claim 1, wherein the electrode is formed on the entire surface of the film or the current blocking layer. 9. A contact layer formed on an upper surface of an upper clad layer for confining light in the active layer, a first contact layer corresponding to an upper portion of a partial region of the active layer, and a partial region of the active layer. The second contact layer which does not correspond to the upper part of the above is spatially separated, and electrodes are formed on the upper surfaces of the first contact layer and the second contact layer, respectively. Semiconductor laser device. 10. A region located on an upper surface of a partial region of the active layer in the cladding layer and / or the first region.
10. The carrier concentration of the contact layer is lower than the carrier concentration of the cladding layer.
The semiconductor laser device according to any one of 1. 11. A region located on the upper surface of a partial region of the active layer of the cladding layer and / or the first region.
11. The semiconductor laser device according to claim 1, wherein the contact layer has a high resistance due to proton irradiation. 12. A region located on an upper surface of a partial region of the active layer in the cladding layer and / or the first region.
11. The semiconductor laser device according to claim 1, wherein the contact layer forms a current blocking layer with respect to the cladding layer by adding and diffusing n-type impurities. 13. The semiconductor laser device according to claim 1, wherein the diffraction grating is provided on the first reflection film side or in the vicinity of the first reflection film. 14. The semiconductor laser device according to claim 1, wherein the diffraction grating is provided on the second reflection film side or in the vicinity of the second reflection film. 15. The diffraction grating is provided on the first reflection film side or in the vicinity of the first reflection film and on the second reflection film side or in the vicinity of the second reflection film. 12. The semiconductor laser device according to any one of 1 to 12. 16. The semiconductor laser according to claim 1, wherein the desired number of oscillation longitudinal modes is two or more within a half-value width of an oscillation wavelength spectrum. apparatus. 17. The diffraction grating has a diffraction grating length of 300.
17. The semiconductor laser device according to claim 1, wherein the semiconductor laser device has a thickness of μm or less. 18. The diffraction grating length of the diffraction grating is equal to or less than a value of (300/1300) times the resonator length, according to any one of claims 1 to 3. Semiconductor laser device. 19. The diffraction grating according to claim 1, wherein a multiplication value of a coupling coefficient of the diffraction grating and a diffraction grating length is 0.3 or less. Semiconductor laser device. 20. The semiconductor laser device according to claim 1, wherein the diffraction grating has a grating period changed randomly or in a predetermined period. 21. 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.
The semiconductor laser device according to any one of 3 to 20. 22. The semiconductor laser device according to claim 1, an optical fiber for guiding the laser light emitted from the semiconductor laser device to the outside, and an optical coupling between the semiconductor laser device and the optical fiber. A semiconductor laser module comprising: an optical coupling lens system for performing. 23. 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 22, wherein: 24. The semiconductor laser module according to claim 22, wherein an optical fiber grating for wavelength selection is connected to the output side of the optical fiber. 25. The semiconductor laser module according to claim 22, an amplification optical fiber, a pumping light output from the semiconductor laser module, and a signal propagating in the amplification optical fiber. An optical fiber amplifier comprising: a coupler for multiplexing light. 26. The amplification optical fiber amplifies the signal light by Raman amplification.
The optical fiber amplifier according to. 27. The optical fiber amplifier according to claim 25, wherein the amplification optical fiber is an erbium-doped fiber, and the semiconductor laser module and the amplification optical fiber are arranged remotely.