JP2006066538A - Surface-emitting laser light source and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a surface-emitting laser light source, with which a laser light can be obtained under optional outgoing conditions, and to provide the surface-emitting laser light source. <P>SOLUTION: The surface-emitting laser light source 2 is comprised of a surface-emitting laser element 3 having a columnar mesa shape and a microlens 4, which are made integral with each other and are formed on a substrate 10. The surface-emitting laser element 3 is a vertical resonator type surface-emitting laser (VCSEL), and a resonator is formed between the lower mirror 5 and the upper mirror 8. The microlens 4 comprises a first lens 4a and a second lens 4b, and it is formed as to have a distributed refractive index structure where the refractive index changes under a specified distribution from the central part on the side of an outgoing surface 3a toward a lens surface 4c on the outside. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a surface emitting laser light source and a surface emitting laser light source.

A vertical cavity surface emitting laser element having a structure that emits laser light perpendicular to the substrate surface can be integrated with other elements at high density on the substrate. The emission angle of the surface emitting laser element is usually 6 to 7 degrees (during single mode), which is narrower than that of the edge emitting laser element (about 30 degrees). Therefore, it is expected to be used in the future as a light source of an optical integrated circuit. Various studies have been made on the laser light emission conditions of the surface emitting laser element (see, for example, Patent Documents 1 to 3).
JP 2001-284725 A JP 2002-26452 A JP 2001-242303 A

  As described above, the surface emitting laser element can obtain laser light having a narrower emission angle than the edge emitting laser element. However, in the case of application to optical interconnection in a state where elements such as surface emitting laser elements are highly integrated, it is necessary to further reduce the light emission angle from the surface emitting laser elements. On the other hand, in the above document, a combination of a surface emitting laser element and a microlens is studied.

  In Patent Document 1, a resin is ejected by a nozzle above the laser emitting portion, and the resin is solidified so as to have a convex lens shape, thereby forming a microlens. However, since the diameter of the laser emission part is several μm, it is difficult to align the position where the resin is ejected by the nozzle, and it is also difficult to form a microlens having a diameter of several μm. Further, considering that the surface emitting laser light sources are integrated with high density, this method in which resin is formed by nozzles one by one is not suitable for mass production. In Patent Document 2, a microlens made of a dielectric is applied to a surface emitting laser light source. However, specific lens structures and lens manufacturing methods have not been fully studied.

  On the other hand, in Patent Document 3, quartz glass is melted by heat to form a microlens. However, since the melting temperature of quartz glass is 1000 ° C. or higher, the semiconductor substrate is thermally damaged and cannot be applied to a surface emitting laser light source.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a surface emitting laser light source manufacturing method and a surface emitting laser light source capable of obtaining laser light under desired emission conditions.

  In order to solve such an object, a method of manufacturing a surface emitting laser light source according to the present invention includes laminating a first dielectric material on an emission surface of a vertical cavity surface emitting laser element formed on a substrate. A first dielectric laminating step, a first lens forming step of forming a first dielectric material laminated on the emission surface on the original lens, and a second dielectric material laminated on the original lens A second dielectric laminating step, a laser beam is emitted from the surface emitting laser element, and an outer surface shape of the second dielectric material laminated on the original lens is adjusted based on the emission pattern to obtain a surface And a second lens forming step of forming a microlens corresponding to the light emitting laser element.

  According to this manufacturing method, the microlens is formed on the emission surface of the surface emitting laser element. Therefore, the emission angle of the laser light emitted from the surface emitting laser light source can be reduced, and further, collimated light can be obtained as necessary. In addition, the microlens is subjected to a two-stage formation process in which an original lens is first formed and then a second dielectric material is laminated thereon. In such a method, the outer surface shape of the finally obtained microlens, the distributed refractive index structure in the lens, and the like can be variously controlled. Furthermore, after the laser beam is emitted once and the emission pattern is confirmed, the shape of the microlens is adjusted. Therefore, in order to obtain a desired emission condition, the shape of the microlens can be controlled with high accuracy. In addition, since a complicated adjustment for alignment is not required, the lens can be easily formed.

  In the second dielectric layer stacking step, it is preferable to stack the second dielectric material by providing a stepwise difference in refractive index from the refractive index of the original lens. In such a configuration, reflected light to the inside of the surface emitting laser element can be obtained with an amount of reflection corresponding to the difference in refractive index at the interface between the first and second dielectric materials. Therefore, by adjusting the refractive index difference, the amount of reflection of the microlens into the surface emitting laser element can be set to a desired value, and the mode can be controlled.

  In the second dielectric layer stacking step, it is preferable to stack the second dielectric material so that the refractive index changes from the original lens side toward the outside. Thereby, it is possible to obtain a microlens having a distributed refractive index structure adapted to a desired emission condition.

  In the second dielectric layer stacking step, it is preferable to stack the second dielectric material so that the refractive index continuously changes from the original lens side toward the outside. By changing the refractive index in this way, light at each angle emitted from the surface emitting laser light source can be gradually refracted in a desired direction, and the optical path length difference can be reduced. Thereby, the aberration of the light emitted from the surface emitting laser light source can be reduced.

  In the second dielectric layer stacking step, it is preferable to stack the second dielectric material so that the refractive index changes stepwise from the original lens side toward the outside. At the interface where the refractive index changes stepwise, it is possible to obtain reflected light into the surface emitting laser element with a reflection amount corresponding to the difference in refractive index before and after the interface. By adjusting the number of interfaces and the refractive index difference at the interfaces, the amount of reflection of the microlenses into the surface-emitting laser element can be set to a desired value, and the mode can be controlled.

In the second dielectric layer stacking step, the second dielectric material is preferably stacked by a plasma CVD method. In the plasma CVD method, particularly in the case of SiN film formation, the refractive index is 2.5 around 350 ° C., but when the film formation temperature is lowered, H (hydrogen) is mixed and the refractive index is lowered. Therefore, it is possible to change the refractive index distribution in the thickness direction by changing the temperature at the time of lamination. In addition, in SiO ₂ , the refractive index can be changed by doping Ge, P, B or the like. Even in other materials, the microlens can be formed by changing the refractive index of the laminated dielectric by changing each film forming condition.

  In the second lens forming step, it is preferable to adjust the outer surface shape of the microlens by a reactive ion etching method or a sputtering method. Thereby, the curved surface of the lens surface of the microlens can be adjusted.

  A surface-emitting laser light source according to the present invention includes a vertical cavity surface-emitting laser element formed on a substrate and a microlens formed on an emission surface of the surface-emitting laser element. And is formed in a distributed refractive index structure in which the refractive index changes with a predetermined distribution from the central portion on the exit surface side toward the outer lens surface.

  According to this surface emitting laser light source, the microlens is formed on the emission surface of the surface emitting laser element. Therefore, the emission angle of the laser light emitted from the surface emitting laser light source can be reduced, and further, collimated light can be obtained as necessary. Further, since the microlens has a distributed refractive index structure that changes its refractive index, it is possible to variously control the emission conditions of the laser light emitted from the surface emitting laser light source. Further, since the microlens is formed on the emission surface of the surface emitting laser element, complicated adjustment for alignment is not required to align the microlens. The exit surface of the surface emitting laser element may be the surface opposite to the substrate or the surface on the substrate side.

  As a specific distributed refractive index structure, the microlens includes an inner first lens portion including a central portion and an outer second lens portion including a lens surface, and includes a first lens portion and a second lens portion. It is preferable that the refractive index changes step by step. At the interface between the first lens unit and the second lens unit and the surface of the second lens unit, reflected light to the inside of the surface emitting laser element can be obtained with a reflection amount corresponding to the refractive index difference. Therefore, the mode can be controlled by adjusting the refractive index difference so that the reflection amount of the microlens into the surface emitting laser element becomes a desired value.

  The microlens includes an inner first lens portion including a center portion and an outer second lens portion including a lens surface, and the second lens portion is refracted from the first lens portion side toward the lens surface side. It is preferred that the rate changes. Thereby, it is possible to control to a desired emission condition in combination with the first lens unit.

  In this case, it is preferable that the change in the refractive index from the first lens unit side to the lens surface side in the second lens unit is continuous. By changing the refractive index in this way, light at each angle emitted from the surface emitting laser light source can be gradually refracted in a desired direction, and the optical path length difference can be reduced. Thereby, the aberration of the light emitted from the surface emitting laser light source can be reduced.

  Furthermore, it is preferable that the change of the refractive index from the first lens unit side to the lens surface side in the second lens unit is stepwise. In such a configuration, at the interface where the refractive index in the second lens portion changes stepwise, reflected light to the inside of the surface emitting laser element can be obtained with a reflection amount according to the refractive index difference before and after the interface. . By adjusting the number of interfaces and the refractive index difference at the interfaces, the amount of reflection of the microlenses into the surface-emitting laser element can be set to a desired value, and the mode can be controlled.

  In the surface emitting laser light source, a plurality of surface emitting laser elements and corresponding microlenses may be formed on a substrate in a one-dimensional or two-dimensional array. In the surface emitting laser light source described above, since the emission angle of the laser light can be suppressed, it is possible to form an array with high density.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and surface emitting laser light source of a surface emitting laser light source which can obtain a laser beam on desired emission conditions can be provided.

  Hereinafter, a manufacturing method of a surface emitting laser light source and a first embodiment of a surface emitting laser light source according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. The dimensional ratios in the drawings do not necessarily match those described.

  FIG. 1 is a perspective view of a surface emitting laser array 1 which is a surface emitting laser light source according to the present embodiment. The surface-emitting laser array 1 includes a plurality of surface-emitting laser light sources 2 arranged in a two-dimensional array at regular intervals on the same surface of the substrate 10.

  FIG. 2 is a perspective view of the surface emitting laser light source 2 according to the present embodiment, and FIG. 3 is a vertical sectional view of the surface emitting laser light source 2.

  As shown in FIG. 2, the surface emitting laser light source 2 is configured by integrally forming a surface emitting laser element 3 having a cylindrical mesa shape and a microlens 4 on a substrate 10. The surface emitting laser element 3 is a vertical cavity surface emitting laser (VCSEL) and is formed by laminating a lower mirror 5, an active layer 6, an oxide current confinement layer 7, and an upper mirror 8. A resonator is formed with the upper mirror 8. Therefore, as indicated by the arrows in FIG. 2, laser light is emitted in a direction parallel to the stacking direction of these layers.

  The microlens 4 has a convex lens shape, and is integrally formed with the surface emitting laser element 3 on the emission surface 3 a which is the surface opposite to the substrate 10 of the surface emitting laser element 3. In addition, the microlens 4 is formed in a distributed refractive index structure in which the refractive index changes with a predetermined distribution from the central portion on the exit surface 3a side toward the outer lens surface 4c.

  Specifically, the microlens 4 is made of SiN, which is a dielectric, and has a center point (center portion) C that is a point on the surface on the emission surface 3a side and intersecting the optical axis, as shown in FIG. The inner first lens portion 4a includes the outer lens portion 4b including the lens surface 4c which is the outer surface of the microlens 4. In the first lens unit 4a, the refractive index is uniformly distributed with a constant value. In the second lens portion 4b, the refractive index is distributed so as to continuously decrease radially from the first lens portion 4a side toward the lens surface 4c side.

  Next, effects of the surface emitting laser array 1 and the surface emitting laser light source 2 will be described. The laser light emitted from the surface emitting laser element 3 is refracted by the microlens 4 and the emission angle becomes small. Therefore, laser light with a narrowed emission angle or collimated laser light can be obtained as necessary. Therefore, when the surface-emitting laser array 1 or the surface-emitting laser light source 2 is applied to optical interconnection, it is possible to increase its integration and to suppress crosstalk between channels. The microlens 4 has a distributed refractive index structure in which the refractive index is distributed from the center point C toward the lens surface 4c. In such a configuration, the laser light emission conditions can be variously controlled by changing the specific distribution structure of the refractive index. The microlens 4 is formed on the emission surface 3 a of the surface emitting laser element 3. Therefore, it is possible to align the microlens 4 without complicated adjustment for alignment.

  The distributed refractive index structure of the microlens 4 can take various structures. For example, the second lens unit 4b has a structure in which the refractive index changes from the first lens unit 4a side to the lens surface 4c side, thereby controlling to a desired emission condition in combination with the first lens unit 4a. Is possible.

  Specifically, in the distributed refractive index structure of the microlens 4 in the present embodiment, the refractive index is uniformly distributed at a constant value in the first lens portion 4a, and the refractive index is the first in the second lens portion 4b. It is a structure that changes so as to continuously decrease from the lens portion 4a side toward the lens surface 4c side. Therefore, as shown in the optical path diagram of FIG. 3, the emitted laser light at each angle is gradually refracted in the vertical direction (upward direction), and the optical path length difference between these lights is reduced. As a result, aberrations when the laser light emitted from the surface emitting laser light source 2 is condensed are reduced. As a result, when applied to devices such as high-speed optical parallel processing circuits using femtosecond pulse waves, the dispersion caused by aberrations is reduced, and it is possible to realize optical systems necessary for high-speed processing such as femtosecond pulse optical computers. Become.

  The distributed refractive index structure of the microlens 4 is not limited to the above example. For example, a configuration in which the refractive index changes stepwise between the first lens unit 4a and the second lens unit 4b may be employed. Thus, when the refractive index is changed stepwise, a part of the light is reflected at the interface between the first lens portion 4a and the second lens portion 4b as shown in FIG. 3 is returned to the inside. Since the reflectance depends on the difference in refractive index, it is possible to control the mode by adjusting the difference in refractive index so as to obtain a desired amount of reflection. In this case, the refractive index in the second lens portion 4b may be continuously changed as described above, or may be constant. Further, the distribution may be such that the refractive index continuously changes from the center point C toward the interface with the second lens portion 4b in the first lens portion 4a. Or it is good also as distribution which a refractive index changes in steps within the 1st lens part 4a. Furthermore, these distributions can be combined. As a result, an outgoing laser beam that satisfies a desired emission condition can be obtained.

  Further, as described above, since the surface emitting laser light source 2 has a reduced emission angle and reduced aberrations, the surface emitting laser array 1 in which the surface emitting laser light sources 2 are arranged at high density is possible. Furthermore, when a large-scale high-power array having a high-density arrangement is realized, high-density light collection is possible. In the surface emitting laser array 1, the arrangement of the surface emitting laser light sources 2 is not limited to the two-dimensional array described above, and may be one-dimensional or two-dimensional array. Further, the surface-emitting laser array 1 may have any number of surface-emitting laser light sources 2, and when only one is provided, it becomes a single surface-emitting laser light source instead of an array.

  The surface emitting laser element 3 is not limited to the mesa type, but may be a buried type or a planar type. The dielectric material forming the microlens is not limited to SiN.

  Next, with reference to FIGS. 5 and 6, a method for manufacturing the surface emitting laser light source 2 according to the present embodiment will be described.

  Here, in the manufacturing method of the surface emitting laser light source 2 in the present embodiment, the microlens is formed by the laminated dielectric. In particular, in forming the microlens, it is preferable to combine the respective characteristics of the plasma CVD method, the reactive ion etching method, the plasma etching method, and the sputtering method. Thereby, it is possible to freely adjust the lens curved surface of the microlens mounted on the surface emitting laser element 3. In the plasma CVD method, since there is no directionality with respect to lamination, the laminate is laminated with a uniform thickness. In addition, since the plasma etching method has no directionality with respect to etching, it is etched with a uniform thickness with respect to the surface of the object to be etched. In addition, since the sputtering method is perpendicular to the stacking, the stack is stacked on the curved surface while maintaining the curvature of the curved surface. In addition, since the reactive ion etching method is perpendicular to etching, the curved surface is etched while maintaining the curvature.

  When SiN is laminated by plasma CVD, the refractive index of the laminate changes by changing the temperature during lamination. By taking advantage of this, it is possible to make the laminate a distributed refractive index structure in which the refractive index changes stepwise or continuously. Thereby, not only mode control of the emitted laser beam and emission pattern (emission angle) control but also aberration reduction can be achieved.

  The manufacturing method of the surface emitting laser light source 2 according to the present embodiment includes a first dielectric layer stacking step, a first lens forming step, a second dielectric layer stacking step, and a second lens forming step. Here, SiN is used as an example of a dielectric to be stacked.

  FIG. 5A is a process sectional view showing a first dielectric layer stacking process.

  As shown in FIG. 5A, first, SiN which is the first dielectric material is laminated on the emission surface 3a of the surface emitting laser element 3 formed on the substrate 10 by, for example, plasma CVD. Then, the first SiN film 11 is formed. The refractive index of the first SiN film 11 differs depending on the temperature at which the first dielectric material SiN is laminated. For example, when the first SiN film 11 is laminated at 350 ° C., the refractive index of the first SiN film 11 is 2.5.

  FIG. 5B to FIG. 5F are diagrams for explaining the first lens forming step.

  As shown in FIG. 5B, first, a resist material (for example, S1818, manufactured by Shipley) is applied on the first SiN film 11 laminated in the first dielectric laminating step to form a resist film 12. To do. The resist material is applied, for example, by spin coating (rotation speed: 7000 rpm, processing time: 40 seconds).

  Next, as shown in FIG. 5C, the resist film 12 is shaped according to the mask pattern by performing exposure and development. The mask pattern is formed so that the resist film 12 remains on the emission surface 3 a of the surface emitting laser element 3.

  Subsequently, as shown in FIG. 5D, the remaining resist film 12 is formed into a spherical shape by post-baking. Post bake is performed for 1 minute, for example at the temperature of 200 degreeC.

Thereafter, as shown in FIG. 5E, the resist film 12 and the first SiN film 11 are etched by a plasma etching method to form the original lens 13 having a spherical shape, that is, a convex lens shape. The gas used for the plasma etching method is, for example, tetrafluorocarbon (CF ₄ ) and oxygen (O ₂ ). In this method, since the surface of the original lens 13 is etched with a uniform thickness, the size and curvature of the original lens 13 can be adjusted by the etching time. That is, if the etching time is lengthened, the original lens 13 becomes smaller and its curvature becomes larger. On the other hand, if the etching time is shortened, the original lens 13 becomes larger and its curvature becomes smaller.

  Thereafter, if necessary, adjustment is performed so that the height of the original lens 13 formed on the substrate 10 is constant. FIG. 5F shows a state in which the original lens 13 is adjusted to be high. When the height of the original lens 13 is lowered, a reactive ion etching method can be applied. In the reactive ion etching method, etching is performed while maintaining the curvature of the original lens 13. On the other hand, when the height of the original lens 13 is increased, a sputtering method is applied. In the sputtering method, the original lens 13 is laminated while maintaining the curvature.

  Thus, the spherical original lens 13 is formed.

  FIG. 6A is a process sectional view showing a second dielectric laminating process.

  As shown in FIG. 6A, SiN as the second dielectric material is stacked on the original lens 13 by plasma CVD to form a second SiN film 14. The refractive index of the second SiN film 14 depends on the temperature (deposition temperature) at the time of stacking. For example, the second dielectric material is continuously changed from the temperature of 350 ° C. at which the first dielectric material is laminated and lowered to 250 ° C., so that the refractive index of the second SiN film 14 is changed to the original lens 13. From the refractive index of 2.5, the refractive index of the second SiN film 14 surface 14a continuously changes to 2.0. Further, the second dielectric material may be laminated at a temperature stepwise different from the temperature at which the first dielectric material is laminated. Or the temperature change at the time of lamination | stacking in a 2nd dielectric material lamination process may be stepwise instead of continuous. Or you may make the temperature at the time of lamination | stacking constant.

  FIG. 6B shows a second lens forming process.

  After the laser light is emitted from the surface emitting laser element 3 and the emission pattern is confirmed, the outer surface shape of the microlens 15 is adjusted so as to satisfy a desired emission condition (for example, collimated light or single mode maximization). To do. For the adjustment of the outer surface shape, a reactive ion etching method or a sputtering method is used. As shown in FIG. 6B, the microlens 15 is composed of an original lens 13 and a second SiN film 14. The microlens 15 includes a first lens portion and a second lens portion, and the original lens 13 is an inner first lens (4a in FIG. 3) including the center point C of the microlens 15, and a second SiN. The film 14 becomes the outer second lens portion (4b in FIG. 3) including the lens surface.

  FIG. 6C is a diagram illustrating a process of removing a portion unnecessary for forming the microlens 15. Specifically, a resist material is applied to the substrate 10 and patterned, and then etching is performed to remove a portion that is not necessary for forming the microlens 15. This step is incorporated as necessary and can be omitted.

  Next, effects of the method for manufacturing the surface emitting laser array and the surface emitting laser light source according to the present embodiment will be described. According to this manufacturing method, since the microlens 15 is formed on the emission surface 3a of the surface emitting laser element 3, the emission angle of the laser beam emitted from the manufactured surface emitting laser light source 2 can be reduced. . Therefore, laser light with a narrowed emission angle or collimated laser light can be obtained as necessary. This also makes it possible to suppress crosstalk when the surface emitting laser array 1 or the surface emitting laser light source 2 is applied to optical interconnection.

  The microlens 15 undergoes a two-stage formation process in which the original lens 13 is first formed and the second dielectric material is laminated thereon. Therefore, it is possible to variously control the outer surface shape of the microlens finally obtained, the distributed refractive index structure in the lens, and the like.

  Further, after the laser beam is once emitted and the emission pattern is confirmed, the outer surface shape of the microlens 15 is adjusted. Therefore, it is possible to control the lens shape with high accuracy in order to obtain a laser beam according to a desired emission condition. For example, the collimated light can be obtained by adjusting the outer surface shape of the microlens 15. Alternatively, the shape of the upper surface of the microlens 15 functioning as a concave mirror can be adjusted to control the light returning to the inside of the surface emitting laser element 3 to maximize the single mode output. In particular, it is possible to adjust the curved surface of the upper surface (lens surface) of the microlens 15 according to a desired emission condition by adjusting using an ion etching method or a sputtering method.

  Furthermore, once the mask used in the first lens forming step is manufactured, the microlenses 15 can be formed in a large amount in a lump without taking time for alignment. Therefore, in the surface emitting laser light source 2 using the oxide film current confinement structure, the shape of a lens having a diameter of several μm aligned on the active layer in the order of μm can be controlled, and a single mode output can be obtained. It becomes possible. In particular, in the manufacture of the surface emitting laser array 1, since the microlenses 15 can be formed in a large amount at a time, it can be manufactured at low cost.

  In the second dielectric laminating step, the second dielectric material can be laminated so that the refractive index changes radially from the original lens 13 side toward the outside (lens surface side). Thereby, the microlens 4 can have a distributed refractive index structure adapted to a desired emission condition.

  For example, the second dielectric material can be laminated so that the radial change in refractive index in the second dielectric lamination step is continuous. This makes it possible to gradually refract the light at each angle emitted from the surface emitting laser element 3 in a desired direction. Specifically, by laminating so that the refractive index decreases radially toward the lens surface, the optical path length between the laser beams of each angle emitted from the surface-emitting laser element 3 on the outer side from the original lens 13. The difference is reduced. As a result, the aberration at the time of condensing the laser light emitted from the surface emitting laser light source 2 is reduced, so that an array in which the surface emitting laser light sources 2 are arranged at high density becomes possible.

  Alternatively, the second dielectric material can be laminated so that the radial change of the refractive index in the second dielectric lamination step becomes stepwise. In such a configuration, reflected light to the inside of the surface emitting laser element can be obtained at the interface where the refractive index in the second SiN film 14 changes stepwise. The amount of reflection is an amount corresponding to the difference in refractive index before and after the interface. By adjusting the number of interfaces and the refractive index difference at the interfaces, the amount of reflection of the microlenses into the surface-emitting laser element can be set to a desired value, and the mode can be controlled.

  In particular, when the second dielectric material is laminated by plasma CVD, the second dielectric material can be laminated with the refractive index changed by changing the temperature at the time of lamination. it can. For example, when the temperature is continuously changed, the refractive index is continuously changed to be laminated. Further, by stacking the second dielectric material at a temperature stepwise different from the temperature at which the first dielectric material is stacked, a step is performed at the interface between the original lens 13 and the second dielectric material. A refractive index difference is provided. At this interface, light is reflected and returned to the inside of the surface emitting laser element 3 with a reflection amount corresponding to the difference in refractive index. Therefore, by adjusting the refractive index difference at the interface, the amount of reflection of the microlens 15 into the surface emitting laser element 3 can be set to a desired value, and mode control can be performed. Alternatively, in the lamination of the second dielectric material, the refractive index of the second dielectric material can be changed stepwise by changing the temperature stepwise. Alternatively, the refractive index can be uniformly distributed at a constant value in the second SiN film 14 by keeping the temperature at the time of lamination constant.

  In the second lens forming step, the outer surface shape of the microlens is adjusted by a reactive ion etching method or a sputtering method. Thereby, the curved surface of the lens surface of the microlens is adjusted.

  In the first dielectric laminating step, the film forming method is not limited to the plasma CVD method, and may be a sputtering method, a vapor deposition method, or the like.

  Here, regarding the microlens 15 manufactured by the manufacturing method of the present embodiment, FIG. 7 shows a cross-sectional shape measured by an atomic force microscope (AFM), and FIG. 8 shows a photograph by an optical microscope. The measurement by AFM includes the cross-sectional shape of the original lens formed through the first lens formation step (b in FIG. 7) and the cross-sectional shape of the microlens after the second lens formation step (a in FIG. 7). And went about. The horizontal axis of the graph in FIG. 7 represents the position on the bottom of the cross section of the microlens, and the vertical axis represents the height of the microlens. From FIG. 7, it can be seen that the cross-sectional shape of the microlens has changed through the second dielectric laminating step and the second lens forming step.

  Next, a second embodiment of the surface emitting laser light source according to the present invention will be described in detail. FIG. 9 is a vertical sectional view of the surface emitting laser light source 20 according to the present embodiment. The surface emitting laser light source 20 is structurally different from the surface emitting laser light source 2 according to the first embodiment because the refractive index change in the second lens portion 4b of the surface emitting laser light source 2 according to the first embodiment is continuous. On the other hand, the refractive index change in the second lens portion 21b of the surface emitting laser light source 20 is gradual.

  The microlens 21 is made of SiN which is a dielectric, and includes an inner first lens portion 21a including a center point (center portion) C and a lens surface 21c which is an outer surface of the microlens 21, as shown in FIG. It is comprised with the outer 2nd lens part 21b. As shown in FIG. 9, the second lens portion 21b includes a first layer 21d, a second layer 21e, and a third layer 21f. These are formed in order of the first layer 21d, the second layer 21e, and the third layer 21f from the first lens portion 21a side toward the lens surface 21c side. In addition, the refractive index value is constant in the first lens portion 21a and in each of the first to third layers 21d, 21e, and 21f.

These layers have different refractive index values. Specifically, the refractive index changes in order from large to small to large to small from the first lens unit 21a to the third layer 21f of the second lens unit 21b. That is, when the refractive index of the first lens portion 21a is n _21a and the refractive indexes of the first to third layers 21d, 21e, and 21f of the second lens portion 21b are n _21d , n _21e , and n _21f , respectively, n _21a > n _21d , n _21d <n _21e , and n _21e > n _21f are satisfied.

  Next, the effect of the surface emitting laser light source 20 will be described. The laser light emitted from the surface emitting laser element 3 is refracted by the microlens 21 and the emission angle becomes small. Therefore, laser light with a narrowed emission angle or collimated laser light can be obtained as necessary. Therefore, when the surface emitting laser light source 20 is applied to optical interconnection, it is possible to increase its integration, suppress crosstalk between channels, and the like. The microlens 21 has a distributed refractive index structure. Therefore, the laser light emission conditions can be controlled in various ways by changing the specific distribution structure of the refractive index. The microlens 21 is formed on the emission surface 3 a of the surface emitting laser element 3. Therefore, it is possible to align the microlens 21 without performing complicated adjustment for alignment.

  The distributed refractive index structure of the microlens 21 in the present embodiment is a configuration in which the refractive index changes stepwise between the first lens portion 21a and the second lens portion 21b. Therefore, a part of the light is reflected at the interface between the first lens portion 21 a and the second lens portion 21 b and returned to the inside of the surface emitting laser element 3.

  Furthermore, the refractive index is uniformly distributed at a constant value in the first lens portion 21a, and the refractive index in the second lens portion 21b changes stepwise from the first lens portion 21a side toward the lens surface 21c side. Yes. Therefore, as shown in FIG. 9, in addition to the interface between the first lens portion 21a and the second lens portion 21b, part of the light is also present at the interfaces between the layers 21d, 21e, and 21f in the second lens portion 21b. The light is reflected and returned to the inside of the surface emitting laser element 3. Thus, since the surface emitting laser light source 21 has many interfaces whose refractive index changes stepwise, a high single mode property can be realized. Further, since the reflectance at each interface depends on the difference in refractive index before and after the interface, it is possible to control the mode by adjusting the difference in refractive index between the respective layers so as to obtain a desired amount of reflection.

  Note that the refractive index change in the second lens portion 21b is not limited to that according to the present embodiment. For example, the refractive index may be changed in order from small → large → small → large in order from the first lens unit 21a to the third layer 21f of the second lens unit 21b. Alternatively, a configuration that changes from large to large or small to small may be included. Further, the number of layers constituting the second lens portion 21b is not limited to three. Furthermore, the refractive index may continuously change in each layer.

  In this case, the distribution may be such that the refractive index continuously changes from the center point C toward the interface with the second lens portion 21b in the first lens portion 21a. Or it is good also as distribution in which a refractive index changes in steps in the 1st lens part 21a. Furthermore, the above-described distribution example of the first lens portion 21a and the distribution example of the second lens portion 21b can be combined. As a result, an outgoing laser beam that satisfies a desired emission condition can be obtained.

  As mentioned above, although preferred embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to the said embodiment. For example, in the above embodiment, the emission surface of the surface emitting laser element is the surface opposite to the substrate, but may be a surface on the substrate side.

  Further, in order to collectively form microlenses 15 that precisely control the angle of emitted light (such as collimated light), a fine design of a distributed refractive index structure that conforms to the structure of the surface emitting laser element 3 is calculated. In accordance with this, the curvature of the original lens 13, the refractive index distribution of the second dielectric material, and the outer surface shape of the microlens 15 can be obtained while confirming the emission angle.

  INDUSTRIAL APPLICABILITY The present invention can be used as a surface emitting laser light source manufacturing method and a surface emitting laser light source capable of obtaining laser light under desired emission conditions.

It is a perspective view which shows the structure of the surface emitting laser array of 1st Embodiment. It is a perspective view which shows the structure of the surface emitting laser light source of 1st Embodiment. It is a figure which shows a mode that the emitted light is refracted by the microlens of 1st Embodiment. It is a figure which shows a mode that outgoing light reflects in the microlens of 1st Embodiment, and returns to the inside of a surface emitting laser element. It is process sectional drawing which shows a 1st dielectric material lamination process and a 1st lens formation process. It is process sectional drawing which shows a 2nd dielectric material lamination process and a 2nd lens formation process. It is an AFM measurement result showing the cross-sectional shape of a micro lens. It is the photograph of the micro lens by an optical microscope. It is sectional drawing which shows the structure of the surface emitting laser light source of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Surface emitting laser array, 2, 20 ... Surface emitting laser light source, 3 ... Surface emitting laser element, 3a ... Output surface, 4, 21 ... Micro lens, 4a, 21a ... 1st lens part, 4b, 21b ... 2nd Lens portion, 4c, 21c ... lens surface, 5 ... lower mirror, 6 ... active layer, 7 ... oxide current confinement layer, 8 ... upper mirror, 10 ... substrate, 11 ... first SiN film, 12 ... resist film, 13 ... Original lens, 14 ... Second SiN film, 15 ... Micro lens, 21d ... First layer, 21e ... Second layer, 21f ... Third layer, C ... Center point of micro lens

Claims (13)

A first dielectric laminating step of laminating a first dielectric material on an emission surface of a vertical cavity surface emitting laser element formed on a substrate;
A first lens forming step of forming, on an original lens, the first dielectric material laminated on the emission surface;
A second dielectric laminating step of laminating a second dielectric material on the original lens;
Laser light is emitted from the surface emitting laser element, and the outer surface shape of the second dielectric material laminated on the original lens is adjusted based on the emission pattern to correspond to the surface emitting laser element. A second lens forming step for forming a microlens;
A method of manufacturing a surface emitting laser light source, comprising:   2. The second dielectric material stacking step, wherein the second dielectric material is stacked by providing a difference in refractive index stepwise from the refractive index of the original lens in the second dielectric layer stacking step. The manufacturing method of the surface emitting laser light source of description.   The second dielectric material is laminated so that a refractive index changes from the original lens side toward the outside in the second dielectric layering step. The manufacturing method of the surface emitting laser light source of description.   The second dielectric material is laminated so that the refractive index continuously changes from the original lens side toward the outside in the second dielectric layer stacking step. The manufacturing method of the surface emitting laser light source of description.   4. The second dielectric material stacking step, wherein the second dielectric material is stacked so that the refractive index changes stepwise from the original lens side toward the outside. The manufacturing method of the surface emitting laser light source of Claim 4.   6. The method of manufacturing a surface emitting laser light source according to claim 1, wherein in the second dielectric laminating step, the second dielectric material is laminated by a plasma CVD method. .   The surface emitting laser light source according to any one of claims 1 to 6, wherein in the second lens forming step, an outer surface shape of the microlens is adjusted by a reactive ion etching method or a sputtering method. Production method. A vertical cavity surface emitting laser element formed on a substrate;
A microlens formed on the emission surface of the surface emitting laser element,
The surface emitting laser is characterized in that the microlens is made of a dielectric and has a distributed refractive index structure in which a refractive index changes with a predetermined distribution from a central portion on the emission surface side toward an outer lens surface. light source.   The microlens includes an inner first lens portion including the central portion and an outer second lens portion including the lens surface, and is stepwise between the first lens portion and the second lens portion. The surface emitting laser light source according to claim 8, wherein the refractive index changes.   The microlens includes an inner first lens portion including the central portion and an outer second lens portion including the lens surface, and the second lens portion is located on the lens surface side from the first lens portion side. The surface emitting laser light source according to claim 8 or 9, wherein the refractive index changes toward the surface.   11. The surface emitting laser light source according to claim 10, wherein the change in the refractive index from the first lens portion side toward the lens surface side in the second lens portion is continuous.   12. The surface emitting laser light source according to claim 10, wherein a change in the refractive index from the first lens portion side toward the lens surface side in the second lens portion is stepwise. . The surface emitting laser light source according to any one of claims 8 to 12, wherein a plurality of the surface emitting laser elements and the corresponding microlenses are formed on the substrate in a one-dimensional or two-dimensional array.

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