DE102021211000A1 - Semiconductor laser chip with at least one protruding web area - Google Patents

Abstract

The invention relates to a semiconductor laser chip for emitting laser radiation, comprising: an active layer (2) with a ridge (10) which has a strip-shaped ridge region (10a) with a width d that is preferably constant in the lateral direction (X), with adhering to a at least one web area (10b, 10b`) protruding laterally beyond the strip-shaped web area (10a) adjoins the first and/or a second lateral edge (12a, 12b) of the strip-shaped web area (10a). A length of the laterally protruding web area (10b, 10b`) in the longitudinal direction (Y) increases starting from a first length L ₁ at the first or at the second lateral edge (12a, 12b) of the strip-shaped web area (10b, 10b`). to a second length L <sub>2</sub> , where: L <sub>2</sub> > 1.2 L <sub>1</sub> , preferably L <sub>2</sub> > 1.3 L <sub>1</sub> . The laterally protruding web area(s) (10b, 10b`) are preferably trapezoidal.

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 (waveguiding) ridge, which has a strip-shaped ridge area with a preferably constant width d, wherein at least one ridge area that protrudes laterally (i.e. in the lateral direction) beyond the strip-shaped ridge area adjoins a first and/or a second lateral edge of the strip-shaped ridge area.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 stripe ridge portion may vary depending on the position in the longitudinal direction, but preferably the width d of the stripe ridge portion is constant in the longitudinal direction.

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

The laser resonator of such a semiconductor laser chip, which is also referred to as a Fabry-Perot resonator, is formed by a pair of parallel mirrors or mirror surfaces, which are formed at the edges of the gain medium or the active semiconductor layer. The mirror (surfaces) can be produced by merely dividing or cutting off the crystal planes perpendicular to the plane with the laser resonator. The resulting interfaces between the crystal and the surrounding air can themselves provide the necessary reflectivity to sustain the laser oscillations. In order to maximize the output power of the laser, the mirror reflectivity is often adjusted to less than 10% at the output facet and more than 90% at the rear facet by depositing a series of dielectric layers on the respective facet or mirror surface becomes.

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 layer. The generated light is partially emitted through the (mirror) facet into the surrounding air and partially reflected back into the laser resonator, where it is amplified by stimulated emission. In order to ensure the amplification of the light, it is necessary for an external electrical input power to inject a sufficient number of charge carriers into the amplification region.

In the 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 layers of semiconductor and the current is supplied through the top of the ridge. Therefore, only those optical modes that propagate under the stream aperture or ridge (as well as the area covered by the so-called stream spread) 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-controlled semiconductor lasers is also referred to as the ridge for the sake of simplicity. The current aperture or the ridge in the laser-active layer typically differs from a surrounding area outside of the ridge in that the surrounding area has a doping or 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 the case of semiconductor lasers, a proportion of the injected current is converted into optical output power P _out according to the following formula: $${\text{P}}_{\text{out}}={\mathrm{n}}_{\text{sloped}}\left(\text{I}-{\text{I}}_{\text{thr}}\right),$$

where η _slope is the (slope) efficiency, I is the injected current and I _thr is the current threshold. The fraction of the electrical power supplied that results in usable light is also referred to as power conversion efficiency (PCE). The remaining input power is dissipated in the device (the semiconductor laser chip) and leads to disadvantageous heating of the device and possible 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 $$\text{B}={\text{P}}_{\text{out}}/\left({\text{<figure-callout id="2" label="M" filenames="DE102021211000A1\_0003.png,DE102021211000A1\_0004.png" state="{{state}}">M</figure-callout>}}^{\text{2}}{}_{\text{<figure-callout id="2" label="lat M" filenames="DE102021211000A1\_0003.png,DE102021211000A1\_0004.png" state="{{state}}">lat</figure-callout>}}{\text{M}}^{}{}^{\text{2}}{}_{\text{vert}}{\mathrm{\lambda }}^2\right),$$

where M ² _{lat denotes} the lateral beam quality, M ² _vert denotes the vertical beam quality and λ denotes 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 increases the optical output power linearly before thermal effects dominate. A 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 that reduce device heating and enable high output power, high PCE, and improved reliability of the semiconductor laser chip.

For applications with high brightness, good beam quality is an essential factor in addition to high output power. The beam quality M ² in Eq. (2) mainly depends on the number of laser modes. Emission of the fundamental mode alone results in a nearly diffraction-limited laser beam with M ² ~ 1. The beam quality degrades as the number of laser modes increases. As a rule, conventional high-power semiconductor lasers use epitaxial layer structures that only excite the fundamental mode in the vertical direction, so that M ² _vert\ ~ 1 is ensured. The wide web, which is required for high output powers, supports the propagation of many laser modes, which leads to a deterioration in the beam quality M ² _lat in the lateral direction. This affects the brightness, which makes it difficult to use semiconductor lasers in many industrial fields of application.

Considering the mode distributions in the laser waveguide, different techniques can be considered to achieve good lateral beam quality. Much of the fundamental mode, particularly its maximum intensity region, is concentrated in the center of the ridge, while substantial parts of the intensity of the higher-order modes are localized away from the central region of the ridge.

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

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

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

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, for example, triangular, rectangular or herringbone-shaped structures on both sides of the edge of the ridge along its longitudinal direction, see for example U.S. 8,396,091 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 outwards in the lateral direction, starting from a strip-shaped web area with a constant width, ie they project outwards beyond the web area of constant width. The corrugated structures are thus comparatively far removed from the center or from the center of the web in the lateral direction. Therefore, only the higher order modes experience scattering losses in the propagation along the longitudinal direction at the corrugated structures, 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 favor of the fundamental mode.

In the DE 10 2008 014 093 A1 describes an edge-emitting semiconductor laser chip that 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 widening in the semiconductor layers between the active zone and the contact strip or strips. The current barriers can form trenches which, starting from the contact strip or from a contact layer, are etched to at least below the active layer.

object 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 level of brightness (brilliance).

subject of the invention

According to a first aspect, this object is achieved by a semiconductor laser chip of the type mentioned at the outset, in which a length of the laterally projecting ridge region in the longitudinal direction, starting from a first length L ₁ at the first or at the second lateral edge of the strip-shaped ridge region, is reduced to a second length L ₂ increases, where: L ₂ > 1.2 L ₁ , preferably L ₂ > 1.3 L ₁ .

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

In principle, it is also possible for the laterally protruding web area to have a section that is further away from the center of the web in the lateral direction, in addition to a section that widens from the first length L ₁ to the second length L ₂ , the length of which is in the longitudinal direction starting from the second length L ₂ decreases. The protruding web area is preferably widened continuously from the first length L ₁ to the second length L ₂ . The side edges or legs of the overlapping web area can run in a straight line starting from the section of the first or second side edge, but it is also possible for the side edges to have a curvature. The first length L ₁ preferably represents a minimum length and the second length L ₂ preferably represents a maximum length of the protruding web area.

The overhanging ridge region can be formed by etching away the semiconductor layer(s) when forming the ridge. The laterally protruding web area and the strip-shaped web area form a continuous, monolithic structure. In contrast to the strip-shaped ridge area, 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 ridge area. In contrast to the strip-shaped web area, the at least one laterally projecting web area is generally not electrically pumped.

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

In one embodiment, the laterally protruding web area is trapezoidal and preferably runs mirror-symmetrically to the lateral direction. In this case, a section of the lateral edge of the strip-shaped web area forms the shorter base of the trapezium (with the first Length L ₁ ) and the longer base side aligned in parallel has the second length L ₂ . It goes without saying that other geometries of the protruding web area are also possible. For example, the web area can have a section which widens to the second length L ₂ and which is adjoined by a narrowing section. The longer base side of the trapezoidal web area can optionally also have a corrugated geometry or a wave shape. A straight, long base side (of length L ₂ ) of the trapezoidal protruding web area, which runs parallel to a lateral edge of the web 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 protruding web area are aligned at an angle of at least 30° and no more than 70° to the first or to the second lateral edge of the strip-shaped web area. Orienting the legs of the overhanging land portion at angles within this interval has been found to be beneficial in increasing the higher mode losses.

In a further embodiment, the laterally protruding web area has a width ds in the lateral direction, for which the following applies: ds>0.5 d. The use of a laterally protruding web area, which has a comparatively large width, has proven to be favorable for suppressing higher modes.

In one embodiment, the width d of the strip-shaped web area is between 10 μm and 250 μm, preferably between 100 μm and 250 μm. The width d of the strip-shaped ridge region is typically less than that of a conventional wide-ridge ridge waveguide, but greater than that of a narrow-ridge ridge waveguide. The total width of the ridge, i.e. the sum of the width d of the strip-shaped ridge area and the width ds of the or the two laterally projecting ridge areas (d + ds or d + 2 ds) is of 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 varying region, which is arranged adjacent to the first lateral edge or to the second lateral edge of the strip-shaped web area, the refractive index -Variation range has a maximum distance A _max from the first lateral edge or from 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 area into the laterally protruding ridge area(s). The expansion of the higher order modes reduces their confinement factor, ie the fraction of the optical modes that resides under the striped central ridge region that is electrically pumped. As a result, the modal gain of the higher order modes is reduced. The provision of at least one refractive index variation range is not only favorable in the event that the protruding web areas are wing-shaped or widen starting from the first length L ₁ , but also in the case of protruding web areas that are designed in a different way, for example in the further triangular, herringbone or rectangular overhanging land 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 is preferred that the refractive index variation region is formed adjacent to the edge of the strip-shaped ridge area, i.e. if it extends no further from the edge of the strip-shaped ridge area than is described by the above formula.

The modulation or the variation of the refractive index in the lateral direction, ie 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 area. A respective refractive index variation range can be formed within the strip-shaped ridge region, ie 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 areas are usually not electrically pumped, the expansion of the higher-order laser modes into the protruding ridge area(s) also leads to scattering losses Increase in absorption that suppress their contribution to laser emission.

The modulation of the refractive index can be generated by lateral structures which are designed 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 continuously or discontinuously in the lateral direction in the refractive index variation range, e.g. in the manner of a rectangular profile.

It is generally favorable when there is no additional refractive index variation in the longitudinal direction in the refractive index variation range, ie when the lateral variation of the refractive index in the longitudinal direction is constant or changes according to the width of the strip-shaped ridge area. Even in the case of a strip-shaped web area, the width d of which 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 web area has a constant width in the lateral direction. In this case, the lateral structures in the refractive index varying region usually extend in the longitudinal direction parallel to the strip-shaped ridge region, ie at a constant distance from the strip-shaped ridge region or from the respective lateral edge to which the respective refractive index varying region is arranged adjacent.

In one embodiment, the at least one refractive index varying region is formed in the at least one laterally projecting ridge region, wherein the at least one refractive index varying 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 region(s) is/are formed in the unpumped respective laterally overhanging ridge region(s). In the event that at least one laterally protruding ridge area is formed on the first edge and at least one laterally protruding ridge area on the second edge of the strip-shaped ridge area, a single refractive index variation area can be in the laterally protruding ridge area adjacent to the first edge of the ridge or in the laterally protruding ridge area can be formed adjacent to the second edge of the ridge, ie the refractive index variation area(s) can be limited to the vicinity of the first edge or the second edge. Alternatively, a first refractive index variation region may be formed in (at least one) laterally overhanging ridge region adjacent the first edge of the ridge and a second refractive index variation region may be formed in (at least one) laterally overhanging ridge region adjacent the second edge of the ridge.

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

In one embodiment, the at least one refractive index variation range is formed between the first edge and the second edge of the strip-shaped ridge area. In this embodiment, the refractive index varying region or regions are formed only within the strip-shaped ridge area, i.e. there is no refractive index varying region outside the strip-shaped ridge region. In this embodiment, refractive index variation regions may be formed only adjacent to the first edge of the stripe-shaped ridge area or only adjacent to the second edge of the stripe-shaped ridge area. Alternatively, (at least) a first range of refractive index variation may be formed adjacent to the first edge of the strip-shaped ridge area and (at least) a second range of refractive index variation may be formed adjacent to the second edge of the strip-shaped ridge area.

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

A protruding web area is preferably formed both on the first edge of the strip-shaped web area and on the second edge of the strip-shaped web area. In this case, it has proven to be advantageous if (at least) one refractive index variation area is formed inside the strip-shaped ridge area and (at least) one refractive index variation area is formed outside the strip-shaped ridge area both on the first edge and on the second edge.

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

It is not absolutely necessary, but can be advantageous if the refractive index variation range 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 favorable if the refractive index variation range is formed within the strip-shaped ridge area and extends into at least a section of the lateral edge that is formed outside of the first length L ₁ on which the respective laterally projecting ridge area is formed. In the section of the strip-shaped ridge area that is not bordered by a laterally protruding ridge area, a variation in the refractive index is generated directly at the edge of the strip-shaped ridge area anyway, since the refractive index inside the ridge is greater than the refractive index in a surrounding area outside the ridge, around the desired To fulfill waveguide function of the web. It is therefore not necessary - but also not impossible - that the refractive index variation begins directly 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 land area begins.

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 over the first length L ₁ of the laterally overhanging ridge region at the first or at the second lateral edge out. In particular, the length of the refractive index variation range can correspond to the (first) length L ₁ of the laterally projecting web area. This embodiment represents an alternative to the embodiment described above, in which the at least one refractive index variation range extends in the longitudinal direction over the entire extent of the resonator.

In an alternative embodiment, at least two laterally projecting land areas adjoin the first edge of the strip-shaped land area and/or at least two laterally projecting land areas adjoin the second edge of the strip-shaped land area, with preferably the at least one refractive index variation area between the first edge and the second edge of the strip-shaped web area, extends in the longitudinal direction only over the respective first length L ₁ of the at least two laterally overhanging web areas and over a section between the laterally overhanging web areas at the first lateral edge or at the second lateral edge extends. In this case, the at least one refractive index variation range extends in each case along or between the laterally protruding web areas, but not beyond, ie not up to the respective end of the resonator on the first or on the 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 web region.

It goes without saying that combinations of refractive index variation ranges 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 area within the ridge or in a laterally projecting ridge area, and the third of which is formed on the other edge of the strip-shaped ridge area either within the strip-shaped Web area or is formed in the laterally projecting web area.

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

In one embodiment, the refractive index variation area has at least one lateral structure, which is preferably designed as a trench, wherein the refractive index variation area has in particular 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 having. The lateral structure has a refractive index which 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 in the form of a trench which 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. Particularly in the event that the trench is formed in the non-pumped, laterally protruding web area, the trench can optionally be filled with an absorbent material. It goes without saying 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 range preferably has at least two lateral structures with a specified width, the at least two lateral structures being separated from one another by a respective intermediate region which has a specified width. The intermediate area (sub-web) can be designed like the rest of the web. Only in the area of the lateral structures, for example at the trenches, does the refractive index vary in this case, which is otherwise usually constant in the lateral direction within the ridge, i.e. both within the strip-shaped ridge area and within the laterally projecting ridge area.

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

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

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

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 is typically undoped, at least in the region of the ridge, 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 goes without saying that the semiconductor laser chip can also have further layers. In particular, typically in a gain-guided semiconductor laser chip, the current is supplied through an aperture defined by a dielectric insulator or by ion implantation. In this case, a contact layer in the form of a contact strip for electrical contacting is typically formed on the upper side of the semiconductor laser chip, the width of the contact strip generally corresponding to the width of the strip-shaped web region. In index-guided lasers, the ridge is formed by etching away layers of semiconductor and the current is applied through the top of the ridge. In this case, the contact layer can be applied to the top side of the semiconductor laser chip over the entire area. Typically, a further contact layer is formed on the underside of the substrate in order to use a current or a voltage source to supply a current to the active To inject layer, which is used to pump the semiconductor material present there.

Further advantages of the invention result from the description and the drawing. Likewise, the features mentioned above and those listed below can each be used individually or together in any combination. The embodiments shown and described are not to be understood as an exhaustive list, but rather have an exemplary character 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,
• 11 a,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.

Show it:

• 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 a 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 which has a web section with the small web width of 4a,b and has a tapering section,
• 6a,b Representations of a web with a plurality of triangular web areas that protrude over 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 varying areas formed adjacent to a respective edge of the stripe-shaped ridge area in the trapezoidal ridge areas,
• 9a,b Representations analogous to 8a,b having two refractive index varying regions formed adjacent to a respective edge of the stripe-shaped ridge region within the stripe-shaped ridge region,
• 10a,b Representations analogous to 7a,b and 8a,b having four refractive index variation areas formed adjacent to a respective edge of the stripe-shaped ridge area in the stripe-shaped ridge area or in the trapezoidal ridge areas,
• 11a,b Representations analogous to 9a,b , in which two protruding trapezoidal web areas are formed both on the first and on the second edge of the strip-shaped web area.

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 area) which is arranged between a first and second waveguide layer 3a,b, which are formed from a p-doped 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 another contact layer 5b is applied (n-contact). The contact layers 5a,b are connected by means of an in 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 It can also be seen that 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 corresponds to the XYZ coordinate system, whose lateral (side) direction is denoted by X and whose vertical direction is denoted by 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 available for a particular application are known in principle to a person skilled in the art, the material selection is not discussed in detail in the present application.

The laser resonator of the semiconductor laser chip 1 is delimited by two parallel mirror (areas) 9a,b, which are formed at the edges of the amplification region or the active semiconductor layer 2, see also FIG 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 (mirror) 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 the output mirror, typically has a low reflectivity, which is generally less than about 5%, and the second mirror 9b has a reflectivity greater than about 90%. As in 3a,b can also be seen, the active layer 2 has a ridge 10 which adjoins the two mirror surfaces 9a,b aligned in parallel and which extends in the longitudinal direction Y between the two mirror surfaces 9a,b (cf. also that in 3a,b coordinate system shown, the origin of which is in the center of the web 10). The web 10 has a constant width D _R in the lateral direction X in the example shown. The ridge 10 is formed in the active layer 2 by etching away the active layer 2 and possibly further layers in a surrounding region 11, which is flat and adjoins the lateral edges 12a, 12b of the ridge 10 (cf. 3a) or which is limited to two trench-shaped areas which border on the two lateral edges 12a, 12b of the web 10, as is shown in 3b is shown. In both cases, the surrounding area 11 of the ridge 10 has a lower (real part of) refractive index than the ridge 10 itself. 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 of the order of magnitude between approximately 10 μm and approximately 500 μm, in particular between approximately 100 μm and approximately 500 μm. As in 3a,b as can be seen, 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 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 _dR of a few micrometers, as shown (not to scale) in 4a,b is shown (d _R << D _R ), or a web 10 with a tapering (trapezoidal) section is used, which connects to a narrow web section (width d _R ) and from there to a maximum width d _T (d _R << d _T ) broadened, as in 5 is shown.

As in 2 can be seen, 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, is the fundamental one 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 in their intensity distributions I ₁ , I ₂ , which are clearly removed in the X-direction from the center of web 10 or from the origin of coordinates.

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 in 2 shown higher laser modes are discarded due to the small width d _R of the ridge 10, since they overlap to a much lesser extent with the charge carriers injected into the narrow ridge 10 than is the case with the fundamental laser mode. The beam quality of the emitted laser radiation 8 is improved in this way.

Although the two in 4a,b and in 5 If the approaches shown improve the lateral beam quality, other optical properties of the emitted laser radiation 8, for example 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 degrading the optical output power and other advantages of conventional wide ridge semiconductor lasers 10, it has recently been proposed to use various corrugated structures on a ridge 10 or on the lateral edges 12a, 12b of the ridge 10 to train. The structures can be, for example, rectangular, herringbone or triangular structures which are distributed repetitively along the longitudinal direction Y, as is the case for example in the initially cited U.S. 8,396,091 is described.

6a,b show an example of such a web 10, which has a central, strip-shaped web area 10a with a constant width d (> d _R ), at the first, left edge 12a shown in dashed lines, six triangular web areas 10b adjoin, which extend laterally over the central, strip-shaped web area 10a survive. Correspondingly, the second, right-hand edge 12b of the strip-shaped web area 10a is followed by six triangular web areas 10b`, which protrude laterally beyond the second edge 12b of the strip-shaped web area 10a. The one on the side In contrast to the strip-shaped ridge region 10a, the existing ridge 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 to increase the beam quality of the laser radiation 8. The central, strip-shaped web area 10a and the respective laterally projecting web areas 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 area 10a on which laterally protruding web areas 10b, 10b` are formed, which adjoin the first and the second lateral edge 12a, 12b. The laterally protruding web areas 10b, 10b' are designed in the manner of (butterfly) wings, more precisely in the form of trapezoids. Each projecting land portion 10a, 10a' has a length in the Y-direction which varies depending on the position in the X-direction. Starting from a first length _L1, the length increases directly at the first or second edge 12a, 12b of the strip-shaped web area 10a, which forms a first, short base side of the trapezoidal web area 10b, 10b', to a second length L ₂ , which forms a second, long base side of the respective trapezoidal web area 10b, 10b'. In the example shown, L ₂ >1.2 L ₁ , more precisely L ₂ >1.3 L ₁ , applies to the first length _L 1 and the second length L ₂ .

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

As in 7a,b can also be seen, the two trapezoidal protruding web areas 10b, 10b' are designed as isosceles trapezoids, ie they are arranged mirror-symmetrically to a central axis M running in the lateral direction X, which in 7a is shown in 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 L ₁ of the trapezoid to a first/second end of the second base L ₂ of the trapezium. The first and the second leg 13a, 13b are in the 7a,b example shown at an angle α of about 45 ° to the first or second lateral edge 12a, 12b and thus also aligned to the first base side L ₁ , which is formed on a respective portion of the lateral edge 12a, 12b. It is favorable 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 goes without saying that the trapezoidal protruding web areas 10b, 10b' do not necessarily have to be in the form of isosceles trapezoids. It is also not absolutely necessary for the two legs 13a, 13b, which connect the base sides L ₁ , L ₂ to one another, to run in a straight line; on the contrary, they can optionally have a curvature. 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 protruding web area 10b, 10b' has a width d _s in the lateral direction X, for which applies: ds > 0.5 d, where d denotes the constant width of the strip-shaped web area 10a in the example shown. The width d of the strip-shaped ridge area 10a is between 10 μm and 250 μm, preferably between 100 μm and 250 μm, ie it is smaller than the width D _R of a conventional ridge 10, as is shown 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 modulating or varying the refractive index n adjacent to the lateral edges 12a, 12b of the ridge 10 or, in the example shown, the strip-shaped ridge area 10a is produced. 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, the following in connection with 8a,b until 11a,b In the examples described, a plurality of refractive index variation regions 14, 14', 15, 15' are additionally produced in the active layer 2, specifically 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', each within the ridge 10, more precisely in the laterally protruding first ridge area 10b arranged adjacent to the first lateral edge 12a or in the laterally protruding second ridge area 10b' adjacent to the second lateral edge 12b are formed. In the two in 8a,b In the examples shown, the respective refractive index variation range 14, 14' has a maximum distance A _max from 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 The refractive index varying region 14, 14' shown 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 an essentially 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 FIG 8a is 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 region of the trenches 16. In contrast, in two intermediate regions 17, which each separate two adjacent trenches 16 from one another, the refractive index n corresponds to the refractive index of the semiconductor material of the web 10. The variation in the refractive index n produced in this way causes the in 2 shown higher laser modes extend in the lateral direction X more strongly away from the center of the ridge 10 into the unpumped, laterally protruding ridge regions 10b, 10b' than would be the case without the refractive index varying region 14, 14`. Therefore, the contribution of the higher laser modes to the emitted laser radiation 8 decreases and thus their beam quality increases.

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

At the in 8a,b example shown, the three trenches 16 each have an identical, predetermined width b. The intermediate regions 17 also have an identical, predetermined width B, which is greater than the width b of the trenches 16 in the example shown, but does not necessarily have to be greater than the width b of the trenches 16 8a In the example shown, the trenches 16, together with the intermediate regions 17, produce a periodic lateral variation in the refractive index n, which is 8a can be seen below. It goes without saying, however, 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, resulting in an aperiodic lateral structure or an aperiodic variation of the refractive index n in the respective refractive index -Variation range 14, 14' can be generated. It is also not absolutely necessary for the web 10 to have two refractive index variation areas 14, 14'; instead, only a single refractive index variation area 14 can be on the first lateral edge 12a or only a single refractive index variation area 14' on the second lateral edge 12b can be formed.

while in 8a,b the refractive index varying regions 14, 14' are formed only in the two lateral web regions 10b, 10b' are in FIG 9a,b example shown, 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 from the respectively adjacent lateral edge 12a, 12b, for which A _max / d < 0.5, in particular A _max / d < 0, applies. 4. As in 9a can be seen, the distance A _max is measured from the side facing away from the first lateral edge 12a of the trench 16 furthest away from the first lateral edge 12a. in the in 9a,b In the example shown, the two refractive index varying 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 areas 17 can be as described in connection with FIG 8a,b described can be chosen either periodically or aperiodically.

Also with the in 9a,b In the example shown, it is not absolutely necessary for the web 10 to have two refractive index variation regions 15, 15′; 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 one Refractive index varying region 15' may be formed adjacent to the second lateral edge 12b in the stripe-shaped ridge region 10a.

It goes without saying that the number of two or three trenches is 16 in 8a,b or. 9a,b and in the further illustrations is merely an example and that the refractive index varying regions 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 may have. Instead of trenches 16, other lateral structures can also be used in order to produce a refractive index variation. For example, a doping limited to a respective lateral area, a laser material treatment of the semiconductor material in a respective lateral area of the active layer 2, etc. can serve for this purpose.

At the in 9a,b In the example shown, the respective refractive index variation ranges 15, 15' extend in the longitudinal direction Y not beyond the length L ₁ of the laterally protruding web area 10b, 10b' at the first or at the second lateral edge 12a, 12b of the strip-shaped web area 10a. More precisely, the length of the two refractive index varying 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 varying 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 varying regions 15, 15' can extend in the longitudinal direction Y over the entire extension of the strip-shaped web region 10a between the two mirror surfaces 9a, b, as is shown in 9a,b is indicated by dashed lines.

10a,b show the active layer 2 or the ridge 10 in an example which shows the 8a,b and in 9a,b shown refractive index variation ranges 14, 14 ', 15, 15' combined, so that the web 10 has a total of four refractive index variation ranges 14, 15, 14 ', 15', each adjacent to the first edge 12a and adjacent to the second edge 12b of the strip-shaped land area 10a are arranged. A first and second refractive index varying region 14, 15 are formed adjacent to the first edge 12a in the protruding ridge region 10b and in the strip-shaped ridge region 10a. Correspondingly, a third and fourth refractive index varying region 14', 15' are formed adjacent to the second edge 12b in the associated projecting ridge region 10b' and in the strip-shaped ridge region 10a, respectively.

In order to increase the efficiency of the suppression of the higher modes, two or more laterally protruding ridge regions can also be formed on one and the same lateral edge 12a, 12b of the strip-shaped ridge region 10a. 11a,b shows this by way of example for the case in which two laterally projecting web areas 10b, 10c are formed on the first lateral edge 12a, which are spaced apart from one another in the longitudinal direction Y. Correspondingly, two laterally protruding web areas 10b′, 10c′ are formed on the second lateral edge 12b, which are also spaced apart from one another in the longitudinal direction Y. Two opposite web areas 10b, 10b ', 10c, 10c' are in the in 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.

At the in 11a,b In the example shown, a refractive index variation region 15 is formed adjacent to the first edge 12a within the first strip-shaped ridge region 10a, which extends in the longitudinal direction Y only over the respective length L ₁ of the two ridge regions 10b, 10c projecting laterally beyond the first edge 12a and over one Section 18 extends between the laterally projecting web areas 10b, 10c along the first lateral edge 12a. Correspondingly, on the second edge 12b of the strip-shaped web area 10a, in the longitudinal direction Y, there is only a respective (first) length L ₁ of the two refractive index variation areas 10b', 10c' adjoining the second lateral edge 12b and over a section 18 between the two laterally protruding web areas 10b', 10c' extending refractive index variation area 15' is formed. Alternatively, you can also contact the in 11a,b example shown, a respective refractive index variation region 15, 15' in the longitudinal direction Y over the entire length of the strip-shaped web region 10a, as is shown in FIG 11a,b is indicated by dashed lines.

It goes without saying that the arrangement and the number of 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 that have protruding web regions that are designed differently than those described above, starting from a first length L ₁ broadening web areas 10b, 10b ', 10c, 10c', for example with projecting web areas, as in the U.S. 8,396,091 are described, which is incorporated by reference in its entirety into the content of this application.

In all of 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 is shown in FIG 3 is shown. Because of the (wing-shaped) protruding strip-shaped ridge areas 10b, 10b', 10c, 10c' and possibly because of the additionally present refractive index varying regions 14, 14', 15, 15', despite the greater width d of the strip-shaped ridge area 10a, the higher laser Modes are suppressed and good beam quality can be ensured as a result. A trained in the manner described above The third semiconductor laser chip 1 also has the advantages of semiconductor laser chips 1 with ridges 10 of great 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, in particular at high power levels, and a high Reliability.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US8396091 [0014, 0063, 0082]
• DE 102008014093 A1 [0016]

Claims (15)

Semiconductor laser chip (1) for emitting laser radiation (8), comprising: an active layer (2) with a ridge (10) which has a strip-shaped ridge region (10a) with a lateral direction (X) preferably constant width d, wherein at least one web area (10b, 10b`) protruding laterally beyond the strip-shaped web area (10a) adjoins a first and/or a second lateral edge (12a, 12b) of the strip-shaped web area (10a), characterized in that a length of the laterally protruding web area (10b, 10b', 10c, 10c`) in the longitudinal direction (Y) starting from a first length L ₁ at the first or at the second lateral edge (12a, 12b) of the strip-shaped web area (10b, 10b', 10c, 10c') to a second length L ₂ , where the following applies: L ₂ > 1.2 L ₁ , preferably L ₂ > 1.3 L ₁ . semiconductor laser chip claim 1 , in which the laterally protruding web area (10b, 10b', 10c, 10c') is trapezoidal and preferably runs mirror-symmetrically to the lateral direction (X). semiconductor laser chip claim 2 , in which two legs (13a, 13b) of the trapezoidal protruding web area (10b, 10b', 10c, 10c') are 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 area (10a) are aligned. Semiconductor laser chip according to one of the preceding claims, in which the laterally projecting web region (10b, 10b', 10c, 10c') has a width ds in the lateral direction (X), for which the following applies: ds > 0.5 d. Semiconductor laser chip according to one of the preceding claims, in which the width d of the strip-shaped ridge region (10) is between 10 µm and 250 µm, preferably between 100 µm and 250 µm. Semiconductor laser chip according to the preamble of claim 1 , In particular 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 adjacent to the first lateral edge (12a) or to the second lateral edge (12b) of the strip-shaped web area (10a), the refractive index varying area (14, 14' 15, 15') having a maximum distance A _max from the first lateral edge (12a) or from the second lateral edge (12b). , which is given by A _max / d < 0.5, preferably A _max / d < 0.4. semiconductor laser chip 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`), the at least one refractive index variation region (14, 14') preferably extending in the longitudinal direction ( Y) does not extend beyond the first length L <sub>1</sub> of the laterally projecting web area (10b, 10b`). semiconductor laser chip claim 6 , wherein the at least one refractive index variation region (15, 15 ') between the first edge (12a) and the second edge (12b) of the strip-shaped web region (10) is formed. semiconductor laser chip claim 6 , in which at least one refractive index variation area (15, 15') is formed between the first edge (12a) and the second edge (12b) of the strip-shaped web area (10a) and in which at least one refractive index variation area (14, 14') is formed in the at least one laterally projecting web area (10b, 10b', 10c, 10c'). semiconductor laser chip claim 8 or 9 , in which 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 ridge region (10a), extends in the longitudinal direction (Y) over the entire extent of the strip-shaped web area (10a). Semiconductor laser chip according to one of 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 ridge region (10), does not extend in the longitudinal direction (Y) over the Length L ₁ of the laterally projecting web area (10b, 10b', 10c, 10c') at the first or at the second lateral edge (12a, 12b). Semiconductor laser chip according to one of Claims 8 or 9 in which at least two laterally protruding web areas (10b, 10c) adjoin the first edge (12a) of the strip-shaped web area (10a) and/or in which at least two laterally adjoin the second edge (12b) of the strip-shaped web area (10a). protruding ridge areas (10b', 10c'), wherein the at least one refractive index varying area (15, 15') formed between the first edge (12a) and the second edge (12b) of the strip-shaped ridge area (10) itself in longitudinal direction (Y) only over the respective length L ₁ of the at least two laterally projecting web areas (10b, 10c; 10b', 10c`) and over a section (18) between the laterally projecting web areas (10b, 10c; 10b', 10c ') at the first lateral edge (12a) or at the second lateral edge (12b). Semiconductor laser chip according to one of 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), 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, in which two mirror surfaces (9a, 9b) are formed on two opposite sides of the active layer (2), to which the strip-shaped ridge region (10a) of the ridge (10) adjoins. 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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