JPH09191155A - Optical waveguide and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fetch light from an optical waveguide in the direction perpendicular to the waveguide while the optical coupling efficiency between the waveguide and an external optical system is improved. SOLUTION: The light enclosed to a waveguide 35 from a waveguide in a semiconductor laser section returns to an active layer 34 after the light is propagated through the active layer 34, reflected upward by a reflecting mirror R2 , and reflected by a mirror 38. The light reflected by a reflecting mirror R1 is partially reflected by a Bragg reflecting film 32 and form a resonator. The light transmitted through the reflecting film 32 passes through a substrate 30 while the light is diffused and is reflected by a reflecting mirror 39 on the rear parabolic surface 31 of the substrate 30 and further reflected after the light is made parallel to the direction perpendicular to the substrate 30. The reflected light passes through the substrate 30 and is outputted from the surface of the substrate 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide and a method for manufacturing the optical waveguide, and more particularly to an optical waveguide suitable for incorporation in an optical transmission module and a method for manufacturing the same.

[0002]

2. Description of the Related Art There is an application for extracting light propagating in an optical waveguide in a direction perpendicular to the optical waveguide. For example, if light can be extracted perpendicularly to a flat optical waveguide, not only the conventional one-dimensional array-like coupling such as coupling between a waveguide and an optical fiber, but also the substrate on which the waveguide is formed. The degree of freedom in the vertical direction is increased, and the two-dimensional array-like coupling with the optical fiber becomes possible.

FIG. 6 shows a conventional light emitting device (Japanese Patent Laid-Open No. 62-1 / 1987).
No. 62371), in which, 1 and 2 are electrodes, 3 is a semiconductor plate member, 4 is a horizontal active region, 5 is an inclined hole, and 6 is a reflector plate. Plate material 3
And the horizontal active region 4 form an optical waveguide, and an inclined hole 5 is formed in this optical waveguide by etching or the like, and the light guided in the active region is reflected by the reflection plate 6 and I take it out in the vertical direction (arrow direction).

FIG. 7 is a view showing an example (Japanese Patent Application Laid-Open No. 6-177486) in which light generated by the semiconductor laser is taken out to the outside in a combination structure with a semiconductor laser. Is an electrode, 12 is a substrate, 13 is a clad layer, 14 is an active layer, 15 is a microtrench, and as shown in the figure, a microtrench is formed at the waveguide end of the semiconductor laser including the clad layer 13 and the active layer 45. °
The mirror 15 is formed so that the light guided by the semiconductor laser is reflected by the mirror 15 and is extracted in the direction perpendicular to the guiding direction (arrow direction).

FIG. 8 shows a structure in which an optical waveguide and an external optical system are combined to improve the optical coupling efficiency.
6-66907), in the figure, 21 is a semiconductor laser, 22 is a heat sink, 23 is a bonding surface, 24 is a substrate,
25 is a lens and 26 is an optical fiber.
Is formed as an inclined surface having a cut surface 26a of approximately 45 °. Bonding surface 2 of semiconductor laser 21 and heat sink 22
The light generated in the active layer formed along the line 3
3 is focused on by the lens 25, introduced into the optical fiber 26, and propagated in a direction (arrow direction) perpendicular to the substrate 24.

[0006]

However, FIG. 6 and FIG.
In the example shown in (2), in order to improve the coupling efficiency with an external optical system, it is necessary to externally attach an optical system for condensing light such as a lens and a mirror. In addition, in the example shown in FIG. 8, a lens is added for condensing, but since the condensing lens is attached externally, it is difficult to make the module compact by paying attention to the optical axis adjustment of the lens and the laser. There is.

The present invention has been made in view of the above-mentioned circumstances, and improves the optical coupling efficiency between the optical waveguide and an external optical system while taking out light from the optical waveguide in a direction perpendicular to the optical waveguide. However, the present invention has been made for the purpose of providing a structure of an optical waveguide and a method for manufacturing the same, which solve the above problems.

More specifically, the invention of claim 1 is an optical waveguide for extracting light in a direction perpendicular to the waveguide direction of the optical waveguide and at the same time improving the optical coupling efficiency between the optical waveguide and an external optical system. A structure is provided, and the invention of claim 2 provides a semiconductor laser which extracts light in a direction perpendicular to a waveguide direction of an optical waveguide and at the same time improves optical coupling efficiency with an external optical system. In addition to the inventions of claims 1 and 2, the inventions of claim 3, 4, 5, and 6 have been made for the purpose of providing a method of manufacturing an optical waveguide capable of easily forming a converging optical system. .

[0009]

According to a first aspect of the present invention, a reflection mirror is provided in the middle of an optical waveguide, and guided light is extracted by the reflection mirror in a direction perpendicular to the waveguide direction of the optical waveguide. In addition, it is characterized in that a condensing lens or a condensing mirror is integrated in the extraction part so that the light can be extracted in a direction perpendicular to the waveguide direction of the optical waveguide and the collection part is collected in the extraction part. Since the optical optical system is formed, light can be efficiently coupled to the external optical system, and the optical axis adjustment of the light collecting optical system integrated with the optical waveguide is unnecessary, and
This is a compact optical waveguide with a built-in condensing optical system.

The invention of claim 2 is characterized in that, in the invention of claim 1, the optical waveguide also serves as a semiconductor laser. Therefore, a converging optical system capable of efficiently coupling light with an external optical system is incorporated. The semiconductor laser can be realized.

The invention of claim 3 is characterized in that a waveguide is formed on a substrate in which a condenser lens or a condenser mirror is incorporated. Therefore, since a substrate incorporating a condenser optical system is used, By simply forming a mirror in the waveguide, it is possible to easily manufacture an optical waveguide incorporating a condensing optical system capable of efficiently coupling light with an external optical system.

According to a fourth aspect of the present invention, a reflection mirror is formed by forming a groove oblique to the optical waveguide in the optical waveguide.
It is characterized in that the groove is filled with a material having a refractive index that does not cause total reflection at a surface where guided light first intersects with the groove, and a condenser lens is formed on the material. According to the distance, an optical waveguide incorporating a condensing optical system capable of efficiently coupling light with an external optical system can be easily manufactured.

According to a fifth aspect of the present invention, a reflection mirror is formed by forming an inclined surface in the optical waveguide in an inverted mesa shape with respect to the waveguide direction.
It is characterized by forming a condenser lens on it. Therefore, by forming an oblique end face in the optical waveguide and integrating the condenser lens according to this, light can be efficiently coupled with an external optical system. The optical waveguide incorporating the condensing optical system can be easily manufactured.

According to a sixth aspect of the present invention, an oblique forward mesa-shaped step serving as a reflection mirror is formed on the substrate, an optical waveguide is formed along the oblique step, and then the oblique step is flattened. After that, a condenser lens is formed on the step, and by utilizing the oblique step of the substrate, an optical waveguide with a condenser optical system that can efficiently couple light with an external optical system is provided. It is designed to be easily manufactured.

[0015]

The invention according to claim 1 has a reflecting mirror in the middle of the optical waveguide, and the guided light is extracted by the reflecting mirror in a direction perpendicular to the guiding direction of the optical waveguide. It is characterized in that a condensing lens or a condensing mirror is integrated and provided in the take-out portion. Thus, according to the present invention, since the reflection mirror is incorporated in the middle of the optical waveguide so that the guided light of the optical waveguide can be bent, the guided light is taken out upward (vertical direction) with respect to the guiding direction of the optical waveguide. be able to. If a condenser lens or condenser mirror is formed in the direction of taking out light from the optical waveguide, the optical waveguide and the external optical system can be efficiently coupled with the condenser lens or condenser mirror. Further, in the case of a planar type optical waveguide, the light extraction direction can be horizontal, upward, or downward of the optical waveguide.

According to a second aspect of the invention, in the first aspect of the invention, the optical waveguide also serves as a semiconductor laser. Therefore, according to the present invention, since the semiconductor laser is also an optical waveguide, it is not necessary to form a new waveguide in this case.

The invention of claim 3 is characterized in that a waveguide is formed on a substrate in which a condenser lens or a condenser mirror is incorporated. Therefore, according to the present invention, when the condenser lens or the condenser mirror is formed, since the substrate incorporates the condensing optical system, the optical axis is aligned with the condensing optical system, and the waveguide is formed on the optical axis. It is possible to form a reflection mirror that bends the guided light, and it is possible to efficiently couple with an external optical system. In that case, if a substrate with a condensing optical system capable of forming a waveguide is used, it is only necessary to consider formation of the optical waveguide.

According to a fourth aspect of the present invention, a reflection mirror is formed by forming a groove oblique to the optical waveguide in the optical waveguide,
It is characterized in that the groove is filled with a material having a refractive index such that total reflection does not occur on the surface where the guided light first intersects with the groove, and a condenser lens is formed on the material. That is,
According to the present invention, the optical waveguide is obliquely etched to form an oblique groove, but if it is left as it is, total reflection is caused at the end on the waveguide side. Therefore, a material that transmits guided light is further embedded in the groove. The guided light is transmitted through the buried groove and reflected on the inclined surface on the opposite side of the groove, and the guided light can be extracted upward (vertical direction) with respect to the guiding direction of the optical waveguide.
After that, if a lens is formed in the extraction direction, it can be efficiently coupled with an external optical system. Further, there is an advantage that the distance between the condenser lens and the end face of the waveguide of the groove can be adjusted to the focal length of the condenser lens by controlling the distance of the oblique groove width.

According to a fifth aspect of the present invention, a reflection mirror is formed by forming an inclined surface in the optical waveguide in an inverted mesa shape with respect to the waveguide direction.
It is characterized in that a condenser lens is formed thereon. Therefore, according to the present invention, the total reflection surface mirror that bends the guided light can be easily formed by obliquely etching the optical waveguide to form the reflection mirror. By using this reflecting surface to form a condenser lens in the direction in which guided light is reflected, it can be efficiently coupled with an external optical system, and this is a particularly effective manufacturing method when combined with a semiconductor laser. .

According to a sixth aspect of the present invention, an oblique forward mesa-shaped step serving as a reflection mirror is formed on the substrate, an optical waveguide is formed along the oblique step, and then the oblique step is flattened. After that, a condenser lens is formed on the step. Therefore, according to the present invention, an oblique step serving as a reflection mirror is formed in advance on the substrate, and the optical waveguide is formed along this step. However, since the step still remains, the step is removed. Alternatively, it is flattened by embedding a step. Since the condenser lens can be easily formed on the flat surface according to the step, it can be efficiently coupled to the external optical system.
In particular, it is an effective manufacturing method when it is easy to form an oblique reflection mirror on the substrate or when a substrate originally having a step is used.

[Embodiment 1] FIG. 1 is a process chart for explaining an embodiment of the present invention. First, as shown in FIG. 1A, a rear surface of an n-type InP substrate 30 for a reflection mirror is formed. The paraboloid 31 is formed by oblique dry etching while rotating the substrate using the resist as a mask. The parabolic focus is on the front side of the substrate 30. Next, as shown in FIG. 1B, a Bragg reflection film 32 having an optical thickness of 1/4 of the oscillation wavelength of the laser is formed on the front side of the substrate by repeating n-type InP and n-type InGaAsP. , N-type InP clad layer 3
3, an undoped InGaAsP active layer 34, a p-type InP clad layer 35, and a p-type InGaAsP cap layer 36 in this order.
A semiconductor film is formed by a metal organic chemical vapor deposition method. Next, FIG.
As shown in FIG. 3C, diagonal dry etching is performed at 45 ° until the Bragg reflection film 32 is reached to form the reflection surfaces R ₁ and R ₂ and the separation mesa. At this time, the etching surface R ₁ is made to coincide with the focus of the parabolic surface 31 on the back surface of the substrate, and the mesa width of the laser is made narrower than the diameter of the curved surface portion of the parabolic surface 31. Continuing, as shown in FIG.
An SiO ₂ film 37 for insulation is formed, part of the SiO ₂ on the cap layer is removed, and an AuZn electrode 38 that also serves as an electrode and a reflection mirror is formed.
Is formed, and finally, the AuGeNi electrode 39 serving as an electrode and a reflection mirror is formed on the back surface of the substrate, and the process is completed.

The light trapped in the waveguides 33 to 35 of the semiconductor laser section is guided through the active layer 34, and the reflection mirror R
_The light is reflected upward at ₂ but is reflected by the mirror 38 and returns to the active layer. On the other hand, the light reflected by the reflection mirror R ₁ is partially reflected by the Bragg reflection film 32 to form a resonator. The light transmitted through the Bragg reflection film passes through the substrate 30 while being diffused, and is reflected by the parabolic surface 31 on the rear surface of the substrate to the reflection mirror 39.
Is reflected by, and is reflected in parallel to the substrate vertical direction. This reflected light passes through the substrate and is output from the surface of the substrate. Since the mesa width of the laser is narrower than the diameter of the parabolic surface, the output is not disturbed by the laser. It has a built-in mirror that collimates the semiconductor laser, and can be aligned with a parabolic mirror with the accuracy of photolithography.

The first embodiment is an embodiment in which claims 2 and 3 are combined, and in this embodiment, as shown in FIG. Three
6, the reflection mirror corresponds to R ₁ , the condenser mirror corresponds to 39, and the substrate incorporating the condenser mirror of claim 3 corresponds to 30.

[Embodiment 2] FIG. 2 is a process chart for explaining another embodiment of the present invention. First, as shown in FIG. 2A, a quartz substrate 40 is provided with a metal mask, Ion diffusion partially increases the refractive index. The portion 41 where the ions diffuse has a lens effect. As shown in FIG. 2B, the quartz substrate 40 having the flat lens 41 incorporated therein is added with SiO ₂
A waveguide film including the clad layer 42, the SiON active layer 43, and the SiO ₂ clad layer 44 is formed by the CVD method. Then, as shown in FIG. 2C, when the end R of the waveguide is aligned with the center of the lens 41 of the substrate and etched at 45 °, the light reflected by the end R of the waveguide is condensed by the lens 41. . The setting of the focus can be controlled by the diffusion radius of the ion diffusion unit 41 and the diffusion profile. The light guided through the waveguides 42 to 43 is reflected by the reflection mirror R, condensed by the lens 41, transmitted through the substrate 40, and taken out to the outside. Conversely, external light can be condensed by the lens 41 through the substrate 40 and coupled to the waveguide.

Example 2 is an example in which claims 1 and 3 are combined. As shown in FIG. 2C, the optical waveguide of claim 1 is changed from 42 to 44 and the reflection mirror is changed to R. The condenser lens corresponds to 41, and the substrate incorporating the condenser lens of claim 3 corresponds to 40.

[Embodiment 3] FIG. 3 is a process chart for explaining another embodiment of the present invention. First, as shown in FIG. 3A, a quartz substrate 50 is subjected to a CVD method using SiO ₂ Clad layer 5
1, a waveguide layer composed of the SiO ₂ active layer 52 and the SiO ₂ clad layer 53 is formed. Next, as shown in FIG. 3B, a groove 54 is formed obliquely by 45 ° by dry etching. Further, as shown in FIG. 3C, spin-on-glass (Si) is formed in the groove 54 surrounded by the etching end faces R ₁ and R _2.
O ₂ ) 56 is applied and baked to be embedded. Finally, FIG.
As shown in (E), the condenser lens 57 is formed by performing oblique dry etching while rotating the substrate using the resist as a mask. The light guided through the waveguides 51 to 53 is introduced into the burying layer 56 without being totally reflected by the end face R ₂ . The light propagates while diffusing in the buried layer, is reflected by the reflection mirror 55, and is bent in the direction perpendicular to the substrate.
It is condensed by the lens 57. Conversely, input light from the outside can be coupled to the waveguide. Further, by changing the groove width, the focal position of the lens 57 passing can be controlled.

The third embodiment is an embodiment in which the inventions of claims 1 and 4 are combined, and as shown in FIG. 3 (E), the optical waveguides of 51 to 53 and the reflection mirror of R are as shown in FIG. ₁ , the condenser lens corresponds to 57, the oblique groove of claim 4 corresponds to the portion 54 sandwiched by R ₁ and R ₂ , and the material filling the groove corresponds to 56.

[Embodiment 4] FIG. 4 is a process chart for explaining another embodiment of the present invention. First, an n-type GaAs substrate 6 is used.
0, a structure to be a semiconductor laser is manufactured by a metal organic chemical vapor deposition method. Then, as shown in FIG. 4 (A), n-type AlAs
And a Bragg reflection film 61 composed of alternating layers of p-type AlGaAs
An n-type AlGaAs clad layer 62, an undoped GaAs active layer 63, a p-type AlGaAs clad layer 64, and a p-type GaAs cap layer 65 are laminated. Next, as shown in FIG. 4B, a groove 66 of 45 ° is formed. Thereafter, as shown in FIG. 4C, a SiO ₂ insulating film 67 is formed, the SiO ₂ insulating film on the cap layer is partially removed, and then an AuZn electrode 68 and a back electrode AuGeNi 69 are formed. Finally, as shown in FIG. 4D, the microlens 70 made of polyimide is formed immediately above the groove 66. The light guided through the active layer is totally reflected by the groove 66, and the light reflected in the substrate direction is reflected by the Bragg reflection film 61 and returns to the active layer. On the other hand, a part of the light reflected in the direction opposite to the substrate at the end of the groove 66 is part of the cap layer 65.
The light is reflected by the surface and returns to the active layer, but the remaining light is reflected by the lens 70.
The light is collected or collimated by and taken out in the direction perpendicular to the substrate.

[Embodiment 5] FIG. 5 is a process diagram for explaining another embodiment of the present invention. In this embodiment, a substrate on which a waveguide is formed has a [110] plane [110] ] The Si substrate 80 cut out by inclining by 10 ° is used. When this substrate is used, as shown in FIG. 5A, the (111) plane selectively formed by hydrazine, KOH, or the like is formed on the substrate.
It can be formed at an angle of 5 °. As shown in FIG. 5B, the SiO ₂ clad layer 81 and the SiON active layer 8 are formed on the Si substrate 80 on which the 45 ° step 86 is formed.
2, the SiO ₂ clad layer 83 is laminated to form a waveguide.
Further, as shown in FIG. 5C, a spin-on-glass (SiO ₂ ) burying layer 84 is applied and baked to flatten the step. Similar to the third embodiment, as shown in FIG.
The process is completed by forming the lens 85 centering on the step. The light guided through the waveguides 81 to 83 is reflected by the oblique step 86, collected by the lens 85, and taken out to the outside. Alternatively, external light is collected by the lens 85, reflected by the step 86, and coupled to the waveguide.

Example 5 is an example in which claims 1 and 6 are combined. As shown in FIG. 5D, the optical waveguide of claim 1 is from 81 to 83, and the reflecting mirror is 86. The condenser lens corresponds to 85, and the oblique forward mesa-shaped step of claim 6 corresponds to 86.

[0031]

According to the invention of claim 1, a reflection mirror is provided in the middle of the optical waveguide, and the guided light is extracted by the reflection mirror in a direction perpendicular to the waveguide direction of the optical waveguide, and the extraction portion is provided. Since a condenser lens or condenser mirror is integrated in the structure, it has a structure to extract upwards (vertical direction) with respect to the waveguide direction of the optical waveguide, and a condensing optical system is formed. There is an effect that it can be efficiently coupled with an external optical system, and there is no need to adjust the optical axis of the focusing optical system integrated with the optical waveguide, and a compact optical waveguide incorporating the focusing optical system can be realized.

According to the second aspect of the invention, since the optical waveguide also serves as a semiconductor laser, there is an effect that it is possible to realize a semiconductor laser incorporating a focusing optical system capable of efficiently coupling light with an external optical system.

According to the third aspect of the invention, since the waveguide is formed on the substrate in which the condenser lens or the condenser mirror is incorporated, and the substrate in which the condenser optical system is incorporated is used, the waveguide is mirrored. There is an effect that an optical waveguide incorporating a condensing optical system capable of efficiently coupling light with an external optical system can be easily manufactured only by forming the optical waveguide.

According to a fourth aspect of the present invention, a reflection mirror is formed by forming a groove oblique to the optical waveguide in the optical waveguide,
Since the groove is filled with a material having a refractive index that does not cause total reflection on the surface where the guided light first intersects with the groove, and the condenser lens is formed on the material, the focal length of the condenser lens is In addition, there is an effect that it is possible to easily manufacture an optical waveguide incorporating a condensing optical system that can efficiently couple light with an external optical system.

According to a fifth aspect of the present invention, a reflection mirror is formed by forming an inclined surface in an inverted mesa shape in the optical waveguide with respect to the waveguide direction.
Since a condenser lens is formed on top of it, it is possible to efficiently combine light with an external optical system simply by forming an oblique end face in the optical waveguide and integrating the condenser lens in accordance with this. There is an effect that an optical waveguide incorporating an optical system can be easily manufactured.

According to a sixth aspect of the invention, an oblique forward mesa-shaped step serving as a reflection mirror is formed on the substrate, an optical waveguide is formed along the oblique step, and then the oblique step is flattened. Since the condensing lens is formed on the step after that, it is possible to easily construct an optical waveguide with a built-in condensing optical system that can efficiently couple light with an external optical system by using the oblique step of the substrate. There is an effect that can be manufactured.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining an example of the present invention.

FIG. 2 is a process drawing for explaining another embodiment of the present invention.

FIG. 3 is a process drawing for explaining still another embodiment of the present invention.

FIG. 4 is a process drawing for explaining still another embodiment of the present invention.

FIG. 5 is a process drawing for explaining still another embodiment of the present invention.

FIG. 6 is a main part schematic configuration diagram for explaining an example of a conventional light emitting element (optical waveguide).

FIG. 7 is a schematic configuration diagram of a main part for explaining another example of the conventional optical waveguide.

FIG. 8 is a schematic configuration diagram of a main part for explaining still another example of the conventional optical waveguide.

[Explanation of symbols]

30 ... InP substrate, 31 ... Parabolic surface for reflection mirror, 32
InP / InGaAsP Bragg reflection film, 33 ... InP cladding layer, 34 ... InGaAsP active layer, 35 ... InP cladding layer, 36 ... InGaAsP cap layer, 37 ... SiO ₂
Insulating film, 38 ... AuZn electrode, 39 ... AuGeNi electrode,
R ₁ , R ₂ ... Reflective surface, 40 ... Quartz substrate, 41 ... Lens, 4
2 ... SiO ₂ clad layer, 43 ... SiON active layer, 44 ...
SiO ₂ clad layer, R ... Reflective mirror, 50 ... Quartz substrate,
51, 53 ... SiO ₂ cladding layer, 52 ... SiON active layer, 55 ... Reflecting mirror, 56 ... SiO ₂ burying layer, 57
... Lens, R ₁ , R ₂ ... Etching end surface (reflection surface), 60
... GaAs substrate, 61 ... AlGaAs / AlAs Bragg reflective film, 62 ... AlGaAs cladding layer, 63 ... GaAs active layer, 64 ... AlGaAs cladding layer, 65 ... GaAs cap layer, 66 ... Etching groove, 67 ... AlO ₂ insulating film, 68
... AuZn electrode, 69 ... AuGeNi electrode, 70 ... Lens,
80 ... Si substrate, 81, 83 ... SiO ₂ clad layer, 82
... SiON waveguide layer, 84 ... SiO ₂ burying layer, 85 ... Lens, 86 ... Step portion.

Claims (6)

[Claims] 1. A reflection mirror is provided in the middle of the optical waveguide, the guided light is extracted by the reflection mirror in a direction perpendicular to the waveguide direction of the optical waveguide, and a condensing lens or a condensing lens is provided at the extraction portion. An optical waveguide having an integrated mirror. 2. The optical waveguide according to claim 1, wherein the optical waveguide also serves as a semiconductor laser. 3. A method of manufacturing an optical waveguide, comprising forming a waveguide on a substrate in which a condenser lens or a condenser mirror is incorporated. 4. A reflection mirror is formed by forming a groove oblique to the waveguide direction in the optical waveguide, and the reflection mirror is made of a material having a refractive index such that total reflection does not occur at the surface where the guided light first intersects with the groove. A method for manufacturing an optical waveguide, comprising filling the groove and forming a condenser lens on the material. 5. A method of manufacturing an optical waveguide, characterized in that a slope is formed in the optical waveguide in an inverted mesa shape with respect to the waveguide direction to form a reflection mirror, and a condenser lens is formed thereon. 6. An oblique forward mesa-shaped step serving as a reflection mirror is formed on a substrate, an optical waveguide is formed along the oblique step, and then the oblique step is flattened before the step. A method of manufacturing an optical waveguide, which comprises forming a condenser lens on the substrate.