SEMICONDUCTOR LASER

Abstract

A semiconductor laser includes an edge-emitting laser diode, which has an active zone for generating laser radiation and a facet having a radiation exit region, and at least one photodiode. The facet is arranged on a main emission side of the laser diode. The photodiode is arranged in such a way that at least part of the laser radiation exiting at the facet reaches the photodiode. The laser diode and the photodiode are not connected to each other in a non-destructively detachable manner, and a non-destructively detachable connection is formed with a joining partner

Claims

1. A semiconductor laser comprising: an edge-emitting laser diode, which has an active zone for generating laser radiation and a facet having a radiation exit region, and at least one photodiode, wherein the facet is arranged on a main emission side of the laser diode, the photodiode is arranged in such a way that at least part of the laser radiation exiting at the facet reaches the photodiode, photodiode, and the laser diode and the photodiode are not connected to each other in a non-destructively detachable manner, and a non-destructively detachable connection is formed with a joining partner.

2. The semiconductor laser according to claim 1, in which the photodiode and the laser diode are arranged on a common carrier.

3. The semiconductor laser according to claim 1, in which the photodiode is attached to a cover of the semiconductor laser.

4. The semiconductor laser according to claim 1, in which an optical element is arranged between the laser diode and the photodiode, the optical element being configured to direct part of the laser radiation emitted by the laser diode towards the photodiode.

5. The semiconductor laser according to claim 4, in which the optical element is arranged on a carrier for the photodiode and the laser diode.

6. The semiconductor laser according to claim 4, in which the optical element is partially transmissive to the laser radiation emitted by the laser diode and is partially reflective to the laser radiation emitted by the laser diode.

7. The semiconductor laser according to claim 4, in which the optical element is configured to change the main propagation direction of at least part of the laser radiation emitted by the laser diode.

8. The semiconductor laser according to claim 1, in which the photodiode is at least locally transmissive to the laser radiation emitted by the laser diode.

9. The semiconductor laser according to claim 1, which has on a radiation exit side a cover which is partially transmissive to the laser radiation emitted by the laser diode and partially reflective to the laser radiation emitted by the laser diode.

10. The semiconductor laser according to claim 1, in which the laser diode and the photodiode are arranged in a common housing.

11. The semiconductor laser according to claim 1, in which the photodiode is a component of a carrier for the laser diode.

12. The semiconductor laser according to claim 1, in which a carrier for the laser diode comprises a recess in which the photodiode is arranged.

13. The semiconductor laser according to claim 1, in which the main extension plane of the photodiode is transverse or perpendicular to the main extension plane of the facet.

14. The semiconductor laser according to claim 1, in which the main extension plane of the photodiode is parallel to the main extension plane of the facet.

15. The semiconductor laser according to claim 1, in which an optical filter is arranged on the photodiode at least in places.

16. The semiconductor laser according to claim 1, in which a partially reflective layer is arranged on the photodiode, said partially reflective layer being configured to direct part of the laser radiation emitted by the laser diode towards the photodiode.

17. The semiconductor laser according to claim 1, in which a surface of the photodiode is uneven.

Description

[0041] In the following, the semiconductor laser described herein is explained in more detail in connection with exemplary embodiments and the associated figures.

[0042] FIG. 1 shows a schematic cross-section through a semiconductor laser according to an exemplary embodiment.

[0043] FIGS. 2, 3, 4, 5, 6, 7, 8, 9 and 10 show cross-sections through further exemplary embodiments of the semiconductor laser.

[0044] FIG. 11A shows a top view of a semiconductor laser according to another exemplary embodiment.

[0045] FIG. 11B shows a schematic cross-section through the semiconductor laser according to another exemplary embodiment.

[0046] FIG. 12 shows a top view of a photodiode according to an exemplary embodiment.

[0047] FIGS. 13A, 13B and 13C show further exemplary embodiments of the semiconductor laser.

[0048] Elements that are identical, similar or have the same effect are marked with the same reference signs in the figures. The figures and the proportions of the elements shown in the figures are not to be regarded as true to scale. Rather, individual elements may be shown exaggeratedly large for better representability and/or for better comprehensibility.

[0049] FIG. 1 shows a schematic cross-section through a semiconductor laser 20 according to an exemplary embodiment. The semiconductor laser 20 is shown without a housing 28. This means that the encapsulation of the semiconductor laser 20 is arbitrary. The semiconductor laser 20 comprises an edge-emitting laser diode 21. The laser diode 21 has an active region for generating a laser radiation and a facet 22 having a radiation exit region 23. In FIG. 1, the radiation exit region 23 is located in the upper region of the facet 22. However, it is also possible that the radiation exit region 23 is located in a different region of the facet 22.

[0050] The facet 22 is arranged on a main emission side of the laser diode 21. This means that the laser diode 21 is configured to emit laser radiation mainly on the main emission side during operation. The laser diode 21 is arranged on a connection carrier 32. The connection carrier 32 may be a so-called submount. The connection carrier 32 may comprise a semiconductor material, such as Si, SiC, Ge or GaN, or sapphire. The laser diode 21 is electrically conductively connected to the connection carrier 32. Thus, the laser diode 21 can be controlled via the connection carrier 32.

[0051] The connection carrier 32 with the laser diode 21 is arranged on a carrier 25. The connection carrier 32 may be a part of the carrier 25. The carrier 25 may include a driver that can be used to control the laser diode 21. Alternatively, the carrier 25 may be an electronically passive component and serve only as a mounting plane. The carrier 25 may comprise a semiconductor material, such as Si, SiC, Ge or GaN, or sapphire.

[0052] The semiconductor laser 20 further comprises a photodiode 24. The photodiode 24 is arranged on the carrier 25. The photodiode 24 is arranged at a distance from the laser diode 21. Since the photodiode 24 and the laser diode 21 are both arranged on the carrier 25, they are not connected to each other in a non-destructively detachable manner. The photodiode 24 has a main extension plane which is parallel to a main extension plane of the carrier 25. Furthermore, the main extension plane of the photodiode 24 is perpendicular to the main extension plane of the facet 22. Further, the photodiode 24 has a radiation entrance side 33. The photodiode 24 is configured to detect electromagnetic radiation incident on the radiation entrance side 33. The radiation entrance side 33 is arranged on the side of the photodiode 24 facing away from the carrier 25.

[0053] An optical filter 30 is optionally arranged on the photodiode 24 at the radiation entrance side 33. The filter 30 is transmissive to electromagnetic radiation in a certain wavelength range and impermeable or less transmissive to electromagnetic radiation outside that wavelength range.

[0054] In a vertical direction z, an optical element 27 is arranged above the photodiode 24 and the filter 30, the vertical direction z being perpendicular to the main extension plane of the carrier 25. Thus, the filter 30 is arranged between the optical element 27 and the photodiode 24 in the vertical direction z.

[0055] The optical element 27 has the shape of a cuboid with a beveled side surface. The optical element 27 is arranged adjacent to the laser diode 21 in a lateral direction x, the lateral direction x being parallel to the main extension plane of the carrier 25. The optical element 27 is spaced apart from the laser diode 21. Thus, the optical element 27 is arranged between the laser diode 21 and the photodiode 24. The beveled side surface of the optical element 27 is a main surface 34, and the main surface 34 faces the laser diode 21. In particular, the main surface 34 faces the facet 22.

[0056] The optical element 27 is configured to direct part of the laser radiation emitted by the laser diode 21 towards the photodiode 24. In FIG. 1, the laser radiation emerging from the laser diode 21 is shown with arrows. The main propagation direction of the laser radiation emerging at the facet 22 is parallel to the main extension plane of the carrier 25. The laser radiation emerging at the facet 22 impinges on the main surface 34 of the optical element 27. The optical element 27 is partially transmissive to the laser radiation emitted by the laser diode 21 and partially reflective to the laser radiation emitted by the laser diode 21. Thus, part of the laser radiation is reflected at the main surface 34 and deflected in the vertical direction z.

[0057] The laser radiation is reflected at the optical element 27 in a direction away from the carrier 25. Another part of the laser radiation enters the optical element 27 at the main surface 34. This laser radiation partially exits the optical element 27 again on the side facing the photodiode 24. Thus, part of the laser radiation exiting at the facet 22 reaches the photodiode 24 and can be detected there. This enables safe and reliable monitoring of the intensity of the laser radiation emerging from the laser diode 21.

[0058] The portion of the laser radiation entering the optical element 27 may be small compared to the portion of the laser radiation reflected from the optical element 27. The reflected laser radiation may exit the semiconductor laser 20 in the vertical direction z. Thus, the optical element 27 is configured to change the main propagation direction of a portion of the laser radiation emitted by the laser diode 21. The semiconductor laser 20 is a surface emitter.

[0059] To deflect part of the emitted laser radiation at the optical element 27, a partially reflective layer 31 is applied to the main surface 34. The partially reflective layer 31 may comprise a metal. The thickness of the partially reflective layer 31 is thin enough to allow part of the incident laser radiation to enter the optical element 27 through the partially reflective layer 31. The optical element 27 may comprise a transparent material, such as glass.

[0060] FIG. 2 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. The laser diode 21 and the photodiode 24 are arranged in a common housing 28. The housing 28 has a cover 26 and side walls 35.

[0061] The side walls 35 are arranged on the carrier 25 and completely surround the laser diode 21 and the photodiode 24 in lateral directions x. In the vertical direction z, the side walls 35 extend further than the optical element 27 and the laser diode 21. The cover 26 is arranged on the side walls 35. The cover 26 extends over the entire lateral extent of the carrier 25. Thus, a cavity 36 is formed between the cover 26, the side walls 35 and the carrier 25. The laser diode 21 and the photodiode 24 are arranged in the cavity 36. The cavity 36 may be hermetically sealed from the external environment.

[0062] The cover 26 is arranged on a radiation exit side of the semiconductor laser 20. This means that the laser radiation emitted by the semiconductor laser 20 exits the semiconductor laser 20 through the cover 26. Therefore, the cover 26 is at least locally transmissive to the laser radiation emitted by the laser diode 21. The laser radiation emerging from the facet 22 is shown with an arrow. At the main surface 34, part of the laser radiation is reflected in the direction of the cover 26, so that the reflected laser radiation exits the semiconductor laser 20 in the vertical direction z.

[0063] The carrier 25, on which the connection carrier 32 with the laser diode 21 is arranged, has a recess 29. The photodiode 24 is arranged in the recess 29. The optical element 27 is arranged on the carrier 25 and above the photodiode 24. Part of the laser radiation incident on the main surface 34 passes through the optical element 27 to the photodiode 24, where it can be detected. Since the photodiode 24 is arranged in the recess 29, the semiconductor laser 20 can have a compact shape.

[0064] FIG. 3 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 2, the carrier 25 does not have a recess 29. The photodiode 24 is arranged on the carrier 25. Here, the main extension plane of the photodiode 24 is parallel to the main extension plane of the facet 22. The optical element 27 is arranged between the laser diode 21 and the photodiode 24. The photodiode 24 is adjacent to a side surface of the optical element 27 which extends perpendicular to the main extension plane of the carrier 25. The photodiode 24 is adjacent to the side surface of the optical element 27 which faces away from the main surface 34. It is shown with an arrow that part of the laser radiation incident on the main surface 34 passes through the optical element 27 to the photodiode 24. In this case, the laser radiation incident on the photodiode 24 has the same main propagation direction as the laser radiation emerging from the facet 22. This exemplary embodiment of the semiconductor laser 20, too, can have a particularly compact design.

[0065] FIG. 4 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. In this exemplary embodiment, the encapsulation of the semiconductor laser 20 is arbitrary. Compared to the exemplary embodiment shown in FIG. 1, the photodiode 24 is arranged in the carrier 25. Thus, the photodiode 24 is an integral part of the carrier 25. The carrier 25 may comprise a semiconductor material such as Si, Ge, or SiC. As explained in connection with FIG. 1, part of the laser radiation emitted at the facet 22 passes through the optical element 27 to the photodiode 24. The partially reflective layer 31 is shown separately in this exemplary embodiment and completely covers the main surface 34.

[0066] FIG. 5 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 1, the semiconductor laser 20 comprises no optical element 27. The photodiode 24 is arranged on the carrier 25 at a distance from the laser diode 21. The main extension plane of the photodiode 24 is transverse or oblique to the main extension plane of the facet 22. Furthermore, the main extension plane of the photodiode 24 is transverse or oblique to the main extension plane of the carrier 25.

[0067] A partially reflective layer 31 is arranged on the radiation entrance side 33 of the photodiode 24. The partially reflective layer 31 is partially transmissive to the laser radiation emitted by the laser diode 21 and partially reflective to the laser radiation emitted by the laser diode 21. This means that the partially reflective layer 31 is configured to direct part of the laser radiation emitted by the laser diode 21 towards the photodiode 24. Another part of the laser radiation emitted by the laser diode 21 is reflected by the partially reflective layer 31 and exits the semiconductor laser 20 in the vertical direction z. The partially reflective layer 31 may be constructed like a partially reflective layer 31 arranged on the optical element 27. Optionally, an optical filter 30 is also arranged on the radiation entrance side 33.

[0068] FIG. 6 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 1, the photodiode 24 is arranged between the laser diode 21 and the optical element 27. The photodiode 24 is arranged on the carrier 25. Furthermore, the photodiode 24 is arranged at a distance from the laser diode 21 and at a distance from the optical element 27. Laser radiation emerging at the facet 22 impinges on the photodiode 24, with the photodiode 24 being arranged in the direction of the main emission direction of the emerging laser radiation. Thus, all or most of the laser radiation emerging from the facet 22 impinges on the photodiode 24. This enables accurate determination of the intensity of the laser radiation emerging from the laser diode 21 with an improved signal-to-noise ratio.

[0069] The photodiode 24 is at least locally transmissive to the laser radiation emitted by the laser diode 21. Thus, the emitted laser radiation passes through the photodiode 24 to the optical element 27. At the main surface 34, the laser radiation is deflected in the vertical direction z. At the main surface 34, the optical element 27 is reflective to the laser radiation. This means that the reflectivity of the main surface 34 for the incident laser radiation is, for example, at least 90% or at least 95%.

[0070] The photodiode 24 may comprise SiC or sapphire. A further optical element 39 is optionally arranged on the radiation entrance side 33 of the photodiode 24. The further optical element 39 is configured to beam-shape the laser radiation exiting the facet 22. For example, the further optical element 39 is configured to focus the laser radiation exiting the facet 22 onto the photodiode 24.

[0071] FIG. 7 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 2, the photodiode 24 is attached to the cover 26 of the semiconductor laser 20. The cover 26 or a portion of the cover 26 may be a growth substrate for the photodiode 24. The growth substrate may comprise sapphire or SiC. Further, the photodiode 24 is at least locally transmissive to the laser radiation emitted by the laser diode 21. An electrical contact 37 is arranged in one of the side walls 35 and in places on the cover 26 for electrically contacting the photodiode 24. Thus, the photodiode 24 can be controlled via the carrier 25. The optical element 27 has a high reflectivity at the main surface 34 for the laser radiation emitted by the laser diode 21. For example, the reflectivity of the main surface 34 is at least 90% or at least 95% for the laser radiation emitted by the laser diode 21.

[0072] Thus, most of the laser radiation exiting the facet 22 is reflected off the main surface 34 towards the cover 26. The photodiode 24 is attached to the cover 26 in the area where a majority of the reflected laser radiation impinges on the cover 26. Thus, all or most of the emitted laser radiation impinges on the photodiode 24, which increases the accuracy of the measurement of the intensity of the emitted laser radiation. The emitted laser radiation exits the semiconductor laser 20 through the photodiode 24 and the cover 26.

[0073] FIG. 8 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 7, the photodiode 24 is not attached to the cover 26, but is arranged on the carrier 25. The photodiode 24 is arranged adjacent to the optical element 27, so that the optical element 27 is arranged between the laser diode 21 and the photodiode 24. The cover 26 is partially transmissive to the laser radiation emitted by the laser diode 21. This means that part of the laser radiation reflected off the main surface 34 exits the semiconductor laser 20 through the cover 26 in the vertical direction z. Part of the laser radiation incident on the main surface 34 is scattered at the main surface 34 and reaches the photodiode 24 via total reflection at the cover 26. The main extension plane of the photodiode 24 is parallel to the main extension plane of the carrier 25. The portion of the laser radiation which exits the semiconductor laser 20 through the cover 26 is substantially larger than the portion of the laser radiation which is scattered at the main surface 34.

[0074] Optionally, a partially reflective layer 31 is arranged on the cover 26, said partially reflective layer having a very low reflectivity and a high transmissivity for the emitted laser radiation. This means that a small portion of the laser radiation is reflected at the partially reflective layer 31 and can reach the photodiode 24. The majority of the laser radiation incident on the partially reflective layer 31 exits the semiconductor laser 20 through the partially reflective layer 31 and the cover 26. This exemplary embodiment allows for a compact design of the semiconductor laser 20.

[0075] FIG. 9 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 7, the photodiode 24 is not arranged along the main propagation direction of the laser radiation. Arrows indicate that the main propagation direction of the laser radiation reflected at the main surface 34 is in the vertical direction z. The reflected laser radiation exits the semiconductor laser 20 through the cover 26. The photodiode 24 is attached to the cover 26 and is located adjacent to the area where a majority of the emitted laser radiation exits the semiconductor laser 20 through the cover 26. The photodiode 24 is not necessarily transmissive to the laser radiation. A small portion of the laser radiation incident on the main surface 34 is scattered in other directions. In addition, the laser beam exhibits some divergence. Thus, part of the laser radiation reaches the photodiode 24 and is detected there.

[0076] FIG. 10 shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 1, the photodiode 24 is arranged in the connection carrier 32. Here, the photodiode 24 is arranged on the side of the facet 22 in the connection carrier 32. The optical element 27 has a high reflectivity for the emitted laser radiation. Laser radiation incident on the optical element 27 is deflected in the vertical direction z. The photodiode 24 is configured to detect scattered light of the laser radiation emerging from the facet 22. Thus, the laser radiation emerging from the laser diode 21 can be directly monitored by the photodiode 24.

[0077] FIG. 11A shows a top view of another exemplary embodiment of the semiconductor laser 20. The semiconductor laser 20 comprises three laser diodes 21. The laser diodes 21 are arranged on the connection carrier 32, which is arranged on the carrier 25. The main emission directions of the laser diodes 21 are parallel to each other. Furthermore, the optical element 27 is arranged at a distance from the laser diodes 21 on the carrier 25. The optical element 27 is arranged such that the laser radiation emitted from each of the laser diodes 21 at the facet 22 is incident on the main surface 34. Further, the semiconductor laser 20 comprises two photodiodes 24. Each of the photodiodes 24 is arranged between two respective laser diodes 21 in the lateral direction x. The photodiodes 24 may be arranged on the connection carrier 32, on the carrier 25 or in the carrier 25.

[0078] An optical filter 30 is arranged on one of the two photodiodes 24. No optical filter 30 is arranged on the other photodiode 24. The optical filter 30 is transmissive to the laser radiation emitted by the laser diodes 21. Electromagnetic radiation in other wavelength ranges is largely absorbed by the optical filter 30. By comparing the radiation detected by the two photodiodes 24, the proportion of background radiation and scattered light can be determined. Thus, the signal-to-noise ratio of the detected laser radiation can be improved.

[0079] FIG. 11B shows a schematic cross-section through the exemplary embodiment of the semiconductor laser 20 shown in FIG. 11A. A partially reflective layer 31 is arranged on the side of the cover 26 facing the carrier 25. A small portion of the laser radiation emitted from the laser diodes 21 is reflected at the partially reflective layer 31. Thus, part of the laser radiation reaches the photodiodes 24. The cover 26 is at least in places transmissive to the radiation emitted by the laser diodes 21. The radiation entrance side 33 of the photodiodes 24 is arranged on the side of the photodiodes 24 facing away from the carrier 25.

[0080] FIG. 12 shows a top view of an exemplary embodiment of a photodiode 24. The photodiode 24 is the photodiode 24 of the exemplary embodiment shown in FIGS. 11A and 11B, on which the optical filter 30 is arranged. The filter 30 has three different filter regions 38. In addition, the photodiode 24 has three segments. One filter region 38 is arranged above each of the segments. One of the laser diodes 21 is associated with each of the filter regions 38. The filter regions 38 are transmissive to the laser radiation emitted by the associated laser diode 21 and impermeable to other wavelength ranges. For example, one of the filter regions 38 is transmissive to red light, one of the filter regions 38 is transmissive to blue light, and one of the filter regions 38 is transmissive to green light. The photodiode 24 further comprises two electrical contacts 37 for electrically contacting the photodiode 24.

[0081] As an alternative to the exemplary embodiment shown in FIG. 12, the semiconductor laser 20 of the exemplary embodiment shown in FIGS. 11A and 11B may comprise a total of four photodiodes 24. In this case, an optical filter 30 is disposed on each of three of the photodiodes 24. Each of the optical filters 30 is associated with one of the laser diodes 21 as described above. No optical filter 30 is arranged on the fourth photodiode 24.

[0082] FIG. 13A shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 5, the photodiode 24 has an uneven or curved surface. Here, the curved surface faces the facet 22 of the laser diode 21. The partially transparent layer 31 arranged on the surface of the photodiode 24 also has a curved shape. Overall, the surface of the photodiode 24 has a concave shape. This means that the surface of the photodiode 24 is curved inward. Thus, the surface of the photodiode 24 with the partially transparent layer 31 serves for beam deflection and beam shaping of the laser radiation emitted by the laser diode 21. The photodiode 24 has an active region 40 which is configured to detect electromagnetic radiation during operation of the photodiode 24. The active region 40 extends parallel to the curved surface of the photodiode 24.

[0083] FIG. 13B shows a top view of a portion of the photodiode 24 shown in FIG. 13A. The cross-section shown in FIG. 13A is along the dashed line. The photodiode 24 is arranged on the carrier 25. In the top view, the curvature of the surface is shown to be circular.

[0084] FIG. 13C shows a schematic cross-section through another exemplary embodiment of the semiconductor laser 20. Compared to the exemplary embodiment shown in FIG. 13A, the active region 40 of the photodiode 24 extends parallel to the main extension plane of the photodiode 24.

[0085] This patent application claims the priority of German patent application 102018128751.8, the disclosure content of which is hereby incorporated by reference.

[0086] The invention is not limited to the exemplary embodiments by the description based on the same. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.

LIST OF REFERENCE SIGNS

[0087] 20: semiconductor laser [0088] 21: laser diode [0089] 22: facet [0090] 23: radiation exit region [0091] 24: photodiode [0092] 25: carrier [0093] 26: cover [0094] 27: optical element [0095] 28: housing [0096] 29: recess [0097] 30: filter [0098] 31: partially reflective layer [0099] 32: connection carrier [0100] 33: radiation entrance side [0101] 34: main surface [0102] 35: side walls [0103] 36: cavity [0104] 37: electrical contact [0105] 38: filter region [0106] 39: further optical element [0107] 40: active region [0108] x: lateral direction [0109] z: vertical direction