EP2425507A1

EP2425507A1 - Edge-emitting semiconductor laser

Info

Publication number: EP2425507A1
Application number: EP10714321A
Authority: EP
Inventors: Marc Schillgalies; Stephan Lutgen; Uwe Strauss
Original assignee: Osram Opto Semiconductors GmbH
Current assignee: Ams Osram International GmbH
Priority date: 2009-04-30
Filing date: 2010-04-22
Publication date: 2012-03-07
Also published as: WO2010124989A1; CN102414944A; US20120051380A1; CN102414944B; US8331411B2; DE102009019516A1

Abstract

The invention relates to an edge-emitting semiconductor laser comprising a semiconductor body (10), which comprises a waveguide region (4), wherein the waveguide region (4) comprises a first waveguide layer (2a), a second waveguide layer (2b), and an active layer (3) arranged between the first waveguide layer (2a) and the second waveguide layer (2b) for producing laser radiation (5), and the waveguide region (4) is arranged between a first cover layer (1a) and a second cover layer (1b) following the waveguide region (4) in the growth direction of the semiconductor body (10). The waveguide region (4) has a thickness (d) of 400 nm or less, and an emission angle of the laser radiation (5) leaving the semiconductor body (10) in a direction parallel to the layer plane of the active layer (3) and the emission angle of the laser radiation (5) leaving the semiconductor body (10) in a direction perpendicular to the layer plane of the active layer (3) differ by less than a factor of 3.

Description

Edge-emitting semiconductor laser

The invention relates to an edge-emitting semiconductor laser, in particular a semiconductor laser based on a nitride compound semiconductor.

This patent application claims the priority of German Patent Application 10 2009 019 516.5, the disclosure of which is hereby incorporated by reference.

Conventional nitride compound semiconductor based semiconductor lasers are typically optimized to achieve high output powers. Therefore, such semiconductor lasers have a high slope characteristic, that is, the output power of the semiconductor laser increases sharply with increasing operating current. Since even small changes in the operating current lead to significant changes in output power, the exact control of a desired output power, in particular a small output power, problematic. Furthermore, the operation of such a semiconductor laser in an operating current range which is only slightly above the laser threshold, difficult. This is based on the fact that with constant operating current already a small, for example age-related increase of the threshold current intensity of the

Semiconductor laser can cause the threshold current is no longer reached and therefore the semiconductor laser no longer emits coherent laser radiation.

Edge-emitting semiconductor lasers that focus on a high

Efficiency are optimized at high optical powers, usually have comparatively wide waveguide structures, resulting in a comparatively small Radiation angle parallel to the layer plane of the epitaxial layers. On the other hand, such a semiconductor laser in a direction perpendicular to the epitaxial layers typically has a comparatively large radiation angle due to diffraction. The laser beam is therefore highly elliptical, so that a complex and expensive optics is usually required when the application of the edge-emitting semiconductor laser requires an approximately circular beam profile.

The invention has for its object to provide an improved edge-emitting semiconductor laser, in which a beam profile with low ellipticity, preferably a nearly circular beam profile is achieved in a comparatively simple manner.

This object is achieved by an edge-emitting semiconductor laser having the features of claim 1. Advantageous embodiments and modifications of the invention are the subject of the dependent claims.

In accordance with at least one embodiment, an edge-emitting semiconductor laser has a semiconductor body with a waveguide region, the waveguide region having a first waveguide layer, a second waveguide layer and an active layer for generating laser radiation arranged between the first waveguide layer and the second waveguide layer. The waveguide region is between a first cladding layer, which faces, for example, a substrate of the edge-emitting semiconductor laser, and a second cladding layer, for example, the waveguide region in the growth direction of Semiconductor body follows, arranged. In the growth direction of the semiconductor body, therefore, preferably the first cladding layer, the first waveguide layer, the active layer, the second waveguide layer and the second cladding layer follow one another. The preferably epitaxially produced semiconductor layers are for example applied to a substrate and can be provided on an opposite side of the substrate with an electrical contact layer.

The waveguide region preferably has a thickness of 400 nm or less. That is, the sum of the thicknesses of the first waveguide layer, the second waveguide layer, and the active layer disposed between the first waveguide layer and the second waveguide layer is not more than 400 nm.

Because the waveguide region is comparatively thin and preferably has a thickness of less than 400 nm, it is achieved that the difference in the

Beam angle in the horizontal direction, d. H. in a direction parallel to the layer plane of the semiconductor layers and in the vertical direction, d. H. is reduced in a direction perpendicular to the layer planes of the semiconductor layers, compared to conventional edge emitting semiconductor lasers. The astigmatism typical of edge emitting semiconductor lasers, d. H. a highly elliptical beam profile is reduced in this way.

Preferably, the waveguide region has a thickness of 300 nm or less, more preferably even 250 nm or less. In a preferred embodiment, the emission angle α _{P of} the laser radiation emerging from the semiconductor body in a direction parallel to the layer plane of the active layer and the emission angle α _{s of} the laser radiation emerging from the semiconductor body in a direction perpendicular to the layer plane of the active layer differ by less than a factor 3 from each other. In the context of the application, the emission angles α _s , αp are each understood to mean the full angular range in which the intensity of the emitted laser radiation is not less than half the intensity in the main radiation direction (FWHM-filling width at half maximum). Furthermore, the emission angle at the side facet of the semiconductor laser without taking into account any existing optical elements for beam shaping, in particular lenses arranged outside the semiconductor body, is understood as the emission angle of the laser radiation emerging from the semiconductor body.

In particular, it is possible that the radiation angles of the semiconductor laser in the horizontal and vertical directions differ by less than a factor of two. For example, the emission angle in the vertical direction, that is to say perpendicular to the layer planes of the semiconductor layers, can be greater than the emission angle in the horizontal direction, that is, in a direction parallel to the layer planes of the semiconductor layers. However, the emission angle in the vertical direction is at most three times and preferably not more than twice as large as the emission angle in the horizontal direction.

Because the emission angles have only a comparatively small difference in the horizontal and vertical directions, it is possible to achieve a comparatively small difference to use inexpensive spherical lens for collimating the laser radiation. On comparatively expensive aspherical lenses, such as cylindrical lenses, can be advantageously dispensed with.

In particular, the edge-emitting semiconductor laser can have a housing which contains a lens for beam shaping of the emitted laser radiation. The preferably spherical lens advantageously serves as a cover of the housing and advantageously protects the semiconductor body of the edge-emitting semiconductor laser from mechanical damage or environmental influences such as moisture or dirt.

The housing of the edge-emitting semiconductor laser can be designed in particular as a so-called TO package (transistor outline). This type of housing usually has several, typically three, connection legs for electrical contacting and mounting of the edge-emitting semiconductor laser. The semiconductor body of the edge-emitting semiconductor laser is arranged under a cover, which may in particular be cylindrical, on an electrically conductive support which is connected to one of the connecting legs. The typically at least approximately cylindrical cover may for example be made of plastic or metal and have on the radiation exit side a transparent cover, which is preferably designed as a lens, particularly preferably as a spherical lens.

Alternatively, the semiconductor laser can also have an SMT housing (surface mount technology). Such surface-mountable housing have at one Housing bottom and / or a housing side surface contact surfaces for electrical contacting, where the housing can be soldered for example on a circuit board.

The edge-emitting semiconductor laser has a first and a second side facet, which are preferably each provided with a reflection-enhancing coating. In a preferred embodiment, a first side facet of the semiconductor body serving as a radiation coupling-out surface is provided with a reflection-enhancing coating whose reflection is preferably 75 percent or more. Particularly preferably, the reflection of the reflection-increasing coating on the first side facet serving as the radiation coupling-out surface is even 85 percent or more. It is also possible that the reflection of the reflection-enhancing coating is as high as 95 percent or more.

By such a high reflection on the as

Although the facet of the semiconductor body serving for radiation coupling-out area reduces the steepness of the characteristic line of the semiconductor laser, ie the output power of the semiconductor laser increases less with increasing operating current than in a conventional semiconductor laser, in which the radiation output surface has a lower reflection. This is based on the fact that a larger proportion of the laser radiation incident on the side facet of the semiconductor body is reflected back into the resonator and thus is not coupled out of the semiconductor laser. On the other hand, in this way, the mean circulation time of the laser radiation increases in the Laser resonator, which advantageously reduces the threshold current of the semiconductor laser.

The low threshold current intensity and the low steepness of the characteristic curve of the semiconductor laser have the advantage that a stable operation is ensured even at low output powers of the semiconductor laser. In particular, smaller changes in the operating current effect only small changes in the optical output power, and the risk of dropping below the threshold current intensity with fluctuations in the operating current is relatively low due to the low threshold current. In particular, the operating currents in normal operation are so far above the threshold current of the semiconductor laser, that a possibly occurring age-related increase in

Schwellstromstärke usually does not cause the laser threshold is not reached and it comes to a suspension of the laser action.

In a further preferred embodiment, one of the radiation coupling-out surface opposite the second side facet of the semiconductor laser is followed by a monitor diode. The second side facet, which lies opposite the first side facet serving as radiation coupling-out surface, typically has a comparatively high reflection of preferably 85 percent or more, or particularly preferably 95 percent or more. Nevertheless, at least a small proportion of the laser radiation can emerge from the semiconductor body at the side facet opposite the radiation coupling-out surface and be supplied to a monitor diode for monitoring the optical output power of the semiconductor laser. The monitor diode is preferably connected to a control loop, via which the optical output power is kept constant.

The increase in the reflection of the first side facet serving as the radiation decoupling surface has the aforementioned

Advantages of reducing the threshold current and decreasing the slope of the characteristic of the

Semiconductor laser. Furthermore, it is also advantageously possible to reduce the resonator length compared to a conventional semiconductor laser. In particular, it has been found that a shortening of the length of the laser resonator from a length L _a to a length L _{b can} be compensated for by increasing the reflectivity of the first side facet Ri, _a serving as radiation coupling-out surface to a value Ri, _b . The compensation of the reduced resonator length by an increased reflection Ri, _{b of} the first side facet is carried out according to the following equation:

In this case, R2, _{a is} the reflection of the second side facet which lies opposite the first side facet serving as the radiation coupling-out surface.

The shortening of the resonator of the edge-emitting semiconductor laser has the advantage that a larger number of laser diodes can be produced on a wafer, which advantageously reduces the production costs, Advantageously, the length of the laser resonator of the edge-emitting semiconductor laser is not more than 450 μm.

Due to the comparatively low threshold current intensity and the low steepness of the characteristic curve, the edge-emitting semiconductor laser is particularly suitable for operation at low output powers. Preferably, the optical output power is 10 mW or less. In particular, stable operation can be realized even at output powers of 5 mW or less.

The edge-emitting semiconductor laser is therefore of particular importance for applications in which a stable operation with low output powers is to be achieved in a cost-effective manner, for example in the case of a laser pointer.

The edge-emitting semiconductor laser may, in particular, be a semiconductor laser which emits laser radiation in the wavelength range from 430 nm to 700 nm.

Preferably, the semiconductor laser emits in the blue or blue-green region of the visible spectrum. In particular, the emitted laser radiation may have an intensity maximum at a wavelength between 430 nm and 540 nm. The semiconductor laser can for example be part of a

Laser pointers with a wavelength in the blue spectral range (<500 nm) or with a wavelength in the green spectral range (> 500 nm), be.

Such a semiconductor laser may for example be based on a nitride compound semiconductor. "Based on a nitride compound semiconductor" in the present context means that the semiconductor layer sequence or at least one layer thereof comprises a III-nitride compound semiconductor material, preferably In _x Al _y Ga _x - _y N, where O ≤ x ≤ l, O ≤ y ≤ l and x + y ≤ 1 must This material does not necessarily have a mathematically exact composition according to the above formula. Rather, it may have one or more dopants such as Mg or Si and additional constituents comprise, that do not alter the characteristic physical properties of the In _x Al _y Ga _x -YN material substantially. For the sake of simplicity, however, the above formula contains only the essential constituents of the crystal lattice (In, Al, Ga, N), even if these may be partially replaced by small amounts of other substances.

The invention will be described below with reference to

Embodiments explained in more detail in connection with Figures 1 to 5.

Show it:

FIG. 1A shows a schematic illustration of a cross section through an exemplary embodiment of an edge-emitting semiconductor laser,

FIG. 1B shows a schematic representation of a plan view of the exemplary embodiment illustrated in FIG. 1A,

Figure 2 is a graphical representation of the optical

Output power as a function of the operating current intensity for two embodiments of semiconductor lasers with different thicknesses of the waveguide region, 3 each a perspective view of an embodiment of an edge-emitting semiconductor laser without housing cover (left) and with housing cover (right),

Figure 4 is a graphical representation of the optical

Output power as a function of the operating current for five embodiments of edge emitting semiconductor lasers with different high reflectivity of

Radiation decoupling surface, and

Figure 5 is a graphical representation of the optical

Output power as a function of the operating current for another five embodiments of

Semiconductor lasers with different high reflectivity of the radiation decoupling surface.

Identical or equal components are provided in the figures with the same reference numerals. The components shown and the size ratios of the components with each other are not to be considered as true to scale.

In the figures IA and IB, an embodiment of an edge emitting semiconductor laser is shown in a cross section and in a plan view.

The edge-emitting semiconductor laser has a semiconductor body 10, in which a waveguide region 4 is contained. The waveguide region 4 comprises a first waveguide layer 2 a, a second waveguide layer 2 b, and a waveguide layer 2 a between the first waveguide layer 2 a and the second waveguide layer 2 a second waveguide layer 2b arranged active layer 3, which serves to generate laser radiation 5.

The active layer 3 of the edge-emitting semiconductor laser may in particular be a single or multiple quantum well structure. Within the scope of the application, the term quantum well structure includes any structure in which charge carriers undergo quantization of their energy states by confinement. In particular, the name includes

Quantum well structure no information about the dimensionality of the quantization. It thus includes quantum wells, quantum wires and quantum dots and any combination of these structures.

The waveguide region 4 is arranged between a first cladding layer 1 a and a second cladding layer 1 b following the waveguide region 4 in the growth direction of the semiconductor body 10. The first cladding layer 1a is thus arranged on a side facing a substrate 6 of the semiconductor body 10, and the second cladding layer 1b is arranged on a side of the semiconductor body 10 facing away from the substrate 6 from the active layer 3. The semiconductor layers 1b, 2b arranged above the active layer preferably form a p-doped region and the layers 1a, 2a arranged below the active layer 3 form an n-doped region.

The semiconductor body 10 of the edge-emitting semiconductor laser is preferably based on a

Nitride compound semiconductor. Nitride compound semiconductors are particularly suitable for generating radiation in the blue and blue-green spectral range. The emission wavelength of the Edge emitting semiconductor laser may be in particular in the range of about 430 nm to 540 nm.

The electrical contacting of the edge-emitting semiconductor laser is effected, for example, by a first electrical contact layer 11 on the rear side of the substrate 6 facing away from the active layer 3 and a second electrical contact layer 12 on a surface of the semiconductor body 10 opposite to the substrate 6.

The semiconductor body 10 may contain one or more further layers in addition to the semiconductor layers illustrated in FIG. 1A. For example, one or more intermediate layers may be arranged between the substrate 6 and the lower cladding layer 1a or between the upper cladding layer 1b and the second contact layer 12. Furthermore, it is also possible for one or more of the semiconductor layers of the semiconductor body 10 described above to be composed of a plurality of partial layers instead of a single layer. In particular, for example, the active layer 3 can be formed from a quantum well structure having a plurality of quantum layers arranged between barrier layers. Furthermore, it is also possible, for example, for a sub-layer with an increased electronic band gap to be embedded in the second waveguide layer 2 b (not illustrated), which acts as an electron barrier and leads to better charge carrier confinement in the active layer 3.

The cladding layers 1 a, 1 b advantageously have a lower refractive index than the waveguide layers 2 a, 2 b, as a result of which the laser radiation 5 propagating in the lateral direction essentially occurs in the waveguide region 4 is included. The laser modes propagating in the waveguide region 4 formed by the active layer 3, the first waveguide layer 2 a and the second waveguide layer 2 b penetrate only slightly into the cladding layers 1 a, 1 b.

The laser resonator of the edge-emitting semiconductor laser is formed by the side facets 7, 8 of the semiconductor body 10. The side facets 7, 8 are preferably each provided with a reflection-enhancing coating 9a, 9b. The reflection-enhancing coatings 9a, 9b may, for example, be formed from a multiplicity of alternating dielectric layers. In particular, the reflection-enhancing coatings 9a, 9b may each comprise a plurality of layer pairs of oxide layers having different refractive indices, such as comparatively low refractive index silica and relatively high refractive index tantalum pentoxide. Alternatively, it would also be possible to form the reflection-enhancing coatings 9a, 9b from alternating semiconductor layers with different refractive indices.

In the case of the edge-emitting semiconductor laser, the first side facet 7 serves as a radiation output surface. The

Laser radiation 5 is thus through the first Seitenfacette 7 with the preferably applied thereto reflection-enhancing coating 9a of the

Semiconductor body 10 emitted, wherein the main radiation direction of the laser radiation 5 perpendicular to

Side facet 7 of the semiconductor body 10 is aligned.

Thus, a part of the laser resonator formed in the first Seitenfacette 7 and the second Seitenfacette 8 propagating laser radiation at the first side facet 7 is coupled out of the semiconductor body 10, the reflection-enhancing coating 9a of the first side facet 7 preferably has a lower reflection R than the reflection-increasing coating 9b of the second side facet 8.

Due to diffraction effects, the entire laser radiation 5 is not emitted perpendicular to the radiation decoupling surface, but instead has a beam cone with an emission angle α _s , α _P. In a conventional semiconductor laser, the radiation angle α _s in a direction perpendicular to the layer plane of the active layer is considerably larger than the radiation angle α _P in the direction parallel to the layer plane of the active layer. In the context of the application, the emission angles α _s , α _P are each understood to be the full angular range in which the intensity of the emitted laser radiation 5 is not less than half the intensity maximum.

It has been found to be advantageous that the difference between the emission angle α _s in a direction perpendicular to the layer plane of the active layer 3 and the emission angle α _P in a direction parallel to the layer plane of the active layer 3 can be reduced by the thickness d of the waveguide region 4 is reduced. Of the

Waveguide region 4 preferably has a thickness d of 400 nm or less, more preferably 300 nm or less.

In this way it is achieved that the radiation angle α _s perpendicular to the layer plane of the active layer 3 and the radiation angle α _P parallel to the plane of the active layer. 3 preferably differ by less than a factor of 3, and more preferably by less than a factor of two.

FIG. 2 illustrates the influence of the thickness d of the waveguide region 4 on the characteristic curve of the edge-emitting semiconductor laser. The optical output power P as a function of the operating current intensity I for an edge-emitting semiconductor laser in which the thickness d of the waveguide region 4 is 600 nm (curve 21) in comparison with an edge-emitting semiconductor laser in which the thickness d of the waveguide region 4 is advantageously only 250 nm is (curve 22). In both exemplary embodiments, the reflectivity at the first side facet 7, which is equal to the radiation outcoupling surface, is 50 percent in each case and the reflectivity at the second side facet 8 is 95 percent in each case. The characteristic curve 22 of the edge-emitting semiconductor laser with advantageously small thickness of the waveguide region 4 of only 250 nm has a smaller slope than the characteristic curve 21 of the edge-emitting semiconductor laser with a thickness d of the waveguide region 4 of 600 nm. The lower steepness of the characteristic, which results from the reduction of the thickness of the waveguide region 4, is disadvantageous if a high output power of the semiconductor laser is desired. On the other hand, however, the flatter characteristic curve 22 has the advantage that comparatively small output powers, in particular output powers of 10 mW or less, can be adjusted more precisely by adjusting the operating current intensity I. The semiconductor laser with the flatter characteristic curve 22 is advantageously also less sensitive to external influences such as, for example a temperature change or an aging-related shift of the threshold current.

The edge-emitting semiconductor laser having a thickness d of the waveguide region 4 of 600 nm has an emission angle α _P in the direction parallel to the layer plane of the active layer 3 of about 8.3 degrees. In the direction perpendicular to the layer plane of the active layer 3, the radiation angle α _{s is} about 22.4 degrees. Thus, the ratio of the radiation angle α _s to the radiation angle α _{P is} approximately

2.7. The edge-emitting semiconductor laser having the characteristic curve 22 and a thickness d of the waveguide region 4 of 250 nm, on the other hand, has an emission angle α _P of 11.9 degrees and an emission angle α _s of approximately 18.6 degrees. Due to the reduction in the thickness d of the waveguide region, the ratio of the emission angle α _s to the emission angle α _P is therefore only about 1.57. The edge-emitting semiconductor laser with the reduced thickness d of the waveguide region 4 thus advantageously has a less elliptical beam profile than the semiconductor laser with the larger thickness d of the waveguide region.

The low ellipticity of the beam profile of the semiconductor laser due to the comparatively small thickness of the waveguide region 4 has the advantage that comparatively simple and cost-effective optical elements for beam shaping can be used. In contrast, conventional high power semiconductor lasers often employ sophisticated aspherical lenses or lens systems to reduce beam divergence in the field

Direction parallel and perpendicular to the semiconductor layers to match each other. In the edge-emitting semiconductor laser described herein, preferably only a single lens used for beam shaping. The lens is preferably a spherical lens that can be easily and inexpensively manufactured.

The preferably spherical lens may be integrated in a housing of the edge-emitting semiconductor laser. An embodiment of the edge-emitting semiconductor laser with a so-called TO package (transistor outline) is shown in FIG. In the right half of Figure 3, the housing is shown with housing cover 18 and in the left half of Figure 3 for clarity without housing cover. The housing 14 has a housing base body 15, from which three connecting legs 16, which serve for mounting and electrical contacting of the edge emitting semiconductor laser, protrude. The semiconductor body 10 is advantageously mounted on a heat sink 17, via which the heat loss of the semiconductor body 10 is dissipated. For electrical contacting, the semiconductor body 10 is electrically conductively connected by means of bonding wires to two connection legs 16 of the housing. The semiconductor body 10 is mounted vertically in the housing, so that the main emission of the laser radiation is perpendicular to the housing base 15 of the housing 14. As shown in the right half of Figure 3, the housing 14 preferably has a housing cover 18, in which in the beam direction of the semiconductor body 10, a lens 19 for beam shaping of the laser radiation is integrated. The lens 19 may be in particular a simple and inexpensive to produce spherical lens.

It can be seen from FIG. 2 already explained above that the edge-emitting semiconductor laser with the characteristic curve 22 and a thickness d of the waveguide region 4 is only 250 nm has a larger threshold current than the edge-emitting semiconductor laser with the steeper characteristic 21 and the comparatively thick

Waveguide region 4 having a thickness of 600 nm. The increase in the threshold current intensity by the reduction in the thickness of the waveguide region 4 can be counteracted by increasing the reflectivity of the first side facet 7 of the semiconductor laser, which serves as a radiation output surface. This will be explained below with reference to the characteristic curves illustrated in FIGS. 4 and 5 of edge-emitting semiconductor lasers with different high reflectivity of the first side facet.

FIG. 4 shows a graphical representation of the optical output power P as a function of

Operating current I for embodiments of edge-emitting semiconductor lasers in which the reflectivity Ri serving as radiation coupling surface first Seitenfacette 50 percent (curve 41), 75 percent (curve 42), 85 percent (curve 43), 90 percent (curve 44) and 95

Percent (curve 45). The reflectivity R2 of the second side facet of the semiconductor laser is 95 percent in all cases. The reflectivity Ri of the first side facet can be modified in particular by changing a reflection-enhancing coating which is applied to the first side facet of the

Semiconductor laser is applied to be changed. In particular, the combination of materials or the number of alternating layers of a dielectric mirror can be changed to set a desired reflectivity.

Fig. 4 illustrates that the steepness of the characteristics with increasing reflectivity at the radiation output surface decreases and simultaneously decreases the threshold current. A low slope of the characteristic and a low threshold current have the advantage that a desired optical output power can be accurately adjusted by the control of the operating current, and that an increase in the threshold current, which may arise due to aging effects of the semiconductor laser, does not lead to failure of the semiconductor laser because the operation takes place even at low output power with operating currents that are well above the laser threshold. Advantageously, the reflectivity Ri of the reflection-enhancing coating of the first side facet of the semiconductor laser is at least 75 percent. The reflectivity Ri of the first side facet is particularly preferably at least 85 percent and particularly preferably at least 90 percent.

FIG. 5 shows the optical output power P as a function of the operating current intensity I for five further embodiments of edge-emitting semiconductor lasers in which the reflectivity Ri at the first side facet is 50 percent (curve 51), 75 percent (curve 52), 85 percent (curve 53), 90 percent (curve 54) and 95 percent (curve 55). In contrast to the exemplary embodiments illustrated in FIG. 4, the reflectivity R2 of the second side facet of the semiconductor laser is not 95 percent, but only 85 percent. Like the characteristic curves shown in FIG. 4, the characteristic curves shown in FIG. 5 also show that with increasing reflectivity Ri of the first side facet, the

Radiation coupling surface is used, the slope of the characteristics is reduced and the threshold current decreases. A lower reflectivity R2 of the second side facet of the semiconductor laser, which is opposite to the radiation coupling-out surface, can be used, for example, to decouple a small portion of the laser radiation for a monitor diode on the second side facet of the semiconductor laser. For example, as shown in FIG. 1B, the second side facet 8 of the semiconductor laser can be followed by a monitor diode 13. By means of the monitor diode 13 can be determined by external influences such as changes in temperature or due to aging of the semiconductor laser changes in the optical output power. The monitor diode 13 is preferably connected to an electrical control circuit by which the operating current is adjusted to achieve a desired optical output power.

An increase in the reflectivity Ri as

Radiation Auskoppelfläche serving first Seitenfacette 7 of the semiconductor laser has the advantage that the resonator length of the semiconductor laser can be reduced at the same operating current without the laser threshold is exceeded. In particular, a shortening of the resonator length from an original resonator length L _a to a resonator length L _{b can} be compensated for by increasing the reflectivity Ri, _{b of} the first side facet 7 relative to the original reflectivity Ri, _{a of} the first side facet 7 of the semiconductor laser as follows:

By reducing the resonator length of the semiconductor laser, it is possible to manufacture a larger number of semiconductor lasers on a wafer, thereby advantageously reducing the manufacturing cost. Preferably, the length of the laser resonator is 450 μm or less.

The edge-emitting semiconductor laser described herein is advantageously used in applications where a low output power of, for example, 10 mW or less, preferably 5 mW or less, is sufficient, but a stable operation over the life of the device and a low-cost manufacturing process is desired.

The invention is not limited by the description with reference to the embodiments. Rather, the includes

Invention, each novel feature and any combination of features, which includes in particular any combination of features in the claims, even if this feature or this combination is not even explicitly stated in the claims or exemplary embodiments.

Claims

claims

An edge emitting semiconductor laser comprising a semiconductor body (1) having a waveguide region (4), wherein

- The waveguide region (4) has a first waveguide layer (2A), a second

Waveguide layer (2B) and an active layer (3) arranged between the first waveguide layer (2A) and the second waveguide layer (2B) for generating laser radiation (5),

- The waveguide region (4) between a first cladding layer (IA) and the waveguide region (4) in the growth direction of the semiconductor body (10) subsequent second cladding layer (IB) is arranged, characterized in that

the waveguide region (4) has a thickness d of 400 nm or less, and

an emission angle α _{P of} the laser radiation (5) emerging from the semiconductor body (10) in a direction parallel to the layer plane of the active layer (3) and the emission angle α _s in a direction perpendicular to the layer plane of the active layer (3) Semiconductor body (10) emerging laser radiation (5) differ by less than a factor of 3 from each other.

The edge emitting semiconductor laser according to claim 1, wherein the waveguide region (4) has a thickness d of 300 nm or less.

3. Edge-emitting semiconductor laser according to claim 1 or

2, wherein the emission angle 0C _s and the emission angle CCp differ by less than a factor of 2 from each other.

4. Edge-emitting semiconductor laser according to one of the preceding claims, which has a lens (19) for beam shaping of the laser radiation (5).

The edge emitting semiconductor laser of claim 4, wherein the lens (19) is a spherical lens.

The edge emitting semiconductor laser according to claim 4 or 5, wherein the lens is contained in a housing (14) of the semiconductor laser.

7. The edge emitting semiconductor laser of claim 6, wherein the housing (14) is a TO package or an SMT package.

8. Edge-emitting semiconductor laser according to one of the preceding claims, in which a radiation output surface serving as first side facet (7) of the semiconductor body (10) with a reflection-increasing coating (9A) is provided.

The edge emitting semiconductor laser of claim 8, wherein the reflection of the reflection enhancing Coating (9A) is 75% or more.

The edge-emitting semiconductor laser according to claim 9, wherein the reflection of the reflection-enhancing coating (9A) is 85% or more.

The edge-emitting semiconductor laser according to claim 10, wherein the reflection of the reflection-enhancing coating (9A) is 95% or more.

12. Edge emitting semiconductor laser according to one of the preceding claims, wherein one of the radiation coupling-out opposite second side facet (8) of the semiconductor laser is arranged downstream of a monitor diode (13).

13. The edge-emitting semiconductor laser according to any one of the preceding claims, comprising a laser resonator with a length of 450 microns or less.

The edge emitting semiconductor laser according to any one of the preceding claims, which has an optical output power of 10 mW or less.

15. Edge emitting semiconductor laser according to one of the preceding claims, wherein the emitted laser radiation (5) a

Has intensity maximum at a wavelength between 430 nm and 540 nm.