Laser diode with integral thermal aperture

Abstract

The present invention relates to a diode laser with an integral thermal aperture. The laser diode (10) according to the present invention comprises an active layer (14) formed between an n-doped semiconductor material (12) and a p-doped semiconductor material (16), the active layer (14) forming an active region (40) having a width w along a longitudinal axis for generating electromagnetic radiation, and a thermal conductivity k of the corresponding semiconductor materials (16, 12) in the p-doped semiconductor material (16) and / or the n-doped semiconductor material (12). bulk A thermal conductivity coefficient k smaller than block A layer-shaped thermal opening (18) having a thickness of 100 Å is formed for spatially selective heat transport from the active region (40) to the opposite side of the active layer (14) of the corresponding semiconductor material (16, 12).

Description

explanation

[0001] The present invention relates to a laser diode with an integral thermal aperture.

[0002] Broad-area diode lasers (BALs) can exhibit particularly high efficiency and brightness. These emitters can reliably achieve output powers in excess of 15 W. Because they are the most efficient sources of near-infrared (NIR) radiation, BALs are widely used as pump sources for solid-state and fiber lasers. BALs are also key components of fiber-coupled laser systems designed to deliver high-radiance beams for materials processing with high wall-plug efficiency. To increase the output power of these systems and reduce their cost, improving the beam quality of the slow axis is important because it enables the coupling of more emitters into low-numerical-aperture (NA) fibers.

[0003] However, at high optical output powers and associated operating currents, there is generally a significant degradation of beam quality, which is particularly detrimental to fiber coupling. It has been shown that slow-axis thermal lensing (rather than charge carrier or gain-induced waveguiding) is one of the main causes of beam quality degradation as the operating current increases (Bai, J. Get al., Mitigation of Thermal Lensing Effect as a Brightness Limitation of High-Power Broad-Area Diode Lasers, Proc. SPIE 7953, 79531F (2011)). Therefore, the decisive factor in the degradation of beam quality at high output powers is the formation of a lateral temperature gradient due to the temperature increase in the central region under the laser stripe. This leads to a local increase in the refractive index, thus creating additional lateral waveguides and resulting in a larger divergence angle.

[0004] In particular, extending the laser cavity or influencing the heat flow between the laser diode and the submount (thermal path technology; see, for example, Bai et al., German Patent Publication No. 102013114226 and U.S. Patent Application Publication No. 20160315446) has been proposed to improve thermal transport. This reduces the lateral temperature gradient and flattens the thermal lensing. However, diode lasers with long cavities are expensive to manufacture. However, it has recently been shown that a high thermal barrier forms at the interface between the laser diode and the appropriate metallization, significantly reducing the effectiveness of thermal path technology against thermal lensing (Rieprich, J. et al., Chip-carrier thermal barrier and its impact on lateral thermal lens profile and beam parameter product in high-power broad-area lasers, J. Appl. Phys. 123, 125703 (2018)).

[0005] Another method to reduce the lateral temperature gradient is to further heat the laser diode using an external heat source (Hohimer, J.P., Mode control in broad area diode lasers by thermally induced lateral index tailoring, Appl. Opt. Phys. Lett. 52, 260 (1988)). However, integrating an external heat source into a diode laser is very complicated and therefore not very practical.

[0006] Reduction of lateral temperature gradients can also be achieved through specially adapted layer structures (Winterfeldt, M. et al., Assessing the Influence of the Vertical Epitaxial Layer Design on the Lateral Beam Quality of High-Power Broad Area Diode Lasers, Proc. SPIE 9733, 97330O (2016)). However, such adjustments can only slightly improve the lateral beam quality. Furthermore, such adjustments are only possible for specific laser designs. DISCLOSURE OF THE INVENTION

[0007] It is therefore an object of the present invention to provide a laser diode that is capable of reducing lateral temperature gradients and flattening the thermal lens that is generated. In particular, the laser diode should not require an external heat source or adjustments in the layer structure (e.g., metallization) external to the chip, i.e., should be based solely on a monolithic integrated structure within the diode laser.

[0008] These objects are achieved according to the invention by the features of patent claim 1. Suitable embodiments of the invention are contained in the respective dependent claims.

[0009] A laser diode according to the present invention comprises an active layer formed between n-doped semiconductor material and p-doped semiconductor material, the active layer forming an active region along a longitudinal axis having a width w for generating electromagnetic radiation, and in the p-doped semiconductor material, a thermal conductivity coefficient k of the p-doped semiconductor material (e.g., the p-doped semiconductor material between the active region and the cooled underside of the laser diode). bulk A thermal conductivity coefficient k smaller than block and a thermal opening formed in the shape of a layer having a thermal conductivity coefficient k of the n-doped semiconductor material is formed for spatially selective heat transport from the active region to a side of the p-doped semiconductor material opposite the active region. bulk A thermal conductivity coefficient k smaller thanblock A layer-shaped thermal opening having a thickness of 100 Å is formed in the n-doped semiconductor material for spatially selective heat transport from the active region to a side of the n-doped semiconductor material opposite the active layer.

[0010] Thus, thermal openings according to the invention can be formed in both p-doped and n-doped semiconductor materials, with the formation preferably taking place in the corresponding semiconductor material. In the following, p-side thermal openings are considered as examples, but the description also applies to n-side thermal openings.

[0011] A laser diode is understood to be a layer structure (a so-called laser chip) made of semiconductor materials with or without metallization. The term semiconductor material is used generally herein to refer to any semiconductor material or combination of semiconductor materials, such as the AlInGaAsNSb material system. In particular, n-doped and p-doped semiconductor materials may each include layer systems of corresponding semiconductor materials of different types or doping levels with different compositions. Therefore, the terms n-side semiconductor material and p-side semiconductor material should be understood to be synonymous.

[0012] The active layer is formed in the transition region between n-doped and p-doped semiconductor materials. Electromagnetic radiation is generated in the electrically pumped region of the active layer within the active region. Most of the heat generated during laser diode operation is generated there and must be dissipated accordingly. This can be done via a submount, which can be thermally connected, for example, to the underside of the laser diode below the active region. The connection between the underside of the laser diode and the submount is state-of-the-art and can be achieved by soldering or gluing.

[0013] In accordance with the present invention, for spatially selective heat transport from the active region to the underside of the laser diode, the thermal conductivity coefficient k of the surrounding p-doped semiconductor material is reduced. bulk A thermal conductivity coefficient k smaller than blockA layer-shaped thermal aperture having a thermal conductivity of π / 2 is formed in the p-doped semiconductor material below the active region. The thermal conduction coefficient (also called thermal conductivity or thermal conductance coefficient) determines the heat flow through the material based on thermal conduction. The lower this value, the worse the material's thermal conduction properties. According to the present invention, the thermal aperture is intended to reduce the lateral temperature gradient (i.e., flatten the thermal lens) by counteracting the spatial lateral expansion of the heat flow in the region between the active region and the underside of the laser diode by locally increasing the thermal resistance of the conventional lateral expansion region (laterally below the active region). As a result of this increased thermal resistance, the local temperature in the lateral region (thermal aperture) increases as more heat is generated within the stripe (in the central region) with increasing output power. This corresponds to a lower temperature gradient between the central and lateral regions, and therefore a flatter thermal lens.

[0014] Regarding the relationship between the two thermal conductivity coefficients, the thermal conductivity coefficient k of the p-doped semiconductor material under the active region bulk is particularly important. For p-doped semiconductor materials consisting of several layers, each layer has a slightly different thermal conductivity k layer Then, the thermal conductivity coefficient k bulk can be considered as the resulting thermal conductivity of all layers participating in the heat flow. As an approximation, the average thermal conductivity of the p-doped semiconductor material below the active region is also taken as the thermal conductivity k of the p-doped semiconductor material. bulk Alternatively, as an approximation, the thermal conductivity coefficient k of the p-doped semiconductor material can be bulk is the thermal conductivity k of the p-contact layer of the p-doped semiconductor material KS It can also be equal to

[0015] Therefore, the idea of ​​the present invention is to realize a flat thermal lens by integrating a monolithically integrated thermal opening (internal thermal path technology) directly into the laser diode. In contrast, external thermal path technology is less effective due to the presence of an inherent semiconductor-metal thermal barrier. The thermal opening according to the present invention can also be placed very close to the active region, minimizing the spread of lateral heat flow and resulting in a particularly flat thermal lens. Therefore, thermal path technology known from the prior art can be applied inside the laser diode, significantly increasing its effectiveness and efficiency.

[0016] Preferably, the thermal opening is made of a semiconductor material, which has a low thermal conductivity coefficient k block It should have a particularly low thermal conductivity (for example, for AlInGaAsP composites on GaAs substrates: GaAs and AlGaAs as p-type semiconductor materials). Furthermore, a high electrical conductivity is preferred. In particular, the thermal opening can be constructed from the same semiconductor material system as the p-doped semiconductor material (e.g., for AlInGaAsP composites on GaAs substrates: GaAs and AlGaAs as p-type semiconductor materials). By varying the indium and / or phosphorus content (e.g., for AlInGaAsP composites on GaAs substrates: GaAs and AlGaAs as p-type semiconductor materials, InGaP or InGaAsP as thermal opening), the thermal conductivity coefficient k block can be lowered.

[0017] Preferably, a particularly small thermal conductivity coefficient k block To achieve this, the thermal apertures are formed from periodically alternating materials (e.g., different semiconductors, or semiconductors and air) with numerous regular alternations between the materials, resulting in a thermal conductivity k layer The heat transport across the interface is limited and the thermal conductivity k block is further reduced (see J. Piprek et al., Thermal conductivity reduction in GaAs-AlAs distributed Bragg reflectors, in IEEE Photon. Tech. Lett. 10, 81 (1998)).

[0018] Preferably, the thermal openings can be realized in photonic crystal structures. Photonic crystal structures are understood to be 3D periodic nanostructures that can affect the movement of photons within a crystal lattice. Typically, to create a high refractive index contrast, openings ("air holes") filled with air or other particularly low-refractive-index materials are formed within the structure. These openings and the transition of multiple materials cause a particularly significant reduction in the thermal conductivity of these materials. In summary, photonic crystal structures can be used to create regions with good optical properties and very low thermal conductivity. The same applies to 1D periodic lattices (superlattices) in which thin layers of two different materials, particularly semiconductor materials, are alternately arranged on top of each other.

[0019] Thus, in a laser diode according to the invention, the optical properties of the region below the active region can be largely maintained despite the additional thermal aperture.

[0020] For example, GaAs(k KS ≒44W / (m·K)) or Al x Ga 1-x As(k KS ≒11~91W / (m·K)), InGaP (k block ≒5W / (m·K)), InGaAsP(k block ≒5W / (m·K)), InGaAsSb, or InGaP-InGaAsP superlattice (k block ≈2.5 W / (m·K)) thermal aperture can be constructed.

[0021] For sufficient opening effect, the thermal conductivity coefficient k block must be as low as possible. The thermal conductivity coefficient k block is the corresponding bulk value k bulk In the InGaP-InGaAsP superlattice, the thermal conductivity coefficient k blockcan be achieved, which is about half the value of the thermal conductivity coefficient k of InGaP and InGaAsP (see J. Piprek et al., Thermal conductivity reduction in GaAs-AlAs distributed Bragg reflectors, in IEEE Photon. Tech. Lett. 10, 81 (1998)). However, much lower thermal conductivities can be achieved with photonic crystal structures.

[0022] Preferably, the thermal apertures form gap-shaped passage regions arranged parallel to the active layer for heat flow from the active region toward the outside of the laser diode (e.g., to the underside of the p-side where the heat sink is provided in the case of a p-side thermal aperture). In such a configuration, the thermal apertures can confine heat flow along the entire resonator axis (z-axis) to a slit-shaped passage. For efficiency reasons, a centrosymmetric (inward) arrangement of the slit-shaped passage region relative to the active region is preferred.

[0023] Preferably, the lateral distance dx between the outer edge (lateral boundary in the lateral direction) of the active region and the nearest inner edge of the thermal opening (lateral boundary facing the active region) is -w / 6≦dx≦+w / 6. This means that the distance preferably depends on the width w of the active region and is selected so that the inner edge of the thermal opening can have both positive and negative lateral distances relative to the outer edge of the active region. It is particularly preferred if the distance dx is 0, i.e., the outer edge of the active region and the corresponding inner edge of the thermal opening spatially coincide when projected onto the underside of the laser diode.

[0024] Preferably, the vertical distance dy between the center of the active layer and the top of the thermal aperture is 0 μm≦dy≦1 μm. This means that the top of the thermal aperture is preferably located directly below the center of the active layer, but at a maximum distance of 1 μm from it. A minimum distance provides the highest aperture effect, but may adversely affect optical properties. A distance greater than 1 μm may result in ineffective suppression of the lateral spread of heat flow.

[0025] Preferably, the thermal opening has an opening thickness d between 0.3 μm and 3 μm. block Thicker thermal openings can provide greater suppression of the lateral spread of heat flow.

[0026] Preferably, the p-doped semiconductor material (with integral thermal apertures) has a total layer thickness d of 0.5 μm to 10 μm, more preferably 1 μm to 5 μm, even more preferably 2 μm to 3 μm.

[0027] Preferably, the n-doped semiconductor material has a thermal opening formed in layers, and the p-doped semiconductor material has a thermal opening formed in layers. The n-doped semiconductor material thermal opening can functionally correspond to the p-doped semiconductor material thermal opening. In this regard, all information provided in this description regarding the p-doped semiconductor material thermal opening applies accordingly, taking into account the doping variations. Preferably, the n-doped semiconductor material thermal opening and the p-doped semiconductor material thermal opening can be constructed symmetrically with respect to the active layer. This symmetry can refer in particular to the geometric and / or material formation of the thermal opening. However, for example, if the p-doped and n-doped semiconductor materials have different thicknesses and distance adjustment is required, the thermal openings can also be formed differently. Such an embodiment is useful when the laser diode is mounted for double-sided cooling, i.e., when heat extraction can be performed on both sides of the laser diode.

[0028] Further preferred embodiments of the invention result from the features of the dependent claims.

[0029] The various embodiments of the invention referred to in this application can be usefully combined with one another, unless otherwise specified in individual cases.

[0030] The invention will now be described in the following by way of example with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a schematic diagram of an exemplary prior art laser diode without a thermal aperture. [Figure 2] 1 is a schematic diagram of a first exemplary embodiment of a laser diode according to the present invention having a thermal aperture; [Figure 3] 1 is a simulation of temperature as a function of lateral position (x-axis) within the active region. [Figure 4] Simulation of the normalized thermal lens curvature coefficient |B2| as a function of the thermal conductivity coefficient kKS of the p-contact layer. [Figure 5] 10 is a simulation of the normalized thermal lens curvature coefficient |B2| as a function of the aperture thickness dblock. [Figure 6] 10 is a simulation of the normalized thermal lens curvature coefficient |B2| as a function of the lateral distance dx. [Figure 7] 5 is a simulation of the temperature difference ΔT between the temperature T and the peak temperature Tpeak at position x=0 as a function of lateral position (x-axis) for a structure with KS material according to FIG. 4. [Figure 8] 3 is a schematic diagram of a second exemplary embodiment of a laser diode according to the present invention having two thermal apertures; Detailed Description of the Drawings

[0032] 1 shows a schematic diagram of an exemplary conventional laser diode without a thermal aperture. The illustrated diode laser comprises a laser diode 10 having an active layer 14 formed between an n-doped semiconductor material 12 and a p-doped semiconductor material 16, the active layer 14 defining an active region 40 along its longitudinal axis having a width w for generating electromagnetic radiation, and a submount 30 thermally connected to the p-side underside of the laser diode 10 below the active region 40. The thermally conductive connection may be formed by an intermediate solder layer 20, the solder intended to provide optimal heat transfer between the underside of the laser diode 10 and the submount 30.

[0033] In particular, the laser diode 10 can have a multilayer structure including an n-substrate, an n-clad layer on the n-substrate, an n-waveguide layer on the n-clad layer, an active layer 14 on the n-waveguide layer, a p-waveguide layer on the active layer 14, a p-clad layer on the p-waveguide layer, a p-contact layer on the p-clad layer, and a metal p-contact on the p-contact layer.

[0034] The losses occurring as heat during the operation of the laser diode in the active region 40 must be dissipated away from the active region 40. For this purpose, the submount 30 is usually used as a corresponding heat sink. However, the heat flow from the active region 40 towards the submount 30 spreads strongly laterally, resulting in a non-uniform temperature distribution in the region below the active region 40. The resulting temperature distribution has a thermo-optic effect on the generated electromagnetic radiation and can contribute to a degradation of the beam quality during radiation emission by forming a thermal lens in this region.

[0035] 2 shows a schematic diagram of a first exemplary embodiment of a laser diode with a thermal aperture according to the present invention. The illustrated diode laser comprises a laser diode 10 having an active layer 14 formed between an n-doped semiconductor material 12 and a p-doped semiconductor material 16, the active layer 14 defining an active region 40 along its longitudinal axis (longitudinal, z-axis) having a width w for generating electromagnetic radiation, and a submount 30 thermally conductively connected to the underside of the p-side of the laser diode 10 below the active region 40. This corresponds as closely as possible to the structure described with reference to FIG. 1.

[0036] However, in the p-doped semiconductor material 16, the thermal conductivity coefficient k of the p-doped semiconductor material 16 (below the active region 40) is increased due to spatially selective heat transport from the active region 40 to the side of the p-doped semiconductor material 16 opposite the active layer 14 (below the laser diode 10), and thus to the submount 30. bulk A thermal conductivity coefficient k smaller than blockAs an approximation, the average thermal conductivity of the p-doped semiconductor material 16 is also approximately equal to the thermal conductivity k of the p-doped semiconductor material below the active region 40. bulk Alternatively, the thermal conductivity coefficient k of the p-doped semiconductor material 16 can be bulk is the thermal conductivity k of the p-contact layer of the p-doped semiconductor material 16 KS can also be made approximately equal to

[0037] Again, the thermally conductive connection can be made by an intermediate solder layer 20 intended to allow optimal heat transfer between the underside of the laser diode 10 and the submount 30. The connection can also be made by bonding using, for example, a thermally conductive adhesive.

[0038] The thermal opening 18 forms a slit-like passage area parallel to the active layer 14 for heat flow 42 from the active region 40 toward the underside of the laser diode 10. The slit-like passage area is located below and inside the active region 40 in the figure. Lateral propagation of the heat flow 42 from the active region 40 toward the submount 30 is suppressed by the thermal opening 18 of the present invention, resulting in a mostly parallel heat flow 42. The high thermal resistance of the thermal opening 18 results in a localized increase in the temperature of the active region 40 (i.e., heating in the lateral regions) as more heat is generated by the active region 40 with increasing output power. This results in a more uniform temperature distribution in the region below the active region 40 between the central region (directly below the active region) and the thermal opening (lateral region). Therefore, the formation of a thermal lens in this region is also suppressed, improving beam quality during radiation emission.

[0039] The figure further shows the horizontal distance dx between the outer edge of the active region 40 and the nearest inner edge of the thermal opening. The vertical distance dy between the center of the active region 14 and the thermal opening 18 is also shown. The opening thickness d of the thermal opening 18 is block and the total layer thickness d of the p-doped semiconductor material 16 are also shown.

[0040] Therefore, the discussion also applies to thermal apertures 18 formed in n-doped semiconductor material 12. In this case, a corresponding submount 30 above the active region 40 can be thermally conductively connected to the n-side top of the laser diode 10 to reduce the lateral spread of upward heat flow 42.

[0041] Figure 3 shows a simulation of temperature as a function of lateral position (x-axis) within the active region. The simulation shows the optical power P opt The simulation is performed for a GaAs-based broad-area diode laser (BAL) with a stripe width of w = 90 μm operating at 10 W, at a vertical position (y-axis) of y = 0, i.e., at the center of the active layer (see M. Elattar et al, High-brightness broad-area diode lasers with enhanced self-aligned lateral structure, Semicond. Sci. Technol. 35, 095011 (2020)). The simulated BAL corresponds to a typical structure consisting of an active region (AZ) between n-doped and p-doped semiconductor materials. The p-doped semiconductor material is Al grown on the AZ. x Ga 1-x As waveguide layer (WL), followed by Al x Ga 1-xThe simulation consists of an As cladding layer (MS) and finally a GaAs contact layer (KS), on top of which a contact metal is subsequently deposited. The simulation (which corresponds to the corresponding experimental results) includes a thermal barrier at the KS-metal interface. The term thermal lens curvature coefficient B2 is the quadratic term in the quadratic fitting of the obtained thermal profile (Rieprich, J. et al., Chip-carrier thermal barrier and its impact on lateral thermal lens profile and beam parameter product in high-power broad-area lasers, J. Appl. Phys. 123, 125703 (2018)). The quadratic fitting was performed in the simulation for the region within the stripe width w = 90 μm. An exemplary conventional diode laser in the simulation shows that a thermal profile with a curvature profile between approximately 45°C at the edge of the wide strip and approximately 51°C in the center is obtained.

[0042] Figure 4 shows the thermal conductivity of the p-contact layer, k KS The normalized thermal lens curvature coefficient |B2| is simulated as a function of k. In the reference structure, the KS is made of GaAs (k KS ≒44W / (m·K)). GaAs is replaced with InGaP (k block ≒5W / (m·K)), InGaAsP(k block ≒5W / (m K)), InGaP-InGaAsP superlattice (k block ≒2.5W / (m·K; see J. Piprek et al., "Thermal conductivity reduction in GaAs-AlAs distributed Bragg reflectors," in IEEE Photon. Tech. Lett. 10, 81 (1998)). airSubstituting a material with a lower thermal conductivity, such as ≈0.026 W / (m K), reduces the normalized thermal lens curvature coefficient |B2|, and correspondingly weakens the thermal lens. This reduces the far-field angle and therefore improves beam quality. Specifically, simulations show that a 5% reduction in the normalized thermal lens curvature coefficient |B2| is equivalent to a reduced thermal conductivity coefficient k KS It was shown that a thermal conductivity of ≒18 W / (m K) can be achieved. KS A 10% reduction can be achieved with a thermal conductivity of ≈7W / (m·K). For a 15% reduction, the thermal conductivity must be k KS It must be ≒2.5W / (m·K).

[0043] Figure 5 shows the opening thickness d block Figure 1 shows the simulation of the normalized thermal lens curvature coefficient |B2| as a function of GaAs(KS) or Al x Ga 1-x Replacing the As(MS, WL) layer with InGaP (which has a low thermal conductivity k) reduces the normalized thermal lens curvature coefficient |B2| and correspondingly weakens the thermal lens formed. This reduces the far field angle and therefore improves the beam quality. In particular, simulations show that a 5% reduction in the normalized thermal lens curvature coefficient |B2| reduces the beam quality by 10% for an aperture thickness d block It was shown that the aperture thickness d can be achieved at 688 nm. block At ≈1375 nm a reduction of 10% can be achieved.

[0044] Figure 6 shows a simulation of the normalized thermal lens curvature coefficient |B2| as a function of the lateral distance dx. Here, the KS is assumed to be made of InGaP. It can be observed that the thermal lens curvature coefficient |B2| can be most effectively reduced when dx = 0, i.e., when the thermal and especially conductive slit-like passage area below the active region is aligned completely inside the laser stripe.

[0045] FIG. 7 shows the temperature T as a function of lateral position (x-axis) and the peak temperature T at position x=0 for the structure with the KS material shown in FIG.peak Figure 1 shows a simulation of the temperature difference ΔT between GaAs and a material with a lower thermal conductivity. The curves show the reduction in the curvature of the thermal lens when GaAs is replaced with a material with a lower thermal conductivity.

[0046] FIG. 8 shows a schematic diagram of a second exemplary embodiment of a laser diode according to the present invention, having two thermal apertures. The illustrated laser diode 10 corresponds in principle to the first embodiment of the laser diode 10 according to the present invention, having thermal apertures 18, shown in FIG. 2. Therefore, the individual reference numerals and the respective designations of the individual features apply accordingly. However, in contrast to the illustration in FIG. 2, a structure is shown here with thermal apertures 18 according to the present invention in both the p-doped semiconductor material 16 below the active layer 14 and the n-doped semiconductor material 12 above the active layer 14. A first submount 30a is thermally conductively connected to the underside of the laser diode 10 below the active region 40. Furthermore, a second submount 30b is thermally conductively connected to the top of the laser diode 10 above the active region 40. Therefore, cooling can be performed on both sides of the laser diode 10, thereby effectively suppressing the lateral spread of heat flow 42 to both the top and bottom of the laser diode 10 via the thermal apertures 18. Such an embodiment is useful when the laser diode 10 is mounted for double-sided cooling, i.e., when heat extraction can occur on both sides of the laser diode 10. The illustrated laser diode is symmetrical with respect to the active layer 14.

[0047] 10 Laser Diode 12 n-doped semiconductor materials 14 Active layer 16 p-doped semiconductor materials 18 Thermal Openings 20 solder layer 30 Submount 30a First submount 30b Second submount 40 active area 42 Heat flow dx Lateral distance (low speed axis) dy Vertical distance (fast axis) d block Opening Thickness w width

Claims

1. 1. A laser diode (10) comprising an active layer (14) formed between an n-doped semiconductor material (12) and a p-doped semiconductor material (16), the active layer (14) forming an active region (40) having a width w along a longitudinal axis for generating electromagnetic radiation, In the n-doped semiconductor material (12) or the p-doped semiconductor material (16), a thermal conductivity coefficient k of each doped semiconductor material (12, 16) is selected for spatially selective heat transport from the active region (40) to the side of each doped semiconductor material (12, 16) opposite the active layer (14). ｂｕｌｋ A thermal conductivity coefficient k smaller than ｂｌｏｃｋ A thermal opening (18) is formed in the shape of a layer, the laser diode (10) is based on GaAs or Al x Ga 1-x As, and the thermal aperture (18) is made of InGaP, InGaAsP, InGaAsSb or an InGaP-InGaAsP superlattice; the thermal opening (18) has an opening thickness d block of 0.3 μm to 3 μm; A laser diode (10) characterized by:

2. 10. The laser diode (10) of claim 1, wherein the thermal aperture (18) is formed of periodically alternating materials.

3. A laser diode (10) as described in claim 1 or 2, wherein the thermal opening (18) is realized in a photonic crystal structure.

4. A laser diode (10) as described in claim 1, wherein the thermal opening (18) is conductive.

5. 2. The laser diode (10) of claim 1, wherein the thermal opening (18) forms a slit-shaped passage area arranged parallel to the active layer (14) for heat flow (42) from the active region (40) toward the outside of the laser diode (10).

6. 6. The laser diode (10) of claim 5, wherein the slit-shaped passage region is disposed inwardly with respect to the active region (40).

7. A laser diode (10) as described in claim 1, wherein the n-doped semiconductor material or the p-doped semiconductor material having the thermal opening (18) has a total layer thickness d of 0.5 μm to 10 μm.

8. 2. The laser diode (10) of claim 1, wherein a lateral distance dx between an outer edge of the active region (40) and a nearest inner edge of the thermal aperture (18) is -w / 6≦dx≦+w / 6.

9. 2. The laser diode (10) of claim 1, wherein a vertical distance dy between the center of the active layer (14) and the top of the thermal aperture (18) is 0 μm≦dy≦1 μm.

10. The thermal conductivity coefficient k ｂｌｏｃｋ is the corresponding thermal conductivity coefficient k ｂｕｌｋ 2. The laser diode (10) of claim 1, wherein the .lambda.

11. 2. The laser diode (10) of claim 1, wherein a layered thermal aperture (18) is formed in the n-doped semiconductor material (12) and a layered thermal aperture (18) is formed in the p-doped semiconductor material (16).

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