JP2015012018A - Semiconductor laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a semiconductor laser element emitting multimode laser light.SOLUTION: In a semiconductor laser element 1, an active layer 6 is arranged between a first conductivity type semiconductor layer 4 and a second conductivity type semiconductor layer 5 that has a stripe-shaped stripe part 10 extending in one direction. The semiconductor laser element 1 emits multimode laser light from an end surface 15a of the active layer 6 to which a current is injected from an electrode 8 provided on the stripe part 10 via the stripe part 10. The semiconductor laser element 1 is provided with a modulator 12 for reducing a current injection amount of the active layer 6 smaller than that at the circumference.

Description

  The present invention relates to a semiconductor laser element that emits multimode laser light.

  Semiconductor laser elements that emit laser light are widely used as pickup light sources for optical information recording / reproducing apparatuses (optical disks). For example, an AlGaInP-based red laser with a wavelength of 650 nm is used for DVD, and a blue-violet laser with a wavelength of 405 nm is used for Blu-ray (registered trademark) disk. A semiconductor laser element for such an application is required to emit a laser beam of a single transverse mode (single mode).

  On the other hand, since a semiconductor laser element can emit light having a high light density and emit a high-purity color, it is attracting attention as an excitation light source for illumination and processing. A semiconductor laser element for such applications is generally required to emit a laser beam with a very high output such as several watts to several tens of watts. For this reason, a wide stripe type semiconductor laser element that emits a plurality of transverse mode (multi-mode) laser beams is generally used.

  A wide stripe type multi-mode semiconductor laser device has a light output portion that is several to several tens times larger than a single-mode semiconductor laser device, so that a high output can be obtained. For example, the output specification of the semiconductor laser element is several hundreds mW for optical disk light source use, but 10 to 100 times that for excitation light source use.

  At this time, the specification of the lifetime of the semiconductor laser element is about several thousand hours to 10,000 hours for the light source application of the optical disc, whereas it is tens of thousands to 100,000 hours for the excitation light source application. For this reason, a semiconductor laser element for use as an excitation light source is advantageous in extending the life due to the wide stripe structure, but is required to have higher reliability by preventing destruction due to heat generation or the like.

  A conventional semiconductor laser element with improved heat dissipation is disclosed in Patent Document 1. FIG. 15 is a schematic perspective view of the semiconductor laser device. In the semiconductor laser element 101, a semiconductor laminated film 103 made of a nitride semiconductor necessary for laser oscillation is formed on a substrate. The semiconductor stacked film 103 has an active layer 106 disposed between the n-type semiconductor layer 104 and the p-type semiconductor layer 105.

  A p-side electrode 108 is formed on the upper surface of the semiconductor stacked film 103. An n-side electrode 109 is formed on the protruding portion 104 a that protrudes laterally from the lower portion of the n-type semiconductor layer 104. A wire 110 is connected to the p-side electrode 108, and a wire 111 is connected to the n-side electrode 109.

  A striped (elongated) stripe portion (not shown) is formed in the semiconductor laminated film 103 above the active layer 106. Current is injected into the active layer 106 from the p-side electrode 108 through the stripe portion, and a stripe-shaped optical waveguide 115 (oscillation region) is formed in the active layer 106. Laser light is emitted from the emission portion 115 a on the end face of the optical waveguide 115.

  At this time, the plurality of wires 110 are connected to the p-side electrode 109 along the striped optical waveguide 115. Thereby, the heat generated in the optical waveguide 115 can be radiated through the plurality of wires 110. Therefore, destruction due to heat of the semiconductor laser element 101 can be prevented, and reliability can be improved.

Japanese Patent No. 3618989 (pages 3 to 8, FIG. 1)

  However, according to the conventional semiconductor laser device 101 described above, there is a case where the lifetime specification is not satisfied when the wide stripe type is used for the excitation light source, and the reliability cannot be sufficiently improved.

  It is an object of the present invention to provide a multimode semiconductor laser device that can reliably improve reliability.

  In order to achieve the above object, the present invention provides an active layer disposed between a first conductivity type semiconductor layer and a second conductivity type semiconductor layer having a stripe-like stripe portion extending in one direction, on the stripe portion. In a semiconductor laser device that emits multimode laser light from the end face of the active layer into which current is injected from the electrode provided on the stripe portion through the stripe portion, the modulation unit that reduces the current injection amount of the active layer from the surroundings It is characterized by providing.

  According to the present invention, in the semiconductor laser device configured as described above, the modulation portion is formed by a groove portion for digging the semiconductor laminated film on the stripe portion.

  According to the present invention, in the semiconductor laser device configured as described above, the depth of the groove is smaller than the height of the stripe portion.

  According to the present invention, in the semiconductor laser device configured as described above, a dielectric is embedded in the groove.

  According to the present invention, in the semiconductor laser device having the above configuration, the modulation section is formed away from both end faces of the stripe section.

  According to the present invention, in the semiconductor laser device configured as described above, the modulation portion is formed by a through-hole penetrating the electrode and facing the stripe portion.

  According to the present invention, in the semiconductor laser device configured as described above, the modulation section is arranged symmetrically with respect to a center line that bisects the width direction of the stripe section.

  According to the present invention, in the semiconductor laser device configured as described above, a plurality of regions divided in the width direction by the modulation unit are formed at equal intervals on the stripe unit.

  According to the present invention, in the semiconductor laser device configured as described above, the modulation section has a length of 5% or more with respect to the stripe section in the longitudinal direction of the stripe section.

  According to the present invention, the modulation unit that reduces the current injection amount of the active layer is provided below the surroundings. Therefore, the high-order mode of the horizontal transverse mode is limited in the waveguide region partitioned by the modulation unit, and the low-order mode is changed. To be emphasized. This prevents the formation of a region having a high local light intensity on the emission surface due to the superposition of higher-order modes. Therefore, the generation of COD can be prevented and the reliability of the semiconductor laser element can be improved.

The perspective view which shows the semiconductor laser element of 1st Embodiment of this invention. The top view which shows the semiconductor laser element of 1st Embodiment of this invention The front view which shows the epitaxial growth process of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the state at the time of the resist formation of the ridge part formation process of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the state at the time of the etching of the ridge part formation process of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the state at the time of film-forming of the embedded layer formation process of the manufacturing method of the semiconductor laser element of 1st Embodiment of this invention The front view which shows the state at the time of the etching mask removal of the embedded layer formation process of the manufacturing method of the semiconductor laser element of 1st Embodiment of this invention Front sectional drawing which shows the state at the time of the etching mask formation of the groove part formation process of the manufacturing method of the semiconductor laser element of 1st Embodiment of this invention Front sectional drawing which shows the state at the time of the etching of the groove part formation process of the manufacturing method of the semiconductor laser element of 1st Embodiment of this invention Front sectional drawing which shows the electrode formation process of the manufacturing method of the semiconductor laser element of 1st Embodiment of this invention Front sectional view showing a semiconductor laser device according to a second embodiment of the present invention. The top view which shows the semiconductor laser element of 2nd Embodiment of this invention Front sectional view showing a semiconductor laser device according to a third embodiment of the present invention. The top view which shows the semiconductor laser element of 4th Embodiment of this invention A perspective view showing a conventional semiconductor laser device

<First Embodiment>
In describing the embodiment of the present invention, the result of failure analysis of the conventional semiconductor laser device 101 shown in FIG. 15 will be described. As a result of performing a reliability test of the multimode semiconductor laser device 101 formed in the wide stripe type, the semiconductor laser device 101 that was destroyed in about 1000 hours was included.

  When the destroyed semiconductor laser device 101 is analyzed, COD (catastrophic optical damage) is generated in the emitting portion 115a. Further, COD is generated not in the entire width direction of the optical waveguide 115 but in a part of the region, and is generated in different positions depending on each semiconductor laser element 101. COD occurs when the light intensity at the emitting portion 115a is extremely strong.

  On the other hand, as a result of producing a single-mode semiconductor laser element in the same manner and conducting a reliability test, no breakdown occurred in about 1000 hours.

  Therefore, the light density was calculated on the assumption that the light intensity of the emitting portion 115a is constant within the width of the optical waveguide 115, and the light densities of the single mode and multimode semiconductor laser elements were compared. As a result, it was found that the optical density of the multimode semiconductor laser device 101 is lower than that of the single mode semiconductor laser device.

  Therefore, it is considered that there is a region where the light intensity is partially high on the emission portion 115a of the multimode semiconductor laser element 101, and the portion is broken. In addition, since the COD generation position is not constant, it is considered that the region where the light intensity is high changes depending on various conditions such as the heat balance and the situation in the optical waveguide (light scattering and gain variation).

  An embodiment of the present invention based on the above analysis results will be described below with reference to the drawings. 1 and 2 are a perspective view and a top view of the semiconductor laser device of the first embodiment. The semiconductor laser device 1 has a nitride-based semiconductor multilayer film 3 epitaxially grown on the upper surface 2a of a substrate 2 made of a semiconductor such as n-type GaN having a thickness of 100 μm, for example.

  The substrate 2 may be formed of other materials, or may be formed of a mixed crystal semiconductor composed of two or more of GaN, InN, and AlN. Further, the substrate 2 may be formed of a III-V group compound (for example, GaAs, GaP, etc.) other than sapphire, spinel, SiC, Si, and nitride.

  The semiconductor multilayer film 3 is formed by disposing an active layer 6 between an n-type semiconductor layer 4 (first conductive semiconductor layer) and a p-type semiconductor layer 5 (second conductive semiconductor layer). The n-type semiconductor layer 4 is formed by sequentially laminating a lower contact layer 4a, a lower cladding layer 4b, and a lower guide layer 4c on the (001) plane of the substrate 2.

The lower contact layer 4a provided on the substrate 2 is formed of n-type GaN having a thickness of about 0.1 μm to about 10 μm (for example, about 4 μm). The lower cladding layer 4b provided on the lower contact layer 4a is formed of n-type Al _0.05 Ga _0.95 N having a thickness of about 0.5 μm to about 3.0 μm (for example, about 2 μm). The lower guide layer 4c provided on the lower cladding layer 4b is formed of n-type GaN having a thickness of about 0.2 μm or less (for example, about 0.1 μm).

The active layer 6 is provided on the lower guide layer 4c and has, for example, a multiple quantum well (MQW) structure in which three quantum well layers (not shown) and four barrier layers (not shown) are alternately stacked. The quantum well layer is made of, for example, In _x1 Ga _1-x1 N having a thickness of about 6 nm. The barrier layer is made of, for example, In _x2 Ga _{1 -x2} N (x1> x2) having a thickness of about 8 nm. As examples of x1 and x2, x1 = 0.05 to 0.15 and x2 = 0 to 0.1.

The p-type semiconductor layer 5 is provided on the active layer 6, and is formed by laminating an evaporation preventing layer 5a, an upper guide layer 5b, an upper cladding layer 5c, and an upper contact layer 5d in order from the substrate 2 side. The evaporation preventing layer 5a provided on the active layer 6 is formed of p-type Al _0.3 Ga _0.7 N having a thickness of about 0.02 μm or less (for example, about 0.01 μm). The upper guide layer 5b provided on the evaporation prevention layer 5a is formed of p-type GaN having a thickness of about 0.2 μm or less (for example, 0.01 μm).

The upper cladding layer 5c provided on the upper guide layer 5b is made of p-type Al _0.05 Ga _0.95 N. The upper contact layer 5d is provided on the convex portion of the upper cladding layer 5c that forms the ridge portion 10 described later, and is formed of p-type GaN having a thickness of about 0.01 μm to 1 μm (for example, 0.05 μm).

  A striped (elongated) ridge portion 10 (stripe portion) extending in a direction perpendicular to the emission surface 1 a is provided on the p-type semiconductor layer 5. The ridge portion 10 is formed by being dug up to an intermediate position in the thickness direction of the upper cladding layer 5c. An optical waveguide 15 made of a resonator is formed by a stripe-shaped region facing the ridge portion 10 of the active layer 6, and laser light is emitted from the emission portion 15 a exposed on the emission surface 1 a of the optical waveguide 15.

  Whether the semiconductor laser device 1 is driven in a single horizontal mode or a multi-mode in the horizontal transverse mode is determined by the width W of the ridge portion 10, the wavelength of the laser light, and the refractive index of the optical waveguide 15. For example, the nitride semiconductor laser device 1 having a wavelength of 405 nm is driven in a single mode when the width W of the ridge portion 10 is about 2 μm or less, and is driven in a multimode when the width exceeds about 2 μm. The semiconductor laser device 1 of the present embodiment is formed in a wide stripe type in which the width W of the ridge portion 10 is 5 to 200 μm (for example, 15 μm) at the bottom, and emits multimode laser light.

  A groove 12 extending in the longitudinal direction of the ridge 10 is formed in the upper surface of the ridge 10. The ridge portion 10 is divided in the width direction by the groove portion 12. A plurality of groove portions 12 are provided in the width direction of the ridge portion 10, but one groove portion 12 may be provided, or a plurality of groove portions 12 may be provided in the longitudinal direction of the ridge portion 10. Further, a dielectric film may be embedded in the groove 12.

A buried layer 7 is provided on the semiconductor laminated film 3 excluding the upper surface of the ridge portion 10. The buried layer 7 is formed of an insulating material such as SiO ₂ , SiN, Al ₂ O ₃ , or ZrO ₂ . Both side surfaces of the ridge portion 10 are covered with the buried layer 7, and light confinement in the horizontal transverse mode and the vertical transverse mode can be performed.

  A p-side electrode 8 for injecting carriers from the upper surface of the ridge portion 10 is formed on the upper contact layer 5 d and the buried layer 7. The p-side electrode 8 is in ohmic contact with the upper contact layer 5d. As a material for forming the p-side electrode 8, a metal such as Ni, Pd, Pt, or Au, or a laminate including these metals can be used.

  An n-side electrode 9 for injecting carriers is formed on the lower surface 2 b of the substrate 2. The n-side electrode 9 is in ohmic contact with the substrate 2. As a material for forming the n-side electrode 9, a metal such as Hf, Ti, Al, W, or a laminate including these metals can be used.

  Next, a method for manufacturing the semiconductor laser element 1 will be described. The semiconductor laser device 1 is formed by sequentially performing an epitaxial growth step, a ridge portion forming step, a buried layer forming step, a groove portion forming step, an electrode forming step, an end face coat film forming step, and a cutting step.

  FIG. 3 is a front view showing an epitaxial formation step. In the epitaxial growth step, the semiconductor multilayer film 3 is epitaxially grown on the wafer-like substrate 2 made of n-type GaN by MOCVD (Metal Organic Chemical Vapor Deposition) or the like.

  That is, the lower contact layer 4a, the lower cladding layer 4b, and the lower guide layer 4c are sequentially grown on the upper surface 2a of the substrate 2. Then, four barrier layers (not shown) and three quantum well layers (not shown) are alternately grown on the lower guide layer 4c to obtain the active layer 6. Subsequently, an evaporation preventing layer 5a, an upper guide layer 5b, an upper cladding layer 5c, and an upper contact layer 5d are sequentially grown on the active layer 6.

  Next, the p-type semiconductor layer 5 (evaporation preventing layer 5a, upper guide layer 5b, upper cladding layer 5c, upper contact layer 5d) is formed by, for example, low-energy electron beam irradiation (LEEBI) treatment or heat treatment. Adjust the H concentration and lower the resistivity.

  4 and 5 are front views showing the ridge portion forming step. In the ridge portion forming step, as shown in FIG. 4, a resist 21 is formed on the upper contact layer 5d by using, for example, a photolithography technique. The resist 21 is formed in a stripe shape extending in a direction perpendicular to the emission surface 1a (see FIG. 1) (direction perpendicular to the paper surface in FIG. 4).

  Next, as shown in FIG. 5, for example, a reactive etching method is used to etch the resist 21 as a mask to a depth in the middle of the upper cladding layer 5c. Thereby, the ridge portion 10 constituted by the convex portion of the upper cladding layer 5c and the upper contact layer 5d is obtained. By forming the ridge portion 10, a striped optical waveguide 15 (see FIG. 1) is obtained below the ridge portion 10.

6 and 7 are front views showing the buried layer forming step. In the buried layer forming step, as shown in FIG. 6, a buried layer 7 such as SiO _{2 is} formed by sputtering or the like with the resist 21 left on the ridge portion 10. The buried layer 7 is formed to a thickness of about 0.1 μm to about 0.3 μm (for example, about 0.15 μm), for example.

  Next, as shown in FIG. 7, the resist 21 is removed, and the upper surface of the upper contact layer 5d (the upper surface of the ridge portion 10) is exposed. As a result, the ridge portion 10 is buried by the buried layer 7.

  8 and 9 are front sectional views showing the groove forming step. In the groove forming step, as shown in FIG. 8, a resist 22 is formed on the ridge 10 and the buried layer 7 by using, for example, a photolithography technique. The resist 22 has an opening 22 a corresponding to the shape of the groove 12 (see FIG. 1) on the upper surface of the ridge 10. At this time, you may devise, such as processing the side wall of the opening part 22a into a taper shape.

  Next, as shown in FIG. 9, etching is performed to dig the semiconductor laminated film 3 below the opening 22a to form the groove 12, and then the resist 22 is removed. Alternatively, after the dielectric film is formed on the resist 22, the resist 22 may be removed and the dielectric film may be embedded in the groove 12. This prevents the p-side electrode 8 (see FIG. 10) from entering the groove portion 12 in an electrode forming process described later. Accordingly, simultaneous injection of current to the upper cladding layer 5c and the upper contact layer 5d through the sidewall of the groove 12 can be prevented.

  FIG. 10 is a front sectional view showing the electrode forming step. In the electrode formation step, the patterned p-side electrode 8 is formed on the top surfaces of the ridge portion 10 and the buried layer 7 by a combination of photolithography and vapor deposition.

  Next, the n-side electrode 9 is formed on the lower surface 2b of the substrate 2 by, for example, vapor deposition. Before the n-side electrode 9 is formed, the thickness of the substrate 2 may be appropriately adjusted by polishing the lower surface 2b of the substrate 2 or the like. That is, by forming the substrate 2 to a thickness of about 80 μm to about 150 μm (for example, 100 μm), the semiconductor laser element 1 can be easily divided when it is separated into individual pieces.

  In the end face coat film forming step, an end face coat film (not shown) is formed on the exit face 1a and the opposing face 1b (see FIG. 2) facing the exit face 1a. The end face of the semiconductor laser device 1 is protected by the end face coat film and the reflectance of the end face is adjusted.

  In the cutting process, the wafer-like substrate 2 is cut and the semiconductor laser element 1 is separated into pieces, and the chip-shaped semiconductor laser element 1 shown in FIG. 1 is obtained.

  The semiconductor laser device 1 is mounted on, for example, a lead frame or a stem and wire formation is performed, and then sealed in a metal case. As a result, a CAN package type semiconductor laser device is obtained.

  In the semiconductor laser device 1 having the above configuration, when a voltage is applied between the p-side electrode 8 and the n-side electrode 9, a current is injected from the p-side electrode 8 into the active layer 6 through the ridge portion 10. Thus, a stripe-shaped optical waveguide 15 is formed in the active layer 6 along the ridge portion 10, and laser light is emitted from the emission portion 15 a on the end face of the optical waveguide 15. Since the ridge portion 10 is formed in a wide stripe type, multimode laser light is emitted from the emission portion 15a.

  At this time, since the groove portion 12 does not inject current into the active layer 6, it constitutes a modulation portion that reduces the amount of current injection injected into the active layer 6 from the surroundings. The ridge portion 10 is divided in the width direction by the groove portion 12. In the waveguide region partitioned by the groove portion 12 of the ridge portion 10, the high-order mode of the horizontal transverse mode is limited and weakened, and the low-order mode is emphasized.

  As a result, the mode is forcibly selected and the formation of a locally high light intensity region on the emission surface 1a due to the superposition of the higher-order modes is prevented. Therefore, even if there are variations in heat and gain within the ridge portion 10 of the semiconductor laser element 1, COD can be prevented.

  It is more desirable that the groove portion 12 has a length of 5% or more with respect to the length of the ridge portion 10 in the longitudinal direction of the ridge portion 10 because the higher mode can be weakened with certainty. When the groove portion 12 is divided in the longitudinal direction, the total length of the groove portion 12 may be 5% or more with respect to the ridge portion 10.

  The groove portion 12 divides the ridge portion 10 into a plurality of regions in the width direction and is disposed symmetrically with respect to a center line C (see FIG. 2) that bisects the width direction. At this time, the grooves 12 are arranged so that the respective regions are equally spaced. Thereby, the amount of current injected into the active layer 6 in each region divided by the groove 12 can be made uniform.

  The groove portion 12 may be in contact with the emission surface 1a and the opposing surface 1b forming the resonator end face, but it is more desirable that the groove portion 12 be provided at a predetermined distance as in this embodiment. Thereby, the mode control is performed while the laser light guided inside the ridge portion 10 is not completely separated but is weakly coupled. Therefore, it is possible to prevent the same-dimensional mode from existing independently in the ridge portion 10 and to avoid the generation of interference fringes.

  Further, the depth D (see FIG. 9) of the groove 12 is formed to be smaller than the height H (see FIG. 9) of the ridge 10. As a result, it is possible to prevent the same-dimensional mode from existing independently in the ridge portion 10 as described above.

  Depending on the size of the groove 12, the depth D of the groove 12 may be the same or larger than the height H of the ridge 10. In the case where the depth D of the groove 12 and the height H of the ridge 10 are formed to be the same, even if the opening corresponding to the groove 12 is formed in the resist 21 in the ridge formation process shown in FIGS. Good. Thereby, the ridge part 10 and the groove part 12 can be formed simultaneously, and a man-hour can be reduced by omitting a groove part formation process.

  According to the present embodiment, since the groove portion 12 (modulation portion) for reducing the current injection amount of the active layer 6 is provided from the surroundings, the high-order mode of the horizontal transverse mode is limited in the waveguide region partitioned by the groove portion 12. It is weakened and the low-order mode is emphasized. This prevents the formation of a region having a high local light intensity on the emission surface 1a due to the superposition of higher order modes. Therefore, the generation of COD can be prevented and the reliability of the semiconductor laser device 1 can be improved.

  Also, the groove 12 that digs the semiconductor laminated film 3 on the ridge portion 10 (stripe portion) can easily realize a modulation portion that reduces the current injection amount of the active layer 6 from the surroundings.

  Further, since the depth D of the groove portion 12 is smaller than the height H of the ridge portion 10, it is possible to prevent the same-dimensional mode from independently existing in the ridge portion 10, and to avoid generation of interference fringes and the like. it can.

  Further, when a dielectric is embedded in the groove 12, the p-side electrode 8 is prevented from entering the groove 12. Accordingly, simultaneous injection of current to the upper cladding layer 5c and the upper contact layer 5d through the sidewall of the groove 12 can be prevented.

  Further, since the groove portion 12 is formed away from both end faces of the ridge portion 10, it is possible to further prevent the same-dimensional mode from existing independently in the ridge portion 10.

  Further, since the groove portion 12 is arranged symmetrically with respect to the center line C that bisects the width direction of the ridge portion 10, the amount of current injected into the active layer 6 in each region divided by the groove portion 12 can be made uniform. .

  Further, since the plurality of regions divided in the width direction by the groove 12 on the ridge portion 10 are formed at equal intervals, the amount of current injected into the active layer 6 in each region can be made more uniform.

  Further, since the groove portion 12 has a length of 5% or more with respect to the ridge portion 10 in the longitudinal direction of the ridge portion 10, it is possible to surely weaken the higher-order mode of the horizontal transverse mode in the waveguide region.

Second Embodiment
Next, FIGS. 11 and 12 show a front sectional view and a top view of the semiconductor laser device 1 of the second embodiment. For convenience of explanation, the same reference numerals are assigned to the same parts as those in the first embodiment shown in FIGS. In the present embodiment, the groove portion 12 (see FIG. 1) on the ridge portion 10 is omitted from the first embodiment, and the through-hole 8a is provided in the p-side electrode 8. Other parts are the same as those in the first embodiment.

  The through-hole 8 a is formed so as to penetrate the p-side electrode 8 and face the upper surface of the ridge portion 10 by pattern formation of the p-side electrode 8, and extends in the longitudinal direction of the ridge portion 10. Since the through hole 8a does not inject current into the active layer 6, it constitutes a modulation unit that reduces the amount of current injected into the active layer 6 below the surroundings.

  The upper surface of the ridge portion 10 is divided in the width direction by the through hole 8a, and the high-order mode of the horizontal transverse mode is limited and weakened in the waveguide region partitioned by the through-hole 8a of the ridge portion 10, and the low-order mode is reduced. To be emphasized. Therefore, as in the first embodiment, it is possible to prevent the formation of a region having a high local light intensity on the emission surface 1a, thereby preventing COD.

  A plurality of through holes 8 a are provided in the width direction of the ridge portion 10, but one may be provided, or a plurality of through holes 8 a may be provided in the longitudinal direction of the ridge portion 10. Further, it is more preferable that the through hole 8 a has a length of 5% or more with respect to the length of the ridge portion 10 in the longitudinal direction of the ridge portion 10. When the through hole 8 a is divided in the longitudinal direction, the total length of the through holes 8 a may be 5% or more with respect to the ridge portion 10.

  The through hole 8a is arranged symmetrically with respect to the center line C that bisects the width direction of the ridge portion 10. At this time, the through holes 8a are arranged so that the regions divided by the through holes 8a are equally spaced. Further, the through hole 8a may be in contact with the emission surface 1a and the opposing surface 1b forming the resonator end face, but it is more desirable that the through hole 8a is provided at a predetermined distance as in the present embodiment.

  According to the present embodiment, as in the first embodiment, since the through hole 8a (modulation unit) that reduces the current injection amount of the active layer 6 than the surroundings is provided, in the waveguide region partitioned by the through hole 8a. The high-order mode of the horizontal / horizontal mode is limited to emphasize the low-order mode. This prevents the formation of a region having a high local light intensity on the emission surface 1a due to the superposition of higher order modes. Therefore, the generation of COD can be prevented and the reliability of the semiconductor laser device 1 can be improved.

  Further, the through-hole 8a that penetrates the p-side electrode 8 and faces the ridge portion 10 can easily realize a modulation section that reduces the amount of current injection of the active layer 6 from the surroundings.

<Third Embodiment>
Next, FIG. 13 shows a front sectional view of the semiconductor laser device 1 of the third embodiment. For convenience of explanation, the same parts as those in the first and second embodiments shown in FIGS. In the present embodiment, a through-hole 8a of the p-side electrode 8 of the second embodiment is provided for the semiconductor laser element 1 similar to the first embodiment.

  The through hole 8a is formed so as to overlap the groove 12, and the through hole 8a and the groove 12 constitute a modulation unit that reduces the amount of current injected into the active layer 6 from the surroundings. Therefore, the same effects as those of the first and second embodiments can be obtained.

<Fourth embodiment>
Next, FIG. 14 shows a top view of the semiconductor laser device 1 of the fourth embodiment. For convenience of explanation, the same reference numerals are assigned to the same parts as those in the first embodiment shown in FIGS. This embodiment differs in the shape of the groove part 12 with respect to 1st Embodiment. Other parts are the same as those in the first embodiment.

  A plurality of groove portions 12 are provided in parallel in the width direction of the ridge portion 10, and a plurality of groove portions 12 are provided in the longitudinal direction. Moreover, the groove part 12 is formed so that the output surface 1a and the opposing surface 1b may be contact | connected.

  Even in such a configuration, the same effect as in the first embodiment can be obtained. Further, the groove portion 12 is in contact with the emission surface 1a and the opposing surface 1b, but mode control is performed while the laser beam is weakly coupled by being divided in the longitudinal direction. Therefore, it is possible to prevent the same-dimensional mode from existing independently in the ridge portion 10.

  In the first to fourth embodiments, the modulation unit formed by the groove 12 and the through hole 8a does not inject current into the active layer 6, but is a modulation unit that injects weak current by reducing the amount of current injection from the surroundings. There may be.

  The semiconductor laser element 1 is formed in a ridge type having the stripe-shaped ridge portion 10. However, the semiconductor laser element 1 having another structure as long as it has a stripe-shaped stripe portion for injecting current into the active layer 6. It may be. For example, a BH (Buried Heterostructure) type semiconductor laser element or the like may be used.

  In addition, the n-type semiconductor layer 4, the active layer 6, and the p-type semiconductor layer 5 are stacked in this order to form the ridge portion 10 in the p-type semiconductor layer 5. However, the p-type semiconductor layer, the active layer 6, and the n-type semiconductor are formed. The ridge portion 10 may be formed in the n-type semiconductor layer by stacking layers in order.

  Further, the semiconductor laminated film 3 can be applied to other material systems. For example, in the case of a semiconductor laser element that emits laser light in the infrared region, a GaAs-based semiconductor is epitaxially grown on an n-type GaAs substrate in order by metal organic chemical vapor deposition (MOCVD) or molecular beam crystal growth (MBE). .

  At this time, the semiconductor laminated film 3 is formed in order from the substrate side: an n-type GaAs buffer layer, an n-type GaInP buffer layer, an n-type AlGaInP cladding layer, an n-side light guide layer made of AlGaAs, an AlGaAs hole barrier layer, an InGaAs / AlGaAs multiple layer. Consists of a quantum well active layer, a p-side light guide layer made of AlGaAs, a p-type AlGaInP first cladding layer, a p-type GaInP etch stop layer, a p-type AlGaInP second cladding layer, a p-type GaInP intermediate layer, and a p-type GaAs cap layer Is done. The order and composition of each layer can be appropriately changed to the optimum content for the design of each laser.

  Then, the ridge portion 10 can be obtained by processing the p-type AlGaInP second clad layer, the p-type GaInP intermediate layer, and the p-type GaAs cap layer into a stripe shape. The ridge portion 10 and the modulation portion can be formed by etching or the like as described above.

  According to the present invention, it can be used as an excitation light source for illumination or processing.

DESCRIPTION OF SYMBOLS 1,101 Semiconductor laser element 1a Emission surface 2,102 Substrate 3,103 Semiconductor laminated film 4 N-type semiconductor layer 5 P-type semiconductor layer 6 Active layer 7 Buried layer 8, 108 p-side electrode 8a Through-hole 9, 109 N-side electrode 10 Ridge part 12 Groove part 15 Optical waveguide 15a Output part 21, 22 Resist

Claims (5)

  An active layer is disposed between the first conductivity type semiconductor layer and a second conductivity type semiconductor layer having a stripe-shaped stripe portion extending in one direction, and an electrode provided on the stripe portion is interposed through the stripe portion. A semiconductor laser element that emits multimode laser light from an end face of the active layer into which a current is injected, wherein a semiconductor laser element is provided that includes a modulation unit that reduces the amount of current injection of the active layer from the surroundings .   2. The semiconductor laser device according to claim 1, wherein the modulation part is formed by a groove part that digs the semiconductor laminated film on the stripe part.   The semiconductor laser device according to claim 2, wherein a depth of the groove is smaller than a height of the stripe portion.   2. The semiconductor laser device according to claim 1, wherein the modulation portion is formed by a through hole that penetrates the electrode and faces the stripe portion.   5. The semiconductor laser device according to claim 1, wherein the modulation portion is formed away from both end faces of the stripe portion.

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