WO2010136384A1 - Laser diodes, which are arranged vertically one above the other, for pumping solid-state lasers with an optimized far field - Google Patents

Laser diodes, which are arranged vertically one above the other, for pumping solid-state lasers with an optimized far field Download PDF

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Publication number
WO2010136384A1
WO2010136384A1 PCT/EP2010/056978 EP2010056978W WO2010136384A1 WO 2010136384 A1 WO2010136384 A1 WO 2010136384A1 EP 2010056978 W EP2010056978 W EP 2010056978W WO 2010136384 A1 WO2010136384 A1 WO 2010136384A1
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laser
refractive index
laser device
semiconductor laser
semiconductor
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PCT/EP2010/056978
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German (de)
French (fr)
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Hans-Jochen Schwarz
Hans Wenzel
Andre Maassdorf
Goetz Erbert
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Robert Bosch Gmbh
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S5/00Semiconductor lasers
    • H01S5/40Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4031Edge-emitting structures
    • H01S5/4043Edge-emitting structures with vertically stacked active layers
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02PIGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P23/00Other ignition
    • F02P23/04Other physical ignition means, e.g. using laser rays
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S2301/00Functional characteristics
    • H01S2301/18Semiconductor lasers with special structural design for influencing the near- or far-field
    • H01S2301/185Semiconductor lasers with special structural design for influencing the near- or far-field for reduction of Astigmatism
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S5/00Semiconductor lasers
    • H01S5/02Structural details or components not essential to laser action
    • H01S5/024Cooling arrangements
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S5/00Semiconductor lasers
    • H01S5/20Structure or shape of the semiconductor body to guide the optical wave; Confining structures perpendicular to the optical axis, e.g. index- or gain-guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/2004Confining in the direction perpendicular to the layer structure
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S5/00Semiconductor lasers
    • H01S5/30Structure or shape of the active region; Materials used for the active region
    • H01S5/305Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure
    • H01S5/3095Tunnel junction
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S5/00Semiconductor lasers
    • H01S5/30Structure or shape of the active region; Materials used for the active region
    • H01S5/32Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
    • H01S5/3211Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures characterised by special cladding layers, e.g. details on band-discontinuities
    • H01S5/3213Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures characterised by special cladding layers, e.g. details on band-discontinuities asymmetric clading layers
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S5/00Semiconductor lasers
    • H01S5/40Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4018Lasers electrically in series
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01SDEVICES USING STIMULATED EMISSION
    • H01S5/00Semiconductor lasers
    • H01S5/40Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4081Near-or far field control

Abstract

The invention relates to a laser device (100) having at least two semiconductor lasers (110, 120), which are arranged like layers one above the other, are in the form of edge emitters, are monolithically integrated and are optically coupled to one another. According to the invention, at least one further semiconductor laser (130) is provided, which is not optically coupled to an adjacent semiconductor laser (120).

Description

description

title

VERTICAL stacked LASER DIODES TO PUMP OF SOLID STATE LASERS WITH THE OPTIMUM FERNFELD art

The invention relates to a laser device having at least two layered superimposed and configured as an edge emitter monolithically integrated and optically coupled with each other semiconductor lasers.

Such a laser device is known from DE 10 2006 061 532 A1. The known laser device has the disadvantage that it is only suitable for pulsed operation, especially for relatively short pulse durations in the nanosecond range because excessive heating of the laser device already occurs at pulse durations in the microsecond range along to form a non-constant in the control temperature profile a Schichtdickenkoordinate the laser device leads. This means that such lasers layers which are located closer to a heat sink at a lower temperature, such as a laser layer arranged further away from the heat sink. The non-constant temperature profile leads to undesirable changes in the refractive index of individual components of the laser device. Particularly in the case of optically coupled structures such variations in the refractive index over the Schichtdickenkoordinate are undesirable because they adversely affect the efficiency of the optical coupling. As a result, in particular those stemming enlarged angle in the far field and higher intrinsic losses.

Disclosure of the Invention

Accordingly, it is an object of the present invention to improve a laser device of the kind mentioned above such that the problems associated with the self-adjusting unbalanced during operation temperature profile disadvantages are avoided.

This object is achieved in the laser device of the type mentioned according to the invention characterized in that a further semiconductor laser is provided at least that is not optically coupled to an adjacent semiconductor laser.

This gives the advantage that despite relatively strong asymmetries of a temperature profile in the at least one further Hableiterlaser

Laser means in the sense of an increase in performance can be provided with respect to the optical output power, which could be but insufficiently coupled with an adjacent semiconductor laser due to the asymmetries. The inventively provided non-coupled semiconductor laser advantageously have a low intensity distribution in the far field, because they are not subject to temperature-related sub-optimal optical coupling.

The inventive combination of a plurality of optically coupled to one another and at least one not optically coupled semiconductor laser thus a laser device having a large optical output can be realized at the same time cheaper intensity distribution in the far field. Unlike traditional laser devices, this advantage is in particular also still exists when an uneven temperature distribution in the laser device is obtained.

This makes it advantageously possible to manufacture laser devices that operate efficiently in contrast to the known systems, even with pulse durations of the laser radiation generated in the microsecond range or even in the millisecond range and the associated self-heating.

The arrangement of the optically uncoupled semiconductor laser in the stack structure of the laser device according to the invention advantageously selected such that they are arranged in the layer thickness areas where relatively high temperature gradients in operation over the layer thickness. A further particularly simple embodiment of the laser device according to the invention is characterized in that a layer structure of the laser device adjacent layer thickness ranges is in two adjacent divided, with a first film thickness portion includes semiconductor lasers that are optically coupled respectively to adjacent semiconductor lasers of the same layer thickness range, and wherein a second layer thickness region semiconductor laser which are not optically coupled to adjacent semiconductor lasers, especially the same layer thickness range. Particularly preferably, the subdivision of the layer thickness ranges as a function of an expected for operation of the laser device is carried out

Temperature profile over Schichtdickenkoordinate. The classification according to the invention in the different layer thickness ranges permits a particularly simple manufacture of the laser device, wherein the optical coupling of adjacent semiconductor laser determining manufacturing parameters only once, namely in the transition area between the two

Layer thickness ranges have to be changed.

An alternating based on the providence of Schichtickenkoordinate optically coupled to each other and non-optically coupled to each semiconductor lasers is also conceivable.

In a further highly advantageous variant of the invention it is provided that a first refractive index profile of a first semiconductor laser over a Schichtdickenkoordinate and based is different to a reference temperature of a second by a respective second refractive index profile

Semiconductor laser. The various semiconductor laser according to the invention, different in terms of the refractive index curve, design based on the reference temperature advantageously permits a compensation of the disturbing effects of an asymmetrical or non-constant temperature profile over the entire laser device.

Particularly preferred is using the principle of the invention, the refractive index profile of different semiconductor laser of the laser device - with respect to the reference temperature, for example room temperature - so different from each other, selected that during operation of the

Laser means and is in this case adjusting non-constant temperature distribution over the Schichtdickenkoordinate effectively as low as possible variations and asymmetries arise with respect to the refractive index of the individual semiconductor lasers. That is, a temperature-induced variation of the refractive index along the Schichtdickenkoordinate in the laser device can, using the principle of the invention by suitable

"Provision" of the refractive index in selected regions of the laser device are at least partially and at least compensate for a certain temperature range. In this way, an operation can be optimized in particular optically coupled to one another semiconductor laser.

In a preferred embodiment of the laser device according to the invention it is provided that an average over a layer thickness of a first semiconductor laser refractive index relative to the reference temperature from a thickness of a layer over a second semiconductor laser averaged

is different refractive index with respect to the reference temperature. According to the invention it has been recognized that the optical coupling of adjacent semiconductor laser impairing deformation of the corresponding laser modes depends essentially on an averaged over the layer thickness of the respective semiconductor laser refractive index and therefore can be affected accordingly. This results in a simplified manufacture of the laser device according to the invention, because it is primarily to ensure compliance with a specified average refractive index and layer eg internal local variations in the refractive index may be permitted within certain limits accordingly.

In a further very advantageous embodiment of the laser device according to the invention it is provided that an average across the layer thickness of the semiconductor laser refractive index depending on the arrangement of the corresponding semiconductor laser within the laser device, in particular in

Depending on a spatial distance to a substrate and / or a heat sink, is selected, whereby a corresponding accurate compensation of thermally induced variations in the refractive index can be obtained in different semiconductor lasers of the laser device. A particularly accurate compensation is another embodiment, further then added, according to the invention when the refractive index of the laser device, in particular forming of the semiconductor laser components, at least in sections varies continuously over the Schichtdickenkoordinate to a self-adjusting during operation of the laser device non-constant temperature profile calculation to carry.

the refractive index of the respective layers are influenced - In an embodiment of a substrate of the laser device of gallium arsenide, for example, by adjusting the aluminum content of a corresponding layers of the laser device - for example, in the context of an epitaxial manufacturing process. The aluminum content in the laser device-forming layers can advantageously be adjusted during manufacture so that depending on the intended operating temperature of the laser device, the rule provided by the pulse durations and the cooling system, which results for the operation, in particular the optical coupling, optimum refractive index profile , This leads, inter alia, that the laser device according to the invention, has at the reference temperature which is usually lower than the operating temperature, a non-constant refractive index profile which is connected to the non-constant temperature profile during operation

Laser device corresponds. That is, the laser device according to the invention - for example, based on room temperature - intentionally unbalanced with regard to their refractive index curve designed so that it has, at the deviates from the room temperature operating temperature or a corresponding non-constant temperature profile is desired, preferably symmetrical and constant refractive index profile.

A particularly simple to implement variant of the invention is characterized in that the refractive index of a layer of a first semiconductor laser at least partially deviates by a predetermined, preferably constant, value of the refractive index of a corresponding layer of a further semiconductor laser.

Another very advantageous variant of the laser device according to the invention provides that the semiconductor lasers have a different number of quantum wells, which is also an influence of an averaged over the respective semiconductor laser refractive index possible.

Due to their high efficiency even in the generation of laser pulses with pulse durations in the microsecond or even millisecond range, the laser device according to the invention is especially suitable for generating pump radiation for optically pumping another laser systems, particularly solid-state lasers with passive Q-switching.

the laser device according to the invention is particularly preferably used to generate a pulsed operation laser pulses with pulse durations of at least about two microseconds, preferably at least about ten microseconds.

Further features, application possibilities 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 the features described or depicted, or in any combination form the subject of the invention, irrespective of their summary in the claims or their back-reference and regardless of their formulation or representation in the description or in the drawing.

In the drawing:

1 shows a refractive index profile over a Schichtdickenkoordinate a conventional laser device;

Figure 1 b is a temperature profile across the Schichtdickenkoordinate of the laser device according to figure 1a in a pulse mode with

Pulse durations in the nanosecond range;

Figure 1 c is an intensity distribution by the laser device in accordance

Figure 1 a laser radiation generated in the far field; 2a shows a refractive index profile of a conventional

Laser device, as it results in a pulsed mode with pulse durations in the microsecond range;

Figure 2b is a temperature profile plotted against

Schichtdickenkoordinate for the laser device of Figure 2a;

2c shows an intensity distribution of the laser radiation generated by the laser device according to Figure 2a in the far field;

3a to 5a each having a refractive index profile over a

Schichtdickenkoordinate according to the present invention;

3b to 5b the refractive index curves of Figures 3a to 5a corresponding temperature profiles; 3c to 5c the refractive index gradients in Figures 3a to 5a corresponding intensity distributions in the far field;

Figure 6, 7 has a refractive index profile over the Schichtdickenkoordinate according to further embodiments; and

Figure 8 is a schematic representation of an embodiment of laser device according to the invention.

Figure 1a is a graph showing a refractive index n of the components of a conventional laser device with a total of three sandwiched superposed as an edge emitter formed monolithically integrated semiconductor lasers 110, 120, 130th

The refractive index profile n is applied over a Schichtdickenkoordinate x corresponding to a direction of growth of an epitaxial manufacturing process, be layers grown at which individual components 110, 120, 130 of the conventional laser device one after another in a known manner to a substrate.

In the example illustrated in figure 1a structure of the first semiconductor laser is left 1 10 is disposed a non-illustrated herein gallium arsenide substrate, and on the right of the third semiconductor laser 130 is also a heat sink, not shown.

In addition to the refractive index profile n 1a shows also a corresponding course of the square E 2 the electric field strength in the

Laser device which is also applied over the Schichtdickenkoordinate x.

As is apparent from Figure 1 a, which have a total of three semiconductor lasers corresponding to the layer regions 110, 120, 130, each having the same

Refractive index curve n on. In this case surrounded waveguide portions 1 12a, 112b having a refractive index nθ an unspecified active zone, for example, having a quantum well and a greater refractive index than the waveguide regions 112a, 1 12b. The other semiconductor laser 120, 130 have an identical construction and are of adjacent

Semiconductor lasers each separated by tunnel diodes 140 which are sandwiched between barrier layers 150 with a low refractive index.

One is adjusting in a pulse operation of the laser device temperature profile, ie, the temperature gradient in the laser device applied over the Schichtdickenkoordinate x, is indicated in Figure 1 b. The temperature T is as shown in Figure 1 b can be seen constant over the entire thickness of the laser device, because only pulse durations are used in the nanosecond range with a sufficiently long pulse pauses present, whereby a correspondingly lower heat input in the laser device.

Therefore, the entire laser device, the ambient temperature, for example room temperature to.

Figure 1 c shows an intensity distribution I plotted versus the angle θ, as it appears in the far field of the conventional laser device. About 95% of the radiated energy as laser radiation lying in an angular range Δθ of 60 °, so that efficient operation is given.

2a shows a refractive index profile n that already described with reference to Figure 1a to 1c conventional laser device, as it results when operating with pulse durations in the microsecond range. Due to the compared to the scenario of Figure 1 a much larger pulse durations there is a not negligible heating of the conventional laser device, which is evident from the temperature profile T according to Figure 2b. A maximum temperature prevails in areas such as

Laser devices 110, 120, 130 while there is a relatively low temperature in the range of the laser device, which is due to the fact that the laser device 130 in proximity to the aforementioned heat sink, such as a heat sink is located.

Because of the now non-constant temperature profile T according to Figure 2b gives a x dependent on the Schichtdickenkoordinate change in the refractive index n of the various semiconductor lasers 110, 120, 130, see FIG. Figure 2a. Ie, during the pulse operation with pulse durations in the microsecond range, the three semiconductor lasers 110, 120, 130 do not have identical refractive index profiles n more, as was the case in the scenario shown in FIG 1a with only an insignificant heating. Due to the individual variations of the refractive index n of the semiconductor lasers 110, 120, 130, the laser mode concerned are deformed accordingly, and there are no longer optimum conditions for the optical coupling of the semiconductor laser 1 10, 120, where the 130th This is reflected in 2 of the electric field of Figure 2a also the unsymmetrical distribution of the square of E.

Correspondingly, the angle range Δθ increases (Figure 2c), occur in the about 95% of the radiated energy, detrimental to about 81 °.

According to the invention is, therefore, provided that at least one semiconductor laser 130 is provided in place of each optically coupled to one another semiconductor lasers, which is not optically coupled to an adjacent semiconductor laser 120th Figure 8 shows schematically a side view of an embodiment of laser device 100 according to the invention are laminated in the three formed as an edge emitter semiconductor laser 1 10, 120, 130 in a stacked array monolithically integrated one above the other. Adjacent semiconductor laser 1 10, 120 are in this case connected in a known per se manner via a tunnel diode 140 with each other to allow electrical supply of the semiconductor lasers 110, 120, 130th Corresponding electrodes on the surfaces of the laser device are not shown 100th

The inventive principle described below can be applied to general

Laser devices are used with any number of stacked edge emitter, sake of clarity, however, subsequently be explained with three stacked semiconductor lasers 110, 120, 130 by means of a laser device 100th

The spatial coordinates also shown in Figure 8 x indicates a direction of growth of an epitaxial manufacturing process in which the individual components of the laser device 100 are successively layered, grown in a conventional manner on a substrate 102, such as a GaAs substrate.

The laser device 100 has in arranged in known manner barrier layers 150, the optical coupling of adjacent semiconductor laser 110, control 120, and at the same time ensure that the radiation field does not exceed a predetermined threshold value in the area of ​​the tunnel diode 140, to the intrinsic losses in which the to keep tunnel diode 140 associated layer region low.

The semiconductor lasers 110, 120, 130 have the indicated in figure 8 by the double arrows x1, x2, x3 layer thicknesses, and the radiation emitted by them

Laser radiation is symbolized by the block arrow 200th

In the upper area in Figure 8 of the laser device 100, a heat sink 104 is disposed, for example, with a cooling device, such. For example, a Peltier element may be connected to and serves to cool the laser device 100th A refractive index profile n the inventive laser device 100 is depicted in Figure 3a. In this embodiment, the refractive index profile n of the laser device 100 is advantageously selected such that optical coupling between the semiconductor lasers 110, 120, but is not placed between the semiconductor lasers 120, 130th This is presently effected by the

Barrier layers 150 'between the non-optically coupled semiconductor lasers 120, 130 a greater layer thickness, measured along the Schichtdickenkoordinate x having as barrier layers 150 between the optically coupled semiconductor lasers 110, 120. Alternatively, or in addition to the increased layer thickness of the barrier layers 150' can be used for formation of the barrier layers 150 'for the purpose of optical isolation also a lower refractive index than in the conventionally formed barrier layers are used 150th

That is, the barrier layer 150 'according to the invention for realizing the optical

Decoupling may differ in particular with respect to their layer thickness and / or its refractive index by the conventional barrier layer 150th

As a result of the inventive selective decoupling of the semiconductor laser 130 may oscillate in only one laser mode having favorable far field distribution is depicted in Figure 3c.

The inventive combination of optically coupled semiconductor laser 110, 120 with the optically coupled semiconductor laser 130 is not constant in spite of the temperature profile T, see FIG. 3b, a more efficient operation of the

Laser device 100 possible because the problem of asymmetry of the refractive index n with respect to the optical coupling between the semiconductor lasers 120, 130 due to the lack of optical coupling does not occur

Figures 4a, 5a show two possible modes, which in the area of ​​the optically coupled semiconductor laser 1 10, 120 can occur in accordance with Figure 3a, see FIG. and the respectively resulting far field in the Figures 4c, 5c.

By compared to the layer boundary 120, 130 low, but nonzero, temperature differences in the field of semiconductor lasers 110, 120 (Figure 4b, 5b) can oscillate both modes shown. However, the efficiency losses occur through a different strong light field E 2 in the regions 1 10, 120 are not as strong from, as thus greater differences in refractive index is given in the range of greater temperature differences and usually. The two modes are typically different from each other,

Far-field angle of approximately 65 °, Figure 4c, and about 55 °, figure 5c. If both modes oscillate at the same intensity, a far-field angle of about 60 ° is expected, which in the design of the waveguide layers of the semiconductor laser 1 10, 120 is taken into account.

It is also possible to design the structure that only the fashion shown in Figure 5a has sufficiently small intrinsic losses and thus oscillate just this fashion. For this purpose, for example, provide 140 an increased optical coupling or a thicker tunnel diode layer.

A further advantageous variant of the invention provides that a first refractive index profile of a first semiconductor laser 110 via the Schichtdickenkoordinate x and based is different to a reference temperature from a respective second refractive index profile of a second semiconductor laser 120. variation of this inventive of

Refractive index gradient between different semiconductor lasers 110, 120 of the laser device is advantageously a substantial compensation of the above-described known conventional laser devices, the effect of influencing the refractive index gradient due to the temperature profile possible.

6 shows a refractive index profile n optically coupled to one another semiconductor laser 1 10, 120 of a corresponding embodiment of the laser device 100, as it emerges under the influence of temperature effects during a Pυlsbetriebs with pulse durations in the microsecond range. The present invention further decoupled semiconductor laser 130 (Figure 3a) is not shown in Figure 6 for clarity.

In addition to the profile of the refractive index n of the laser device 100 through the Schichtdickenkoordinate x of the epitaxial manufacturing process in Figure 6, the light distribution over the Schichtdickenkoordinate x in the form of the square E 2 the electric field strength in the laser device 100 is specified.

Each semiconductor laser 110, 120 has an active region 111, 121 with a quantum film or the like. The active region 11 1, 121 are each of a

Waveguide 1 12a, 112b, or in the case of other semiconductor laser 120 of waveguides 122a, 122b surrounded.

On the outside of the waveguide region 12a 1, a cladding layer 101 is disposed, whose refractive index is smaller than the refractive index of the

Waveguide portion 1 12a.

Centrally with respect to the semiconductor lasers 110, 120 is a tunnel diode 140 disposed intermediate the already described with reference to Figure 8, barrier layers 150th

The barrier layers 150 affect the light distribution of E 2 in the laser device 100 advantageously so that an optical coupling between the guided in the first waveguide 1 12a, 112b guided radiation with the second in the waveguide 122a, 122b radiation is possible. At the same time, the barrier layers 150 advantageously prevent a too strong extent of the light field in between the semiconductor lasers 10 1, 120, 130 regions located so that, inter alia, absorption through the tunnel diode 140 is low.

According to the invention, the refractive index profile n of the semiconductor lasers 110, 120 - relative to a reference temperature - selected differently from one another.

Advantageous in the non-constant temperature profile T (Figure 3b) is taken into account, which results during operation of the laser device 100 in a Pυlsbetrieb with Pυlsdaυem in Mikrosekυndenbereich.

Temperature effects are due to the inventive selection of the refractive index gradient n advantageously compensated for the refractive index profile such that in each case on the film thicknesses x1, x2 (Figure 8) of the semiconductor laser 1, 10, 120 average refractive index - taking into account the

becomes a desired value - temperature influence. The inventive modification of the refractive index profile of the semiconductor laser 1 10, 120 is carried out as in Figure 6 can be seen in the present embodiment by the provision of special regions 1 12a ', 1 12b', 122a ', 122b', whose refractive index is chosen to be somewhat less than the refractive index of the surrounding further waveguide regions 112a, 1 12b, 122a, 122b.

Thereby, the reinforced in the region of the semiconductor laser 120 during operation warming, see FIG. the temperature profile T of Figure 3b, is counteracted in such a way that an average refractive index is obtained for the semiconductor laser 120 under the influence of the higher temperature, which approximately corresponds to the averaged refractive index of the temperaturbeaufschlagten same extent semiconductor laser 1 is 10 degrees.

Thereby, advantageously the optical coupling between the semiconductor lasers

110, 120 improves, so that in addition to the inventive Providence not optically coupled semiconductor laser 130 in the area of ​​the optically coupled semiconductor laser 110, 120 an improved far-field characteristics can be obtained.

Although the inventive configuration of the semiconductor laser 1 10, 120 n in the present case a far-field distribution is obtained with two main peaks with non-constant refractive index profile, about 95% of the observed radiation power are in a predetermined angular range ΔΘ = 60 °, so that the laser device 100 of the invention preferably in the range is used by high-power laser applications that do not necessarily require a single main peak, but rather only a high concentration of the radiation power in the predetermined angle range Δθ. Therefore, the laser device 100 of the invention is particularly suitable for use in laser-based ignition systems for internal combustion engines, especially as a pumping light source for optical pumping of other laser devices, such as passive Q-switched solid state lasers, which are arranged in laser spark plugs. The laser device 100 of the invention is preferably implemented in the form of an AlGaAs system, the active regions 111, 121, 131 GaAsP and / or InAlGaAs have.

7 shows a refractive index profile n optically coupled to one another

Semiconductor lasers 110, 120 to a further embodiment of the laser device 100 in which the modification according to the invention is carried of via the respective semiconductor lasers 110, 120, average refractive index in that the active zones 11 1, 121 each have different many quantum wells. Since the introduction of another quantum film results in the active region 111 to a sharp increase in the average refractive index of the semiconductor laser 1 is 10, it is advantageous, at the same time to reduce the refractive index in the surrounding waveguide 1 12a, 112b. The purpose, for example, required increase in the aluminum content of the waveguides 112a, 1 12b forming material is in the single digits and can be well controlled in the context of conventional epitaxial manufacturing processes.

It is also advantageous to increase the refractive index of the tunnel diodes 140 surrounding barrier or cladding layers 150th The position of the quantum wells relative to the surrounding waveguides 1 12a, 112b may be modified according to the invention to temperature-induced distortions of the refractive index profile n compensate for a predeterminable operating temperature range.

The measures described above provide a high degree of

Compensation of temperature-induced asymmetrical influence of the refractive index profile n via the optically coupled to one another semiconductor laser 110, 120, which leads to a substantially symmetrical light field distribution E 2 is at operating temperature and to the previously described favorable far field.

The present invention not optically coupled semiconductor laser 130 may comprise one to the semiconductor lasers 110, 120 comparable or even a different refractive index profile. Other measures according to the invention influence of the refractive index curve n in the sense of a compensation of temperature effects may include: provision of different layer thicknesses for the waveguide regions 112a, 112b, 122a, 122b, 132a, 132b, the barrier layers 150, 150 'as well as the addition of other components such as phosphorus at of the

Manufacturing the laser device 100 in order to change the refractive index profile n.

The above measures according to the invention can also be combined with each other and also generally to laser devices having more than three semiconductor lasers 1 10, 120, 130 applicable.

A relative to the Schichtickenkoordinate x alternating provision of optically coupled with each other semiconductor lasers 10 1, 120, and is not optically coupled to one another semiconductor lasers 130 is also conceivable.

In addition to a continuous variation of the refractive index n over Schichtdickenkoordinate x, which requires a very precise adjustment of the aluminum or other refractive index n affecting contaminant level, such as a certain portion 112a '(Figure 6) a waveguide layer 1 12a with a changed refractive index formed in order to achieve the effect of the invention.

A further particularly simple embodiment of the laser device 100 according to the invention is characterized in that a layer structure of

Laser device is divided into two adjacent layer thickness ranges B1, B2 (Figure 8) 100, a first film thickness portion includes B1 semiconductor lasers 110, 120 which are optically coupled respectively to adjacent semiconductor lasers of the same layer thickness range, and wherein a second layer thickness region comprises B2 semiconductor laser 130 not with neighboring

Semiconductor lasers, especially the same layer thickness range, are optically coupled. Particularly preferably, the subdivision of the layer thickness ranges is effected in dependence on an expected for operation of the laser device 100 on the temperature curve T Schichtdickenkoordinate x. The classification according to the invention in the different layer thickness ranges B1, B2 permits a particularly simple manufacture of the laser device 100 in which the optical coupling of adjacent semiconductor laser 1 10, 120 determining manufacturing parameters only once, namely, change in the transition region between the two coating thickness areas B1, B2 have to.

Optically isolated from their neighbors semiconductor laser 130 are preferably provided in those areas of the laser device 100, where large temperature changes over the Schichtdickenkoordinate x present in operation.

Due to their high efficiency, in the generation of laser pulses with pulse durations in the microsecond or even the millisecond range, the laser device 100 of the invention is especially suitable for generating pump radiation 200 for optical pumping of other laser systems, particularly solid-state lasers with Passive Q-switching.

the laser device according to the invention is particularly preferably 100 to optically pump in a pulsed operation laser pulses with pulse durations of at least about two microseconds, preferably to produce at least about ten microseconds, in particular solid-state laser of laser spark plugs.

Claims

claims
1. Laser device (100) having at least two layered superimposed and edge emitter formed monolithically integrated and optically coupled with each other semiconductor lasers (110, 120), characterized in that at least a further semiconductor laser (130) is provided, which does not (with an adjacent semiconductor laser 120) is optically coupled.
2. Laser device (100) according to claim 1, characterized in that a layer structure of the laser device (100) in two adjacent
Layer thickness ranges (B1, B2) is divided, with a first layer thickness range (B1) semiconductor laser (1 10, 120), each with adjacent semiconductor lasers (110, 120) of the same layer thickness range (B1) are optically coupled, and wherein (a second layer thickness region comprising B2) semiconductor laser (130) that are not adjacent with
Semiconductor lasers (130), in particular of the same layer thickness range (B2), are optically coupled.
3. Laser apparatus (100) according to any one of the preceding claims, characterized in that a first refractive index curve (s) of a first
The semiconductor laser (110) over a Schichtdickenkoordinate (x) and is related to a reference temperature is different from a corresponding second index of refraction profile of a second semiconductor laser (120).
4. averaged laser device (100) according to any one of the preceding claims, characterized in that a layer thickness (x1) of a first semiconductor laser (110) based average refractive index to a reference temperature from a higher layer thickness (x2) of a second semiconductor laser (120) is different refractive index with respect to the reference temperature.
5. Laser device (100) according to any one of the preceding claims, characterized in that the refractive index (n) of the laser device (100), in particular of the semiconductor laser (110, 120) forming components, at least partially continuously over the
Schichtdickenkoordinate (x) changes.
6. Laser device (100) according to any one of the preceding claims, characterized in that the refractive index (n) of a layer (1 12) of a first semiconductor laser (1 10) at least in sections by a predetermined, preferably constant, value of the refractive index (n) a corresponding layer (122) of a further semiconductor laser (120) is different.
7. Laser device (100) according to any one of the preceding claims, characterized in that the semiconductor laser (110, 120, 130) a different number of quantum wells (11 1, 121, 131).
8. A method for optical pumping of a laser, in particular a passively Q-switched solid state laser, characterized in that at least one laser device (100) according to any one of the preceding claims is used to generate the pump radiation for optically pumping the laser.
9. The method of claim 8, characterized, in that the
Laser means (100) generated in a pulsed operation laser pulses whose pulse duration is at least 2 microseconds, preferably at least 10 microseconds.
PCT/EP2010/056978 2009-05-28 2010-05-20 Laser diodes, which are arranged vertically one above the other, for pumping solid-state lasers with an optimized far field WO2010136384A1 (en)

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