DE102021211000B4 - Semiconductor laser chip with at least one protruding web region - Google Patents

Abstract

The invention relates to a semiconductor laser chip for emitting laser radiation, comprising: an active layer (2) with a web (10) which has a strip-shaped web region (10a) with a width d that is preferably constant in the lateral direction (X), wherein at least one web region (10b, 10b') projecting laterally beyond the strip-shaped web region (10a) adjoins a first and/or a second lateral edge (12a, 12b) of the strip-shaped web region (10a). A length of the laterally projecting web region (10b, 10b') in the longitudinal direction (Y) increases from a first length L1 at the first or second lateral edge (12a, 12b) of the strip-shaped web region (10b, 10b') to a second length L2, wherein: L2> 1.2 L1, preferably L2> 1.3 L1. The laterally projecting web region(s) (10b, 10b') are preferably trapezoidal in shape. Two mirror surfaces (9a, 9b) are formed on two opposite sides of the active layer (2). The strip-shaped web region (10a) of the web (10) borders on the mirror surfaces (9a, 9b). The mirror surface (9a, 9b) does not border on the projecting web region (10b, 10b').

Description

The present invention relates to an (edge-emitting) semiconductor laser chip (or a laser diode) for emitting laser radiation, comprising: a (laser) active (semiconductor) layer with a (wave-guiding) ridge, which has a strip-shaped ridge region with a preferably constant width d, wherein a first and/or a second lateral edge of the strip-shaped ridge region is adjoined by at least one ridge region that protrudes laterally (i.e. in the lateral direction) beyond the strip-shaped ridge region. The ridge typically extends along the (main) propagation direction of the laser radiation emitted by the edge-emitting semiconductor laser chip (longitudinal direction). The width d of the strip-shaped ridge region can vary depending on the position in the longitudinal direction, but the width d of the strip-shaped ridge region is preferably constant in the longitudinal direction.

It is from the DE 10 2013 220 641 A1 A semiconductor laser is known which comprises a base body and a ridge structure arranged on the base body.

The ridge structure serves to push out dislocations of a fracture surface from a central area of an active surface. Further applications are known from the US 2017/0047480 A1 and the DE 10 2016 113 071 A1 known.

A semiconductor laser (chip) typically has an active region or active layer that serves as the gain medium, and waveguide/cladding layers that surround the active layer. The gain medium is typically formed by a semiconductor material with a direct band gap and is usually undoped, while the surrounding waveguide/cladding layers are doped with p-type or n-type dopants. For efficient laser operation, a material with a lower band gap energy and higher refractive index is selected as the active gain material than is the case with the materials of the surrounding waveguide/cladding layers. In this way, a field-confining waveguide is formed in the vertical direction (perpendicular to the plane with the p-n junction).

The laser cavity of such a semiconductor laser chip, also called a Fabry-Perot cavity, is formed by a pair of parallel mirrors or mirror surfaces that are formed at the edges of the gain medium or the active semiconductor layer. The mirror surfaces can be created by simply cutting or slicing the crystal planes perpendicular to the plane containing the laser cavity. The resulting interfaces between the crystal and the ambient air can themselves provide the necessary reflectivity to maintain the laser oscillations. To maximize the output power of the laser, the mirror reflectivity is often set to less than 10% on the output facet and to more than 90% on the rear facet by depositing a sequence of dielectric layers on the respective facet or mirror surface.

The key phenomenon responsible for laser emission is the generation of light by radiative recombination of charge carriers (i.e. electrons and holes) in the active region or active layer. The generated light is partly emitted through the (mirror) facet into the surrounding air and partly reflected back into the laser cavity, where it is amplified by stimulated emission. To ensure the amplification of the light, it is necessary that a sufficient number of charge carriers are injected into the amplification region by an external electrical input power.

In so-called gain-guided semiconductor lasers, the current is supplied through an aperture (opening) defined by a dielectric insulator surrounding the aperture or by ion implantation. In index-guided semiconductor lasers, a ridge is formed by etching away semiconductor layers and the current is supplied through the top of the ridge. Therefore, only those optical modes that propagate under the current aperture or ridge (and the area covered by the so-called current expansion) are amplified. The number of laser modes can be controlled by adjusting the width of the current aperture or ridge. In the following description, the current aperture in gain-guided semiconductor lasers is also referred to as a ridge for simplicity. The current aperture or the ridge in the laser-active layer typically differs from a surrounding area outside the ridge in that the surrounding area has a doping or in that the material of the active layer has been etched away in the surrounding area.

wobei η_slope die (Steigungs-)Effizienz, I den injizierten Strom und I_thr die Stromschwelle bezeichnen. Der Bruchteil der zugeführten elektrischen Leistung, der in Nutzlicht resultiert, wird auch als Leistungs-Konversions-Effizienz („Power Conversion Efficiency“, PCE) bezeichnet. Die restliche Eingangsleistung wird in die Vorrichtung (den Halbleiterlaserchip) dissipiert und führt zu unvorteilhafter Aufheizung der Vorrichtung und ggf. zu nachfolgendem thermischen Überrollen („thermal rollover“).In semiconductor lasers, a portion of the injected current is converted into optical output power P _out according to the following formula: $${\text{P}}_{\text{out}}={\mathrm{\eta }}_{\text{slope}}\left(\text{I}-{\text{I}}_{\text{thr}}\right),$$

where η _slope is the efficiency, I the injected current and I _thr the current threshold. The fraction of the supplied electrical power that results in useful light is also called the power Conversion efficiency (“Power Conversion Efficiency” (PCE). The remaining input power is dissipated into the device (the semiconductor laser chip) and leads to unfavorable heating of the device and possibly to subsequent thermal rollover.

wobei M² _lat die laterale Strahlqualität, M² _vert die vertikale Strahlqualität und λ die Wellenlänge bezeichnen.The brightness or brilliance B of a laser is defined as $$\text{B}={\text{P}}_{\text{out}}/\left({\text{<figure-callout id="2" label="M" filenames="DE102021211000B4\_0003.png,DE102021211000B4\_0004.png" state="{{state}}">M</figure-callout>}}^2{}_{\text{<figure-callout id="2" label="lat M" filenames="DE102021211000B4\_0003.png,DE102021211000B4\_0004.png" state="{{state}}">lat</figure-callout>}}{\text{M}}^{}{}^2{}_{\text{vert}}{\mathrm{\lambda }}^2\right),$$

where M ² _lat is the lateral beam quality, M ² _{vert is} the vertical beam quality and λ is the wavelength.

Many industrial applications only require high output power. According to Eq. (1), high output power can be achieved by increasing the injected current, which linearly increases the optical output power before thermal effects dominate. One concrete way to increase the output power is to use a laterally wide ridge to inject more current into the device. A wide ridge is also beneficial to create small electrical and thermal resistances, which reduce device heating and enable high output power, high PCE, and improved reliability of the semiconductor laser chip.

For applications with high brightness, in addition to high output power, good beam quality is an essential factor. The beam quality M ² in Eq. (2) depends essentially on the number of laser modes. Emission of the fundamental mode alone leads to a nearly diffraction-limited laser beam with M ² ∼ 1. The beam quality deteriorates as the number of laser modes increases. Conventional high-power semiconductor lasers usually use epitaxial layer structures that only excite the fundamental mode in the vertical direction, so that M ² _vert ∼ 1 is ensured. The wide ridge required for high output powers supports the propagation of many laser modes, which leads to a deterioration of the beam quality M ² _lat in the lateral direction. This impairs the brightness, which makes the use of semiconductor lasers difficult in many industrial applications.

Considering the mode distributions in the laser waveguide, different techniques can be considered to achieve good lateral beam quality. A large part of the fundamental mode, especially the region of its maximum intensity, is concentrated in the center of the ridge, while significant parts of the intensity of the higher order modes are located away from the central region of the ridge.

The simplest way to obtain good beam quality is to use a narrow ridge waveguide that pumps only the fundamental mode and favors it for emission over the higher order modes. However, the small dimension of the ridge width limits the achievable output power as well as the PCE (at high output power) and reduces the reliability of the device.

In the so-called tapered lasers, two separate sections of the ridge waveguide are used to achieve high output power and good lateral beam quality at the same time. In a first section with a small ridge width, only the fundamental mode is guided and the higher modes are filtered out. The fundamental mode is then expanded to a larger area in a second, beveled or tapered section to provide high brightness. However, tapered lasers suffer from a very strong astigmatism that is unfavorable for practical applications and depends on the operating current.

An alternative approach to reduce the number of lasing modes is to increase the lasing thresholds of the higher order modes and/or reduce the modal gain of the higher modes relative to the fundamental mode in a ridge waveguide with a wide ridge supporting multiple lateral modes. This can be achieved by increasing the losses of the higher order modes and reducing their overlap with the injected carriers. The larger thresholds and/or lower modal gain reduce the contributions of the higher order modes to the lasing emission, thus achieving improved beam quality.

Recently, so-called corrugated structures have been proposed to increase the optical losses of the higher order modes in wide ridge waveguides. The corrugated structures form a repetition of e.g. triangular, rectangular or herringbone-shaped structures on both sides of the edge of the ridge along its longitudinal direction, cf. for example US 8 396 091 B2 or the article "Beam quality improvement of highpower semiconductor lasers using laterally inhomogeneous waveguides", MJ Miah, S.Strohmaier, G. Urban and D. Bimberg, Appl. Phys, Lett. 113 (22), 221107 (2018) .

The corrugated structures described there typically extend from a strip-shaped ridge region with a constant width in the lateral direction outwards, ie they protrude beyond the ridge region of constant width. The corrugated structures are thus comparatively far away from the centre or middle of the ridge in the lateral direction. Therefore, only the higher order modes experience scattering losses in the corrugated structures when propagating along the longitudinal direction, while the fundamental mode remains almost unaffected. In this way, an unequal treatment between the threshold values of the fundamental mode and the higher modes is achieved in favour of the fundamental mode.

In the DE 10 2008 014 093 A1 describes an edge-emitting semiconductor laser chip which has at least one contact strip and an active zone in which electromagnetic radiation is generated during operation of the semiconductor laser chip. The semiconductor laser chip comprises at least two current barriers which are arranged on different sides of the contact strip and which extend along the contact strip. The greatest distance between at least one of the current barriers and the contact strip is selected such that the ratio of the greatest distance to the width of the contact strip is greater than one. The current barriers are intended to prevent current expansion in the semiconductor layers between the active zone and the contact strip(s). The current barriers can form trenches which are etched starting from the contact strip or from a contact layer to at least below the active layer.

task of the invention

The invention is based on the object of providing a semiconductor laser chip which makes it possible to emit laser radiation with a high brightness (brilliance).

subject matter of the invention

This object is achieved according to a first aspect by a semiconductor laser chip of the type mentioned at the outset, in which a length of the laterally projecting web region increases in the longitudinal direction starting from a first length L ₁ at the first or second lateral edge of the strip-shaped web region to a second length L ₂ , where: L ₂ > 1.2 L ₁ , preferably L ₂ > 1.3 L ₁ . Furthermore, two mirror surfaces are formed on two opposite sides of the active layer. The strip-shaped web region of the web borders on the mirror surfaces. The mirror surface does not border on the projecting web region.

In the semiconductor laser chip according to the invention, it is proposed to use structures in the form of (butterfly) wings instead of corrugated or wave-shaped structures that protrude laterally beyond the strip-shaped web region. Such a laterally protruding web region widens, starting from the section at which the protruding web region adjoins the strip-shaped web region (with length L ₁ ), in the lateral direction to a second, greater length L ₂ , which is further spaced from the strip-shaped web region or from its center in the lateral direction than the section with the first length L ₁ . The second length L ₂ can be formed in particular on the outer edge of the protruding web region in the lateral direction, which can extend parallel to the outer edge of the strip-shaped web region.

In principle, it is also possible for the laterally projecting web region to have, in addition to a section that widens from the first length L ₁ to the second length L ₂ , a section that is further away from the center of the web in the lateral direction and whose length decreases in the longitudinal direction starting from the second length L _2. The widening of the projecting web region from the first length L ₁ to the second length L ₂ preferably takes place continuously. The lateral edges or legs of the projecting web region can run in a straight line starting from the section of the first or second lateral edge, but it is also possible for the lateral edges to have a curve. The first length L ₁ preferably represents a minimum length and the second length L ₂ preferably represents a maximum length of the projecting web region.

The protruding bridge region can be formed by etching away the semiconductor layer(s) when producing the bridge. The laterally protruding bridge region and the strip-shaped bridge region form a continuous, monolithic structure. In contrast to the strip-shaped bridge region, which typically extends in the longitudinal direction over the entire length of the active layer and which is directly adjacent to the mirror surfaces, this is generally not the case with the protruding bridge region. In contrast to the strip-shaped bridge region, the at least one laterally protruding bridge region is also generally not electrically pumped.

Similar to the corrugated structures, the wing-shaped structures or ridge regions allow the introduction of additional losses of the higher order modes to ensure the dominance of the fundamental mode or the lower order modes in the output laser beam. The active layer can only have a single supernatant protruding web region on the first lateral edge and/or a single protruding web region on the second lateral edge of the strip-shaped web region. To increase performance, several protruding web regions can be formed on a respective edge, which are arranged next to one another in the longitudinal direction.

In addition, two (parallel) mirror surfaces are formed on two opposite sides of the active layer, which is adjacent to the strip-shaped web region of the web. The two mirror surfaces typically run in parallel planes that extend in the lateral direction, i.e. transversely to the (main) propagation direction of the laser radiation. In the simplest case, the mirrors or mirror surfaces are formed by splitting the semiconductor material or cutting it along its crystal planes. It is possible that additional reflective layers are applied to the side surfaces or edges of the active layer in order to increase the reflectivity of the mirror surfaces or to adjust it accordingly. As a rule, one of the two (possibly coated) mirror surfaces is partially transmissive and is used to couple out the laser radiation emitted by the semiconductor laser chip, while the other (possibly coated) mirror surface is highly reflective.

In one embodiment, the laterally projecting bridge region is trapezoidal and preferably runs mirror-symmetrically to the lateral direction. In this case, a section of the lateral edge of the strip-shaped bridge region forms the shorter base side of the trapezoid (with the first length L ₁ ) and the parallel, longer base side has the second length L ₂ . It is understood that other geometries of the projecting bridge region are also possible. For example, the bridge region can have a section that widens to the second length L ₂ , which is adjacent to a narrowing section. The longer base side of the trapezoidal bridge region can also have a corrugated geometry or a wave shape. A straight, long base side (with length L ₂ ) of the trapezoidal projecting bridge region that runs parallel to a lateral edge of the bridge that is aligned in the longitudinal direction has proven to be advantageous, since in this way no unwanted effects such as astigmatism or the like occur. It has also proven to be advantageous if the trapezoidal protruding web area is isosceles, ie if it has an axis of symmetry running in the lateral direction (perpendicular to the base sides), which forms a central axis of the protruding web area.

In a further embodiment, the two legs of the trapezoidal projecting web region are aligned at an angle of at least 30° and not more than 70° to the first or second lateral edge of the strip-shaped web region. The alignment of the legs of the projecting web region at angles within this interval has proven to be beneficial for increasing the losses of the higher modes.

In a further embodiment, the laterally projecting web region has a width d _S in the lateral direction for which d _S > 0.5 d applies. The use of a laterally projecting web region that has a comparatively large width has proven to be advantageous for suppressing higher modes.

In one embodiment, the width d of the strip-shaped ridge region is between 10 µm and 250 µm, preferably between 100 µm and 250 µm. The width d of the strip-shaped ridge region is generally smaller than that of a conventional ridge waveguide with a wide ridge, but larger than that of a ridge waveguide with a narrow ridge. The total width of the ridge, ie the sum of the width d of the strip-shaped ridge region and the width d _S of the two laterally projecting ridge regions (d + d _S or d + 2 d _S ) is in the order of magnitude of conventional ridge waveguides with a wide ridge.

In a second aspect of the invention, which can in particular be combined with the first aspect, the active layer has at least one refractive index variation region which is arranged adjacent to the first lateral edge or to the second lateral edge of the strip-shaped web region, wherein the refractive index variation region has a maximum distance A _max from the first lateral edge or to the second lateral edge, which is given by A _max / d < 0.3, preferably A _max / d < 0.2.

The suppression of the higher order modes can be further enhanced by expanding the higher order modes from the center of the strip-shaped ridge region into the laterally projecting ridge region(s). The expansion of the higher order modes reduces their confinement factor, i.e. the fraction of the optical modes located under the strip-shaped, central ridge region that is electrically pumped. As a result, the modal amplification of the higher order modes is reduced. The provision of at least one refractive index variation region is not only advantageous in the case that the projecting ridge regions are wing-shaped or widen starting from the first length L ₁ , but but also with projecting web areas that are designed in a different way, for example with the triangular, herringbone-shaped or rectangular projecting web areas described above.

A modulation or a variation of the refractive index adjacent to a respective lateral edge of the strip-shaped ridge region can expand the higher modes located there in the lateral direction and shift them away from the center of the strip-shaped ridge region. It has proven to be advantageous if the refractive index variation region is formed adjacent to the edge of the strip-shaped ridge region, i.e. if it does not extend further away from the edge of the strip-shaped ridge region than is described by the above formula.

The modulation or variation of the refractive index in the lateral direction, i.e. perpendicular to the longitudinal direction, which corresponds to the (main) propagation direction of the emitted laser radiation, can be generated by generating lateral structures adjacent to a respective edge of the strip-shaped ridge region. A respective refractive index variation region can be formed within the strip-shaped ridge region, i.e. within the two lateral edges of the strip-shaped ridge region and/or within the protruding (in particular wing-shaped) ridge region(s). Since the protruding ridge regions are generally not electrically pumped, the expansion of the higher-order laser modes into the protruding ridge region(s) leads not only to scattering losses but also to an increase in absorption, which suppresses their contribution to the laser emission.

The modulation of the refractive index can be generated by lateral structures that are formed or arranged periodically or aperiodically in the lateral direction in order to generate a periodic or aperiodic refractive index variation in the lateral direction. The refractive index can vary continuously or discontinuously in the refractive index variation range in the lateral direction, e.g. in the manner of a rectangular profile.

It is generally advantageous if no additional refractive index variation occurs in the longitudinal direction in the refractive index variation region, i.e. if the lateral variation of the refractive index in the longitudinal direction is constant or changes according to the width of the strip-shaped ridge region. Even in the case of a strip-shaped ridge region whose width d changes depending on the position in the longitudinal direction, the following applies at every point: A _max / d < 0.3, preferably < 0.2. In the following examples, however, it is assumed that the strip-shaped ridge region has a constant width in the lateral direction. In this case, the lateral structures in the refractive index variation region generally extend in the longitudinal direction parallel to the strip-shaped ridge region, i.e. at a constant distance from the strip-shaped ridge region or from the respective lateral edge to which the respective refractive index variation region is arranged adjacent.

In one embodiment, the active layer has at least two refractive index variation regions. At least one of the refractive index variation regions is formed in at least one laterally projecting ridge region, wherein the at least one refractive index variation region preferably does not extend in the longitudinal direction beyond the first length L ₁ of the laterally projecting ridge region. In this embodiment, only refractive index variation regions are formed in the unpumped, respective laterally projecting ridge regions. In the event that at least one laterally projecting ridge region is formed at the first edge and at least one laterally projecting ridge region is formed at the second edge of the strip-shaped ridge region, a single refractive index variation region can be formed in the laterally projecting ridge region adjacent to the first edge of the ridge or in the laterally projecting ridge region adjacent to the second edge of the ridge, ie the refractive index variation regions can be limited to the surroundings of the first edge or the second edge. Alternatively, a first refractive index variation region may be formed in (at least one) laterally projecting ridge region adjacent to the first edge of the ridge and a second refractive index variation region may be formed in (at least one) laterally projecting ridge region adjacent to the second edge of the ridge.

In general, it has proven to be advantageous if a respective refractive index variation region that is formed in a laterally projecting web region does not extend in the longitudinal direction beyond the first length L _1. In particular, it has proven to be advantageous if the extension of a respective refractive index variation region that is formed within the laterally projecting web region corresponds to the first length L ₁ .

In one embodiment, the at least one refractive index variation region is formed between the first edge and the second edge of the strip-shaped ridge region. In this embodiment, the refractive index variation region(s) is/are formed only within the strip-shaped ridge region, ie it is no refractive index variation region outside the strip-shaped ridge region. In this embodiment, refractive index variation regions can be formed only adjacent to the first edge of the strip-shaped ridge region or only adjacent to the second edge of the strip-shaped ridge region. Alternatively, (at least) a first refractive index variation region can be formed adjacent to the first edge of the strip-shaped ridge region and (at least) a second refractive index variation region can be formed adjacent to the second edge of the strip-shaped ridge region.

In a further alternative embodiment, at least one refractive index variation region is formed between the first edge and the second edge of the strip-shaped ridge region and at least one refractive index variation region is formed in the at least one laterally projecting ridge region outside the two edges of the strip-shaped ridge region. In this embodiment, at least two refractive index variation regions are present, of which at least one is formed within the strip-shaped ridge region and at least one in the laterally projecting ridge region outside the strip-shaped ridge region. In principle, it is possible for the active layer to have (exactly) two refractive index variation regions, of which a first is formed adjacent to the first/second edge within the strip-shaped ridge region and a second is formed in a projecting ridge region laterally adjacent to the first/second edge.

Preferably, a protruding web region is formed both on the first edge of the strip-shaped web region and on the second edge of the strip-shaped web region. In this case, it has proven to be advantageous if (at least) one refractive index variation region within the strip-shaped web region and (at least) one refractive index variation region outside the strip-shaped web region are formed on both the first edge and the second edge.

In a further embodiment, at least one refractive index variation region, which is formed between the first edge and the second edge of the strip-shaped ridge region, extends over the entire extent of the strip-shaped ridge region in the longitudinal direction. In this case, the refractive index variation region(s) extend over the entire length of the resonator, i.e. between the two mirrors or mirror surfaces, to which the ridge typically adjoins with the strip-shaped ridge region, but generally not with the (unpumped) protruding ridge region(s).

It is not absolutely necessary, but can be advantageous, if the refractive index variation region has a minimum distance A _min from the first lateral edge or from the second lateral edge, which is given by A _min / d > 0.05, preferably A _min / d > 0.1. The latter is particularly advantageous in the case that the refractive index variation region is formed within the strip-shaped ridge region and extends into at least one section of the lateral edge that is formed outside the first length L ₁ , on which the respective laterally projecting ridge region is formed. In the section of the strip-shaped ridge region that is not adjacent to a laterally projecting ridge region, a variation in the refractive index is generated directly at the edge of the strip-shaped ridge region anyway, since the refractive index within the ridge is greater than the refractive index in a surrounding area outside the ridge in order to fulfill the desired waveguide function of the ridge. It is therefore not necessary - but also not excluded - that the refractive index variation begins immediately at the edge of the strip-shaped ridge area; rather, in this case it is usually sensible if the refractive index variation area only begins at a (small) distance from the edge of the strip-shaped ridge area.

In an alternative embodiment, the at least one refractive index variation region formed between the first edge and the second edge of the strip-shaped ridge region does not extend in the longitudinal direction beyond the first length L ₁ of the laterally projecting ridge region on the first or second lateral edge. In particular, the length of the refractive index variation region can correspond to the (first) length L ₁ of the laterally projecting ridge region. This embodiment represents an alternative to the embodiment described above, in which the at least one refractive index variation region extends in the longitudinal direction over the entire extent of the resonator.

In an alternative embodiment, at least two laterally projecting web regions adjoin the first edge of the strip-shaped web region and/or at least two laterally projecting web regions adjoin the second edge of the strip-shaped web region, wherein preferably the at least one refractive index variation region formed between the first edge and the second edge of the strip-shaped web region extends in the longitudinal direction only over the respective first length L ₁ of the at least two laterally projecting ridge regions and over a section between the laterally projecting ridge regions on the first lateral edge or on the second lateral edge. In this case, the at least one refractive index variation region extends along or between the laterally projecting ridge regions, but not beyond them, ie not to the respective end of the resonator on the first or second mirror surface. In this embodiment, no refractive index variation region is formed in the section between the respective end of the resonator and the adjacently arranged laterally projecting ridge region.

It is understood that combinations of refractive index variation regions other than those described above are also possible. For example, the active layer can have three refractive index variation regions, two of which are formed on opposite sides of one of the edges of the strip-shaped ridge region within the ridge or in a laterally projecting ridge region, and the third of which is formed on the other edge of the strip-shaped ridge region either within the strip-shaped ridge region or in the laterally projecting ridge region.

The refractive index variation region can generally be created by etching the ridge at periodic or aperiodic intervals (in the lateral direction). By etching the ridge, trenches can be created that have a V-shaped or possibly a rectangular cross-sectional profile. The trenches or the lateral structures can extend in the vertical direction over the entire height of the active layer, but this is not absolutely necessary in order to create a refractive index variation.

In one embodiment, the refractive index variation region has at least one lateral structure, which is preferably designed as a trench, wherein the refractive index variation region in particular has at least two lateral structures with a predetermined width, which are separated from one another by a respective intermediate region that has a predetermined width. The lateral structure has a refractive index that differs from the refractive index in the surroundings (in the lateral direction), i.e. from the - typically constant - refractive index of the ridge. The lateral structure is preferably designed as a trench that is etched into the semiconductor material of the active layer. Such a trench can in particular have a V-shaped or a rectangular cross-section in the lateral direction. In particular, in the event that the trench is formed in the unpumped, laterally protruding ridge region, the trench can optionally be filled with an absorbent material. It is understood that the lateral structures can also be produced in other ways, for example by (different) doping of the semiconductor material of the active layer or by material processing, e.g. by means of a pulsed laser or the like.

The refractive index variation region preferably has at least two lateral structures with a predetermined width, wherein the at least two lateral structures are separated from one another by a respective intermediate region which has a predetermined width. The intermediate region (sub-bridge) can be designed like the rest of the bridge. In this case, the refractive index is only varied in the region of the lateral structures, for example at the trenches, which is otherwise usually constant in the lateral direction within the bridge, i.e. both within the strip-shaped bridge region and within the laterally projecting bridge region.

The widths of the lateral structures of the refractive index variation region can each be the same size and the widths of the intermediate regions of the refractive index variation region can each be the same size. In this way, a refractive index variation region with a periodic structure is realized.

Alternatively, the widths of at least two of the lateral structures of the refractive index variation region can be different and/or the widths of at least two of the intermediate regions of the refractive index variation region can be different. In this way, a refractive index variation region with an aperiodic structure can be realized.

In a further embodiment, the semiconductor laser chip additionally comprises at least one p-doped waveguide layer and at least one n-doped waveguide layer, between which the active layer is arranged. As described above, the active layer - at least in the region of the ridge - is typically undoped, so that the waveguide layers and the active layer form a p-i-n junction. Both the waveguide layers and the active layer are applied to a substrate, which is usually n-doped.

It is understood that the semiconductor laser chip may have further layers. In particular, in a gain-guided semiconductor laser chip, the current is typically supplied through an aperture or opening formed by a dielectric insulator or by ion implantation is defined. In this case, a contact layer in the form of a contact strip for electrical contacting is typically formed on the top side of the semiconductor laser chip, the width of the contact strip generally corresponding to the width of the strip-shaped ridge region. In index-guided lasers, the ridge is formed by etching away semiconductor layers and the current is supplied through the top side of the ridge. In this case, the contact layer can be applied over the entire surface of the top side of the semiconductor laser chip. Typically, a further contact layer is formed on the underside of the substrate in order to inject a current into the active layer with the aid of a current or voltage source, which serves to pump the semiconductor material present there.

Further advantages of the invention emerge from the description and the drawing. Likewise, the features mentioned above and those listed below can be used individually or in combination in any desired way. The embodiments shown and described are not to be understood as an exhaustive list, but rather are exemplary in nature for the description of the invention.

• 1 eine schematische Darstellung einer beispielhaften Aufbaus eines Halbleiterlaserchips, der eine (laser-)aktive Schicht aufweist,
• 2 eine schematische Darstellung einer lateralen Intensitätsverteilung einer fundamentalen Mode und von zwei höheren Moden in der aktiven Schicht des Halbleiterlaserchips,
• 3a,b Darstellungen einer aktiven Schicht des Halbleiterlaserchips mit einem Steg mit herkömmlicher (breiter) Stegbreite,
• 4a,b Darstellung analog zu 3a,b mit einem Steg, der eine deutlich geringere Stegbreite aufweist,
• 5 eine Darstellung analog zu 3 mit einem Steg, der einen Stegabschnitt mit der geringen Stegbreite von 4a,b sowie einen spitz zulaufenden Abschnitt aufweist,
• 6a,b Darstellungen eines Stegs mit einer Mehrzahl von dreieckförmigen Stegbereichen, die über einen zentralen, streifenförmigen Stegbereich überstehen,
• 7a,b Darstellungen analog zu 6a,b mit zwei trapezförmigen Stegbereichen, die seitlich über einen zentralen, streifenförmigen Stegbereich überstehen,
• 8a,b Darstellungen analog zu 7a,b mit zwei Brechungsindex-Variationsbereichen, die benachbart zu einem jeweiligen Rand des streifenförmigen Stegbereichs in den trapezförmigen Stegbereichen gebildet sind,
• 9a,b Darstellungen analog zu 8a,b mit zwei Brechungsindex-Variationsbereichen, die benachbart zu einem jeweiligen Rand des streifenförmigen Stegbereichs innerhalb des streifenförmigen Stegbereichs gebildet sind,
• 10a,b Darstellungen analog zu 7a,b und 8a,b mit vier Brechungsindex-Variationsbereichen, die benachbart zu einem jeweiligen Rand des streifenförmigen Stegbereichs in dem streifenförmigen Stegbereich bzw. in den trapezförmigen Stegbereichen gebildet sind,
• 11a,b Darstellungen analog zu 9a,b, bei denen sowohl am ersten als auch am zweiten Rand des streifenförmigen Stegbereichs jeweils zwei überstehende trapezförmige Stegbereiche gebildet sind.

They show:

• 1 a schematic representation of an exemplary structure of a semiconductor laser chip having a (laser-)active layer,
• 2 a schematic representation of a lateral intensity distribution of a fundamental mode and two higher modes in the active layer of the semiconductor laser chip,
• 3a ,b Representations of an active layer of the semiconductor laser chip with a ridge with conventional (wide) ridge width,
• 4a ,b Representation analogous to 3a ,b with a web that has a significantly smaller web width,
• 5 a representation analogous to 3 with a web that has a web section with the small web width of 4a ,b and a tapered section,
• 6a ,b Representations of a web with a plurality of triangular web areas that protrude beyond a central, strip-shaped web area,
• 7a ,b Representations analogous to 6a ,b with two trapezoidal web areas that protrude laterally over a central, strip-shaped web area,
• 8a ,b Representations analogous to 7a ,b with two refractive index variation regions formed adjacent to a respective edge of the strip-shaped ridge region in the trapezoidal ridge regions,
• 9a ,b Representations analogous to 8a ,b with two refractive index variation regions formed adjacent to a respective edge of the strip-shaped ridge region within the strip-shaped ridge region,
• 10a ,b Representations analogous to 7a ,b and 8a ,b with four refractive index variation regions formed adjacent to a respective edge of the strip-shaped ridge region in the strip-shaped ridge region or in the trapezoidal ridge regions,
• 11a ,b Representations analogous to 9a ,b, in which two projecting trapezoidal web regions are formed on both the first and the second edge of the strip-shaped web region.

In the following description of the drawings, identical reference symbols are used for identical or functionally identical components.

1 shows an exemplary structure of a semiconductor laser chip 1, which forms a single-strip ridge waveguide laser or a laser diode. The semiconductor laser chip 1 has an active semiconductor layer 2 (active, generally undoped region) which is arranged between a first and second waveguide layer 3a,b, which are made of a p- or n-doped semiconductor material. In addition, the semiconductor laser chip 1 has a p-doped cladding layer 4, which has an upwardly projecting partial region, on the top of which a strip-shaped contact layer 5a (p-contact) is applied. The layers 2, 3a,b, 4, 5a are applied to an (n-doped) substrate 6, on the underside of which a further contact layer 5b is applied (n-contact). The contact layers 5a,b are connected by means of a 1 also shown voltage source 7 and make it possible to inject a current into the semiconductor laser chip 1, more precisely into the active layer 2, in order to pump the active layer 2.

As in 1 As can also be seen, the semiconductor laser chip 1 is an edge emitter, ie the semiconductor laser chip 1 emits laser radiation 8 along a lateral edge of the active layer 2 in a (main) propagation direction which corresponds to the longitudinal direction Y of a 1 also shown XYZ coordinate system, whose lateral direction is designated X and whose vertical direction is designated Z. The materials from which the semiconductor laser chip 1 is formed depend on the application or on the wavelength of the emitted laser radiation 8. Since the materials for a particular application Since the materials available for the application are generally known to the person skilled in the art, the choice of materials will not be discussed in more detail in the present application.

The laser resonator of the semiconductor laser chip 1 is limited by two parallel mirror (surfaces) 9a,b, which are formed at the edges of the gain region and the active semiconductor layer 2, respectively, see also 3a ,b, which show the semiconductor laser chip 1 and the active layer 2 in a plan view. The mirrors 9a,b are typically formed by cleaving the facets or the lateral edges of the layers 2, 3a,b, 4, 5a,b, with or without the deposition of a sequence of additional dielectric (reflective) layers.

In the event that additional mirror layers are applied to the lateral edges of the active layer 2, the first mirror 9a, which serves as an output mirror, has a typically low reflectivity, which is usually less than approximately 5%, and the second mirror 9b has a reflectivity of more than approximately 90%. As in 3a ,b can also be seen, the active layer 2 has a web 10 which adjoins the two parallel mirror surfaces 9a,b and which extends in the longitudinal direction Y between the two mirror surfaces 9a,b (see also the 3a ,b, the origin of which is in the center of the web 10). In the example shown, the web 10 has a constant width D _R in the lateral direction X. The web 10 is formed in the active layer 2 by etching away the active layer 2 and possibly other layers in a surrounding area 11, which is flat and borders on the lateral edges 12a, 12b of the web 10 (cf. 3a) or which is limited to two trench-shaped areas which adjoin the two lateral edges 12a, 12b of the web 10, as shown in 3b In both cases, the surrounding area 11 of the ridge 10 has a lower (real part of the) refractive index than the ridge 10 itself. Therefore, the ridge (area) 10 forms a waveguide, ie the optical modes are guided under or in the ridge 10. The control current is supplied through the top of the ridge 10.

The number of laser modes is mainly determined by the width D _R of the ridge 10. For a high optical output power, conventional semiconductor laser chips 1 use a width D _R in the lateral direction X, which is in the order of magnitude between approx. 10 µm and approx. 500 µm, in particular between approx. 100 µm and approx. 500 µm. As in 3a ,b, the web 10 has a constant width D _R over the entire extension in the longitudinal direction Y. However, such a large width D _R of the web 10 leads to a poor beam quality, which is typically more than 10 times greater than is the case with diffraction-limited laser radiation 8.

In order to improve the beam quality, it is known to use either a small ridge width d _R of a few micrometers, as shown (not to scale) in 4a ,b (d _R << D _R ), or a web 10 with a tapered (trapezoidal) section is used, which adjoins a narrow web section (width d _R ) and widens from there to a maximum width d _T (d _R << d _T ), as shown in 5 is shown.

As in 2 which shows the lateral intensity distribution I ₀ (in the X direction) of the fundamental laser mode and the lateral intensity distributions I ₁ , I ₂ of the first two higher laser modes in the active layer 2 of the semiconductor laser chip 1, the fundamental laser mode is essentially concentrated around the center of the ridge 10 and has its maximum in the center of the ridge 10. The two higher laser modes, on the other hand, have maxima of their intensity distributions I ₁ , I ₂ that are clearly distant from the center of the ridge 10 or from the coordinate origin in the X direction.

The advantage of the small width d of the web 10 of 4a ,b or the small width d _R of the web-shaped section of 5 is that the 2 shown higher laser modes are rejected due to the small width d _R of the ridge 10, since they overlap with the charge carriers injected into the narrow ridge 10 to a significantly lesser extent than is the case with the fundamental laser mode. In this way, the beam quality of the emitted laser radiation 8 is improved.

Although the two in 4a ,b and in 5 Although the approaches shown improve the lateral beam quality, other optical properties of the emitted laser radiation 8, e.g. the optical output power, the power conversion efficiency, the reliability and the system costs of the semiconductor laser chip 1, are impaired.

In order to improve the beam quality without significantly impairing the optical output power and other advantages of conventional semiconductor lasers with wide ridges 10, it has recently been proposed to form various corrugated structures on a ridge 10 or on the lateral edges 12a, 12b of the ridge 10. The structures can be, for example, rectangular, herringbone or triangular structures that are repetitively distributed along the longitudinal direction Y. as is the case, for example, in the US 8,396,091 described.

6a ,b show an example of such a bridge 10, which has a central, strip-shaped bridge region 10a with a constant width d (> d _R ), to whose first, left edge 12a shown in dashed lines six triangular bridge regions 10b are connected, which protrude laterally beyond the central, strip-shaped bridge region 10a. Accordingly, the second, right edge 12b of the strip-shaped bridge region 10a is connected to six triangular bridge regions 10b', which protrude laterally beyond the second edge 12b of the strip-shaped bridge region 10a. In contrast to the strip-shaped bridge region 10a, the laterally protruding bridge regions 10b, 10b' are not pumped and serve to increase the losses of the higher order modes in order to suppress them and in this way increase the beam quality of the laser radiation 8. The central, strip-shaped web region 10a and the respective laterally projecting web regions 10b, 10b' are monolithic, i.e. they together form the web 10.

7a ,b show an alternative embodiment of the web 10 according to the invention, which also has a central strip-shaped web region 10a, on which laterally projecting web regions 10b, 10b' are formed, which adjoin the first and second lateral edges 12a, 12b, respectively. The laterally projecting web regions 10b, 10b' are designed in the manner of (butterfly) wings, more precisely in the form of trapezoids. A respective projecting web region 10a, 10a' has a length in the Y direction, which varies depending on the position in the X direction. The length increases from a first length L ₁ directly at the first or second edge 12a, 12b of the strip-shaped web region 10a, which forms a first, short base side of the trapezoidal web region 10b, 10b', to a second length L ₂ , which forms a second, long base side of the respective trapezoidal web region 10b, 10b'. For the first length L ₁ and the second length L _{2 ,} in the example shown, L ₂ > 1.2 L ₁ , or more precisely L ₂ > 1.3 L ₁ .

The wing-shaped protruding web areas 10b, 10b' generate scattering and absorption losses in the higher order laser modes, which typically have a higher performance or a greater efficiency than the ones described above in connection with 6a ,b described corrugated structures.

As in 7a ,b can also be seen, the two trapezoidal projecting web areas 10b, 10b' are designed as isosceles trapezoids, ie they are arranged mirror-symmetrically to a central axis M running in lateral direction X, which in 7a is shown in dash-dotted lines. A respective trapezoidal web area 10b, 10b' has a straight first and second leg 13a, 13b to connect a first/second end of the first base side L ₁ of the trapezoid with a first/second end of the second base side L ₂ of the trapezoid. The first and second legs 13a, 13b are in the 7a ,b shown example at an angle α of approximately 45° to the first or second lateral edge 12a, 12b and thus also to the first base side L ₁ , which is formed on a respective section of the lateral edge 12a, 12b. It is advantageous if the angle α between the respective leg 13a, 13b and the lateral edge 12a, 12b is at least 30° and not more than 70°.

It is understood that the trapezoidal protruding web areas 10b, 10b' do not necessarily have to be designed as isosceles trapezoids. It is also not absolutely necessary for the two legs 13a, 13b, which connect the base sides L ₁ , L ₂ to run in a straight line; rather, they can have a curve if necessary. A protruding web area 10b, 10b' designed in this way, ie with curved legs 13a, 13b, is also referred to as trapezoidal in the sense of this application.

As in 7a ,b can also be seen, a respective projecting web region 10b, 10b' has a width d _s in the lateral direction X, for which the following applies: d _S > 0.5 d, where d denotes the constant width of the strip-shaped web region 10a in the example shown. The width d of the strip-shaped web region 10a is between 10 µm and 250 µm, preferably between 100 µm and 250 µm, ie this is smaller than the width D _R of a conventional web 10, as in 3a ,b is shown.

The propagation of the higher order modes in the lateral direction X starting from the center of the ridge 10 can be increased by generating a modulation or a variation of the refractive index n adjacent to the lateral edges 12a, 12b of the ridge 10 or, in the example shown, the strip-shaped ridge region 10a. In this way, the overlap of the higher modes with the injected charge carriers is reduced, which improves the beam quality of the emitted laser radiation 8. In order to achieve this, in the following in connection with 8a ,b to 11a ,b, a plurality of refractive index variation regions 14, 14', 15, 15' are additionally produced in the active layer 2, namely adjacent to one or both edges 12a,b of the strip-shaped web region 10a.

8a ,b show two refractive index variation regions 14, 14', which are each formed within the web 10, more precisely in the laterally projecting first web region 10b arranged adjacent to the first lateral edge 12a or in the laterally projecting second web region 10b' arranged adjacent to the second lateral edge 12b. In the two in 8a ,b, the respective refractive index variation region 14, 14' has a maximum distance A _max to the respective adjacent lateral edge 12a, 12b, for which A _max / d < 0.5, in particular A _max / d < 0.4, applies.

A respective in 8a ,b has three lateral structures in the form of trenches 16 etched into the active layer 2, which extend parallel to the lateral edges 12a,b of the strip-shaped web region 10a. The trenches 16 have a substantially rectangular cross-section in the lateral direction X, which leads to a modulation or variation of the refractive index n within the refractive index variation region 14, 14', as shown in 8a shown below. Since the trenches 16 extend practically over the entire height of the active layer 2, the active layer 2 has a refractive index n of almost 1.0 in the area of the trenches 16. In two intermediate areas 17, which each separate two adjacent trenches 16 from each other, the refractive index n, however, matches the refractive index of the semiconductor material of the ridge 10. The variation of the refractive index n generated in this way causes the 2 shown extend further in the lateral direction X from the center of the web 10 into the unpumped, laterally projecting web regions 10b, 10b' than would be the case without the refractive index variation region 14, 14'. Therefore, the contribution of the higher laser modes to the emitted laser radiation 8 decreases and thus its beam quality increases.

As in 8a As can also be seen, the respective refractive index variation range 14, 14' in the longitudinal direction Y does not extend beyond the first (minimum) length L ₁ of the laterally projecting web region 10b, 10b', but rather the length of the refractive index variation range 14, 14' in the longitudinal direction Y corresponds to the length L ₁ of the respective projecting web region 10b, 10b' at the lateral edge 12a, 12b.

In the 8a ,b, the three trenches 16 each have an identical, predetermined width b. The intermediate areas 17 also have an identical, predetermined width B, which in the example shown is larger than the width b of the trenches 16, but does not necessarily have to be larger than the width b of the trenches 16. In the example shown in 8a In the example shown, the trenches 16 together with the intermediate regions 17 produce a periodic lateral variation of the refractive index n, which in 8a can be seen below. However, it is understood that at least two of the trenches 16 can each have different widths b and/or that at least two of the intermediate regions 17 can each have different widths B, whereby an aperiodic lateral structure or an aperiodic variation of the refractive index n can be generated in the respective refractive index variation region 14, 14'. It is also not absolutely necessary for the web 10 to have two refractive index variation regions 14, 14'; rather, only a single refractive index variation region 14 can be formed on the first lateral edge 12a or only a single refractive index variation region 14' on the second lateral edge 12b.

While in 8a ,b the refractive index variation regions 14, 14' are formed only in the two lateral web regions 10b, 10b', are in the 9a ,b, two refractive index variation regions 15, 15' are formed between the two lateral edges 12a, 12b within the strip-shaped web region 10a. In this case too, the refractive index variation regions 15, 15' each have a maximum distance A _max to the respective adjacent lateral edge 12a, 12b, for which A _max / d < 0.5, in particular A _max / d < 0.4 applies. As in 9a As can be seen, the distance A _max is measured from the side of the trench 16 furthest from the first lateral edge 12a facing away from the first lateral edge 12a. In the 9a ,b, the two refractive index variation regions 15, 15' each have two trenches 16 which are separated from one another by an intermediate region 17. The widths of the trenches 16 and the widths of the intermediate regions 17 can be determined as in connection with 8a ,b can be chosen either periodically or aperiodically.

Even with the 9a ,b, it is not absolutely necessary for the web 10 to have two refractive index variation regions 15, 15', but rather only a single refractive index variation region 15 can be formed in the strip-shaped web region 10a adjacent to the first lateral edge 12a, or only a single refractive index variation region 15' can be formed adjacent to the second lateral edge 12b in the strip-shaped web region 10a.

It is understood that the number of two or three trenches 16 in 8a ,b or 9a ,b and in the further representations is merely exemplary and that the refractive index variation areas 14, 14', 15, 15' also have more or fewer trenches 16, eg one trench 16 or three, four, .... or a significantly larger number of trenches 16. Instead of trenches 16, other lateral structures can also be used to generate a refractive index variation. For example, doping limited to a respective lateral region, laser material treatment of the semiconductor material in a respective lateral region of the active layer 2, etc. can serve for this purpose.

In the 9a ,b, the respective refractive index variation regions 15, 15' do not extend in the longitudinal direction Y beyond the length L ₁ of the laterally projecting web region 10b, 10b' on the first or second lateral edge 12a, 12b of the strip-shaped web region 10a. More precisely, the length of the two refractive index variation regions 15, 15' in the longitudinal direction Y corresponds exactly to the (first) length L ₁ of the laterally projecting web regions 10b, 10b'. Alternatively, it is possible for the respective refractive index variation regions 15, 15' to extend beyond the first length L ₁ of the respective laterally projecting web region 10b, 10b'. For example, the respective refractive index variation regions 15, 15' can extend in the longitudinal direction Y over the entire extent of the strip-shaped web region 10a between the two mirror surfaces 9a,b, as shown in 9a ,b is indicated by dashed lines.

10a ,b show the active layer 2 and the web 10 in an example which illustrates the 8a ,b and in 9a ,b are combined so that the web 10 has a total of four refractive index variation regions 14, 15, 14', 15', which are each arranged adjacent to the first edge 12a or adjacent to the second edge 12b of the strip-shaped web region 10a. A first and second refractive index variation region 14, 15 are formed adjacent to the first edge 12a in the protruding web region 10b or in the strip-shaped web region 10a. Accordingly, a third and fourth refractive index variation region 14', 15' are formed adjacent to the second edge 12b in the associated protruding web region 10b' or in the strip-shaped web region 10a.

In order to increase the efficiency of suppression of the higher modes, two or more laterally projecting web regions can also be formed on one and the same lateral edge 12a, 12b of the strip-shaped web region 10a. 11a ,b shows this by way of example for the case where two laterally projecting web regions 10b, 10c are formed on the first lateral edge 12a, which are spaced apart from one another in the longitudinal direction Y. Similarly, two laterally projecting web regions 10b', 10c' are formed on the second lateral edge 12b, which are also spaced apart from one another in the longitudinal direction Y. Two mutually opposite web regions 10b, 10b', 10c, 10c' are formed in the 11a ,b shown example in the lateral direction Y at the same height, but this is not absolutely necessary, ie the protruding web areas 10b, 10c on the first lateral edge 12a can also have a lateral offset to the protruding web areas 10b', 10c' on the second lateral edge 12b.

In the 11a ,b, a refractive index variation region 15 is formed adjacent to the first edge 12a within the first strip-shaped web region 10a, which extends in the longitudinal direction Y only over the respective length L ₁ of the two web regions 10b, 10c projecting laterally beyond the first edge 12a and over a section 18 between the laterally projecting web regions 10b, 10c along the first lateral edge 12a. Accordingly, a refractive index variation region 15' is formed on the second edge 12b of the strip-shaped web region 10a, which extends in the longitudinal direction Y only over the respective (first) length L ₁ of the two refractive index variation regions 10b', 10c' adjacent to the second lateral edge 12b and over a section 18 between the two laterally projecting web regions 10b', 10c'. Alternatively, in the case of the embodiment shown in 11a ,b, a respective refractive index variation region 15, 15' in the longitudinal direction Y extends over the entire length of the strip-shaped web region 10a, as shown in 11a ,b is indicated by dashed lines.

It is understood that the arrangement and the number of the refractive index variation regions 14, 14', 15, 15' are not limited to the examples described above. For example, the active layer 2 can have three refractive index variation regions, two of which are arranged adjacent to one of the two edges 12a, 12b and the third of which is arranged adjacent to the other of the two edges 12a, 12b. Refractive index variation regions 14, 14', 15, 15' formed in the manner described above can also be formed on webs 10 which have protruding web regions which are formed differently than the web regions 10b, 10b', 10c, 10c' described above which widen starting from a first length L ₁ , for example in the case of protruding web regions as shown in the US 8,396,091 which is incorporated by reference in its entirety into this application.

In all the examples described above, a strip-shaped ridge region 10a with a width d can be used which is greater than the width d _R in a semiconductor laser chip 1 which has a ridge 10 with a small ridge width, as shown in 3 is shown. Due to the (wing-shaped) protruding strip-shaped ridge regions 10b, 10b', 10c, 10c' and possibly due to the additional refractive index variation regions 14, 14', 15, 15', the higher laser modes can be suppressed despite the larger width d of the strip-shaped ridge region 10a and thus a good beam quality can be ensured. A semiconductor laser chip 1 designed in the manner described above additionally has the advantages of semiconductor laser chips 1 with ridges 10 of large width D _R , for example a low electrical and thermal resistance and thus a high optical output power, but also a high power conversion efficiency, especially at high power levels, and a high level of reliability.

Claims (14)

Semiconductor laser chip (1) for emitting laser radiation (8), comprising: an active layer (2) with a web (10) which has a strip-shaped web region (10a), wherein at least one web region (10b, 10b') projecting laterally beyond the strip-shaped web region (10a) adjoins a first and/or a second lateral edge (12a, 12b) of the strip-shaped web region (10a), wherein a length of the laterally projecting web region (10b, 10b', 10c, 10c') in the longitudinal direction (Y) increases from a first length L ₁ at the first or at the second lateral edge (12a, 12b) of the strip-shaped web region (10b, 10b', 10c, 10c') to a second length L ₂ , wherein: L ₂ > 1.2 L ₁ , wherein at two two mirror surfaces (9a, 9b) are formed on opposite sides of the active layer (2), to which the strip-shaped web region (10a) of the web (10) adjoins and to which the projecting web region (10b, 10b') of the web (10) does not adjoin. semiconductor laser chip according to claim 1 , in which the laterally projecting web region (10b, 10b', 10c, 10c`) is trapezoidal and preferably runs mirror-symmetrically to the lateral direction (X). semiconductor laser chip according to claim 2 , in which two legs (13a, 13b) of the trapezoidal projecting web region (10b, 10b', 10c, 10c') are aligned at an angle (α) of at least 30° and not more than 70° to the first or second lateral edge (12a, 12b) of the strip-shaped web region (10a). Semiconductor laser chip according to one of the preceding claims, wherein the strip-shaped web region (10a) has a width d, in which the laterally projecting web region (10b, 10b', 10c, 10c') has a width d <sub>S</sub> in the lateral direction (X), for which the following applies: d <sub>S</sub> > 0.5 d. Semiconductor laser chip according to one of the preceding claims, wherein the width d of the strip-shaped web region (10a) is between 10 µm and 250 µm, preferably between 100 µm and 250 µm. Semiconductor laser chip according to one of the preceding claims, in which the active layer (2) has at least one refractive index variation region (14, 14', 15, 15') which is arranged adjacent to the first lateral edge (12a) or to the second lateral edge (12b) of the strip-shaped web region (10a), wherein the refractive index variation region (14, 14', 15, 15') has a maximum distance A <sub>max</sub> from the first lateral edge (12a) or to the second lateral edge (12b), which is given by A <sub>max</sub> / d < 0.5, preferably A <sub>max</sub> / d < 0.4. semiconductor laser chip according to claim 6 , in which the at least one refractive index variation region (14, 14') is formed in the at least one laterally projecting web region (10b, 10b'), wherein the at least one refractive index variation region (14, 14') preferably does not extend in the longitudinal direction (Y) beyond the first length L <sub>1</sub> of the laterally projecting web region (10b, 10b'). semiconductor laser chip according to claim 6 , wherein the at least one refractive index variation region (15, 15') is formed between the first edge (12a) and the second edge (12b) of the strip-shaped web region (10). semiconductor laser chip according to claim 6 , in which the active layer (2) has at least two refractive index variation regions (14, 14', 15, 15'), in which at least one of the refractive index variation regions (15, 15') is formed between the first edge (12a) and the second edge (12b) of the strip-shaped web region (10a), and in which at least one of the refractive index variation regions (14, 14') is formed in the at least one laterally projecting web region (10b, 10b', 10c, 10c'). semiconductor laser chip according to claim 8 or 9 , in which the at least one refractive index variation region (15, 15') formed between the first edge (12a) and the second edge (12b) of the strip-shaped web region (10a) extends in the longitudinal direction (Y) over the entire first covering of the strip-shaped web area (10a). Semiconductor laser chip according to one of the Claims 8 or 9 , in which the at least one refractive index variation region (15, 15') which is formed between the first edge (12a) and the second edge (12b) of the strip-shaped web region (10) does not extend in the longitudinal direction (Y) beyond the length L <sub>1</sub> of the laterally projecting web region (10b, 10b', 10c, 10c`) at the first or at the second lateral edge (12a, 12b). Semiconductor laser chip according to one of the Claims 8 or 9 , in which at least two laterally projecting web regions (10b, 10c) adjoin the first edge (12a) of the strip-shaped web region (10a) and/or in which at least two laterally projecting web regions (10b', 10c`) adjoin the second edge (12b) of the strip-shaped web region (10a), wherein the at least one refractive index variation region (15, 15') formed between the first edge (12a) and the second edge (12b) of the strip-shaped web region (10) extends in the longitudinal direction (Y) only over the respective length L ₁ of the at least two laterally projecting web regions (10b, 10c; 10b', 10c') and over a section (18) between the laterally projecting web regions (10b, 10c; 10b', 10c') on the first lateral edge (12a) or on the second lateral edge (12b). Semiconductor laser chip according to one of the Claims 6 until 12 , in which the refractive index variation region (14, 14', 15, 15') has at least one lateral structure, which is preferably designed as a trench (16), wherein the refractive index variation region (14, 14', 15, 15') in particular has at least two lateral structures with a predetermined width (b), which are separated from one another by a respective intermediate region (17) which has a predetermined width (B). Semiconductor laser chip according to one of the preceding claims, further comprising: at least one p-doped waveguide layer (3a) and at least one n-doped waveguide layer (3b), between which the active layer (2) is arranged.

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