Semiconductor lasers and laser systems including semiconductor lasers

Abstract

The present invention relates to a semiconductor laser (10) comprising a semiconductor layer device (112) having an active region (115) for generating radiation, and including a first resonator mirror (144), a second resonator mirror (146), and a resonator (131) disposed between the first resonator mirror (144) and the second resonator mirror (146), the resonator (131) extending in a direction parallel to the main surface (111) of the semiconductor layer device (112). The semiconductor laser (10) further includes a first wavelength selective absorption element (140) disposed between the semiconductor layer device (112) and the first resonator mirror (144).

Description

[0001] This patent application claims priority to German patent application DE 10 2020 205 253.0, the disclosure of which is incorporated herein by reference.

[0002] LIDAR (“Optical Detection and Ranging”) systems are increasingly being used in vehicles, for example, for autonomous driving. They are used, for instance, to measure distances or identify targets. In the case of LIDAR systems, a narrow window of wavelength is often very convenient because, in this case, sunlight can be effectively suppressed as a interference signal by using narrow-band filters. Since the emission wavelength in conventional edge-emitting semiconductor lasers varies by more than 0.2 nm / K, ideas are being researched to ensure that the wavelength remains almost unchanged even with temperature variations, i.e., to ensure increased temperature stability in this case.

[0003] This invention solves the problem of providing improved semiconductor lasers and improved LIDAR systems.

[0004] According to the embodiments, this problem is solved by the subject matter of the independent claims. Advantageous further developments are defined in the dependent patent claims.

[0005] The semiconductor laser includes: a semiconductor layer device having an active region for generating radiation, a first resonator mirror, a second resonator mirror, and a resonator disposed between the first and second resonator mirrors, the resonator extending in a direction parallel to the main surface of the semiconductor layer device. The semiconductor laser also includes a first wavelength-selective absorption element disposed between the semiconductor layer device and the first resonator mirror.

[0006] The semiconductor laser can also include a second wavelength-selective absorption element disposed between the semiconductor layer device and the second resonator mirror. For example, the first wavelength-selective absorption element can have an absorption layer disposed at a position corresponding to the location of the node of electric field strength at the target wavelength.

[0007] According to an embodiment, the first wavelength-selective absorption element may also have a transparent dielectric layer between the first resonator mirror and the absorption layer. The transparent dielectric layer is sized such that nodes of the standing wave formed at the target wavelength are disposed in the absorption layer. In this case, the planes of the transparent dielectric layer and the absorption layer can extend perpendicular to the direction of light propagation. For example, the nodes can be disposed at the center of the absorption layer.

[0008] Furthermore, the first wavelength-selective absorption element can have multiple absorption layers, wherein the optical distance between the centers of at least two adjacent absorption layers corresponds in each case to an integer multiple of half the target wavelength in a transparent dielectric layer disposed between the absorption layers.

[0009] According to an embodiment, the material of the absorber layer may contain germanium. Alternatively, the absorber layer may be implemented as a tunnel junction.

[0010] For example, transparent dielectric layers can contain SiO2, SiN, ZnSe, or transparent III-V semiconductor materials.

[0011] According to the embodiment, for a target wavelength at a predefined temperature, maximum gain can exist in the active region.

[0012] For example, a semiconductor layer device can have multiple laser elements stacked on top of each other and interconnected by at least one interconnecting layer. The laser elements can be interconnected by at least one absorbing interconnecting layer. For instance, at least one absorbing interconnecting layer can be positioned at a location corresponding to the node with the electric field strength at the target wavelength. According to an embodiment, at least one absorbing interconnecting layer can be implemented via a tunnel junction.

[0013] According to an embodiment, in the case of a semiconductor laser, the lateral boundary of the semiconductor layer device extends obliquely, such that the generated electromagnetic radiation is reflected along the direction of the first main surface of the semiconductor layer device. First and second resonator mirrors are disposed on the first main surface of the semiconductor layer device.

[0014] For example, a first wavelength selective absorption element is disposed between the first main surface and the first resonator mirror. The first wavelength selective absorption element can extend above the first main surface. The first wavelength selective absorption element can also be disposed between the first main surface and the second resonator mirror.

[0015] In the case of a semiconductor laser with oblique reflective sidewalls, wherein the semiconductor layer device has multiple laser elements and at least one absorption bonding layer, the layer thickness s2 of the at least one laser element, measured in the vertical direction, satisfies the relationship s2 = u * λ / 2. In this case, u is a natural number, and λ represents the wavelength in the semiconductor layer of the laser element.

[0016] Other embodiments relate to LIDAR systems that include semiconductor lasers as defined above.

[0017] The accompanying drawings are provided for understanding exemplary embodiments of the invention. The drawings illustrate exemplary embodiments and explain them in conjunction with the description. These contemplated further exemplary embodiments and numerous advantages will become apparent from the following detailed description. Elements and structures shown in the drawings are not necessarily shown to scale. The same reference numerals refer to the same or corresponding elements and structures.

[0018] Figure 1A Elements of an edge-emitting semiconductor laser according to an embodiment are shown.

[0019] Figure 1B A cross-sectional view of a semiconductor laser according to a further embodiment is shown.

[0020] Figure 1C A cross-sectional view of a semiconductor laser according to a further embodiment is shown.

[0021] Figure 1D A cross-sectional view showing details of a semiconductor laser according to an embodiment is shown.

[0022] Figure 2A A cross-sectional view of a surface-emitting semiconductor laser according to an embodiment is shown.

[0023] Figure 2B A cross-sectional view of a surface-emitting semiconductor laser according to a further embodiment is shown.

[0024] Figure 3A Components of a semiconductor laser according to an embodiment are shown.

[0025] Figure 3B A cross-sectional view of a semiconductor laser according to an embodiment is shown.

[0026] Figure 4A A cross-sectional view of a semiconductor laser according to a further embodiment is shown.

[0027] Figure 4B A cross-sectional view of a semiconductor laser according to a further embodiment is shown.

[0028] Figure 4C A cross-sectional view of a semiconductor laser according to a further embodiment is shown.

[0029] Figure 5 A schematic diagram of a LIDAR system according to an embodiment is shown.

[0030] In the following detailed description, reference is made to the accompanying drawings, which form part of this disclosure and illustrate specific exemplary embodiments for illustrative purposes. In this context, directional terms such as “top side,” “bottom,” “front side,” “rear side,” “above,” “up,” “in front of,” “behind,” “in front of,” “behind,” “in rear,” etc., relate to the orientation of the drawings currently described. Since components of the exemplary embodiments can be positioned in different orientations, these directional terms are used for illustrative purposes only and are not intended to be limiting.

[0031] The description of exemplary embodiments is not limiting, as other exemplary embodiments exist and structural or logical changes can be made without departing from the scope defined by the patent claims. In particular, elements of the exemplary embodiments described below can be combined with elements of the other exemplary embodiments, provided that there is no obvious contrary content in the context.

[0032] The lasers described herein are based on semiconductor materials. Generally, the terms "wafer," "semiconductor," or "semiconductor material" as used in the following description can encompass any semiconductor-based structure having a semiconductor surface. Wafers and structures should be understood to include doped and undoped semiconductors, epitaxial semiconductor layers (supported by a substrate, if appropriate), and other semiconductor structures. For example, a layer composed of a first semiconductor material can be grown on a growth substrate composed of a second semiconductor material (e.g., a GaAs substrate, a GaN substrate, or a Si substrate), or on a growth substrate composed of an insulating material (e.g., on a sapphire substrate).

[0033] Depending on the intended use, semiconductors can be based on direct or indirect semiconductor materials. Examples of semiconductor materials particularly suitable for generating electromagnetic radiation include nitride semiconductor compounds capable of producing ultraviolet, blue, or long-wavelength light, such as GaN, InGaN, AlN, AlGaN, AlGaInN, and AlGaInBN; phosphide semiconductor compounds capable of producing green or even longer-wavelength light, such as GaAsP, AlGaInP, GaP, and AlGaP; and other semiconductor materials, such as GaAs, AlGaAs, InGaAs, AlInGaAs, AlGaAsP, InGaAsP, SiC, ZnSe, ZnO, Ga2O3, diamond, hexagonal BN, and combinations thereof. The stoichiometry of compound semiconductor materials can vary. Further examples of semiconductor materials can include silicon, silicon-germanium, and germanium. In the context of this specification, the term "semiconductor" also includes organic semiconductor materials.

[0034] The term "substrate" typically includes insulating, conductive, or semiconductor substrates.

[0035] The terms “lateral” and “horizontal” as used in this specification are intended to describe an orientation or alignment that extends substantially parallel to a first surface of a substrate or semiconductor body. For example, this could be the surface of a wafer or chip (die).

[0036] The horizontal direction can be located, for example, in a plane perpendicular to the growth direction during the growth of the layer.

[0037] The term "vertical" as used in this specification is intended to describe an orientation that extends substantially perpendicular to the first surface of the substrate or semiconductor body. A vertical direction can correspond, for example, to a growth direction during the growth of a layer.

[0038] Figure 1AComponents of a semiconductor laser 10 according to an embodiment are shown. The semiconductor laser 10 includes a semiconductor layer device 112. The semiconductor layer device 112 has an active region 115 for generating radiation. The semiconductor laser 10 also has a first resonator mirror 144, a second resonator mirror 146, and a resonator 131 disposed between the first resonator mirror 114 and the second resonator mirror 146. The resonator 131 extends along a direction parallel to the main surface 111 of the semiconductor layer device 112. The semiconductor laser 10 also has a first wavelength selective absorption element 140 disposed between the semiconductor layer device 112 and the first resonator mirror 144. According to a further embodiment, the semiconductor laser 10 may also have a second wavelength selective absorption element 147 between the semiconductor layer device 112 and the second resonator mirror 146. The structure and function of the first wavelength selective absorption element 140 and the second wavelength selective absorption element 147 will be explained in more detail below.

[0039] The second resonator mirror 146 can have a reflectivity, for example, lower than that of the first resonator mirror 144. The generated laser radiation 135 can be coupled out through the second resonator mirror 146. Alternatively, the first resonator mirror 144 can have a reflectivity lower than that of the second resonator mirror 146. For example, the generated laser radiation 135 can also be coupled out through the first resonator mirror 144.

[0040] Semiconductor layer device 112 includes a first semiconductor layer 110 of a first conductivity type (e.g., p-type) and a second semiconductor layer 120 of a second conductivity type (e.g., n-type). Other semiconductor layers can be disposed between a substrate and the first semiconductor layer 110. The substrate can be insulating or may comprise a semiconductor material. The semiconductor layers can be epitaxially grown, for example, on substrate 100. An active region 115 can be disposed between the first and second semiconductor layers 110, 120. The active region 115 can have, for example, a pn junction, a double heterostructure, a single quantum well (SQW) structure, or a multiple quantum well (MQW) structure for generating radiation. In this case, the designation "quantum well structure" has no meaning regarding the quantized dimension. Therefore, it specifically includes quantum wells, quantum wires, and quantum dots, as well as any combination of these layers.

[0041] The active region 115 is provided by layers or a sequence of layers on the main surface perpendicular to the extending direction of the optical resonator 131. Typically, this type of semiconductor laser is called an edge-emitting semiconductor laser. However, as will be discussed later... Figures 2A to 4C As explained, even with this configuration, electromagnetic radiation can be emitted through the main surface 111 of the semiconductor layer device 112.

[0042] In addition, contact elements (not shown) can be provided to apply voltage to the semiconductor laser.

[0043] exist Figure 1B In the arrangement shown, three laser elements 1271, 1272, and 1273 are stacked on top of each other. Each individual laser element has a first semiconductor layer 110, a second semiconductor layer 120, and an active region 115. Here, the first semiconductor layer can each be of a first conductivity type, and the second semiconductor layer 120 can each be of a second conductivity type. The individual laser elements 1271, 1272, and 1273 are each connected to each other via interconnecting layers 1281 and 1282. The interconnecting layers 1281 and 1282 can each be tunnel junctions, thereby enabling electrical connection.

[0044] In the context of this application, the term "tunnel junction" typically refers to a series of highly doped semiconductor layers of first and second conductivity types. For example, a first highly doped layer of the first conductivity type can be disposed adjacent to and in contact with a first semiconductor layer 110 of the first conductivity type of laser elements 1271, 1272, and 1273. Furthermore, a second highly doped layer of the second conductivity type can be disposed adjacent to and in contact with a second semiconductor layer 120 of the second conductivity type of laser elements 1271, 1272, and 1273. Optionally, an intermediate layer can be disposed between the highly doped layers. The sequence of highly doped layers of the first and second conductivity types and the optional intermediate layer constitutes a tunnel diode. These tunnel diodes can be used to connect the respective laser elements 1271, 1272, and 1273 in series.

[0045] like Figure 1A As shown, a first resonator mirror 144 and a second resonator mirror 146 are also provided here. Furthermore, the semiconductor laser 10 includes a first absorption element 140 between the semiconductor layer device 112 and the first resonator mirror 144. Optionally, the semiconductor laser 10 also includes a second absorption element 147 between the semiconductor layer device 112 and the second resonator mirror 146.

[0046] It goes without saying that the number of laser elements 1271, 1272, and 1273 can be different from three.

[0047] according to Figure 1C In the illustrated embodiment, the first absorption element 140 can also be disposed only on one side of the semiconductor layer device 112, for example, between the semiconductor layer device 112 and the first resonator mirror 144. According to the embodiment, the generated electromagnetic radiation can be coupled out through the second resonator mirror 146. According to a further embodiment, the generated electromagnetic radiation can also be coupled out through the first resonator mirror 144. That is, in this case, the first absorption element 140 is disposed on the light output coupling side of the semiconductor laser 10.

[0048] The following is for reference. Figure 1DThe structure of the first absorption element 140 is described in more detail. This description is applied by analogy to the second absorption element 147. If the semiconductor laser 10 has the first and second absorption elements 140, 147, they can have the same structure or different structures from each other.

[0049] The first absorbing element 140 has one or more absorbing layers 143. The absorbing layers 143 are, for example, thin, highly absorbent layers. The thickness of the absorbing layers 143 can be, for example, less than 20 nm, or less than 5 nm. For example, the material of the absorbing layers 143 can be germanium. The absorbing layers 143 can also include tunnel junctions or other highly absorbent layers. For example, the absorbing layers 143 can contain some germanium monolayers. An optically transparent insulating layer 141, such as a transparent III-V semiconductor layer or a layer comprising SiO2, SiN, or a mixture of these materials, can be disposed between the semiconductor layer device 112 and the absorbing layers 143. The transparent insulating layer 141 is disposed, for example, to prevent short circuits between the absorbing layers 143 and the semiconductor layer device 112.

[0050] The transparent dielectric layer 142 disposed between the absorption layer 143 and the first resonator mirror 144 is, for example, made of a material configured such that the product of the refractive index and the layer thickness changes little with temperature. For example, the product of the refractive index and the layer thickness changes by less than 0.1 nm / K. Typically, for example, the dielectric layer 142 can contain a single layer, or optionally include multiple layers. For example, the optical thickness of the transparent dielectric layer 142 is sized such that the nodes of the standing wave formed at the target wavelength are located in the absorption layer 143, for example, at the center of the absorption layer 143. For example, the transparent dielectric layer 142 can include a transparent III-V semiconductor layer, a ZnSe layer, or a layer comprising SiO2, SiN, or a mixture of these materials.

[0051] A sequence of multiple absorption layers 143 and transparent dielectric layers 142 can be disposed between the semiconductor layer device 112 and the first resonator mirror 144. In this case, for example, the dielectric layers 142 disposed between adjacent absorption layers 143 are sized such that the distance d or optical distance between the centers of adjacent absorption layers 143 corresponds to an integer multiple of half the effective target wavelength of the laser. Here, the term "effective wavelength" relates to the wavelength in the relevant propagation medium (i.e., the transparent layer). Furthermore, the absorption elements are adjusted such that all absorption layers 130 are positioned at the location of minimum intensity of the main standing wave 148.

[0052] In this configuration of an absorbing element having a transparent insulating layer 141, an absorbing layer 143, and another transparent dielectric layer 142, and a first or second resonator mirror 144, 146, for example at the target wavelength of a semiconductor laser, the node of the formed standing wave 148 is located at the location of the absorbing layer 143. For example, the node can be located at the center of the absorbing layer 143 in each case. The term "node" here refers to a region where the electric field strength of the standing wave is zero. Figure 1D The magnitude of the electric field strength of standing wave 148 is shown. That is, the minimum values ​​shown correspond to the nodes of the standing wave.

[0053] Thus, when the semiconductor component operates at the target wavelength, no absorption occurs in the absorption layer 143. If the wavelength shifts with increasing temperature, absorption at that wavelength increases in the absorption layer 143. Specifically, in this case, what is now located in the region of the absorption layer 143 is not a node, but a region with a finite field strength (i.e., a non-zero field strength). Therefore, these modes are attenuated, and only those modes involving electric field strength that exist at the location of the absorption layer 143 are formed. Since the nodes of the standing wave 148 formed at the target wavelength exist at the location of the absorption layer 143, the electric field strength at the location of the absorption layer 143 is equal to zero. Therefore, the light is not absorbed by the absorption layer 143. In this way, it can be ensured that the semiconductor laser 10 emits electromagnetic radiation with the target wavelength. This effect can be enhanced by the absorption elements 140, 147, which in each case have multiple absorption layers 143 positioned as described above.

[0054] Thus, a wavelength-selective absorbing element is provided, which, in combination with a resonator mirror, achieves wavelength-selective reflection. For example, the resonator mirror can have a non-wavelength-dependent reflectivity. According to a further embodiment, a resonator mirror with a wavelength-dependent reflectivity can also be combined with a wavelength-selective absorbing element. For example, the first and / or second resonator mirrors 144, 146 can be implemented as metallic mirrors, for example, made of gold. According to a further embodiment, the first and / or second resonator mirrors 144, 146 can be implemented as dielectric mirrors. Generally, the term "dielectric mirror" includes any device that largely reflects incident electromagnetic radiation (e.g., >90%) and is non-conductive. For example, the dielectric mirror layer can be formed from a series of extremely thin dielectric layers, each with a different refractive index. For example, these layers can alternately have high refractive indices (e.g., n > 1.7) and low refractive indices (e.g., n < 1.7) and can be implemented as Bragg reflectors.

[0055] The described concept also applies to semiconductor lasers, wherein at least a portion of the resonator extends along a direction parallel to the main surface 111 of the semiconductor layer device 112, and radiation 135 is emitted through the first main surface 111 of the semiconductor layer device 112.

[0056] Figure 2A A surface-emitting semiconductor laser according to an embodiment is shown, comprising a resonator 131 extending parallel to the main surface 111. For example... Figure 2A As shown, the end face of the semiconductor layer device 112 is etched at a 45° angle. The dielectric layer 138 can be applied with adjacent tilted etched sidewalls. According to a further embodiment, the dielectric carrier substrate 100 can also be directly adjacent to the tilted etched sidewalls. Due to the refractive index difference between the semiconductor material of the semiconductor layer device 112 and the dielectric layer 138, total internal reflection occurs at each sidewall. As a result, the tilted sidewalls of the semiconductor layer device 112 act as specular reflective sidewalls 137. Therefore, the generated electromagnetic radiation is reflected towards the first main surface 111 of the semiconductor layer device 112. First and second resonator mirrors 144 and 146 are disposed on the first main surface 111.

[0057] In each case, the laser light is reflected by the first resonator mirror 144 and the second resonator mirror 146 into the semiconductor layer device having the active region 115. For example, a wavelength-dependent absorption element 140 can be provided between the semiconductor layer device 112 and the first resonator mirror 144 as described above. As mentioned above, a thin absorption layer is also included between the dielectric material layers. The position of the absorption layer corresponds to the position of the node of the standing wave formed between the specular reflection sidewall 137 and the first resonator mirror 144. Figure 2A In this configuration, multiple laser elements 1271, 1272, and 1273 are stacked on top of each other and interconnected via connecting layers 1281 and 1282. The connecting layers can again form tunnel junctions. The carrier substrate 100 is constructed in a manner corresponding to the shape of the semiconductor layer device. For example, the second resonator mirror 146 has a reflectivity lower than that of the first resonator mirror 144. Accordingly, the generated electromagnetic radiation 135 is coupled out through the first main surface 111 at the location of the second resonator mirror 146.

[0058] according to Figure 2B In the embodiment shown, the absorbing element 140 can also be disposed between the second resonator mirror, which has a lower reflectivity, and the semiconductor layer device 112. For example, in this case, the first resonator mirror 144 can be adjacent to the semiconductor layer device 112 without the absorbing element 140 inserted. In this case, the emitted electromagnetic radiation 135, after passing through the absorbing element 140 and the second resonator mirror 146, is emitted through a region of the first main surface 111 of the semiconductor layer device 112. Figure 2B Other components and references of semiconductor lasers Figure 2A The components described are similar or identical.

[0059] Figure 3A It shows Figure 2A , 5In the case of a semiconductor laser described in B, 3B, 4A, 4B, and 4C, at least a portion of the resonator extends along a direction parallel to the main surface 111 of the semiconductor layer device 112, and the generated electromagnetic radiation is emitted through the first main surface 111.

[0060] For example, according to Figure 2A , 2B The semiconductor lasers of the embodiments shown in 3B, 4A, 4B, and 4C have multiple laser elements 1271, 1272, and 1273 stacked on top of each other. The laser elements are interconnected and electrically connected in series, for example, via interconnecting layers 1281 and 1282. For example, each laser element 1271, 1272, and 1273 may have a first semiconductor layer 110 of a first conductivity type (e.g., p-conductivity), a second semiconductor layer 120 of a second conductivity type (e.g., n-conductivity), and an active region 115. The interconnecting layers 1281 and 1282 may each be implemented as a tunnel junction. The sidewalls of the semiconductor layer of the semiconductor layer arrangement 112 are etched at a 45° angle and covered with a dielectric layer 138. Due to the refractive index difference between the semiconductor layer and the adjacent dielectric layer, the interface between the semiconductor material and the dielectric layer acts as a total internal reflection mirror.

[0061] Therefore, the emitted radiation is emitted vertically through the first main surface 111 of the semiconductor layer stack 112. The absorbing element 140 has a plurality of absorbing layers 143 and a transparent dielectric layer 142 disposed between the absorbing layers 143. The thickness of the transparent dielectric layer 142 is determined such that, in each case, the reflective sidewall 137 is aligned with the adjacent resonator mirror (…). Figure 3A The standing wave formed between (not shown in the text) has a node, and the node is located at the position of the absorbing layer 143 (as mentioned above). Figure 1D (as described above). This ensures that the absorption layer 143 does not absorb at the target wavelength. In the case of wavelength shift, the absorption layer 143 absorbs, causing these components to be attenuated and forming wavelength-stable laser radiation.

[0062] Figure 3B A cross-sectional view of the semiconductor laser 10 is shown for illustration. Figure 3A Other components of the semiconductor laser shown. A resonator 131 with an active region 115 extends in a direction parallel to the first main surface 111, and radiation is emitted through the first main surface 111 of the semiconductor layer device 112. Figure 3BAs shown, a common absorption element 140 is disposed on the first main surface 111 of the semiconductor layer device 112. Therefore, the common absorption element 140 is disposed both between the first resonator mirror 144 and the semiconductor layer device 112, and also between the second resonator mirror 146 and the semiconductor layer device 112. The first and second resonator mirrors 144 and 146 are each disposed on the first main surface of the semiconductor layer device 112. The first and second resonator mirrors each extend in a plane parallel to the first main surface 111.

[0063] therefore, Figure 3A The components shown are in Figure 3B The following is shown in more detail. The thickness of the transparent dielectric layer 142 of the absorbing element 140 is s1, and the applicable relationship here is s1 = m * λ / 2, where m is a natural number. The active region 115 of each laser element 1271, 1272, 1273 is positioned such that the maximum value of the formed standing wave is set at the location of the active region 115 in each case. This ensures that the standing wave formed in the resonator 131 is guided in the active region 115 in each case. Therefore, for the layer thickness of individual laser elements 1272 and 1273, this produces respective relationships s2 = u * λ / 2 and s3 = n * λ / 2, where u and n are natural numbers. In each case, the wavelength specified here is always related to the wavelength (i.e., the effective wavelength) in the corresponding semiconductor medium.

[0064] The layer thicknesses of individual laser elements 1271, 1272, and 1273 can be the same or different in each case. If the layer thickness S2 of the second laser element 1272 and the layer thickness S3 of the third laser element 1273 satisfy the above relationship, then the first and second connecting layers 1281 and 1282 can represent loss channels for all amplified wavelengths except the target wavelength. For example, the first and second connecting layers 1281 and 1282 can be implemented as an absorption tunnel junction. Given this size, the nodes of the standing wave are located at the location of the tunnel junction in each case. Therefore, absorption of laser modes with wavelengths deviating from the target wavelength occurs. Therefore, even if the gain peak amplification changes, the emission wavelength may remain almost constant under temperature variations.

[0065] For example, the second resonator mirror 146 has a reflectivity of less than 100%. The first resonator mirror 144 has a higher reflectivity than the second resonator mirror 146. According to a further embodiment, the second resonator mirror 146 can also have a higher reflectivity than the first resonator mirror 144.

[0066] According to the embodiments described herein, the absorber layer 143 and the transparent dielectric layer 142 can be applied, for example, epitaxially or subsequently, for example, by sputtering, vapor deposition, etc. For example, the absorber layer 143 can contain some monolayer of absorber material, such as germanium.

[0067] Figure 4A A cross-sectional view of a semiconductor laser 10 according to an embodiment is shown. Figure 4A The semiconductor laser shown has Figure 3A and 3B The components shown are shown. An absorption element 140 is disposed between the first resonator mirror 144 and the semiconductor layer device 112. The absorption element 140 is also disposed between the second resonator mirror 146 and the semiconductor layer device 112. The generated electromagnetic radiation 135 is output through the second resonator mirror 146.

[0068] For example, the materials of the first and second semiconductor layers 110, 120 and the active region can be based on a GaAs material system and can contain GaAs semiconductor layers. In this case, the interconnect layers 1281, 1282 can have a tunnel junction containing highly doped AlGaAs (e.g., tellurium-doped or carbon-doped AlGaAs). According to a further embodiment, the tunnel junction can include, for example, highly doped GaAs doped with tellurium or carbon. For example, the layer thickness of the tunnel junction can be less than λ / 2, where λ corresponds to the effective wavelength in the corresponding propagation medium.

[0069] According to a further embodiment, one of the absorption layers 140, for example, between the semiconductor layer device 112 and the second resonator mirror 146, or between the semiconductor layer device 112 and the first resonator mirror 144, can be removed.

[0070] Figure 4B A cross-sectional view of a semiconductor laser according to an embodiment is shown, wherein an absorption element 140 is disposed between the semiconductor layer device 112 and the first resonator mirror 144 in the manner described above. In contrast, no absorption element 140 is disposed between the second resonator mirror 146 and the semiconductor layer device 112. For example, the second resonator mirror 146 is directly adjacent to the semiconductor layer device 112. The generated electromagnetic radiation 135 is output through the second resonator mirror 146.

[0071] Figure 4C An example is shown where the absorbing element 140 is disposed between the second resonator mirror 146 and the semiconductor layer arrangement 112. In contrast, no absorbing element 140 is disposed between the first resonator mirror 144 and the semiconductor layer arrangement 112. For example, the first resonator mirror 144 is directly adjacent to the semiconductor layer arrangement 112. The generated electromagnetic radiation 135 is output via the second resonator mirror 146.

[0072] As previously mentioned, by using a wavelength-selective absorption element between the semiconductor layer device and the resonator mirror, a semiconductor laser with improved temperature stability can be provided. Therefore, the performance of systems using semiconductor lasers can be improved. Furthermore, this semiconductor laser can be manufactured in a cost-effective manner.

[0073] Figure 5 A schematic apparatus of a LIDAR system 150 capable of using the described semiconductor laser 10 is shown. Laser radiation (typically pulsed laser radiation) emitted by the semiconductor laser 10 is emitted, for example, through a collimator optics unit 157 and a deflection / scanning unit 154. A target beam 153 is incident on a target 156 and reflected by it. A reflected beam 155 appears in the process. The reflected beam 155 is fed to a detector 160 through a receiving optics unit 152. The distance to the target 156 can be determined based on the time difference between the emission and reception of the laser pulse.

[0074] Because semiconductor lasers can operate at a stable wavelength even under varying temperatures, narrowband detectors can be used. For example, the detector can use a narrow wavelength window of less than 10 nm, less than 5 nm, or even less than 1 nm.

[0075] As a result, the effects of sunlight can be reduced, and the signal-to-noise ratio can be improved. Consequently, for example, lower laser power is required to measure the same distance. Alternatively, the system range can be increased while keeping the power constant. Overall, the system performance is improved. Furthermore, the laser can operate at lower power to perform the same measurements with a constant signal-to-noise ratio, thus reducing energy consumption. Moreover, the described semiconductor laser can be manufactured cost-effectively and simply.

[0076] This semiconductor laser can also be used in other applications. For example, it can be used in metrology, sensor technology, and applications requiring temperature-stable wavelengths, such as display devices where minimal color shift is desired.

[0077] Although specific embodiments have been illustrated and described herein, those skilled in the art will recognize that the specific embodiments shown and described can be replaced by various substitutions and / or equivalent configurations without departing from the scope of the invention. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, the invention is limited only by the claims and their equivalents.

[0078] Figure Labels

[0079] 10 Semiconductor Lasers

[0080] 100 Carrier substrate

[0081] 110 First Semiconductor Layer

[0082] 111 First Primary Surface

[0083] 112 Semiconductor Layer Device

[0084] 115 Active Area

[0085] 120 Second semiconductor layer

[0086] 1271 First Laser Element

[0087] 1272 Second laser element

[0088] 1273 Third laser element

[0089] 1281 First Connector Layer

[0090] 1282 Second Connector Layer

[0091] 131 resonator

[0092] 135 laser radiation

[0093] 137 Specular Reflective Sidewall

[0094] 138 dielectric layer

[0095] 140 First Absorption Element

[0096] 141 Transparent Insulating Layer

[0097] 142 Transparent dielectric layer

[0098] 143 Absorption Layer

[0099] 144 First resonator mirror

[0100] 146 Second resonator mirror

[0101] 147 Second Absorption Element

[0102] 148 Standing Waves

[0103] 150 LIDAR system

[0104] 151 beam splitter

[0105] 152 Receiving Optical Units

[0106] 153 Target Beam

[0107] 154 deflection / scanning units

[0108] 155 reflected beam

[0109] 156 Targets

[0110] 157 Collimator Optical Unit

[0111] 160 detectors

Claims

1. A semiconductor laser (10), comprising: a semiconductor layer arrangement (112) having an active region (115) for generating radiation, a first resonator mirror (144), a second resonator mirror (146) and a resonator (131) arranged between the first resonator mirror (144) and the second resonator mirror (146), the resonator (131) extending in a direction parallel to a main surface (111) of the semiconductor layer arrangement (112), and a first wavelength-selective absorption element (140) arranged between the semiconductor layer arrangement (112) and the first resonator mirror (144), wherein the first wavelength-selective absorption element (140) has an absorption layer (143) arranged at a position corresponding to a position of a node of an electrical field strength at a target wavelength, and the first wavelength-selective absorption element (140) further has a transparent dielectric layer (142) between the first resonator mirror (144) and the absorption layer (143), wherein the transparent dielectric layer (142) is dimensioned such that a node of a standing wave formed at the target wavelength is arranged in the absorption layer (143), wherein the planes of the transparent dielectric layer (142) and the absorption layer (143) extend perpendicular to a direction of light propagation; wherein, if the semiconductor laser is operated at the target wavelength, no absorption occurs in the absorption layer (143), and, if the wavelength is shifted with increasing temperature, the absorption in the absorption layer (143) for this wavelength increases.

2. The semiconductor laser (10) according to claim 1, further comprising a second wavelength-selective absorption element (147) arranged between the semiconductor layer arrangement (112) and the second resonator mirror (146).

3. The semiconductor laser (10) as claimed in claim 1, wherein The first wavelength-selective absorption element (140) has a plurality of absorption layers (143), wherein the optical distance between the centers of at least two adjacent absorption layers (143) corresponds in each case to an integer multiple of half the target wavelength arranged in the transparent dielectric layer (142) between the absorption layers (143).

4. The semiconductor laser (10) according to any one of claims 1 to 3, wherein The material of the absorption layers (143) contains germanium, or the absorption layers (143) are realized as tunnel junctions.

5. The semiconductor laser (10) as claimed in claim 3, wherein The transparent dielectric layer (142) contains SiO2, SiN, ZnSe or a transparent III-V semiconductor material.

6. The semiconductor laser (10) as claimed in claim 1 or 3, wherein For the target wavelength at a predefined temperature, there is a maximum gain within the active region (115).

7. The semiconductor laser (10) as claimed in any of claims 1 to 3, wherein The semiconductor layer arrangement (112) has a plurality of laser elements (1271, 1272, 1273).

8. The semiconductor laser (10) as claimed in claim 7, wherein The laser elements (1271, 1272, 1273) are connected to one another by at least one absorption connection layer (1281, 1282).

9. The semiconductor laser (10) as claimed in claim 8, wherein The at least one absorption connection layer (1281, 1282) is arranged at a position corresponding to a position of a node of an electrical field strength at a target wavelength.

10. The semiconductor laser (10) as claimed in claim 8, wherein The at least one absorption connection layer (1281, 1282) is realized by a tunnel junction.

11. The semiconductor laser (10) as claimed in any of claims 1 to 3, wherein The lateral boundary of the semiconductor layer arrangement extends obliquely such that the generated electromagnetic radiation (135) is reflected in the direction of the first main surface (111) of the semiconductor layer arrangement (112), and a first resonator mirror (144) and a second resonator mirror (146) are arranged on the first main surface (111) of the semiconductor layer arrangement (112).

12. The semiconductor laser (10) as claimed in claim 11, wherein The first wavelength-selective absorption element (140) is arranged between the first main surface (111) and the first resonator mirror (144).

13. The semiconductor laser (10) as claimed in claim 12, wherein The first wavelength-selective absorption element (140) extends over the first main surface (111) and is also arranged between the first main surface (111) and the second resonator mirror (146).

14. The semiconductor laser (10) as claimed in claim 11, wherein The semiconductor layer arrangement (112) has a plurality of laser elements (1271, 1272, 1273) and also at least one absorption connection layer (1281, 1282), wherein the layer thickness s2 of at least one laser element (1271, 1272, 1273) measured in the perpendicular direction satisfies the relationship s2 = u * λ / 2, wherein u is a natural number and λ denotes the wavelength in the semiconductor layer of the laser element (1271, 1272, 1273).

15. A LIDAR system (150) comprising a semiconductor laser (10) as claimed in any one of claims 1 to 14.

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