Vcsel array with suppressed coherent coupling from optical feedback

Abstract

A VCSEL array has two or more VCSELs which are arranged on a common substrate and each have an in particular identical epitaxial structure with a first distributed Bragg reflector, DBR, an active zone, and a second distributed Bragg reflector, DBR, wherein the VCSEL array is designed in such a way that the wavelengths of two of the VCSELs differ by at least 0.003 nm and at most 5 nm.

Description

[0001] Applicant:

[0002] TRUMPF Photonic Components GmbH Lise-Meitner-Str. 13 89081 Ulm Germany

[0003] VCSEL array with suppressed coherent coupling from optical feedback

[0004] The invention relates to an array of vertical cavity surface-emitting semiconductor lasers (VCSELs) and a method for producing such a VCSEL array.

[0005] In a VCSEL array, several VCSELs are arranged on a substrate, with each VCSEL representing an independent laser source or emitter.

[0006] VCSEL arrays are basically known from US 9,065,254 B2.

[0007] VCSELs or VCSEL arrays are used, for example, as radiation sources in sensor technology or communications engineering, with VCSEL arrays being used particularly in 3D sensor systems and 3D depth cameras. VCSELs typically have a semiconductor multilayer structure in which semiconductor layers are epitaxially grown or grown on a substrate in a stacked arrangement. The substrate typically comprises a semiconducting material such as gallium arsenide (GaAs) or indium phosphide (InP). A first layer sequence of alternating, thin layers of different refractive indices, which are n-doped, for example, is grown on the substrate to form the first distributed Bragg reflector (DBR). Following the first DBR, the active zone for generating the laser radiation is grown. This can be a quantum well structure.A further layer sequence of alternating thin layers of different refractive indices, which are, for example, p-doped, is grown on the active zone to form the second distributed Bragg mirror or the second DBR.

[0008] Together with the active zone located between the two mirrors, the first and second DBRs form the laser resonator. In VCSELs, the laser light is emitted perpendicular to the surface of the VCSEL layers (i.e., in the vertical direction).

[0009] The epitaxy described above is merely an example. VCSELs can certainly have additional (epitaxy) layers. The order of the layers can vary depending on the VCSEL design and the desired properties. In particular, VCSELs often also have an oxide aperture (layer) or a current aperture (layer).

[0010] In VCSEL arrays, as mentioned above, identical VCSELs are typically arranged on the same substrate, for example, in series or as a matrix. In VCSEL arrays manufactured with good manufacturing homogeneity, the lasers within each array have very similar properties, particularly with regard to laser wavelength and polarization.

[0011] The inventors have recognized that when two VCSELs are integrated into a module with a slightly reflective interface, such as a protective cover glass, far-field interference effects can occur. The inventors have recognized that these interference effects can be attributed to spontaneous coherent coupling of the two lasers through optical feedback.

[0012] Spontaneous coherent coupling through optical feedback refers to the phenomenon in which a portion of a laser's emitted light is reflected back into the laser itself and re-enters the active region. This amount of light is referred to as optical feedback.

[0013] Optical feedback can be generated in various ways, for example, through reflections from external surfaces, especially cover glasses or transparent encapsulations of the VCSEL, or through internal reflections within the laser. This causes the reflected light in the laser's active zone to interact with the existing light fields.

[0014] Optical feedback influences and modulates the emitted light fields in the laser. If the phase relationship between the reflected light and the light already present in the laser is stable, coherent coupling can occur. This means that the reflected light coherently interferes with the already present light waves and is amplified. This creates a spatial and temporal modulation of the light fields in the laser.

[0015] Spontaneous coherent coupling through optical feedback can have various effects, including the generation of higher-order modes or the modulation of emission wavelength and intensity. In particular, an inhomogeneous far-field pattern can arise. Due to the spontaneous, chaotic nature of the interference, the position of minima and maxima is no longer predictable and therefore can no longer be compensated. Consequently, desired applications can no longer be controlled as desired. Mode competition or noise, and in particular so-called "intensity ripples," can occur, which can be particularly noticeable in the far field. The inventors have recognized that "intensity ripples" arise when the phases of the electric fields of two or more VCSELs oscillate at exactly the same frequency due to the coherent coupling, and the two fields then interfere with each other in the far field.Due to the unknown and variable path length difference from laser 1 (first VCSEL) via the structure that generates the optical feedback (e.g., protective glass) to laser 2 (second VCSEL), the phases can be shifted relative to each other or equal, but the field frequency is synchronized. This unknown and chaotic phase shift creates the "intensity ripple" for different components or different operating conditions for the same component at different positions.

[0016] To ensure the desired operating modes and properties of the VCSEL, it is therefore desirable to keep the optical feedback as low as possible and to minimize the consequences of the optical feedback.

[0017] Minimizing optical feedback itself can be achieved, for example, by using quasi-reflection-free cover glasses. However, sometimes the phenomenon cannot be completely avoided, since cover glasses, for example, cannot be designed to be reflection-free indefinitely.

[0018] Against this background, it is an object of the present invention to provide an array of vertical cavity surface-emitting semiconductor lasers, VCSELs, in which the spontaneous coherent coupling of light of the individual VCSELs is suppressed due to optical feedback.

[0019] It is a further object to provide a method for producing such a VCSEL array.

[0020] According to a first aspect of the present disclosure, a VCSEL array is proposed comprising two or more VCSELs arranged on a common semiconductor substrate. The epitaxial structure of the two or more VCSELs each comprises a first distributed Bragg mirror or Bragg reflector, DBR, an active zone, and a second distributed Bragg mirror or reflector, DBR. A first electrical contact can be provided on the first distributed Bragg mirror and a second electrical contact can be provided on the second distributed Bragg mirror. The first distributed Bragg mirror is preferably grown directly on the substrate. It consists of several (dielectric) layers that alternately have a higher or lower refractive index (relative to one another). The maximum reflectivity for a wavelength is achieved when all layers have an optical thickness of exactly one-quarter the wavelength of the respective VCSEL.The first distributed Bragg mirror is preferably n-doped. The second distributed Bragg mirror (which is grown on the active zone or located on the side of the active zone facing away from the substrate) also has several (dielectric) layers with alternating higher and lower refractive indices. For the second distributed Bragg mirror, maximum reflectivity for a wavelength is also achieved when all layers have an optical thickness of exactly one-quarter the wavelength of the respective VCSEL. The second distributed Bragg mirror is preferably p-doped.

[0021] The first electrical contact is attached to or in contact with the first distributed Bragg mirror. The first electrical contact is also called an n-type contact. The second electrical contact is attached to or in contact with the second distributed Bragg mirror. The second electrical contact is also called a p-type contact. The n-type and p-type contacts are used to supply the VCSEL with operating current.

[0022] For at least two of the two or more VCSELs, the wavelength (of the emitted laser light) differs by at least 0.003 nm and at most 5 nm.

[0023] In this respect, the laser wavelength of the (two) VCSELs of the VCSEL array is deliberately designed to differ in such a way that the probability of coherent coupling between them through optical feedback is reduced or is no longer possible. To achieve this effect, the two VCSELs must have at least slight differences in their construction (with regard to structure and / or material), in their control and / or in their arrangement on the substrate of the array. The inventors have recognized, however, that the two VCSELs preferably have an identical layer structure, as this facilitates production. Preferably, the difference between the wavelengths of the VCSELs is not too great in order not to unnecessarily increase the full spectral width of the entire array, for example when a spectral filter is used in the application.The goal is, on the one hand, to keep the full spectral width as similar to that of a perfectly symmetric array, but on the other hand to have a wavelength difference large enough to prevent coherent coupling.

[0024] A typical frequency range in which coherent coupling can occur, i.e., the so-called "locking ranges," is 1 GHz to 10 GHz, which corresponds to a wavelength difference of 0.003 nm to 0.03 nm. The goal is therefore to change the laser wavelength of the individual VCSELs or the wavelength difference between the two VCSELs by at least 0.003 nm, in particular by at least 0.01 nm, in particular by at least 0.04 nm, in particular by at least 0.1 nm.

[0025] In other words, the inventors propose deliberately inducing a wavelength difference. This approach differs from the usual production approach of minimizing wavelength variation across the wafer. A current typical scatter of 5 nm across a 4-inch wafer, however, results in a wavelength difference of only 0.005 nm at a VCSEL pitch of 50 pm and sometimes less, e.g., in the center of the wafer. For chips with lasers that are often only 30 to 40 pm apart, even the most stringent locking criteria of 1 GHz would be met if no measures were taken.

[0026] The advantage of this solution is that application-relevant properties such as the (linear) polarization of the VCSEL or VCSEL array remain unaffected. The overall spectrum width of the VCSEL array is only minimally expanded.

[0027] Another advantage is that it is an "on-chip" solution, i.e., a solution in which spontaneous coherent coupling is already suppressed by measures on the VCSELs of the VCSEL array on the chip itself. Additional components in addition to the VCSEL array (or the chip on which they are applied) are not necessary. The aforementioned differences in the wavelengths of the VCSELs in a VCSEL array virtually eliminate a common phase relationship between the light emitted by the VCSELs in the array. However, coherent coupling is dependent on a stable phase relationship. Thus, even slight wavelength differences in the nanometer or even sub-nanometer range between VCSELs in a VCSEL array can suppress coherent coupling of the light from these VCSELs.

[0028] Preferably, the VCSEL array is configured such that the wavelength of the two VCSELs differs by at least 0.003 nm and at most 4 nm, in particular by at least 0.01 nm and at most 2 nm, in particular by at least 0.04 nm and at most 0.5 nm.

[0029] It is also conceivable that the VCSEL array is configured such that the wavelengths of the two VCSELs differ by at least 0.003 nm and at most 0.1 nm, or by at least 0.003 nm and at most 0.5 nm. It is also conceivable that the wavelengths of the two VCSELs differ by at least 0.01 nm and at most 0.1 nm.

[0030] In principle, a larger wavelength difference between the two VCSELs tends to prevent spontaneous coherent coupling. On the other hand, the wavelength difference should not be chosen too large to avoid unnecessarily broadening the overall spectrum compared to two VCSELs with the same wavelength, for example, to allow the use of downstream narrowband filters, e.g., to improve the SNR (signal-to-noise ratio).

[0031] Preferably, the two VCSELs (with different wavelengths) in the VCSEL array are adjacent. Their separation is preferably 20 pm to 50 pm, particularly preferably 30 pm to 40 pm. In a preferred embodiment of the VCSEL array, the VCSEL array is configured such that the internal temperature of the two VCSELs differs by at least 0.1 K to 1 K.

[0032] The different temperatures of the VCSELs mean that the two VCSELs have slightly different emission wavelengths, even if the semiconductor layer structure is identical. An identical layer structure is particularly advantageous because it simplifies manufacturing. Depending on the internal temperature of the VCSEL, the length of the optical resonator or cavity changes due to expansion or shrinkage effects of the material used, so that the emitted wavelength of a VCSEL is temperature-dependent. Furthermore, the band structure of the semiconductors used in the VCSEL changes, which also results in a wavelength change.

[0033] The inventors have recognized that small temperature differences (in the range of a few Kelvin or even below 1 K) between VCSELs, or small temperature changes within a VCSEL within such a range, do not, or do not significantly, change the polarization characteristics of the emitted light from the VCSEL(s), so that high polarization-to-extinction ratios can still be achieved. Thus, while the aforementioned temperature difference suppresses spontaneous coherent coupling, it does not have a (negative) effect on the polarization of the VCSELs in the VCSEL array. One advantage of the proposed solution is that it still allows the use of polarization-selective elements such as polarization filters in a subsequent beam path.

[0034] Particularly preferably, the internal temperature differs by 0.1 K to 0.5 K.

[0035] Preferably, the temperature difference between the two VCSELs results from the arrangement of the VCSELs on the substrate. Preferably, the two VCSELs have the same layer structure, and the VCSEL array is configured such that the internal temperature difference between the two VCSELs results from the arrangement of the two VCSELs in the VCSEL array.

[0036] In one embodiment, the two VCSELs are designed differently with regard to their heat sinks. A heat sink can be understood as a structure that dissipates heat for the respective VCSEL.

[0037] In one embodiment of the VCSEL array, the two VCSELs are arranged non-symmetrically or asymmetrically on the substrate relative to the center of the substrate.

[0038] As a result, the heat dissipation capabilities for the two VCSELs are typically different, resulting in different internal temperatures for the two VCSELs, which in turn allows for different wavelengths of emitted light from the VCSELs.

[0039] In a preferred embodiment, one of the two VCSELs is arranged centrally on the substrate and the other of the two VCSELs is arranged at an edge of the substrate.

[0040] This leaves the VCSEL at the edge of the substrate with less space for heat dissipation, while the VCSEL placed centrally on the substrate has more space for heat dissipation. This arrangement of the VCSELs therefore results in the two VCSELs differing in their internal temperature, which in turn results in the emission of different wavelengths.

[0041] In a further embodiment, the VCSEL array comprises three VCSELs, wherein the distance between one of the two VCSELs (which differ in wavelength) and a third VCSEL differs from the distance between another of the two VCSELs and the third VCSEL.

[0042] This results in the two VCSELs having different amounts of space for heat radiation, resulting in a difference in the internal temperature. Furthermore, the third VCSEL can cause additional heat input and heat the VCSEL located closer to it more than the one further away. This, in turn, results in a difference in the emitted wavelength. Preferably, the distances differ by

[0043] According to a further embodiment of the VCSEL array, the two VCSELs each further have an oxide aperture layer with an oxide aperture, wherein the diameter of the oxide aperture of the two VCSELs differs, in particular wherein the diameter of the oxide aperture differs by at least 0.05 pm to 0.5 pm. In particular, the diameter of a mesa of the first VCSEL and the second VCSEL of the two VCSELs can differ, in particular by at least 0.05 to 0.5 pm. The difference in the oxide aperture can be achieved by a corresponding (equally large) difference in the mesa diameter. The different mesa diameter can be achieved by a targeted variation of the associated mask. With the same (lateral) oxidation depth, a different oxide aperture results from a different mesa diameter.

[0044] This then causes the two VCSELs to exhibit different temperature behavior, which in turn leads to a difference in the emitted wavelength. One advantage of this design can be that the wavelength can be adjusted in a simple, well-defined manner for one or more individual VCSELs. In particular, a controlled, slight adjustment of the wavelength is possible.

[0045] In a further embodiment of the VCSEL array, the material composition of the respective first electrical contact of the two VCSELs and / or the respective second electrical contact of the two VCSELs differs. For example, the material composition of a contact layer, in particular a (p-contact) metallization layer of the two VCSELs, differs. In particular, a different ohmic resistance is provided.

[0046] In other words, for example, the first electrical contact of one of the two VCSELs has a different material (or a different material composition) than the other of the two VCSELs. The respective second electrical contacts can also have different materials. Examples of contact materials are titanium (Ti), platinum (Pt), nickel (Ni), gold (Au), and germanium (Ge). Thus, for example, the first electrical contact of one of the two VCSELs can be made of titanium, while the first electrical contact of the other of the two VCSELs can be made of platinum. This results in different current conduction (particularly with regard to voltage and current) within the two VCSELs, so that the two VCSELs differ in terms of their wavelength.

[0047] In a preferred embodiment, the area size of the first electrical contact of the two VCSELs and / or the second electrical contact of the two VCSELs differs. In one embodiment, the area size of a layer, in particular a (p-contact) metallization layer, for contacting the two VCSELs differs. It is understood that the VCSELs can also be grown the other way around. In this case, for example, the size of an n-contact metallization layer can differ.

[0048] Similar to a different material composition, a difference in surface area also causes a different current conduction or a different electrical resistance, thus a different power loss and different heating and ultimately the emission of light of different wavelengths.

[0049] Preferably, the area of ​​said electrical contacts differs by at least 5%, more preferably by at least 20%, even more preferably by at least 50%.

[0050] This means that contact with different ohmic resistance can be provided, thus resulting in different power dissipation and different heating and ultimately the emission of light of different wavelengths.

[0051] In another embodiment of the VCSEL array, the two VCSELs are configured to be supplied with different operating currents. In another embodiment, the two VCSELs of the VCSEL array each further comprise a current aperture layer with a current aperture, wherein the distance between the first electrical contact and the current aperture layer differs between the two VCSELs and / or the distance between the second electrical contact and the current aperture layer differs between the two VCSELs.

[0052] This causes a different current flow or a different electrical resistance, thus a different power loss and different heating and ultimately the emission of light of different wavelengths.

[0053] Preferably, the epitaxial structure of the two VCSELs is identical.

[0054] According to another aspect of the present disclosure, a method for manufacturing a VCSEL array according to claim 15 is provided.

[0055] The inventive method according to claim 14 has the same advantages as the inventive VCSEL array.

[0056] According to another aspect of the present disclosure, a method is provided for operating a VCSEL array comprising two or more VCSELs, the VCSELs being arranged on a common substrate and each having an identical epitaxial structure, wherein two of the VCSELs are fed with different operating currents.

[0057] Further advantages and features can be found in the following description and the attached drawings.

[0058] It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention. Embodiments of the invention are illustrated in the drawings and will be described in more detail below with reference to them. They show:

[0059] Fig. 1 is a schematic sectional view of a VCSEL array according to the prior art;

[0060] Figs. 2A, 2B and 2C show exemplary images of interference effects due to coherent coupling;

[0061] Fig. 3 is a schematic sectional view of a first embodiment of a VCSEL array according to the present disclosure;

[0062] Fig. 4 is a schematic sectional view of a second embodiment of a VCSEL array according to the present disclosure;

[0063] Fig. 5 is a schematic sectional view of a third embodiment of a VCSEL array according to the present disclosure; and

[0064] Fig. 6 is a schematic sectional view of a fourth embodiment of a VCSEL array according to the present disclosure;

[0065] Fig. 7 is a schematic plan view of another embodiment of a VCSEL array according to the present disclosure;

[0066] Fig. 8 is a schematic plan view of another embodiment of a VCSEL array according to the present disclosure;

[0067] Fig. 9 is a schematic top view of another embodiment of a VCSEL array according to the present disclosure; Fig. 10 is a schematic top view of another embodiment of a VCSEL array according to the present disclosure.

[0068] Figures 1 and 4 to 6 show various embodiments of VCSEL arrays. It should be understood that the illustrated VCSELs and their structural features are not drawn to scale.

[0069] Fig. 1 shows a schematic sectional view of a VCSEL array 10 according to the prior art. The illustrated VCSEL array 10 comprises four VCSELs 100, 200, 300, and 400 arranged in a row, which share a first electrical contact 2 and a substrate 4. The VCSELs are identical in terms of their structure. The VCSEL array 10 is covered with a highly anti-reflection cover glass 50. Since the cover glass 50 is not completely anti-reflection, optical feedback can occur, ultimately leading to spontaneous coherent coupling of the emitted light of the individual VCSELs.

[0070] As shown in Figs. 2A to 2C, this can be clearly seen in the far field in the form of so-called "intensity ripples," as can be seen particularly in Figs. 2B and 2C. The striped intensity fluctuations are clearly visible in Figs. 2B and 2C.

[0071] Fig. 3 shows a schematic sectional view of a first embodiment of a VCSEL array 10 with a detailed view of an individual VCSEL 100. The illustrated VCSEL array 10 has four VCSELs 100, 200, 300, and 400 arranged in a row (in a dimension perpendicular to the vertical direction y), which share a first electrical contact 2 and a substrate 4. The epitaxial structure of the four VCSELs 100, 200, 300, and 400 is grown on the substrate 4. The epitaxial structure of the first VCSEL 100 is shown enlarged. As can be seen from the enlarged view, a first distributed Bragg mirror 115, an active zone 120, and a second distributed Bragg mirror 130 (in this order) are grown or arranged starting from the substrate 4. Directly above the active zone, i.e. towards the second Bragg mirror, there is an optional current aperture layer 145.A second electrical contact 135 is connected to the second distributed Bragg mirror 130. The first electrical contact 2 is mounted on the opposite side of the substrate 4. The first and second electrical contacts serve to supply the VCSEL 100 with an operating current.

[0072] The (epitaxial) layer structure of the other VCSELs 200, 300, and 400 is identical to that of VCSEL 100. However, in this embodiment, the current apertures of the current aperture layer differ. For example, the sizes of the current apertures of current aperture layers 145 and 445 differ from the current apertures of current aperture layers 245 and 345. As a result, VCSELs 100 and 400 offer a different distribution of the current flow through the VCSEL and thus a different ohmic resistance and thus a different power dissipation, which in turn leads to a difference in the internal temperature, for example, of the two VCSELs 145 and 245. With regard to the wavelength of the emitted radiation, this causes the wavelength of the VCSELs to differ (assuming that the same voltage is applied to each of the VCSELs shown).

[0073] Instead of the current aperture layers 145, 245, 345 and 445, oxide aperture layers could also be formed in the respective VCSELs, which cause a slightly different heating and thus a change in the wavelength.

[0074] In an advantageous embodiment, the differences in the current aperture layers or oxide apertures of the respective VCSELs can be created by a difference in the mesa diameter. In this case, oxidation can be carried out from the sides to the same extent or depth to form the oxide apertures. This simplifies the manufacturing process. With a mesa with a larger diameter, a larger aperture remains in the center with the same lateral oxidation than with a mesa with a smaller diameter.

[0075] In the example shown in Fig. 3, the VCSELs 200 and 300 have a slightly smaller mesa diameter than the VCSELs 100 and 400. Accordingly, the sizes of the current apertures of the current aperture layers 145 and 445 differ from the current apertures of the current aperture layers 245 and 345. The current apertures of the current apertures 245 and 345 are, corresponding to the smaller mesa diameter, slightly smaller than the current apertures of the current aperture layers 145 and 445.

[0076] Fig. 4 shows a schematic sectional view of a second embodiment of a VCSEL array 10 with two VCSELs 100 and 200. The epitaxy of the VCSELs 100 and 200 is identical. The VCSELs 100 and 200 differ only in their position on the substrate 4 in the x-direction. While the VCSEL 100 is located essentially centrally on the substrate 4 in the x-direction, the VCSEL 200 is grown at the edge of the substrate 4.

[0077] This means that the VCSEL 100 has a larger surface area available for heat dissipation compared to the VCSEL 200. The VCSEL 100 thus heats up less than the VCSEL 200, so the wavelength of the VCSEL 100 differs from that of the VCSEL 200. The arrangement is selected such that the wavelength of the VCSEL 100 and 200 differs by at least 0.003 nm and at most 5 nm.

[0078] Fig. 5 shows a schematic sectional view of a third embodiment of a VCSEL array 10 with three VCSELs 100, 200, and 300. The epitaxy of the VCSELs 100, 200, and 300 is identical. The VCSELs 100 and 200 differ only in their position on the substrate 4 in the x-direction. The VCSELs 100 and 200 are arranged significantly closer to each other in the x-direction than the VCSELs 200 and 300.

[0079] This means that, for example, the VCSEL 300 arranged further away experiences less heat input or, due to the greater distance from other VCSELs as additional heat sources, allows better heat dissipation than the VCSEL 200 and the VCSEL 100 and thus heats up less, so that the wavelength differs. The arrangement is selected such that the wavelength of the VCSELs 100 and 200 differs by at least 0.003 nm and at most 5 nm. The VCSEL array can be set up such that the wavelength of two of the VCSELs 100, 200, 300 differs by at least 0.003 nm, in particular by at least 0.01 nm, in particular by 0.03 nm, in particular by 0.04 nm, in particular by 0.1 nm. Fig. 6 shows a schematic sectional view of a fourth embodiment of a VCSEL array 10 with two VCSELs 100 and 200. The epitaxy of the VCSELs 100 and 200 is identical.However, the VCSELs 100 and 200 differ in their design, in particular in the size of their respective second electrical contacts 135 and 235. The second electrical contact 135 of the first VCSEL 100 is significantly larger in area than the second electrical contact 235 of the second VCSEL 200.

[0080] As a result, the contact offers lower electrical resistance, lower thermal dissipation, and correspondingly less heat to the VCSEL 100, allowing the desired slightly different wavelength of the first VCSEL 100 compared to the second VCSEL 200 to be achieved. Alternatively or additionally, a larger contact surface can act as a heat sink and enable improved heat dissipation, which is specifically selected to achieve the desired defined wavelength difference between the two VCSELs.

[0081] Figs. 7 to 10 show schematic top views of further embodiments of a VCSEL array with two VCSELs 100 and 200. The top view schematically illustrates the second electrical contact 135 of the first VCSEL 100 and the second electrical contact 235 of the second VCSEL 200. Further connecting lines are not shown for simplification. The schematic top views also show the mesa 150 and the active region 160 for emitting laser radiation, provided, for example, by an opening of a current aperture, of the first VCSEL 100, as well as the mesa 250 and the active region 260 of the second VCSEL 200.

[0082] In the embodiment shown in Fig. 7, the second electrical contact 235 of the second VCSEL 200 has a smaller area than the second electrical contact 135 of the first VCSEL 100. In other words, the VCSEL array is configured such that the size of the area of ​​a layer, in particular a metallization layer, for contacting the two VCSELs differs. This is implemented in a similar way in the VCSEL array shown in the schematic sectional view in Fig. 6. Furthermore, the distance of the second electrical contact 235 of the second VCSEL 200 to the active region 260 is greater than the distance of the first electrical contact 135 of the first VCSEL 100 to the active region 160. The greater distance results in a longer path and thus a somewhat higher power loss.In this way, a somewhat higher temperature of the second VCSEL 200 can be achieved in a targeted manner, but with simple process-technically speaking, whereby the VCSEL array is configured with this measure in such a way that the wavelength of two of the VCSELs differs by at least 0.003 nm and at most 5 nm.

[0083] In the embodiment shown in Fig. 8, the second electrical contact 235 of the second VCSEL 200 has a smaller area than the second electrical contact 135 of the first VCSEL 100. This allows the proposed defined wave difference between two VCSELs of the VCSEL array to be achieved. However, the distance between the second electrical contact 235 of the second VCSEL 200 and the active region 260 and the distance between the first electrical contact 135 of the first VCSEL 100 and the active region 160 can be the same.

[0084] In the embodiment shown in Fig. 9, the second electrical contact 235 of the second VCSEL 200 and the second electrical contact 135 of the first VCSEL 100 have the same area. However, the distance of the second electrical contact 235 of the second VCSEL 200 to the active region 260 is smaller than the distance of the first electrical contact 135 of the first VCSEL 100 to the active region 160. This allows the proposed defined wave difference between two VCSELs of the VCSEL array to be achieved.

[0085] In the embodiment shown in Fig. 10, the second electrical contact 235 of the second VCSEL 200 again has a smaller area than the second electrical contact 135 of the first VCSEL 100. In this embodiment, the second electrical contact 235 is part of the first electrical contact 135. Here, the second electrical contact 235 is formed, for example, as a semicircle, and the first electrical contact 135 as a full circle. This allows the proposed defined wave difference between two VCSELs of the VCSEL array to be achieved.

Claims

Claims 1. A VCSEL array comprising two or more VCSELs arranged on a common substrate and each having an epitaxial structure with a laser resonator having a first distributed Bragg reflector, DBR, an active zone, and a second distributed Bragg reflector, DBR, wherein the VCSEL array is configured such that the wavelength of two of the VCSELs differs by at least 0.003 nm and at most 5 nm.

2. VCSEL array according to claim 1, wherein the VCSEL array is configured such that the wavelength of the two VCSELs differs by at least 0.003 nm, in particular by at least 0.01 nm, in particular by 0.03 nm, in particular by 0.04 nm, in particular by 0.1 nm.

3. VCSEL array according to one of the preceding claims, wherein the VCSEL array is configured such that the wavelength of the two VCSELs differs by at least 0.003 nm and at most 4 nm, in particular by at least 0.01 nm and at most 2 nm, in particular by at least 0.04 nm and at most 0.5 nm.

4. VCSEL array according to one of the preceding claims, wherein the two VCSELs are adjacent.

5. VCSEL array according to one of the preceding claims, wherein the VCSEL array is arranged such that the internal temperature of the two VCSELs differs by at least 0.1 K to 1 K.

6. VCSEL array according to claim 5, wherein the two VCSELs have a same layer structure and the VCSEL array is configured such that the internal temperature difference of the two VCSELs results from an arrangement of the two VCSELs of the VCSEL array.

7. A VCSEL array according to any one of the preceding claims, wherein the two VCSELs are arranged asymmetrically on the substrate relative to the center of the substrate; in particular, wherein one of the two VCSELs is arranged centrally on the substrate and the other of the two VCSELs is arranged at an edge of the substrate.

8. A VCSEL array according to any one of the preceding claims, wherein the VCSEL array comprises three VCSELs, wherein the distance between one of the two VCSELs and a third VCSEL is different from the distance between another of the two VCSELs and the third VCSEL.

9. VCSEL array according to one of the preceding claims, wherein the two VCSELs each further comprise an oxide aperture layer with an oxide aperture, wherein the diameter of the oxide aperture of the two VCSELs differs, in particular wherein the diameter of the oxide aperture of the two VCSELs differs by at least 0.05 pm to 0.5 pm.

10. VCSEL array according to one of the preceding claims, wherein a material composition of a layer for contacting, in particular a p-contact metallization layer, for contacting the two VCSELs differs, in particular wherein a different ohmic resistance is provided.

11. VCSEL array according to one of the preceding claims, wherein the size of the area of ​​a layer, in particular a metallization layer, for contacting the two VCSELs differs.

12. VCSEL array according to one of the preceding claims, wherein the two VCSELs are designed to be supplied with different operating currents 13. VCSEL array according to one of the preceding claims, wherein the two VCSELs each further have a current aperture, wherein the distance between a metallization layer for contacting and the current aperture differs between the two VCSELs.

14. VCSEL array according to one of the preceding claims, wherein the epitaxial structure of the two VCSELs is identical.

15. A method for manufacturing a VCSEL array, the method comprising arranging two or more VCSELs on a common substrate, the VCSELs each having an epitaxial structure with a laser resonator having a first distributed Bragg reflector, DBR, an active region and a second distributed Bragg reflector, DBR, the VCSEL array being configured such that the wavelength of two of the VCSELs differs by at least 0.003 nm and at most 5 nm.

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