Nitride semiconductor laser element, manufacturing method of them, and light-emitting device

Abstract

To provide a semiconductor laser element capable of obtaining a high output in a vertical single mode.SOLUTION: In a distribution feedback type semiconductor laser element 100, a lamination structure 110 contains: a GaN substrate 112, an n-type semiconductor layer 120, an active layer 114, and a p-type semiconductor layer 130, and a ridge type waveguide is formed therein. A first diffraction grating 150 is formed to both adjacent to the ridge type waveguide so as to be adjacent. A depth d of a groove of the first diffraction grating is within a range of 50nm≤d≤200nm, a duty ratio duty is within a range of an inequality (1) using numerical constants a, b, c, and n regulated against a dimension of a diffraction light. [equation 1]SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a nitride semiconductor laser device. [Background technology]

[0002] Until now, 254 nm ultraviolet germicidal lamps have been widely used for sterilization purposes. However, there is a risk of developing skin cancer and keratitis when irradiated to humans. In contrast, in recent years, many medical institutions and universities both in Japan and overseas have reported that 222 nm ultraviolet light using KrCl excimer lamps is much safer. In addition, its effectiveness against the new coronavirus is also being verified. This virus inactivation system using KrCl excimer lamps can inactivate viruses without restricting human activity in medical institutions, schools, public and commercial facilities, restaurants, etc., and is attracting attention as a system that can contribute to both suppressing the pandemic and maintaining social activity.

[0003] To further improve the quietness and miniaturization of this virus inactivation system, it is possible to replace the KrCl excimer lamp with a semiconductor light-emitting device equipped with a semiconductor light-emitting element. However, there are still no semiconductor light-emitting elements that emit light at around 222 nm. Therefore, it is possible to use harmonic generation by a wavelength conversion element to convert 444 nm light into 222 nm second harmonic (SHG: Second harmonic Generation) waves.

[0004] In order to increase the conversion efficiency of SHG waves, a single-longitudinal mode, high-output semiconductor laser is required as a 444 nm light source. Generally, a distributed feedback laser (DFB-LD: Distributed FeedBack Laser Diode) is used as a single-longitudinal mode laser. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] "InGaAs / AlGaAs Quantum Well Laterally-Coupled Distributed Feedback Laser", Japanese Journal of Applied Physics, volume 43, Number 5R, pp.25-49 (2004) [Non-Patent Document 2] "Continuous-wave operation of a semipolar InGaN distributed-feedback blue laser diode with a first-order indium tin oxide surface grating", Optics Letters vol.44 pp.3106-3109 (2019) Summary of the Invention [Problem to be solved by the invention]

[0006] GaN-based materials are widely used as semiconductor light-emitting elements that emit light in the ultraviolet and visible wavelength bands. However, it is difficult to obtain a sufficient refractive index difference with GaN-based materials, and it has been difficult to increase the optical coupling coefficient κ of the diffraction grating.

[0007] The present disclosure has been made in light of the above-mentioned circumstances, and an exemplary purpose of an embodiment of the present disclosure is to provide a semiconductor laser device capable of obtaining a high output in a single longitudinal mode. [Means for solving the problem]

[0008] An embodiment of the present disclosure relates to a distributed feedback semiconductor laser device. The semiconductor laser device includes a GaN substrate, a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer, a laminated structure in which a ridge-type waveguide is formed, and a first diffraction grating formed adjacent to both sides of the ridge-type waveguide. The groove depth d of the first diffraction grating is within the range of 50 nm≦d≦200 nm, and the duty ratio duty is within the range of inequality (1) using constants a, b, c, and n defined for the order of diffracted light.

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[0009] Another aspect of the present disclosure relates to a method for manufacturing a distributed feedback semiconductor laser device. The method includes the steps of forming a laminated structure including a GaN substrate, a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer, forming a ridge stripe structure in the laminated structure, forming a first diffraction grating adjacent to the ridge stripe structure, and forming an insulating film inside the grooves of the first diffraction grating. The depth d of the grooves of the first diffraction grating is within the range of 54.9 nm≦d≦200 nm, and the duty ratio duty is within the range of inequality (1) using constants a, b, c, and n defined for the order of diffracted light.

[0010] Any combination of the above components, or mutual substitution of components or expressions between methods, devices, systems, etc., are also effective as aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. Effect of the Invention

[0011] According to a semiconductor laser device according to an aspect of the present disclosure, high output can be obtained in a single longitudinal mode. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view of a distributed feedback semiconductor laser device according to a first embodiment. [Diagram 2] FIG. 1 is a diagram illustrating an interaction between light and a diffraction grating. [Diagram 3] FIG. 13 is a diagram showing the relationship between the duty ratio of a diffraction grating and an optical coupling coefficient κ. [Figure 4] FIG. 13 is a diagram showing the relationship between the groove depth d and the duty ratio duty when the optical coupling coefficient κ is 10 cm −1 . [Diagram 5] FIG. 11 is a perspective view of a semiconductor laser device according to a second embodiment. [Figure 6] 4A and 4B are diagrams illustrating interactions between light and a first diffraction grating and a second diffraction grating. [Figure 7] FIG. 4 is a diagram showing an optical coupling coefficient κ of the first and second embodiments. [Figure 8] 1A to 1C are diagrams illustrating a manufacturing method of a semiconductor laser element. [Figure 9] FIG. 11 is a perspective view of a semiconductor laser device according to a third embodiment. [Figure 10] FIG. 2 is a cross-sectional view showing a diffraction grating having a phase shift region. [Figure 11] 1 is a diagram showing a light emitting device according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Overview of the embodiment) A summary of some exemplary embodiments of the present disclosure is provided. This summary is intended as a prelude to the more detailed description that follows, or as a basic understanding of the embodiments. This summary is intended to provide a simplified description of some concepts of one or more embodiments, and is not intended to limit the scope of the invention or disclosure. Additionally, this summary is not intended to be a comprehensive overview of all possible embodiments, nor is it intended to limit essential elements of the embodiments. For convenience, the term "one embodiment" may refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed in this specification.

[0014] (Overview of the embodiment) A distributed feedback semiconductor laser device according to one embodiment includes a GaN substrate, a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer, and includes a stacked structure in which a ridge-type waveguide is formed, and a first diffraction grating formed adjacent to both sides of the ridge-type waveguide. The groove depth d of the first diffraction grating is within the range of 50 nm≦d≦200 nm, and the duty ratio duty is within the range of inequality (1) using constants a, b, c, and n defined for the order of diffracted light.

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[0015] By keeping the duty ratio within the range defined by equation (1) using the depth of the grooves of the diffraction grating as a parameter, a large optical coupling coefficient κ can be obtained, enabling the semiconductor laser element to have a high output.

[0016] In one embodiment, the order may be 3, a=1000000, b=0.889, c=75.3, n=4, and 75.3 nm≦d≦200 nm.

[0017] In one embodiment, the order may be 1, a=7500000, b=0.738, c=54.9, n=8, and 54.9 nm≦d≦200 nm.

[0018] In one embodiment, the order may be 5, a=7500000, b=0.929, c=88.9, n=4, and 88.9 nm≦d≦200 nm.

[0019] In one embodiment, the order may be 7, a=23000000, b=0.947, c=100.6, n=4, and 100.6 nm≦d≦200 nm.

[0020] In one embodiment, the semiconductor laser element may further include a second diffraction grating formed on the upper surface of the ridge-type waveguide. The first diffraction grating and the second diffraction grating have the same periodic structure and are continuous when viewed in a plan view. By providing the second diffraction grating, the optical coupling coefficient can be further increased. Furthermore, since the first diffraction grating and the second diffraction grating have the same periodic structure, they can be formed simultaneously using the same manufacturing process. This facilitates manufacturing.

[0021] In one embodiment, the bottom surface of the grooves of the second grating may be higher than the bottom surface of the grooves of the first grating.

[0022] In one embodiment, the first diffraction grating may have a phase shift region. In one embodiment, the oscillation wavelength is λ, m is 0 or any positive integer, n 0r is the average refractive index experienced by light, the length of the phase shift region is λ / 4n 0r ×(2m+1).

[0023] In one embodiment, the phase shift region may be provided at a position that divides the space between the low reflection end face and the high reflection end face of the semiconductor laser element in a range of 6:4 to 8:2.

[0024] In one embodiment, at least in the portion of the first diffraction grating through which light leaks, the grooves are covered with an insulating film, and the insulating film may contain at least one or more elements selected from the group consisting of Si, Zr, Al, Ta, Nb, Ti, In, O, and N.

[0025] A light emitting device according to an embodiment may include any one of the distributed feedback semiconductor laser elements described above, a nonlinear optical element that generates a second harmonic of the emitted light from the distributed feedback semiconductor laser element, and a filter that transmits the second harmonic. With this configuration, it is possible to generate safe ultraviolet light with high efficiency.

[0026] A method for manufacturing a distributed feedback semiconductor laser device according to an embodiment includes the steps of forming a laminated structure including a GaN substrate, a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer, forming a ridge stripe structure in the laminated structure, forming a first diffraction grating adjacent to the ridge stripe structure, and forming an insulating film inside the grooves of the first diffraction grating. The depth d of the grooves of the first diffraction grating is within the range of 54.9 nm≦d≦200 nm, and the duty ratio duty is within the range of inequality (1) using constants a, b, c, and n defined for the order of diffracted light.

[0027] The manufacturing method according to an embodiment may further include a step of forming a second diffraction grating in a region adjacent to the ridge stripe structure simultaneously with the formation of the first diffraction grating.

[0028] In one embodiment, the insulating film may be formed by an atomic layer deposition (ALD) method.

[0029] (Embodiment) Hereinafter, preferred embodiments will be described with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the embodiments are illustrative and do not limit the disclosure or invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure or invention.

[0030] In addition, the dimensions (thickness, length, width, etc.) of each component shown in the drawings may be enlarged or reduced as appropriate for ease of understanding. Furthermore, the dimensions of multiple components do not necessarily represent their relative sizes, and even if a component A is drawn thicker than another component B on the drawings, component A may actually be thinner than component B.

[0031] (Embodiment 1) 1 is a perspective view of a distributed feedback semiconductor laser device 100 according to embodiment 1. The semiconductor laser device 100 includes an n-type GaN substrate 112, an n-type semiconductor layer 120, an active layer 114, a p-type semiconductor layer 130, an n-side electrode 140, a p-side electrode 142, and a diffraction grating 150.

[0032] The GaN substrate 112 is a nitride semiconductor. x Al y Ga 1-x-y N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). To generate blue laser light of 444 nm, the material of the GaN substrate 112 can be selected as GaN (x=y=0).

[0033] An n-type semiconductor layer 120, an active layer 114, and a p-type semiconductor layer 130 are formed in this order on an n-type GaN substrate 112 by epitaxial growth to form a layered structure 110.

[0034] The n-type semiconductor layer 120 may include an n-type cladding layer 122 and an n-type guide layer 124. For example, the material of the n-type cladding layer 122 is n-Al 0.05 Ga 0.95 N, and the material of the n-type guide layer 124 is n-GaN.

[0035] An active layer (light emitting layer) 114 having a quantum well structure is formed on the n-type semiconductor layer 120. When the oscillation wavelength is set to 444 nm, the material of the quantum well structure is In as a barrier layer. 0.01 Ga 0.99 N as the well layer, and In as the well layer. 0.15 Ga 0.85 You can choose N.

[0036] In order to suppress the diffusion of impurities from the n-type semiconductor layer 120 to the active layer 114, an undoped nitride guide layer (not shown) In is provided between them. 0.02 Ga 0.98 N can be inserted.

[0037] The p-type semiconductor layer 130 may include a carrier block (electron block EB) layer 132, a p-type guide layer 134, a p-type cladding layer 136, and a contact layer 138. For example, the material of the p-type guide layer 134 is p-In 0.02 Ga 0.98 N, and the material of the p-type cladding layer 136 is p-Al 0.04 Ga 0.96 N, and the material of the contact layer 138 is p-GaN.

[0038] In order to suppress diffusion of impurities from the p-type semiconductor layer 130 to the active layer 114, an undoped nitride guide layer (not shown) can be inserted between them.

[0039] An n-side electrode 140 is formed on the back surface of the GaN substrate 112 , and a p-side electrode 142 is formed on the top surface of the contact layer 138 .

[0040] A ridge (mesa) is formed in the p-type cladding layer 136 to form a ridge stripe structure (ridge structure) 160. The height of the ridge can be several hundred nm, and the width of the ridge (mesa width) can be several microns. For example, the height can be 500 nm and the width can be 2 μm.

[0041] The optical coupling coefficient κ, which will be described later, also varies depending on the ridge width, and the narrower the mesa width, the larger the optical coupling coefficient κ. However, when the mesa width is less than 1 μm, the lateral confinement weakens and the optical coupling coefficient begins to decrease. On the other hand, when the mesa width exceeds 3 μm, the transverse single mode changes to transverse multimode. Therefore, in order to obtain a high optical coupling coefficient κ in the transverse single mode, it is preferable that the mesa width Wm is 1 μm≦Wm≦3 μm.

[0042] The p-type cladding layer 136 having a ridge stripe structure 160, together with the active layer 114 and the n-type cladding layer 122, forms a ridge-type waveguide.

[0043] A diffraction grating 150 is formed on the p-type cladding layer 136 on the side of the mesa adjacent to the ridge stripe structure 160 .

[0044] The emission side (front) end face of the semiconductor laser element 100 is coated with an AR (anti-reflection) coating (reflectance 2% or less), and the reflection side (rear) end face is coated with an HR (high reflection) coating (reflectance 90% or more). Alternatively, both end faces may be AR coated.

[0045] Fig. 2 is a diagram illustrating the interaction between light and diffraction grating 150. Fig. 2 shows a simplified cross-sectional view of semiconductor laser device 100. Laser light guided in the ridge-type waveguide seeps out in the horizontal direction, and the seeped out portion interacts with diffraction grating 150 located on the side of ridge stripe structure 160. This allows the device to function as a distributed feedback laser, enabling oscillation in a single longitudinal mode.

[0046] The shape of the grooves of the diffraction grating 150 is generally considered to be rectangular, but is not limited thereto as long as a similar effect is effectively obtained. For example, the cross-sectional shape of the grooves may be trapezoidal, wedge-shaped, or other shapes. When the cross-section of the grooves is non-rectangular, the width may be defined as the average width.

[0047] Next, a diffraction grating 150 for obtaining a high output at 444 nm will be described. In a semiconductor laser of a long wavelength (red to infrared region), the optical coupling coefficient κ of the diffraction grating can be easily increased, but in a blue laser, it is difficult to increase the optical coupling coefficient κ, and the structure of the diffraction grating 150 greatly affects the performance of the semiconductor laser element 100.

[0048] Fig. 3 is a diagram showing the relationship between the duty ratio of a diffraction grating and the optical coupling coefficient κ. Fig. 3 shows the calculation of the optical coupling coefficient κ for the first, third, fifth, and seventh order diffracted light. The groove depths are 50 nm, 100 nm, 150 nm, and 200 nm, respectively. The duty ratio of a diffraction grating is expressed as the ratio of the groove width and period of the diffraction grating, and if the groove width is w and the period is p, then duty = 1-(w / p), and is defined in the range of 0≦duty≦1. The narrower the groove width w, the higher the duty ratio.

[0049] One of the important parameters in designing a DFB-LD is the normalized coupling coefficient κL. Here, κ is the optical coupling coefficient and L is the cavity length. Empirically, it is recommended that κL should be κL ≥ 0.5, and more preferably κL ≥ 1. This is because in a DFB-LD with a small κL, the FP (Fabry-Perot) mode and the DFB mode may coexist depending on the driving conditions, making it impossible to realize longitudinal single mode oscillation with a high SMSR (side mode suppression ratio). In addition, in a transverse single mode nitride semiconductor laser, the ridge width is about 2 μm, so in order to obtain an optical output of several tens of mW or more, it is empirically recommended that the cavity length be 500 μm or more. This is because, in general, the optical output becomes thermally saturated due to heat generation caused by current flow, and if the cavity length is short, thermal saturation occurs before sufficient optical output is obtained. For these reasons, it is recommended that the optical coupling coefficient κ of a DFB-LD be κ ≥ 10 cm. -1 It is desirable to design it so that

[0050] Figure 4 shows the optical coupling coefficient κ obtained from the results of Figure 3, with a value of 10 cm -1 FIG. 4 is a diagram showing the range of the groove depth d and the duty ratio duty when the above condition is satisfied. d=a×(duty-b) n +c …(2) This can be nicely expressed by equation (2).

[0051] a, b, c, and n are fitting parameters. For a certain depth d, the optical coupling coefficient κ can be set to 10 cm by determining the duty ratio within the range enclosed by equation (2). -1 In other words, the duty ratio “duty” can be determined so as to satisfy the following relational expression (1).

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[0052] Here, the optical coupling coefficient κ depends on the groove depth d, and the deeper the groove is dug, the more the optical coupling coefficient tends to increase monotonically. However, due to restrictions on etching technology, the groove cannot be made infinitely deep, and the maximum depth is about 200 nm. In addition, if the depth of the diffraction grating d is made deeper than 200 nm, the height of the ridge stripe structure 160 (mesa height) needs to be increased to ensure sufficient lateral light confinement, but this leads to an increase in the driving voltage. Considering such restrictions, the groove depth d is preferably in the range of 50 to 200 nm.

[0053] In one embodiment, the diffraction order may be 3. In this case, a=1000000, b=0.889, c=75.3, n=4 and the possible groove depths d are 75.3 nm≦d≦200 nm.

[0054] In one embodiment, the diffraction order can be 1. In this case, a=7500000, b=0.738, c=54.9, n=8, and the possible groove depths d are 54.9 nm≦d≦200 nm.

[0055] In one embodiment, the diffraction order may be 5. In this case, a=7500000, b=0.929, c=88.9, n=4 and the possible groove depths d are 88.9 nm≦d≦200 nm.

[0056] In one embodiment, the diffraction order may be 7. In this case, a=23000000, b=0.947, c=100.6, n=4 and possible groove depths d are 100.6 nm≦d≦200 nm.

[0057] (Embodiment 2) Fig. 5 is a perspective view of a semiconductor laser device 100A according to embodiment 2. The semiconductor laser device 100A further includes a second diffraction grating 152 in addition to the components of the semiconductor laser device 100 in Fig. 1. In embodiment 2, the diffraction grating 150 adjacent to the ridge stripe structure 160 is referred to as a first diffraction grating 150.

[0058] The second diffraction grating 152 has the same periodic structure as the first diffraction grating 150, and when the semiconductor laser device 100A is viewed in a plan view, the corresponding grooves of the first diffraction grating 150 and the second diffraction grating 152 are aligned and continuous.

[0059] 6 is a diagram illustrating the interactions between light and the first and second diffraction gratings 150 and 152. FIG. 6 shows a simplified cross-sectional view of the semiconductor laser device 100A. The laser light guided through the ridge-type waveguide seeps out in the horizontal lateral direction, and the seeped out portion interacts with the first diffraction grating 150 located to the side of the ridge stripe structure 160. In addition, the laser light also seeps out in the vertical upward direction, and the seeped out portion interacts with the second diffraction grating 152 located above the ridge stripe structure 160. This makes it possible to further increase the optical coupling coefficient κ compared to the first embodiment.

[0060] 7 is a diagram showing the optical coupling coefficient κ of the first and second embodiments. Calculations were performed for third-order diffracted light and first-order diffracted light. For third-order diffracted light, the groove depth d=150 nm and the duty ratio were set to 90%, and for first-order diffracted light, the groove depth d=100 nm and the duty ratio were set to 85%. In the second embodiment, the optical coupling coefficient κ can be increased for both first-order and third-order diffracted light.

[0061] Furthermore, in the semiconductor laser device 100A according to the second embodiment, the first and second diffraction gratings have the same periodic structure, and therefore can be formed simultaneously using the same manufacturing process. In this case, the groove depths of the diffraction gratings 150 and 152 are approximately the same. In other words, the bottom of the grooves of the diffraction grating 150 is located higher than the bottom of the grooves of the diffraction grating 152.

[0062] If the depth of the diffraction grating d is made deeper than 200 nm, the height of the ridge stripe structure 160 (the height of the mesa) must be increased to ensure sufficient lateral light confinement, but this leads to an increase in the drive voltage. In addition, the injected current is also likely to be non-uniform in the cavity direction. By limiting the depth d of the diffraction grating grooves to the range of 50 to 200 nm, there is no need to increase the height of the mesa, and the problems of voltage increase and non-uniform current do not occur.

[0063] 8 is a diagram illustrating a manufacturing method of the semiconductor laser device 100A. In step S1, an insulating film 202 is formed on a laminated structure 201 in which a mesa is formed. The laminated structure 201 is a laminated structure including the GaN substrate 112, the n-type semiconductor layer 120, the active layer 114, and the p-type semiconductor layer 130 of FIG. The laminated structure may be manufactured using a known technique.

[0064] In the next step S2, a resist 204 is applied onto the insulating film 202, and then the patterns of the diffraction gratings 150 and 152 are formed.

[0065] In the next step S3, the insulating film 202 is etched and the resist 204 is removed. In the next step S4, the insulating film 202 is removed.

[0066] An insulating film 206 may be formed inside the groove. The insulating film 206 is preferably formed at least in the portion from which light seeps out, and may completely fill the groove. In step S5, the insulating film 206 is formed by ADL (atomic layer deposition). By using the ADL method, the insulating film 206 can be successfully formed on the bottom surface of the groove. The material of the insulating film 206 is an oxide containing one or more elements of Si, Zr, Al, Ta, Nb, Ti, In, O, and N, specifically, SiN x , SiO2, ZrO2, Al2O3, Ta2O5, Nb2O5, TiO2, AlN, AlON, AlInN, etc. can be used.

[0067] In the next step S6, a portion 208 of the upper surface of the mesa is removed from the insulating film 206. Then, in step S7, the p-side electrode 142 is formed.

[0068] The above is the method for manufacturing semiconductor laser device 100 A. According to this semiconductor laser device 100 A, first diffraction grating 150 and second diffraction grating 152 can be formed simultaneously in the same process.

[0069] In the semiconductor laser device 100 according to the first embodiment, it is necessary to form the diffraction grating 150 while avoiding the mesa, which makes the manufacturing process difficult. In other words, if the diffraction grating 150 is brought very close to the shoulder of the mesa, there is a high possibility that a groove will be formed on the side of the mesa. Conversely, if one tries to prevent the groove on the side of the mesa, the diffraction grating 150 will be separated from the shoulder of the mesa, which will reduce the optical coupling coefficient κ. In the second embodiment, the first diffraction grating 150 and the second diffraction grating 152 are formed simultaneously in the same process, so this problem does not occur.

[0070] (Embodiment 3) 9 is a perspective view of a semiconductor laser device 100B according to embodiment 3. The second diffraction grating 152 is formed on the top surface of the mesa, but no groove is formed within a certain width from the side surface of the mesa. This can further suppress non-uniformity of current injection.

[0071] In the first to third embodiments, the diffraction gratings 150 and 152 may be provided with a phase shift region. Fig. 10 is a cross-sectional view showing a diffraction grating 150C having a phase shift region 151. For comparison, the lower part of Fig. 10 shows a diffraction grating 150 without a phase shift region 151. The phase shift region 151 is provided in the mountain portion of the diffraction grating 150C. The length of the phase shift region 151 is λ / 4n 0r ×(2m+1) where λ is the oscillation wavelength, m is 0 or any positive integer, and n 0r is the average refractive index experienced by light. n 0r is a value that depends on the structure and materials of the semiconductor laser element, and 1 <n 0rThe value can be in the range of <3. By providing the phase shift region 151, the side mode suppression ratio (SMSR) of the single longitudinal mode can be improved.

[0072] The phase shift region 151 is preferably formed closer to the high reflection end face than to the center of the cavity. For example, the phase shift region 151 may be provided at a position that divides the distance between the low reflection end face (emission end face) and the high reflection end face of the semiconductor laser element in a ratio of 6:4 to 8:2.

[0073] Next, applications of the semiconductor laser device 100 will be described.

[0074] 11 is a diagram showing a light emitting device 200 according to an embodiment. The light emitting device 200 includes the above-mentioned semiconductor laser device 100 (100A, 100B), a nonlinear optical element 210, and a filter 220.

[0075] The semiconductor laser element 100 oscillates in a single longitudinal mode with λ=444 nm. The nonlinear optical element 210 is a wavelength conversion element, which generates a second harmonic λ / 2 (wavelength 222 nm) of the light emitted from the semiconductor laser element 100. The nonlinear optical element 210 may be, for example, β-BaB2O4 (BBO) or CsLiB6O 10 (CLBO) or the like is used. By irradiating the fundamental wave (444 nm) from an appropriate direction to this wavelength conversion element, the second harmonic (222 nm) can be generated. The filter 220 is a short-pass filter that removes the fundamental wave λ and outputs the second harmonic λ / 2.

[0076] The embodiments merely illustrate the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments without departing from the spirit of the present invention defined in the claims. [Explanation of symbols]

[0077] 100 Semiconductor laser element 110 Laminated structure 112 GaN substrate 120 n-type semiconductor layer 122 n-type cladding layer 124 n-type guide layer 114 Active layer 130 p-type semiconductor layer 132 Carrier Block Layer 134 p-type guide layer 136 p-type cladding layer 138 Contact Layer 140 n-side electrode 142 p side electrode 150 First diffraction grating 151 Phase Shift Region 152 Second diffraction grating 160 Ridge stripe structure 200 Light emitting device 210 Nonlinear Optical Elements 220 Filter

Claims

1. A distributed feedback semiconductor laser element, a laminated structure including a GaN substrate, a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer, and in which a ridge type waveguide is formed; a first diffraction grating formed adjacent to the ridge-type waveguide on both sides; Equipped with The depth d of the grooves of the first diffraction grating is within the range of 50 nm≦d≦200 nm, and the duty ratio duty is expressed by the inequality (1) using constants a, b, c, and n defined for the order of diffracted light. [0010] A semiconductor laser element characterized in that:

2. 2. The semiconductor laser device according to claim 1, wherein the order is 3, a=1,000,000, b=0.889, c=75.3, n=4, and 75.3 nm≦d≦200 nm.

3. 2. The semiconductor laser device according to claim 1, wherein the order is 1, a=7,500,000, b=0.738, c=54.9, n=8, and 54.9 nm≦d≦200 nm.

4. 2. The semiconductor laser device according to claim 1, wherein the order is 5, a=7,500,000, b=0.929, c=88.9, n=4, and 88.9 nm≦d≦200 nm.

5. 2. The semiconductor laser device according to claim 1, wherein the order is 7, a=23000000, b=0.947, c=100.6, n=4, and 100.6 nm≦d≦200 nm.

6. 6. The semiconductor laser device according to claim 1, further comprising a second diffraction grating formed on an upper surface of the ridge-type waveguide.

7. 7. The semiconductor laser device according to claim 6, wherein a bottom surface of the grooves of the second diffraction grating is higher than a bottom surface of the grooves of the first diffraction grating.

8. 6. The semiconductor laser device according to claim 1, wherein the first diffraction grating has a phase shift region.

9. 9. The semiconductor laser element according to claim 8, wherein the phase shift region is provided at a position that divides a space between a low reflection end face and a high reflection end face of the semiconductor laser element in a ratio of 6:4 to 8:

2.

10. A semiconductor laser element as described in any one of claims 1 to 5, characterized in that at least in the portion of the first diffraction grating from which light leaks out, the groove portion is covered with an insulating film, and the insulating film contains at least one element selected from the group consisting of Si, Zr, Al, Ta, Nb, Ti, In, O, and N.

11. A distributed feedback semiconductor laser element according to any one of claims 1 to 5, a nonlinear optical element for generating a second harmonic of the emitted light of the distributed feedback semiconductor laser element; a filter that transmits the second harmonic; A light emitting device comprising:

12. A method for manufacturing a distributed feedback semiconductor laser device, comprising the steps of: forming a laminated structure including a GaN substrate, a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer; forming a ridge stripe structure in the laminate structure; forming a first diffraction grating adjacent to the ridge stripe structure; forming an insulating film inside the grooves of the first diffraction grating; Equipped with The depth d of the grooves of the first diffraction grating is within the range of 54.9 nm≦d≦200 nm, and the duty ratio duty is expressed by the inequality (1) using constants a, b, c, and n defined for the order of diffracted light. [0025] A manufacturing method characterized in that the range is within the range.

13. The method according to claim 12 , further comprising the step of forming a second diffraction grating in a region adjacent to the ridge stripe structure at the same time as forming the first diffraction grating.

14. 14. The method according to claim 12, wherein the insulating film is formed by an atomic layer deposition (ALD) method.

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