Laser device

Abstract

The VCSEL (10) has a body (12) with a resonator (14) for forming a specific laser mode and an output coupling mirror adjacent to the outer surface (16) of the body (12) and the internal Bragg mirror. The active layer for generating light is disposed between the Bragg mirrors, and at least two output coupling facets (22) are provided on the outer surface (16) and are arranged at positions that coincide with the positions of the maxima (19) of the intensity of the laser mode so that the specific laser mode is stabilized. The output coupling facets (22) have a facet reflectivity higher than the surface reflectivity of the remaining light emitting region (20), and the output coupling facets (22) do not have a circular outer contour (24).

Description

Technical Field

[0001] The present invention relates to a VCSEL for emitting laser light.

Background Art

[0002] A VCSEL is proposed that has a resonator for forming a specific laser mode, an internal Bragg mirror, and a Bragg mirror adjacent to the outer surface of the body that functions as an output coupling mirror, and has a body. The active layer for generating light is disposed between the Bragg mirrors, and there is provided on the outer surface a light emitting region having at least two output coupling facets disposed at positions on the outer surface that coincide with the positions of the maxima of the intensity of the laser mode so that the specific laser mode is stabilized. The output coupling facets have a facet reflectivity higher than the surface reflectivity of the remaining light emitting region, and the output coupling facets do not have a circular outer contour.

[0003] The light emitting region is formed on the outer surface of the output coupling mirror, but the output coupling facets are surrounded by the light emitting region. Each output coupling facet is disposed at a position where a maximum of the intensity of a specific laser mode is formed. The light at the position of the maximum of the intensity is reflected within the cavity between the Bragg mirrors, but the reflection of the light in the area of the remaining light emitting region is less compared thereto, thereby promoting and stabilizing this specific laser mode.

[0004] Further embodiments and developments are described in the dependent claims.

[0005] Advantageously, the outer contour has a greater extension along the length axis than along the width axis. The length axis is aligned perpendicular to the width axis, and the length axis and the width axis are aligned parallel to the outer surface. The length axis and the width axis are aligned perpendicular to the stacking direction of the Bragg mirrors. Preferably, the width axis is arranged along the maximum width, and the length axis is arranged along the maximum length of the outer contour.

[0006] Preferably, the outer contour is substantially elliptical, rectangular or rhombic. For example, the width axis is the minor semi-axis of the ellipse and the length axis is the major semi-axis. The same applies to the diagonal of the rhombus or the side length of the rectangle such that the dimension of the width axis is smaller than the dimension of the length axis.

[0007] In a specific development form, at least two outer contours are of different shapes compared to each other. At least two output coupling facets have outer contours that do not have the same shape. Thereby, a certain specific mode can be promoted.

[0008] It is particularly desirable to arrange the facet row with three or more output coupling facets along an imaginary line, and the outermost output coupling facets at both longitudinal ends of the facet row preferably have an outer contour different from the other output coupling facets of the facet row.

[0009] Advantageously, the intervals between at least two contours along the imaginary line between two directly adjacent outer contours are of different sizes, and the contour intervals are arranged between each outer contour and the directly adjacent intersection of the imaginary line. The contour interval is the interval between the contour parts adjacent to two adjacent outer contours.

[0010] It is desirable that the interval between the central outer contours is smaller than the remaining intervals between the adjacent outer contours of the same facet row with respect to the imaginary line.

[0011] To achieve high-efficiency light extraction, two directly adjacent outer contours may intersect so as to cross each other.

[0012] To realize the polarization of the output coupling light, the polarization grating can be arranged on at least one output coupling facet, and preferably at least two central output coupling facets of the facet row have the polarization grating.

[0013] A further advantageous development can include that the facet reflectivity of the output coupling facet within the region of the outer contour continuously decreases along the descending portion to the level of the surface reflectivity of the remaining light emitting region, the descending portion being the shortest dimension along which the facet reflectivity decreases, preferably being from 0.1 to 3 micrometers. The descending portion can be designed as a peripheral area, for example, a seam around the output coupling facet. The descending portion can reduce the diffraction effect at the edge of the output coupling facet.

[0014] For example, the longitudinal axis can be aligned perpendicular to the imaginary line, while the width axis can be aligned parallel to or on the imaginary line.

[0015] Preferably, the intersection intervals are formed between adjacent intersections of the longitudinal axis and the imaginary line, and the distances of at least two intersections are different. By way of pure example, the intersection interval of the central output coupling facet of the facet row is smaller than the intersection intervals in the regions at both longitudinal ends of the facet row. This enables the optimal adjustment of the output coupling facet according to the laser mode.

[0016] Advantageously, the intersection interval between two adjacent output coupling facets can be smaller than the extension of one of the adjacent output coupling facets along the width axis. As a result, the adjacent output coupling facets overlap, and the outer contours of the adjacent output coupling facets form intersections.

[0017] It is particularly desirable that the outer contour of at least one output coupling facet has a straight contour portion. Corners and rounded portions can also be provided.

[0018] The scope of the present invention is defined only by the claims.

[0019] The present invention will be described in more detail below based on exemplary embodiments with reference to the accompanying drawings. The direction indications in the following description should be understood in accordance with the direction of reading the drawings.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

[0021] These figures show a VCSEL 10 (vertical-cavity surface-emitting lasers) having a body 12. The body 12 includes a resonator 14 formed by two Bragg reflectors, and the internal Bragg reflector and the output coupling mirror are provided as Bragg reflectors. The output coupling mirror is in contact with the outer surface 16 of the body 12. Inside the resonator 14, a specific laser mode 18 is formed by the light from the active layer disposed between the Bragg reflectors.

[0022] Figure 3 shows such a laser mode 18 in which a plurality of intensity maxima 19 are arranged along the imaginary line 32. The imaginary line 32 represents the x-axis 33, and the longitudinal axis 26 represents the y-axis of the graph in Figure 3. The curves in the graph show the intensity distribution along the axes 33, 35.

[0023] The Bragg mirror and the active layer are stacked on top of one another, and the stacking direction is oriented perpendicular to the main extension plane of the layers of the Bragg mirror and the active layer.

[0024] On the outer surface 16, a light-emitting region 20 having at least two output coupling facets 22 is provided. The light of the laser mode 18 exits from the output coupling facet 22. The output coupling facet 22 is arranged at a position on the outer surface 16 and is at the same position as the intensity maximum 19 of the laser mode 18. The output coupling facet 22 is arranged at a position on the outer surface 16, is in contact with the spatial volume of the resonator 14, and has an antinode of the standing wave at the base of the laser mode 18. Each intensity maximum in the exemplary representation in Figure 3 is also located in these spatial volumes.

[0025] The output coupling facet 22 has a facet reflectivity higher than the surface reflectivity of the remaining light-emitting region 20. As a result, the corresponding intensity maximum is promoted, so that the specific laser mode 18 is stabilized.

[0026] The output coupling facet 22 does not have a circular outer contour 24. The output coupling facet 22 is separated from the remaining light-emitting region 20 by the outer contour 24. The outer contour 24 separates an area having a high facet reflectivity and a low surface reflectivity.

[0027] In Figure 1, the outer contour 24 has a greater extension along the longitudinal axis 26 of each output coupling facet 22 than along the width axis 28 of the output coupling facet 22. The longitudinal axis 26 is aligned perpendicular to the width axis 28 and is aligned parallel to the outer surface 16 and perpendicular to the stacking direction.

[0028] Preferably, the width axis 28 is arranged along the maximum width, and the length axis 26 is arranged along the maximum length of the outer contour 24. The result is an elliptical outer contour 24. Other shapes such as rectangles or rhombuses are also conceivable.

[0029] FIG. 3 shows that there is a non-circular intensity distribution around the maximum intensity 19. The output coupling facet 22 and the outer contour 24 are selected accordingly.

[0030] The output coupling facet 22 in FIG. 1 is arranged in a facet row 30 in which three or more output coupling facets 22 are arranged along the imaginary line 32. The imaginary line 32 is a straight line. The width axis 28 is located on the imaginary line 32. The imaginary line is, in particular, along the common axis of symmetry of the output coupling facets 22.

[0031] Since the laser mode 18 in FIG. 3 has eight intensity maxima 19, eight output coupling facets 22 are provided as an example in FIG. 1.

[0032] FIG. 2 shows that the directly adjacent outer contours 24 intersect so that they cross each other. As a result, the output coupling facets 22 overlap each other. The overlapping area of the output coupling facets 22 is located on the imaginary line 32. Therefore, the output coupling facets 22 are combined with each other to form a continuous facet row 30.

[0033] In FIG. 4, the outer contours 24 of the outermost output coupling facets 221 at both longitudinal ends of the facet row 30 have different shapes from the outer contours 24 of the output coupling facets 22 between the outermost output coupling facets 221. For example, the dimension of the width axis 281 may be longer than the length axis 261 of the outer contour 241 of the outermost output coupling facet 221, but the dimension of the width axis 28 is shorter than the length axis 26 of the outer contour 24 of the remaining output coupling facets 22.

[0034] According to FIG. 3, the laser mode 18 has an intensity distribution at the outermost intensity maximum 19, which is different from the remaining intensity distributions of the respective intensity maxima 19 located between the outermost intensity maxima 191.

[0035] Preferably, the dimensions of the output coupling facet 22 of the facet row 30 along the respective longitudinal axes 26, 261 are of the same size. In particular, only the dimensions along the width axes 28, 281 of the output coupling facets 22, 221 are different. In particular, preferably, the shape of the outer contour 24 between the outermost outer contours 241 is identical to each other.

[0036] FIG. 5 shows a further embodiment in which the outermost outer contour 241 does not have an elliptical shape, but has a straight contour portion 242 aligned parallel to the imaginary line 32, similar to the outermost outer contour 241 in FIG. 4.

[0037] FIG. 6 shows a further embodiment in which the intervals 38 between the longitudinal axes 26 of the adjacent output coupling facets 22 are of different sizes. In particular, the interval 380 between the two longitudinal axes 26 of the central output coupling facet 22 may become smaller towards the center 40 so that it is smaller than the intervals 381, 382, 383 of the remaining output coupling facets 22. The interval 38 can gradually increase from the center so that the outermost interval 383 is the largest.

[0038] The interval between the outer contours 22 (i.e., the contour interval) may also vary. For example, the contour interval can be measured along the imaginary line 32 between the two opposite closest points of the adjacent outer contours 24. The adjacent points can also be the intersection points of the outer contour 22 and the imaginary line 32. Similar to the interval 38, the contour interval can gradually increase from the center towards the outside.

[0039] If the spacing between the intersections of two adjacent output coupling facets 22 is less than the extent of one of the adjacent output coupling facets 22 along the width axis 28, the output coupling facets 22 overlap and the outer contours 24 of the adjacent output coupling facets 22 successively form intersections with each other. Then, as shown in FIG. 3, the adjacent outer contours 24 intersect each other.

[0040] FIG. 7 shows a further embodiment in which two central output coupling facets 22 have a polarization grating 42. Alternatively, more than three output coupling facets 22 may have a polarization grating 42. Further alternatively, only the outer output coupling facets 22 may have a polarization grating 42 or other dispersedly arranged output coupling facets 22.

[0041] FIG. 8 shows an output coupling facet 22 having a descending portion 50 disposed within the region of the outer contour 24.

[0042] Along the descending portion 50, the facet reflectivity continuously decreases to the level of the surface reflectivity of the remaining light emitting region 20.

[0043] In the exemplary embodiment of FIG. 8, the reflectivity decreases along the shortest dimension 52. The dimension 52 of the descending portion 50 is preferably from 0.1 to 3 micrometers.

[0044] The descending portion 50 is formed like a seam around the output coupling facet 22 and extends along the outer contour 24. The dimension 52 is always constant and may preferably be perpendicular to the outer contour 24.

[0045] The features of the embodiments can be combined with each other. Therefore, the polarization grating can be used in any embodiment. Further, the spacing between the output coupling facets may vary from embodiment to embodiment. Similarly, the shape of the individual output coupling facets can vary accordingly. For example, it is also possible to create a plurality of facet rows arranged parallel or transverse to each other.

Claims

1. A VCSEL (10) having a resonator (14) for forming a specific laser mode, an internal Bragg reflector, and an output coupling mirror adjacent to an outer surface (16) of a body (12), wherein an active layer for generating light is disposed between the internal Bragg reflectors, and at least two output coupling facets (22) are disposed at positions on the outer surface (16) that coincide with positions of maxima (19) of the intensity of the laser mode so that the specific laser mode is stabilized. A light emitting region (20) having the output coupling facets (22) is provided on the outer surface (16), the output coupling facets (22) have a facet reflectivity higher than the surface reflectivity of the remaining light emitting region (20), and the output coupling facets (22) do not have a circular outer contour (24), the VCSEL (10).

2. The VCSEL (10) according to claim 1, wherein the outer contour (24) has an extension greater along a longitudinal axis (26) than along a width axis (28), the longitudinal axis (26) is aligned perpendicular to the width axis (28), and the longitudinal axis (26) and the width axis (28) are aligned parallel to the outer surface (16).

3. The VCSEL (10) according to claim 1 or 2, wherein the outer contour (24) is substantially elliptical, rectangular or rhombic.

4. The VCSEL (10) according to any one of claims 1 to 3, wherein at least two outer contours (24) have different shapes compared to each other.

5. A facet row (30) with three or more output coupling facets (22) is arranged along an imaginary line (32), and the outermost output coupling facets (22) at both longitudinal ends of the facet row (30) preferably have an outer contour (24) different from the remaining output coupling facets (22) of the facet row (30). The VCSEL (10) according to any one of claims 1 to 4.

6. The VCSEL (10) according to claim 5, characterized in that the distance between at least two contours along the imaginary line (32) between two directly adjacent outer contours (24) is of different sizes, and the distance between the contours is arranged between each of the outer contours (24) and the directly adjacent intersection of the imaginary line (32).

7. The VCSEL (10) according to claim 6, characterized in that the distance between the central outer contours (24) is smaller than the remaining distances between the adjacent outer contours (24) of the same facet row (30) with respect to the imaginary line (32).

8. The VCSEL (10) according to any one of claims 1 to 7, characterized in that the two directly adjacent outer contours (24) intersect such that the two directly adjacent outer contours (24) cross each other.

9. The VCSEL (10) according to any one of claims 1 to 8, characterized in that a polarization grating (42) is arranged on at least one output coupling facet (22), and preferably at least two central output coupling facets (22) of the facet row (30) have the polarization grating (42).

10. The VCSEL (10) according to any one of claims 1 to 9, characterized in that the facet reflectivity of the output coupling facet (22) within the region of the outer contour (24) continuously decreases along the descending part (50) to the level of the surface reflectivity of the remaining light emitting region (20), and the descending part (50) is the shortest dimension along which the facet reflectivity decreases, preferably 0.1 to 3 micrometers.

11. The VCSEL (10) according to any one of the preceding claims and claim 2 and claim 5, characterized in that the major axis (26) is perpendicular to the imaginary line (32), but the minor axis (28) is parallel to the imaginary line (32) or on the imaginary line.

12. The VCSEL (10) according to claim 11, characterized in that the intersection interval is formed between the major axis (26) and the directly adjacent intersection of the imaginary line (32), and at least two intersection distances are different.

13. The VCSEL (10) according to claim 12, characterized in that an interval between the intersections of the central output coupling facet (22) of the facet array (30) is smaller than an interval between the intersections in regions at both longitudinal ends of the facet array (30).

14. The VCSEL (10) according to claim 12 or 13, characterized in that an interval between the intersections of two adjacent output coupling facets (22) is smaller than an extension of one of the adjacent output coupling facets (22) along the width axis (28).

15. The VCSEL (10) according to any one of claims 1 to 14, characterized in that an outer contour (24) of at least one output coupling facet (22) has a linear contour portion (242).

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