Laser device

Abstract

A VCSEL (10) having a main body (12), which has a resonator (14) for forming a particular laser mode, and which has an inner Bragg mirror and a coupling-out mirror which is adjacent to an outer face (16) of the main body (12), wherein an active layer for generating light is arranged between the Bragg mirrors, wherein on the outer face (16) an emission region (20) is provided that has at least two coupling-out facets (22) which are positioned at locations on the outer face (16) that match locations of intensity maxima (19) of the laser mode such that the particular laser mode is stabilised, wherein the coupling-out facets (22) have a facet reflectivity that is higher than a surface reflectivity of the remaining emission region (20), wherein the coupling-out facets (22) do not have a circular outer contour (24).

Description

[0001] Laser device

[0002] The invention relates to a VCSEL for emitting laser light.

[0003] It is proposed to provide a VCSEL with a base body which has a resonator for forming a specific laser mode, which has an inner Bragg mirror and a Bragg mirror adjacent to an outer surface of the base body, which Bragg mirror functions as an output mirror, wherein an active layer for generating light is arranged between the Bragg mirrors, wherein an emission region is provided on the outer surface, which emission region has at least two output facets which are positioned at locations on the outer surface that correspond to locations of intensity maxima of the laser mode, such that the specific laser mode is stabilized, wherein the output facets have a facet reflectivity that is higher than a surface reflectivity of the remaining emission region, wherein the output facets do not have a circular outer contour.The emission region is formed on the outer surface of the output mirror, while the output facets are enclosed within the emission region. The respective output facets are positioned at locations where the intensity maxima of a specific laser mode develop. This promotes and stabilizes this specific laser mode, as the light at the locations of the intensity maxima is reflected into the cavity between the Bragg mirrors, while the light in the remaining emission region is reflected to a comparatively lesser extent.

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

[0005] Advantageously, the outer contour has a greater extension along a length axis than along a width axis, wherein the length axis is oriented 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 oriented perpendicular to a stacking direction of the Bragg mirrors. Preferably, the width axis is arranged along the greatest width, and the length axis is arranged along the greatest length of the outer contour.

[0006] Preferably, the outer contour is substantially elliptical, rectangular, or diamond-shaped. The width axis is, for example, the minor semi-axis and the length axis the major semi-axis of the ellipse. The same applies to the diagonals of the rhombus or the side lengths of the rectangle, so that the width axis is smaller than the length axis. In a particular refinement, at least two outer contours are shaped differently from one another. At least two output facets have outer contours that are not identical in shape. This can promote certain modes.

[0007] It is particularly preferred to arrange a facet row with more than two coupling-out facets along an imaginary line, wherein the outermost coupling-out facet at the respective longitudinal ends of the facet row has an outer contour that is preferably different from the other coupling-out facets of the facet row.

[0008] Advantageously, at least two contour distances along the imaginary line between two directly adjacent outer contours are of different sizes, with the contour distance being positioned between directly adjacent intersection points of the respective outer contour with the imaginary line. The contour distances are the distances between the nearest contour sections of two adjacent outer contours.

[0009] It is preferred that the distances between middle outer contours along the imaginary line are smaller than the remaining distances between adjacent outer contours of the same row of facets.

[0010] To achieve efficient light extraction, two directly adjacent outer contours can intersect, merging into one another. To achieve polarization of the extracted light, a polarization grating can be arranged on at least one extraction facet, with at least two central extraction facets of the facet row preferably having a polarization grating.

[0011] An advantageous further development can include the facet reflectivity of the output facets in the region of the outer contour continuously decreasing along a depression section to the level of the surface reflectivity of the remaining emission region. The depression section has a shortest dimension along which the facet reflectivity decreases, which is preferably 0.1 to 3 micrometers. The depression section can, for example, be designed as a seam-like circumferential edge around an output facet. The depression section can reduce diffraction effects at the edge of the output facet.

[0012] For example, the length axis can be aligned perpendicular to the imaginary line, while the width axis can be aligned parallel to or on the imaginary line.

[0013] Preferably, an intersection distance is formed between adjacent intersection points of the length axes and the imaginary line, with at least two intersection distances being of different sizes. Purely by way of example, the intersection distances of the middle output facets of the facet row are smaller than the intersection distances in the region of the longitudinal ends of the facet row. This enables optimal adjustment of the output facets according to the laser modes. Advantageously, the intersection distance between two adjacent output facets can be smaller than the extension of one of the adjacent output facets along the width axis. As a result, the adjacent output facets overlap, and the outer contours of adjacent output facets form intersection points.

[0014] It is particularly preferred if the outer contour of at least one coupling-out facet has a straight contour section. Corners and round sections may also be provided.

[0015] The scope of the invention is defined only by the claims.

[0016] The invention will be explained in more detail below using exemplary embodiments with reference to the accompanying drawings. Directional references in the following explanation are to be understood according to the reading direction of the drawings.

[0017] They show:

[0018] Fig. 1 , 2 and 4 to 7 different embodiments of facet rows,

[0019] Fig. 3 is a diagram showing an exemplary laser mode, and

[0020] Fig. 8 shows an output facet surrounded by a depression area.

[0021] The figures show VCSELs 10 (vertical-cavity surface-emitting lasers) comprising a base body 12. The base body 12 comprises a resonator 14 formed by two Bragg mirrors, with an inner Bragg mirror and an output mirror serving as Bragg mirrors. The output mirror borders an outer surface 16 of the base body 12. A specific laser mode 18 forms within the resonator 14, which is fed by light from an active layer arranged between the Bragg mirrors.

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

[0023] The Bragg mirrors and the active layer are stacked on top of each other, with a stacking direction oriented perpendicular to the main extension planes of the layers of the Bragg mirrors and the active layer.

[0024] On the outer surface 16, an emission region 20 is provided, which has at least two output facets 22. The light of the laser mode 18 emerges from the output facets 22. The output facets 22 are positioned at locations on the outer surface 16 that correspond to locations of intensity maxima 19 of the laser mode 18. The output facets 22 are arranged at locations on the outer surface 16 that border the spatial volumes within the resonator 14 that contain the antinodes of a standing wave underlying the laser mode 18. The respective intensity maxima of the exemplary illustration in Fig. 3 are also positioned in these spatial volumes. The output facets 22 have a facet reflectivity that is higher than a surface reflectivity of the remaining emission region 20. This stabilizes the specific laser mode 18 because the corresponding intensity maxima are promoted.

[0025] The output facets 22 do not have a circular outer contour 24. The outer contour 24 separates the output facet 22 from the remaining emission region 20. The outer contour 24 separates the region with high facet reflectivity and low surface reflectivity.

[0026] In Fig. 1, the outer contour 24 has a greater extension along a length axis 26 of the respective coupling facet 22 than along a width axis 28 of the coupling facet 22. The length 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.

[0027] Preferably, the width axis 28 is arranged along the greatest width and the length axis 26 along the greatest length of the outer contour 24. This results in an elliptical outer contour 24. Other shapes such as rectangles or diamonds are also conceivable.

[0028] Fig. 3 shows that the intensity distribution around the intensity maxima 19 is non-circular. The output facets 22 and the outer contour 24 are selected accordingly.

[0029] The output facets 22 of Figure 1 are arranged in a facet row 30 with more than two output facets 22 along an imaginary line 32. The imaginary line 32 is a straight line. The width axes 28 lie on the imaginary line 32. In particular, the imaginary line runs along a common axis of symmetry of the output facets 22.

[0030] Eight coupling-out facets 22 are provided in Fig. 1 by way of example, since the laser mode 18 from Fig. 3 has eight intensity maxima 19.

[0031] Fig. 2 shows that directly adjacent outer contours 24 intersect, so that they merge into one another. As a result, the output facets 22 overlap. The overlapping areas of the output facets 22 lie on the imaginary line 32. Accordingly, the output facets 22 are connected to one another to form a continuous row of facets 30.

[0032] In Fig. 4, the respective outer contour 24 of the outermost coupling facets 221 at the longitudinal ends of the facet row 30 is shaped differently than the outer contours 24 of the coupling facets 22 between the outermost coupling facets 221. For example, the dimensions of the width axes 281 can be longer than the length axes 261 of the outer contour 241 of the outermost coupling facets 221, while the dimensions of the width axes 28 are shorter than the length axes 26 of the outer contour 24 of the remaining coupling facets 22.

[0033] According to Fig. 3, the laser mode 18 has intensity distributions at the outermost intensity maxima 19 that are different from the remaining intensity distribution of the respective intensity maxima 19 located between the outermost intensity maxima 191. Preferably, the dimensions of the output facets 22 of the facet row 30 are the same along the respective longitudinal axes 26, 261. In particular, only the dimensions along the width axes 28, 281 of the output facets 22, 221 differ. Particularly preferably, the shapes of the outer contours 24 between the outermost outer contours 241 are identical to one another.

[0034] In Fig. 5, a further embodiment is shown in which the outermost outer contours 241 do not have an elliptical shape, as is the case with the outermost outer contours 241 in Fig. 4, but have straight contour sections 242 aligned parallel to the imaginary line 32.

[0035] Fig. 6 shows a further embodiment in which the distances 38 between the longitudinal axes 26 of adjacent output facets 22 are of different sizes. In particular, the distances 38 can become smaller toward the center 40, so that the distance 380 between the two longitudinal axes 26 of the central output facets 22 is smaller than the distances 381, 382, ​​383 of the remaining output facets 22. The distance 38 can increase successively starting from the center, so that the outermost distance 383 is the largest.

[0036] The distances between the outer contours 22, i.e., the contour distances, can also vary. For example, the contour distances can be measured along the imaginary line 32 between two opposite, closest points of adjacent outer contours 24. The closest points can also be intersection points of the outer contour 22 with the imaginary line 32. Like the distances 38, the contour distances can become increasingly larger from the center outward.

[0037] If the intersection distance between two adjacent output facets 22 is smaller than the extension of one of the adjacent output facets 22 along the width axis 28, then the output facets 22 overlap, and the outer contours 24 of adjacent output facets 22 in turn form intersection points. The adjacent outer contours 24 then merge into one another as shown in Fig. 3.

[0038] Fig. 7 shows a further embodiment in which the two middle output facets 22 have a polarization grating 42. Alternatively, more than two output facets 22 can have a polarization grating 42. Further alternatively, only the outer output facets 22 can have a polarization grating 42 or other decentrally arranged output facets 22.

[0039] In Fig. 8, a coupling-out facet 22 is shown which has a lowering section 50 which is arranged in the region of the outer contour 24.

[0040] Along the lowering section 50, the facet reflectivity continuously decreases to the level of the surface reflectivity of the remaining emission region 20.

[0041] In the exemplary embodiment of Fig. 8, the reflectivity decreases along a shortest dimension 52. The dimension 52 of the lowered section 50 is preferably 0.1 to 3 micrometers. The lowered section 50 is formed in a seam-like manner around an output facet 22 and extends along the outer contour 24. The dimension 52 can always be constant and preferably perpendicular to the outer contour 24.

[0042] The features of the embodiments can be combined with one another. For example, the polarization grating can be used on any of the embodiments. Furthermore, the spacing between the output facets can be varied in each embodiment. Likewise, the shapes of the individual output facets can be varied accordingly. Multiple rows of facets can also be implemented, arranged, for example, parallel or perpendicular to one another.

Claims

Patent claims VCSEL (10) with a base body (12) which has a resonator (14) for forming a specific laser mode, which has an inner Bragg mirror and an output mirror adjacent to an outer surface (16) of the base body (12), wherein an active layer for generating light is arranged between the Bragg mirrors, wherein an emission region (20) is provided on the outer surface (16) and has at least two output facets (22) which are positioned at locations on the outer surface (16) which correspond to locations of intensity maxima (19) of the laser mode, so that the specific laser mode is stabilized, wherein the output facets (22) have a facet reflectivity which is higher than a surface reflectivity of the remaining emission region (20), wherein the output facets (22) do not have a circular outer contour (24).VCSEL (10) according to claim 1, characterized in that the outer contour (24) has a greater extent along a length axis (26) than along a width axis (28), wherein the length axis (26) is oriented perpendicular to the width axis (28), wherein the length axis (26) and the width axis (28) are oriented parallel to the outer surface (16). VCSEL (10) according to claim 1 or 2, characterized in that the outer contour (24) is substantially elliptical, rectangular, or diamond-shaped. VCSEL (10) according to one of the preceding claims, characterized in that at least two outer contours (24) are shaped differently from one another. VCSEL (10) according to one of the preceding claims, characterized in that a facet row (30) with more than two coupling-out facets (22) is arranged along an imaginary line (32), wherein the outermost coupling-out facet (22) at the respective longitudinal ends of the facet row (30) has an outer contour (24) that is preferably different from the remaining coupling-out facets (22) of the facet row (30). VCSEL (10) according to claim 5, characterized in that at least two contour distances along the imaginary line (32) between two directly adjacent outer contours (24) are of different sizes, wherein the contour distance is positioned between directly adjacent intersection points of the respective outer contour (24) with the imaginary line (32).VCSEL (10) according to claim 6, characterized in that the distances between central outer contours (24) with respect to the imaginary line (32) are smaller than the remaining distances () between adjacent outer contours (24) of the same facet row (30). VCSEL (10) according to one of the preceding claims, characterized in that two directly adjacent outer contours (24) intersect with one another, so that they merge into one another. VCSEL (10) according to one of the preceding claims, characterized in that a polarization grating (42) is arranged on at least one coupling-out facet (22), wherein preferably at least two middle coupling-out facets (22) of the facet row (30) have a polarization grating (42). VCSEL (10) according to one of the preceding claims, characterized in that the facet reflectivity of the coupling-out facets (22) in the region of the outer contour (24) continuously decreases along a depression section (50) to the level of the surface reflectivity of the remaining emission region (20), wherein the depression section (50) has a shortest dimension along which the facet reflectivity decreases, which is preferably 0.1 to 3 micrometers.VCSEL (10) according to one of the preceding claims and claims 2 and 5, characterized in that the length axis (26) is perpendicular to the imaginary line (32), while the width axis (28) is parallel to or on the imaginary line (32). VCSEL (10) according to claim 11, characterized in that an intersection point distance is formed between adjacent intersection points of the length axes (26) and the imaginary line (32), wherein at least two intersection point distances are of different sizes. VCSEL (10) according to claim 12, characterized in that the. Intersection distances of the middle coupling facets (22) of the Facet row (30) are smaller than the intersection distances in the region of the longitudinal ends of the facet row (30). VCSEL (10) according to claim 12 or 13, characterized in that the intersection distance between two adjacent coupling-out facets (22) is smaller than the extension of one of the adjacent coupling-out facets (22) along the width axis (28). VCSEL (10) according to one of the preceding claims, characterized in that the outer contour (24) of at least one coupling-out facet (22) has a straight contour section (242).

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