Semiconductor laser chip and laser arrangement

Abstract

A semiconductor laser chip (1) is specified, comprising: - a substrate (2) having a waveguide (3), wherein the waveguide (3) forms part of an optical resonator or an optical amplifier of the semiconductor laser chip (1), - a laser-active material (4) embedded in the substrate (2), and - a light source (5) arranged on or above the substrate (2), wherein - the light source (5) optically pumps the laser-active material (4) during operation, so that electromagnetic laser radiation (6) is generated and propagates within the waveguide (3). Furthermore, a laser arrangement is specified.

Description

[0001] A semiconductor laser chip and a laser arrangement are specified.

[0002] One objective of certain embodiments is to provide a semiconductor laser chip and a laser arrangement that are particularly compact. This objective is achieved by the semiconductor laser chip and the laser arrangement with the features according to the independent claims.

[0003] Advantageous embodiments and further developments of the semiconductor laser chip and the laser arrangement are specified in the dependent claims.

[0004] According to one embodiment, the semiconductor laser chip has a substrate comprising a waveguide, wherein the waveguide forms part of an optical resonator or optical amplifier of the semiconductor laser chip. For example, the waveguide is integrated into or embedded in the substrate, or the waveguide is arranged on the substrate. In particular, the waveguide extends parallel to a principal extension plane of the substrate.

[0005] For example, the substrate comprises a support, a first cladding layer, a waveguide layer, and a second cladding layer arranged on a principal surface of the support, preferably in that order. In particular, the waveguide is arranged between the first cladding layer and the second cladding layer. It is also possible for the first cladding layer to act as the support, thus eliminating the need for an additional support. For example, the support and / or the waveguide layer comprises or consists of a semiconducting material, such as silicon, gallium arsenide, indium phosphide, aluminum nitride, or gallium nitride. For example, the first cladding layer and / or the second cladding layer comprises or consists of an oxide, such as silicon dioxide or aluminum oxide.

[0006] For example, during operation of the semiconductor laser chip, electromagnetic radiation in a wavelength range between infrared and ultraviolet light propagates within the waveguide. The waveguide may support a single propagating electromagnetic mode. It is also possible for the waveguide to support two or more propagating electromagnetic modes.

[0007] In particular, the first and second cladding layers are configured to confine the electromagnetic radiation at least partially vertically within the waveguide. Here and in the following, "vertical" refers to a direction perpendicular to the principal plane of extension of the substrate. Specifically, the refractive index of the first and second cladding layers is lower than the refractive index of the waveguide layer.

[0008] For example, the waveguide layer is structured in the horizontal direction to confine the electromagnetic radiation, at least partially, in the horizontal direction. For instance, the waveguide layer has a limited spatial extent or width in the horizontal direction. Here and in the following, "horizontal" refers to a direction parallel to the principal extension plane of the substrate. In particular, the electromagnetic radiation is confined in a horizontal direction that is perpendicular to any propagation direction of the electromagnetic radiation within the waveguide.

[0009] For example, the width and / or height of the waveguide is at most ten times the wavelength of the electromagnetic radiation, or is at most equal to the wavelength of the electromagnetic radiation. For example, the width and / or height of the waveguide is at most 10 micrometers, or at most 1 micrometer. Here and in the following, the width of the waveguide refers to a linear extent of the waveguide in the horizontal direction, perpendicular to the direction of propagation of the electromagnetic radiation within the waveguide. Here and in the following, the height of the waveguide refers to a linear extent of the waveguide in the vertical direction. For example, the waveguide is a buried waveguide, a ribbed waveguide, a finned waveguide, a strip waveguide, or a slotted waveguide.

[0010] According to another embodiment, the semiconductor laser chip comprises a laser-active material embedded in the substrate. In particular, the laser-active material is configured to generate electromagnetic laser radiation during operation due to stimulated emission of photons. For example, the laser-active material is optically and / or electrically pumped during operation of the semiconductor laser chip such that the electronic states in the laser-active material exhibit a population inversion.

[0011] The laser-active material is embedded, for example, in the first cladding layer, the second cladding layer, and / or the waveguide layer. It is also possible for the laser-active material to be arranged, for example, on the first cladding layer, on the second cladding layer, and / or on the waveguide layer. In particular, the laser-active material is arranged near the waveguide so that electromagnetic radiation generated in the laser-active material is coupled into the waveguide and / or so that electromagnetic radiation propagating in the waveguide can be at least partially absorbed by the laser-active material.For example, the laser-active material is arranged near the waveguide so that the electromagnetic radiation generated in the laser-active material is coupled into an optical mode of the waveguide and / or so that the optical mode of the waveguide interacts at least partially with the laser-active material.

[0012] For example, the laser-active material contains or consists of rare earth or transition metal ions. In particular, these ions can be directly embedded or doped into the substrate, for example, by ion implantation. Alternatively or additionally, these ions can be embedded or doped into a host material, such as a crystal, and the host material can, for example, be further embedded in the substrate.

[0013] According to another embodiment, the semiconductor laser chip has a light source arranged on or above the substrate. For example, the light source is a light-emitting semiconductor diode having a pn junction configured to convert electrical current into electromagnetic radiation during operation. In particular, the light source generates electromagnetic radiation by spontaneous emission. It is also possible that the light source is a laser, for example, a laser diode that emits electromagnetic laser radiation. In the latter case, the light source generates electromagnetic radiation by stimulated emission.

[0014] In particular, the light source is arranged such that a light-emitting surface of the light source faces the substrate and / or the laser-active material. In other words, the electromagnetic radiation emitted by the light source during operation is coupled into the substrate and at least partially absorbed by the laser-active material during operation. Specifically, a wavelength of the electromagnetic radiation emitted by the light source is adjusted to correspond to an absorption wavelength of the laser-active material. For example, the light source emits electromagnetic radiation in a spectral range between infrared and ultraviolet light during operation.

[0015] The semiconductor laser chip can also have two, three, or a plurality of light sources. These two, three, or plurality of light sources can be identical or different. For example, the two, three, or plurality of light sources can emit electromagnetic radiation with the same wavelength or with different wavelengths. For example, the two, three, or plurality of light sources can have the same dimensions or different dimensions. For example, the plurality of light sources can be arranged as an array of light sources on the substrate. For example, at least two light sources can be arranged on opposite sides of the substrate facing each other, such that the laser-active material is located between the two light sources.

[0016] According to another embodiment of the semiconductor laser chip, the light source optically pumps the laser-active material during operation, so that electromagnetic laser radiation is generated and propagates within the waveguide. In particular, the optically pumped laser-active material, together with the optical resonator, which is partially formed by the waveguide, is configured to generate electromagnetic laser radiation during the operation of the semiconductor laser chip.

[0017] Alternatively or additionally, the optically pumped laser-active material, together with the waveguide, forms an optical amplifier that amplifies the electromagnetic radiation propagating in the waveguide. In particular, the electromagnetic radiation propagating along the waveguide excites the emission of photons by the pumped laser-active material, leading to an amplification of the electromagnetic radiation propagating in the waveguide.

[0018] Electromagnetic laser radiation is generated by stimulated emission and, compared to electromagnetic radiation generated by spontaneous emission, has a greater coherence length, a smaller spectral bandwidth and / or a higher degree of polarization.

[0019] According to a preferred embodiment, the semiconductor laser chip comprises: - the substrate that incorporates the waveguide, wherein the waveguide forms part of the optical resonator or optical amplifier of the semiconductor laser chip, - the laser-active material embedded in the substrate, and - the light source, which is arranged on or above the substrate, wherein - the light source optically pumps the laser-active material during operation, so that electromagnetic laser radiation is generated and propagated within the waveguide.

[0020] The semiconductor laser chip described here is based on the idea of ​​using a light-emitting diode (LED) as a pump source to excite the laser-active material, which is directly embedded in a photonic integrated circuit. The latter forms the optical resonator for the laser or part of the optical amplifier. Accordingly, the semiconductor laser chip advantageously offers a wide range of design possibilities.

[0021] For example, no direct electrical contacts are required for contacting the laser-active material, leading to greater design freedom regarding the integration of the laser-active material into the substrate. In particular, the optical resonator can be designed to be particularly low-loss, for example, by using transparent materials with low optical losses for the waveguide. Similarly, the waveguide of the optical amplifier is designed to be particularly low-loss.

[0022] Furthermore, the semiconductor laser chip described here can be easily integrated into photonic integrated circuits. For example, no complicated adjustment is required to couple the electromagnetic laser radiation generated by the semiconductor laser chip into a photonic integrated circuit, since the electromagnetic laser radiation is generated directly within the photonic integrated circuit.

[0023] Various laser-active materials can be used to generate electromagnetic laser radiation at different wavelengths. Furthermore, the emission wavelength of the light source, such as a light-emitting diode (LED), can be matched to the absorption wavelength of the laser-active material, enabling the creation of semiconductor laser chips with a broad spectrum of emission wavelengths. For example, two or more semiconductor laser chips emitting electromagnetic laser radiation at the same or different wavelengths can be combined in a single photonic integrated circuit on a common substrate.

[0024] Furthermore, the size of the light source can be adapted to the dimensions of the waveguide, for example, by using one or more micro-LEDs as the light source. The micro-LED can, for instance, have an elongated form factor adapted to the shape of the waveguide. Accordingly, the efficiency of the semiconductor laser chip can be increased and / or the semiconductor laser chip can be made particularly compact.

[0025] According to another embodiment of the semiconductor laser chip, the optical resonator comprises two mirror elements arranged at opposite ends of the waveguide, or the optical amplifier comprises a mirror element arranged at one end of the waveguide. In particular, the waveguide together with the two mirror elements forms the optical resonator. For example, one of the mirror elements has a high reflectivity, while the other mirror element is partially reflective to electromagnetic radiation propagating within the waveguide. Specifically, electromagnetic laser radiation is coupled out of the semiconductor laser chip via the partially reflective mirror element.For example, the highly reflective mirror element has a reflectance of at least 99%, while the partially reflective mirror element has a reflectance between 2% and 80% inclusive for the electromagnetic radiation propagating in the waveguide. The mirror elements may, for example, be made of metal or a Bragg mirror.

[0026] It is also possible for the semiconductor laser chip to have only a single reflective mirror element located at one end of the waveguide, thus realizing a reflective semiconductor optical amplifier (RSOA). Furthermore, the optical amplifier can also be implemented without mirror elements at both ends of the waveguide. In the latter case, the semiconductor laser chip functions as a transmission optical amplifier.

[0027] In other words, in some embodiments the semiconductor laser chip may have two mirror elements at both ends of the waveguide, have one mirror element at one end of the waveguide while the other end is free of a mirror element, or the semiconductor laser chip may have no mirror elements.

[0028] According to another embodiment of the semiconductor laser chip, at least one mirror element comprises or consists of a photonic crystal. For example, the mirror element comprises or consists of a one-dimensional photonic crystal configured to at least partially reflect incident electromagnetic radiation propagating within the waveguide during operation.

[0029] In particular, the photonic crystal exhibits a spatial modulation of the refractive index for electromagnetic radiation. For example, the spatial modulation is periodic or superperiodic. This spatial modulation is achieved, for instance, by forming a multitude of holes, especially micro- or nanoholes, within the waveguide or waveguide layer. These holes may be filled with air or with a dielectric material that has a different refractive index than the waveguide material.

[0030] For example, the spatial modulation of the refractive index extends in one, two, or three linearly independent directions. In other words, the photonic crystal is one-, two-, or three-dimensional. In particular, the photonic crystal exhibits a photonic band gap, such that photons with energies within the photonic band gap cannot propagate through the photonic crystal. The photonic band gap arises, for example, from destructive interference of electromagnetic radiation scattered by different regions of the photonic crystal. Specifically, the photonic crystal forms a Bragg mirror for reflecting incident electromagnetic radiation that propagates within the waveguide.

[0031] According to another embodiment of the semiconductor laser chip, the optical resonator or the optical amplifier is designed as a photonic integrated circuit. For example, elements of the optical resonator or the optical amplifier, such as the waveguide and / or the mirror elements, are integrated, embedded, or fabricated on a common substrate using a CMOS process (CMOS stands for "Complementary Metal-Oxide-Semiconductor" process).

[0032] According to another embodiment of the semiconductor laser chip, the optical resonator or the optical amplifier is coupled to and / or extends into a photonic integrated circuit. For example, the photonic integrated circuit is formed on the same substrate as the semiconductor laser chip, so that the waveguide is directly coupled to the photonic integrated circuit.

[0033] According to another embodiment of the semiconductor laser chip, the laser-active material is arranged within the waveguide and / or in an evanescent field region of the waveguide. In particular, the laser-active material is arranged in the evanescent field region of the waveguide if the evanescent field of the electromagnetic laser radiation propagating within the waveguide at least partially penetrates the laser-active material and / or is optically coupled to the laser-active material. For example, the distance between the laser-active material and the waveguide is at most one-quarter of the wavelength of the electromagnetic radiation propagating in the waveguide during operation of the semiconductor laser chip. For example, the distance between the laser-active material and the waveguide is at most 100 nanometers for electromagnetic radiation in the green spectral range.

[0034] According to another embodiment of the semiconductor laser chip, the laser-active material incorporates laser-active ions embedded within the substrate. For example, the laser-active ions are implanted into the substrate using an ion implantation process. Specifically, the laser-active ions are implanted into the substrate, the first cladding layer, the waveguide layer, and / or the second cladding layer. For example, the substrate is exposed to accelerated laser-active ions using a predefined mask to implant the laser-active ions in a predefined area and depth within the substrate. It is also possible for the laser-active material to comprise or consist of a semiconductor material. In this case, the laser-active material may, for example, have a pn junction and / or quantum well structures configured to generate electromagnetic radiation.

[0035] According to another embodiment of the semiconductor laser chip, the laser-active ions are selected from the following group: Pr3+, Tb3+, Dy3+, Tm3+, Ho3+ and combinations thereof.

[0036] According to another embodiment of the semiconductor laser chip, the laser-active material forms a layer within the substrate. In particular, the layer is arranged within the waveguide or in the evanescent field region of the waveguide. For example, the layer of laser-active material is deposited during the formation of the waveguide layer or during the formation of one of the cladding layers. For example, laser-active ions are implanted into the substrate so that a layer of laser-active material is formed.

[0037] According to another embodiment of the semiconductor laser chip, the laser-active material comprises a crystal of a host material doped with laser-active ions. In particular, the host material comprises or consists of an oxide or a fluoride, such as yttrium lithium fluoride (YLF), barium yttrium fluoride (BYF), or yttrium aluminum garnet (YAG).

[0038] According to another embodiment of the semiconductor laser chip, the light source incorporates a micro-LED. Micro-LEDs (micro light-emitting diodes, or micro-LEDs for short) are semiconductor light-emitting diodes of a particularly small size. For example, a growth substrate for epitaxial growth of a semiconductor layer sequence of the micro-LED is removed from the micro-LED. In other words, the micro-LED does not encompass the growth substrate. For example, the thickness or height of the micro-LED in one growth direction of the semiconductor layer sequence is between 1.5 micrometers and 10 micrometers.

[0039] The light-emitting surface of the micro-LED can be rectangular or have another shape. Specifically, any lateral extent of the light-emitting surface, viewed from above the layers of the semiconductor sequence, is at most 100 micrometers or at most 70 micrometers. For example, if the micro-LED has a rectangular shape, any edge length of the micro-LED—particularly viewed from above the layers of the semiconductor sequence—is at most 70 micrometers or at most 50 micrometers. For example, the rectangular light-emitting surface of the micro-LED has a width between 1 micrometer and 10 micrometers inclusive, and a length between 10 micrometers and 70 micrometers inclusive.

[0040] For example, micro-LEDs are mounted on wafers with removable supports, allowing the micro-LED to be detached from the wafer without damage. Micro-LEDs can also be referred to as µLEDs, µ-LEDs, uLEDs, u-LEDs, or micro light-emitting diodes.

[0041] According to another embodiment of the semiconductor laser chip, a light-emitting surface of the light source is in direct contact with a major surface of the substrate. For example, the light source is an LED or micro-LED with a light-emitting surface that is glued to or directly bonded to the substrate. For example, the light source is bonded directly to the cladding layer or to the waveguide. Particularly thin electrical contacts for external electrical contacting of the light source can be formed, for example, by directly bonding the light source to the cladding layer, which may contain, for example, SiO2 and / or indium tin oxide (ITO), under pressure and temperature. It is also possible to position the light source on a back plane of the substrate, i.e., on a surface of the substrate opposite the waveguide.

[0042] According to another embodiment of the semiconductor laser chip, the waveguide is arranged between two cladding layers. A cavity is formed in one of the cladding layers, and the light source is located within this cavity. In other words, the cavity is formed by partially exposing the waveguide, i.e., by partially removing one of the cladding layers from the waveguide. Specifically, the light source is located directly on the waveguide. For example, the laser-active material is arranged as a layer deposited on the light-emitting surface of the light source.

[0043] According to another embodiment of the semiconductor laser chip, a reflective layer is arranged on the side of the substrate opposite the light source. For example, the reflective layer is configured to reflect electromagnetic radiation emitted by the light source and transmitted through the laser-active material back towards the laser-active material. Accordingly, the absorption rate and thus the efficiency of the semiconductor laser chip can be increased.

[0044] According to another embodiment of the semiconductor laser chip, the reflective layer comprises or consists of a metal, a Bragg mirror, and / or a retroreflective structure. For example, the Bragg mirror comprises a plurality of alternating dielectric layers with different refractive indices. For example, the retroreflective structure comprises prisms and / or other optical elements for retroreflecting incident electromagnetic radiation.

[0045] According to another embodiment of the semiconductor laser chip, a heating element is arranged in or on the substrate near the laser-active material. For example, the emission wavelength of the electromagnetic laser radiation emitted by the semiconductor laser chip during operation is adjusted by changing the temperature of the laser-active material using the heating element.

[0046] Furthermore, a laser arrangement is specified. In particular, the laser arrangement includes a semiconductor laser chip described herein. All features of the semiconductor laser chip are also disclosed for the laser arrangement, and vice versa.

[0047] According to one embodiment, the laser arrangement comprises at least two semiconductor laser chips as described herein, wherein the waveguides of the at least two semiconductor laser chips share a common substrate. For example, a single light source is arranged on the common substrate to pump the laser-active materials of the two semiconductor laser chips. Alternatively, two separate light sources are arranged on the common substrate to pump the two laser-active materials belonging to the two semiconductor laser chips.

[0048] According to a further embodiment of the laser arrangement, the at least two semiconductor laser chips emit electromagnetic laser radiation with the same wavelength or with different wavelengths. Alternatively or additionally, the spectral linewidths of the electromagnetic laser radiation emitted by the at least two semiconductor laser chips are the same or different.

[0049] According to another embodiment of the laser arrangement, the at least two semiconductor laser chips comprise a first semiconductor laser chip and a second semiconductor laser chip, which are cascaded such that the electromagnetic laser radiation emitted by the first semiconductor laser chip is used for optical pumping of the second semiconductor laser chip. Furthermore, the laser arrangement can be configured to generate electromagnetic laser radiation with multiple and / or different wavelengths in a single waveguide.

[0050] Further advantageous embodiments and developments of the semiconductor laser chip and the laser arrangement can be seen from the following exemplary embodiments, which are described in conjunction with the figures.

[0051] The Fig. 1 and Fig. Figure 2 shows schematic top views of semiconductor laser chips according to various embodiments.

[0052] The Fig. Figures 3 to 12 show schematic cross-sectional views of semiconductor laser chips according to various embodiments.

[0053] The Fig. 13 and Fig. Figure 14 shows schematic top views of laser arrangements according to various embodiments.

[0054] Fig. Figure 15 shows a schematic top view of a semiconductor laser chip according to a further embodiment.

[0055] Elements that are identical, similar, or have the same effect are marked with the same reference symbols in the figures. The figures and the proportions of the elements depicted in the figures are not to scale. Rather, individual elements, such as layer thicknesses, may be exaggerated for clarity and / or better understanding.

[0056] Fig. Figure 1 shows a top view of the main surface 21 of a substrate 2 of a semiconductor laser chip 1 according to an exemplary embodiment. The semiconductor laser chip 1 comprises a substrate 2 with an integrated waveguide 3 for electromagnetic laser radiation 6 (not shown) and a laser-active material 4 embedded in the substrate 2. Furthermore, a light source 5 in the form of a micro-LED is arranged face down directly on the main surface 21 of the substrate 2. The light source serves to optically pump the laser-active material 4 during operation of the semiconductor laser chip 1.

[0057] The waveguide 3 has a width W1 of 1 micrometer and includes a tapered region 31 in which the width W1 of the waveguide 3 increases monotonically to match the dimensions of the light source 5. Depending on the width W1, the waveguide 3 is, for example, a single-mode waveguide or a multi-mode waveguide. Furthermore, the width W1 of the waveguide 3 depends on the wavelength of the electromagnetic laser radiation 6 emitted by the semiconductor laser chip 1 during operation. In other words, the tapered section 31 of the waveguide 3 compensates for the difference between the width W1 of the waveguide 3 and the width W2 of the light source 5. Specifically, the micro-LED 5 has a rectangular shape with a width W2 of approximately 5 micrometers and a length L of approximately 10 micrometers when viewed from the substrate 2. The width W1 of the waveguide 3 thus increases in the tapered section 31 to match the width W2 of the micro-LED 5.In particular, the length or opening angle of the tapered region 31 is chosen such that scattering of the electromagnetic laser radiation 6 within the waveguide is minimized.

[0058] Mirror elements 7 in the form of photonic crystal reflectors are arranged on opposite sides of the waveguide 3. Each mirror element 7 has a plurality of holes 71 formed in the waveguide 3. Alternatively or additionally, the mirror element 7 comprises a plurality of pillars near the waveguide 3, and / or the width W1 or height of the waveguide 3 changes periodically along the propagation direction of the electromagnetic laser radiation 6 within the waveguide 3. For example, a structure that causes a periodic modulation of a refractive index profile along the waveguide 3 can be used as a mirror element 7. The holes 71 cause a spatial modulation of the refractive index for the electromagnetic laser radiation 6 propagating within the waveguide 3.In particular, the holes 71 are arranged such that the electromagnetic laser radiation 6 is at least partially Bragg-reflected by the mirror elements 7. Accordingly, the waveguide 3 together with the mirror elements 7 forms a high-Q optical resonator for the electromagnetic laser radiation 6. Here, "high Q factor" refers to a high quality factor of the optical resonator, where the quality factor is proportional to the ratio between the resonant frequency of the optical resonator and its resonant bandwidth. For example, the high-Q optical resonator has a quality factor of at least 10,000 to achieve a low-threshold laser. One of the mirror elements 7 is highly reflective, while the other mirror element 7 is partially reflective, so that electromagnetic laser radiation 6 is coupled out of the optical resonator during operation.

[0059] The laser-active material 4 consists of laser-active ions, in particular rare-earth ions such as Pr³⁺, Tb³⁺, Dy³⁺, Tm³⁺, or Ho³⁺, which are introduced into the substrate 2 by ion implantation. It is also possible that the laser-active material 4 comprises or consists of a semiconductor material. The laser-active material 4 forms a layer that is arranged in an evanescent field region of the waveguide 3, such that photons generated in the laser-active material 4 are coupled into the waveguide 3 or into an optical mode of the waveguide 3. Alternatively or additionally, the layer of laser-active material 4 can also be formed directly inside the waveguide 3.

[0060] The layer of laser-active material 4 has a rectangular shape when viewed from above on the substrate 2, with its length and width being slightly larger and equal to the length L and width W2 of the light source 5. Consequently, the pump light emitted by the light source 5 during operation strikes the laser-active material 4 completely or almost completely, where it is at least partially absorbed. This reduces pump light losses and increases the efficiency of the semiconductor laser chip 1.

[0061] During operation of the semiconductor laser chip 1, the light source 5 optically pumps the laser-active material 4, which serves as an amplification medium for the semiconductor laser chip 1. Accordingly, a population inversion of the electronic states is achieved in the laser-active material 4. The laser-active material 4 is optically coupled to the optical resonator formed by the waveguide 3 and the mirror elements 7 and thus emits electromagnetic laser radiation 6 by stimulated emission. The electromagnetic laser radiation 6 propagates within the waveguide 3 and is at least partially coupled out of the waveguide via one of the mirror elements 7, which has a lower reflectivity for the electromagnetic laser radiation 6 than the other mirror element 7.

[0062] Fig. Figure 2 shows a top view of the main surface 21 of a substrate 2 of a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Figure 1, the light source 5 has a different form factor. Specifically, the light source 5 is a micro-LED with a linear form factor and has a width W2 of approximately 1 micrometer and a length L of approximately 100 micrometers, while the waveguide 3 has a width W1 of at most 1 micrometer. The width W2 of the light source 5 is therefore equal to, or approximately equal to, the width W1 of the waveguide 3. Accordingly, no tapered region 31, or only a slightly tapered region 31, of the waveguide 3 is required to compensate for the difference between the width W1 of the waveguide 3 and the width W2 of the light source 5.

[0063] Fig. Figure 3 shows a cross-sectional view of a semiconductor laser chip 1 according to one of the [references / documents] in connection with the [references / documents]. Fig. 1 and Fig. The embodiments described in Figure 2 are as follows: The substrate 2 has the waveguide 3, which is arranged vertically between a first cladding layer 91 and a second cladding layer 92. In particular, the vertical direction is perpendicular to the main surface 21 of the substrate 2. It is also possible that the first cladding layer 91 and the second cladding layer 92 are formed as a single, common cladding that surrounds the waveguide on all sides except the end faces where the mirror elements 7 are arranged. The cladding layers 91, 92 have a material that has a lower refractive index than the waveguide 3. For example, the waveguide 3 is made of Si or SiN, while the cladding layers 91, 92 are made of SiO2.

[0064] The light-emitting surface 51 of the light source 5 is bonded directly to the main surface of the substrate 21. In other words, the light-emitting surface 51 of the light source 5 is bonded directly to the second cladding layer 92.

[0065] The layer of laser-active material 4 is embedded in the second cladding layer 92 at a distance D from the waveguide 3, which is at most one quarter of the wavelength of the electromagnetic laser radiation 6. It is also possible that the layer of laser-active material 4 is embedded in the first cladding layer 91.

[0066] Fig. Figure 4 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Section 3, the layer of laser-active material 4 is directly embedded in the waveguide 3. Accordingly, optical coupling between the laser-active material 4 and the waveguide 3 can be improved.

[0067] Fig. Figure 5 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in section 4, the second cladding layer 92 is removed, and the waveguide 3 is exposed in a region where the laser-active material 4 is located. In other words, a cavity 10 is formed within the second cladding layer 92, in which the light source 5 is located. Specifically, the light source 5 is directly bonded to the waveguide 3.

[0068] Fig. Figure 6 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Figure 3, a plurality of light sources 5 in the form of a micro-LED array are arranged on the main surface 21 of the substrate 2. This increases the overall pumping energy, while the arrangement of the micro-LEDs is adapted to the shape of the waveguide and / or the shape of the layer of laser-active material 4. Furthermore, this configuration enables lasers with a particularly low threshold due to the increased gain. Accordingly, the reflectivity of the mirror elements 7 can be reduced.

[0069] Fig. Figure 7 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Section 3, the layer of laser-active material 4 is embedded in the first cladding layer 91. Furthermore, a reflective layer 11 is arranged on a side of the first cladding layer 91 facing away from the waveguide 3. Specifically, in a top view of the main surface 21 of the substrate, the reflective layer 11 completely overlaps the layer of active material 4. The reflective layer 11 comprises a metal and reflects at least some of the pump light emitted by the light source 5, which is not absorbed by the laser-active material 4, back to the laser-active material 4.

[0070] Furthermore, a reflective layer 11, comprising a metal, is arranged on the main surface 21 of the substrate 2, i.e., on one side of the second cladding layer 92 facing away from the waveguide 3. The reflective layer 11 completely surrounds the light source 5. Together, the two reflective layers 11 increase the optical path length of the pump light within the laser-active material 4 and thus increase the absorption probability of the pump light by the laser-active material 4, thereby also reducing the lasing threshold.

[0071] Fig. Figure 8 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Section 7, the reflective layer 11, which is arranged on the side of the first cladding layer 91 facing away from the waveguide 3, is designed as a retroreflective structure 112. In particular, the retroreflective structure 112 is a surface structuring of the first cladding layer 91 in the form of prisms or other optical elements that are arranged for the retroreflection of the incident pump light emitted by the light source 5.

[0072] Fig. Figure 9 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Section 9, the reflective layer 11, which is arranged on the side of the first cladding layer 91 facing away from the waveguide 3, is designed as a Bragg mirror 111. In particular, the Bragg mirror 111 comprises a plurality of alternating dielectric layers with different refractive indices, which are configured to reflect the incident pump light emitted by the light source 5.

[0073] Fig. Figure 10 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Figure 7, the reflective layer 11 is embedded in the first cladding layer 91. Furthermore, the laser-active material 4 comprises a crystal made of a host material 8, which is doped with laser-active ions. The crystal made of the host material 8 is embedded in the second cladding layer 92.

[0074] Fig. Figure 11 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in section 10, the crystal of the host material 8 doped with laser-active ions is directly embedded in the waveguide 3.

[0075] Fig. Figure 12 shows a semiconductor laser chip 1 according to a further embodiment. In contrast to the one in connection with Fig. In the semiconductor laser chip 1 described in Section 3, the layer of laser-active material 4 is embedded in the first cladding layer 91. Furthermore, the main surface 21 of the substrate 2 has a surface roughening 921 that at least partially scatters and deflects the incident pump light emitted by the light source 5. This increases the optical path length of the pump light within the laser-active material 4, thereby increasing the absorption probability of the pump light.

[0076] Furthermore, a heating element 12 is arranged on one side of the first cladding layer 91, facing away from the waveguide 3. The heating element 12 can be used to adjust a wavelength of the electromagnetic laser radiation 6 emitted by the semiconductor laser chip 1 during operation.

[0077] Fig. Figure 13 shows a top view of the main surface 21 of the substrate 2 of a laser arrangement 100 according to an exemplary embodiment. The laser arrangement 100 has two semiconductor laser chips 1 according to the illustration in conjunction with Fig. The embodiment described in Figure 1 is further described, wherein the waveguides 3 of the two semiconductor laser chips 1 are embedded in a common substrate 2. The two semiconductor laser chips 1 emit electromagnetic laser radiation 6 in the same wavelength range or in different wavelength ranges. It is also possible that the spectral linewidths of the electromagnetic laser radiation 6 emitted by the two semiconductor laser chips 1 are different or the same.

[0078] Fig. Figure 14 shows a laser arrangement 100 according to a further embodiment. The laser arrangement 100 comprises a first semiconductor laser chip 1a and a second semiconductor laser chip 1b according to the illustration in conjunction with Fig. The embodiment described in Figure 1 is based on the embodiment described above, with the difference that the second semiconductor laser chip 1b does not include a light source 5 for emitting pump light. The waveguides 3 of the first and second semiconductor laser chips 1a, 1b are embedded in a common substrate 2.

[0079] The first semiconductor laser chip 1a and the second semiconductor laser chip 1b form a cascaded arrangement. In particular, the electromagnetic laser radiation 6 emitted by the first semiconductor laser chip 1a is coupled into the waveguide 3 of the second semiconductor laser chip 1b, where it is at least partially absorbed by the laser-active material 4 of the second semiconductor laser chip 1b. In other words, the electromagnetic laser radiation 6 emitted by the first semiconductor laser chip 1a is used as pump light for optical pumping of the laser-active material 4 of the second semiconductor laser chip 1b.

[0080] The wavelengths of the electromagnetic laser radiation 6 emitted by the first and second semiconductor laser chips 1a, 1b differ. In particular, the photonic crystal mirror element 7 of the second semiconductor laser chip 1b exhibits low reflectivity for the electromagnetic laser radiation 6 emitted by the first semiconductor laser chip 1a. Accordingly, the electromagnetic laser radiation 6 emitted by the first semiconductor laser chip 1a can be readily coupled into the optical resonator of the second semiconductor laser chip 1b, where it is at least partially absorbed by the laser-active material 4.

[0081] It is also possible that the second semiconductor laser chip 1b does not have mirror elements 7, but instead has a pump light source 5 and forms an optical amplifier. In particular, the electromagnetic laser radiation 6 generated by the first semiconductor laser chip 1a is coupled out on a side of the waveguide 3 facing the second semiconductor laser chip 1b. The electromagnetic laser radiation 6 is then amplified in transmission by the second semiconductor laser chip 1b as it propagates along the waveguide 3. Specifically, the electromagnetic laser radiation 6 generated by the first semiconductor laser chip 1a excites the optically pumped laser-active material 4 of the second semiconductor laser chip 1b to emit photons, thereby amplifying the electromagnetic laser radiation 6.

[0082] Fig. Figure 15 shows a top view of the main surface 21 of a substrate 2 of a semiconductor laser chip 1 according to an exemplary embodiment. In comparison to the one in connection with Fig. In the semiconductor laser chip 1 described in Figure 1, the semiconductor laser chip 1 has only a single mirror element 7, which is arranged at one end of the waveguide 3. Specifically, the other end of the waveguide 3 is free of a mirror element 7 and instead has, for example, an antireflective coating. Accordingly, the semiconductor laser chip 1 implements a reflective optical semiconductor amplifier. Electromagnetic radiation coupled into the waveguide 3 via an end opposite the mirror element 7 propagates along the waveguide and stimulates the pumped laser-active material 4 to emit photons, thereby amplifying the electromagnetic radiation.

[0083] Due to the mirror element 7, the electromagnetic radiation is reflected once and passes through the pumped laser-active material 4 a second time before exiting the semiconductor laser chip 1 at the same end of the waveguide 3 where it was coupled into the semiconductor laser chip 1. Accordingly, the electromagnetic radiation is amplified twice by stimulating the pumped laser-active material 4 to emit photons.

[0084] It is also possible that the semiconductor laser chip 1 does not include a mirror element 7. In this case, the semiconductor laser chip 1 implements an optical amplifier that amplifies the electromagnetic radiation transmitted through the waveguide by stimulating the pumped laser-active material 4 to emit photons.

[0085] This patent application claims priority over German patent application DE 102023116227.6, the disclosure content of which is hereby incorporated by reference.

[0086] The invention is not limited to the embodiments described on the basis of these embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular includes any combination of features in the claims and any combination of features in the embodiments, even if this feature or combination itself is not expressly stated in the claims or embodiments. Reference sign 1 semiconductor laser chip 2 Substrat 21 Main area 3 waveguides 31 rejuvenated area 4 laser-active material 5 light sources 51 Light emission area 6 electromagnetic laser radiation 7 Mirror element 71 holes 8 Host material 91 first mantle layer 92 second mantle layer 921 Surface roughening 10 Cavity 11 reflective layer 111 Bragg mirrors 112 retroreflective structure 12 Heating element 100 laser arrangement 1a first semiconductor laser chip 1b second semiconductor laser chip Length L W1 Waveguide width W2 Width of the light source D distance QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102023116227.6

[0085]

Claims

[1] A semiconductor laser chip (1) comprising: - a substrate (2) having a waveguide (3), wherein the waveguide (3) forms part of an optical resonator of the semiconductor laser chip (1), - a laser-active material (4) embedded in the substrate (2), and - a light source (5) arranged on or above the substrate (2), wherein - the light source (5) optically pumps the laser-active material (4) during operation, so that electromagnetic laser radiation (6) is generated and propagates within the waveguide (3). [2] The semiconductor laser chip (1) according to the preceding claim, wherein - the optical resonator has two mirror elements (7) which are arranged at opposite ends of the waveguide (3). [3] The semiconductor laser chip (1) according to the previous claim, wherein at least one mirror element (7) comprises a photonic crystal. [4] The semiconductor laser chip (1) according to any one of the preceding claims, wherein - the optical resonator is designed as a photonic integrated circuit, or - the optical resonator is coupled to and / or extends into a photonic integrated circuit. [5] The semiconductor laser chip (1) according to one of the preceding claims, wherein the laser-active material (4) is arranged within the waveguide (3) and / or in an evanescent field region of the waveguide (3). [6] The semiconductor laser chip (1) according to any of the preceding claims, wherein the laser-active material (4) comprises laser-active ions embedded in the substrate (2). [7] The semiconductor laser chip (1) according to any of the preceding claims, wherein the laser-active ions are selected from at least one of: Pr3+, Tb3+, Dy3+, Tm3+ or Ho3+. [8] The semiconductor laser chip (1) according to one of the preceding claims, wherein the laser-active material (4) forms a layer within the substrate (2). [9] The semiconductor laser chip (1) according to one of the preceding claims, wherein the laser-active material (4) comprises a crystal of a host material (8) doped with laser-active ions. [10] The semiconductor laser chip (1) according to one of the preceding claims, wherein the light source (5) comprises a micro-LED. [11] The semiconductor laser chip (1) according to one of the preceding claims, wherein a light emission surface (51) of the light source (5) is in direct contact with a main surface (21) of the substrate (2). [12] The semiconductor laser chip (1) according to any one of the preceding claims, wherein - the waveguide (3) is arranged between two cladding layers (91, 92), - a cavity (10) is formed in one of the mantle layers (91, 92), and - the light source (5) is arranged inside the cavity (10). [13] The semiconductor laser chip (1) according to one of the preceding claims, wherein a reflective layer (11) is arranged on one side of the substrate (2) opposite the light source (5). [14] The semiconductor laser chip (1) according to the previous claim, wherein the reflective layer (11) comprises a metal, a Bragg mirror (111) and / or a retroreflective structure (112). [15] The semiconductor laser chip (1) according to one of the preceding claims, wherein a heating element (12) is arranged in or on the substrate (2) in the vicinity of the laser-active material (4). [16] A laser arrangement (100) comprising: at least two semiconductor laser chips (1) according to one of claims 1 to 15, wherein - the waveguides (3) of the at least two semiconductor laser chips (1) have a common substrate (2). [17] The laser arrangement (100) according to the previous claim, wherein the at least two semiconductor laser chips (1) emit electromagnetic laser radiation (6) with the same wavelength or with different wavelengths. [18] The laser arrangement (100) according to one of claims 16 or 17, wherein the at least two semiconductor laser chips (1) comprise a first semiconductor laser chip (1a) and a second semiconductor laser chip (1b) which are cascaded such that the electromagnetic laser radiation (6) emitted by the first semiconductor laser chip (1a) is used for optical pumping of the second semiconductor laser chip.

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