JP2005221965A - Optical waveguide and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide in which signal light can be transferred at an arbitrary position in an optical circuit, and also to provide the manufacturing method. <P>SOLUTION: The optical waveguide 10 is composed of a core 12 and a clad 13 provided on a substrate 11. In the core 12, there are installed a reflection body 15 which is equipped with a slope 15a crossing the core 12 at an arbitrary angle and which is provided with a triangular or a trapezoidal cross section, and a light reflector 14 which is installed on the slope 15a of the reflection body 15 and which is provided with a light reflecting film 16 for reflecting signal light L1 propagating in the core 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical waveguide for efficiently coupling signal light propagating through an optical waveguide to a surface emitting laser or a surface photodiode, and a method for manufacturing the same.

  In recent years, signal light (optical signal) of a planar optical circuit that integrates various functions is taken out in a direction perpendicular to the plane of the planar optical circuit without using a transmission line such as an optical fiber, and is directly connected to an electric circuit and signal light. Optical / electrical composite mounting technology for exchanging data is being studied.

  An optical waveguide device in which signal light (optical waveguide propagation light) of a planar optical circuit, a surface emitting laser, and a planar photodiode are optically coupled is known as a device using this optical / electrical composite mounting technology. For example, as shown in FIG. 6 as an example of a conventional optical waveguide device 60, the device 60 includes a core 62 having a predetermined refractive index provided on a substrate 61 and a clad 63 having a refractive index lower than that of the core 62. The optical waveguide 65 includes a surface emitting laser 66 and a surface photodiode 67 optically coupled to the optical waveguide 65. Both end surfaces (left and right end surfaces in FIG. 6) 65a and 65b of the optical waveguide 65 are approximately 45 degrees with respect to the horizontal plane in order to refract the laser light (optical waveguide propagation light) L3 emitted from the surface emitting laser 66. It is formed on a slope with an angle α.

  Laser light (signal light) L3 emitted vertically downward from the surface emitting laser 66 is refracted at right angles at the optical waveguide end face 65a and is incident on the core 62. Thereafter, the laser beam L3 propagates in the core 62 in the horizontal direction and is refracted at a right angle again at the opposite optical waveguide end face 65b. By this refraction, the laser beam L3 is emitted (taken out) upward in the vertical direction and received by the surface photodiode 67 (see, for example, Patent Document 1).

JP 2000-235127 A

  However, since the conventional optical waveguide device 60 refracts the laser light L3 at the end faces 65a and 65b of the optical waveguide 65, signal light is exchanged only at the end of the optical circuit, that is, only at the end of the core 62. There is a problem that the configuration and design of the optical circuit are limited.

  Further, since the end faces 65a and 65b that refract the laser light L3 in the direction perpendicular to the surface of the optical waveguide 65 are often formed by polishing, a large amount of the optical waveguide 65 (optical waveguide device 60) is manufactured. It was an unsuitable manufacturing method.

  An object of the present invention, which was created in view of the above circumstances, is to provide an optical waveguide capable of exchanging signal light at an arbitrary position of an optical circuit and a method for manufacturing the same.

  In order to achieve the above object, an optical waveguide according to the present invention is an optical waveguide composed of a core and a clad provided on a substrate, and includes a light reflecting portion having an inclined surface intersecting the core at an arbitrary angle. And at least the surface portion of the inclined surface of the light reflecting portion is made of a metal material.

  Here, the metal material is preferably Ag, Au, Pt, Al, or Ta.

  Further, the optical waveguide according to the present invention is an optical waveguide composed of a core and a clad provided on a substrate, and the cross section provided with an inclined surface intersecting the core at an arbitrary angle in the core has a triangular shape or a base. A light reflecting portion having a shape of a reflecting main body portion and a light reflecting film provided on an inclined surface of the reflecting main body portion and reflecting signal light propagating in the core is provided.

  Here, the light reflecting film is preferably composed of Ag, Au, Pt, Al, or Ta. In addition, a lens that collects the light may be provided in a portion where the signal light reflected on the clad side is extracted.

  According to the above configuration, the light reflecting portion can be provided at an arbitrary position in the longitudinal direction of the core, and signal light can be exchanged at the light reflecting portion, that is, at an arbitrary position of the optical circuit.

  On the other hand, an optical waveguide device according to the present invention includes the above-described optical waveguide and a surface emitting laser and a surface photodiode optically coupled to the optical waveguide.

  According to the above configuration, since the optical waveguide capable of exchanging signal light at any position of the optical circuit is used, the surface emitting laser and the surface photodiode can be provided at any position of the optical circuit. Therefore, the configuration of the optical waveguide device is not limited, and the optical waveguide device can be freely designed.

  On the other hand, in the method of manufacturing an optical waveguide according to the present invention, the surface of the lower clad on the substrate is etched to form a pattern with a rectangular cross section, and the rectangular pattern is subjected to sputter etching or reactive ion etching, A reflection main body having a triangular or trapezoidal cross section is formed, and a light reflection film is provided on the slope of the reflection main body. Here, it is preferable that a core is formed on the lower clad so as to be orthogonal to the reflection main body, and an upper clad is formed so as to cover the core and the lower clad.

  Further, in the method of manufacturing an optical waveguide according to the present invention, a surface portion of a metal film provided on a substrate is etched to form a pattern having a rectangular cross section, and the rectangular pattern is subjected to sputter etching or reactive ion etching. Thus, the reflection main body having a triangular or trapezoidal cross section is formed, and the slope of the reflection main body is formed on the light reflection film.

  Here, it is preferable that a core is formed on the substrate so as to be orthogonal to the reflection main body, and an upper clad is formed so as to cover the core and the substrate.

  According to the above method, a reflection main-body part can be formed in the arbitrary positions of a core longitudinal direction by various etching. As a result, an optical waveguide having a light reflecting portion at an arbitrary position in the core longitudinal direction can be easily manufactured.

  According to the present invention, an excellent effect is obtained that an optical waveguide capable of exchanging signal light at an arbitrary position of an optical circuit can be obtained.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

(First embodiment)
A cross-sectional view of an optical waveguide according to a preferred embodiment of the present invention is shown in FIG.

  As shown in FIG. 1, an optical waveguide 10 according to the present embodiment includes a core 12 having a predetermined refractive index provided on a flat substrate 11 and a clad (upper clad) 13 having a refractive index lower than that of the core 12. In the middle of the core 12, a light reflecting portion 14 for reflecting the signal light (optical waveguide propagation light) L1 propagating in the core 12 to the clad 13 side is provided. Here, in FIG. 1, a laminated structure of the planar substrate 11, the core 12, and the upper cladding 13 is formed. However, a laminated structure of the planar substrate 11, the lower cladding (not shown), the core 12, and the upper cladding 13. It is good. Further, the planar substrate 11 may be a lower clad.

  The light reflecting portion 14 is provided on the reflecting body 15 having an inclined surface 15a intersecting with the core 12 at an arbitrary angle (for example, an angle of about 45 degrees), and the inclined surface 15a of the reflecting body 15 and And a light reflecting film 16 that reflects the signal light L1 propagating in the direction toward the clad 13 at an arbitrary angle. The reflection main body 15 is formed in a triangular (or trapezoidal) cross section.

  The constituent material of the light reflecting film 16 is not particularly limited as long as it is a metal capable of efficiently reflecting light, and examples thereof include Ag, Au, Pt, Al, or Ta, and reflectivity of light. Ag is preferable, and Ta is preferable when considering heat resistance and low thermal expansion.

  The constituent material of the planar substrate 11, the core 12, and the clad 13 is not particularly limited as long as it can constitute an optical circuit, and any material that is conventionally used as a constituent material of an optical circuit is applicable. It is.

  Here, in the optical waveguide 10 according to the present embodiment, the case where only one light reflecting portion 14 is formed has been described. However, a plurality of light reflecting portions 14 may be collectively formed. For example, two light reflecting portions 14 are formed, and a surface emitting laser (see FIG. 6) is optically connected to a position above the inclined surface of the reflecting main body portion 15 in one light reflecting portion 14, and the other light reflecting portion is also connected. An optical waveguide device can be obtained by optically connecting a planar photodiode (see FIG. 6) to a position above the inclined surface of the reflection main body 15 in FIG.

  Next, an example of a method for manufacturing the optical waveguide 10 according to the present embodiment will be described.

  The manufacturing process of the optical waveguide according to the present embodiment is shown in FIGS. 2 (a) to 2 (g) and FIGS. 3 (a) to 3 (g).

  First, as shown in FIG. 2A, a quartz glass substrate was prepared as the planar substrate 21. Next, as shown in FIG. 2B, an etching mask WSi film 22 having a thickness of 1 μm is formed on the surface of the substrate 21.

Next, as shown in FIG. 2C, a resist pattern 23 having a width of 6 μm and a thickness of 1 μm is formed on the WSi film 22 by using a photolithography technique using a photosensitive resist. Using this resist pattern 23 as a mask, as shown in FIG. 2D, the non-mask portion 22a of the WSi film 22 is etched away by reactive ion etching using NF ₃ gas. Thereafter, the resist pattern 23 is removed.

Next, as shown in FIG. 2E, the non-mask portion 21a of the quartz glass substrate 21 is removed by reactive ion etching using CHF ₃ gas using the pattern portion 22b of the WSi film 22 as a mask, As shown in FIG. 2F, a pattern 24 having a rectangular cross section is formed.

  Next, after placing the planar substrate 21 on which the pattern 24 is formed in Ar gas plasma, as shown in FIG. 2G, a part 24a of the pattern 24 having a substantially rectangular cross section is obtained by sputtering with Ar ions. Is removed by etching to form a pattern (reflective body portion) 25 having a substantially triangular cross section. The base angle of the triangle in the reflection main body 25 was 45 degrees. Here, the size of the base angle of the triangle can be adjusted by the pressure of Ar ions. The formation of the reflection main body 25 is not limited to sputter etching with Ar gas, and reactive ion etching may be used. In reactive ion etching, by selecting conditions that enhance the effect of ions, the size of the base angle of the triangle can be adjusted as in the case of sputter etching.

  Next, as shown in FIG. 3A, a Ta film 32 having a thickness of 0.5 μm is formed on the surface 31 of the flat substrate 21 as a light reflecting film by a DC sputtering (DC sputtering) method. Here, metals such as Ag, Au, Pt, and Al can be used as the constituent material of the light reflecting film. However, the manufacturing process temperature of the quartz glass waveguide is higher than 350 ° C. In this form, the Ta film 32 was selected in consideration of heat resistance and low thermal expansion. In the case of a waveguide made of a material other than quartz, for example, a polymer or the like, the manufacturing process temperature is as low as 350 ° C. or lower, so that the constituent material of the light reflecting film may be any metal material.

Next, as shown in FIG. 3B, a resist pattern 33 is formed on the Ta film 32 immediately above the reflecting main body 25 using a photolithography technique. Using this resist pattern 33 as a mask, as shown in FIG. 3C, the non-mask portion 32b of the Ta film 32 is removed by reactive ion etching using SF ₆ gas, and the resist pattern 33 is also removed. Then, the light reflecting film 36 is formed. As a result, the light reflecting portion 34 having the light reflecting film 36 is formed on the surface of the reflecting body portion 25.

Next, as shown in FIG. 3D, a core glass film 37 made of SiO ₂ —GeO ₂ having a GeO ₂ concentration of 10 mol% is formed on the surface 31 of the planar substrate 21 by RF sputtering (high frequency sputtering). To do.

  Next, as shown in FIG. 3E, the surface of the core glass film 37 is subjected to CMP (Chemical Mechanical Polishing) to remove the irregularities 37a, and the surface of the core glass film 37 is smoothed. Thereafter, the core pattern 38 is formed by using a photolithography technique so as to be orthogonal to the reflection main body 25.

Next, using the core pattern 38 as a mask, a core glass film 37 is formed on a core 39 having a rectangular cross section of 6 μm × 6 μm by reactive ion etching using CHF ₃ gas, as shown in FIG. To do.

Finally, a glass film (upper clad) 40 is formed so as to cover the planar substrate 21, the light reflecting portion 34, and the core 39 by plasma CVD using TEOS (tetraethoxysilane) which is a silica raw material and O ₂ gas. By forming, the optical waveguide 10 having the configuration shown in FIG. 1 is obtained.

  As shown in FIG. 1, a photodetector (shown by a one-dot chain line) 18 is disposed above the light reflecting portion 34 of the obtained optical waveguide 10, and the signal light L <b> 1 is incident on the optical waveguide 10 to cause a reflection loss. (Including bond loss). As a result, the reflection loss value is about 1 dB, which is lower than that of the conventional optical waveguide 65 shown in FIG.

  Next, the operation of the optical waveguide 10 according to the present embodiment will be described.

  Prior to the formation of the core 12, the optical waveguide 10 according to the present embodiment first forms the light reflecting portion 14. For this reason, the light reflection part 14 can be formed in the arbitrary positions of a core longitudinal direction. Therefore, unlike the conventional optical waveguide 60 shown in FIG. 6, the signal light can be exchanged only at the end of the optical circuit, that is, only at the end of the core 62, and at any position of the optical circuit. Signal light can be exchanged easily and with low loss. As a result, the configuration of the optical circuit is not limited, and the optical circuit can be freely designed.

  Further, the light reflecting portion 14 of the optical waveguide 10 according to the present embodiment is formed through various etching processes, and does not require polishing unlike the conventional optical waveguide 60 shown in FIG. Therefore, it is suitable for mass production and can be easily mass produced. As a result, the cost of the optical waveguide 10, and thus the optical waveguide device, can be reduced.

  Further, by constructing an optical waveguide device using the optical waveguide 10 according to the present embodiment, a surface emitting laser and a surface photodiode can be provided at an arbitrary position of the optical circuit. Therefore, the configuration of the optical waveguide device is not limited, and the optical waveguide device can be freely designed. As a result, the optical waveguide device can be reduced in size, and the degree of freedom in layout increases.

  Next, another embodiment of the present invention will be described with reference to the accompanying drawings.

(Second Embodiment)
FIG. 4 shows a cross-sectional view of an optical waveguide according to another preferred embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the member similar to FIG. 1, and detailed description is abbreviate | omitted about these members.

  The basic configuration of the optical waveguide 50 according to the present embodiment is the same as that of the optical waveguide 10 according to the previous embodiment, and the signal light L1 reflected by the light reflecting portion 14 is more efficiently detected by a photodetector (illustrated by a one-dot chain line). ) A microlens that collects light on a portion from which the signal light L1 reflected on the clad 13 side is extracted (on the surface of the clad 13 and directly above the inclined surface 15a of the reflection main body 15) to be optically coupled to the clad 13. The difference is that 41 is provided.

  According to the optical waveguide 50 according to the present embodiment, the provision of the microlens 41 enables the signal light L1 reflected by the light reflecting portion 14 to be optically coupled to the photodetector 18 more efficiently. The optical waveguide has a lower loss than the optical waveguide 10 according to the embodiment. In addition, the optical waveguide 50 according to the present embodiment can obtain the same effects as the optical waveguide 10 according to the previous embodiment.

  Next, an example of a method for manufacturing the optical waveguide 50 according to the present embodiment will be described.

After producing the optical waveguide 10 shown in FIG. 3G, as shown in FIG. 5A, the P ₂ O ₅ concentration is 50 mol% on the surface of the upper cladding 40 by RF sputtering (high frequency sputtering). Then, a core glass film 51 made of SiO ₂ —GeO ₂ having a thickness of 8 μm is formed.

  Next, using a photolithography technique, a disk pattern 52 having a diameter of 16 μm is formed on the core glass film 51 as shown in FIG.

Next, using the disk pattern 52 as a mask, as shown in FIG. 5C, the non-masked portion 51a of the core glass film 51 is removed by reactive ion etching using CHF ₃ gas, and the height is 8 μm. A cylindrical pattern 53 having a diameter of 15 μm is formed. Thereafter, the disk pattern 52 is removed, and an optical waveguide 55 shown in FIG. 5D is obtained.

  Next, the entire optical waveguide 55 was subjected to heat treatment at 500 ° C. to 600 ° C. for 3 hours in an oxygen atmosphere. By this heat treatment, the cylindrical pattern 53 is softened, and as shown in FIG. 5E, a hemispherical microlens 56 having a radius of 7.5 μm and a smooth surface is formed on the surface of the upper cladding 40, as shown in FIG. The optical waveguide 50 having the above-described configuration is obtained. The loss when light having a wavelength of 1.55 μm was passed through the microlens 56 was as low as 0.1 dB or less.

  As shown in FIG. 4, a photodetector (shown by a one-dot chain line) 18 is disposed above the microlens 56 of the obtained optical waveguide 50, and the signal light L <b> 1 is incident on the optical waveguide 50 to cause reflection loss (coupling) Loss included). As a result, the reflection loss value is about 0.6 dB, which is lower than that of the optical waveguide 10 according to the previous embodiment shown in FIG.

(Third embodiment)
In the optical waveguide 10 according to the first embodiment and the optical waveguide 50 according to the second embodiment, the light reflecting film 16 is provided on the inclined surface 15a of the reflecting main body portion 15, and only the surface of the light reflecting portion 14 is made of metal. It was composed of wood.

  The basic configuration of the optical waveguide according to the present embodiment is the same as that of the optical waveguide 10 (or the optical waveguide 50) according to the previous embodiment, except that the entire reflection main body is made of a metal material. Yes. That is, in the optical waveguide according to the present embodiment, the light reflecting portion is configured only by the reflecting main body portion. As the metal material constituting the reflection main body portion, the same metal material as that of the light reflection film 16 in the optical waveguide 10 according to the previous embodiment is used.

  The optical waveguide according to the present embodiment can obtain the same effects as the optical waveguide 10 according to the first embodiment (or the optical waveguide 50 according to the second embodiment).

  Next, an example of a method for manufacturing an optical waveguide according to the present embodiment will be described.

  First, a quartz glass substrate was prepared as a flat substrate. Next, a Ta film is formed on the surface of the substrate. Further, an etching mask WSi film is formed on the surface of the Ta film.

Next, a resist pattern is formed on the WSi film using a photolithography technique using a photosensitive resist. Using this resist pattern as a mask, the non-mask portion of the WSi film is removed by reactive ion etching using NF ₃ gas. Thereafter, the resist pattern is removed.

Next, using the pattern portion of the WSi film as a mask, the non-mask portion of the Ta film is removed by reactive ion etching using SF ₆ gas to form a pattern having a rectangular cross section.

  Next, after placing the planar substrate on which the pattern is formed in Ar gas plasma, a part of the pattern having a substantially rectangular cross section is removed by etching by sputter etching using Ar ions, so that the reflection main body having a substantially triangular cross section is formed. Form. The base angle of the triangle in the reflection main body was 45 degrees. Here, the size of the base angle of the triangle can be adjusted by the pressure of Ar ions. Further, the formation of the reflection main body is not limited to the sputter etching using Ar gas, and reactive ion etching may be used. In reactive ion etching, by selecting conditions that enhance the effect of ions, the size of the base angle of the triangle can be adjusted as in the case of sputter etching.

  Thereafter, the process shown in FIG. 3 is performed through the steps shown in FIGS. 3D to 3G (or FIGS. 3D to 3G and 5A to 5E). The optical waveguide according to the present embodiment having the same configuration as that of the optical waveguide 10 (or the optical waveguide 50 shown in FIG. 4) is obtained.

  According to the optical waveguide according to the present embodiment, it is possible to form the light reflecting portion only by forming the reflection main body portion. Therefore, like the optical waveguide 10 according to the first embodiment, the light reflecting film is formed. 16 is not required (see FIGS. 3A to 3C). For this reason, the optical waveguide according to the present embodiment is easier and easier to manufacture than the optical waveguide 10 according to the first embodiment.

  As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various other things are assumed.

1 is a cross-sectional view of an optical waveguide according to a preferred embodiment of the present invention. It is sectional drawing explaining the process until it forms a reflection main-body part among the manufacturing processes of the optical waveguide shown in FIG. It is sectional drawing explaining the process after forming a reflection main-body part among the manufacturing processes of the optical waveguide shown in FIG. It is sectional drawing of the optical waveguide which concerns on other suitable one Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the optical waveguide of FIG. It is sectional drawing of the conventional optical waveguide apparatus.

Explanation of symbols

10 Optical waveguide 11 Planar substrate (substrate)
12 Core 13 Cladding 14 Light reflecting portion 15 Reflecting main body portion 15a Slope 16 Light reflecting film L1 Signal light

Claims (10)

  In an optical waveguide composed of a core and a clad provided on a substrate, a light reflecting portion having a slope intersecting with the core at an arbitrary angle is provided in the core, and at least a surface portion of the slope of the light reflecting portion is provided. An optical waveguide comprising a metal material.   The optical waveguide according to claim 1, wherein the metal material is Ag, Au, Pt, Al, or Ta.   In an optical waveguide composed of a core and a clad provided on a substrate, a reflection main body having a triangular or trapezoidal cross section with a slope intersecting with the core at an arbitrary angle in the core, and the reflection main body An optical waveguide comprising a light reflecting portion provided on a slope of the portion and having a light reflecting film for reflecting signal light propagating in the core.   The optical waveguide according to claim 3, wherein the light reflecting film is made of Ag, Au, Pt, Al, or Ta.   The optical waveguide according to claim 1, wherein a lens for condensing light is provided at a portion where the signal light reflected on the clad side is extracted.   6. An optical waveguide device comprising: the optical waveguide according to claim 1; and a surface emitting laser and a planar photodiode optically coupled to the optical waveguide.   Etching is performed on the surface of the lower clad on the substrate to form a pattern with a rectangular cross section, and the rectangular pattern is subjected to sputter etching or reactive ion etching to form a reflective main body having a triangular or trapezoidal cross section. And a method of manufacturing an optical waveguide, comprising providing a light reflecting film on the inclined surface of the reflecting main body.   8. The method of manufacturing an optical waveguide according to claim 7, wherein a core is formed on the lower clad so as to be orthogonal to the reflection main body, and an upper clad is formed so as to cover the core and the lower clad.   Etching is performed on the surface portion of the metal film provided on the substrate to form a pattern having a rectangular cross section, and the rectangular pattern is subjected to sputter etching or reactive ion etching to form a reflective main body having a triangular or trapezoidal cross section. And a slope of the reflecting body portion is formed on the light reflecting film. 10. The method of manufacturing an optical waveguide according to claim 9, wherein a core is formed on the substrate so as to be orthogonal to the reflection main body, and an upper clad is formed so as to cover the core and the substrate.

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