阅读说明：本技术 提供弯曲端面的半导体激光器的技术 (Techniques for providing curved end facet semiconductor lasers ) 是由 林友熙 W·帕兹 N·比克尔 C·史塔加尔斯库 于 2018-11-15 设计创作，主要内容包括：公开了用于提供弯曲端面的半导体激光器的技术。在一个特定实施例中,该技术可以被实现为包括波导的半导体激光器,其中波导包括在半导体激光器的边缘处形成的端面,并且该端面具有曲率。(Techniques for providing a curved end facet semiconductor laser are disclosed. In one particular embodiment, the technique can be implemented as a semiconductor laser including a waveguide, wherein the waveguide includes an end face formed at an edge of the semiconductor laser, and the end face has a curvature.)

1. A semiconductor laser comprising:

a waveguide;

wherein the waveguide includes an end face formed at an edge of the semiconductor laser, and the end face has a curvature.

2. The semiconductor laser of claim 1, wherein facet curvature is based on a width of the facet or a depth of the facet.

3. The semiconductor laser of claim 2, wherein the depth of the end facet is measured from a minimum depth of the edge of the semiconductor laser to the end facet.

4. The semiconductor laser of claim 3, wherein the minimum depth of the end facet is located at a central region of the end facet.

5. The semiconductor laser of claim 1, wherein the facet curvature is based on a radius.

6. The semiconductor laser of claim 1, wherein the facet is configured to emit light, and the facet curvature reduces the degree of far field asymmetry of the emitted light relative to light emitted without the facet curvature.

7. The semiconductor laser of claim 1, wherein the end facet curvature is formed by chemically assisted ion beam etching.

8. The semiconductor laser of claim 1, wherein an end facet curvature is concave relative to the edge of the semiconductor laser.

9. The semiconductor laser of claim 1, wherein the facet curvature is convex with respect to the edge of the semiconductor laser.

10. The semiconductor laser of claim 1, wherein the end facet curvature satisfies the following equation:

(w/2)²+(r-1)²＝r²

where w is the width of the end face, r is the radius, and 1 is the depth of the end face.

11. A method of fabricating a semiconductor laser, comprising:

an end face of a waveguide is etched at an edge of a semiconductor laser including the waveguide, wherein the end face has a curvature.

12. The method of claim 11, wherein end face curvature is based on a width of the end face or a depth of the end face.

13. The method of claim 11, wherein the end face curvature is based on a radius.

14. The method of claim 11, wherein the end face curvature is formed by chemically assisted ion beam etching.

15. The method of claim 11 wherein the end facet curvature is concave relative to the edge of the semiconductor laser.

16. A method as in claim 11 wherein the facet curvature is convex with respect to the edge of the semiconductor laser.

17. A semiconductor laser comprising:

a waveguide; and

a substrate attached to the waveguide;

wherein the waveguide and the substrate include end faces formed at edges of the semiconductor laser, and the end faces have a curvature.

18. The semiconductor laser of claim 17, wherein an end facet curvature is concave relative to the edge of the semiconductor laser.

19. The semiconductor laser of claim 17, wherein the facet curvature is convex with respect to the edge of the semiconductor laser.

20. The semiconductor laser of claim 17, wherein the end facet curvature satisfies the following equation:

(w/2)²+(r-1)²＝r²

where w is the width of the end face, r is the radius, and 1 is the depth of the end face.

Technical Field

The present disclosure relates generally to semiconductors and, more particularly, to techniques for providing curved end facet semiconductor lasers.

Background

Semiconductor lasers are typically fabricated on a wafer by growing a suitable layered semiconductor material on a substrate by Metal Organic Chemical Vapor Deposition (MOCVD) or Molecular Beam Epitaxy (MBE) to form an epitaxial structure having an active layer parallel to the substrate surface. The wafer may then be processed using various semiconductor processing tools to produce a laser optical cavity that includes an active layer and metal contacts attached to the semiconductor material.

Laser mirror facets are typically formed at the ends of the laser cavity by cutting the semiconductor material along its crystal structure to define edges or ends of the laser optical cavity, such that when a bias voltage is applied to the contacts, a current is generated through the active layer, causing photons to be emitted from the facet edges of the active layer in a direction perpendicular to the current flow. Since the semiconductor material is cut to form the laser facets, the position and orientation of the facets are limited. Furthermore, once the wafer is diced, the lasers are typically small pieces, so that conventional photolithography techniques cannot be readily applied to further process the lasers.

Photons emitted from the edge of the end face may be emitted in different vertical and horizontal far field patterns, which may result in asymmetry between the vertical and horizontal far fields. This asymmetry may be detrimental to laser operation. For example, when a semiconductor laser is coupled to a transmission medium such as an optical fiber, the transmission medium may capture only a limited percentage of photons due to an asymmetric far-field pattern. Therefore, coupling loss may be increased. It may be necessary to use complex external aspheric optical elements (such as lenses) to correct the asymmetry and ensure reduced coupling losses. However, these optical components are often expensive and can increase the overall cost of manufacturing and using the semiconductor laser.

In view of the foregoing, it can be appreciated that there can be significant problems and disadvantages associated with current semiconductor laser fabrication techniques.

Disclosure of Invention

Techniques for providing a curved end facet semiconductor laser are disclosed. In one particular embodiment, the technique can be implemented as a semiconductor laser including a waveguide, wherein the waveguide includes an end face formed at an edge of the semiconductor laser, and the end face has a curvature.

In accordance with other aspects of this particular embodiment, the end face curvature may be based on the width of the end face.

In accordance with other aspects of this particular embodiment, the end face curvature may be based on the depth of the end face.

According to further aspects of this particular embodiment, the depth of the end facet may be measured from the edge of the semiconductor laser to the minimum depth of the end facet.

In accordance with further aspects of this particular embodiment, the minimum depth of the end face may be located in a central region of the end face.

In accordance with other aspects of this particular embodiment, the end face curvature may be based on a radius.

According to other aspects of this particular embodiment, the endface is configured to emit light, and the endface curvature reduces the degree of far field asymmetry in the emitted light relative to light emitted without said endface curvature.

In accordance with other aspects of this particular embodiment, the end face curvature may be formed by etching.

In accordance with further aspects of this particular embodiment, the etching may be chemically assisted ion beam etching.

In accordance with other aspects of this particular embodiment, the end facet curvature may be concave relative to an edge of the semiconductor laser.

In accordance with other aspects of this particular embodiment, the facet curvature may be convex with respect to the edge of the semiconductor laser.

In accordance with other aspects of this particular embodiment, the end face curvature may satisfy the following equation: (w/2)²+(r-1)²＝r²Where w is the width of the end face, r is the radius, and l is the depth of the end face.

In another particular embodiment, the technique may be realized as a method of fabricating a semiconductor laser, comprising: an end face is etched at an edge formed by the waveguide, wherein the end face has a curvature.

In accordance with other aspects of this particular embodiment, the end face curvature may be based on the width of the end face.

In accordance with other aspects of this particular embodiment, the end face curvature may be based on the depth of the end face.

In accordance with other aspects of this particular embodiment, the end face curvature may be based on a radius.

In accordance with other aspects of this particular embodiment, the end face curvature may be formed by chemically assisted ion beam etching.

In accordance with other aspects of this particular embodiment, the end facet curvature may be concave relative to an edge of the semiconductor laser.

In accordance with other aspects of this particular embodiment, the facet curvature may be convex with respect to the edge of the semiconductor laser.

In another particular embodiment, a semiconductor laser may include a waveguide and a substrate to which the waveguide is attached, wherein the waveguide and the substrate include an end face formed at an edge of the semiconductor laser, and the end face has a curvature.

In accordance with other aspects of this particular embodiment, the end facet curvature may be concave relative to an edge of the semiconductor laser.

In accordance with other aspects of this particular embodiment, the facet curvature may be convex with respect to the edge of the semiconductor laser.

In accordance with other aspects of this particular embodiment, the end face curvature may satisfy the following equation: (w/2)²+(r-1)²＝r²Where w is the width of the end face, r is the radius, and 1 is the depth of the end face.

The present disclosure will now be described in more detail with reference to specific embodiments thereof as illustrated in the accompanying drawings. While the present disclosure is described below with reference to specific embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein, and with respect to which the present disclosure may be of significant utility.

Drawings

To facilitate a fuller understanding of the present disclosure, reference is now made to the accompanying drawings, in which like elements are designated with like reference numerals. These drawings should not be construed as limiting the present disclosure, but are merely illustrative.

Fig. 1A illustrates a cross-sectional view of a semiconductor laser according to an embodiment of the present disclosure.

Fig. 1B illustrates a top view of a semiconductor laser according to an embodiment of the present disclosure.

Fig. 1C illustrates a three-dimensional cross-sectional view of a semiconductor laser according to an embodiment of the present disclosure.

Fig. 2A shows a simulated thermal map of light emitted from a semiconductor laser according to an embodiment of the present disclosure.

Fig. 2B illustrates a graph showing data of a thermal map of light emitted from a semiconductor laser in a graphical format, in accordance with an embodiment of the present disclosure.

Fig. 3A illustrates a top view of a semiconductor laser having a concavely curved end face in accordance with an embodiment of the present disclosure.

Fig. 3B illustrates a three-dimensional cross-sectional view of a semiconductor laser having a curved end face according to an embodiment of the present disclosure.

Fig. 3C shows an enlarged view of a curved end face of the semiconductor laser having a curved end face.

Fig. 4A shows a simulated thermal map of light emitted from a semiconductor laser having a curved endface in accordance with an embodiment of the present disclosure.

Fig. 4B illustrates a graph showing data in a graphical format of a thermal map of light emitted from a semiconductor laser having a curved endface, in accordance with an embodiment of the present disclosure.

Fig. 4C and 4D show examples of how the antireflection characteristic may be improved according to the laser end face according to an embodiment of the present disclosure.

Fig. 5A illustrates a graph showing different spans of horizontal angles of horizontal far field components of light emitted from a semiconductor laser having a curved end face, according to an embodiment of the present disclosure.

Fig. 5B shows an enlarged portion of the graph shown in fig. 5A.

Fig. 6A to 6C show experimental results obtained by testing a reference semiconductor laser and a semiconductor laser having a varying edge facet curvature according to an embodiment of the present disclosure.

Fig. 7 shows a graph reflecting the ratio of the output optical power in milliwatts (mW) to the current in milliamps (mA) of a semiconductor laser, in accordance with an embodiment of the present disclosure.

Fig. 8 illustrates a top view of a semiconductor laser having a convexly curved endface in accordance with an embodiment of the present disclosure.

Detailed Description

The disclosure and associated advantages are described and emphasized in the following description and the accompanying drawings, which are not necessarily drawn to scale. Detailed descriptions of some structures and processing techniques are omitted so as to not unnecessarily obscure the present disclosure.

Fig. 1A illustrates a cross-sectional view of a semiconductor laser 100 according to an embodiment of the present disclosure. The semiconductor laser 100 may be a ridge diode laser including a ridge 102. The semiconductor laser 100 may also include a waveguide 104 and a substrate 106. For example, the substrate 106 may be an indium phosphide (InP) based material and the waveguide 104 may be an aluminum gallium indium arsenide (AlGaInAs) based material. The ridge 102 may be, for example, an InP-based material. A spacer layer 114 may be positioned between the ridge 102 and the waveguide 104. The spacer layer 114 may be made of the same material as the ridge 102. Alternatively, the spacer layer 114 may be part of the ridge 102 and may be a residual layer that forms a single structure with the ridge 102.

Fig. 1B illustrates a top view of a semiconductor laser 100 according to an embodiment of the present disclosure. As shown in fig. 1B, the ridge 102 extends from one edge of the semiconductor laser 100 to the opposite edge of the semiconductor laser 100.

Fig. 1C illustrates a three-dimensional cross-sectional view of a semiconductor laser 100 according to an embodiment of the present disclosure. As shown in fig. 1C, light 108 is emitted from the waveguide 104 at the end facet of the semiconductor laser 100. The light 108 has a horizontal far-field component 110 and a vertical far-field component 112. Because of the asymmetric geometry of the end face where the light exits the waveguide 104, the light 108 may diverge in different directions and/or at different angles, and the component 110 and the component 112 may have different dimensions. In practice, the vertical far field may diverge faster than the horizontal far field, and the full width at half maximum value of the horizontal far field may be much narrower than the vertical far field. Thus, as shown in fig. 1C, the size of the vertical far-field component 112 may be greater than the size of the horizontal far-field component 110. This difference in the size of components 110 and 112 may result in light 108 having an asymmetric far-field pattern. When coupling the light 108 to a transmission medium, such as an optical fiber, the asymmetric far-field pattern may cause astigmatism because the virtual focal points of the horizontal far-field component 110 and the vertical far-field component 112 may be at different positions. Such astigmatism may reduce the coupling efficiency with the transmission medium and the coupling loss may increase. It may be necessary to use complex aspheric optical elements (such as lenses) to correct the asymmetry and ensure that coupling losses are reduced. However, these optical elements can be expensive and can increase the cost of manufacturing and using the semiconductor laser.

Fig. 2A shows a simulated thermal map 200 of light 108 in accordance with an embodiment of the present disclosure. The heat map 200 indicates, on its left-hand y-axis, the vertical angle of the vertical far-field component 112. The horizontal angle of the horizontal far-field component 110 is included on the x-axis of the thermal map 200. The normalized intensity of light 108, expressed in arbitrary units (a.u.), is included on the y-axis on the right hand side of the thermal map 200. As shown in heat map 200, the vertical angle of vertical far-field component 112 spans a larger angular range than the horizontal angle of horizontal far-field component 110, with normalized intensity greater than zero. The greater span of vertical angles than horizontal angles reflects the asymmetry between the vertical far-field component 112 and the horizontal far-field component 110.

Fig. 2B illustrates a graph 202 that displays the data of the heat map 200 in a graphical format, in accordance with an embodiment of the present disclosure. As shown in graph 202, the horizontal angle of the horizontal far-field component 110 spans from about-40 degrees to about 40 degrees. However, a substantial portion of the emitted light is concentrated between about-15 degrees and about 15 degrees. The vertical far field component 112 spans from about-80 degrees to about 80 degrees in vertical angle, with a majority of the emitted light concentrated between about-25 degrees to about 25 degrees. Thus, the graph 202 further illustrates the asymmetry between the vertical far-field component 112 and the horizontal far-field component 110.

Fig. 3A illustrates a top view of a semiconductor laser 300 according to an embodiment of the present disclosure. The semiconductor laser 300 may be a ridge diode laser including a ridge 302. The semiconductor laser 300 may also include a waveguide and a substrate (not shown in fig. 3A). The semiconductor laser 300 may include a concavely curved end face 304. For example, a chemically assisted ion beam may be used to etch a concave curved end face 304 from the semiconductor laser 300. Other kinds of etching methods, such as reactive ion etching-inductively coupled plasma (RIE-ICP) etching or wet etching, may also or alternatively be used. The concavely curved end face 304 may have a concave shape with respect to an edge of the semiconductor laser 300 including the end face, as shown in a top view in fig. 3A. Alternatively, differently shaped end faces may be provided. For example, the curved end surface may be a convex curved end surface (as will be discussed with reference to fig. 8), or may be a curve of a different shape. For example, a stepped configuration may be used.

Of the semiconductor laser 300 whose concavely curved end face 304 may originate from the concavely curved end face 304The first position extends to a second position of the semiconductor laser 300 where the concavely curved end face 304 terminates. The distance between the first position and the second position is the width of the curved end face and is denoted by "w" in fig. 3A. The value "l" of fig. 3A represents the distance from the edge of the semiconductor laser 300 to the minimum depth of the concavely curved end face 304. The curve of the concavely curved end face 304 may extend into a circle 306 including a radius "r". The circle 306 is not an integral part of the semiconductor laser 300, but rather symbolizes the shape that would result if the curvature of the concavely curved end face 304 formed a portion of a circle. The values "w", "r" and "l" satisfy the equation (w/2)²+(r-1)²＝r²。

The curvature of the concavely curved end face 304 may be modified by adjusting the radius "r" of the circle 306. For example, by increasing the radius "r" and keeping "1" constant, the curvature of the concavely curved end face 304 may be decreased. Conversely, the curvature of the concavely curved end face 304 may be increased, for example, by decreasing the radius "r" and keeping "1" constant. Adjusting the radius "r" may also modify the horizontal far field angle of the light emitted from the semiconductor laser 300. By decreasing the radius "r" and keeping "1" constant, the horizontal far field angle can be increased.

Fig. 3B illustrates a three-dimensional cross-sectional view of a semiconductor laser 300 according to an embodiment of the present disclosure. As shown in fig. 3B, the semiconductor laser 300 includes a ridge 302, a waveguide 308, and a substrate 310. Fig. 3B also shows another view of the concavely curved end face 304. A spacer layer 318 may be positioned between the ridge 302 and the waveguide 308. The spacer layer 318 may be made of the same material as the ridges 302. Alternatively, the spacer layer 318 may be part of the ridge 302 and may be a residual layer that forms a single structure with the ridge 302.

As shown in fig. 3B, light 312 is emitted from the waveguide 308 at the end facet of the semiconductor laser 300. The light 312 has a horizontal far-field component 314 and a vertical far-field component 316. Similar to components 110 and 112 of light 108 discussed above, horizontal far-field component 314 and vertical far-field component 316 may diverge at different angles in different directions. However, the concavely curved end face 304 may reduce this asymmetry by correcting for divergence without requiring additional optical elements. Thus, the size of the vertical far-field component 316 may be closer to the size of the horizontal far-field component 314, and the light 312 emitted by the semiconductor laser 300 may be more symmetric than the light 108 emitted by the semiconductor 100. In fact, light 312 may have a more symmetric far-field pattern than light 108.

The improved far field pattern may reduce the amount of astigmatism present when coupling light 312 to a transmission medium, such as an optical fiber, as compared to the coupling of light 108. This reduction is because the virtual focus of the horizontal far-field component 314 and the virtual focus of the vertical far-field component 316 may be at closer positions. The reduction in astigmatism may increase the coupling efficiency with the transmission medium and may reduce coupling losses compared to the coupling of light 108. Complex aspheric optical elements (such as lenses) may not be required to couple light 308 to the transmission medium. Moreover, the cost of manufacturing and using the semiconductor laser 300 may be less than the cost of manufacturing and using the semiconductor laser 100. In addition, the end facet curvature may reduce the mode reflectivity, which may be desirable in semiconductor optical amplifier applications.

Fig. 3C illustrates an enlarged view of the concavely curved end face 304 and shows the ridge 302, the waveguide 308, and the substrate 310, in accordance with an embodiment of the present disclosure. Each layer of the semiconductor laser 300 may be etched to form a concavely curved end facet 304. Alternatively, however, only the waveguide 308 may be etched as curved alone, or the waveguide 308 together with one or more of the substrate 310 and the ridge 302 may be etched as curved.

Fig. 4A shows a simulated thermal map 400 of light 312 according to an embodiment of the present disclosure. The heat map 400 indicates, on its left-hand y-axis, the vertical angle of the vertical far-field component 316. The horizontal angle of the horizontal far-field component 314 is included on the x-axis of the thermal map 400. The normalized intensity of light 312, expressed in arbitrary units (a.u.), is included on the y-axis on the right-hand side of the thermal map 400.

As shown in the heat map 400, the vertical angle of the vertical far-field component 316 spans a larger angular range, in which the normalized intensity is greater than zero, than the horizontal angle of the horizontal far-field component 314. However, as compared to the heat map 200 in fig. 2A, the span of horizontal angles may be about the same or greater, while the span of vertical angles may not be greater or the same. Thus, the thermal map 400 illustrates that the concavely curved end face 304 of the semiconductor laser 300 may increase the horizontal far-field component and/or decrease the vertical far-field component of the emitted light. The thermal map 400 also shows an increase in the horizontal far field component of the emitted light, since the horizontal angle may be slightly larger. Because the span of angles more closely matches, an increase in the horizontal far-field component and/or a decrease in the vertical far-field component may reduce the asymmetry of the vertical and horizontal far-field components. In addition, the concavely curved end face 304 may improve the anti-reflection characteristics of the semiconductor laser 300.

Fig. 4B illustrates a graph 402, the graph 402 displaying data of the heat map 400 in a graphical format, in accordance with an embodiment of the present disclosure. As shown in graph 402, the horizontal far-field component 314 has a horizontal angular span from about-40 degrees to about 40 degrees. However, a large portion of the emitted light is concentrated between about-20 degrees and about 20 degrees, showing an increase compared to the graph 202 in fig. 2B. For example, the vertical angle of the vertical far-field component 316 may be considered to span from about-60 degrees to about 60 degrees, or may be considered to span from about-80 degrees to about 80 degrees. Accordingly, the vertical angular span of the semiconductor 300 may therefore be considered to be reduced or substantially unchanged from that of the semiconductor laser 100 shown in fig. 2B. Thus, the results of graph 402 and thermal map 400 may show a reduction in asymmetry of vertical and/or horizontal far field components of light emitted by semiconductor laser 300 as compared to light emitted by semiconductor laser 100. The results may further demonstrate that the concave curved end face 304 increases the full width at half maximum value of the horizontal far field component of the light emitted from the waveguide 308.

Fig. 4C and 4D show examples of how the antireflection characteristic can be improved according to the laser end face. As shown in fig. 4C, a semiconductor laser 404 is shown. The semiconductor laser 404 may be the semiconductor laser 100 shown in fig. 1A to 1C. Light 406 passes through the semiconductor laser 404 and strikes an end face 408, which is a non-curved end face. So that the reflected light 410 may travel in a direction parallel to the light 406. Since reflected light 410 may be parallel to light 406, there may be high mode reflectivity in laser 404 and the efficiency of the light exiting laser 404 may be reduced.

Fig. 4D shows a semiconductor laser 412. The semiconductor laser 412 may be the semiconductor laser 300 shown in fig. 3A-3C. The light 406 passes through the semiconductor laser 404 and hits the concavely curved end face 416. So that reflected light 418 may travel in a direction that is not parallel to light 406. Since reflected light 418 may not be parallel to light 406, the mode reflectivity of laser 412 may be reduced and the efficiency of the light exiting laser 412 may be increased.

Fig. 5A illustrates a graph 500 showing different spans of horizontal angles of horizontal far field components of light emitted from the waveguide 308 via the concave curved end face 304 when the radius "r" changes and "1" remains constant, according to one embodiment of the present disclosure. As shown in the graph with a radius of 14 μm, the angular span is from about-50 degrees to about 50 degrees. The angular span is from about-40 degrees to about 40 degrees for an 18 μm radius. Accordingly, the curvature of the concavely curved end face 304 may be modified to adjust the horizontal angle of the horizontal far-field component of the light emitted from the waveguide 308.

Fig. 5B shows an enlarged portion 502 of the graph 500 shown in fig. 5A. As shown in fig. 5B, a concave curved end face with a radius of 18 μm results in a smaller horizontal angular span relative to a concave curved end face with a radius of 14 μm.

Fig. 6A-6C illustrate experimental results obtained by testing a reference semiconductor laser (e.g., semiconductor laser 100) and a semiconductor laser having varying edge facet curvature (e.g., semiconductor laser 300), according to an embodiment of the present disclosure. The resulting plot shows the horizontal far field pattern of the different lasers and how wide the output laser beam diverges as it exits the different lasers. These figures also show how wide the angle of available light intensity is within half the intensity of each figure. The x-axis is the angle in the horizontal direction. The y-axis is power intensity in arbitrary units (a.u.).

Fig. 6A shows the horizontal angle of the horizontal far-field component of the emitted light emitted by the reference semiconductor laser having no end face curvature. This laser showed a full width at half maximum value of the horizontal far field of 16.8 degrees.

Fig. 6B shows the horizontal angle of the horizontal far-field component of the emitted light emitted by the 14 μm concave end-face curvature semiconductor laser. This laser showed a full width at half maximum value of the horizontal far field of 29.2 degrees.

Fig. 6C shows the horizontal angle of the horizontal far-field component of the emitted light emitted by the 18 μm concave end-face curvature semiconductor laser. This laser showed a full width at half maximum value of the horizontal far field of 25.6 degrees.

Thus, the results shown in fig. 6A to 6C can show that the semiconductor laser with a curved end face provides a wider horizontal far-field laser output than the reference semiconductor laser without end face curvature. Therefore, the curved end face semiconductor laser exhibits better performance than the reference semiconductor laser having no end face curvature. Experimental results also show that the horizontal far field changes as the curvature of the concavely curved end face 304 changes, and that the far field magnitude can be adjusted based on the changing radius of curvature "r".

Fig. 7 shows a graph 700 reflecting the ratio of the output optical power of a semiconductor laser in milliwatts (mW) to the current in milliamps (mA) according to an embodiment of the present disclosure. The semiconductor laser performance of the curved end face shown by the dotted line is compared with the semiconductor performance of the non-curved end face shown by the solid line. As shown in the graph 700, the output optical power of a semiconductor laser (e.g., the semiconductor laser 300) having a curved end face does not significantly differ from the output optical power of a semiconductor laser (e.g., the semiconductor laser 100) not having a curved end face, and the output optical power of a semiconductor laser (e.g., the semiconductor laser 300) having a curved end face is within a tolerance range. Thus, the facet curvature has no significant effect on semiconductor laser performance, such as, for example, semiconductor laser output optical power performance.

Fig. 8 illustrates a top view of a semiconductor laser 800 according to an embodiment of the present disclosure. The semiconductor laser 800 may be a ridge diode laser including a ridge 802. The semiconductor laser 800 may also include a waveguide and a substrate (not shown in fig. 8). The ridges 802 may be the same as the ridges 302 described above. The waveguide and substrate of the semiconductor laser 800 may be, for example, the same as the waveguide 308 and substrate 310 described above.

The semiconductor laser 800 may include a convexly curved endface 804. The convexly curved end face 804 may be formed, for example, by etching the semiconductor laser 800 using chemically assisted ion beam etching. The convex curved facet 804 has a convex shape with respect to the edge of the semiconductor laser 800 including the facet, as shown in the top view in fig. 8. Alternatively, the curved end surface may be a curve of a different shape.

The convex curved end face 804 may extend from a first location of the semiconductor laser 300 where the convex curved end face 804 begins to a second location of the semiconductor laser 300 where the convex curved end face 804 ends. The distance between the first position and the second position is the width of the curved end face and is denoted by "w" in fig. 8. The value of "1" of fig. 8 represents the distance from the minimum convex depth of the curved facet 804 to the edge of the semiconductor laser 800 that has been etched. The curve of the convexly curved end face 804 may extend into a circle 806 that includes a radius "r". The circle 806 is not an integral part of the semiconductor laser 800, but rather symbolizes the shape that would result if the curvature of the convexly curved end face 804 formed a portion of a circle. The values "w", "r" and "l" satisfy the equation (w/2)²+(r-1)²＝r²。

By adjusting the radius "r" of the circle 806, the curvature of the convexly curved end face 804 may be modified. For example, by increasing the radius "r" and keeping "1" constant, the curvature of the convexly curved end face 804 may be reduced. Conversely, the curvature of the convexly curved end face 804 may be increased, for example, by decreasing the radius "r" and keeping "1" constant. Adjusting the radius "r" may also modify the horizontal far field angle of the light emitted from the semiconductor laser 800.

Referring back to fig. 4C, in another embodiment, an optically transparent material may be deposited or otherwise placed in front of the end face 408 of the laser 404 in fig. 4C to modify how the light exits the laser 404 and improve the functionality of the laser 404. For example, the optically transparent material may be a high refractive index optically transparent material. The material may, for example, be shaped or etched in the same manner as the end face 408 as shown in fig. 4C (e.g., such that it forms a non-curved end face similar to the end face 408). In another embodiment, the material may be shaped or etched (e.g., formed into a concavely curved end face similar to end face 416), for example, in the same manner as end face 416 as shown in FIG. 4D. In another embodiment, the material may be shaped or etched, for example, in the same form as the endface 804 as shown in FIG. 8 (e.g., such that it forms a convexly curved endface similar to the endface 804).

The scope of the present disclosure is not limited by the specific embodiments described herein. Indeed, various other embodiments and modifications of the disclosure in addition to those described herein will be apparent to those skilled in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Moreover, although the present disclosure has been described herein in the context of at least one particular implementation in at least one particular environment for at least one particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes.