Optically pumped semiconductor disk laser

Abstract

Barrier-pumped semiconductor disk laser comprising a pump light source, at least one semiconductor body (2), which semiconductor body (2) has at least one window region (8), one active region (7) and one reflection device (P), wherein the active region (7) comprises at least a number of barrier layers and a number of quantum wells, wherein the barrier layers are essentially formed of GaSb or GalnAsSb or AlGaAsSb or AlGalnAsSb and the quantum wells are essentially formed of GalnSb or GalnAsSb, wherein the reflection device has at least a first P-reflection element (P1) for the pump wavelength, wherein the first P-reflection element (P1) is configured and arranged such that pump light emanating from the pump light source (3) is conductable with at least two passes through the active region (7), wherein a first band gap of the barrier layers and a second band gap of the quantum wells differ by less than 50% and wherein the total thickness of the active region (7) and the window region (8) in the direction of an optical axis of the semiconductor disk laser is less than three times the laser wavelength in the active region (7).

Description

[0001] The invention lies in the field of semiconductor lasers and relates to a semiconductor disk laser (SDL - semiconductor disk laser or VECSEL - vertical cavity surface emitting laser) according to the preamble of claim 1.

[0002] Compared to edge-emitting semiconductor lasers, semiconductor disk lasers are characterized by improved beam quality with a diffraction-limited beam and a circular intensity profile, while simultaneously achieving high output powers. The size of the pumped area allows semiconductor disk lasers to scale their power while maintaining high beam quality. This allows a wide range of complex requirements, such as tunable emission wavelengths or mode-selective laser operation, to be met while simultaneously achieving high output powers using various external resonator configurations.

[0003] As is known from the prior art, see for example M. Kuznetsov et al. “High-power diode-pumped vertical external cavity surface emitting semiconductor lasers with circular TEM00 beams”, IEEE Photonics Technology Letters, Vol. 9, No. 8, p. 1063 (1997), the semiconductor body of a semiconductor disk laser consists of three clearly separated regions: A) a mirror region that is highly reflective for one operating wavelength of the laser (laser wavelength). Optionally, this region can have additional optical properties (such as high reflectivity in a second wavelength range, see WO 02 / 47223 A1). B) an active region containing quantum wells (QWs) and adjacent barrier or spacer layers. Optionally, additional layers for specific functionalities can be located in the active region between the quantum wells and barrier layers (see, for example, J. Paajaste et al. “High-power and broadly tunable GaSb-based optically pumped VECSELs emitting near 2µm”, Journal of Crystal Growth 311, p. 1917 (2009)). The thickness of the active region is defined from the beginning of the first to the end of the last barrier layer directly adjacent to a quantum well. The thickness of the active region thus corresponds to the extent of the active region in the direction of an optical axis (parallel to the main emission direction, preferably parallel to the growth direction of the semiconductor layers, i.e. normal to the wafer surface) of the semiconductor disk laser.Within the active region of a semiconductor disk laser, pump radiation is absorbed and laser radiation is generated. If the energy of the pump photons is above the band gap of the quantum wells and below the band gap of the barrier layers surrounding the quantum wells, the pump light is absorbed only in the quantum wells. These are then referred to as "in-well" pumped semiconductor disk lasers. If the energy of the pump photons is above the band gap of the barrier layers surrounding the quantum wells, the pump light is absorbed in both the barrier and quantum well layers. Due to the layer thickness ratios of the barrier layers to the quantum wells, the majority of the pump light is absorbed in the barrier layers, which is why this configuration is referred to as a "barrier-pumped" semiconductor disk laser. C) a window region through which the laser radiation exits the structure and which simultaneously shields the active region from the environment as a surface. The window region is constructed from semiconductor layers that are transparent to the laser wavelength (i.e. absorption is minimal). If an optical pumping process with pump photons of a pump wavelength occurs through the window region, the window region must also be transparent to the pump wavelength. Typically, the semiconductor layers in the window region have a larger band gap than the last barrier layer of the active region in order to prevent diffusion of charge carriers to the surface, for example in barrier-pumped semiconductor disk lasers. Furthermore, the window region can be constructed in such a way that it changes the reflectivity for the laser wavelength and / or the pump wavelength (e.g. AR for the laser wavelength in WO 02 / 47223 A1).In many designs, the window region is sealed by a thin cap layer at the air interface. This cap layer serves to prevent any oxidation of the underlying semiconductor material. The thickness of the window region is defined by the adjacent active region and the end of the semiconductor body, i.e., the surface at the interface between the semiconductor body and the environment. The thickness of the window region thus corresponds to the extent of the window region in the direction of an optical axis (parallel to the main emission direction) of the semiconductor disk laser.

[0004] The total thickness of the active region and the window region thus corresponds to the extension of the active region and the window region in the direction of an optical axis (parallel to the main emission direction) of the semiconductor disk laser.

[0005] It is also known to adjust the length of the semiconductor structure in such a way that a resonance for the laser light is formed within the semiconductor structure, thus creating a standing wave field for a laser field intensity, in order to increase the absorption of the pump light. Typically, absorption efficiencies of the pump light in the range of 65-95% are desired. For example, WO 02 / 47223 discloses directing the pump light a second time through the active region to increase the absorption efficiency.

[0006] An alternative semiconductor arrangement for an optically pumped surface-emitting semiconductor laser is disclosed in DE102006002879A1. This document discloses a semiconductor arrangement comprising a semiconductor body with multiple groups of quantum wells arranged such that the groups of quantum wells have different numbers of quantum wells and the arrangement is optimized with respect to maxima of the path of the pump light and the laser light in the semiconductor arrangement. This measure can optimize the semiconductor arrangement such that comparable charge carrier densities are generated in each of the quantum wells, even with an uneven distribution of the pump field.

[0007] In the publication “Thermal Management for High-Power Single-Frequency Tunable Diode-Pumped VECSEL Emitting in the Near- and Mid-IR”; Devautour et al. IEEE Journal of Selected Topics in Quantum Electronics, Vol. 19, No. 4, July / August 2013, a semiconductor laser device based on GaSb and GaAs based III-V semiconductor materials with improved thermal management is disclosed by reducing the length of the active region and the number of layers of the Bragg mirror for the laser wavelength.

[0008] A disadvantage of state-of-the-art semiconductor disk lasers is that their maximum output power, especially in the MIR wavelength range between 1.9 and 2.8 µm, is limited compared to other laser concepts. Likewise, the scalability of the output power via the size of the pumped area is currently limited.

[0009] The present invention is therefore based on the object of providing a semiconductor disk laser which enables an increase in output power and has improved scalability of the output power, in particular in the MIR wavelength range.

[0010] This object is achieved by a semiconductor disk laser according to claim 1. Preferred embodiments of the semiconductor disk laser according to the invention can be found in claims 2 to 13. The wording of the claims is hereby explicitly incorporated into the description by reference.

[0011] The invention is based on the applicant's finding that high power efficiency and high output power can be achieved in semiconductor disk lasers by passing the pump light through the active region at least a second time and forming the semiconductor structure with a reduced overall thickness of the active region and the window region.

[0012] Surprisingly, the applicant's investigations have shown that, unlike the prior art, a greater overall thickness of the semiconductor structure does not lead to higher power and power efficiency, but rather that higher output power is achieved precisely with a reduced overall thickness of the active region and the window region.

[0013] The semiconductor disk laser according to the invention is designed as an optically pumped semiconductor disk laser and comprises a pump light source, at least one semiconductor body with an active region, a window region and a reflection device, which reflection device has a first P-reflection element for the pump wavelength, wherein the first P-reflection element is designed and arranged such that the pump light emanating from the pump light source can be guided through the active region in at least two passes.

[0014] It is essential that the total thickness of the active region and the window region in the direction of an optical axis of the semiconductor disk laser is less than three times the laser wavelength in this medium.

[0015] Typically, the thickness of the active region and / or the total thickness of the active region together with the window region is specified as a multiple of the laser wavelength λ in the medium, ie, in the material system in question. According to the invention, the total thickness of the active region and the window region L gesamt < 3. λ. The conversion into real layer thicknesses can be done using the emission wavelength of the laser in air λ L and the refractive indices of the individual layers n, where: λ = λ L / n.

[0016] The semiconductor body is preferably constructed as a semiconductor layer structure. However, it is also within the scope of the invention for layers and / or components that are not formed in a semiconductor material to be included within the semiconductor body. The thickness of the window region is defined by the adjacent active region and by the end of the semiconductor body, i.e., the surface as the interface between the semiconductor body and the environment. Any additional coatings adjacent to the window region of the semiconductor body that are not formed in a semiconductor material do not belong to the window region and thus do not change the inventive thickness of the window region.

[0017] The reduced overall thickness of the active region including the adjacent window area results in the following advantages with regard to the laser properties of the semiconductor disk laser: - The internal optical losses are reduced because the absorption of free charge carriers in the active region decreases due to the reduced overall thickness. - The internal efficiency increases because non-radiative recombination of charge carriers in the active region is reduced due to the reduced overall thickness. - The shortened active area leads to improved heat dissipation because the distance to a heat spreader (typically located on the top or bottom of the structure) is shortened. - For a given size of the optical pump spot, the reduced overall thickness leads to a heat flow that is more like a purely one-dimensional heat flow, compared to the significantly stronger influence of the three-dimensional heat flow with a longer active region. This improves the scalability of the output power of the semiconductor disk laser across the size of the pumped area, since the one-dimensional heat flow significantly improves scalability.

[0018] However, these advantages of a thinner structure only lead to higher output power if the pump light is simultaneously passed through the active region at least once more. Only in this way can the disadvantage of a thinner structure—the lower absorption efficiency of the pump light due to the shorter absorption path length—be offset. High pump light absorption is essential for achieving high power efficiency.

[0019] In a preferred embodiment, the barrier layers and / or the quantum wells within the active region are constructed from semiconductor material from the III-V compound semiconductor group. This offers the advantage that the wavelength can be adjusted over a wide range by selecting a suitable composition of the semiconductor layers.

[0020] According to the invention, the semiconductor layers are essentially made of the III-antimonide material system, meaning that the quantum wells and barriers are made of GaSb, GaInSb, GaInAsSb, AlGaAsSb, or AlAsSb. This results in the advantage that laser emission can be achieved in the wavelength range around 2 µm and beyond.

[0021] According to the invention, the semiconductor disk laser is designed as a barrier-pumped semiconductor disk laser, meaning that the pump light is primarily absorbed in the barrier layers adjacent to the quantum wells. In barrier-pumped semiconductor disk lasers, reducing the thickness of the active region along with the window region increases the percentage of pump light absorbed directly in the quantum wells. This reduces absorption in the barrier layers for the same number of quantum wells, thus reducing the significance of recombination losses in the barrier layers.

[0022] In a further preferred embodiment, the first P-reflection element of the reflection device is designed as a mirror, in particular as a multilayer mirror, preferably as a double-band dielectric mirror (distributed Bragg reflector). Particularly preferably, the first P-reflection element is designed such that it has a high reflectivity for the pump wavelength, preferably for both the pump wavelength and the laser wavelength, in particular higher than 95%, preferably higher than 97%. The double-band dielectric mirror can be applied to the semiconductor layers by subsequent coating or can preferably be formed using an epitaxial growth process. The advantage here is that the high reflectivity of the double-band dielectric mirror for the pump wavelength enables a double passage of the pump light through the active region.The pump light travels from the pump light source into the active region, is reflected by the double-band dielectric mirror in the active region, and then passes through the active region in a second pass. Alternatively, broadband reflecting layers (e.g., metallic coatings) or a combination of the described options can be used.

[0023] In a further preferred embodiment, the semiconductor disk laser comprises a second P-reflection element for the pump wavelength, wherein the active region is arranged between the first P-reflection element and the second P-reflection element, and the first P-reflection element, active region, and second P-reflection element are designed and arranged to cooperate in such a way that, in the operating state, the pump light undergoes multiple passes through the active region. The second P-reflection element is preferably formed by a semiconductor-air interface of the semiconductor body facing away from the first P-reflection element. Due to the different refractive indices of air and semiconductor material, said interface acts as a mirror. Advantageously, no additional optical component is required to fulfill the resonance condition.Alternatively, an additional coating or a Bragg mirror is applied to the top of the semiconductor body.

[0024] Preferably, the first P-reflection element, active region, and second P-reflection element are designed and arranged in such a way that a resonance for the pump wavelength is formed. The pump light is reflected, and the reflected, returning wave overlaps with the incoming wave of the pump light. If the resonance condition is met, a standing wave for the pump light (also called microcavity resonance for the pump wavelength) is formed. This resonance significantly increases the absorption of the pump radiation and thus the power efficiency of the semiconductor disk laser.

[0025] In a further preferred embodiment, the layer thicknesses of the semiconductor body are adjusted such that a resonance for the laser wavelength is formed within the active region. It is also advantageous to place the quantum wells in the antinodes of the resulting standing wave field of the laser wavelength. This design (also called "resonant periodic gain", RPG) increases the modal gain of the structure and thus reduces the laser threshold. The advantage of this structure is that the intensity of the laser light at the location of the quantum wells and thus the modal gain of the structure can be increased (see, for example, SW Corzine et al. "Design of Fabry-Perot surface-emitting lasers with a periodic gain structure", IEEE Journal of quantum electronics, vol. 25, p. 1513 (1989)).

[0026] In a further preferred embodiment, a transparent heat spreader (e.g. made of diamond or silicon carbide, SiC) is applied to the semiconductor body in order to improve heat dissipation. The advantage here is that the shorter distance to the surface of the semiconductor body and thus to the heat spreader and to the first reflection element leads to a lower thermal resistance due to the shortened length of the active region. The low thermal resistance improves heat dissipation. Therefore, pump light sources with higher pump light intensities can be used compared to the prior art, and thus an increased output power can be achieved. The heat spreader is preferably designed as an intracavity heat spreader, i.e. the intracavity heat spreader is applied on the side of the semiconductor body within the laser resonator facing away from the first P-reflection element.Preferably, a second heat spreader is arranged on the side of the semiconductor body facing away from the first heat spreader. For this purpose, it is advantageous to partially or completely remove the substrate on which the semiconductor body was grown in order to further improve heat dissipation.

[0027] In a further preferred embodiment, the total thickness of the active region together with the adjacent window region is further reduced, preferably formed with a thickness < 2.5·λ, most preferably < 2·λ, preferably < 1.5·λ, particularly preferably < 1·λ, preferably < 0.5·λ.

[0028] In a further preferred embodiment, a quantum deficit, i.e. an energetic difference between pump and laser photons, is less than 50%, preferably less than 40%, preferably less than 30%, preferably less than 20%.

[0029] According to the invention, the active region comprises at least a number of barrier layers and a number of quantum wells, wherein a first band gap of the barrier layers and a second band gap of the quantum wells differ by less than 50%. The small difference between the first band gap of the barrier layers and the second band gap of the quantum wells allows the quantum deficit of the barrier-pumped semiconductor disk laser to be reduced. The low-energy pump photons enable a lower quantum deficit. This increases the external power efficiency of the semiconductor disk laser. Advantages here include the lower laser threshold and the increased output power.

[0030] In a further preferred embodiment, the barrier layers in the active region are formed essentially of GaSb or GaInAsSb, and the quantum wells are formed essentially of GaInSb or GaInAsSb. When using this material system, the barrier layers exhibit a smaller band gap than alternative material systems such as AlGaAsSb. This allows the use of a pump laser adapted to the barrier material, such as a laser with a higher emission wavelength in the range of 1.5 µm. With the same emission wavelength of the quantum wells, the quantum deficit is reduced, allowing higher pump powers to be used.

[0031] In a further preferred embodiment, the total thickness of the active region and window region is less than 1 / 200 of the diameter of the pump beam on the surface of the semiconductor body. The total thickness of the active region and window region is thus much smaller than the diameter of the pumped region, which essentially corresponds to the diameter of the light beam from the pump light source. Advantageously, the heat flow from the active region to a heat sink, e.g., preferably via an intracavity heat spreader or a heat spreader under the dielectric mirror, is approximated to a purely one-dimensional heat flow. This improves the scalability of the output power of the semiconductor disk laser across the size of the pumped area.Preferably, the total thickness of the active region and the window region is less than 1 / 300 of the diameter of the pump beam on the surface of the semiconductor body, most preferably less than 1 / 400 of the diameter of the pump beam on the surface of the semiconductor body, particularly preferably less than 1 / 500 of the diameter of the pump beam on the surface of the semiconductor body.

[0032] In a further preferred embodiment, the absorption efficiency of the pump light is greater than 70%, preferably >90%, preferably >95%.

[0033] In a further preferred embodiment, the semiconductor disk laser is designed such that the pump light impinges on the active region at an angle of incidence with respect to the optical axis, which angle of incidence corresponds to an optimal spectral resonance for the pump wavelength. Particularly preferably, the angle of incidence for the pump light is optimized as a function of the temperature and the semiconductor layer structure. This means that an optimal spectral position of the resonance for the pump wavelength is set by means of an angle of incidence of the pump light and / or the temperature of the semiconductor layer. "Optimal spectral resonance" here means that the resonance for the pump wavelength reaches a maximum, in particular a global maximum, as a function of the angle of incidence.The maximum here is the point at which the resonance, after an initial increase, transitions to a decrease depending on the angle of incidence of the pump light and the temperature of the semiconductor layer structure. This results in the advantage of almost complete absorption of the pump light despite the shortened length of the active region.

[0034] In a further preferred embodiment, the barrier-pumped semiconductor disk laser has an active region with a length L akt [m], where Lact=−In(1−ηabs) / (2α(λ)⋅Γabs(λ)) with the absorption efficiency of the pump photons in the active region η abs [%], the average absorption coefficient of the active region α(λ)[m -1 ] and Γ abs (λ) [-] as an increase factor for the absorption of the pump light by the resonance.

[0035] This results in particular in the advantages that the length of the active region L akt can be significantly shortened, while preferably the required length of the absorption path S abs within the active region for a given value of the pump light absorption efficiency η abs remains essentially the same.

[0036] The length of the active region in this description is the length of the path along the optical axis of the semiconductor disk laser, which runs in the active region of the semiconductor layer structure, denoted by L akt ,.

[0037] The required length of the absorption section S abs Within the active region, in the context of this description, is the length that the pump light travels in the active region. The length S absis determined with the material-specific absorption coefficient α(λ)[m -1 ] of the pump photons in the active region is determined by a given value of the absorption efficiency η abs should be achieved: sabs=−In(1−ηabs) / α(λ)

[0038] Further preferred features and embodiments of the semiconductor disk laser according to the invention are explained below with reference to exemplary embodiments and the figures. Herein: Fig. 1 a schematic representation of a first embodiment of a semiconductor wafer laser according to the invention with a linear resonator, Fig. 2 a schematic representation of a previously known semiconductor device (state of the art), Fig. 3 the course of the refractive index and the intensity distribution of the laser field in a previously known semiconductor device (state of the art), Fig. 4 a schematic representation of a first embodiment of a semiconductor body showing the double passage of the pump light through the active region Fig. 5 shows the course of the refractive index and the intensity distribution of the laser field in an exemplary embodiment of the semiconductor body according to the invention, Fig. 6 a schematic representation of a further embodiment of a semiconductor body with a multiple passage of the pump light through the active region. Fig. 7 the course of the refractive index and the intensity distribution of the laser field and the pump light field in a preferred embodiment according to Fig. 6.

[0039] In the Fig. 1 to 7, the same reference symbols denote the same or equivalent elements.

[0040] Fig. Figure 1 schematically shows the basic structure of a first embodiment of a semiconductor disk laser with a linear laser resonator 1. The semiconductor disk laser has a semiconductor body 2, a pump light source 3, in this case a laser, a pump optics 4, and an external mirror 5. The laser radiation 13 emitted by the pump light source 3 passes through the pump optics 4 and is focused in the semiconductor body 2. The laser resonator 1 is formed by a mirror, which is part of the semiconductor body 2, and the external mirror 5. The laser resonator 1 can also be designed as an arrangement with several external mirrors or other optical elements. The semiconductor body 2 is optically pumped via the pump laser 3 and the pump optics 4. A pump spot diameter can vary greatly depending on the pump laser 3, e.g., between 50 µm and 2000 µm. In the present case, the pump spot diameter is approximately 550 µm.The laser resonator 1 for the laser wavelength has an extension along the optical axis of typically a few cm in length, but significantly shorter (in the range of 100 µm in length) or significantly longer (a few 10 to 100 cm in length) resonators can also be realized.

[0041] Fig. 2 shows the basic structure of the semiconductor body 2. This comprises a mirror region 6 which is highly reflective for the laser wavelength. Adjacent to this is the active region 7. In the active region 7, the pump radiation is absorbed and the laser radiation is generated. Arranged on the active region is the window region 8, which forms the uppermost region of the semiconductor structure. The mirror 6 is made of semiconductor material in the form of a distributed Bragg reflector (DBR), in this case from III-V semiconductor material, but can also be in the form of a dielectrically vapor-deposited or metallic mirror, or from a combination of these possibilities. The window region 8 is made of III-V semiconductor material in this case.

[0042] In Fig. Figure 3 shows an example of the profile of the refractive index n 9 and the intensity distribution of the laser field 10 in a previously known semiconductor arrangement (prior art). Identified are the mirror region 6 (of which only the first layer pairs are visible) and the active region 7 with the barrier layers 11 and quantum wells 12. In this example, the active region 7 has a thickness of 6 λ / 2 = 3λ, where λ is the laser wavelength in the respective material system. The semiconductor structure is closed off by the window region 8, which in this example consists of a material with a high band gap (and thus a lower refractive index) and a thin cap layer, and has a total thickness of 2 λ / 2. The thicknesses of the semiconductor layers in this example are adapted such that a resonance for the laser light is formed within the semiconductor structure, thus creating a standing wave field for the laser field intensity.Furthermore, the quantum wells are arranged in the wave streams (RPG design). The total thickness of the active region 7 together with the adjacent window region 8 (or, in other words, the thickness of the entire semiconductor structure 2, excluding the mirror region 6) is 8 λ / 2 = 4 λ.

[0043] Fig. 4 shows a schematic representation of a first embodiment of a semiconductor arrangement with representation of the pump light. The semiconductor body 2 has the reduced total thickness of the window region and the active region according to the invention: the thickness of the active region 7 together with the thickness of the window region 8 (or in other words, the thickness of the entire semiconductor structure 2, excluding the mirror region 6) is less than 3λ in absolute value, where λ is the laser wavelength in the relevant material system. The semiconductor body 2 is designed such that the pump light is guided through the active region 7 at least a second time with the aid of the reflection device P. The reflection device P comprises the first P-reflection element, which is designed as a mirror 6. The mirror 6 has a high reflectivity for both the laser light and the pump light 13.The pump light 13 is therefore passed through the active region 7 at least a second time.

[0044] In Fig. 5 is the profile of the refractive index n 9 and the intensity distribution of the laser field 10 in an embodiment of the arrangement according to Fig. 4. The mirror region 6 (in which again only the first layers are shown) is designed in this case such that it has a high reflectivity for both the laser light and the pump light. As a result, the pump light is guided through the active region 7 at least a second time. The active region 7 with the barrier layers 11 and quantum wells 12 has a thickness of 4 λ / 2, and the adjacent window layer (including a cap layer contained in the window layer 8) has a thickness of λ / 2. The thickness of the active region 7 together with the thickness of the window region 8 (or in other words, the thickness of the entire semiconductor structure 2, excluding the mirror region 6) is thus 5 λ / 2 and is less than 3 λ.

[0045] For an emission wavelength λ LWith a thickness of 2.0 µm, this structure can consist, for example, of a 260 nm thick window layer (8) (consisting, for example, of 10 nm GaSb and 250 nm AlGaAsSb with a refractive index n of 3.89 and 3.24, respectively) and a 1070 nm thick active region (7), which in turn consists of GaSb (n=3.89) and GaInSb quantum wells (n=4.0). The mirror region consists of several layers of AlAsSb and AlGaAsSb.

[0046] Fig. Figure 6 shows a schematic representation of another embodiment of a semiconductor device. Here, the mirror 6 is designed such that it has a high reflectivity for both the laser light and the pump light 13 and thus, as shown in Fig. 4 represents a P-reflection element P for the pump light. Furthermore, the window region 8 is designed such that it represents a further P-reflection element P2 for the pump light, e.g. by reflecting the pump light at the semiconductor-air interface on the surface of the window layer 8. This results in multiple passages of the pump light 13 through the active region 7. The thicknesses of the semiconductor layers in the active region 7 and the window layer 8 are adapted such that resonance of the pump light occurs. The resonance further increases the intensity of the pump light (as in an etalon) in the active region 7. The thickness of the active region 7 together with the thickness of the window region 8 (or in other words the thickness of the entire semiconductor structure 2, excluding the mirror region 6) is less than 3 λ, where λ is the laser wavelength in the relevant material system.

[0047] In Fig. 7 is the profile of the refractive index 9 and the intensity distribution of the laser field 10 in the above-mentioned preferred embodiment according to Fig.6. Due to the dual-band mirror 6 (high reflection for laser and pump light), the reflection of the pump light at the semiconductor-air interface at the end of the window layer 8, and the adapted layer thicknesses in the active region 7 and the window region 8, a standing wave field (resonance) is formed not only for the laser light 10, but also for the pump light 13. As a result, the pump light 13 is guided through the active region 7 many times. The active region 7 with the barrier layers 11 and quantum wells 12 has a thickness of 3 λ / 2, and the adjacent window region (including the cap layer) has a thickness of λ / 2. The thickness of the active region 7 together with the thickness of the window region 8 (or in other words, the thickness of the entire semiconductor structure 2, excluding the mirror region 6) is thus 4 λ / 2 and is less than 3 λ.

Claims

[1] Barrier-pumped semiconductor disk laser comprising a pump light source, at least one semiconductor body (2), which semiconductor body (2) has at least one window region (8), an active region (7) and a reflection device (P), wherein the active region (7) comprises at least a number of barrier layers and a number of quantum wells, wherein the barrier layers are formed essentially from GaSb or GaInAsSb or AlGaAsSb or AlGaInAsSb and the quantum wells are formed essentially from GaInSb or GaInAsSb, wherein the reflection device has at least a first P-reflection element (P1) for the pump wavelength, wherein the first P-reflection element (P1) is designed and arranged such that pump light emanating from the pump light source (3) can be guided through the active region (7) with at least two passages, wherein a first band gap of the barrier layers and a second band gap of the quantum wells differ by less than 50% and wherein the total thickness of the active region (7) and the window region (8) in the direction of an optical axis of the semiconductor disk laser is less than three times the laser wavelength in the active region (7). [2] Barrier-pumped semiconductor disk laser according to the preceding claim, characterized bythat the reflection device (P) of the semiconductor body (2) is designed as a first P-reflection element (P1) for the pump wavelength as a double-band dielectric mirror (6) (distributed Bragg reflector), particularly preferably that the reflection region for the pump wavelength and for the laser wavelength has a reflectivity > 95% and / or that the first P-reflection element (P1) for the pump light is designed as a dielectric or metallic mirror (6) or as a combination of a dielectric mirror and a metallic mirror or as a combination of a dielectric mirror, a metallic mirror and a double-band dielectric mirror. [3] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized bythat the semiconductor disk laser comprises a second P-reflection element (P2) for the pump wavelength, which second P-reflection element (P2) is arranged on the side of the active region (7) facing away from the first P-reflection element (P1), and that the first P-reflection element (P1), active region (7) and second P-reflection element (P2) are designed and arranged to cooperate in such a way that, in the operating state in the active region (7), the pump light passes through the active region (7) multiple times. [4] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized by that the thickness of the semiconductor body (2) and the first P-reflection element (P1) and the second P-reflection element (P2) are designed and arranged to cooperate in such a way that a resonance for the pump light results. [5] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized bythat the thickness of the active region (7) and the window region (8) in the direction of an optical axis of the semiconductor disk laser is less than 2.5 times the laser wavelength in this medium (< 2.

5. λ), most preferably less than 2 times the laser wavelength in this medium, preferably less than 1.5 times the laser wavelength in this medium, particularly preferably less than 1 times the laser wavelength in this medium, preferably less than 0.5 times the laser wavelength in this medium. [6] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized by that the second P-reflection element (P2) is formed by a semiconductor-air interface of the semiconductor body (2) facing away from the first P-reflection element (P1), preferably by said semiconductor-air interface of the semiconductor body (2), which comprises an optical coating. [7] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized by that a first band gap of the barrier layers and a second band gap of the quantum wells differ by less than 40%, most preferably by less than 30%. [8] Optically pumped semiconductor disk laser according to one of the preceding claims, characterized by that the semiconductor body (2) is designed such that a resonance for the laser light is produced and the quantum wells in the active region (7) are arranged according to the resonant periodic gain concept. [9] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized bythat the cooling of the semiconductor body (2) takes place via the reflection device (P), preferably via the first P-reflection element (P1), preferably that the cooling of the semiconductor body (2) takes place by means of a heat spreader, most preferably by means of a SiC or diamond heat spreader, in particular that the heat spreader is arranged on the side of the active region (7) facing away from the first reflection element (P1). [10] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized by that a semiconductor material from the group of III-V compound semiconductors is used as the material for the barrier layers and / or the quantum wells. [11] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized bythat the semiconductor disk laser is designed such that the pump light impinges on the active region (7) at an angle of incidence which corresponds to an optimal spectral resonance for at least the pump wavelength, in particular depending on the temperature of the semiconductor body (2). [12] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized by that the total thickness of the active region (7) and the window region (8) is less than 1 / 200 of the diameter of the pump beam on the surface of the semiconductor body (2), preferably less than 1 / 300 of the diameter of the pump beam on the surface of the semiconductor body (2), most preferably less than 1 / 400 of the diameter of the pump beam on the surface of the semiconductor body (2), particularly preferably less than 1 / 500 of the diameter of the pump beam on the surface of the semiconductor body (2). [13] Barrier-pumped semiconductor disk laser according to one of the preceding claims, characterized by that the absorption efficiency of the pump light is greater than 70%, in particular greater than 90%.

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