WO2015106972A1 - Laser à semi-conducteur à dissipation de chaleur anisotrope - Google Patents

Laser à semi-conducteur à dissipation de chaleur anisotrope Download PDF

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Publication number
WO2015106972A1
WO2015106972A1 PCT/EP2015/000092 EP2015000092W WO2015106972A1 WO 2015106972 A1 WO2015106972 A1 WO 2015106972A1 EP 2015000092 W EP2015000092 W EP 2015000092W WO 2015106972 A1 WO2015106972 A1 WO 2015106972A1
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WIPO (PCT)
Prior art keywords
heat
heat spreader
spreader
thermal conductivity
laser element
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PCT/EP2015/000092
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German (de)
English (en)
Inventor
Jürgen Wolf
Matthias Schröder
Petra Hennig
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Jenoptik Optical Systems GmbH
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Jenoptik Laser GmbH
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/024—Arrangements for thermal management
    • H01S5/02476—Heat spreaders, i.e. improving heat flow between laser chip and heat dissipating elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/0235—Method for mounting laser chips
    • H01S5/02355—Fixing laser chips on mounts
    • H01S5/02365—Fixing laser chips on mounts by clamping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/02—Structural details or components not essential to laser action
    • H01S5/022—Mountings; Housings
    • H01S5/0235—Method for mounting laser chips
    • H01S5/02355—Fixing laser chips on mounts
    • H01S5/0237—Fixing laser chips on mounts by soldering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
    • H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
    • H01S5/4031—Edge-emitting structures

Definitions

  • the invention relates to a semiconductor laser, which can be preferably designed as a diode laser bar with one or more emitters and is equipped with measures that allow efficient dissipation of the waste heat and also an improved electrical contact
  • the isotropic heat spreading with metal bodies is known, for example, from DE 10 2008 026 229 A1 and from US Pat. No. 8,486,766 B1.
  • the heat spreader serve simultaneously as electrical
  • Heat spreader made of metal or ceramic have a low elasticity, so that mechanical stresses can occur in the laser element.
  • the thermal conductivity is limited.
  • copper has a thermal conductivity of less than 400W / (m * K).
  • a ductile indium layer must be provided. An indium coating is complicated and expensive.
  • Graphite components is highly oriented in the direction of the surface normal of the carbon film, the carbon film is in the direction of the surface normal, ie by the thickness d of the film, poor thermal conductivity. This direction of least thermal conductivity is referred to below as the z ' direction. For the sake of completeness, it should be noted that this means that it is
  • CONFIRMATION COPY the preferred direction of the graphite components is.
  • the electrical conductivity of the carbon film in the c direction is also poor. Since the flow of current to the laser element is via the carbon foil, a voltage drop occurs across the thickness of the carbon foil, which leads to an increased electrical power loss. Therefore, unnecessary waste heat is generated.
  • the carbon film is selected as thin as possible, for example 25 ⁇ . But also the desired effect of heat spreading is suboptimal low pronounced. It is also intended, the graphite foil during assembly of the laser
  • a light-emitting component which contains a layer of anisotropic graphite.
  • This graphite layer is oriented so that the c direction, i. H. the direction of least thermal conductivity is oriented in the direction of the surface normal.
  • a disadvantage of this mounting technology is that a heat spread occurs mainly in the layer plane and the heat transfer through the graphite layer is poor, since this direction of the c
  • From DE 10 201 1055 891 A1 is a semiconductor laser diode with a structured
  • Metallization layer known. By structuring the metallization layer, heat dissipation is allowed to vary along a longitudinal or lateral direction.
  • the metal as a layer material has a material-related isotropic thermal conductivity. Due to the structuring, the thermal conductivity can be reduced in certain areas or directions. This has the disadvantage that the heat dissipation is deteriorated overall.
  • the thermal bonding surface of the diode laser bar can be reduced, which is the
  • Objects of the invention are the disclosure of a method for the efficient removal of the waste heat of a semiconductor laser and the specification of a semiconductor laser with efficient removal of the waste heat. Another equally important task is to ensure an efficient power supply to the semiconductor laser.
  • the laser element should be as small as possible
  • the object of the invention can additionally
  • a semiconductor laser comprising a laser element, a first heat spreader having anisotropic thermal conductivity, which has a lowest thermal conductivity in a direction z ' , and a first heat sink, wherein the laser element is a first
  • Heat spreader a first angle a of more than 5 ° to the surface normal n of
  • the solution of the problem further comprises a method for heat dissipation of a
  • Laser element by means of a heat spreader with anisotropic thermal conductivity, which has a heat input surface with a surface normal n.
  • the direction of least thermal conductivity of the heat spreader at an angle of more than 5 ° to
  • the invention enables the efficient removal of the waste heat of a semiconductor laser.
  • an electrically pumped semiconductor laser diode laser
  • the laser element may comprise one or more gain regions, in which an optical amplification takes place, which leads to the formation of laser radiation, which profit regions may be electrically pumped
  • the laser element may be designed in such a way that in the gain ranges only for photons in a specific direction a reinforcement takes place, which is referred to as the longitudinal direction In the laser element, therefore, there is a longitudinal direction y, which is defined by the fact that only for photons that move in this direction or in the
  • the laser element may be a gain guided laser element.
  • the profit areas can be laterally, d. H. transversal, bounded by unpumped areas.
  • the profit areas can be pumped electrically. They can be located in an epitaxially produced on a substrate layer sequence, wherein the layer sequence an active layer (quantum trench), the between two light-guiding layers
  • the substrate may have a thickness of between 50 ⁇ m and 200 ⁇ m, while the layer sequence may be, for example, between 3 ⁇ m and 20 ⁇ m thick.
  • the layer sequence can be designed as a pn junction.
  • the profit ranges can be defined by a structured isolation layer. Only in the recesses in which the
  • the Laser element may be in the longitudinal direction, for example, 0.5 mm to 6 mm long. However, the laser element can also be embodied as a ridge waveguide or as an index-guided laser.
  • the laser element may, for example, be a diode laser bar with one or more emitters. The individual emitters are then the profit areas of the laser element, with the possible exception of any unpumped areas. Profit areas are thus the areas in which an optical amplification takes place so that laser radiation is generated.
  • a diode laser bar with only one emitter is also referred to as a single emitter.
  • the term diode laser bar in the following expressly includes single emitter.
  • the emitters may preferably be designed as broad-band emitters.
  • the laser element for example a diode laser bar, can have a plurality of profit regions which are parallel to one another, wherein the individual profit regions can be offset in an offset direction perpendicular to the longitudinal direction x and in each case one and the same
  • the width of the profit regions may be, for example, between 5 pm and 200 pm in the transverse direction x, while the distance p may be, for example, 20 pm to 500 pm.
  • the width of the laser element results from the number and width of the profit regions, as well as their distance from one another.
  • the width of the laser element in the transverse direction may be, for example, 0.5 mm to 10 mm.
  • the laser element may preferably be formed as edge emitter.
  • the emission direction of the radiation emitted by the laser element can correspond to the longitudinal direction y of the laser radiation in the laser element.
  • a beam deflection can also be provided in the laser element, so that the direction of the laser radiation outside the laser element can deviate from the longitudinal direction of the laser radiation in the gain range of the laser element.
  • the laser element may additionally contain lattice structures, for example known DBR or DFB gratings.
  • the laser element can be electrically pumped and can be operated with a high current.
  • the operating current can be, for example, 1 A to 1000 A.
  • the individual emitter regions can be preferred as wide-band emitter or as
  • the laser element can also be designed as a vertical resonator structure (VCSEL).
  • VCSEL vertical resonator structure
  • In addition to or between the gain ranges of a laser element can be unpumped areas that are not flowed through by the operating current. These can be covered, for example, with an insulating masking layer.
  • the laser element may be terminated with mirrors, for example a high-reflectance mirror layer may be attached to the back facet of the laser element and a low one on the opposite exit-side facet containing the exit aperture reflective mirror layer with a Refelxionsgrad of, for example, 0, 1% to 10%.
  • the mirrors can define a laser resonator that enables laser operation.
  • the laser element can also be designed as a profit element, which is provided only in cooperation with an external resonator for laser operation. In this case, for example, a
  • Such an electro-optical gain element is also to be understood as a laser element in the sense of the invention.
  • the laser element has a first contact surface, which is used for thermal contacting of the
  • the first contact surface can also be used for electrical contacting of the
  • the laser element may have a second contact surface, which serves for making electrical contact with the other electrode of the laser element.
  • This can, but does not have to, also be used for thermal contacting.
  • the first contact surface may be the epitaxial-side electrode of the laser chip, the second contact surface, the opposite substrate-side electrode of the laser chip.
  • the first contact surface may therefore be the anode of a laser diode.
  • Contact surface can be the cathode.
  • the first contact surface of the laser element may comprise a metal layer in a preferred embodiment of the invention.
  • the metal layer may, for example, preferably be applied flat on the p-side contact surface of the laser element. It may be, for example, a metallic layer whose chip-remote side consists for example of gold. Preference may be given to a galvanically reinforced gold layer having a thickness preferably greater than 0.5 pm, more preferably between 1 ⁇ and 10 ⁇ , are used.
  • a metal can be selected whose electrical conductivity, which may be isotropic, is higher than the highest electrical conductivity of the heat spreader. It should be noted that the thermal conductivity of this metal, which may also be isotropic, may well be less than the highest thermal conductivity of the heat spreader.
  • This metallic layer can be an advantageous
  • a metallic layer can also be on the n-side contact surface or on both
  • a metal layer preferably of gold, can also the
  • a gold layer can also be soft, so that only low mechanical stresses in the
  • the laser element can also be an optically pumped laser element. In this case, no power supply to the laser element is required.
  • the semiconductor laser comprises a first heat spreader, which may preferably be embodied as a solid (that is, as a compact or homogeneous) body.
  • the first heat spreader is disposed between the laser element and the first heat sink.
  • a solid body is understood to mean that it is not composed of individual layers or of particles that must be held together by forces, but rather that an intrinsic cohesion of the material
  • the first heat spreader and also, if present, the further heat spreader may thus preferably consist of a homogeneous material which is anisotropic according to the invention.
  • the first heat spreader has a heat entrance surface in thermal contact with the first contact surface of the laser element.
  • Heat spreader can rest directly on the first contact surface.
  • the support surface is considered below as a heat input surface. It can also have the function of an electrical contact surface at the same time.
  • the heat spreader can be larger than that
  • the embodiment is preferred in which the contact surface of the laser element is connected to a single first heat spreader.
  • the surface normal n of the heat input surface is defined below in such a way that it points into the interior of the heat spreader.
  • the first heat spreader has a heat exit surface in thermal contact with the heat sink.
  • the heat input surface can be the same size as the heat exit surface. It can also be the largest of the surfaces that limit the heat spreader.
  • Heat exit surface may preferably be parallel to the heat input surface.
  • Heat spreader may be cuboid.
  • ⁇ is the thermal conductivity tensor of the material making up the heat spreader
  • q is the heat flow density vector
  • gradT is the temperature gradient, which is also a vector.
  • a Cartesian coordinate system is chosen as the reference system, in which the z direction of the normal n corresponds to the heat input surface of the heat spreader.
  • the y-direction can be used in the case of a
  • edge emitting laser bars are chosen so that they the longitudinal direction of the Laser radiation in the resonator corresponds, that is in the direction of or the profit ranges.
  • the direction y may be opposite to the direction of the exiting laser beam.
  • the x-direction then results as normal to the yz-plane. You can, for example, the laser bar
  • Light exit surface correspond.
  • the heat input surface of the considered heat spreader is then in the xy plane.
  • a graphite layer is arranged as slaughterhouse in such a way that the direction Z 'of the lowest thermal conductivity ⁇ m in the z-direction, and the largest thermal conductivity ⁇ M in the xz plane is present, wherein the thermal conductivity in be equal to x and y direction and may have a value ⁇ ⁇ .
  • the thermal conductivity tensor may have the following shape:
  • This representation may be a symmetric tensor in diagonal form.
  • two may have the same amount ⁇ ⁇ , so that the
  • Thermal conductivity tensor has two different eigenvalues ⁇ ⁇ and ⁇ m .
  • Coordinate stem x ' y ' z 'can take the following form:
  • the sense of direction of z ' can be chosen without restriction of generality such that z ' at the heat entrance surface points into the interior of the heat spreader. Therefore, the angle ⁇ defined below can be restricted to a value range of 0 ° to 90 °.
  • the coordinate system x ' y ' z ' should be linked via the transformation matrix M to the coordinate system xyz defined above, so that each vector r' in the coordinate system x ' y ' z 'has the coordinates r in the coordinate system xyz
  • the coordinate system x ' y ' z ' may be related to the coordinate system xyz, for example by a rotation about the x axis.
  • the angle of rotation is the angle between n and z ' , which comprises a value range of 0 ° to 90 °.
  • the angle can be
  • the matrix M has the following form:
  • the thermal conductivity tensor in the reference frame xyz then has the following shape
  • the z-direction is essentially the direction of the intended heat flux from the laser element to the heat sink, i. h, the direction from the heat entrance surface to the heat exit surface of the heat spreader. It should be noted that this consideration is only for the understanding of the invention. In practice, temperature gradients also occur in the xy plane.
  • Equation 2 Equation 2
  • Heat flux density q T z A m .
  • the angle a should be chosen from this observation so that A M -sin (ar) is greater than A m .
  • a M - sin (ör) is nine times higher than A m .
  • the angle of rotation a is not limited to small angles, it may also preferably be a right angle or be selected close to 90 °.
  • the direction z 'of the lowest thermal conductivity may, for example, lie in the direction y (longitudinal direction of the laser radiation in the laser element). Then the heat transfer through the heat spreader in the z-direction by utilizing the maximum thermal conductivity t M of the material is possible. However, then the heat spreading in the heat spreader is mainly possible only in the x-direction, while in the y-direction, the low thermal conductivity A m acts, causing the heat spreading in y-direction can occur only to a very small extent.
  • Such an effect can be used to design the temperature profile of the laser element.
  • This may be advantageous, for example, to minimize the known phenomenon that the middle emitters are more heated in the operation of the laser bar relative to the edge emitters.
  • Another advantageous effect of this measure can be that the temperature distribution in the x-direction over the width of an emitter is more homogeneous than with existing heat spread.
  • An emitter of a laser bar is known as a result of
  • Heat spreader be provided, or the angle a is less than 90 °, preferably less than 85 ° selected.
  • a rotation angle a deviating from the right angle may be provided, for example an angle of 45 ° about the x-axis.
  • more than 70% of the maximum thermal conductivity ⁇ ⁇ of the material can be used both for the passage of heat from the heat inlet surface to the heat outlet surface of the heat spreader, while also more than 70% of ⁇ ⁇ are available for heat spreading in the heat spreader in the y direction. In the x-direction would then even the maximum thermal conductivity for
  • the rotation can also take place about another axis, for example the y-axis.
  • a different axis of rotation in the xy plane can be selected, which may for example have an angle of 45 ° to the x-axis.
  • the basic idea of the invention is thus the use of a first anisotropic heat spreader having a heat entrance surface whose normal n points in a direction z, wherein the minimum of the directional thermal conductivity of the heat spreader lies in a direction z ' .
  • the direction z according to the invention has an angle a of 5 ° to 90 ° to the direction z ' .
  • the electrical conductivity of the first heat spreader may also be anisotropic.
  • the electrical conductivity of the heat spreader can also be represented as a tensor second stage.
  • ⁇ is the electrical conductivity tensor of the material making up the heat spreader
  • j is the vector of current density
  • E is the electric field strength, which is also a vector.
  • the electrical conductivity tensor can have the following shape analogous to the thermal conductivity tensor:
  • the direction of minimum electrical conductivity may coincide with the direction z ' of minimum thermal conductivity.
  • the coordinate system of the principal axes of this tensor can therefore be oriented in the same way as in the tensor of the thermal conductivity. Since the electrical and thermal conductivity of solids are often directly related, the electrical conductivity can also have a similar ratio between the minimum value and the maximum value.
  • the minimum electrical conductivity may be in the same direction z ' as the minimum of the thermal conductivity. Therefore, the above-mentioned inventive introduction of a rotation angle a equally leads to a significant improvement of the power supply to the laser bar. If, as in the above example calculations, the heat connection by factors 9 or Can be improved, the resulting in the interior of the heat spreader electrical power loss can be reduced by such a factor.
  • the heat spreader according to the invention can be embodied as a homogeneous anisotropic body. This means that it does not consist of individual slats, for example, but consists of a solid piece of material. As a material for heat spreader is oriented or highly oriented TPG (thermal pyrolytic graphite) into consideration. With known
  • Manufacturing processes can be produced plane-parallel flat blanks, which are expanded in a plane xy and in the z-direction has a thickness d.
  • the ab-levels are the
  • TPG material of greater thickness is required.
  • special manufacturing processes that produce small angle errors are suitable.
  • WO 2005/029931 for example, a method for the production of TPG with low
  • This TPG can be made in large thickness, from which the
  • the material TPG is a three-dimensionally ordered graphite structure with a high thermal conductivity in the xy plane, which corresponds to the preferred orientation of the ab plane of the graphite.
  • the thermal conductivity may be greater than 1000W / (m * K) or preferably greater than 1500 W / (m * K).
  • the thermal conductivity in the z ' direction, which corresponds to the preferred orientation of the graphite in the c direction, may be less than 20 W / (m * K).
  • Heat spreader may, but need not, be provided with a metal layer.
  • a metal layer may, for example, on the heat input surface and / or the heat exit surface of the
  • the metal layer may for example consist of copper.
  • it may additionally have a gold surface and a diffusion barrier, for example of nickel, so that the layer sequence may have the following structure: Cu-Ni-Au.
  • Base material and the Cu layer may be an adhesion-promoting layer, so that delamination is prevented.
  • the gold surface can be soldered and used to attach the
  • Laser element may be provided on the heat input surface by soldering.
  • the heat exit surface may, for example, have said metallization in order to connect the heat exit surface of the heat spreader to the heat sink by soldering.
  • Metallization of the surface can also improve the stability and mechanical workability of the surface
  • the semiconductor laser may further comprise a lid.
  • the lid can have the function of a heat sink (second heat sink) or without thermal function.
  • the cover can be connected in a planar manner to the first heat sink via a joining surface by means of a heat-conducting joining agent layer, for example an electrically insulating heat-conducting adhesive, so that the heat can be dissipated from the cover to the first heat sink.
  • the cover can serve for power supply, for example as n-side contact terminal. With the help of the lid, a clamping force can be exerted on the laser element. This can be used for the frictional connection between the first contact surface and the heat input surface of the first heat spreader and / or for non-positive connection of the heat exit surface of the first heat spreader and the heat receiving surface of the heat sink or the
  • the clamping force can effect a frictional connection of the second contact surface to the heat input surface of the second heat spreader.
  • the laser element can frictionally with the first
  • Heat spreader and / or be connected to the second heat spreader Such a frictional connection can be advantageous for various reasons. Then namely can be dispensed with an example solderable coating of the heat spreader. In addition, the semiconductor laser can be disposed of more easily because the components are easier to separate than a solder joint.
  • the clamping force can be applied for example by a spring element, which may be formed for example as a spring washer or as a compression spring.
  • the use of a spring element is advantageous if the first heat spreader is plastically deformable or rigid. If the first heat spreader, however, is elastic, the clamping force can also be applied by itself. Then, the lid can be mechanically rigidly connected to the first heat sink, for example, without spring element. This connection can be made electrically insulating, so that the cover and the first heat sink to electrical
  • an insulating element for example an insulating disk or an insulating bush can be used.
  • the first angle a may preferably be between 10 ° and 90 °. Also preferably, it may be a right angle.
  • the thermal conductivity of the first heat spreader can have in each direction, which lies in a plane xy ' perpendicular to the direction z ' of the lowest thermal conductivity of the heat spreader, an approximately equal value, which is the maximum value of the direction-dependent
  • the semiconductor laser may additionally comprise at least one second laser element designed as a laser bar, which is arranged offset to the first laser element.
  • the second laser element can be electrically connected in parallel to the first laser element.
  • a common first heat spreader can be provided for both laser elements.
  • the second laser element may be connected in series with the first laser element.
  • a separate associated first heat spreader may be present for each laser element.
  • the laser element has a second contact surface which is in thermal contact with a heat input surface of the second heat spreader and the second heat spreader further comprises a heat exit surface, which is in thermal contact with a heat receiving surface of the second heat sink. Also in the second heat spreader, the heat exit surface parallel to
  • the maximum electrical conductivity of the heat spreader may be smaller than the electrical conductivity of a metal, which may be applied, for example, as a layer on the first contact surface of the laser element.
  • the maximum electrical conductivity of a TPG body can be 10 5 to 10 7 (ohm * m) -1
  • a gold layer can be an (isotropic) electrical
  • the maximum electrical conductivity of the cherriessp Schwarz stressess can thus for example 5 to 20 may be times lower than that of the metal layer, while a maximum thermal conductivity from 3 to 6 may be times higher than that of the metal layer.
  • Thermal conductivity of a gold layer may be, for example, 300 W (m * K), while the maximum thermal conductivity of a TPG body may be 1000 to 2000 W / (m * K). Therefore, the metal layer may be mainly provided for current spreading, while the
  • Heat spreader can be mainly provided for heat spreading.
  • a metal layer which may be applied to the first contact surface of the laser element, therefore, a particularly advantageous embodiment of the invention can be produced.
  • the lowest electrical conductivity cr m of the TPG heat spreader can even be smaller by a few orders of magnitude than its maximum electrical conductivity ⁇ ⁇ .
  • a m may have an amount of only 10 3 to 10 5 (ohm * m) -1 .
  • the thermal contact between the heat exit surface of the first heat spreader and the first heat sink can by means of a third heat spreader with anisotropic
  • Heat spreader is and a heat exit surface of the third heat spreader is in thermal contact with the heat receiving surface of the first heat sink. In this case, the direction of the lowest thermal conductivity of the third heat spreader perpendicular to
  • the direction of least heat conductivity of the third heat spreader may be different from the direction of least heat conductivity of the first heat spreader.
  • the thermal contact between the heat outlet surface of the second heat spreader and the second heat sink can be effected by means of a fourth heat spreader having anisotropic thermal conductivity in that the heat exit surface of the second heat spreader in thermal contact with a heat input surface of the fourth
  • Heat spreader is and a heat exit surface of the fourth heat spreader is in thermal contact with the heat receiving surface of the second heat sink. In this case, the direction of the lowest thermal conductivity of the fourth heat spreader perpendicular to
  • the fourth heat spreader may be oriented.
  • the direction of least heat conductivity of the fourth heat spreader may be different from the direction of least heat conductivity of the second heat spreader.
  • the first heat spreader may comprise or consist of graphite, for example pyrolytic graphite.
  • the heat spreader comprises or consists of highly oriented pyrolytic graphite.
  • the first heat spreader may have a thickness of 0, 1 mm to 10 mm, preferably 0.2 mm to 5 mm.
  • the laser element may be non-positively connected to the first heat spreader and / or the second heat spreader.
  • the first heat spreader may be subjected to pressure treatment prior to assembling the semiconductor laser of the present invention.
  • a later, for example, deformation of the heat spreader during assembly of the semiconductor laser can be prevented or greatly reduced.
  • settlement phenomena of the heat spreader in the finished assembled semiconductor laser can be avoided or limited.
  • the semiconductor laser will have good long-term stability, in particular with regard to the position of the emitter.
  • Another advantage of the pressure treatment is that the flatness of the surfaces, i. h the heat input surface and the heat outlet surface can be improved. This means that the roughness of said surfaces can be reduced.
  • the pressure treatment can be carried out by subjecting the heat spreader to a uniaxial pressure perpendicular to the heat input surface.
  • the pressure can be effected for example by a press with, for example, two flat surfaces, wherein a force in the normal direction is applied to the heat input surface.
  • the pressure can be maintained for a few seconds to several days.
  • the pressure can be either constant or pulsating.
  • the thickness of the heat spreader can decrease.
  • the pressure may preferably be higher than that occurring later in use in the semiconductor laser according to the invention, preferably at least three times as high.
  • the pressure treatment can lead to a compression of the material. By the pressure treatment, the deformability (compressibility) of the heat spreader can decrease or increase its hardness.
  • the pressure treatment can lead to an increase in electrical conductivity.
  • the pressure treatment can be combined with a heat treatment.
  • the second, third and / or fourth heat spreader can also be treated. Said pressure treatment is not only suitable for the heat spreader.
  • Heat spreader can be achieved.
  • the pressure treatment can also be done before the preparation of the geometric shape of the
  • the pressure treatment can also be done by rolling the material between two rolls.
  • the rolling technology may be particularly suitable for thin materials, for example, preferably thinner than 1 mm thickness, for example, carbon film with a thickness of 25 pm to 500 ⁇ .
  • an arrangement can be set up in which at least two of the laser elements are electrically connected in series.
  • Fig. 2 shows a first embodiment with existing heat spreading in the x direction in
  • Fig. 3 shows the first embodiment in front view
  • Fig. 4 shows the effect of the metal layer on the electric current density at the first
  • Fig. 5 shows a detail A in a detailed representation
  • Fig. 6 shows a second embodiment with suppressed heat spreading in the x direction in front view
  • Fig. 7 shows a third embodiment with a third heat spreader
  • Fig. 8 shows a fifth embodiment with a second heat spreader
  • Fig. 9 shows the fifth embodiment in exploded view
  • FIG. 10 shows a sixth exemplary embodiment in which a plurality of laser bars, each having an emitter, are electrically connected in parallel
  • FIGS. 2, 3 and 4 A first exemplary embodiment of a semiconductor laser according to the invention is shown in FIGS. 2, 3 and 4. To illustrate the essential features, the figures are not drawn to scale.
  • the semiconductor laser comprises a laser element 1, which, as shown in FIG. 2, emits laser radiation 1 2 in a direction defined as -y.
  • the laser element is a diode laser bar with multiple emitters, for example with 19 emitters.
  • FIG. 3 for the sake of clarity, only three emitters are shown, which each have a gain region 13, which corresponds in the illustrated view to the exit aperture.
  • the exit aperture is at the bottom of the chip
  • the first contact surface is thus the p-contact (anode) of the diode laser bar.
  • the laser element has on the first contact surface on a gold layer 9 with a thickness greater than 0.5 ⁇ for spreading or distribution of the electrical operating current.
  • the thickness of the gold layer can be for example 4 ⁇ and be prepared by electroplating.
  • the surface normal n of the first contact surface is oriented in the z-direction.
  • the semiconductor laser of the first embodiment further includes a first heat sink 17 and a second heat sink 22.
  • the semiconductor laser of the first embodiment further includes a first one
  • the thickness of the first heat spreader is 0.5 mm.
  • Thermal conductivity of the first heat spreader is at a first angle of 90 ° to
  • Heat spreader is thus in the longitudinal direction of the laser radiation in the laser bar (y direction). This y-direction is also the main propagation direction of the emergent laser beams 12.
  • the first contact surface 2 is in thermal contact with a heat input surface 1 of the first heat spreader 14.
  • the thermal contact is effected by the gold-plated first contact surface rests on the heat input surface and by a clamping force 26 surface
  • the heat input surface of the first heat spreader has a first
  • the laser element is thus non-positively connected to the first heat spreader.
  • the first heat spreader also has a
  • Heat exit surface 16 which is in thermal contact with a heat receiving surface 18 of the first heat sink 17. This thermal contact is effected in the same way by the clamping force 26.
  • the clamping force 26 is effected by a cover 22 which is fastened with screws 27.
  • the screws are equipped with spring elements 28 and mounted electrically insulated from the cover by means of insulating washers 29.
  • the lid is provided here without thermal function. But it could also be used as a second heat sink, if you installed a heat dissipation from the lid, for example, by water cooling, or if the lid thermally with the first Heat sink is connected.
  • the cover is made of copper and serves to supply power, so as n-side (substrate side) contact terminal for the laser bar, while the p-side electrical connection is made via the first heat sink.
  • the operating voltage is thus applied between the first heat sink 17 and the cover 22.
  • the operating current must therefore flow with a z-component over the first heat spreader 14.
  • a method for heat dissipation from the laser element is practiced, in which a heat spreading takes place in the x direction, as shown in Fig. 3.
  • a heat spreading takes place in the x direction, as shown in Fig. 3.
  • three vectors of the heat flux q are shown for an emitter 13, which represent the direction of the heat flow by way of example. Because of the orientation 25 of the anisotropic material of the heat spreader 14, the heat spread in the y direction is negligibly small.
  • the heat transfer through the heat spreader 14 takes place in the z-direction, i. the vectors q have a z-component, while the y-component is vanishingly small, as can be seen in FIG.
  • the heat spreading takes place mainly in the heat spreader 14 and only a small part in the metal layer 9, since the maximum value of the thermal conductivity of the
  • Heat spreader i. in y 'direction, is higher than the thermal conductivity of the metal layer.
  • Heat spreader i. in y 'direction.
  • the current path differs from the heat path described above according to FIG. 3.
  • the spreading or distribution of the operating current in the metal layer 9 thus causes the current flow in the z direction to be determined by the first
  • Heat spreader 14 has a higher cross-sectional area is available. As a result, the ohmic resistance and thus the power loss of the semiconductor laser can be reduced. From this consideration, the advantage of combining the heat spreader 14 according to the invention with a thick metallization layer 9 on the laser element becomes clear.
  • the laser bar 1 comprises a substrate 3, a light guiding layer 4, an active one Layer 5, a further light guide layer 4, a cover layer 6, a structured insulation layer 7, an electrode 8 (anode, p-side) and a gold layer 9.
  • the structured insulating layer 7 is applied, which is interrupted in the central region of the illustration is.
  • the region in which the insulation layer is interrupted has a constant width (extension in the x-direction) (which is independent of the y-coordinate), thereby defining a corresponding emitter strip of the laser bar.
  • the emitter width is ⁇ ⁇ on this structured
  • Insulation layer is the electrode 8, which was prepared by sputtering and has a thickness of less than 0.5 ⁇ . This electrode was galvanically strengthened, so that a
  • Gold layer 9 of 4 pm thickness has emerged.
  • the operating current is supplied from below via the first heat spreader 14.
  • the current flow is shown schematically by the arrows 10.
  • the insulating layer Due to the insulating layer, only certain regions of the active layer are electrically pumped so that the formation of the laser radiation is limited locally to fixed gain regions 13. Since the current is spread laterally (x-direction) in the metal layer 9, it can be cut in the shortest path, i. H. in the z-direction over the entire surface are passed through the heat spreader 14.
  • FIG. 1 A second embodiment of a semiconductor laser according to the invention is shown in FIG.
  • the direction z 'of the lowest thermal conductivity of the first heat spreader 14 is oriented perpendicular to the direction y profit areas.
  • the heat transfer through the heat spreader takes place in the z-direction. This is one of the two directions with maximum thermal conductivity.
  • Heat spreader is oriented in the direction of y. Therefore, a heat spreading in the y-direction can take place.
  • This embodiment is to be preferred if a homogeneous temperature distribution over the profit ranges is desired. Since the heat flow in the x-direction is minimal, it is avoided that the profit regions (emitters) are better cooled at the edges, respectively, than in the middle of the respective profit region. Thereby, the formation of thermal lenses in the resonators can be avoided.
  • a current spread in the metal layer 9 provided for this takes place in the same way as in the first embodiment.
  • FIG. 1 A third embodiment of a semiconductor laser according to the invention is shown in FIG. In contrast to the first embodiment, the thermal contact between the
  • the heat outlet surface of the first heat spreader is lying flat on a heat input surface of the third heat spreader. This is the heat output surface of the first
  • a heat exit surface of the third heat spreader is flat on a heat receiving surface of the first heat sink. Thereby, this heat exit surface of the third heat spreader is in thermal contact with the heat receiving surface of the first heat sink.
  • the direction z 'of the lowest heat conductivity of the third heat spreader is oriented perpendicular to the surface normal of the heat entrance surface of the third heat spreader, and the direction z' of the lowest heat conductivity of the third heat spreader 24 is different from the direction of least heat conductivity z 'of the first heat spreader 14.
  • the direction z 'of the first heat spreader is oriented in the direction -y, while the direction z' of the third heat spreader is oriented in the direction x.
  • the thermal contact between the heat outlet surface of the second heat spreader and the second heat sink can be effected by means of a fourth heat spreader with anisotropic thermal conductivity, characterized in that the heat exit surface of the second heat spreader in thermal contact with a heat input surface of the fourth heat spreader stands.
  • a heat exit surface of the fourth heat spreader is in thermal contact with the
  • Heat receiving surface of the second heat sink and the direction of least heat conductivity of the fourth heat spreader is oriented perpendicular to the surface normal of the heat input surface of the fourth heat spreader.
  • the direction of least heat conductivity of the fourth heat spreader is different from the direction of least heat conductivity of the second heat spreader.
  • Heat spreader is oriented in the direction x.
  • Direction z 'of the lowest thermal conductivity of the first heat spreader 14 thus includes a first angle «on 45 ° to the surface normal n of the heat input surface 1 5 of the first
  • Coordinate system xyz rotated about the x-axis.
  • the electric field -E is oriented in the z direction
  • the electric current density j in the heat spreader is adjacent to the z component also a y component.
  • the current flow j is therefore not parallel to the field strength vector E.
  • the plotted vector - j (opposite current direction) is as shown
  • Fig. 1 directed to the bottom right.
  • the heat flow q also has a z next to the component
  • FIG. 1 A fifth embodiment is shown in FIG.
  • the lid 22 is designed as a second heat sink. The heat dissipation from the laser bar occurs on the epitaxial side with a first
  • Heat spreader 19 and a second heat sink 22 are provided. Both heat spreader 14, 19 are designed in the manner according to the invention so that in each case a direction Z 'of the lowest thermal conductivity of the first and the second heat spreader each an angle «of more than 45 ° to the surface normal n of the heat input surface of the first heat spreader or to the surface normal n 2 of the second heat spreader includes. In an analogous manner, a heat flow q 2 then flows from the laser element 1 through the second heat spreader to the second heat sink (cover) 22.
  • Both heat sinks 17, 22 are made of copper.
  • the second heat sink 22 is connected by means of an electrically insulating istleitklebers 30 as a joining means with the first heat sink 17 surface. Therefore, the heat can be transferred from the second heat sink to the first heat sink.
  • the clamping force 26 between both heat sinks is maintained by the joining means 30 without requiring any external force for the operation of the semiconductor laser.
  • Fig. 9 shows an exploded view of the fifth embodiment. Here are the first
  • the surface 15 is the heat input surface, the surface 9 the
  • the surface 18 is the
  • the surface 20 is the heat input surface, the surface 21, the heat exit surface of the second heat spreader 19.
  • the surface 23 is the Heat receiving surface of the second heat sink 22.
  • the area designations apply equally to all embodiments.
  • FIG. 10 shows a sixth exemplary embodiment in which a plurality of laser bars 1, each having an emitter 13, are electrically connected in parallel.
  • the first heat spreader 14 is correspondingly wide (expanded in the x direction), so that a plurality of laser elements 1 can each be arranged offset in the direction x relative to one another.
  • Each laser bar 1 has only one emitting area (wide-band emitter) 13.
  • Such laser bars are also referred to as a single emitter. They are electrically contacted together via the first heat sink 17 and the cover 22.
  • first contact surface for example p contact
  • ab planes for example, a hexagonal graphite structure

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
  • Semiconductor Lasers (AREA)

Abstract

L'invention concerne un laser à semi-conducteur, comprenant un élément laser (1), un premier corps de diffusion thermique (14) présentant une conductivité thermique anisotrope et ayant une direction z' dans laquelle la conductivité thermique est la plus faible, et un premier dissipateur de chaleur (17), l'élément laser possédant une première surface de contact (2) qui est en contact thermique avec une surface d'entrée de chaleur du premier corps de diffusion thermique et la surface d'entrée de chaleur (15) du premier corps de diffusion thermique possédant une première normale n à la surface et le premier corps de diffusion thermique possédant en outre une surface de sortie de chaleur (16) qui est en contact thermique avec une surface de réception de chaleur (18) du premier dissipateur de chaleur. Selon l'invention, la direction z' du premier corps de diffusion thermique, dans laquelle la conductivité thermique est la plus faible, forme un premier angle α de plus de 5° par rapport à la normale n à la surface d'entrée de chaleur du premier corps de diffusion thermique.
PCT/EP2015/000092 2014-01-20 2015-01-20 Laser à semi-conducteur à dissipation de chaleur anisotrope Ceased WO2015106972A1 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111463654B (zh) * 2020-04-22 2021-07-20 常州纵慧芯光半导体科技有限公司 一种发光装置及其制造方法与应用
US20220037852A1 (en) * 2018-09-13 2022-02-03 Suzhou Lekin Semiconductor Co., Ltd. Surface emitting laser device and surface emitting laser apparatus having the same
CN115133394A (zh) * 2022-06-07 2022-09-30 潍坊华光光电子有限公司 一种半导体激光器高精度封装结构
CN115799974A (zh) * 2023-02-07 2023-03-14 度亘激光技术（苏州）有限公司 一种导热结构及其制备方法、间接导热结构

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102015115244A1 (de) * 2015-09-10 2017-03-16 Infineon Technologies Ag Kühlkörper mit graphen-lagen und elektronikbaugruppe
JP7035377B2 (ja) * 2017-03-27 2022-03-15 ウシオ電機株式会社 半導体レーザ装置
US11114817B2 (en) * 2017-03-27 2021-09-07 Ushio Denki Kabushiki Kaisha Semiconductor laser device
DE102018210142B4 (de) * 2018-06-21 2024-12-24 Trumpf Photonics, Inc. Diodenlaseranordnung und Verfahren zum Herstellen einer Diodenlaseranordnung
DE102018121857B4 (de) 2018-09-07 2023-05-11 Jenoptik Optical Systems Gmbh Vorrichtung zum Betreiben eines lichtemittierenden Halbleiterbauelements
DE112019003763B4 (de) 2018-10-15 2024-03-28 Panasonic Intellectual Property Management Co., Ltd. Systeme und verfahren gegen das pumpen von thermischen grenzflächenmaterialien in hochleistungslasersystemen
DE102019124993A1 (de) * 2019-09-16 2021-03-18 Jenoptik Optical Systems Gmbh Verfahren zum Herstellen einer Halbleiteranordnung und Diodenlaser
DE102021124129A1 (de) 2021-09-17 2023-03-23 OSRAM Opto Semiconductors Gesellschaft mit beschränkter Haftung Optoelektronisches halbleiterbauelement und optoelektronisches modul

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0590232A1 (fr) * 1992-09-28 1994-04-06 Mitsubishi Denki Kabushiki Kaisha Dispositif laser multiple à semi-conducteur et méthode de montage
EP1906496A2 (fr) * 2006-09-29 2008-04-02 OSRAM Opto Semiconductors GmbH Laser semi-conducteur et son procédé de fabrication
WO2011106771A1 (fr) * 2010-02-26 2011-09-01 Graftech International Holdings Inc. Gestion thermique de projecteurs portatifs

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB991581A (en) * 1962-03-21 1965-05-12 High Temperature Materials Inc Expanded pyrolytic graphite and process for producing the same
US5863467A (en) * 1996-05-03 1999-01-26 Advanced Ceramics Corporation High thermal conductivity composite and method
US6075701A (en) * 1999-05-14 2000-06-13 Hughes Electronics Corporation Electronic structure having an embedded pyrolytic graphite heat sink material
US6661317B2 (en) * 2002-03-13 2003-12-09 The Boeing Co. Microwave monolithic integrated circuit assembly with multi-orientation pyrolytic graphite heat-dissipating assembly
US7220485B2 (en) 2003-09-19 2007-05-22 Momentive Performance Materials Inc. Bulk high thermal conductivity feedstock and method of making thereof
JP5612471B2 (ja) * 2007-09-07 2014-10-22 スペシャルティ ミネラルズ （ミシガン） インコーポレーテツド 層状熱拡散器およびその製造方法
DE102008026229B4 (de) 2008-05-29 2012-12-27 Jenoptik Laser Gmbh Wärmeübertragungsvorrichtung zur doppelseitigen Kühlung eines Halbleiterbauelementes
US8085531B2 (en) * 2009-07-14 2011-12-27 Specialty Minerals (Michigan) Inc. Anisotropic thermal conduction element and manufacturing method
DE102009040835A1 (de) 2009-09-09 2011-03-10 Jenoptik Laserdiode Gmbh Verfahren zum thermischen Kontaktieren einander gegenüberliegender elektrischer Anschlüsse einer Halbleiterbauelement-Anordnung
JP5421751B2 (ja) 2009-12-03 2014-02-19 スタンレー電気株式会社 半導体発光装置
US8681829B2 (en) 2011-08-29 2014-03-25 Intellectual Light, Inc. Compression mount for semiconductor devices, and method
DE102011055891B9 (de) 2011-11-30 2017-09-14 Osram Opto Semiconductors Gmbh Halbleiterlaserdiode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0590232A1 (fr) * 1992-09-28 1994-04-06 Mitsubishi Denki Kabushiki Kaisha Dispositif laser multiple à semi-conducteur et méthode de montage
EP1906496A2 (fr) * 2006-09-29 2008-04-02 OSRAM Opto Semiconductors GmbH Laser semi-conducteur et son procédé de fabrication
WO2011106771A1 (fr) * 2010-02-26 2011-09-01 Graftech International Holdings Inc. Gestion thermique de projecteurs portatifs

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220037852A1 (en) * 2018-09-13 2022-02-03 Suzhou Lekin Semiconductor Co., Ltd. Surface emitting laser device and surface emitting laser apparatus having the same
US12003075B2 (en) * 2018-09-13 2024-06-04 Suzhou Lekin Semiconductor Co., Ltd. Surface emitting laser device and surface emitting laser apparatus having the same
CN111463654B (zh) * 2020-04-22 2021-07-20 常州纵慧芯光半导体科技有限公司 一种发光装置及其制造方法与应用
CN115133394A (zh) * 2022-06-07 2022-09-30 潍坊华光光电子有限公司 一种半导体激光器高精度封装结构
CN115799974A (zh) * 2023-02-07 2023-03-14 度亘激光技术（苏州）有限公司 一种导热结构及其制备方法、间接导热结构

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