Nitride semiconductor laser element

Abstract

To provide a nitride semiconductor laser element in which generation of an end surface damage is suppressed.SOLUTION: A nitride semiconductor laser element comprises: a first conductive type first nitride semiconductor layer; a second conductive type second nitride semiconductor layer that is a conductive type different from the first conductive type; an active layer that is arranged between the first nitride semiconductor layer and the second nitride semiconductor layer; a light emission side end surface and a light reflection side end surface which are crossed to a surface on the side of the second nitride semiconductor layer of the active layer; and a protection film that is provided to the light emission side end surface. The protection film comprises: a crystalline first film containing an aluminum and / or gallium, and oxygen in order from the side of the light emission side end surface; a crystalline second film made of a nitride film; and a third film containing the aluminum and oxygen.SELECTED DRAWING: Figure 1C

Description

[Technical Field]

[0001] This invention relates to a nitride semiconductor laser element. [Background technology]

[0002] In recent years, various light-emitting devices have been proposed that utilize semiconductor lasers or other sources as excitation light sources, and use the excitation light emitted from these sources for illumination and other purposes. In such light-emitting devices, a nitride-based semiconductor laser element has been proposed that prevents the peeling of the protective film formed on the resonator surface (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-99959 [Overview of the project] [Problems that the invention aims to solve]

[0004] On the other hand, in semiconductor lasers, where particularly high power output is required, catastrophic optical damage (COD) is cited as one of the limiting factors in increasing power output. There is a need for semiconductor laser elements that overcome this limitation, that is, that suppress the occurrence of COD, resulting in higher power output and higher performance. [Means for solving the problem]

[0005] A nitride semiconductor laser element according to one embodiment of the present invention comprises a first nitride semiconductor layer having a first conductivity type, a second nitride semiconductor layer having a second conductivity type different from the first conductivity type, an active layer disposed between the first nitride semiconductor layer and the second nitride semiconductor layer, an optical emission side end face and an optical reflection side end face of the active layer intersecting with the side of the second nitride semiconductor layer, and a protective film provided on the optical emission side end face. The protective film includes, in order from the side of the light-emitting side end face, a crystalline first film containing aluminum and / or gallium and oxygen, a crystalline second film made of a nitride film, and a third film containing aluminum and oxygen.

Advantages of the Invention

[0006] According to one embodiment of the present invention, it is possible to provide a nitride semiconductor laser device in which the occurrence of end face damage is suppressed.

Brief Description of the Drawings

[0007] [Figure 1A] It is a perspective view of a nitride semiconductor laser device according to one embodiment of the present invention. [Figure 1B] It is a front view of FIG. 1A. [Figure 1C] It is a cross-sectional view taken along the line IC-IC of FIG. 1A. [Figure 2] It is a high-resolution transmission electron microscope image of the protective film and its vicinity. [Figure 3A] It is an electron diffraction image of the third film. [Figure 3B] It is an electron diffraction image of the second film. [Figure 3C] It is an electron diffraction image of the first film. [Figure 3D] It is an electron diffraction image of the nitride semiconductor laminate. [Figure 4] It is a cross-sectional view showing another example of the nitride semiconductor laser device of the present invention. [Figure 5] It is a partially enlarged view showing another example of the protective film on the side of the light-emitting side end face. [Figure 6] It is a partially enlarged view showing an example of the protective film on the side of the light-reflecting side end face.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments shown below are examples of methods for embodying the technical idea of the present invention, and the present invention is not limited to the following embodiments. Further, in the following description, the same names and reference numerals denote the same or similar members, and detailed descriptions thereof will be omitted as appropriate.

[0009] The nitride semiconductor laser device according to this embodiment (hereinafter, may be referred to as a semiconductor laser device) is shown in FIGS. 1A to 1C. FIG. 1A is a perspective view of the nitride semiconductor laser device of this embodiment. FIG. 1B is a front view of FIG. 1A. FIG. 1C is a cross-sectional view taken along the line IC-IC of FIG. 1A. In FIGS. 1A and 1B, the protective films 24 and 25 are omitted. The nitride semiconductor laser device 10 is an end-face emission laser device. The nitride semiconductor laser device 10 includes a first nitride semiconductor layer 11, a second nitride semiconductor layer 12, an active layer 13 disposed between the first nitride semiconductor layer 11 and the second nitride semiconductor layer 12, and a protective film 24. The first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 have a light-emitting side end face 14 and a light-reflecting side end face 15 as surfaces intersecting with the surface of the second nitride semiconductor layer 12 on the side of the active layer 13. The laminate including the first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 may be referred to as a nitride semiconductor laminate. The protective film 24 is provided on the light-emitting side end face 14. The protective film 24 includes a first film 21 containing aluminum and / or gallium and oxygen, a second film 22 made of a nitride film, and a third film 23 containing aluminum and oxygen in this order from the side of the light-emitting side end face 14. The first film 21 and the second film 22 are crystalline films. This configuration makes it possible to suppress the occurrence of end-face damage to the nitride semiconductor laser element 10. The reasons for this effect are thought to be as follows: First, because the first film 21 in the protective film 24 is an oxygen-containing film, the resistance does not change easily during operation, and a decrease in resistance can be avoided. Also, because the third film 23 is an oxygen-containing film, oxidation of the third film 23 can be suppressed. Furthermore, because the second film 22, which is a nitride film, is present between the first film 21 and the third film 23, oxidation and expansion of the second film 22 by reacting with oxygen in the air or atmosphere can be suppressed. Because the first film 21 is a crystalline film, it is easy to form the second film 22 as a crystalline film, and oxidation reactions between the first film 21 and the end face of the nitride semiconductor laminate are less likely to occur. And because the second film 22 is a crystalline film, it can function as a barrier film against oxygen, and oxidation of the light-emitting end face 14 by oxygen from outside the third film 23 or the nitride semiconductor laser element 10 can be suppressed. These results suggest that the occurrence of end-face damage (COD) can be effectively reduced. By reducing the occurrence of end-face damage, it becomes possible to extend the lifespan of the nitride semiconductor laser element 10. This effect is particularly pronounced in high-power nitride semiconductor laser elements 10. The high-power nitride semiconductor laser element 10 has, for example, a light density of 2 MW / cm². 2 The above describes the elements. The optical density of the nitride semiconductor laser element 10 is 200 MW / cm². 2 The following are also possible: The high-power nitride semiconductor laser element 10 is, for example, an element with an output of 1W or more when the transverse mode is multimode, and may be an element with an output of 5W or more. The high-power nitride semiconductor laser element 10 is, for example, an element with an output of 0.1W or more when the transverse mode is single-mode. The output of the nitride semiconductor laser element 10 may be 3W or less.

[0010] (First nitride semiconductor layer 11, active layer 13, second nitride semiconductor layer 12) The first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 are stacked in this order. A nitride semiconductor laminate including these semiconductor layers can be formed on a substrate 16. The first nitride semiconductor layer 11 exhibits a first conductivity type, and the second nitride semiconductor layer 12 exhibits a second conductivity type. The first conductivity type may be either n-type or p-type. The second conductivity type means a conductivity type different from the first conductivity type. The first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 are made of a semiconductor layer composed of In x Al y Ga 1-x-y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). The first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may contain any one or more of Si, Ge, etc. as n-type impurities. The first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may contain any one or more of Mg, Zn, etc. as p-type impurities. The impurities can be contained, for example, in the range of 5×10 16 / cm 3 ~1×10 21 / cm 3 . The first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may include an undoped layer. The undoped layer refers to a layer in which impurities indicating n-type or p-type are not intentionally doped. The undoped layer has an impurity concentration that does not exceed the detection limit in the analysis results such as secondary ion mass spectrometry (SIMS), or may be a layer with an impurity concentration of less than 1×10 16 / cm 3 . The first nitride semiconductor layer 11 and the second nitride semiconductor layer 12 may each have only one semiconductor layer, but preferably have two or more semiconductor layers. The oscillation peak wavelength of the semiconductor laser formed by the first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 includes 200 nm or more and 700 nm or less.

[0011] (The first nitride semiconductor layer 11) The first nitride semiconductor layer 11 can be a multilayer structure made of nitride semiconductors such as GaN, InGaN, and AlGaN. When the first nitride semiconductor layer 11 is formed on a substrate 16, examples of the first nitride semiconductor layer 11 include having an underlayer, cladding layer, crack prevention layer, intermediate layer, optical guide layer, etc. It may also include semiconductor layers other than those listed above.

[0012] (Active layer 13) The active layer 13 has a quantum well structure. The active layer 13 may have either a multiple quantum well structure or a single quantum well structure. The active layer 13 can be a multilayer structure made of a nitride semiconductor such as GaN or InGaN. When the active layer 13 has a multiple quantum well structure, it may include a well layer, an intermediate barrier layer, and another well layer in that order from the first nitride semiconductor layer 11 side. It may also have multiple well layers and multiple intermediate barrier layers. The well layer is, for example, an InGaN layer. The intermediate barrier layer is, for example, an InGaN layer or a GaN layer. The active layer 13 is, for example, an undoped layer. The composition of the active layer 13 can be appropriately adjusted according to the oscillation wavelength of the nitride semiconductor laser element to be obtained. For example, the well layer can be made of In x Ga 1-x The layer can be made of N, etc. The In composition ratio x can be selected from the range of 0.01 to 0.50. This allows the oscillation peak wavelength of the semiconductor laser to be set in the range of 360 nm to 700 nm. The well layer may be a layer made of GaN or AlGaN.

[0013] (Second nitride semiconductor layer 12) The second nitride semiconductor layer 12 can be a multilayer structure made of nitride semiconductors such as GaN, InGaN, or AlGaN. The second nitride semiconductor layer 12 may include a cladding layer, an optical guide layer, etc. It may also include other semiconductor layers. As long as it constitutes an end-face emitting laser element, the surface, i.e., the upper surface, of the second nitride semiconductor layer 12 may have a ridge 12a, or a current-constricting layer known in the art may be arranged within the second nitride semiconductor layer 12. For example, the second nitride semiconductor layer 12 may be a p-type semiconductor layer with a ridge 12a formed on its upper surface. The second nitride semiconductor layer 12 may also be an n-type semiconductor layer. The ridge 12a functions as an optical waveguide region, and its width is typically between 1 μm and 30 μm. When the nitride semiconductor laser element 10 is driven at high power, the width of the ridge 12a can be between 1.5 μm and 500 μm. The height of the ridge 12a is typically between 0.1 μm and 2 μm. The degree of optical confinement can be appropriately adjusted by adjusting the thickness, material, etc., of the layers constituting the second nitride semiconductor layer 12. The length of the ridge 12a in the resonator direction can be between 200 μm and 5000 μm. The width of the ridge 12a does not have to be the same throughout in the resonator direction, and its side surface may be perpendicular or tapered. In this case, the taper angle is typically between 45 degrees and less than 90 degrees.

[0014] The first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12 are not limited in their crystal planes on the stacking surface. They may be any of the C plane {0001}, M plane {1-100}, A plane {11-20}, or R plane {1-102}, or other planes. For example, the upper surface of the second nitride semiconductor layer 12 is the C plane. When representing crystal planes and directions, crystallographic notation would indicate the opposite direction of 1 with a bar above the 1, but for convenience, this is written as "-1". Individual orientations are indicated by [], aggregate orientations by <>, individual planes by () and aggregate planes by {}.

[0015] (Light-emitting end face 14 and light-reflecting end face 15) The light-emitting end face 14 and the light-reflecting end face 15 are end faces of a semiconductor layer that include at least the light-emitting surface 14a and the light-reflecting surface on both sides of the region corresponding to the optical waveguide region or NFP (near-field pattern) of the active layer 13. The light-emitting end face 14 and the light-reflecting end face 15 are surfaces that intersect with the stacking plane (XY plane in Figure 1A) of the first nitride semiconductor layer 11, the active layer 13, and the second nitride semiconductor layer 12. The light-emitting end face 14 and the light-reflecting end face 15 may be inclined with respect to the stacking direction of the semiconductor layer (direction of arrow Z in Figure 1A), but are preferably parallel. It is also preferable that they intersect perpendicularly with respect to the stacking plane of the semiconductor layer (XY plane in Figure 1A). The light-emitting end face 14 and the light-reflecting end face 15 are surfaces that face each other and are preferably arranged in parallel. A resonator is formed between the light-emitting end face 14 and the light-reflecting end face 15. Here, parallel includes a difference of ±5 degrees. Here, perpendicular includes a difference of ±5 degrees. The light-emitting end face 14 and the light-reflecting end face 15 may be any of the M-plane {1-100}, A-plane {11-20}, C-plane {0001}, or R-plane {1-102}, or any other plane. For example, the light-emitting end face 14 is an M-plane. When the light-emitting end face 14 and the light-reflecting end face 15 are M-planes, these planes may be obtained by cleavage. Cleavage can be performed, for example, by forming a recess by laser processing and then pressing it. The scanning direction of the laser processing and the direction of cleavage may be the same or different. The light-emitting end face 14 does not have to be a strictly M-plane.

[0016] (Protective film 24) The protective film 24 (first protective film) comprises, on the light-emitting end face 14, a first film 21 containing aluminum and / or gallium and oxygen, a second film 22 made of a nitride film, and a third film 23 containing aluminum and oxygen, in order from the light-emitting end face 14 side. The first film 21 and the second film 22 are crystalline films. The protective film 24 provided on the light-emitting end face 14 covers the resonator surface formed on the semiconductor layer, but it does not necessarily have to cover the entire surface of the light-emitting end face 14. The protective film 24 covers at least the light-emitting surface 14a, which is the end face of the region corresponding to the optical waveguide region or NFP of the resonator surface, that is, the region extending to the active layer 13 and a part of its upper and lower layers. The protective film 24 may cover the entire surface of the light-emitting end face 14. A part of the protective film 24 may be placed on a surface other than the resonator surface, for example, the upper surface, side surface, etc. of the semiconductor layer. The first film 21, the second film 22, and the third film 23 constituting the protective film 24 are each made of a material that is transparent to the oscillation wavelength of the nitride semiconductor laser element 10.

[0017] (1st membrane 21) The first film 21 is a film positioned in contact with the light-emitting end face 14. "Contact" means that the first film 21 is not only in direct contact with the resonator surface, but may also be formed on top of a thin film formed on the resonator surface to an extent that provides the effects of the present invention. For example, a thin film may exist formed by pretreatment of the resonator surface, the atmosphere at the start of film formation, etc. The thickness of such a thin film is, for example, less than the thickness of the first film 21. The thickness of such a thin film may be, for example, 3 nm or less, or 1 nm or less. Such a thin film may contain, for example, gallium (Ga) and oxygen (O). The first film 21 may be an oxide film containing aluminum (Al), an oxide film containing Ga, or an oxide film containing both Al and Ga. An example of an Al-containing oxide film is a film made of aluminum oxide, such as Al2O3. An example of a Ga-containing oxide film is a film made of gallium oxide, such as Ga2O3. An example of an Al and Ga-containing oxide film is a film made of aluminum gallium oxide, such as AlGaO. By using such a film, changes in resistance can be suppressed when driving the semiconductor laser element. Furthermore, because the first film 21 is an Al-containing oxide film, a crystalline film can be easily formed. The first film 21 is, for example, a film made of Al2O3. The first film 21 may be an insulating film. The first film 21 is a crystalline film (single crystal, polycrystalline, etc.). In a single crystal, there is almost no variation in the lattice constant within the material, and there is almost no lattice plane tilt. In other words, the atomic arrangement is regularly aligned within the material, and long-range order is maintained. A polycrystalline film is composed of many tiny single crystals, i.e., microcrystals. The crystallinity of such films can be determined by the diffraction pattern obtained by electron beam diffraction. By irradiating the film with an electron beam, an electron diffraction pattern appears corresponding to the magnitude of the lattice constant and the plane direction. For example, in the case of a single crystal, diffraction spots are observed to be regularly aligned. In the case of a polycrystalline film, because it is composed of microcrystals, the orientation of each lattice plane is not aligned, and diffraction spots are observed to be in a complex combined state, or Debye ring may be seen. On the other hand, in the case of amorphous materials, electron diffraction does not occur because the atomic arrangement does not have a long-range periodic structure. Therefore, the diffraction pattern is observed to be free of diffraction spots. Electron diffraction patterns can be observed by cutting the film so that the cross-section is exposed to the edge where the film is formed, and then irradiating it with an electron beam. Differences in crystallinity can be confirmed, for example, by cross-sectional observation using a transmission electron microscope (TEM), scanning transmission electron microscope (STEM), or scanning electron microscope (SEM), or by differences in etching rates with appropriate etchants such as acid or alkaline solutions. The atomic arrangement may also be confirmed by imaging using high-resolution transmission electron microscopy (HRTEM).

[0018] Figure 2 shows an example of a high-resolution transmission electron microscope image of the protective film 24 and its vicinity. The line in the lower right of Figure 2 represents 5 nm. The nitride semiconductor laminate shown in Figure 2 includes an active layer 13. Figure 3A is the electron diffraction pattern in the circle indicated by A in Figure 2, and is the electron diffraction pattern of the third film 23. Figure 3B is the electron diffraction pattern in the circle indicated by B in Figure 2, and is the electron diffraction pattern of the second film 22. Figure 3C is the electron diffraction pattern in the circle indicated by C in Figure 2, and is the electron diffraction pattern of the first film 21. Figure 3D is the electron diffraction pattern in the circle indicated by D in Figure 2, and is the electron diffraction pattern of the nitride semiconductor laminate. From Figure 3C, it was confirmed that the first film 21 is crystalline, that is, the first film 21 is a crystalline film.

[0019] Examples of crystal structures for the first film 21 include cubic, tetragonal, or hexagonal systems. The material, crystallinity, and orientation of the first film 21 can be selected according to the material, crystallinity, and orientation of the light-emitting end face 14 on which the first film 21 is formed. Examples of crystalline films include films that partially contain single crystals and / or polycrystalline materials, or films composed solely of single crystals and / or polycrystalline materials. In other words, the first film 21 does not necessarily have to be strictly single crystal or polycrystalline, and may have a crystal structure close to these or a crystal structure that exhibits characteristics of these crystal structures. The crystallinity of the first film 21 may differ between the region corresponding to the optical waveguide region or NFP and the side of the active layer 13, the first nitride semiconductor layer 11 and the second nitride semiconductor layer 12, and the side in the thickness direction that is far from the active layer 13. In the region corresponding to the optical waveguide region or NFP, it is preferable that the first film 21 is substantially crystalline throughout the thickness direction. "Substantially the entire area in the thickness direction" refers to the entire remaining area excluding regions where the boundaries between adjacent films are difficult to distinguish. For example, the first film 21 is a film that contains polycrystalline material in at least a portion. When observing a cross-section of the first film 21 cut in a direction intersecting the main surface of the active layer 13 and intersecting the light-emitting end face 14 (for example, in directions that intersect perpendicularly to each other), it is possible that more than half of the region adjacent to the active layer 13 is composed of polycrystalline material. The thickness of the first film 21 can be 1 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less, and more preferably 1 nm or more and 10 nm or less. The smaller the thickness of the first film 21, the easier it is to form a film with good crystallinity. The thickness of the first film 21 can be 5 nm or more or 6 nm or more, and may be 8 nm or more. A thickness of 5 nm or more for the first film 21 makes it possible to further extend the lifespan of the nitride semiconductor laser element 10. This is thought to be because the crystallinity of the second film 22 is improved. The thickness of the first film 21 may be 50 nm or less, 20 nm or less, 10 nm or less, or less than 10 nm. For example, the thickness of the first film 21 can be 5 nm or more and 10 nm or less. The thickness of the first film 21 may be less than 10 nm, and may be 5 nm or more and less than 10 nm. The thickness of the first film 21 refers to the length in the direction parallel to the main surface of the active layer 13. Similarly, the thickness of the second film 22 and the thickness of the third film 23 refer to the length in the direction parallel to the main surface of the active layer 13.

[0020] The first film 21 can be formed by methods known in the art. For example, pulsed sputtering, electron cyclotron resonance (ECR) sputtering, magnetron sputtering, ion beam-assisted deposition, laser ablation, chemical vapor deposition (CVD), or a combination of two or more of these methods can be used. Alternatively, these methods may be combined with whole or partial pretreatment. As pretreatment, for example, one or more of the following can be used: irradiation with an inert gas (Ar, He, Xe, etc.) or plasma, irradiation with oxygen or ozone gas, oxidation treatment (heat treatment), or exposure treatment. The first film 21 is preferably deposited by pulse sputtering or ECR sputtering. For example, it can be deposited using an ECR sputtering apparatus. This allows the first film 21 to be obtained as a film with good crystalline properties. When the first film 21 is formed using an ECR sputtering apparatus, the oxygen flow rate during formation is 1.33 × 10⁻⁶. -7 m 3A temperature of 1 / s or higher is preferred. Pretreatment may be performed before forming the first film 21. Examples of pretreatment include treating the light-emitting end face 14 with oxygen plasma. Examples of pulsed sputtering methods include using an oxide target, or using a non-oxide target and sputtering intermittently while irradiating with oxygen gas or plasma, or in an oxygen atmosphere. The ECR sputtering method tends to allow for lower temperatures during film formation than the pulsed sputtering method. This makes it possible to suppress the degradation of the electrode characteristics described later.

[0021] In this way, by forming the first film 21 as an oxygen-containing film in contact with the light-emitting end face 14, changes in resistance can be suppressed when the nitride semiconductor laser element 10 is driven. Furthermore, by forming the first film 21 as a crystalline film, it is easier to form the second film 22 as a crystalline film. In addition, because the thickness of the first film 21 is relatively small, for example, thinner than the third film 23, stress caused by heat during driving can be relieved at the light-emitting end face 14 when the nitride semiconductor laser element 10 is driven. Furthermore, the adhesion between the light-emitting end face 14 and the protective film 24 can be improved.

[0022] (2nd membrane 22) The second film 22 is a film positioned in contact with the first film 21. The second film 22 is a nitride film. Specifically, examples of nitride films include films made of AlN, GaN, AlGaN, etc. Among these, AlN films are preferred. Since AlN films can be formed by the ECR sputtering method, for example, both the first film 21 and the second film 22 can be formed using an ECR sputtering apparatus. The first film 21 and the second film 22 can be grown continuously. The second film 22 is a crystalline film. This allows it to effectively function as an oxygen barrier film. The orientation of the second film 22 is as follows in the thickness direction: M axis <1-100>, A axis <11-20>, C axis <0001> The orientation may be either R-axis or R-axis<1-102> orientation, or any other orientation. For example, the second film 22 is C-axis oriented with respect to the M-axis of the nitride semiconductor stack. In this case, the M-axis of the nitride semiconductor stack and the C-axis of the second film 22 are parallel. The axial orientation of the crystal in the region of the second film 22 adjacent to the active layer 13 may be the same as the axial orientation of the crystal in the region of the second film 22 adjacent to the first nitride semiconductor layer 11 and / or adjacent to the second nitride semiconductor layer 12. This makes it easier to form the second film 22 with good crystallinity. For example, in the second film 22, both the region adjacent to the active layer 13 and the region adjacent to the first nitride semiconductor layer 11 and / or the second nitride semiconductor layer 12 are C-axis oriented. For example, the C-axis of the region of the second film 22 adjacent to the active layer 13 is parallel to the C-axis of the region of the second film 22 adjacent to the first nitride semiconductor layer 11 and / or the second nitride semiconductor layer 12. The region of the second film 22 adjacent to a specific layer (e.g., the active layer 13) refers to the region of the second film 22 sandwiched between an extended plane (virtual plane) obtained by extending one main plane of that layer and an extended plane (virtual plane) obtained by extending the other main plane. The crystal axial orientation of the second film 22 may be the same throughout its entirety. The crystallinity of each region of the second film 22 can be evaluated using a cross-section cut in a direction intersecting the main plane of the active layer 13 (e.g., perpendicular to it). The thickness of the second film 22 can be between 5 nm and 500 nm, and may also be between 5 nm and 200 nm, between 5 nm and 100 nm, or between 5 nm and 50 nm. By setting the thickness of the second film 22 within this range, a film with good crystallinity can be obtained, and it can effectively function as an oxygen barrier film. It is thought that the occurrence of cracks is easily suppressed when the thickness of the second film 22 is 50 nm or less. To adjust the reflectivity of the protective film 24, the thickness of the second film 22 may be greater than 50 nm. The second film 22 can be deposited by known methods such as sputtering and ECR sputtering. Examples of sputtering methods include using a nitride target and sputtering with a non-nitride target while irradiating with nitrogen gas or plasma, or in a nitrogen atmosphere. Regarding the example of the second film 22 shown in Figure 2, Figure 3B confirms that the second film 22 is crystalline, that is, the second film 22 is a crystalline film.

[0023] (Third membrane 23) The third film 23 is a film positioned in contact with the second film 22. The third film 23 is a film containing Al and O. The third film 23 may be an Al-containing oxide film or an Al-containing oxynitride film. The third film 23 may be a film made of aluminum oxide. By using such a film, oxidation of the third film 23 can be suppressed, thereby reducing the possibility of oxygen reaching the nitride semiconductor laminate. An Al-containing oxide film is considered to be less prone to oxidation of the third film 23 when the nitride semiconductor laser element 10 is driven than an Al-containing oxynitride film. As a result, it becomes possible to further extend the lifespan of the nitride semiconductor laser element 10. The third film 23 is, for example, a film made of Al2O3.

[0024] The third film 23 may be a crystalline film or a film containing an amorphous structure. An amorphous structure means that there is no periodic structure like the atomic arrangement in a crystal, that is, the atomic arrangement is irregular and lacks long-range order. Preferably, the third film 23 is an amorphous film or a film containing both an amorphous and a crystalline structure, and more preferably a film consisting only of an amorphous structure. This makes it easier to make the thickness of the third film 23 greater than the thickness of the first film 21 and / or the second film 22. Furthermore, by driving the nitride semiconductor laser element 10, a part of the third film 23, for example, a part on the active layer 13 side, may become a crystalline film. This is thought to further extend the lifespan of the nitride semiconductor laser element 10. For example, such crystallization can occur when the third film 23 is a film made of Al2O3.

[0025] The thickness of the third film 23 is preferably greater than the thickness of the first film 21. The thickness of the third film 23 may be less than the thickness of the second film 22, but is preferably greater. The thickness of the third film 23 can be three times or more the thickness of the first film 21, and may be ten times or more. The thickness of the third film 23 is preferably 10 nm to 1000 nm, and more preferably 50 nm to 500 nm. By setting the thickness of the third film 23 within this range, the total thickness of the protective film 24 can be increased, thereby reducing the possibility that oxygen from outside the nitride semiconductor laser element 10 can pass through the protective film 24 and reach the nitride semiconductor laminate. This is thought to have an advantageous effect on extending the lifespan. In particular, a more significant effect can be obtained when the first film 21 and the second film 22 are formed as thinner films than the third film 23 in order to perform their respective functions. The thickness of the third film 23 may be within the range of ±25% of (λ / 2n3) × 2. λ is the oscillation wavelength of the nitride semiconductor laser element 10, and n3 is the refractive index of the third film 23 at the oscillation wavelength λ. This makes it possible to extend the lifespan of the nitride semiconductor laser element 10 compared to when the thickness of the third film 23 is smaller. This is thought to be because increasing the thickness of the protective film 24 increases the time it takes for fractures progressing from inside the nitride semiconductor laser element 10 to reach the outer surface of the protective film 24. As shown in Figure 4, a portion of the protective film 24 may be provided on the upper and / or lower sides of the nitride semiconductor laminate. Figure 4 is a cross-sectional view showing another example of the nitride semiconductor laser element 10. By providing the protective film 24 in this way, it is thought that the distance it takes for fractures to reach the outer surface of the nitride semiconductor laser element 10 can be increased by the thickness of the protective film 24 on the upper and / or lower sides of the nitride semiconductor laminate. Therefore, it is possible to extend the lifespan of the nitride semiconductor laser element 10.

[0026] The protective film 24 may further include other films provided on the outside of the third film 23. This may increase the thickness of the protective film 24 and extend the lifespan of the nitride semiconductor laser element 10. As shown in Figure 5, the protective film 24 may have a fourth film 26 provided on the outside of the third film 23. Figure 5 is a partially enlarged view showing another example of the protective film 24 on the light-emitting end face 14 side. The fourth film 26 is provided on the side of the third film 23 opposite to the second film 22. The thickness of the fourth film 26 may be greater than the thickness of the third film 23. By providing the fourth film 26, the distance over which fractures propagating from the inside of the nitride semiconductor laser element 10 reach the outer surface of the protective film 24 can be increased compared to when the fourth film 26 is not provided. The refractive index of the fourth film 26 at the oscillation wavelength λ may be smaller than the refractive index of the third film 23 at the oscillation wavelength λ. For example, the thickness of the third film 23 can be set to a thickness within ±20% of λ / 2n3, and the thickness of the fourth film 26 can be set to a thickness within ±5% of λ / 2n4, where n4 is the refractive index of the fourth film 26 at the oscillation wavelength λ. The fourth film 26 can be made of, for example, silicon oxide (e.g., SiO2). This has the advantage of suppressing deterioration of initial characteristics due to light absorption and heat generation. The outermost film of the protective film 24 may be the third film 23. In the protective film 24, other films may be arranged between the second film 22 and the third film 23. The third film 23 can be formed by known methods such as sputtering and ECR sputtering. For example, it can be formed using an ECR sputtering apparatus. When the first film 21 and the third film 23 are formed using an ECR sputtering apparatus, the oxygen flow rate during the formation of the third film 23 is less than the oxygen flow rate during the formation of the first film 21. This allows the first film 21 to be formed as a crystalline film and the third film 23 to be formed as an amorphous film. Regarding the example of the third film 23 shown in Figure 2, Figure 3A confirms that the third film 23 is amorphous, meaning that the third film 23 is an amorphous structured film.

[0027] By having such a configuration, it is possible to suppress the occurrence of end-face damage to the nitride semiconductor laser element 10 and extend the lifespan of the nitride semiconductor laser element 10.

[0028] (Protective film 25) A protective film 25 (second protective film) is provided on the light-reflecting end face 15. The protective film 25 has a different or the same film structure as the protective film 24 on the light-emitting end face 14. The reflectivity of the protective film 25 with respect to the oscillation wavelength of the nitride semiconductor laser element 10 is higher than the reflectivity of the protective film 24 with respect to the oscillation wavelength of the nitride semiconductor laser element 10. The protective film 25 on the light-reflecting end face 15 side may have the same film as the multilayer films of the first film 21, second film 22, and third film 23 described above. The protective film 25 may be made of oxides such as Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B, and Ti (especially Al2O3, SiO2, Nb2O5, TiO2, ZrO2, etc.), nitrides (especially AlN, AlGaN, BN, etc.), fluorides, or combinations of two or more of these. When forming the same film as the multilayer films of the first film 21, second film 22, and third film 23, it may be formed with a different thickness than the protective film 24 on the light-emitting end face 14 side. Preferably, the protective film 25 is made of a material that is transparent to and / or reflects light with respect to the oscillation wavelength of the nitride semiconductor laser element 10. The protective film 25 may be a single layer or a multilayer.

[0029] For example, the protective film 25 on the light-reflecting end face 15 can be a laminated film of Si oxide and Zr oxide, a laminated film of Al oxide and Zr oxide, a laminated film of Si oxide and Ti oxide, a laminated film of Al oxide, Si oxide and Zr oxide, or a laminated film of Si oxide, Ta oxide and Al oxide. The lamination period and other parameters can be adjusted as appropriate to match the desired reflectivity. The thickness of such protective film 25 is not particularly limited, and examples include 100 nm to 4000 nm, 300 nm to 3000 nm, and 500 nm to 2000 nm. For example, the thickness of protective film 25 is greater than the thickness of protective film 24.

[0030] The protective film 25 is, for example, a multilayer film. The multilayer film can have a structure in which films with relatively low refractive indices and films with relatively high refractive indices are alternately stacked. The film in contact with the light-reflecting end face 15 of the multilayer film may be a film with a relatively low refractive index or a film with a relatively high refractive index. As shown in Figure 6, the protective film 25 may have a first portion 25a that is in contact with the light-reflecting end face 15 and a second portion 25b that is in contact with the first portion 25a. Figure 6 is a partially enlarged view showing an example of the protective film 25 on the light-reflecting end face 15 side. The thickness of the protective film 25 is preferably ±5% of an odd multiple of λ / 4n, and more preferably an odd multiple of λ / 4n. This reduces the probability of optical damage occurring at the light-reflecting end face 15 when the nitride semiconductor laser element 10 is driven. Hereinafter, λ is the oscillation wavelength of the nitride semiconductor laser element 10, and n is the refractive index of each film at the oscillation wavelength λ. The thickness of the protective film 25 refers to its length in the direction parallel to the main surface of the active layer 13. The second portion 25b consists of alternating high-refractive-index films 254 and low-refractive-index films 255. The first portion 25a consists of one or more films. The film in the first portion 25a that is in contact with the second portion 25b has a refractive index different from that of either the high-refractive-index film 254 or the low-refractive-index film 255. By combining the first portion 25a and the second portion 25b, light can be reflected at the interface between the first portion 25a and the second portion 25b, thereby improving the reflectivity of the protective film 25. This improves the optical output of the nitride semiconductor laser element 10. The distance from the light-reflecting end face 15 to the interface between the first portion 25a and the second portion 25b is preferably 50 nm or more and 200 nm or less. This further improves the reflectivity of the protective film 25 and further improves the optical output of the nitride semiconductor laser element 10. Note that the distance here refers to the shortest distance. The protective film 25 may consist only of the first part 25a and the second part 25b, or it may have another film.

[0031] The first portion 25a is preferably a multilayer structure having a film with a relatively low refractive index and a film with a relatively high refractive index. This further improves the reflectivity of the protective film 25. For example, the film with a relatively low refractive index in the first portion 25a is in contact with the high refractive index film 254 of the second portion 25b. Alternatively, the film with a relatively high refractive index in the first portion 25a is in contact with the low refractive index film 255 of the second portion 25b. The film in the second portion 25b that is in contact with the first portion 25a is preferably a film with a higher refractive index than the film in the first portion 25a that is in contact with the second portion 25b, and more preferably a film with a higher refractive index than any of the films constituting the first portion 25a. This further improves the reflectivity of the protective film 25. The low refractive index film 255 of the second portion 25b can be, for example, a silicon oxide film (e.g., an SiO2 film). The high refractive index film 254 of the second portion 25b can be, for example, a tantalum oxide film (e.g., Ta2O5).

[0032] The first portion 25a may have a fifth film 251, a sixth film 252, and a seventh film 253. The first portion 25a may have, in order from the light-reflecting end face 15 side, a crystalline fifth film 251 containing aluminum and / or gallium and oxygen, a crystalline sixth film 252 made of a nitride film, and a seventh film 253 containing aluminum and oxygen. The fifth film 251 may employ the material, thickness, and formation method described for the first film 21. The sixth film 252 may employ the material, thickness, and formation method described for the second film 22. The seventh film 253 may employ the material, thickness, and formation method described for the third film 23. Since the first portion 25a is in contact with the light-reflecting end face 15, having such a fifth film 251, sixth film 252, and seventh film 253 can provide the same effect as the protective film 24. The fifth film 251 may be positioned in contact with the light-reflecting end face 15. The thicknesses of the fifth film 251, the sixth film 252, and the seventh film 253 may each be λ / 4n or less. This allows the interface between the first portion 25a and the second portion 25b to be positioned relatively close to the light-reflecting end face 15, thereby improving the reflectivity of the protective film 25 and further improving the optical output of the nitride semiconductor laser element 10. For example, the first portion 25a may consist only of the fifth film 251, the sixth film 252, and the seventh film 253.

[0033] (Circuit board 16) The substrate 16 may be an insulating substrate or a conductive substrate. For example, a nitride semiconductor substrate made of GaN or the like can be used as the substrate 16. The first main surface of the substrate 16, which is the semiconductor layer formation surface, may be a C-plane, R-plane, M-plane, etc., and is for example a C-plane. The first main surface and / or the second main surface opposite the first main surface may have an off-angle of 0° to 10°. The thickness of the substrate 16 may be 10 μm to 10 mm.

[0034] (Implantation membrane 18, first electrode 17, second electrode 19, pad electrode 20) The nitride semiconductor laser element 10 can have an embedded film 18 provided on the upper surface of the second nitride semiconductor layer 12, for example, on the side surface of the ridge 12a and on the upper surface of the second nitride semiconductor layer 12 that is continuous with the side surface of the ridge 12a. The embedded film 18 is preferably formed of a material having a lower refractive index than the second nitride semiconductor layer 12. Examples of embedded films 18 include single-layer or multi-layer films of insulating films such as oxides, nitrides, or oxiditrides of Zr, Si, V, Hf, Ta, Al, Ce, In, Sb, and Zn. The embedded film 18 can be formed by methods known in the art, as exemplified in the method for forming the first film 21.

[0035] If there is a substrate 16 on the underside of the first nitride semiconductor layer 11, for example, the first electrode 17 can be provided on the underside of the substrate 16. If the substrate 16 is a semiconductor substrate, the substrate 16 has the same conductivity type as the first nitride semiconductor layer 11. The first electrode 17 is provided, for example, over almost the entire underside of the substrate 16. A second electrode 19 can be provided on the upper surface of the second nitride semiconductor layer 12, for example, on the upper surface of the ridge 12a, and a pad electrode 20 can be provided on top of it. The first electrode 17 and the second electrode 19 can be formed from a single-layer or multilayer film of a conductive oxide containing at least one selected from metals or alloys such as Ni, Rh, Cr, Au, W, Pt, Ti, Al, Pd, etc., and Zn, In, Sn. Examples of conductive oxides include ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), and GZO (Gallium-doped Zinc Oxide). The thickness of the electrodes is usually sufficient to function as electrodes for a semiconductor laser element. For example, a thickness of 0.1 μm to 2 μm is possible.

[0036] The first electrode 17 and the second electrode 19 may be provided on the first main surface side and the second main surface side of the nitride semiconductor laminate, respectively, or both may be provided on either the first main surface side or the second main surface side. The embedded film 18, the first electrode 17, the second electrode 19, and the pad electrode 20 may be spaced apart from or in contact with the protective film 24 described above. The embedded film 18, the first electrode 17, the second electrode 19, and the pad electrode 20 may be covered by the protective film 24, or they may be covered by the protective film 24. It is preferable that the embedded film 18 and the second electrode 19 are covered by the protective film 24. This can suppress peeling of the embedded film 18 and the second electrode 19.

[0037] (Examples) As shown in Figures 1A to 1C, a gallium nitride-based semiconductor laser device with an oscillation wavelength peak of approximately 445 nm was fabricated. MOCVD equipment was used to fabricate epitaxial wafers that would become semiconductor laser elements. Trimethylgallium (TMG), triethylgallium (TEG), trimethylaluminum (TMA), trimethylindium (TMI), ammonia (NH3), silane gas, and bis(cyclopentadienyl)magnesium (Cp2Mg) were used as raw materials as appropriate. On an n-type GaN substrate (substrate 16) with the C-plane as the growth surface, an n-side semiconductor layer as the first nitride semiconductor layer 11, an active layer 13, and a p-side semiconductor layer as the second nitride semiconductor layer 12 were grown, and a stripe-shaped ridge 12a with a length of 1200 μm in the direction parallel to the resonator length was formed on the surface of the p-side semiconductor layer. Next, a p-electrode made of ITO (200 nm) was formed as a second electrode 19 on the upper surface of the p-side semiconductor layer, and an embedded film 18 made of SiO2 was formed on the side surface of the ridge 12a and the upper surface of the p-side semiconductor layer outside of it. The embedded film 18 was formed such that a part of it partially covered the p-electrode. A pad electrode 20 was formed on the p electrode in a continuous pattern using Ni (8 nm) / Pd (200 nm) / Au (400 nm) / Pt (200 nm) / Au (700 nm). Subsequently, the substrate 16 was polished from the side opposite to the growth surface of the first nitride semiconductor layer 11 to a thickness of 80 μm, and an n-electrode consisting of Ti (8 nm) / Pt (100 nm) / Au (300 nm) was formed on the polished surface as the first electrode 17. Next, the substrate 16 was cleaved in a bar shape from the side where the n-electrode was formed, and the cleaved surface became the resonator surface, i.e., the light-emitting end face 14 and the light-reflecting end face 15. The light-emitting end face 14 and the light-reflecting end face 15 of the obtained bar were surface-treated by exposing them to oxygen plasma using an ECR sputtering apparatus. At this time, for example, the flow rate of O2 was 3.33 × 10⁻¹⁰. -7 m 3 The process was performed using a microwave at 500W for 10 minutes, with a setting of / s. Subsequently, an Al target is used on the light-emitting end face 14, and the Ar flow rate is 5 × 10 -7 m 3 / s, oxygen flow rate is 1.67 × 10 -7 m 3 A first film 21 made of Al2O3 was formed using a microwave at 500W at 1 / s. A second film 22 was similarly formed by changing the oxygen gas to nitrogen gas, and then a third film 23 was similarly formed by changing the nitrogen gas to oxygen gas, thereby forming a protective film 24. In the semiconductor laser elements of Examples 1 and 2 and the Comparative Example, the first film 21, the second film 22, and the third film 23 were formed with the thicknesses shown in Table 1. In the semiconductor laser elements of Examples 1 and 2 and the Comparative Example, the reflectivity of the protective film 24 was approximately 15%. The oxygen flow rate during the formation of the first film 21 was 1.67 × 10⁻¹⁰ -7 m 3 Assuming a flow rate of / s, the oxygen flow rate during the formation of the third membrane 23 is 8.33 × 10⁻¹⁰. -8 m 3 The value was set to / s. A protective film 25 containing a multilayer structure in which multiple layers of SiO2 and Ta2O5 are alternately stacked was formed on the light-reflecting end face 15. Subsequently, the bar was cut in a direction perpendicular to the cleavage plane to obtain a nitride semiconductor laser element 10. [Table 1] Seven semiconductor laser elements were fabricated for each of Examples 1 and 2 and the Comparative Example, with a light density of approximately 36 MW / cm². 2A life test was conducted by continuously oscillating the device for approximately four months, and the number of sudden deaths was measured. As a result, there were 3 in Example 1, 0 in Example 2, and 5 in the Comparative Example.

[0038] These results confirm that by providing the first film 21, the second film 22, and the third film 23, the occurrence of end-face damage to the nitride semiconductor laser element 10 can be suppressed. Furthermore, it was confirmed that this makes it possible to extend the lifespan of the nitride semiconductor laser element 10.

[0039] Through the information described herein so far, the following technical matters are disclosed: (Item 1) A first nitride semiconductor layer having a first conductivity type, a second nitride semiconductor layer having a second conductivity type different from the first conductivity type, an active layer disposed between the first nitride semiconductor layer and the second nitride semiconductor layer, a light-emitting end face and a light-reflecting end face of the active layer intersecting with the side of the second nitride semiconductor layer, and a protective film provided on the light-emitting end face. The protective film comprises, in order from the light-emitting end face side, a crystalline first film containing aluminum and / or gallium and oxygen, a crystalline second film made of a nitride film, and a third film containing aluminum and oxygen, in a nitride semiconductor laser element. (Item 2) The nitride semiconductor laser element according to Item 1, wherein the first film is an oxide film containing aluminum. (3) The nitride semiconductor laser element according to item 1 or 2, wherein the third film is an oxide film containing aluminum. (Item 4) The nitride semiconductor laser element according to any one of items 1 to 3, wherein the second film is a film made of AlN. (Item 5) A nitride semiconductor laser element according to any one of items 1 to 4, wherein the thickness of the first film is less than 10 nm. (Item 6) The nitride semiconductor laser element according to any one of items 1 to 5, wherein the thickness of the third film is three times or more the thickness of the first film. (Item 7) A nitride semiconductor laser element according to any one of items 1 to 6, wherein the first film and the second film are thinner than the third film. (Clause 8) The nitride semiconductor laser element according to any one of Clauses 1 to 7, wherein the first film is an insulating film. (Clause 9) The nitride semiconductor laser element according to any one of Clauses 1 to 8, wherein the third film is an amorphous film or a film comprising an amorphous structure and a crystalline structure. (Clause 10) The nitride semiconductor laser element according to any one of Clauses 1 to 9, wherein the axial orientation of the crystal in the region of the second film adjacent to the active layer is the same as the axial orientation of the crystal in the region of the second film adjacent to the first nitride semiconductor layer and / or adjacent to the second nitride semiconductor layer. (Item 11) The protective film comprises a fourth film provided on the side of the third film opposite to the second film, A nitride semiconductor laser element according to any one of items 1 to 10, wherein the thickness of the fourth film is greater than the thickness of the third film. (Item 12) The protective film is a first protective film, The nitride semiconductor laser element comprises a second protective film provided on the light-reflecting end face, The second protective film has a first portion that is in contact with the light-reflecting end face and a second portion that is in contact with the first portion. The first part described above is a multilayer structure having a film with a relatively low refractive index and a film with a relatively high refractive index. The second part is a nitride semiconductor laser element according to any one of claims 1 to 11, wherein a high refractive index film and a low refractive index film are arranged alternately. (Clause 13) The nitride semiconductor laser element according to Clause 12, wherein the first part comprises, in order from the light-reflecting end face, a fifth crystalline film containing aluminum and / or gallium and oxygen, a sixth crystalline film made of a nitride film, and a seventh film containing aluminum and oxygen. [Explanation of Symbols]

[0040] 10 Nitride semiconductor laser elements 11. First nitride semiconductor layer 12. Second Nitride Semiconductor Layer 12a Ridge 13 Active layer 14 Light output side end face 14a Light-emitting surface 15 Light reflecting side end face 16 circuit boards 17 1st electrode 18 Implantation membrane 19 2nd electrode 20 pad electrodes 24, 25 Protective film 21 1st membrane 22 Second membrane 23 Third membrane 26 4th membrane 25a Part 1 25b Part 2 251 5th membrane 252 6th membrane 253 7th membrane 254 High refractive index film 255 Low refractive index film

Claims

1. a first nitride semiconductor layer of a first conductivity type; a second nitride semiconductor layer of a second conductivity type different from the first conductivity type; an active layer disposed between the first nitride semiconductor layer and the second nitride semiconductor layer; a light-emitting side end face and a light-reflecting side end face intersecting with a surface of the active layer on the second nitride semiconductor layer side; a first protective film provided on the light-emitting side end face; and a second protective film provided on the light-reflecting side end face, The first protective film and / or the second protective film are a nitride semiconductor laser element comprising, in order from the light-emitting end face side, a crystalline first film containing aluminum and / or gallium and oxygen, a crystalline second film made of a nitride film, and a third film containing aluminum and oxygen.

2. 2. The nitride semiconductor laser device according to claim 1, wherein the first film is an oxide film containing aluminum.

3. 2. The nitride semiconductor laser device according to claim 1, wherein the third film is an oxide film containing aluminum.

4. 2. The nitride semiconductor laser device according to claim 1, wherein the second film is a film made of AlN.

5. 2. The nitride semiconductor laser device according to claim 1, wherein the first film has a thickness of less than 10 nm.

6. 2. The nitride semiconductor laser device according to claim 1, wherein the thickness of said third film is at least three times the thickness of said first film.

7. 2. The nitride semiconductor laser device according to claim 1, wherein the first film and the second film are thinner than the third film.

8. 2. The nitride semiconductor laser device according to claim 1, wherein the first film is made of an insulating film.

9. 2. The nitride semiconductor laser device according to claim 1, wherein the third film is a film having an amorphous structure or a film containing an amorphous structure and a crystalline structure.

10. 2. The nitride semiconductor laser element according to claim 1, wherein the axial orientation of the crystal in the region of the second film adjacent to the active layer is the same as the axial orientation of the crystal in the region of the second film adjacent to the first nitride semiconductor layer and / or the region of the second film adjacent to the second nitride semiconductor layer.

11. the first protective film includes the first film, the second film, and the third film, the first protective film includes a fourth film provided on the opposite side of the third film from the second film, 2. The nitride semiconductor laser device according to claim 1, wherein the fourth film has a thickness greater than that of the third film.

12. the second protective film has a first portion disposed in contact with the light-reflecting side end face and a second portion disposed in contact with the first portion, the first portion has a multilayer structure including the first film, the second film, and the third film, 12. The nitride semiconductor laser device according to claim 1, wherein the second portion is formed by alternately arranging high-refractive-index films and low-refractive-index films.

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