JP2006351967A - Multi-wavelength semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-wavelength semiconductor laser device capable of matching a reflection factor in a prescribed wavelength band to a prescribed standard. <P>SOLUTION: The multi-wavelength semiconductor laser device comprises a first element section 20A for oscillating a laser beam at a wavelength of 660 nm and a second element section 20B for oscillating a laser beam at a wavelength of 780 nm, on a substrate 10. A rear end face film 30 and a front end face film 31 are collectively formed on the rear and front end faces, respectively, of the first and second element sections 20A, 20B. The front end face film 31 has a layer 32 having a high refractive index in a prescribed thickness, and a layer 33 having a low refractive index in a thickness according to the thickness of the layer 32 having a high refractive index, on the front end face. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multi-wavelength semiconductor laser device having a monolithic structure, and more particularly to an improved multi-wavelength semiconductor laser device having a reflecting film on the high reflectance side.

  In recent years, in the field of semiconductor laser elements (LD), a multi-wavelength laser element having a plurality of light emitting portions having different emission wavelengths on the same substrate (or base) has been actively developed. This multi-wavelength laser element is used as a light source of an optical disc device, for example.

  In such an optical disk apparatus, a laser beam of 780 nm band is used for reproducing a CD (Compact Disk), and CD-R (CD Recordable), CD-RW (CD Rewritable) or MD (Mini Disk) can be recorded. It is used for recording / reproducing of an optical disc. In addition, a 660 nm band laser beam is used for recording / reproduction of a DVD (Digital Versatile Disk). By mounting a multi-wavelength laser element on an optical disk device, recording or reproduction can be performed for any of a plurality of existing types of optical disks. By increasing the number of wavelengths in this way, it is possible to further expand the applications.

In such a monolithic multi-wavelength laser element, generally, as with a single wavelength laser element, a low reflection mirror film and a high reflection mirror film adapted to the wavelength λ of each laser beam are arranged on the end face of the laser element as a whole. The light is efficiently extracted from the end face on the low reflecting mirror film side (Patent Document 1). At this time, the low-reflection mirror film generally has a single layer structure or a multilayer structure in which low refractive index layers having a thickness λo and high refractive index layers having a thickness λo are alternately laminated. The material constituting the structure, the number of stacked layers, and the like are appropriately adjusted according to the target reflectivity. Here, λo is a value obtained by dividing the average value obtained by dividing the sum of the wavelengths of the laser beams emitted from the multiple wavelength laser elements by the number of emitted laser beams by 4n (n is the refractive index).
Japanese Patent Application No. 2001-257413

  However, in the above-described single-layer structure and the multilayer structure in which the low refractive index layer having the thickness λo and the high refractive index layer having the thickness λo are alternately stacked, each of the laser beams emitted from the multiple wavelength laser elements is provided. The reflectance in the wavelength band cannot be controlled independently. For this reason, even if the reflectance according to the standard can be obtained for each wavelength band, there is almost no thickness margin with respect to the standard, and as a result, the thickness of the single layer structure and the multilayer If the thicknesses of the individual films constituting the structure vary due to manufacturing errors or the like, the reflectance in the wavelength band of any laser beam is out of the standard, and the yield may be reduced. In particular, in the case of a two-wavelength laser element in the 660 nm band and the 780 nm band, in consideration of manufacturing errors, the standards (first standard) that reflectivities in the 660 nm band and the 780 nm band are both 6% or more and 8% or less, The reflectance of 6% to 8%, the reflectance of 780 nm band is 20% or more (second standard), the reflectance of 660 nm band is 6% or more, and the reflectance of 780 nm band is 6% or more. There is a problem that there is no layer structure that satisfies the standard (third standard) of 8% or less.

  The present invention has been made in view of such problems, and an object thereof is to provide a multi-wavelength semiconductor laser device capable of adapting the reflectance in a predetermined wavelength band to a predetermined standard.

  The multi-wavelength semiconductor laser device of the present invention has, on a substrate, a first element portion that oscillates laser light of a first wavelength and a second element portion that oscillates laser light of a second wavelength. A front end face film is formed on the front end face of each of the first element part and the second element part, and a rear end face film is formed on the rear end face. The front end face film has a high refractive index layer having a predetermined thickness and a low refractive index layer having a thickness corresponding to the thickness of the high refractive index layer on the front end face.

  In the multiwavelength semiconductor laser device of the present invention, when current is injected into the first element portion and the second element portion, light emission occurs in the respective light emitting regions. The light emitted in each region is reflected by the front end face film and the rear end face film and laser oscillates, and the laser light having the first wavelength from the first element part side of the front end face film is the second element part side of the front end face film. To 2nd wavelength laser beams are respectively emitted to the outside.

  At this time, the thickness of the high refractive index layer is a value obtained by dividing the first wavelength or the second wavelength by 4n (n is the refractive index) or an average value obtained by dividing the sum of the first wavelength and the second wavelength by 2. Unlike the value divided by 4n (hereinafter referred to as “value derived from the function of the wavelength of laser light”), it is a thickness that can satisfy the first standard, the second standard, and the third standard.

For example, when the high refractive index layer is an Al ₂ O ₃ layer and the low refractive index layer is an SiO ₂ layer, the Al ₂ O ₃ layer has a thickness of 30 nm or more and 60 nm or less in the first standard, and the second In the case of the standard, the Al ₂ O ₃ layer has a thickness of 210 nm to 230 nm. The SiO ₂ layer is set to a thickness that can satisfy the above-mentioned standard in the set thickness of the Al ₂ O ₃ layer.

  In this way, the front end face film is composed of the high refractive index layer and the low refractive index layer, and the thickness of the high refractive index layer is set to a value that is not a function of the wavelength of the laser light. It is possible to relatively freely control the reflectance in the wavelength band including, and the thickness margin for the reflectance in these wavelength bands becomes large.

  According to the semiconductor laser device of the present invention, the front end face film composed of the high refractive index layer and the low refractive index layer is provided, and the thickness of the high refractive index layer is a value other than a value derived from a function of the wavelength of the laser light. Since the value is set, the thickness margin with respect to the reflectance in the wavelength band including the first wavelength and the second wavelength is increased. As a result, even if the thickness of individual films constituting the multilayer structure varies due to manufacturing errors, the reflectance in the wavelength band of any laser beam is not likely to deviate from the standard, and the yield may be reduced. Absent. As a result, the reflectance in a wavelength band including the first wavelength and the second wavelength (for example, 660 nm band and 780 nm band) can be adapted to a predetermined standard.

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

[First Embodiment]
FIG. 1 shows a cross-sectional configuration of a two-wavelength semiconductor laser device according to the first embodiment of the present invention. FIG. 2 shows a planar configuration of the two-wavelength semiconductor laser element of FIG. FIG. 1 shows a cross-sectional configuration in the direction of arrows AA in FIG. 1 and 2 are schematically shown and are different from actual dimensions and shapes.

  This two-wavelength semiconductor laser element is a monolithic laser element in which a first element part 20A and a second element part 20B are arranged on a substrate 10.

(First element portion 20A)
The first element portion 20A is a semiconductor laser element capable of emitting light in the 660 nm band, and is composed of an aluminum / gallium / indium / phosphorus (AlGaInP) group III-V group compound semiconductor. The aluminum, gallium, indium, and phosphorus group III-V compound semiconductor here means at least aluminum (Al), gallium (Ga), and indium (In) among the 3B group elements in the short period type periodic table, and short. It refers to those containing at least phosphorus (P) among the group 5B elements in the periodic periodic table.

  The first element portion 20A is obtained by growing a semiconductor layer 21A on the substrate 10. The semiconductor layer 21A includes an n-type cladding layer, an active layer 22A, a p-type cladding layer, and a p-side contact layer. Note that layers other than the active layer 22A are not particularly shown.

  Specifically, the substrate 10 is made of, for example, n-type GaP and has a thickness of about 100 μm, for example.

The n-type cladding layer is made of, for example, n-type AlGaInP having a thickness of 1.5 μm. The active layer 22A is, for example, a multiple quantum of a well layer and a barrier layer each formed of Al _x Ga _y In _1-xy P having a thickness of 40 nm and different compositions (where x ≧ 0 and y ≧ 0). It has a well structure. The p-type cladding layer is made of, for example, p-type AlGaInP having a thickness of 1.5 μm. The p-side contact layer is made of, for example, p-type GaP having a thickness of 0.5 μm. A part of the p-type cladding layer and the p-side contact layer have a striped ridge portion 23A extending in the direction of the resonator, so that current confinement is achieved. A region corresponding to the ridge portion 23A in the active layer 22A is a first light emitting point 24A.

An insulating layer 25 is provided on a continuous surface (hereinafter referred to as surface A) from the side surface of the ridge portion 23A to the surface of the p-type cladding layer. The insulating layer 25 is made of an insulating material such as SiO ₂ , ZrOx, or SiN of about 300 nm, for example, and electrically connects the semiconductor layer 21A of the first element unit 20A and the semiconductor layer 21B (described later) of the second element unit 20B. In addition, current can flow into the active layer 22A only from the upper surfaces of the ridge portion 23A and the ridge portion 23B (described later). Therefore, the insulating layer 25 has an element isolation function and a current confinement function.

  A p-side electrode 26A is provided on a continuous surface from the upper surface (surface of the p-side contact layer) of the ridge portion 23A to the surface of the insulating layer 25, and is electrically connected to the p-side contact layer. On the other hand, an n-side electrode 27 is provided on the back surface of the substrate 10 and is electrically connected to the substrate 10.

  A wiring layer 28A is provided on the p-side electrode 26A and is electrically connected to the p-side electrode 26A. The p-side electrode 26A is connected to a positive-side power supply (not shown) through a wiring (not shown) electrically connected to the wiring layer 28A. The n-side electrode 27 is electrically connected to a wiring (not shown), and is connected to a negative power source (not shown) via the wiring. Here, the p-side electrode 26A and the n-side electrode 27A have a multilayer structure in which, for example, Ti having a thickness of 15 nm / Pt having a thickness of 50 nm / Au having a thickness of 300 nm are stacked in this order. The wiring layer 28A is made of, for example, Au having a thickness of 8.7 μm.

(Second element portion 20B)
The second element portion 20B is a semiconductor laser element capable of emitting light of 780 nm, and is composed of a gallium arsenic (GaAs) group III-V compound semiconductor. The gallium-arsenic III-V group compound semiconductor here is at least gallium (Ga) of 3B group elements in the short period type periodic table, and at least arsenic of 5B group elements in the short period type periodic table. As).

  The second element portion 20B is obtained by growing a semiconductor layer 21B on the substrate 10 like the first light emitting element 20A. The semiconductor layer 21B includes an n-type cladding layer, an active layer 22B, a p-type cladding layer, and a p-side contact layer. The layers other than the active layer 22B are not particularly shown.

Specifically, the n-type cladding layer is made of, for example, n-type AlGaAs having a thickness of 1.5 μm. The active layer 22B has, for example, a multiple quantum well structure of a well layer and a barrier layer each formed of Al _x Ga _1-x As (where x ≧ 0) having a thickness of 35 nm and having different compositions. The p-type cladding layer is made of, for example, p-type AlGaAs having a thickness of 1.0 μm. The p-side contact layer is made of, for example, p-type GaAs having a thickness of 0.5 μm. A part of the p-type cladding layer and the p-side contact layer have a striped ridge portion 23B extending in the direction of the resonator, so that current confinement is achieved. In the active layer 22B, a region corresponding to the ridge portion 23B is a second light emitting point 24B.

  The insulating layer 25 described above is provided on a continuous surface (hereinafter referred to as surface B) from the side surface of the ridge portion 23B to the surface of the p-type cladding layer.

  A p-side electrode 26B is provided on a continuous surface from the upper surface of the ridge portion 23B (the surface of the p-side contact layer) to the surface of the insulating layer 25, and is electrically connected to the p-side contact layer. On the other hand, the n-side electrode 27 described above is provided on the back surface of the substrate 10 and is electrically connected to the substrate 10.

  A wiring layer 28B is provided on the p-side electrode 26B and is electrically connected to the p-side electrode 26B. The p-side electrode 26B is connected to a positive power source (not shown) via a wiring (not shown) electrically connected to the wiring layer 28B. Here, the p-side electrode 26B is formed by stacking, for example, Ti having a thickness of 15 nm / Pt having a thickness of 50 nm / Au having a thickness of 300 nm in this order. The wiring layer 28B is made of, for example, Au having a thickness of 4.5 μm.

(Front end face film, rear end face film)
Further, as shown in FIG. 2, the surface perpendicular to the extending direction (axial direction) of the ridge portion 23A of the first element portion 20A (the extending direction (axial direction of the ridge portion 23B of the second element portion 20B)). A pair of reflecting mirror films are formed in a lump on the surface perpendicular to). The reflection-side film (rear end face film 30) of the pair of reflecting mirror films is formed by laminating one or a plurality of Al ₂ O ₃ layers having a thickness λo and TiO ₂ layers having a thickness λo on the rear end face. The multilayer structure is adjusted so that the reflectance is high. Here, λo is an intermediate wavelength 720 nm obtained by adding the wavelength 660 nm of the laser beam emitted from the first element unit 20A and the wavelength 780 nm of the laser beam emitted from the second element unit 20B and dividing by two.

  On the other hand, the main emission side film (front end face film 31) has a high refractive index layer 32 having a predetermined thickness on the front end face and a low refractive index layer having a thickness corresponding to the thickness of the high refractive index layer 32. 33 are laminated in this order, and are adjusted to satisfy the first standard.

Specifically, the high refractive index layer 32 is composed of an Al ₂ O ₃ layer, and the low refractive index layer 33 is composed of an SiO ₂ layer. The thickness of the Al ₂ O ₃ layer is a value obtained by dividing 660 nm or 780 nm by 4n (n is the refractive index), or an average value obtained by dividing the sum of 660 nm and 780 nm by 2 (the wavelength of the laser beam). Unlike the value derived from the function (1), it is 30 nm or more and 60 nm or less. For example, when the thickness of the Al ₂ O ₃ layer is 30 nm, the thickness of the SiO ₂ layer is 85 nm or more and 120 nm or less, and when the thickness of the Al ₂ O ₃ layer is 50 nm, the thickness of the SiO ₂ layer is 50 nm or more and 70 nm or less, When the thickness of the Al ₂ O ₃ layer is 60 nm, the thickness of the SiO ₂ layer is 40 nm or more and 80 nm or less.

  The two-wavelength semiconductor laser device having such a configuration can be manufactured, for example, as follows.

First, the laser structure of the first element unit 20A is manufactured. For this purpose, the semiconductor layer 21A on the substrate 10 is formed by, for example, the MOCVD method. At this time, for example, trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMIn), and phosphine (PH ₃ ) are used as the raw material for the AlGaInP-based semiconductor. (H ₂ Se) is used, and dimethyl zinc (DMZn), for example, is used as the acceptor impurity raw material.

  Specifically, first, an n-side contact layer, an n-type cladding layer, an active layer 22A, a p-type cladding layer, and a p-type contact layer are stacked in this order on the substrate 10 to form the semiconductor layer 21A. Subsequently, the p-side contact layer and the p-type cladding layer are patterned, for example, by a dry etching method so as to form a thin band-like convex portion, thereby forming a ridge portion 23A.

Next, the laser structure of the second element unit 20B is manufactured. For this purpose, the semiconductor layer 21B on the substrate 10 is formed by, for example, the MOCVD method. At this time, for example, TMA, TMG, TMIn, and arsine (AsH ₃ ) are used as the raw material for the GaAs-based semiconductor, H ₂ Se is used as the raw material for the donor impurity, and DMZn is used as the raw material for the acceptor impurity, for example. Is used.

  Specifically, first, an n-side contact layer, an n-type cladding layer, an active layer 22B, a p-type cladding layer, and a p-type contact layer are stacked in this order on the substrate 10 to form the semiconductor layer 21B. Subsequently, the p-side contact layer and the p-type cladding layer are patterned, for example, by a dry etching method so as to form a thin band-like convex portion, thereby forming a ridge portion 23B. Thereby, as shown in FIG. 3A, the laser structure of the first element unit 20A and the laser structure of the second element unit 20B are arranged on the substrate 10.

  Next, after an insulating material such as SiN is formed on the upper surfaces of the ridge portions 23A and 23B and on the surfaces A and B by vapor deposition or sputtering, as shown in FIG. , 23B, the region corresponding to the upper surface is removed by etching. Thereby, the insulating layer 25 is formed on the surfaces A and B.

  Next, as shown in FIG. 1, the p-side electrode 26A and the wiring layer 28A are stacked in this order on the continuous surface from the surface of the p-side contact layer of the ridge portion 23A to the surface of the insulating layer 25. . Further, the p-side electrode 26B and the wiring layer 28B are laminated in this order on the continuous surface from the surface of the p-side contact layer of the ridge portion 23B to the surface of the insulating layer 25. In addition, an n-side electrode 27 is formed on the back surface of the substrate 10.

  Next, after cleaving on a plane perpendicular to the extending direction of the ridge portions 23A and 23B, the front end face film 31 and the rear end face film 32 are collectively formed on the cleaved face. In this way, the two-wavelength semiconductor laser device of the present embodiment is manufactured.

  Next, the operation and effect of the two-wavelength semiconductor laser device of this embodiment will be described.

  In the two-wavelength semiconductor laser device of the present embodiment, when a predetermined voltage is applied between the p-side electrodes 26A and 26B and the n-side electrode 27, current is injected into the active layers 22A and 22B, and the electron-positive Luminescence occurs due to hole recombination. The light emitted from each of the active layers 22A and 22B is reflected by the front end face film 30 and the rear end face film 31 and laser oscillates. Laser light having a wavelength of 660 nm from the first element portion 20A side of the front end face film 30 is emitted from the front end face film. 30, laser light having a wavelength of 780 nm is emitted to the outside from the second element unit 20B side. Thus, the first element unit 20A and the second element unit 20B can emit laser beams having different wavelengths.

  By the way, the front end face film 31 has a single structure formed on the rear end face as described above, and the material, thickness, layer structure, etc. are adjusted according to the part where the laser light is emitted. It does not have a plurality of configurations. Therefore, it is necessary to realize a reflectance (here, the first standard) that satisfies a predetermined standard with respect to laser light having both wavelengths in a single configuration.

  In general, the front end face film of a single configuration has a single-layer structure, or an intermediate wavelength (λ1 + λ2) / 2 obtained by adding the wavelength λ1 of one laser beam and the wavelength λ2 of the other laser beam and dividing it by 2 as λo. Then, a high refractive index layer having a thickness λo and a low refractive index layer having a thickness λo are taken as one set, and one or a plurality of these layers are stacked. In the front end face film having such a structure, the reflectance in the respective wavelength bands of the laser light emitted from the two-wavelength laser element cannot be controlled independently. For this reason, even if the reflectance according to the standard can be obtained for each wavelength band, there is almost no thickness margin with respect to the standard, and as a result, the thickness of the single layer structure and the multilayer If the thicknesses of the individual layers constituting the structure vary due to manufacturing errors or the like, the reflectance in the wavelength band of any laser beam is out of the standard, and the yield may be reduced. In particular, in a two-wavelength laser element in the 660 nm band and the 780 nm band, it is extremely difficult to form a layer structure that satisfies a predetermined standard in consideration of manufacturing errors and the like.

For example, as illustrated in FIG. 4, in the front end face film having a single layer structure made of Al ₂ O ₃ , the thickness that satisfies the above-mentioned standard is only 330 nm, and the reflectance at this time is 8%, which is the upper limit of the standard It has become. For this reason, if the thicknesses of the individual layers constituting the front end face film vary due to manufacturing errors or the like, the reflectance in the wavelength band of at least one laser beam is out of the standard, and the yield may be reduced. Therefore, it can be confirmed that it is extremely difficult to adapt the reflectance in the 660 nm band and the 780 nm band to a predetermined standard.

  On the other hand, in the two-wavelength semiconductor laser device of the present embodiment, the front end face film 31 having a single configuration is configured by laminating a high refractive index layer 32 and a low refractive index layer 33 in this order on the front end face. Since the thickness of the high refractive index layer is configured to be a value that is not a function of the wavelength of the laser beam, the reflectance in the 660 nm band and the 780 nm band can be controlled relatively freely. The thickness margin for the reflectance in the wavelength band can be increased.

For example, as illustrated in FIG. 5, when the high refractive index layer 32 is an Al ₂ O ₃ layer having a thickness of 50 nm, the low refractive index layer 33 is an SiO ₂ layer having a thickness of 50 nm to 70 nm. Meet the standards. In addition, although not shown in the drawings, when the high refractive index layer 32 is an Al ₂ O ₃ layer having a thickness of 45 nm, the above-mentioned standard is acceptable as long as the low refractive index layer 33 is an SiO ₂ layer having a thickness of 60 nm to 90 nm. When the high refractive index layer 32 is an Al ₂ O ₃ layer having a thickness of 60 nm, the low refractive index layer 33 may be an SiO ₂ layer having a thickness of 40 nm to 80 nm. Thus, when the high refractive index layer 32 is an Al ₂ O ₃ layer having a thickness of 45 nm or more and 60 nm or less, the above-mentioned standard can be satisfied, and the thickness of the thickness with respect to the reflectance in the 660 nm band and the 780 nm band can be satisfied. It can be confirmed that the margin is large. Moreover, it can also be confirmed that the thickness of the front end face film 31 in FIG. 5 is very thin compared to the front end face film in FIG.

  Thus, according to the two-wavelength semiconductor laser device of the present embodiment, the front end face film 31 formed by laminating the high refractive index layer 32 and the low refractive index layer 33 in this order is provided, and the thickness of the high refractive index layer 32 is As a result, the thickness margin for the reflectivity in the 660 nm band and the 780 nm band is increased, thereby increasing the thickness of the individual layers constituting the multilayer structure. Even if there are variations due to manufacturing errors, there is no possibility that the reflectance in the wavelength band of any of the laser beams will deviate from the standard, and there is no possibility that the yield will decrease. As a result, the reflectance in the 660 nm band and the 780 nm band can be adapted to a predetermined standard.

  In addition, since the front end face film 31 has a multilayer structure, the thickness can be reduced as compared with the case of the single layer structure.

[Second Embodiment]
Next, a two-wavelength semiconductor laser device according to the second embodiment of the present invention will be described. FIG. 6 shows a planar configuration of the two-wavelength semiconductor laser element of the present embodiment. FIG. 6 is a schematic representation, which differs from actual dimensions and shapes.

  This two-wavelength semiconductor laser device is different from the first embodiment in that a front end face film 41 is provided. Therefore, the description of the same configuration, operation, and effect as in the first embodiment is omitted as appropriate, and the front end face film 41 will be mainly described below.

  The front end face film 41 is configured by laminating a high refractive index layer 42 having a predetermined thickness and a low refractive index layer 43 having a thickness corresponding to the thickness of the high refractive index layer 42 on the front end face in this order. It has a multilayer structure and is adjusted to meet the second standard.

Specifically, in the same manner as the front end face film 31 of the first embodiment, the front end face film 41 includes a high refractive index layer 42 formed of an Al ₂ O ₃ layer and a low refractive index layer 43 formed of a SiO ₂ layer. Yes. Each of the Al ₂ O ₃ layer and the SiO ₂ layer has a thickness different from a value derived from a function of the wavelength of the laser beam. For example, the thickness of the Al ₂ O ₃ layer is 210 nm to 230 nm, and the thickness of the SiO ₂ layer is 70 nm to 110 nm.

FIG. 7 shows a specific example of the reflectance distribution of the front end face film 41. As illustrated in FIG. 7, when the high refractive index layer 42 is an Al ₂ O ₃ layer having a thickness of 220 nm, the above-described standard is satisfied if the low refractive index layer 43 is an SiO ₂ layer having a thickness of 80 nm to 110 nm. Fulfill. In addition, although not shown in the drawings, when the high refractive index layer 42 is an Al ₂ O ₃ layer having a thickness of 210 nm, the above-mentioned standard is acceptable as long as the low refractive index layer 43 is an SiO ₂ layer having a thickness of 75 nm to 105 nm. When the high refractive index layer 42 is an Al ₂ O ₃ layer having a thickness of 230 nm, the low refractive index layer 43 may be an SiO ₂ layer having a thickness of 70 nm or more and 100 nm or less. Thus, when the high refractive index layer 42 is an Al ₂ O ₃ layer having a thickness of 210 nm or more and 230 nm or less, the above-mentioned standard can be satisfied, and the thickness with respect to the reflectance in the 660 nm band and the 780 nm band can be satisfied. It can be confirmed that the margin is large.

  In the front end face film 41 of FIG. 7, when the thickness of the front end face film 41 is set between 305 nm and 325 nm, the reflectance of the 660 nm band is within the standard range (within the range of 6% to 8%). Therefore, when the thickness of the low refractive index layer 43 is changed between 85 nm and 105 nm, the reflectance of the 780 nm band is changed without changing the reflectance of the 660 nm band. Can be set within the range (20% or more). Therefore, the reflectance of the 660 nm band and the 780 nm band can be independently controlled by changing the thickness of the high refractive index layer 42 to a predetermined thickness and changing the thickness of the low refractive index layer 43. I can confirm that I can do it.

  As described above, according to the two-wavelength semiconductor laser element of the present embodiment, the front end face film 41 formed by laminating the high refractive index layer 42 and the low refractive index layer 43 in this order is provided, and the thickness of the high refractive index layer 42 is increased. Since the thickness is set to a value that is not a function of the wavelength of the laser beam, the margin of the thickness with respect to the reflectivity in the 660 nm band and the 780 nm band is increased, whereby the thickness of each layer constituting the multilayer structure is increased. However, even if there is a variation due to a manufacturing error or the like, there is no possibility that the reflectance in the wavelength band of any laser beam will be out of the standard, and there is no possibility that the yield will be lowered. As a result, the reflectance in the 660 nm band and the 780 nm band can be adapted to a predetermined standard.

  Further, the reflectance of the 660 nm band and the 780 nm band can be independently controlled by changing the thickness of the high refractive index layer 42 to a predetermined thickness and changing the thickness of the low refractive index layer 43.

[Third Embodiment]
Next, a two-wavelength semiconductor laser element according to the third embodiment of the present invention will be described. FIG. 8 shows a planar configuration of the two-wavelength semiconductor laser element of the present embodiment. FIG. 8 is a schematic representation, which differs from actual dimensions and shapes.

  This two-wavelength semiconductor laser device is different from the first embodiment in that a front end face film 51 is provided. Therefore, the description of the same configuration, operation, and effect as in the first embodiment is omitted as appropriate, and the front end face film 51 will be mainly described below.

  The front end face film 51 includes a high refractive index layer 52 having a predetermined thickness and a low refractive index layer 53 having a thickness corresponding to the thickness of the high refractive index layer 52 on the front end face. Has a multilayer structure provided in the low refractive index layer 53 and is adjusted to satisfy the first standard.

Specifically, unlike the front end face film 31 of the first embodiment, the front end face film 51 is composed of a high refractive index layer 52 of a TiO ₂ layer and a low refractive index layer 53 of an Al ₂ O ₃ layer. ing. Each of the TiO ₂ layer and the Al ₂ O ₃ layer has a thickness different from a value derived from a function of the wavelength of the laser beam. For example, the thickness of the TiO ₂ layer is 10 nm or more and 15 nm or less, and the thickness of the Al ₂ O ₃ layer is 15 nm or more and 100 nm or less.

FIG. 9 shows a specific example of the reflectance distribution of the front end face film 51. As illustrated in FIG. 9, when the high refractive index layer 52 is a TiO ₂ layer having a thickness of 12.5 nm, the low refractive index layer 53 is an Al ₂ O ₃ layer having a thickness of 15 nm to 100 nm. Meet the standards. In addition, although not shown in the drawings, when the high refractive index layer 52 is a TiO ₂ layer having a thickness of 10 nm, the above-described standard is acceptable as long as the low refractive index layer 53 is an Al ₂ O ₃ layer having a thickness of 15 nm to 100 nm. When the high refractive index layer 52 is a TiO ₂ layer having a thickness of 15 nm, the low refractive index layer 53 may be an Al ₂ O ₃ layer having a thickness of 15 nm or more and 100 nm or less. Thus, when the high refractive index layer 52 is a TiO ₂ layer having a thickness of 10 nm or more and 15 nm or less, the above-mentioned standard can be satisfied, and the thickness margin with respect to the reflectivity in the 660 nm band and the 780 nm band is provided. It can be confirmed that it is large.

  Thus, according to the two-wavelength semiconductor laser device of the present embodiment, the front end face film 51 including the high refractive index layer 52 and the low refractive index layer 53 is provided, and the thickness of the high refractive index layer 52 is Is set to a value that is not a function of the wavelength of the laser beam, so that the margin of thickness for the reflectivity in the 660 nm band and the 780 nm band becomes large, and thereby the thickness of the individual layers constituting the multilayer structure can be reduced. Even if there is a variation due to a manufacturing error or the like, there is no possibility that the reflectance in the wavelength band of any laser beam will be out of the standard, and there is no possibility that the yield will be lowered. As a result, the reflectance in the 660 nm band and the 780 nm band can be adapted to a predetermined standard.

[Fourth Embodiment]
Next, a two-wavelength semiconductor laser element according to the fourth embodiment of the present invention will be described. FIG. 10 shows a planar configuration of the two-wavelength semiconductor laser element of the present embodiment. FIG. 10 is a schematic representation, which differs from actual dimensions and shapes.

  This two-wavelength semiconductor laser device is different from the configuration of the third embodiment in that a front end face film 61 is provided. Therefore, the description of the configuration, action, and effect similar to those of the third embodiment is omitted as appropriate, and the front end face film 61 will be mainly described below.

  The front end face film 61 includes a high refractive index layer 62 having a predetermined thickness and a low refractive index layer 63 having a thickness corresponding to the thickness of the high refractive index layer 62 on the front end face. Has a multilayer structure provided in the low refractive index layer 63 and is adjusted to satisfy the third standard.

Specifically, in the front end face film 61, as in the third embodiment, the high refractive index layer 62 is composed of a TiO ₂ layer, and the low refractive index layer 63 is composed of an Al ₂ O ₃ layer. Each of the TiO ₂ layer and the Al ₂ O ₃ layer has a thickness different from a value derived from a function of the wavelength of the laser beam. For example, the thickness of the TiO ₂ layer is 55 nm to 65 nm, and the thickness of the Al ₂ O ₃ layer is 15 nm to 100 nm.

FIG. 11 shows a specific example of the reflectance distribution of the front end face film 61. As illustrated in FIG. 11, when the high refractive index layer 62 is a TiO ₂ layer having a thickness of 60 nm, the low refractive index layer 63 is an Al ₂ O ₃ layer having a thickness of 15 nm or more and 100 nm or less. Fulfill. In addition, although not shown, when the high refractive index layer 62 is a TiO ₂ layer having a thickness of 55 nm, the above-mentioned standard is acceptable as long as the low refractive index layer 63 is an Al ₂ O ₃ layer having a thickness of 15 nm to 100 nm. When the high refractive index layer 62 is a TiO ₂ layer having a thickness of 65 nm, the low refractive index layer 63 may be an Al ₂ O ₃ layer having a thickness of 15 nm or more and 100 nm or less. As described above, when the high refractive index layer 62 is a TiO ₂ layer having a thickness of 55 nm or more and 65 nm or less, the above-mentioned standard can be satisfied, and a thickness margin with respect to the reflectance in the 660 nm band and the 780 nm band is provided. It can be confirmed that it is large.

  Further, in the front end face film 61 of FIG. 11, when the thickness of the front end face film 61 is set at least between 150 nm and 200 nm, the reflectance of the 780 nm band is within the standard range (in the range of 6% to 8%). Therefore, if the thickness of the low refractive index layer 63 is changed between at least 90 nm and 140 nm, the reflectance in the 660 nm band is changed without changing the reflectance in the 780 nm band. Can be set within the standard range (6% or more). Thus, the reflectance of the 660 nm band and the 780 nm band can be independently controlled by changing the thickness of the high refractive index layer 62 to a predetermined thickness and changing the thickness of the low refractive index layer 63. I can confirm that I can do it.

  Thus, according to the two-wavelength semiconductor laser device of the present embodiment, the front end face film 61 configured to include the high refractive index layer 62 and the low refractive index layer 63 is provided, and the thickness of the high refractive index layer 62 is increased. Is set to a value that is not a function of the wavelength of the laser beam, so that the margin of thickness for the reflectivity in the 660 nm band and the 780 nm band becomes large, and thereby the thickness of the individual layers constituting the multilayer structure can be reduced. Even if there is a variation due to a manufacturing error or the like, there is no possibility that the reflectance in the wavelength band of any laser beam will be out of the standard, and there is no possibility that the yield will be lowered. As a result, the reflectance in the 660 nm band and the 780 nm band can be adapted to a predetermined standard.

  Further, the reflectance of the 660 nm band and the 780 nm band can be independently controlled by changing the thickness of the high refractive index layer 62 to a predetermined thickness and changing the thickness of the low refractive index layer 63.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment and can be variously modified.

  For example, in the above-described embodiment, an example in which the present invention is applied to a two-wavelength semiconductor laser element has been described. However, the present invention is not limited to this, and can be applied to a multi-wavelength semiconductor laser element. At this time, the front end face film from which laser light in a wavelength band other than the 660 nm band and the 780 nm band is emitted may be formed together with the front end face films 31, 41, 51, 61 described above, or may be formed separately. It may be. Further, the present invention can also be applied to a semiconductor laser element of a type in which a plurality of laser beams of at least one of 660 nm band and 780 nm band are emitted.

  Moreover, in the said embodiment, an AlGaInP type III-V compound semiconductor laser element is mentioned as the 1st element part 20A, and a GaAs type III-V group compound semiconductor laser element is mentioned as the 2nd element part 20B, respectively, Although the configuration has been specifically exemplified and described, the present invention can be similarly applied to semiconductor laser elements having other compositions and structures.

1 is a cross-sectional configuration diagram of a two-wavelength semiconductor laser device according to a first embodiment of the present invention. FIG. 2 is a plan configuration diagram of the two-wavelength semiconductor laser element of FIG. 1. FIG. 7 is a cross-sectional view for explaining a part of the manufacturing process of the two-wavelength semiconductor laser element of FIG. 1. It is a figure showing an example of the reflectance distribution of the conventional front end face film. It is a figure showing an example of the reflectance distribution of the front end surface film | membrane of FIG. It is a plane block diagram of the 2 wavelength semiconductor laser element which concerns on the 2nd Embodiment of this invention. It is a figure showing an example of the reflectance distribution of the front end surface film | membrane of FIG. It is a plane block diagram of the 2 wavelength semiconductor laser element which concerns on the 3rd Embodiment of this invention. It is a figure showing an example of the reflectance distribution of the front end surface film | membrane of FIG. It is a plane block diagram of the 2 wavelength semiconductor laser element which concerns on the 4th Embodiment of this invention. FIG. 11 is a diagram illustrating a specific example of the reflectance distribution of the front end face film in FIG. 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 20A ... 1st element part, 20B ... 2nd element part, 21A, 21B ... Semiconductor layer, 22A, 22B ... Active layer, 23A, 23B ... Ridge part, 24A ... 1st light emission point, 24B ... 1st 2 light emitting points, 25 ... insulating layer, 26A, 26B ... p-side electrode, 27 ... n-side electrode, 28A, 28B ... wiring layer, 30 ... rear end face film, 31, 41, 51, 61 ... front end face film, 32, 42 , 52, 62 ... high refractive index layer, 33, 43, 53, 63 ... low refractive index layer.

Claims (7)

A first element portion that oscillates a laser beam of a first wavelength formed on the substrate, a second element portion that oscillates a laser beam of a second wavelength formed on the substrate, and the first element portion. A front end face film formed on the front end face of each of the element part and the second element part; and a rear end face film formed on the rear end face of each of the first element part and the second element part.
The front end face film includes a high refractive index layer having a predetermined thickness on the front end face and a low refractive index layer having a thickness corresponding to the thickness of the high refractive index layer. Wavelength semiconductor laser element. The high refractive index layer is an Al ₂ O ₃ layer having a thickness of 30 nm to 60 nm,
The multi-wavelength semiconductor laser device according to claim 1, wherein the low refractive index layer is a SiO ₂ layer having a thickness of 40 nm or more and 120 nm or less. The thickness of the SiO ₂ layer is 85 nm to 120 nm when the thickness of the Al ₂ O ₃ layer is 30 nm, 50 nm to 70 nm when the thickness of the Al ₂ O ₃ layer is 50 nm, and the Al ₂ The multiwavelength semiconductor laser device according to claim 2, wherein the thickness of the O ₃ layer is 40 nm or more and 80 nm or less when the thickness of the O ₃ layer is 60 nm. The high refractive index layer is a TiO ₂ layer having a thickness of 10 nm to 15 nm,
The multi-wavelength semiconductor laser device according to claim 1, wherein the low refractive index layer is an Al ₂ O ₃ layer having a thickness of 15 nm to 100 nm. The high refractive index layer is an Al ₂ O ₃ layer having a thickness of 210 nm to 230 nm,
The multi-wavelength semiconductor laser device according to claim 1, wherein the low refractive index layer is a SiO ₂ layer having a thickness of 70 nm to 110 nm. The thickness of the SiO ₂ layer is 80 nm to 110 nm when the thickness of the Al ₂ O ₃ layer is 210 nm, 75 nm to 105 nm when the thickness of the Al ₂ O ₃ layer is 220 nm, and the Al ₂ The multiwavelength semiconductor laser device according to claim 5, wherein the thickness of the O ₃ layer is 70 nm or more and 100 nm or less when the thickness of the O ₃ layer is 230 nm. The high refractive index layer is a TiO ₂ layer having a thickness of 55 nm or more and 65 nm or less,
The multi-wavelength semiconductor laser device according to claim 1, wherein the low refractive index layer is an Al ₂ O ₃ layer having a thickness of 15 nm to 100 nm.

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