Quantum cascade laser, semiconductor laser device, method for manufacturing the same, and gas analysis device

Abstract

A semiconductor laser element, a semiconductor laser device, a manufacturing method thereof, and a gas analysis device. A distributed feedback semiconductor laser element (3) has a diffraction grating (3M) formed on a waveguide path (3L), stably outputs light of a single mode, and increases the intensity of the light. The waveguide path (3L) includes a diffraction grating portion (301) in which the diffraction grating (3M) is formed, and a flat portion (302) having a region in which the diffraction grating (301) is not formed and which is wider than the diffraction grating portion (301). The flat portion (302) has a connecting portion (303) having a region in which the width continuously changes toward a connecting position with the diffraction grating portion (301). A high reflection film (HR) is provided on an end surface of the flat portion (302) on the opposite side from the connecting portion (303), and a low reflection film (AR) is provided on an end surface of the diffraction grating portion (301) on the opposite side from the connecting portion (303).

Description

Technical Field

[0001] This invention relates to semiconductor laser elements, semiconductor laser devices, methods for manufacturing semiconductor laser devices, and gas analysis devices. Background Technology

[0002] Previously, one of the gas analysis methods that uses quantum cascade lasers (QCLs) that oscillate lasers in the mid-infrared region was the mid-infrared laser absorption method (QCL-IR).

[0003] The QCL-IR gas analysis device irradiates a sample containing the target component with laser light from a quantum cascade laser. A photodetector detects the intensity of the laser light transmitted through the sample, and the detected signal is used to analyze the target component. Here, the quantum cascade laser needs to have its oscillation wavelength controlled to a wavelength suitable for the target component and to efficiently extract a single beam of light at the desired oscillation wavelength, for example, using the quantum cascade laser shown in Patent Document 1.

[0004] In order to extract a single beam of light at the desired oscillation wavelength, a periodic diffraction grating corresponding to the oscillation wavelength is formed in the waveguide of this quantum cascade laser. Furthermore, in the quantum cascade laser, to improve the single-mode nature of the laser, it is preferable to reduce the width of the waveguide; and to increase the laser output (gain), it is preferable to increase both the width and the long side of the waveguide.

[0005] However, if the waveguide width is reduced (to less than twice the oscillation wavelength) to improve the single-mode nature of the laser, the laser output (gain) will decrease. On the other hand, if the waveguide width or long side dimension is increased to increase the laser intensity, the single-mode nature of the laser will decrease. In other words, there is a trade-off between the single-mode nature of the laser and the optical output (gain) when it comes to the waveguide width.

[0006] Furthermore, increasing the width or long side of the waveguide to increase laser intensity leads to increased power consumption for laser oscillation. This, in turn, causes a rise in the temperature of the semiconductor laser element, increases the chirp rate of the laser oscillation wavelength, and degrades the resolution in gas analysis.

[0007] Patent Document 1: Japanese Patent Application Publication No. 8-107253 Summary of the Invention

[0008] In view of the above problems, the inventors of this application have studied the following: Figure 9As shown, in a waveguide circuit with a diffraction grating, by setting a diffraction grating portion with a diffraction grating and a flat portion without a diffraction grating, the width of the diffraction grating portion is reduced to improve single-mode performance, and the width of the flat portion is increased to increase the laser output (gain).

[0009] However, it was determined that under the above structure, unintentional reflection occurred at the corner formed between the diffraction grating and the flat part, which hindered the single-mode capability.

[0010] Therefore, the present invention was made to solve the above-mentioned problems. The main objective of the present invention is to stably output single-mode light and increase the light output (gain) in a semiconductor laser element.

[0011] That is, the semiconductor laser element of the present invention has a diffraction grating formed on a waveguide path, wherein the waveguide path includes: a diffraction grating portion having the diffraction grating formed thereon; and a flat portion having a region where the diffraction grating is not formed and the width is wider than that of the diffraction grating portion, the flat portion having a connecting portion having a region whose width continuously changes as it moves toward the connecting portion of the diffraction grating portion, a high-reflectivity film being provided on the end face of the flat portion opposite to the connecting portion, and a low-reflectivity film being provided on the end face of the diffraction grating portion opposite to the connecting portion.

[0012] In a semiconductor laser element with such a design, the narrow diffraction grating portion and the wide flat portion enhance single-mode performance and increase laser output (gain). Furthermore, because the flat portion has a connection portion whose width continuously varies with its orientation towards the connection point with the diffraction grating portion, unintentional reflections are reduced, enabling stable single-mode light output. Additionally, since a high-reflectivity film is provided on the end face of the flat portion opposite to the connection portion, and a low-reflectivity film is provided on the end face of the diffraction grating portion opposite to the connection portion, single-mode light can be stably output from the end face of the diffraction grating portion. Thus, the end face of the diffraction grating portion opposite to the connection portion becomes the light exit surface, further improving single-mode performance.

[0013] As a specific implementation, it can be considered that the width of the connecting portion continuously narrows as it moves toward the connection point with the diffraction grating portion.

[0014] Alternatively, it can be considered that the maximum width of the connecting portion is less than or equal to the maximum width of the portion of the flat portion other than the connecting portion, and the minimum width of the connecting portion is greater than or equal to the maximum width of the diffraction grating portion.

[0015] Preferably, the flat portion has the connecting portion and a rectangular portion.

[0016] Specifically, in order to reduce unintentional reflections between the diffraction grating portion and the connecting portion or between the rectangular portion and the connecting portion, it is preferable that the connection portion between the diffraction grating portion and the connecting portion and / or the connection portion between the rectangular portion and the connecting portion are rounded.

[0017] As a specific embodiment of the connecting portion, the following method can be adopted. That is, the connecting portion has: a tapered portion whose width continuously narrows as it moves toward the connection portion with the diffraction grating portion; and a narrow portion that connects the tapered portion to the diffraction grating portion.

[0018] In order to suppress transverse mode oscillations and emit single-mode light, it is preferable that the width of the light emitting end of the waveguide is 1 to 2 times the oscillation wavelength.

[0019] In order to reasonably balance the stabilization of single-mode light and the increase of light output (gain), it is preferable that the area of ​​the region where the diffraction grating is not formed is greater than or equal to the area of ​​the region where the diffraction grating is formed.

[0020] Preferably, it includes: a first electrode for supplying current to the diffraction grating portion; and a second electrode, disposed independently of the first electrode, for supplying current to the flat portion.

[0021] With this structure, the current flowing to the diffraction grating and the current flowing to the flat section can be controlled independently. As a result, the current flowing to the diffraction grating can be reduced, and the chirp rate, which is the proportion of the change in oscillation wavelength, can be reduced when the current flows in a pulsed manner, thereby improving the resolution when used in a gas analysis device.

[0022] When a diffraction grating is formed in the connecting portion, the width of the region where the diffraction grating is formed varies, so the instability of single-mode light can be taken into account. Therefore, it is preferable that the connecting portion is a region where the diffraction grating is not formed. With this structure, single-mode performance can be further improved.

[0023] Furthermore, the semiconductor laser device manufacturing method of the present invention is a method for manufacturing a semiconductor laser device in which a diffraction grating is formed on a waveguide path, comprising: a structure forming step, wherein a stacked structure is formed on a substrate, the stacked structure having a diffraction grating region in which the diffraction grating is formed and a flat region in which the diffraction grating is not formed; and a waveguide path forming step, wherein the stacked structure is etched to form a waveguide path, the waveguide path comprising: a diffraction grating portion in which the diffraction grating is formed; and a flat portion having a region in which the diffraction grating is not formed and the width is wider than that of the diffraction grating portion, the flat portion having a connecting portion having a region in which the width continuously varies with the direction of the connection portion to the diffraction grating portion.

[0024] Furthermore, the semiconductor laser device of the present invention includes a substrate and a semiconductor laser element disposed on the substrate. The semiconductor laser element is a distributed feedback semiconductor laser element on a waveguide with a diffraction grating formed thereon. The waveguide includes: a diffraction grating portion on which the diffraction grating is formed; and a flat portion having a region on which the diffraction grating is not formed and whose width is wider than that of the diffraction grating portion. The flat portion has a connecting portion having a region whose width continuously changes as it moves toward the connecting portion with the diffraction grating portion.

[0025] Furthermore, the gas analysis apparatus analyzes the components of the gas to be measured, and includes: a measuring cell for introducing the gas; the aforementioned semiconductor laser device for irradiating the measuring cell with laser light; a photodetector for detecting the laser light that has passed through the measuring cell; and an analysis unit for analyzing the components of the gas to be measured using the detection signal from the photodetector.

[0026] According to the present invention configured in this way, single-mode light can be stably output in a semiconductor laser element and the light output (gain) can be increased. Attached Figure Description

[0027] Figure 1 This is an overall schematic diagram of the exhaust gas analysis device using the semiconductor laser device of this embodiment.

[0028] Figure 2 This is an overall schematic diagram of a semiconductor laser device with the same implementation method.

[0029] Figure 3 This is a cross-sectional view of a semiconductor laser element of the same embodiment, orthogonal to the waveguide direction.

[0030] Figure 4 This is a cross-sectional view of a semiconductor laser element according to the same embodiment, shown along line AA.

[0031] Figure 5 This is a top view showing the waveguide path of a semiconductor laser element according to the same embodiment.

[0032] Figure 6 This is a schematic diagram illustrating a method for manufacturing a semiconductor laser device according to the same embodiment.

[0033] Figure 7 This is a top view showing the waveguide path of a semiconductor laser element in a modified embodiment.

[0034] Figure 8 This is a top view showing the waveguide path of a semiconductor laser element in a modified embodiment.

[0035] Figure 9This is a top view showing the waveguide path of a semiconductor laser element, which is a comparative example of the present invention. Detailed Implementation

[0036] An embodiment of the semiconductor laser device of the present invention will be described below with reference to the accompanying drawings.

[0037] <1. Device Structure>

[0038] like Figure 1 As shown, the semiconductor laser device 100 of this embodiment is used in a gas analysis device 10, which, for example, analyzes the target component in exhaust gas discharged from an internal combustion engine. Here, the gas analysis device 10 includes: a multi-reflection measuring cell 11 for introducing exhaust gas; a semiconductor laser device 100 for irradiating the measuring cell 11 with laser light; a photodetector 12 for detecting the laser light passing through the measuring cell 11; and an analysis unit 13 for analyzing the target component using the detection signal from the photodetector 12.

[0039] Specifically, the semiconductor laser device 100 emits a wavelength ±1 cm relative to the absorption wavelength of the component being measured. -1 Lasers with oscillation wavelengths, such as Figure 2 and Figure 3 As shown, it includes a semiconductor substrate 2 such as an InP substrate and a semiconductor laser element 3 formed on the semiconductor substrate 2.

[0040] Furthermore, the semiconductor substrate 2, on which the semiconductor laser element 3 is disposed, is housed within an hermetically sealed container 5, such as a butterfly package. Within this hermetically sealed container 5, a light-guiding section 51 for guiding laser light outwards is formed at a location opposite the light-emitting surface 3x of the semiconductor laser element 3. An optical window component 6 is provided in this light-guiding section 51, and this optical window component 6 is slightly tilted (e.g., 2 degrees) so that laser light reflected by the optical window component 6 does not return to the semiconductor laser element 3. Additionally, a cooling module 7 or similar device for cooling the semiconductor laser element 3 is also housed within the hermetically sealed container 5.

[0041] like Figure 3 and Figure 4 As shown, the semiconductor laser element 3 is a distributed feedback (DFB) semiconductor laser element, which has a waveguide 3L. The waveguide 3L is composed of a clad layer and a core layer disposed on the semiconductor substrate 2. In this waveguide 3L, light passes through the core layer by utilizing the difference in refractive index between the clad layer and the core layer.

[0042] Specifically, the semiconductor laser element 3 has a buffer layer 31, a core layer 32, an upper cladding layer 33, and a cap layer 34 sequentially formed on the upper surface of the semiconductor substrate 2. Furthermore, these layers 31 to 34 all extend in the same direction. Additionally, the sides of these layers in their width direction are covered by a protective film 35, thereby forming a waveguide path 3L extending in one direction. Furthermore, the protective film 35 is an inorganic film, such as SiO2 or a combination of SiO2 and Si3N4.

[0043] Both the buffer layer 31 and the upper covering layer 33 are made of InP. Alternatively, a lower covering layer made of InP can be provided between the buffer layer 31 and the core layer 32, allowing the buffer layer 31 to function as a covering layer.

[0044] The capping layer 34 is a layer made of InGaAs, and a portion of its upper surface (the central part in the width direction) is covered by the upper electrode 91.

[0045] The core layer 32 has: a lower guiding layer 321 made of InGaAs; an active layer 322 that emits light when injected with current; and an upper guiding layer 323 made of InGaAs.

[0046] The active layer 322 is composed of a multi-quantum-well structure with multiple well layers, formed by alternating layers of semiconductor layers that will become light-emitting regions and semiconductor layers that will become injection regions in a predetermined number. Furthermore, the semiconductor layers that will become light-emitting regions are formed by alternating layers of InGaAs and InAlAs, and the semiconductor layers that will become injection regions are formed by alternating layers of InGaAs and InAlAs.

[0047] like Figure 6 As shown, the semiconductor laser element 3 thus constructed is a quantum cascade laser that emits light by means of optical transitions between subbands formed in these quantum wells, where multiple well layers are connected in a multi-level manner.

[0048] In this semiconductor laser element 3, a diffraction grating 3M is formed between the core layer 32 and the upper cladding layer 33, i.e., on the upper guiding layer 323 (see reference). Figure 4 The diffraction grating 3M is composed of alternating recesses and convexities formed on the upper guide layer 323, with the recesses and convexities extending in the width direction of the upper guide layer 323. Using this diffraction grating 3M, light of a predetermined oscillation wavelength mutually reinforces each other and is selectively amplified. Furthermore, the predetermined oscillation wavelength is defined by the pitch of the diffraction grating 3M.

[0049] On the lower surface of the semiconductor substrate 2, a lower electrode 92 is provided in the portion located below the semiconductor laser element 3. Furthermore, by applying a laser oscillation current (or voltage) to the upper electrode 91 and the lower electrode 92, a predetermined oscillation wavelength defined by the diffraction grating 3M is emitted. A current source (or voltage source) is connected to the upper electrode 91 and the lower electrode 92 for laser oscillation, and the laser control device 8 controls this current source (or voltage source) (see reference). Figure 2 ).

[0050] <2. Characteristic Structure of Semiconductor Laser Element 3>

[0051] Furthermore, in the semiconductor laser element 3 of this embodiment, such as Figure 4 and Figure 5 As shown, the waveguide 3L has: a diffraction grating portion 301 on which a diffraction grating 3M is formed; and a flat portion 302 on which a diffraction grating 3M is not formed.

[0052] The diffraction grating portion 301, used to obtain the predetermined oscillation wavelength, extends in a straight line along its long side when viewed from above, and has a substantially uniform width in the width direction orthogonal to the long side direction. As described above, the diffraction grating 3M formed in the diffraction grating portion 301 is composed of alternating recesses and convex portions formed between the core layer 32 and the upper cladding layer 33, i.e., alternatingly formed in the upper guide layer 323. Furthermore, the width dimension of the diffraction grating portion 301 is configured to be 1 to 2 times the predetermined oscillation wavelength. Using this structure, the width dimension of the light emitting end of the waveguide 3L is 1 to 2 times the oscillation wavelength, which can suppress transverse mode oscillations and efficiently emit single-mode light.

[0053] The flat portion 302, used to increase light output (gain), is a region where the diffraction grating 3M is not formed and is wider than the diffraction grating portion 301. In this embodiment, the flat portion 302 has: a rectangular portion 302s that is substantially rectangular when viewed from above; and a connecting portion 303 whose width continuously changes as it approaches the connection portion CP1 with the diffraction grating portion 301. This flat portion 302 is formed between the core layer 32 and the upper cladding layer 33 without forming recesses or protrusions in the upper guide layer 323.

[0054] Furthermore, the flat portion 302 has a connecting portion 303 whose width continuously changes as it approaches the connection point with the diffraction grating portion 301. This connecting portion 303 has a portion whose width gradually increases from the diffraction grating portion 301 towards the rectangular portion 302s. In this embodiment, the connecting portion 303 is configured such that its width gradually increases from the diffraction grating portion 301 towards the rectangular portion 302s. That is, the connecting portion 303 is tapered from the rectangular portion 302s towards the diffraction grating portion 301. In other words, the connecting portion 303 is configured such that its width continuously decreases as it approaches the connection point with the diffraction grating portion 301. Additionally, the width dimension of the connecting portion 303 on the diffraction grating portion 301 side is the same as the width dimension of the diffraction grating portion 301, and the edges 303a on both ends of the connecting portion 303 in the width direction are continuous with the edges on both sides of the rectangular portion 302s in the width direction. On the other hand, the width dimension of the rectangular portion 302s side of the connecting portion 303 is the same as the width dimension of the rectangular portion 302s, and the edges 303a on both ends of the connecting portion 303 in the width direction are continuous with the edges on both ends of the diffraction grating portion 301 in the width direction. With this structure, the maximum width of the connecting portion 303 is less than or equal to the maximum width of the portion other than the connecting portion 303 of the flat portion 302, and the minimum width of the connecting portion 303 is greater than or equal to the maximum width of the diffraction grating portion 301. Furthermore, the edges 303a on both ends of the connecting portion 303 in the width direction are straight. Additionally, in this embodiment, the connecting portion 303 is a region where the diffraction grating 3M is not formed.

[0055] In this embodiment, the connection portion CP1 between the diffraction grating portion 301 and the connecting portion 303, and / or the connection portion CP2 between the rectangular portion 302s and the connecting portion 303, may also be rounded. Specifically, when viewed from above, the sides of the diffraction grating portion 301 in the width direction are connected to the sides of the connecting portion 303a in the width direction in an arc shape, and the sides of the rectangular portion 302s in the width direction are connected to the sides of the connecting portion 303a in the width direction in an arc shape. That is, there are no sharp corners between the diffraction grating portion 301 and the rectangular portion 302s. As a result, unintentional reflections between the diffraction grating portion 301 and the connecting portion 303, or between the rectangular portion 302s and the connecting portion 303, can be reduced.

[0056] In this embodiment, the waveguide 3L of the semiconductor laser element 3 may also be configured such that the area of ​​the region where the diffraction grating 3M is not formed is greater than or equal to the area of ​​the region where the diffraction grating 3M is formed.

[0057] In the semiconductor laser element 3 configured as described above, the end face of the diffraction grating portion 301 opposite to the connecting portion 303 becomes the light emission surface 3x. Furthermore, a high-reflectivity film HR is provided on the end face of the flat portion 302 (rectangular portion 302s) opposite to the connecting portion 303, and a low-reflectivity film AR is provided on the end face of the diffraction grating portion 301 opposite to the connecting portion 303. Here, by providing the low-reflectivity film AR on the end face of the diffraction grating portion 301 opposite to the connecting portion 303, the light emission surface 3x is formed.

[0058] In addition, such as Figure 4 As shown, the upper electrode 91 of the semiconductor laser element 3 has: a first electrode 91a for supplying current to the diffraction grating portion 301; and a second electrode 91b, disposed independently of the first electrode 91a, for supplying current to the flat portion 302. Using this structure, the current I flowing through the region where the diffraction grating 3M is not provided can be individually controlled. flat and the current I flowing through the region (DFB region) where the diffraction grating is set 3M. DFB .

[0059] <3. Manufacturing method of semiconductor laser device 100>

[0060] Next refer to Figure 6 The manufacturing method of the semiconductor laser device 100 will be described.

[0061] An InP layer that forms a buffer layer 31, an InGaAs layer that forms a lower guiding layer 321, an InGaAs layer and an InAlAs layer that form an active layer 322, and an InGaAs layer that forms an upper guiding layer 323 are stacked on the upper surface of the semiconductor substrate 2 by metal-organic chemical vapor deposition (MOVPE).

[0062] A diffraction grating region 323x and a flat region 323y are formed on the upper surface of the upper guiding layer 323 by photolithography and wet etching. The diffraction grating region 323x has a diffraction grating 3M formed thereon, while the flat region 323y does not have a diffraction grating 3M formed thereon. Furthermore, an InP layer forming an upper cladding layer 33 and an InGaAs layer forming a capping layer 34 are stacked on top of the upper guiding layer 323 by metal-organic chemical vapor deposition (MOVPE). Thus, a stacked structure is formed on the semiconductor substrate 2, which has a diffraction grating region 323x with a diffraction grating 3M formed thereon and a flat region 323y without a diffraction grating 3M formed thereon (structure formation process).

[0063] The layered structure thus formed is etched to form a waveguide path 3L. Specifically, the layered structure is etched to form the waveguide path 3L. The waveguide path 3L includes: a diffraction grating portion 301 on which a diffraction grating 3M is formed; and a flat portion 302 having a region where no diffraction grating 3M is formed and a width wider than that of the diffraction grating portion 301. The flat portion 302 has a connecting portion 303 whose width continuously varies with the direction of the connection with the diffraction grating portion 301 (waveguide path forming process).

[0064] Additionally, a protective film 35 of SiO2 is formed, for example, to cover both sides of the waveguide path 3L in the width direction. A semiconductor laser element 3 is then formed. Alternatively, it is possible to form multiple semiconductor laser elements 3 on a single semiconductor substrate 2.

[0065] Furthermore, upper electrodes 91 (91a, 91b) and lower electrodes 92 for laser oscillation are formed on the semiconductor laser element 3. Additionally, a low-reflection film AR is formed on one end face of the diffraction grating portion 301, and a high-reflection film HR is formed on one end face of the flat portion. Subsequently, a semiconductor laser chip is formed by cutting the semiconductor substrate 2 for each region containing the semiconductor laser element 3. This semiconductor laser chip is disposed within the hermetically sealed container 5 and mounted on the cooling module 7.

[0066] <4. Effects of this implementation method>

[0067] In a semiconductor laser device 100 like this, the narrow diffraction grating portion 301 and the wide flat portion 302 enhance single-mode performance and increase laser output (gain). Furthermore, since the flat portion 302 has a connecting portion 303 whose width continuously varies with its orientation towards the connection point with the diffraction grating portion 301, unintentional reflections are reduced, enabling stable single-mode light output. Additionally, a high-reflectivity film HR is provided on the end face of the flat portion 302 opposite to the connecting portion 303, and a low-reflectivity film AR is provided on the end face of the diffraction grating portion 301 opposite to the connecting portion 303, allowing stable single-mode light output from the end face of the diffraction grating portion 301. Thus, since the end face of the diffraction grating portion 301 opposite to the connecting portion 303 becomes the light exit surface, single-mode performance is further enhanced.

[0068] Furthermore, in a structure where the area of ​​the region where the diffraction grating 3M is not formed is greater than or equal to the area of ​​the region where the diffraction grating 3M is formed, a first electrode 91a for supplying current to the diffraction grating section 301 and a second electrode 91b for supplying current to the flat section 302 are provided. Therefore, even in order to obtain high light output (gain), the total current (I) can be increased. flat +I DBF Increasing the current I can also reduce the current I flowing through the region where the diffraction grating is set 3M.DBF Therefore, the temperature rise of the diffraction grating section 301 can be suppressed, the chirp rate can be reduced, and the resolution can be improved when used in the gas analysis device 10.

[0069] <5. Other Implementation Methods>

[0070] Furthermore, the present invention is not limited to the embodiments described herein.

[0071] For example, the top view shape of the semiconductor laser element 3 is not limited to the described embodiment, such as... Figure 7 As shown, the width sides of the connecting portion 303 may also be discontinuous with the width sides of the rectangular portion 302s. Specifically, the width sides of the connecting portion 303 may be continuous with the end edges 302a of the diffraction grating portion of the rectangular portion 302s. Even in this case, it is preferable that the connection portion CP1 between the diffraction grating portion 301 and the connecting portion 303 and / or the connection portion CP2 between the rectangular portion 302s and the connecting portion 303 have rounded corners.

[0072] Furthermore, the shape of the connecting portion 303 is not limited to being straight on both sides in the width direction; it can also be curved. In this case, if the connecting portion 303 is configured to have a portion that gradually widens from the diffraction grating portion 301 toward the flat portion 302, it can also have a portion that temporarily narrows from the diffraction grating portion 301 toward the flat portion 302, such as having a necked shape.

[0073] In addition, such as Figure 8 As shown, the connecting portion 303 may also be configured as follows: having a tapered portion 303m whose width continuously narrows as it faces the connecting portion CP1 of the diffraction grating portion 301, and a narrow portion 303n that connects the tapered portion 303m to the diffraction grating portion 301.

[0074] Furthermore, in the above embodiment, the upper electrode 91 is configured as two electrode structures, with the upper electrode 91 being an electrode 91a for the diffraction grating section and an electrode 91b for the flat section. However, it may also be configured as a single electrode common to both the diffraction grating section 301 and the flat section 302.

[0075] Furthermore, in the described embodiment, the diffraction grating portion 301 and the flat portion 302 are configured to have the same width. However, it is also possible for at least one of the diffraction grating portion 301 and the flat portion 302 to have a varying width along its long side. For example, the flat portion 302 may be configured to not have a rectangular portion 302s. In this case, it may also be configured to have a continuously varying width from one end to the other, for example, a cone shape.

[0076] The driving mode of the semiconductor laser element 3 can be continuous oscillation (CW), quasi-continuous oscillation (quasi-CW), or pulse oscillation.

[0077] In the described embodiment, a distributed feedback (DFB) semiconductor laser device was described, but the present invention can also be applied to a distributed reflection (DBR) semiconductor laser device.

[0078] In the described embodiment, an example of applying the semiconductor laser device 100 to the gas analysis device 10 was given, but it can also be applied to other optical analysis devices and for optical communication purposes.

[0079] In addition, the objects of analysis are not limited to exhaust gas. For example, they can also be gases generated in semiconductor manufacturing processes, gases from byproducts in material production plants, exhaled breath, gases generated from batteries, atmospheric gases, and various other gases, as well as liquids.

[0080] Furthermore, the present invention is not limited to the described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0081] Explanation of reference numerals in the attached figures

[0082] 10 Gas Analysis Apparatus

[0083] 11 Measurement Pool

[0084] 12 Photodetectors

[0085] 13. Analysis Department

[0086] 100 Semiconductor Laser Device

[0087] 3L waveguide

[0088] 3M diffraction grating

[0089] 2 Semiconductor substrate

[0090] 3 Semiconductor laser components

[0091] 301 Diffraction Grating Section

[0092] 302 Flat section

[0093] 302s Rectangular section

[0094] 303 Connecting Part

[0095] 303m conical section

[0096] 303n narrow width section

[0097] Connection between CP1 diffraction grating section and connecting section

[0098] CP2 Connection between the flat part and the connecting part

[0099] 3x light emission surface

[0100] HR high reflectivity film

[0101] AR low-reflection film

[0102] 91a First Electrode

[0103] 91b Second electrode.

[0104] Industrial applicability

[0105] According to the present invention, a semiconductor laser element that stably outputs single-mode light and increases the intensity of the light can be provided.

Claims

1. A quantum cascade laser, wherein a diffraction grating is formed on a waveguide, characterized in that, The waveguide path includes: The diffraction grating portion is formed thereon; and The flat portion has a region where the diffraction grating is not formed and its width is wider than that of the diffraction grating portion. The flat portion has a connecting portion, the connecting portion having a region whose width continuously changes as it faces the connecting portion with the diffraction grating portion. A high-reflectivity film is provided on the end face of the flat portion opposite to the connecting portion, and a low-reflectivity film is provided on the end face of the diffraction grating portion opposite to the connecting portion. The flat portion has the connecting portion and a rectangular portion. The connection between the diffraction grating and the connecting part, and / or the connection between the rectangular part and the connecting part, are rounded.

2. The quantum cascade laser of claim 1, wherein, The width of the connecting portion continuously narrows as it moves toward the connection point with the diffraction grating portion.

3. The quantum cascade laser of claim 1, wherein, The maximum width of the connecting portion is less than or equal to the maximum width of the portion of the flat portion other than the connecting portion, and the minimum width of the connecting portion is greater than or equal to the maximum width of the diffraction grating portion.

4. The quantum cascade laser of claim 1, wherein, The connecting portion has a tapered portion whose width continuously narrows as it moves toward the connection portion with the diffraction grating portion; And a narrow width portion, connecting the tapered portion to the diffraction grating portion.

5. The quantum cascade laser according to claim 1, characterized in that, The width of the light emitting end of the waveguide is 1 to 2 times the oscillation wavelength.

6. The quantum cascade laser according to claim 1, characterized in that, The area of ​​the region where the diffraction grating is not formed is greater than or equal to the area of ​​the region where the diffraction grating is formed.

7. The quantum cascade laser according to claim 1, characterized in that, The quantum cascade laser has the following characteristics: A first electrode is used to supply current to the diffraction grating section; and The second electrode, which is disposed independently of the first electrode, is used to supply current to the flat portion.

8. A semiconductor laser device, comprising a substrate and a quantum cascade laser disposed on the substrate, characterized in that, The quantum cascade laser is the quantum cascade laser according to any one of claims 1 to 7.

9. A method for manufacturing a semiconductor laser device, the semiconductor laser device comprising a substrate and a quantum cascade laser disposed on the substrate, wherein a diffraction grating is formed in the waveguide of the quantum cascade laser. The method for manufacturing the semiconductor laser device is characterized by comprising: In the structure forming process, a stacked structure is formed on the substrate, the stacked structure having a diffraction grating region on which the diffraction grating is formed and a flat region on which the diffraction grating is not formed; as well as The waveguide formation process involves etching the stacked structure to form a waveguide, the waveguide including a diffraction grating portion on which the diffraction grating is formed. And a flat portion having a region where the diffraction grating is not formed and the width is wider than the diffraction grating portion, the flat portion having a connecting portion having a region whose width continuously changes as it faces the connection portion with the diffraction grating portion, the flat portion having the connecting portion and a rectangular portion, the connection portion between the diffraction grating portion and the connecting portion and / or the connection portion between the rectangular portion and the connecting portion having rounded corners.

10. An analytical apparatus for analyzing the analyte components contained in a sample, characterized in that, include: A measuring cell for introducing the sample; The semiconductor laser device of claim 8 irradiates the measuring cell with laser light; A photodetector detects the laser light that has passed through the measurement cell; and The analysis unit uses the detection signal from the photodetector to analyze the components of the measured object.

Images