WO2013060534A2

WO2013060534A2 - Laser light source

Info

Publication number: WO2013060534A2
Application number: PCT/EP2012/068479
Authority: WO
Inventors: Hans-Jochen Schwarz; Joern Ostrinsky
Original assignee: Robert Bosch Gmbh
Priority date: 2011-10-27
Filing date: 2012-09-20
Publication date: 2013-05-02
Also published as: WO2013060534A3; DE102011085344A1; DE102011085344B4

Abstract

The invention relates to a laser light source (100) comprising a plurality of surface emitters (200, 200a, 200b,...) which are arranged on a substrate element (300). The invention is characterized in that different surface emitters (200a, 200b) are each designed and/or arranged relative to one another on the substrate element (300) such that main beam directions (H1, H2) of the laser radiation emitted from said emitters are not parallel to one another and/or such that a packing density which describes a distance from a first surface emitter (200c) to at least one surface emitter (200d) that is adjacent to the first surface emitter in at least one dimension is not constant.

Description

Description title

Laser light source prior art

The invention relates to a laser light source having a plurality of surface emitters arranged on a carrier element.

It is already known to produce laser light sources with a plurality of identically designed surface emitters, which are arranged, for example, on a common substrate or carrier element. This results in an aggregated field characteristic, in particular far field characteristic, for the laser radiation generated by the laser light source, which differs from the

Field characteristics of the individual surface emitter depends, and the disadvantage is only limited adaptable to a target system.

Disclosure of the invention

It is an object of the present invention to improve a laser light source of the type mentioned in that a resulting

Field characteristic of the laser light source is better adapted to the intended use of the laser light source.

This object is achieved in the laser light source of the type mentioned in the present invention that different surface emitter are each formed and / or arranged relative to each other on the support member, that main beam directions of the laser radiation emitted by them are not parallel to each other, and / or a packing density which is a distance of a first surface emitter to at least one adjacent thereto

Surface emitter in at least one dimension describes, is not constant.

In this way, there is advantageously the possibility of the field characteristic of the laser radiation resulting during operation of the laser light source, which results from a superimposition of the field characteristics of the individual

Surface emitter results to be changed so as to give a desired shape for the resulting field characteristic. In particular, the resulting field characteristic of the laser light source can thereby be optimally adapted to the respective intended use of the laser light source.

In an advantageous embodiment, it is provided that at least two surface emitters are formed so that they each have a different field characteristic, in particular far field characteristic, whereby a further degree of freedom to achieve a desired resulting

Field characteristic, in particular far field characteristic, is given for the laser light source.

In a further advantageous embodiment, it is provided that at least two surface emitters differ from one another with regard to at least one of the following features: a. Training, in particular opening area and / or opening shape of a Stromapertur,

b. Arrangement of a current aperture relative to a current contact in the region of a coupling-out mirror of the surface emitter, c. Form and / or orientation of a current contact to supply the surface emitter with electrical energy, d. Number of power contacts to supply the

Surface emitter with electrical energy.

In a further advantageous embodiment, it is provided that at least one surface emitter is arranged on the carrier element such that an optical axis of the surface emitter is not parallel to an optical axis of at least one further arranged on the carrier element Surface emitter, in particular a predetermined angle with the optical axis of the at least one further surface emitter includes.

In a further advantageous embodiment, it is provided that at least one surface emitter has a microlens for influencing the laser radiation generated by the surface emitter, in particular for influencing the main radiation direction of the field characteristic of the laser radiation generated. In a further advantageous embodiment it is provided that several

At least two microlenses each have different optical properties and / or a different orientation with respect to their respective associated surface emitter.

In a further advantageous embodiment, it is provided that different surface emitters are each designed as a vertical cavity surface emitting laser, VCSEL, or as a vertical external cavity surface emitting laser, VECSEL.

In a further advantageous embodiment, a laser ignition system for an internal combustion engine, in particular a motor vehicle or a stationary motor, proposed with a solid-state laser for generating laser ignition pulses and with at least one inventive

Laser light source for providing laser radiation for optical pumping of the solid-state laser.

In a further advantageous embodiment it is provided that a pumping optics is provided, which is designed to shape the radiation emitted by the laser light source, in particular to focus on the solid-state laser.

In a further advantageous embodiment, it is provided that the pumping optics at least one optical element with regions

different optical properties, in particular different

Focal length, has. In a further advantageous embodiment, it is provided that the at least one optical element is, for example, a radially or circularly segmented lens with a partially different surface curvature or a free-form element.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features alone or in any combination form the subject matter of the invention, regardless of their

Summary in the claims or their dependency and regardless of their formulation or representation in the description or in the drawing.

In the drawing shows:

FIG. 1 shows a schematic side view of a first embodiment of a laser light source according to the invention,

FIG. 2a,

2b, 2c schematically each show a plan view of further embodiments of the invention, each with a different packing density of

Surface emitters,

FIG. 3 schematically shows a side view of a further embodiment of the invention;

Figure 4 schematically shows a greatly enlarged cross-section of a

Surface emitter according to a further embodiment,

FIG. 5a,

FIG. 5 b schematically shows a respective far-field characteristic as represented by

different configurations of the emitter according to FIG. 4 can be obtained,

FIG. 6 shows a schematic side view of a laser ignition system according to an embodiment, FIG. 7a,

FIG. 7b schematically shows a cross section of a further embodiment of a surface emitter in different operating states, FIG.

FIG. 8a,

8b schematically each show a far-field characteristic of the embodiments according to FIGS. 7a, 7b,

9 shows schematically a side view of a further embodiment of the invention, and

Figure 10 shows schematically a side view of yet another embodiment of the invention.

FIG. 1 schematically shows a side view of a first embodiment of the laser light source 100 according to the invention. The laser light source 100 has a carrier element 300 formed, for example, as a common substrate, on which, as shown in FIG. 1, a plurality of surface emitters 200a, 200b, 200c are arranged. The surface emitters 200a, 200b, 200c are surface-emitting semiconductor diode lasers, the basic function and structure of which are known per se to a person skilled in the art.

In the operation of the laser light source 100, all are preferred

Surface emitter 200a, 200b, 200c simultaneously or at least partially timed overlapping to generate laser radiation. This results in a superposition of the field characteristics of the individual

Surface emitter such that for the laser light source 100 a total of field characteristics of the laser radiation generated is obtained, which is dependent inter alia on the field characteristics of the individual surface emitter and their arrangement on the support member 300.

According to the invention, different surface emitters 200a, 200b are each designed in such a way that main beam directions H1, H2 of the laser radiation emitted by them are not parallel to one another. This advantageously results in a degree of freedom in the synthesis of one of the

Laser light source 100 to be generated radiation field. Under the In the present case, the main beam direction is that spatial direction in which the optical power radiated by a surface emitter has an absolute maximum ("main lobe").

It is also conceivable to form surface emitters in such a way that they form two or more main lobes of approximately the same size. In this case, the main radiation direction is understood to be an angle between one of the main lobes and a surface normal of a coupling-out mirror of the surface emitter.

For surface emitters which are essentially donut-shaped

Field characteristic (approximately circular intensity distribution in a plane orthogonal to the optical axis of the surface emitter), is understood by the main beam direction in the context of the present invention, the optical axis.

Compared to conventional, also known as VCSEL array

Laser light sources, where a variety of identically designed and

arranged emitter is provided, the laser light source 100 according to Figure 1 has the advantage that one or more surface emitter 200a, 200b, 200c each have different main beam directions H1, H2, H3 for the laser radiation generated by them, whereby the resulting field characteristic of the laser light source 100 total emitted laser radiation can be influenced within wide limits and thus optimally adapted to a target system.

In the configuration depicted in FIG. 1, the laser light source 100 has, for example, a total of four surface emitters of the type 200a, whose main radiation direction H1 is in each case substantially orthogonal to a surface of the carrier element 300. Furthermore, two surface emitters 200b are provided, the main radiation direction H2 of which in each case encloses an acute angle with the main radiation direction H 1 of the first surface emitter type 200a. The same applies to the third type of surface emitter 200c with the

Main beam direction H3.

By suitable arrangement of the surface emitter 200a, 200b, 200c on the carrier element 300 and further suitable selection of the corresponding

Main beam direction H1, H2, H3 may be the resulting field characteristic of Laser radiation of the laser light source 100 can be influenced within wide limits. For example, numerical simulations can be used to simulate a multiplicity of different configurations of surface emitters 200a, 200b, 200c on the carrier element 300, each with different main beam directions H 1, H 2, H 3, and simulate them with respect to an objective function, for example a desired resulting field characteristic of the laser radiation one or more configurations can be obtained which satisfy the given requirements, for example a homogeneity of the far field characteristic over a predefinable solid angle range.

FIG. 2 a schematically shows a plan view of a laser light source 100 according to a further embodiment. In this embodiment, the surface emitters of the laser light source 100, symbolized here as a circle, have a non-constant packing density. That means not all

Surface emitters each have an equal distance to their adjacent surface emitters.

In FIG. 2a, a horizontal location coordinate with the reference symbol x and a vertical location coordinate with the reference symbol y are defined. In the present case, along the vertical spatial coordinate y, all surface emitters have the same distance to their neighbors. This means that the horizontal rows of surface emitters depicted in FIG. 2a each have an identical spacing d3 from one another.

In contrast, a distance between surface emitters adjacent along the x-coordinate is not constant over the entire carrier element 300.

Instead, a surface emitter 200d of the surface emitter 200c arranged on the top left in FIG. 2a has a horizontal distance d1 which is greater than the horizontal distance d2 between the surface emitter 200d and a further surface emitter 200d 'adjacent to the right in FIG. 2a. A distance between the surface emitter 200d 'and a further surface emitter 200d "is again d2, whereas a further distance between the surface emitter 200d" and a surface emitter d1, which is arranged to the right thereof in FIG. 2a, is d1. In summary, therefore, in FIG. 2a, three middle columns of

Surface emitters with each other on a relatively small distance d2 in the horizontal direction, while the outer columns each have a greater distance d1 to the respective adjacent inner column.

Due to this non-constant packing density of the individual surface emitters on the carrier element 300, a further degree of freedom is preferred in achieving a desired resulting field characteristic for the

Laser radiation of the laser light source 100 given. For example, all the surface emitters of the laser light source 100 according to FIG. 2a can be designed identically, and the shaping of the resulting field characteristic takes place solely by influencing the packing density.

Alternatively, surface emitters of different types may be used and combined with a non-constant packing density.

FIG. 2b shows a further embodiment of the invention in which a plurality of rows or columns of surface emitters 200e, 200f are again provided.

In the present case, all surface emitters in the horizontal direction (x-coordinate) have the same distance d4, while the different

Emitter rows different distances d5, d6, as shown in Figure 2b, have. This means that in contrast to the embodiment according to FIG. 2a, the packing density in the embodiment according to FIG. 2b varies in the vertical direction (y-coordinate).

The outer surface emitters 200e of the embodiment according to FIG. 2b accordingly have a greater vertical distance d5 from them

adjacent inner surface emitters 200f, which have a smaller distance d6 between them.

Figure 2c shows a further embodiment of the invention, in which the

Packing density is not constant along the x coordinate as well as along the y coordinate over the carrier element 300. The distribution pattern of the individual, in Figure 2c for clarity, unspecified surface emitter, for example, as

rectangular arrangement of three times three inner surface emitters are considered, which have an adjacent distance of d7 in both the horizontal and in the vertical direction with each other.

Arranged around this inner emitter group is an outer emitter group which extends along the edge of the carrier element 300 and whose emitters have a neighboring distance d8 between them. Furthermore, the outer surface emitters in FIG. 2c also have a neighboring distance d8 to the inner emitter group.

Other configurations for a non-constant packing density are also conceivable, in particular rotationally symmetrical arrangements or

Having circular ring geometry emitter groups and the like.

FIG. 3 shows schematically a side view of a further embodiment of the invention. On a support member 300 a plurality of surface emitter 200g, 200h, 200i are arranged.

As is apparent from FIG. 3, the surface emitters of the type 200g are arranged relative to the carrier element 300 and arranged thereon so that their optical axis OA is substantially perpendicular to a surface of the carrier element 300, ie parallel to the surface normal (not shown) of the carrier element 300 stands.

In contrast to this, the surface emitters 200h, 200i are oriented with respect to the carrier element 300 such that their optical axes OA ', OA "are not parallel to the surface normal of the carrier element 300. Advantageously, a further influencing of the resulting field characteristic of the laser light source 100 can be effected ,

The different emitters 200g, 200h, 200i according to FIG. 3 can advantageously also have the same design parameters, but be aligned on the carrier element 300 by individual mounting such that their respective optical axes OA, OA ', OA2' satisfy the abovementioned criteria. Alternatively or additionally, the surface emitters 200g, 200h, 200i may also constructively designed differently, for example, to each cause different field characteristics of the laser radiation generated by them, whereby further combination possibilities or degrees of freedom for obtaining a resulting field characteristic of the laser light source 100 are given.

The embodiment according to FIG. 3 has different effects

mechanical alignment of the individual surface emitter 200g, 200h, 200i, respectively, the acquisition of different main beam directions for the laser radiation generated by the individual surface emitters. In that regard, a similar effect arises, as in the embodiment described with reference to Figure 1, in which also different main beam directions H 1, H2, H3 are given. In contrast to the configuration according to FIG. 1, however, the different main beam directions in the configuration according to FIG. 3 are generated primarily via the mechanical alignment of the individual surface emitter with respect to the carrier element 300 and other emitters arranged thereon. Additionally, if necessary, by

Use of different emitter types, as already mentioned above, a further influence on the main beam directions of the output from the individual emitters laser radiation.

FIG. 4 schematically shows an enlarged cross section of a

Surface emitter 200, as it can be used for the formation of the laser light source 100 of the invention (Figure 1). The surface emitter 200 has a first mirror layer 202, which may be, for example, a distributed Bragg reflector (DBR), that is to say a layer sequence of substrate layers, each having a different refractive index, formed in a vertical direction in FIG. A Auskoppelspiegelschicht 204 is also formed as a DBR and includes, together with the first mirror layer 202, an active region 206 of the surface emitter 200, for example, a

Quantum film 208 or other suitable elements, such as

Quantum dots, quantum wires may have to generate

Laser radiation.

A current density distribution in the region of the coupling-out mirror 204 and in the region of the active zone 206 can be influenced by a current diaphragm 210. In particular, through the opening width 210 a or Opening surface of the current diaphragm 210 a Stromapertur 210b are defined, which substantially the field characteristics, in particular

Far field characteristic of the surface emitter 200 and the laser radiation generated therefrom L controls.

A current contact 212 is on the upper surface in FIG

Auskoppelspiegel provided 204 and serves to supply the

Surface emitter 200 with electrical energy. Also in FIG. 4

indicated is a control device 400, which supplies the surface emitter 200 by means of a drive signal A with electrical energy to put the surface emitter 200 in an active state in which it generates the laser radiation L. Another power contact is not shown in FIG. 4, but may for example be provided between the components 202, 300 and also connected to the controller 400 to close a circuit between the controller 400 and the surface emitter 200.

The surface emitter 200 may be arranged on a surface of the carrier element 300 in the manner illustrated schematically in FIG. 4, as can further surface emitters 200 not shown in FIG.

According to a further embodiment it is provided that in the

Laser light source 100 at least two surface emitter 200 differ from each other with regard to at least one of the following features: a training, in particular opening area and / or opening shape of the current aperture 21 Ob,

b arrangement of the current aperture 200b relative to the current contact 212 in the region of a coupling-out mirror 204 of the surface emitter 200, c shape and / or orientation of a current contact 212 for supplying the surface emitter 200 with electrical energy,

d number of power contacts 212 to supply the

Surface emitter 200 with electrical energy.

The above features may be used individually or in combination with each other, differently configured Surface emitter 200 to provide, for example, one of its optical axis (normal to the Auskoppelspiegelfläche 204) deviating main beam direction of the laser radiation generated L have.

Such surface emitter types can be combined with one another according to the invention in order to form the laser light source 100. Alternatively or additionally, a non-constant packing density or a mechanical alignment of the individual surface emitters with respect to the common carrier element 200 can also be used.

FIG. 5a shows, by way of example, a first far-field characteristic FFC1 in the form of an optical power P of the laser radiation L (FIG. 4) plotted against an unspecified number, which extends in the horizontal direction in FIG. 5 and represents the angular coordinate. This first far-field characteristic FFC1 can be achieved, for example, by a first configuration of a surface emitter 200 (FIG. 4) by means of the abovementioned measures a to d.

By a modification of the shape of the current aperture 210b (FIG. 4), for example, another far-field characteristic FFC2, as illustrated by way of example in FIG. 5b, can be realized.

Although the current aperture 210b is preferably formed in approximately circular or oval, according to a further advantageous embodiment, the current aperture also substantially slot-shaped, that is rectangular, are formed with an aspect ratio of width to height greater than 2: 1, whereby a division of field characteristics the laser radiation L of the surface emitter 200 is possible from a single main lobe to two main lobes arranged symmetrically about the optical axis.

Depending on the aspect ratio of the slit-shaped current aperture, the main beam direction (angle between the main lobe and the optical axis of the surface emitter) can be influenced, in order in turn to provide different surface emitter 200 types.

FIG. 6 shows components of a laser ignition device 1000, as they are

For example, for an internal combustion engine of a motor vehicle or a stationary large gas engine or the like can be used. The Laser ignition device 1000 has at least one laser light source 100 according to the present invention and a solid state laser 600, which is optically pumped by means of the laser control device L1 generated by the laser light source 100. In the present case, a configuration for the longitudinal optical pumping is shown, in which the pump radiation L1 in the left in Figure 6 end face 602 of the im

Essentially circular-cylindrical solid-state laser 600 is irradiated. Upon application of the pump radiation L1 generates the

Solid-state laser 600 in a conventional manner high-energy laser ignition pulses LZ.

From Figure 6 it can be seen that the laser light source 100 in turn

different surface emitters 200a, 200b, each having different far field characteristics FFC1, FFC2, to obtain a resultant

Field characteristic, in particular far field characteristic, for the pump radiation to achieve L1. Thereby, e.g. a very homogeneous pumping profile 604 are generated (constant optical power over the end face 604), which has a positive effect on the beam quality of the laser ignition pulses LZ and the efficiency in the optical pumping of the solid-state laser 600. By the measures according to the invention described above u.a. the main radiation direction HR of the generated laser radiation L1 and / or its distribution, e.g. over a predeterminable solid angle Ω, be set within wide limits. Optionally, also in Figure 6 between the solid state laser 600 and the

Laser light source 100 pictured pumping optics 500 may be provided, which may be, for example, an optical element with partially different optical properties, in particular different focal length. These different areas can, for example, segmentally or annularly different in the radial direction over the optical

Be distributed element.

In a further advantageous embodiment, it is provided that the at least one optical element has a radially or circularly segmented lens with regions of different surface curvature or a

Freeform element is. FIG. 7a shows a further embodiment of a surface emitter which in the present case has two current contacts 212a, 212b, which are spaced apart from the current stop 210 by the distances d3 ', d4'. In FIG. 7a, only the first current contact 212a is acted upon by the control device 400 by means of the drive signal A1, so that a first current density distribution results in the emitter in the operating state according to FIG. 7a. This operating state corresponds to the far field characteristic FFC5 schematically illustrated in FIG. 8a.

In a second operating state, which is illustrated in FIG. 7b, only the second current contact 212b is acted upon by the control device 400 with a further drive signal A2, whereby one of the

Configuration according to Figure 7a deviating current density distribution in the surface emitter, in particular in its active zone 206 results. As a result, another far field characteristic FFC6 (FIG. 8b) is achieved.

By choosing a suitable operating state, Figure 7a, Figure 7b, therefore even dynamically, that is, during operation of the laser light source 100 (Figure 1) a far field characteristic FFC5, FFC6 individual surface emitter can be changed, so that a further increased flexibility in achieving a desired resulting field characteristic of the laser light source 100 is given.

FIG. 9 shows a further embodiment of the invention in a schematic side view. On the support member 300, a plurality of surface emitters 200j are juxtaposed. Each surface emitter is a microlens

2020, which is designed to shape the laser radiation L (FIG. 4) generated by the surface emitter 200j. In particular, the microlens 2020 may be formed and arranged with respect to the surface emitter 200j to match the original main radiation direction H4 of the

Surface emitter 200j in a deviating main beam direction H4 'transformed. As a result, a laser light source can advantageously also be indicated in the embodiment according to FIG. 9, in which different types of surface emitters are provided such that the laser radiation emitted by the individual surface emitters differs

Main beam directions is emitted. FIG. 10 shows a side view of a further embodiment of the invention, in which, in turn, different surface emitters 200k are assigned different microlenses 2020a, 2020b. According to the invention

Microlenses 2020a, 2020b each formed differently or arranged differently with respect to their associated surface emitter 200k, so that for one or more surface emitter 200k individually shaping of the laser radiation generated by it is possible.

A combination of different types of surface emitters, in particular of VCSEL types or of VECSEL types, is also conceivable, as is the combination of the formation of the different surface emitters with differing structural features and a non-constant packing density.

According to the invention, different main beam directions for the laser radiation generated individually by individual surface emitters can be realized in different ways: Spatial arrangement of a

Surface emitter with respect to a multiple surface emitter receiving support member 300 of the laser light source 100, constructive training

(Current aperture, current contact, number of power contacts, etc., or a combination thereof).

Particularly advantageously, the use of surface emitters of different types achieves a resultant field characteristic for the laser radiation L1 emitted altogether by the laser light source 100, which corresponds to predefinable criteria or to a desired course.

Claims

claims

1 . Laser light source (100) having a plurality of surface emitters (200, 200a, 200b, ..) arranged on a carrier element (300), characterized in that

different surface emitters (200a, 200b) are each formed and / or arranged relative to one another on the carrier element (300) such that main beam directions (H1, H2) of the laser radiation emitted by them are not parallel to one another, and / or

a packing density that is a distance of a first

Surface emitter (200c) to at least one adjacent thereto surface emitter (200d) in at least one dimension describes, is not constant.

2. Laser light source (100) according to claim 1, wherein at least two

Surface emitter (200e, 200f) are formed so that they each have a different field characteristics, in particular far field characteristic (FFC1, FFC2).

3. laser light source (100) according to claim 2, wherein at least two

Surface Emitters (200) differ from each other in at least one of the following features: a. Training, in particular opening area and / or opening shape, a Stromapertur (210b),

b. Arrangement of a current aperture (210b) relative to a current contact (212) in the region of a coupling-out mirror (204) of the

Surface emitter (200),

c. Shape and / or orientation of a current contact (212) to

Supplying the surface emitter (200) with electrical energy, d. Number of power contacts (212) to supply the

Surface emitter (200) with electrical energy. Laser light source (100) according to one of the preceding claims, wherein at least one surface emitter (200h, 200i) is arranged on the carrier element (300) such that an optical axis (ΟΑ ', OA ") of the

Surface emitter (200h, 200i) is not parallel to an optical axis (OA) of at least one further surface emitter (200g) arranged on the carrier element (300), in particular a predeterminable angle with the optical axis (OA) of the at least one further surface emitter (200g). includes.

A laser light source (100) according to any one of the preceding claims, wherein at least one surface emitter (200j) has a microlens (2020) for influencing that produced by the surface emitter (200j)

Has laser radiation, in particular for influencing the

Boresight.

Laser light source (100) according to one of the preceding claims, wherein a plurality of surface emitters (200k, 200k ') are each assigned at least one microlens (2020a, 2020b), wherein at least two

Microlenses (2020a, 2020b) each have different optical properties and / or a different orientation with respect to their respective associated surface emitter (200k, 200k ').

Laser light source (100) according to any one of the preceding claims, wherein different surface emitter (200) each as vertical cavity surface emitting laser, VCSEL, or as a vertical external cavity surface emitting laser, VECSEL, are formed.

Laser ignition system (1000) for an internal combustion engine, in particular a motor vehicle or a stationary motor, comprising a solid-state laser (600) for generating laser ignition pulses (LZ) and having at least one laser light source (100) according to one of the preceding claims

Provision of laser radiation (L1) for optical pumping of the

Solid state laser (600).

Laser ignition system (1000) according to claim 8, wherein a pumping optics (500) is provided which is adapted to shape the radiation emitted by the laser light source (100) radiation, in particular to focus on the solid-state laser (600).

10. laser ignition system (1000) according to claim 9, wherein the pumping optics (500) has at least one optical element with regions of different optical properties, in particular different focal length.

1 1. Laser ignition system (1000) according to claim 10, wherein the at least one optical element is a, in particular radial or circular, segmented lens with partially different surface curvature or a free-form element.