JP2008021913A - Semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device capable of executing stable operation while allowing an FFP of output light to show excellent unimodal characteristics without causing COD, even when executing operation at high output levels. <P>SOLUTION: The semiconductor laser device is provided with a first n-type clad layer 13, a strained quantum well active layer 12, and a first p-type clad layer 11 that are formed in turn from below on an n-type substrate 10, a first current block layer 1 formed on an upper face of the first p-type clad layer at each side of a ridge provided above the first p-type clad layer 11 and on the side faces of the ridge, and a first light-absorbing current block layer 3 that is formed on the first current block layer 1 near the light output end faces from which a laser beam is outputted. Near the light output end faces, impurities are introduced into the strained quantum well active layer 12 and a window region 4a is provided whose composition is disordered. In the window region 4a, the first current block layer 1 is also formed on the upper face of the ridge. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device used as a light source for pickup of an optical disk device, a light source of an electronic device, an information processing device, and the like.

  In recent years, as a light source for information processing equipment such as optical disks such as CD and DVD, a semiconductor laser device that outputs laser light having an infrared wavelength using an AlGaAs mixed crystal, or a red wavelength using an AlGaInP mixed crystal. Semiconductor laser devices that output laser light have been put into practical use. All of the semiconductor laser devices require a light output of 30 mW or more in a rewritable optical disk. In the future, in order to realize higher speed and smaller size of the semiconductor laser device, a higher light output of about 50 mW to 200 mW is required. Required. However, when increasing the output of a semiconductor laser device, there is a problem that the characteristics of the semiconductor laser deteriorate due to crystal breakage at the end face of the output light (hereinafter referred to as the output end face) in the laser resonator. This is a serious problem in semiconductor laser devices using crystals. Therefore, as a means for realizing high output, an end face window structure having a quantum well structure formed using a material transparent to laser light on the output end face is effective. The end face window structure is formed by diffusing impurities in the active layer of the quantum well structure. This utilizes the phenomenon that when the impurities are diffused, the atoms in the active layer are solid-phase diffused and disordered.

  Recently, there is a strong demand for a semiconductor laser device in which laser light sources having different wavelengths are integrated on the same substrate. For example, DVD players and DVD-ROM devices require two types of laser light sources with an oscillation wavelength of 780 nm and an oscillation wavelength of 650 nm so that information can be extracted from both CD and DVD discs. However, the semiconductor laser device including two types of laser light sources has a complicated optical system configuration. Therefore, if laser light sources having two types of wavelengths can be integrated on the same substrate, a great merit such as a reduction in the size of the pickup can be obtained. Even in such a semiconductor laser device in which various laser light sources are integrated on the same substrate, development of higher output of the above-described semiconductor laser device has been studied.

  FIG. 7 is a cross-sectional view showing a configuration of a semiconductor laser element that outputs laser light having an infrared wavelength of 780 nm band having a conventional end face window structure. As shown in FIG. 7, a conventional semiconductor laser device having an end face window structure includes an n-type GaAs substrate 101 inclined at 8 °, an n-type AlGaInP cladding layer 102 formed on the n-type GaAs substrate 101, and an n-type. Quantum well active layer 103 formed on AlGaInP cladding layer 102, p-type AlGaInP first cladding layer 104 formed on quantum well active layer 103, and p formed on p-type AlGaInP first cladding layer 104 P-type GaInP etching stop layer 105, p-type AlGaInP second cladding layer 106 formed in a ridge shape on p-type GaInP etching stop layer 105, and p-type GaInP band formed on p-type AlGaInP second cladding layer 106 Discontinuous relaxation layer 107 and p-type formed on p-type GaInP band discontinuous relaxation layer 107 And a lGaAs diffusion control layer 108.

  Further, the conventional semiconductor laser device includes the p-type GaInP etching stop layer 105, the p-type AlGaInP second cladding layer 106, the p-type GaInP band discontinuous relaxation layer 107, and the p-type AlGaAs diffusion control film 108. An n-type AlInP current confinement layer 109 formed on the p-type, a p-type GaAs contact layer 110 formed on the n-type AlInP current confinement layer 109 and the p-type AlGaAs diffusion control film 108, and an n-type GaAs substrate 101 And the p-type electrode 113 formed on the p-type GaAs contact layer 110. In order to realize the transverse mode control of the laser, the ridge of the p-type AlGaInP second cladding layer 106 is formed in a stripe shape extending in the optical axis direction of the laser beam.

By the way, in the conventional semiconductor laser device, the impurity diffusion region 111 (hatching different from that of the n-type GaAs substrate 101 in FIG. 7 is present in the vicinity of the end face serving as the laser light output face and the end face facing the end face. Area) is provided. Specifically, the upper part of the n-type AlGaInP cladding layer 102, the quantum well active layer 103, the p-type AlGaInP first cladding layer 104, the p-type GaInP etching stop layer 105, the p-type AlGaInP second cladding layer 106, the p-type GaInP band. The impurity diffusion region 111 is obtained by solid-phase diffusing Zn in a direction perpendicular to the substrate surface in the vicinity of the output end face of the discontinuous relaxation layer 107 and the p-type AlGaAs diffusion control film 108 and the end face opposite to the output end face. The end face window structure provided with is formed. In the impurity diffusion region 111, the composition of the quantum well active layer 103 is disordered, and the composition of the well layer and the barrier layer constituting the quantum well active layer 103 is averaged. The area is larger than the excluded area (hereinafter referred to as an impurity non-diffusion area). For example, the photoluminescence wavelength of the laser light emitted from the quantum well active layer 103 is 780 nm in the impurity non-diffusion region, whereas it is 740 nm in the impurity diffusion region 111, and the laser light emitted from the impurity diffusion region 111. Has moved to the short wavelength side by about 80 meV. Therefore, since the impurity diffusion region 111 is transparent to the laser light emitted from the impurity non-diffusion region, the absorption of the laser light at the output end face is remarkably suppressed, and the conventional semiconductor laser device has a stable high output operation. Is achieved.
JP 2002-26447 A

  In the future, the demand for a light source for a high-speed writable optical disk system such as a 48-speed CD-R that has a recording function as well as a reproduction and a DVD that can be recorded at 16-times speed will increase. In this case, a semiconductor laser device used as a light source is required to have a high output operation of at least 200 mW.

  When such a high output operation of 200 mW or more is performed by a semiconductor laser device, even in a semiconductor laser device having an end face window structure, an increase in power consumption during operation and an absorption loss of laser light in the waveguide Due to the heat generated by the increase in the thickness of the active layer, the band gap of the active layer near the output end face is reduced, and the laser light is absorbed at the output end face. As a result, COD (Catastrophic Optical Damage) that destroys the output end face occurs, and it is difficult to guarantee long-term reliability of the semiconductor laser device for several thousand hours or more.

  Therefore, in order to realize a high output operation without causing COD, the diffusion density of the impurity in the impurity diffusion region of the end face window structure is increased, and the band gap of the impurity diffusion region is further expanded, thereby absorbing at the output end face. Further reduction methods are used. However, increasing the diffusion concentration of impurities in the end face window structure increases the effective refractive index difference of the waveguide between the window region and the gain region, so that the coupling loss of laser light at the boundary between the window region and the gain region increases. turn into. As a result, the light converted into the radiation mode as a coupling loss interferes with the output light in the waveguide mode, so that the unimodal shape of the far radiation pattern (hereinafter referred to as FFP (Far Field Pattern)) of the output light is reduced. The problem of being unable to keep occurs.

  If the FFP of the output light is disturbed and the unimodal shape cannot be maintained, the light utilization efficiency of the lens in the optical system of the optical disk system is lowered. Furthermore, the stability of tracking, which is an important signal from the DVD / CD-R, is largely lacking, and the reading of the signal from the disk becomes unstable, causing a serious problem in practical use.

  Reflecting the above problems, the present invention does not cause COD even when operating at high output, and furthermore, the FFP of the output light exhibits good unimodality and stable high output operation. An object of the present invention is to provide a possible semiconductor laser device.

  In order to achieve the above object, a semiconductor laser device of the present invention includes a substrate, a first cladding layer of a first conductivity type formed on the substrate, and a first layer formed on the first cladding layer. Active layer, a second conductivity type second clad layer provided on the first active layer and having a convex first ridge formed thereon, and the second clad layer out of the second clad layer A first current blocking layer formed on an upper surface of a side portion of the first ridge and on a side surface of the first ridge, and a light output end surface from which the first laser beam is output; A first laser element having a second current blocking layer formed on the first current blocking layer in a first region having a longitudinal distance in a first length range; A length of the first ridge from the light output end face of the first active layer. In the second region whose direction distance is in the second length range, an impurity is introduced and a window region whose composition is disordered is formed. In the second region, the first region A current blocking layer is also formed on the upper surface of the first ridge.

  According to this configuration, since the impurity is introduced into the first active layer and the window region having a disordered composition is formed, even when the operation is performed at a high output, it is stable without causing COD. It is possible to perform an operation. Further, the second current blocking layer absorbs the light converted into the radiation mode as a coupling loss at the boundary between the window region and the gain region, and suppresses the interference of the light converted into the radiation mode with the output light. Therefore, it is possible to realize a semiconductor laser device in which the FFP of the output light exhibits good unimodality and is capable of stable high output operation. In addition, since the first current blocking layer is provided in the window region, current injection into the window region can be prevented.

  In the semiconductor laser device of the present invention, it is preferable that the energy gap of the first active layer in the window region is larger than the energy of the first laser beam. Thereby, even if the energy gap of the first active layer in the window region is reduced due to the heat generated by the laser itself during operation, the window region can be kept transparent with respect to the first laser beam. As a result, the first laser beam is less likely to be absorbed in the vicinity of the output end face with a high optical power density, so that the semiconductor laser device of the present invention can operate up to a light output that is thermally saturated without causing COD. It becomes.

  Further, the second current blocking layer preferably absorbs the first laser beam, and more preferably, the energy gap of the second current blocking layer is smaller than the energy of the first laser beam. . As a result, the radiation mode light converted as a coupling loss at the boundary between the window region and the gain region is absorbed by the second current blocking layer, so that the interference with the output light in the waveguide mode is suppressed, and the single peak property Can obtain a good FFP. Further, in the semiconductor laser device of the present invention, it is possible to select a material for the light-absorbing block layer that absorbs laser light according to the oscillation wavelength of the semiconductor laser.

The first current blocking layer preferably includes a dielectric of any one of SiN _x , SiO ₂ , TiO ₂ , and Al ₂ O ₃ or AlInP. As a result, the semiconductor laser device of the present invention can realize an actual refractive index waveguide mechanism, so that the oscillation threshold current and the operating current can be reduced. Further, when forming a current blocking layer made of a dielectric, the number of crystal growths can be reduced as compared with the conventional semiconductor laser device, so that the semiconductor laser device of the present invention is compared with the conventional semiconductor laser device. Manufacturing cost can be reduced.

  Moreover, it is preferable that A <B, where A is the first length and B is the second length. In this case, by setting the width (A) of the second current blocking layer as small as possible within a range in which the unimodality of the FFP of the laser beam can be maintained, the second current blocking layer can emit laser light other than radiation mode light. Absorbing and reducing output can be suppressed. On the other hand, since the spread angle of the FFP depends on the width (B) of the window region, the spread angle of the FFP is adjusted by adjusting the width (B) of the window region in a range larger than that of the second current blocking layer (A). Can be controlled to a desired value.

  According to another aspect of the present invention, there is provided a semiconductor laser device comprising: a first conductivity type third cladding layer formed on the substrate at a predetermined interval from the first laser element; and the third cladding layer. A second active layer formed; a fourth clad layer of a second conductivity type provided on the second active layer and having a convex second ridge formed thereon; and The fourth current blocking layer formed on the upper surface of the side portion of the second ridge and the side surface of the second ridge of the cladding layer, and the light output end face from which the second laser beam is output, A second current ridge having a fifth current blocking layer formed on the fourth current blocking layer in the fifth region in which a longitudinal distance of the second ridge is in a fifth length range; A laser element, and from the light output end face of the second active layer. In the sixth region in which the distance in the longitudinal direction of the second ridge is in the sixth length range, a window region in which impurities are introduced and the composition is disordered is formed. The fourth current blocking layer is also formed on the upper surface of the second ridge, and the first semiconductor laser element and the second semiconductor laser element are monolithically formed on the substrate. It is preferable that they are integrated.

  According to this configuration, in addition to the above-described effects, since one semiconductor laser device is provided with two types of semiconductor laser elements, high output operation can be performed with respect to an information recording medium corresponding to the wavelength of each laser element. A semiconductor laser device that can be stably performed and further downsized can be realized.

  Furthermore, the first laser beam output from the first laser element and the second laser beam output from the second laser element are respectively a red wavelength laser beam and an infrared wavelength laser beam. It is preferable. In this case, it is possible to provide a semiconductor laser device capable of writing on a CD and a DVD with one semiconductor device.

  According to the semiconductor laser device of the present invention, there is provided a semiconductor laser device capable of stable operation without causing COD, exhibiting a good unimodal FFP of output light even when operating at a high output. Can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the configuration of the semiconductor laser device according to the embodiment of the present invention will be described with reference to FIGS. The semiconductor laser device of this embodiment is a monolithic two-wavelength semiconductor laser device having two types of laser elements. FIG. 1A is a top view showing the configuration of the semiconductor laser device of this embodiment. 1B is a cross-sectional view of the semiconductor laser device taken along line Ib-Ib shown in FIG. 1A, and FIG. 1C is a semiconductor laser device taken along line Ic-Ic shown in FIG. FIG.

  As shown in FIGS. 1A and 1B, the semiconductor laser device according to the present embodiment is an n-type substrate made of GaAs or the like whose main surface is a surface inclined by 10 ° in the [011] direction from the (100) plane. 10, a red laser element unit 20 that outputs a laser beam of red wavelength formed on each n-type substrate 10, and an infrared laser element unit 30 that outputs a laser beam of infrared wavelength.

  The red laser element unit 20 includes a first n-type buffer layer 14 made of GaAs or the like formed on the n-type substrate 10 and a first n type made of AlGaInP or the like formed on the first n-type buffer layer 14. Type cladding layer 13, strained quantum well active layer 12 formed on first n-type cladding layer 13, AlGaInP or the like provided on strained quantum well active layer 12 and having a convex ridge formed thereon A first p-type cladding layer 11 of the first p-type cladding layer 11, a first p-type protection layer 15 made of GaInP or the like formed on the upper surface of the ridge, and a first p-type protection layer. And a first p-type contact layer 16 made of GaAs or the like formed on the layer 15. Here, although not shown, in the strained quantum well active layer 12, the first guide layer, the first well layer, the first barrier layer, the first well layer, the first barrier layer, the first The well layer and the second guide layer are laminated in order from the bottom. For example, AlGaInP is used as the first guide layer, the second guide layer, and the first barrier layer, and GaInP is used as the first well layer.

  Further, the red laser element portion 20 is formed on the upper surface of the first p-type cladding layer 11, the side surfaces of the first p-type cladding layer 11, the first p-type protective layer 15, and the first p-type contact layer 16. Are provided with a first current blocking layer 1 made of a dielectric. Here, the first current blocking layer 1 includes the first current blocking layer 1 in a part or all of the window regions 4a and 4b provided in the vicinity of an end surface serving as an output surface of the laser beam (hereinafter referred to as an output end surface). 1 is also formed on the upper surface of the p-type contact layer 16 (see FIG. 1C), and prevents current from being injected into the window regions 4a and 4b.

  As shown in FIG. 1C, the red laser element portion 20 includes a first light-absorbing current blocking layer 3 formed on the first current blocking layer 1 in the vicinity of the output end face. . Here, the material used for the first light-absorbing current blocking layer 3 is preferably a material that absorbs laser oscillation light. Natural vulcanized silicon-based carbon black absorbing material that absorbs light of all wavelengths, amorphous silicon, GaAs It is preferable that it is any material of these.

  On the other hand, the infrared laser element section 30 is made of a second n-type buffer layer 24 made of GaAs or the like formed on the n-type substrate 10 and AlGaInP or the like formed on the second n-type buffer layer 24. Second n-type cladding layer 23, quantum well active layer 22 formed on second n-type cladding layer 23, and provided on quantum well active layer 22, with a convex ridge formed on the top A second p-type cladding layer 21 made of AlGaInP or the like; a second p-type protective layer 25 made of GaInP or the like formed on the upper surface of the ridge in the second p-type cladding layer 21; and a second p And a second p-type contact layer 26 made of GaAs or the like formed on the mold protection layer 25. Here, although not shown, in the quantum well active layer 22, the third guide layer, the second well layer, the second barrier layer, the second well layer, the second barrier layer, the second The well layer and the fourth guide layer are laminated in order from the bottom. For example, AlGaAs is used as the third guide layer, the fourth guide layer, and the second barrier layer, and GaAs is used as the second well layer.

  Further, the infrared laser element section 30 includes the upper surface of the second p-type cladding layer 21, the second p-type cladding layer 21, the second p-type protective layer 25, and the side surfaces of the second p-type contact layer 26. A second current blocking layer 2 made of a dielectric is provided thereon. Here, the second current blocking layer 2 is also formed on the upper surface of the second p-type contact layer 26 in part or all of the window regions 3a and 3b provided in the vicinity of the output end face. (See FIG. 1 (c)), and current injection into the window regions 3a and 3b is prevented.

  Then, as shown in FIG. 1C, the infrared laser element portion 30 has the second light formed on the second current blocking layer 2 in the vicinity of the output end face, similarly to the red laser element portion 20. An absorptive current blocking layer 4 is provided. Here, the material used for the second light-absorbing current blocking layer 4 is preferably a material that absorbs laser oscillation light, such as a natural vulcanized silicon-based carbon black absorbing material that absorbs light of all wavelengths. it can.

  The ridges of the first p-type cladding layer 11 and the ridges of the second p-type cladding layer 21 provided in the red laser element unit 20 and the infrared laser element unit 30 are respectively red laser light and red wavelength. It is formed in a stripe shape extending in the direction of the optical axis of the laser light having the outer wavelength.

  The output end faces of the red laser element section 20 and the infrared laser element section 30 are coated with a low reflection film, and the end faces opposite to the output end faces are coated with a high reflection film. In addition, in the semiconductor laser device of this embodiment, the length of the laser resonator is set to 1300 μm or more in order to suppress an increase in leakage current during high temperature operation and reduce the operating current density.

  As shown in FIG. 1A, the semiconductor laser device of this embodiment includes window regions 3a and 4a in the vicinity of the output end surface, and includes window regions 3b and 4b in the vicinity of the end surface facing the output end surface. It has an end face window structure. In the window regions 3a and 3b, the composition of the quantum well active layer 22 is disordered by diffusing impurities such as Zn and Si into the quantum well active layer 22 in the infrared laser element section 30. The impurity implanted into the quantum well active layer 22 is diffused to a part of the second p-type cladding layer 21 and the second n-type cladding layer 23. Similarly, in the window regions 4a and 4b, the composition of the strained quantum well active layer 12 is disordered by impurity diffusion such as Zn or Si. The impurity implanted into the strained quantum well active layer 12 is diffused to a part of the first p-type cladding layer 11 and the first n-type cladding layer 13. As a result, the energy gap of the quantum well active layer in the window region is larger than the energy of the laser beam, so that the window regions 3a, 3b, 4a, and 4b are in a state transparent to the laser beam. Here, the width in the longitudinal direction of the ridge from the output end face of the window regions 3a and 3b is set to Lw1, and the width of the ridge from the output end face of the first light absorbing current blocking layer 3 and the second light absorbing current blocking layer 4 described above. The width in the longitudinal direction is defined as Lw2.

  The feature of the semiconductor laser device of this embodiment is that it has a double hetero structure having a window region on the end face, and in the vicinity of the output end face, the first light-absorbing current blocking layer 3 and the second The light absorbing current blocking layer 4 is provided. Hereinafter, the effect of this light-absorbing current blocking layer will be described with reference to FIGS.

  FIG. 2 shows a case where the width Lw1 of the window region 4a is changed when the first light-absorbing current blocking layer 3 is not formed on the first current blocking layer 1 provided in the red laser element section 20. It is a figure which shows the measurement result of the far radiation pattern (FFP) of the output light at the time. In addition, the measurement result when operating continuously at an output of 5 mW at room temperature is shown. 2A to 2D show the FFP of the laser light of the red laser element when Lw1 is 5 μm, 20 μm, 40 μm, and 60 μm, respectively. From FIG. 2, it can be seen that only when Lw1 is 5 μm, an FFP with good unimodality is obtained.

  The window region is formed so that the energy gap of the active layer is sufficiently larger than the energy of the laser beam. Therefore, even if the energy gap of the active layer in the window region is reduced due to heat generation of the laser itself during operation, Auger recombination at the output end face of the laser beam, or heat generation due to energy loss in which light is absorbed in the band, The window region can be kept transparent to the laser beam. In other words, the laser light can maintain a wavelength longer than the wavelength corresponding to the energy gap of the active layer in the window region, and is thus less likely to be absorbed in the vicinity of the output end face having a high optical power density. For this reason, the semiconductor laser device in which the window region is formed can operate to a light output that is thermally saturated without generating COD.

  However, when the impurity diffusion concentration of the active layer is increased in order to sufficiently widen the energy gap of the active layer in the window region, the effective refractive index difference between the waveguides in the window region and the gain region increases. As a result, the coupling loss of the laser beam at the boundary between the window region and the gain region becomes large, and light converted into a radiation mode (hereinafter referred to as radiation mode light) is generated as the coupling loss, and the radiation mode light is guided. Since it interferes with the output light in the wave mode, the FFP of the output light cannot maintain a unimodal shape. Also in the red laser element portion 20 in which the first light-absorbing current blocking layer 3 is not formed, as shown in FIG. 2, when the width Lw1 of the window region is as short as 5 μm, the radiation mode light is separated from the optical axis. Since the light is emitted in different directions, the interference with the output light in the waveguide mode is suppressed, and the FFP is not disturbed by the interference. However, when Lw1 is as long as 20 μm or more, the radiation mode light propagates through the cladding layer and increases the component in the optical axis direction, so that it interferes with the output light in the waveguide mode and the FFP is disturbed.

  Here, in order to realize FFP with good unimodality, it is preferable that the width Lw1 of the window region 4a is short. However, if Lw1 is too short, the accuracy of mask alignment in the process of manufacturing the element and the cleavage are reduced. Due to variations in position process, the window region 4a may disappear when the elements are separated by cleavage. Therefore, the width Lw1 of the window region 4a is preferably at least longer than the range of variation due to the element manufacturing process, and more preferably 10 μm or more in order to suppress COD.

  Note that the sizes of the window regions 3b and 4b in the vicinity of the end surface facing the output end surface are not necessarily the same as the sizes of the window regions 3a and 4a on the output end surface side, and may be different from each other. Actually, in order to obtain the desired FFP by adjusting the beam divergence angle of the semiconductor laser in the infrared laser element section 30, the width Lw1 of the window region 3a is adjusted. In this case, the width Lw1 of the window region 3a and the vicinity of the end face are adjusted. The width of the window region 3b (longitudinal direction of the ridge) may be different. This also applies to the red laser element unit 20.

  Next, the effect of the first light absorbing current blocking layer 3 will be described with reference to FIG. FIGS. 3A to 3D are diagrams showing measurement results of FFP of the output light when the first light-absorbing current blocking layer 3 is formed in the red laser element portion 20. In addition, the measurement result when operating continuously at an output of 5 mW at room temperature is shown. 3A, 3C, and 3D, the width Lw2 of the first light-absorbing current blocking layer 3 is 5 μm, and the width Lw1 of the first current blocking layer 1 is 20 μm, 40 μm, and 60 μm, respectively. It is a measurement result of FFP at the time of changing. Compared with the above-described FIGS. 2B, 2C, and 2D, in each case, an FFP with good unimodality is obtained. FIG. 3B shows the results when Lw2 is 10 μm and Lw1 is 20 μm. Also in this case, FFP shows good unimodality, and no unimodal deterioration is observed. From this, it has been found that by providing the first light-absorbing current blocking layer 3 having a width of at least 5 μm in the vicinity of the output end face, it is possible to suppress the deterioration of unimodality of the FFP. This is because the radiation mode light propagated through the cladding layer is absorbed by the first light-absorbing current blocking layer 3, and interference with the waveguide mode output light is suppressed.

  The width Lw2 of the first light-absorbing current blocking layer 3 is preferably longer from the viewpoint of unimodality of FFP. However, if Lw2 becomes too long, the loss of the waveguide increases and the oscillation threshold current value is increased. And an increase in operating current value. The optimum range of Lw2 will be described with reference to FIG.

  FIG. 4 is a diagram showing the relationship between the width Lw2 of the first light-absorbing current blocking layer 3 and the oscillation threshold current value of the red laser element portion 20 in the present embodiment. The width Lw1 of the window region 4a is a constant 20 μm, and Lw2 is changed from 0 μm to 30 μm. As shown in FIG. 4, it can be seen that when Lw2 exceeds 10 μm, the oscillation threshold current value suddenly increases. This is because, since the first light-absorbing current blocking layer 3 absorbs laser light, the loss of the waveguide increases as Lw2 increases, and the gain necessary for laser oscillation increases. Therefore, in the semiconductor laser device of this embodiment, Lw2 is preferably 10 μm or less.

  2, 3, and 4 show the measurement results of the FFP of the output light and the oscillation threshold current value in the red laser element unit 20, the infrared laser element is used in the semiconductor laser device of this embodiment. Similar results are obtained in the section 30. The widths of the first light-absorbing current blocking layer 3 provided in the red laser element section 20 and the second light-absorbing current blocking layer 4 provided in the infrared laser element section 30 are both Lw2 and the above-described width. However, the widths of the light absorption current blocking layers may not be the same.

  Next, current-light output characteristics in the semiconductor laser device of this embodiment will be described with reference to FIG. 5A and 5B are diagrams showing current-light output characteristics when the red laser element unit 20 and the infrared laser element unit 30 are continuously operated at room temperature, respectively. Lw1 is 20 μm, and Lw2 is 5 μm. As shown in FIGS. 5A and 5B, the red laser element unit 20 and the infrared laser element unit 30 operate without generating COD even at a high output of 300 mW or more, and have excellent linearity. It can be seen that the light output characteristics are good.

  Further, FIG. 6 is a diagram showing FFP of each output light from the red laser element unit 20 and the infrared laser element unit 30 when the semiconductor laser device of this embodiment is continuously operated at 5 mW and 100 mW at room temperature, respectively. It is. Lw1 is 20 μm, and Lw2 is 5 μm. As shown in FIGS. 6A and 6B, the FFP of each output light from the red laser element unit 20 and the infrared laser element unit 30 has good unimodality in any operating state. I understand.

  As described above, the semiconductor laser device of the present embodiment has a double hetero structure having a window region on the end face, and further, the first light-absorbing current blocking layer 3 and the second light in the vicinity of the output end face. By providing the absorptive current blocking layer 4, high light output can be realized, and furthermore, laser light in the vicinity of the output end face can be absorbed, so that the FFP of the output light exhibits a good single peak. Even when a high output operation is performed, recording and reproduction can be performed stably without causing COD.

  Further, the semiconductor laser device of this embodiment has a monolithic structure in which the red laser element unit 20 and the infrared laser element unit 30 are provided on the same substrate. Thus, in addition to the above-described effects, recording and reproduction are performed on, for example, a CD and a DVD corresponding to the wavelength of the output light of the red laser element and the wavelength of the output light of the infrared laser element with one semiconductor laser device. In addition, a miniaturized semiconductor laser device can be realized.

  In the semiconductor laser device of the present embodiment, it is preferable that the energy gap between the strained quantum well active layer 12 and the quantum well active layer 22 in the window region is larger than the red wavelength laser beam and the infrared wavelength laser beam, respectively. . As a result, even if the energy gap between the strained quantum well active layer 12 and the quantum well active layer 22 in the window region is reduced due to heat generated by the laser itself during operation, the window region remains transparent to each laser beam. Can keep. As a result, each laser beam is less likely to be absorbed in the vicinity of the output end face where the optical power density is high, so that the semiconductor laser device of this embodiment can operate up to a light output that is thermally saturated without causing COD. Become.

In the semiconductor laser device of the present embodiment, the energy gap between the first light-absorbing current blocking layer 3 and the second light-absorbing current blocking layer 4 is preferably smaller than the energy of the laser beam. As a result, radiation mode light converted as a coupling loss at the boundary between the window region and the gain region is absorbed by the light-absorbing block layer, so that interference with the waveguide mode output light is suppressed, and unimodality is achieved. Good FFP can be obtained. Furthermore, it is possible to select a material for the light-absorbing block layer that absorbs the laser beam according to the oscillation wavelength of the laser beam of the semiconductor laser device. Further, by adjusting the composition of the semiconductor layer constituting the quantum well active layer, it becomes easy to design the amount of laser light absorption in the light absorbing block layer within a desired range. In the semiconductor laser device of the present embodiment, AlInP, GaAs, Al _x Ga _1-x N, or the like can be used as the semiconductor layer such as the strained quantum well active layer 12, the quantum well active layer 22, and each cladding layer. However, the present invention is not limited to this.

In the semiconductor laser device of the present embodiment, the first current blocking layer 1 is made of SiN _x (silicon nitride), SiO ₂ (silicon oxide), TiO ₂ (titanium oxide) Al ₂ O ₃ (aluminum oxide). It is preferable that any dielectric or AlInP is included. As a result, a semiconductor laser device having an actual refractive index waveguide mechanism can be realized, so that the threshold current and the operating current can be reduced. Further, when forming a current blocking layer made of a dielectric, the number of crystal growths can be reduced as compared with the conventional semiconductor laser device, so the semiconductor laser device of this embodiment is different from the conventional semiconductor laser device. In comparison, the manufacturing cost can be reduced.

  In the semiconductor laser device of this embodiment, it is preferable that Lw1> Lw2. In this case, the width (Lw2) of the first light-absorbing current blocking layer 3 and the second light-absorbing current blocking layer 4 that absorbs the laser light is made as small as possible within a range in which the unimodality of the FFP of the laser light can be maintained. By setting, it can suppress that each light absorptive current block layer absorbs laser beams other than radiation mode light, and reduces an output. On the other hand, since the spread angle of FFP depends on the width Lw1 of the window region, it is possible to control the spread angle of FFP to a desired value by adjusting the width Lw1 of the window region in a range larger than Lw2. .

  In the semiconductor laser device of this embodiment, an example of a configuration in which two types of semiconductor lasers are monolithically integrated on the substrate has been described. However, the present invention is not limited to this, and the red laser element, the infrared A configuration including a semiconductor laser element having a single wavelength, such as a laser element or a blue laser element, may be used. Even in this case, it is possible to realize a semiconductor laser device that operates without generating COD at high output and exhibits an FFP with good unimodality.

  In the semiconductor laser device of the present embodiment, an example of a structure in which an n-type cladding layer is formed on an n-type substrate and a p-type cladding layer is formed on an active layer has been described, but the present invention is not limited thereto. Instead, a structure in which a p-type cladding layer is formed on a p-type substrate and an n-type cladding layer is formed on an active layer may be used.

  The semiconductor laser device of the present invention is useful, for example, for a semiconductor laser device used as a light source for a pickup of an optical disk device, a light source of an electronic device, an information processing device, or the like.

(A) is a top view which shows the structure of the semiconductor laser apparatus concerning this embodiment of this invention, (b), (c) is a cross section which shows the structure of the semiconductor laser apparatus concerning this embodiment of this invention. FIG. (A)-(d) is a figure which shows the measurement result of FFP of output light in case the 1st light absorptive current block layer is not formed. (A)-(d) is a figure which shows the measurement result of FFP of output light in case the 1st light absorptive current block layer which concerns on this embodiment is formed. It is the figure which showed the relationship between the oscillation threshold current value of the 1st light absorptive current block layer and red laser element part in this embodiment. (A), (b) is a figure which shows the electric current-light output characteristic at the time of operating the red laser element part and infrared laser element part which concern on this embodiment continuously at room temperature. (A)-(d) is the measurement result of FFP of each output light from a red laser element part and an infrared laser element part when the semiconductor laser device of this embodiment is continuously operated at 5 mW and 100 mW at room temperature, respectively. FIG. It is sectional drawing which shows the structure of the conventional semiconductor laser apparatus.

Explanation of symbols

1 First current blocking layer
2 Second current blocking layer
3 1st light absorption current block layer
3a, 3b, 4a, 4b Window area
4 Second light absorbing current blocking layer
10 n-type substrate
11 First p-type cladding layer
12 Strained quantum well active layer
13 First n-type cladding layer
14 First n-type buffer layer
15 First p-type protective layer
16 First p-type contact layer
20 Red laser element
21 Second p-type cladding layer
22 Quantum well active layer
23 Second n-type cladding layer
24 Second n-type buffer layer
25 Second p-type protective layer
26 Second p-type contact layer
30 Infrared laser element
101 n-type GaAs substrate
102 n-type AlGaInP cladding layer
103 quantum well active layer
104 p-type AlGaInP first cladding layer
105 p-type GaInP etching stop layer
106 p-type AlGaInP second cladding layer
107 p-type GaInP band discontinuous relaxation layer
108 p-type AlGaAs diffusion control film
109 n-type AlInP current confinement layer
110 p-type GaAs contact layer
111 Impurity diffusion region
112 n-side electrode
113 p-type electrode

Claims (16)

A substrate,
A first conductivity type first clad layer formed on the substrate; a first active layer formed on the first clad layer; and provided on the first active layer; A second clad layer of a second conductivity type in which a convex first ridge is formed; an upper surface of a side portion of the first ridge of the second clad layer; and a side surface of the first ridge The first current blocking layer formed thereon and the first region in which the distance in the longitudinal direction of the first ridge from the light output end face from which the first laser beam is output is in the first length range And a first laser element having a second current blocking layer formed on the first current blocking layer,
In the second region of the first active layer, in which the distance in the longitudinal direction of the first ridge from the light output end face is in the second length range, impurities are introduced and the composition becomes disordered. A window region is formed,
In the second region, the first current blocking layer is also formed on the upper surface of the first ridge.   2. The semiconductor laser device according to claim 1, wherein an energy gap of the first active layer in the window region is larger than an energy of the first laser beam.   3. The semiconductor laser device according to claim 1, wherein the second current blocking layer absorbs the first laser beam. 4.   4. The semiconductor laser device according to claim 3, wherein an energy gap of the second current blocking layer is smaller than an energy of the first laser beam. Said first current blocking layer, SiN _X, or the dielectric _{SiO 2, TiO 2, Al 2} O 3 or any one of claims 1 to 4, characterized in that it contains AlInP 1 The semiconductor laser device described in 1.   The second current blocking layer includes at least one of amorphous silicon and GaAs, or a naturally vulcanized silicon-based carbon black absorbing material. The semiconductor laser device described.   7. The semiconductor laser device according to claim 1, wherein A <B, where A is the first length and B is the second length. 8. In the third region in which the first laser element has a third distance in the longitudinal direction of the first ridge from an end surface facing the light output end surface, the first current blocking layer A third current blocking layer formed thereon;
Impurities are also introduced into a fourth region of the first active layer in which the distance in the longitudinal direction of the first ridge is in the fourth length range from the end surface facing the light output end surface, A window region with a disordered composition is formed,
8. The semiconductor laser according to claim 1, wherein in the fourth region, the first current blocking layer is also formed on an upper surface of the first ridge. 9. apparatus.   9. The semiconductor laser device according to claim 8, wherein in the first laser element, the second length and the fourth length are different from each other. A third clad layer of a first conductivity type formed on the substrate at a predetermined interval from the first laser element; a second active layer formed on the third clad layer; A fourth clad layer of a second conductivity type provided on the second active layer and having a convex second ridge formed thereon; and of the second ridge of the fourth clad layer A distance in the longitudinal direction of the second ridge from the fourth current blocking layer formed on the upper surface of the side portion and the side surface of the second ridge and the light output end surface from which the second laser light is output. A second laser element having a fifth current blocking layer formed on the fourth current blocking layer in the fifth region in a fifth length range;
Of the second active layer, impurities are introduced and the composition is disordered in the sixth region in which the distance in the longitudinal direction of the second ridge from the light output end face is in the sixth length range. Window region is formed,
In the sixth region, the fourth current blocking layer is also formed on the upper surface of the second ridge,
The semiconductor laser device according to claim 1, wherein the first semiconductor laser element and the second semiconductor laser element are monolithically integrated on the substrate.   The first laser beam output from the first laser element and the second laser beam output from the second laser element are a red wavelength laser beam and an infrared wavelength laser beam, respectively. 11. The semiconductor laser device according to claim 10, wherein   12. The semiconductor laser device according to claim 10, wherein an energy gap of the second active layer in the window region is larger than an energy of the second laser beam.   The semiconductor laser device according to claim 10, wherein the fifth current blocking layer absorbs the second laser beam.   The semiconductor laser device according to claim 13, wherein an energy gap of the fifth current blocking layer is smaller than an energy of the second laser beam. It said fourth current blocking layer, SiN _X, or the dielectric _{SiO 2, TiO 2, Al 2} O 3 or any one of claims 10 to 14, characterized in that it contains AlInP 1 The semiconductor laser device described in 1. The fifth current blocking layer includes at least one of amorphous silicon and GaAs materials, or a natural vulcanized silicon-based carbon black absorbing material. The semiconductor laser device described.

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