DIODE LASER AND METHOD FOR OPERATING A DIODE LASER

Abstract

The diode laser comprises a laser bar having a semiconductor body and an active layer, wherein the laser bar has a plurality of individual emitters. At least some individual emitters are respectively assigned a section of the semiconductor body and a current regulating element's connected in series therewith, such that, during operation of the individual emitters as intended, an electrical operating current I.sub.0 fed to the individual emitter in each case flows completely through the assigned section of the semiconductor body and in the process a voltage drop U.sub.H occurs at the section and at least part of said operating current I.sub.0 flows through the assigned current regulating element and experiences an electrical resistance R.sub.S in the process. In the case of the individual emitters, the current regulating element assigned in each case is configured such that the resistance Rg at an operating temperature T.sub.0 has a positive temperature coefficient dR.sub.S/dT|.sub.T0. Alternatively or additionally, the resistance R.sub.S is greater than IΔU.sub.H/I.sub.0, wherein ΔU.sub.H is the change in the voltage drop U.sub.H at the assigned section of the semiconductor body in the event of an increase in the temperature T of the individual emitter from an operating temperature T.sub.0 by 1 K.

Claims

1. A diode laser comprising: a laser bar, wherein the laser bar comprises a semiconductor body having an active layer for generating laser radiation, and wherein the laser bar comprises a plurality of individual emitters arranged side by side in a transverse direction, each of which emits laser radiation in the intended operation, one or more current control elements on the semiconductor body, wherein at least some individual emitters are each assigned a section of the semiconductor body and a current control element connected in series therewith, so that, in the intended operation of the individual emitters, in each case an operating current I.sub.0 supplied to the individual emitter flows completely through the associated section of the semiconductor body and, in the process, a voltage drop U.sub.H occurs at the section and at least part of this operating current I.sub.0 flows through the associated current control element and, in the process, experiences an electrical resistance R.sub.S, in the case of the individual emitters, the respectively associated current control element is configured in such a way that the resistance R.sub.S a) comprises a positive temperature coefficient dR.sub.S/dT|.sub.T.sub.0 at an operating temperature T.sub.0 and/or b) is greater than |ΔU.sub.H/I.sub.0|, wherein ΔU.sub.H is the change in the voltage drop U.sub.H at the associated section of the semiconductor body when the temperature T of the individual emitter is increased from an operating temperature T.sub.0 by 1 K.

2. The diode laser according to claim 1, wherein, in the intended operation of at least one individual emitter, the following applies to the resistance R.sub.S of the associated current control element: a) +0,1 mΩ/K≤dR.sub.S/dT|.sub.T.sub.0≤+20 mΩ/K and/or b) 0,5 mΩ≤R.sub.S≤100 mΩ.

3. The diode laser according to claim 1, wherein in case of a positive temperature coefficient dR.sub.S/dT|.sub.T.sub.0 applies: dR.sub.S/dT|.sub.T.sub.0≥0,5/I.sub.0.Math.dU.sub.H/dT|.sub.T.sub.0.

4. The diode laser according to claim 1, wherein, for at least one individual emitter, the associated current control element comprises or consists of a ferroelectric material.

5. The diode laser according to claim 4, wherein the ferroelectric material is a ferroelectric semiconductor ceramic.

6. The diode laser according to claim 1, wherein, for at least one individual emitter, the associated current control element is a high temperature superconductor.

7. The diode laser according to claim 1, wherein the diode laser comprises a plurality of mutually separate current control elements on the semiconductor body, wherein a plurality of individual emitters are each assigned their own current control element.

8. The diode laser according to claim 1, wherein, in the intended operation of at least one individual emitter, the part of the operating current I.sub.0 flowing within the associated current control element flows predominantly in a direction transverse or perpendicular to a main extension plane of the semiconductor body.

9. The diode laser according to claim 1, wherein, in the intended operation of at least one individual emitter, the part of the operating current I.sub.0 flowing within the associated current control element flows predominantly in a direction parallel to a main extension plane of the semiconductor body.

10. The diode laser according to claim 1, wherein, in the case of at least one individual emitter, the associated current control element is divided into a plurality of sections, the different sections each being connected in series with the section of the semiconductor body associated with the individual emitter, wherein the sections of the current control element are connected in parallel with each other, the sections of the current control element of the individual emitter are assigned to different regions of the semiconductor body, resistances R.sub.SA, R.sub.SB of different sections comprise different temperature coefficients dR.sub.SA/dT|.sub.T.sub.0, dR.sub.SB/dT|.sub.T.sub.0 at the operating temperature T.sub.0.

11. The diode laser according to claim 1, wherein the laser bar comprises a plurality of first contact elements arranged on the semiconductor body, each individual emitter is unambiguously assigned its own first contact element the associated individual emitters can be contacted via the first contact elements.

12. The diode laser according to claim 1, wherein, in the case of at least one individual emitter, a length of the associated first contact element, measured along a longitudinal direction running perpendicular to the transverse direction, is greater than a length of the current control element associated with the individual emitter.

13. The diode laser according to claim 1, wherein, in the case of at least one individual emitter, the associated current control element is a contact wire.

14. The diode laser according to claim 1, wherein, in the case of at least one individual emitter, the associated current control element is integrally and/or singly coherently formed.

15. The diode laser according to claim 1, further comprising a heat sink to which the laser bar is applied.

16. The diode laser according to claim 15, wherein, for at least one individual emitter, the associated current control element is applied to the side of the semiconductor body applied to the heat sink.

17. The diode laser according to claim 15, wherein, in the case of at least one individual emitter, the associated current control element is formed on the side of the semiconductor body facing the heat sink.

18. A method for operating a diode laser according to claim 1, wherein the individual emitters are operated in a parallel circuit, an operating current I.sub.0 flows through each individual emitter and laser radiation is thereby generated in the individual emitters, in each of the individual emitters at least part of the operating current I.sub.0 flows through the associated current control element.

19. The method according to claim 18, wherein in the case of at least one individual emitter the entire operating current I.sub.0 flows through the associated current control element.

20. A diode laser comprising: a laser bar, wherein the laser bar comprises a semiconductor body having an active layer for generating laser radiation, and wherein the laser bar comprises a plurality of individual emitters arranged side by side in a transverse direction, each of which emits laser radiation in the intended operation, one or more current control elements on the semiconductor body, wherein at least some individual emitters are each assigned a section of the semiconductor body and a current control element connected in series therewith, so that, in the intended operation of the individual emitters, in each case an operating current I.sub.0 supplied to the individual emitter flows completely through the associated section of the semiconductor body and, in the process, a voltage drop U.sub.H occurs at the section and at least part of this operating current I.sub.0 flows through the associated current control element and, in the process, experiences an electrical resistance R.sub.S, in the case of the individual emitters, the respectively associated current control element is configured in such a way that the resistance R.sub.S a) comprises a positive temperature coefficient dR.sub.S/dT|.sub.T.sub.0 at an operating temperature T.sub.0 and dR.sub.S/dT|T.sub.0≥0,5/I.sub.0.Math.dU.sub.H/dT|T.sub.0 applies and/or b) is greater than |ΔU.sub.H/I.sub.0|, wherein ΔU.sub.H is the change in the voltage drop U.sub.H at the associated section of the semiconductor body when the temperature T of the individual emitter is increased from an operating temperature T.sub.0 by 1 K.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In the following, a diode laser described herein as well as a method for operating a diode laser described herein are explained in more detail with reference to drawings by means of exemplary embodiments. Identical reference signs thereby specify identical elements in the individual figures. However, no references to scale are shown; rather, individual elements may be shown exaggeratedly large for better understanding.

[0058] Showing in:

[0059] FIGS. 1A, 1B and 3 to 11 various exemplary embodiments of a diode laser in different views,

[0060] FIGS. 2A to 2D various exemplary embodiments of a current control element in perspective view.

DETAILED DESCRIPTION

[0061] In FIG. 1A, a first exemplary embodiment of a diode laser 100 is shown in a top view of a facet of the diode laser. The diode laser 100 comprises a semiconductor body 1 having an active layer 11. Electromagnetic radiation is generated in the active layer 11 during intended operation. The semiconductor body 1 is based, for example, on InGaN.

[0062] The semiconductor body 1 comprises a first main side 10 and a second main side 12 opposite to the first main side 10. The main sides are top surfaces of the semiconductor body 1. The first main side 10 is, for example, a p-side of the semiconductor body 1. That is, holes are injected into the semiconductor body 1 via the first main side 10 during intended operation of the diode laser 100. The second main side 12 may correspondingly be the n side via which electrons are injected into the semiconductor body 1 during operation.

[0063] A plurality of metallizations 23, a plurality of current control elements 21, and a plurality of first contact elements 22 are arranged on the first main side 10 of the semiconductor body 1. Presently, the current control elements 21 are respectively arranged between the first contact elements 22 and the metallizations 23. For example, the metallizations 23 are directly adjacent to the semiconductor body 1 and serve to inject charge carriers into the semiconductor body 1. For example, the metallizations 23 are based on or consist of palladium. The first contact elements 22 may be solder contact elements, for example made of gold.

[0064] The current control elements 21 are based, for example, on platinum or a ferroelectric semiconductor ceramic or a superconducting insulator. A second contact element 24 is arranged on the second main side 12 of the semiconductor body 1. For example, the second contact element 24 is formed in a simply connected manner. For example, the second contact element 24 comprises Au and/or Ti and/or Pt.

[0065] Presently, the diode laser 100 is a laser bar having a plurality of individual emitters 2 arranged side by side in a transverse direction Q. Each individual emitter 2 is associated with a separate section 20 of the semiconductor body 1. Furthermore, a first contact element 22, a current control element 21 and a metallization 23 are biuniquely associated with each individual emitter 2. Furthermore, a section of the second contact element 24 is associated with each individual emitter 2.

[0066] In the intended operation of an individual emitter 2, an operating current I.sub.0 flows through the associated first contact element 22, the associated metallization 23, the associated section 20 of the semiconductor body 1 and the associated section of the second contact element 24, respectively. At least part of the operating current I.sub.0 flows through the associated current control element 21. The operating current I.sub.0 for an individual emitter 2 is indicated as a black arrow. For example, the operating current I.sub.0 is 2 A. At this operating current I.sub.0, the operated individual emitter 2 comprises, for example, an operating temperature T.sub.0 of 350 K.

[0067] The current control elements 21 can now each be selected such that their resistance R.sub.S is greater than |ΔU.sub.H/I.sub.0| for the part of the operating current I.sub.0 flowing through them, wherein ΔU.sub.H is the change in the voltage drop U.sub.H at the associated section 20 of the semiconductor body 1 when the temperature T of the individual emitter 2 is increased by 1 K starting from the operating temperature T.sub.0. Alternatively or additionally, the resistances R.sub.S of the current control elements 21 may each comprise a positive temperature coefficient dR.sub.S/dT|.sub.T.sub.0 at an operating temperature T.sub.0.

[0068] This embodiment of the current control elements 21 achieves homogenization of the current injected into the individual emitters 2 during intended operation, in which the individual emitters 2 are preferably operated in parallel.

[0069] In FIG. 1B, a top view of the first main side 10 is shown. The first contact elements 22 are elongated formed. Their length, measured along a longitudinal direction L, is greater than their width, measured along the transverse direction Q.

[0070] In the top view shown in FIG. 1B, the first contact elements 22 completely cover the current control elements 21 and the metallizations 23. The lengths of the current control elements 21 and the metallizations 23 may each be substantially equal to the length of the first contact elements 22.

[0071] FIGS. 2A to 2D show various exemplary embodiments of a current control element 21. Such current control elements 21 may be used in the previously shown exemplary embodiment of a diode laser 100 and in the following exemplary embodiments of a diode laser 100.

[0072] In FIG. 2A, the current control element 21 is a one-piece element.

[0073] In FIG. 2B, the current control element 21 comprises different sections 21A, 21B alternately arranged side by side. A first section 21A comprises, for example, a resistor R.sub.SA. A second section 21B comprises, for example, a resistor R.sub.SB. The resistor R.sub.SA comprises, for example, a temperature coefficient dR.sub.SA/dT|.sub.T.sub.0 at the operating temperature T.sub.0. For example, the resistor R.sub.SB comprises a temperature coefficient dR.sub.SB/dT|.sub.T.sub.0 at the operating temperature T.sub.0. For example, dR.sub.SA/dT|.sub.T.sub.0 is greater than dR.sub.SB/dT|.sub.T.sub.0. For example, sections 21A, 21B are made of different materials. The resistances R.sub.SA, R.sub.SB refer to the case of current flow through the sections 21A, 21B perpendicular to the main extension plane of the current control element 21.

[0074] With such a current control element 21, different regions of the section 20 of the semiconductor body 1 associated with an individual emitter 2 can be energized to different degrees at different temperatures.

[0075] In FIG. 2C, the current control element 21 again comprises different sections 21A, 21B arranged in a checkerboard pattern. In terms of materials and properties, these sections may also be selected as the sections of FIG. 2B.

[0076] In FIG. 2D, the current control element 21 comprises various sections 21A, 21B which are juxtaposed not only in a plane parallel to a main extension plane of the current control element 21, but also in a direction perpendicular thereto.

[0077] FIG. 3 shows a second exemplary embodiment of a diode laser 100. Unlike the exemplary embodiment of FIG. 1, a current flows through the current control element 21 predominantly in the transverse direction Q. As a result, a smaller thickness can be selected for the current control element 21 than in the exemplary embodiment of FIG. 1. In order to achieve a predominant current flow in the transverse direction Q, an insulation 25, for example of silicon nitride or silicon oxide or aluminum oxide, is also provided between the current control element 21 and the semiconductor body 1.

[0078] In the third exemplary embodiment of FIG. 4, again in the intended operation of an individual emitter 2, the current flows predominantly in the transverse direction Q through the associated current control element 21. In this case, however, two first contact elements 22 are associated with each individual emitter 2, which are separated from one another in the transverse direction Q by an insulation 25. With the embodiment shown in FIG. 4, a two-dimensional contacting of the individual emitters 2 can be established in a simplified manner.

[0079] In FIG. 5, a fourth exemplary embodiment of a diode laser 100 is shown in top view of the first main side 10 of the semiconductor body 1. The current control elements 21 comprise a shorter length than the associated first contact elements 22 and the associated metallizations 23, respectively. In particular, the current control elements 21 are each retracted from the facets of the semiconductor body 1 opposite to each other in the longitudinal direction L.

[0080] This can have an advantageous effect in the manufacture of the diode laser 100. Otherwise, the exemplary embodiment of FIG. 5 is substantially the same as the exemplary embodiment of FIG. 3.

[0081] In FIG. 6, a fifth exemplary embodiment of a diode laser 100 is shown. In this case, each individual emitter 2 is associated with its own second contact element 24 on the second main side 12. The individual second contact elements 24 are spaced apart from each other and are not connected.

[0082] Furthermore, in the FIG. 6 the current control elements 21 are formed on the sides of the second contact elements 24 facing away from the semiconductor body 1.

[0083] In addition to the laser bar, the diode laser 100 of FIG. 6 further comprises a heat sink 3 arranged on the first main side 10 of the semiconductor body 1. For example, the first contact elements 22 are soldered to the heat sink 3. The heat sink 3 may comprise or consist of SiC, AIN, Cu, CuW, for example.

[0084] Such a heat sink 3 may also be used in the previously shown exemplary embodiments.

[0085] In the sixth exemplary embodiment of FIG. 7, as in the exemplary embodiment of FIG. 6, the individual emitters 2 are each associated with their own second contact element 24 on the second main side 12. The current control elements 21 are formed on the sides of the first contact elements 22 facing away from the semiconductor body 1 between the heat sink 3 and the first contact elements 22.

[0086] FIG. 8 shows a seventh exemplary embodiment of a diode laser 100. The current control elements 21 are again arranged between the first contact elements 22 and the heat sink 3. The individual emitters 2 share a common second contact element 24 on the second main side 12.

[0087] FIG. 9 shows an eighth exemplary embodiment of a diode laser 100. Again, a heat sink 3 is formed on the first main side 10 of the semiconductor body 1. In the present embodiment, the diode laser 100 comprises only a single current control element 21 which, when viewed from above, overlaps with all of the individual emitters 2. Thus, the same current control element 21 is associated with each of the individual emitters 2. However, the different individual emitters 2 are each assigned different sections of the current control element 21. The current control element 21 is, for example, simply connected and can be formed in one piece. Preferably, the current control element 21 is segmented so that each individual emitter 2 of the laser bar can be more selectively controlled. For example, the current control element 21 may have been first applied to the heat sink 3 and then soldered to the first contact elements 22 of the laser bar.

[0088] In FIG. 10, a ninth exemplary embodiment of the diode laser 100 is shown. Here, the current control elements 21 are formed by contact wires which are connected to the second contact elements 24 of the individual emitters 2. Via the contact wires 21, the individual emitters 2 are supplied with current during intended operation. A heat sink 3 can also be used here.

[0089] FIG. 11 shows a tenth exemplary embodiment of a diode laser 100. Again, only a single current control element 21 is provided. For example, the current control element 21 is formed in a simply connected manner and may additionally be formed in a single piece. The current control element 21 is arranged on the second contact elements 24. The current control element 21 may, for example, be a metal sheet. To maximize the effectiveness of the current control element 21, the current control element 21 may be segmented.

[0090] The invention is not limited to the exemplary embodiments by the description thereof. 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 these features or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.