JP2009139413A - Optical element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve an optical combination from the upper surface side of an optical element. <P>SOLUTION: The optical elements 10 are provided to a base layer 22 and on the base layer and includes a substrate 20 which has a cladding layer 24 having a flat upper surface 24X, an optical waveguide 26 which has at least one end face 26a in the upper surface, and a recess 28 for forming a mirror part which has a depth into the thickness of the substrate from the upper surface of the substrate and which has a reflection side face 22a having a mirror part 30 for reflecting incoming signal light and an opposing side face 22b opposing to the reflection side face. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical element including an optical waveguide used for optical fiber communication, for example, and a manufacturing method thereof.

  In optical fiber communication, for example, an optical element including an optical waveguide for branching an optical signal input from an optical fiber or optically coupling optical fibers to each other is known.

  As such an optical element, a light receiving element is mounted on a substrate on which an optical waveguide is formed. Separately from this substrate, a reflecting mirror for receiving signal light emitted from the optical waveguide by the light receiving element. There is known a configuration including a cover having a (see, for example, Patent Document 1).

In addition, an optical element including a so-called silicon optical waveguide made of a thin silicon wire is known to include a waveguide having a tapered portion whose cross-sectional area decreases toward the tip (see, for example, Patent Document 2). .)
JP 2004-184986 A Japanese Patent No. 2930178

  A silicon optical waveguide made of silicon can have a smaller bending radius, but in order to satisfy the single mode condition, the cross-sectional dimension of the optical waveguide needs to be about 300 nm square, for example.

  In order to optically couple an optical waveguide having a small cross-sectional dimension and an optical fiber as disclosed in Patent Document 1, it is necessary to perform extremely precise alignment.

  When performing such precise alignment, a dedicated device must be prepared and a long time is required.

  Also, as disclosed in Patent Document 2, if the shape of the optical waveguide is a so-called tapered shape, the alignment accuracy between the optical waveguide and the optical fiber can be reduced, but the light is emitted from the optical fiber. In addition, a condensing member such as a lens for condensing the signal light to be collected is further required, and alignment between the condensing member and the optical fiber is further required.

  In the optical element disclosed in Patent Document 1, a cover including a reflecting mirror is used as an additional member, in addition to the substrate on which the optical waveguide is provided.

  As described above, according to the conventional optical element, the structure of the entire optical element is complicated, and the optical element tends to be enlarged as a whole.

  Further, in the manufacturing process of the conventional optical element, there may be a case where a further special manufacturing apparatus is required in addition to a manufacturing apparatus used in a so-called wafer process.

  Further, in the conventional optical element manufacturing process as described above, there is a case where the end face of the optical waveguide on which signal light is incident or emitted is formed by a so-called dicing process using a rotating blade, for example. In such a case, the end face of the optical waveguide may be damaged, and the optical characteristics may be impaired.

  The inventor of the present invention is manufacturing the optical element in which the mirror portion is formed within the thickness of the substrate on which the optical waveguide is formed in a simple process by applying only the conventional wafer process while advancing earnest research. As a result, it has been found that the conventional problems can be solved, and the present invention has been completed.

  The present invention has been made in view of the above-described conventional problems. Accordingly, the object of the present invention is to provide a simple configuration that is easy to align with an optical fiber disposed particularly on the upper surface side of an optical element. It is an object of the present invention to provide a manufacturing method that can be manufactured using only a conventional wafer process and a manufacturing apparatus applied to the wafer process.

  According to a preferred configuration example of the optical element of the present invention, the following configuration may be provided.

  That is, the optical element includes a base layer and a substrate provided on the base layer and having a clad layer having a flat upper surface.

  The optical element includes an optical waveguide provided with at least one end face in the upper surface.

  Furthermore, the optical element is a concave part for forming a mirror part having a depth extending from the upper surface of the substrate to the thickness of the substrate, and a reflective side surface provided with a mirror part for reflecting incident signal light, And a mirror portion forming recess having an opposing side surface facing the reflection side surface and connected to the end surface of the optical waveguide.

  The end face of the optical waveguide of the optical element is inclined with respect to a plane perpendicular to the upper surface, and is an inclined plane that allows signal light to enter the mirror part or receive signal light reflected from the mirror part. It is good.

  The optical waveguide of the optical element is preferably a thin silicon optical waveguide extending on the upper surface.

  Further, the base layer of the optical element is preferably a silicon layer, and the cladding layer is preferably a silicon oxide layer.

  Furthermore, the mirror part is preferably provided as a gold thin film.

  Further, the optical element integrally covers the end face of the optical waveguide and the mirror part, and embeds the concave part for forming the mirror part, and has an embedded part having a refractive index smaller than that of the optical waveguide and larger than that of air. It is better to have more.

  At this time, the embedded portion of the optical element is preferably made of an epoxy resin.

  In addition, according to the method for manufacturing an optical element of the present invention, the following steps may be included.

  Preparing a substrate having an underlayer, a clad layer provided on the underlayer, and an optical waveguide forming layer provided on the clad layer;

  A step of patterning the optical waveguide forming layer to form an optical waveguide extending with one end face in the middle of the cladding layer.

  A step of exposing a base layer by etching away a portion of the cladding layer exposed to the one end face of the cladding layer exposed outside the optical waveguide.

  Forming a resist layer that covers the upper surface side of the substrate and has a resist recess above the exposed region of the underlayer;

  The step of transferring the shape of the resist concave portion to the underlayer to form a mirror portion forming concave portion having a reflective side surface and an opposite side surface facing the reflective side surface.

  Forming a mirror part in a mirror part forming region set on the reflection side surface;

  Further, in the step of forming the concave portion for forming the mirror portion, it is preferable that the end face of the optical waveguide is patterned into an inclined plane that is inclined with respect to a plane perpendicular to the upper surface of the cladding layer.

  Furthermore, the step of forming the mirror portion may be a step of depositing a gold thin film only on the mirror portion forming region using a mirror portion forming resist pattern that exposes the mirror portion forming region.

  The method for manufacturing an optical element preferably further includes a step of forming an embedded portion that integrally covers the end face of the optical waveguide and the mirror portion and embeds the recess for forming the mirror portion.

  The step of forming the embedded portion is preferably a step of forming the embedded portion with a material having a refractive index smaller than that of the optical waveguide and higher than that of air.

  Further, this material is preferably used as an epoxy resin for the manufacturing process of the embedded portion.

  According to the optical element of the present invention, the concave portion for forming the mirror portion is formed within the same thickness as the substrate on which the optical waveguide is provided, and the mirror portion is provided on one side surface of the concave portion for forming the mirror portion. The optical element can be further reduced in size without using additional members.

  Further, according to the optical element of the present invention, since the mirror portion is provided in the concave portion for forming the mirror portion that is open on the upper side, for example, an optical signal of an optical fiber having a spot size of several μm Since alignment with the mirror portion is performed, alignment becomes easier as compared with the case where an optical signal condensed to a diameter of about 1 μm to 2 μm by a ball lens or the like is aligned with a waveguide having a diameter of about 1 μm. . Therefore, the alignment accuracy can be further improved and the coupling efficiency can be further increased.

  Furthermore, according to the method for manufacturing an optical element of the present invention, the optical element of the present invention having the above-described configuration can be formed by a conventional so-called wafer process. Therefore, the optical element can be manufactured more efficiently without requiring further capital investment.

  Embodiments of the present invention will be described below with reference to the drawings. The drawings merely schematically show the shape, size, and arrangement relationship of each component to the extent that the present invention can be understood, and the present invention is not particularly limited thereby. Moreover, in each figure used for the following description, it should be understood that the same components are denoted by the same reference numerals, and redundant description thereof may be omitted.

(First embodiment)
With reference to FIGS. 1A, 1 </ b> B, and 1 </ b> C, a configuration example of an optical element according to an embodiment of the present invention will be described.

  FIG. 1A is a schematic plan view of the optical element as viewed from the upper surface side, and FIG. 1B is a schematic diagram showing a cut surface cut along a dashed line II ′ shown in FIG. FIG. 1C is a schematic cross-sectional view showing a cut surface cut along a dashed line II-II ′ shown in FIG.

  As shown in FIGS. 1A, 1 </ b> B, and 1 </ b> C, the optical element 10 according to the embodiment of the present invention includes a substrate 20. The substrate 20 is preferably a parallel plate type, that is, has a rectangular shape as viewed from above as shown in FIG.

  As shown in FIG. 1B, in this example, the substrate 20 includes an underlayer 22 and a clad layer 24 provided on the underlayer 22 and having a flat upper surface 24X.

  An optical waveguide 26 is provided on the upper surface 24X of the cladding layer 24. As shown in FIG. 1C, in this example, the optical waveguide 26 is a thin waveguide having a uniform cross-sectional area at any part of the extension length.

  The optical waveguide 26 has at least one end face in the upper surface of the clad layer 24, that is, a first end face 26 a in the illustrated example.

  Although details will be described later, in the manufacturing process, the optical waveguide 26 is derived from a layer that is integrated with the base layer 22 and the clad layer 24 described above, and therefore may be described as a part of the substrate 20 in the following description. is there.

  In this example, the substrate 20 preferably has, for example, a first silicon layer, a silicon oxide film layer stacked on the first silicon layer, and a second silicon layer stacked on the silicon oxide layer. It is preferable to use a so-called SOI (Silicon on Insulator) substrate. That is, the base layer 22 is preferably a first silicon layer, the cladding layer 24 is a silicon oxide layer, and the optical waveguide 26 is derived from the second silicon layer.

  When the optical waveguide 26 is a silicon waveguide made of silicon, it is preferable that the cross section with respect to the extended length is a square of about 300 nm square.

  Further, the optical waveguide 26 that is a silicon waveguide may be doped with an impurity such as phosphorus (P) in order to obtain desired optical characteristics.

  Further, the substrate 20 is not limited to the above-described SOI substrate. For example, a glass substrate may be used, and for example, germanium may be deposited on the glass substrate as an optical waveguide material.

  The optical element 10 has a recess 28 for forming a mirror part. In this example, the recess 28 for forming the mirror part has a depth from the upper surface 24X of the substrate 20, that is, the cladding layer 24, to the thickness of the substrate 20, that is, to the middle of the thickness of the base layer 22.

  As shown in FIG. 1 (A), in this example, the recess 28 for forming the mirror part is extended in the short axis direction of the optical element 10 having a rectangular shape, that is, the substrate 20, and both ends are opened. It has a substantially semicylindrical shape, that is, a groove shape.

  In this example, the recess 28 for forming the mirror part is described as a groove shape having both ends in the short axis direction open. However, the present invention is not limited to this, and the optical function is not impaired. It is also possible to adopt any suitable configuration such as a dent closed at both ends.

  As shown in FIG. 1B, the mirror portion forming recess 28 is connected to the reflective side surface 28a, the opposed side surface 28b facing the reflective side surface 28a, and the reflective side surface 28a and the opposed side surface 28b. It has a bottom surface 22c.

  In this example, the reflective side surface 28a is a curved surface having any suitable curvature. The opposed side surface 28b is a flat inclined surface. The bottom surface 22c is a flat and horizontal surface that connects the reflecting side surface 28a and the opposing side surface 28b.

  The reflective side surface 28a is connected to the cladding layer first side surface 24a formed through the cladding layer 24 and is connected to the cladding layer first side surface 24a, and the base layer first side surface 22a has an edge located within the thickness of the base layer 22. It is configured.

  A mirror portion formation region 30X is set on the entire surface of the reflection side surface 28a or a partial region thereof. The mirror part 30 is provided in the mirror part forming region 30X. The mirror unit 30 is a planar or three-dimensional structure having an incident surface and has any suitable optical characteristics.

  In this example, the mirror unit 30 is provided as a reflecting mirror that reflects incident signal light as collimated light.

  The mirror unit 30 is preferably in close contact with the reflective side surface 28a, and preferably configured as a thin film of gold (Au), for example.

  For example, when the optical element 10 is used for optical coupling between optical fibers, the mirror portion 30 is preferably configured as a curved surface having a curvature radius of about 1 μm.

  The radius of curvature of the mirror portion 30 can be arbitrarily selected in consideration of factors such as the distance to the optical waveguide 26, for example.

  The opposing side surface 28 b is connected to the cladding layer second side surface 24 b formed so as to penetrate the cladding layer 24, and the lower side edge is located within the thickness of the base layer 22. It is comprised by the side surface 22b.

  Since the opposing side surface 28b and the bottom surface 22c do not have to perform an optical function, the shape thereof is not limited to a flat surface, and may be provided as a curved surface, for example.

  As illustrated in FIG. 1B, the optical waveguide 26 extends on the upper surface 24 </ b> X of the cladding layer 24. The first end face 26 a of the optical waveguide 26 is incident on the mirror unit 30 and is reflected by the mirror unit 30 so that an optical signal can be incident on the mirror unit 30 positioned within the thickness of the substrate 20. It is provided so that the emitted optical signal can be received.

  In other words, the mirror unit 30 reflects the signal light incident from the upper side of the optical element 10 so that the reflected signal light can be incident on the first end surface 26a of the optical waveguide 26, or the first end surface 26a. The signal light emitted from the optical element 10 is reflected on the upper surface side of the optical element 10, that is, provided so as to be emitted.

  In this example, the first end face 26 a of the optical waveguide 26 is provided so as to be connected to the clad layer second side face 24 b of the clad layer 24.

  The first end face 26a is preferably, for example, a plane with respect to the vertical surface of the upper surface 24X of the clad layer 24 which is a flat surface, on condition that the signal light can be incident on the mirror part 30 or the signal light can be received from the mirror part 30. It is preferable to configure it as an inclined plane having an angle θ. More specifically, the first end face 26a may be an inclined plane having an inclination of about 15 ° with respect to a vertical plane orthogonal to the major axis direction of the upper surface 24X of the cladding layer 24.

  The inclination angle and the inclination direction of the first end face 26a can be arbitrarily selected from the viewpoint of the relative positional relationship with the mirror unit 30 and desired optical characteristics.

  According to the configuration of the optical element of the present invention, the concave portion for forming the mirror portion is formed within the same thickness as the substrate on which the optical waveguide is provided, and the mirror portion is provided on one side surface of the concave portion for forming the mirror portion. Therefore, the optical element can be further reduced in size without using additional members.

  Further, according to the optical element of the present invention, since the mirror part is provided in the concave part for forming the mirror part that is open to the upper side, the optical coupling between optical devices such as optical fibers can be performed on the upper side of the element. In particular, it is easy to align the optical device arranged above the element. Therefore, the accuracy of such alignment can be further improved and the coupling efficiency can be further increased.

(Optical element manufacturing method)
With reference to FIGS. 2A, 2B and 2C and FIG. 3, an example of a method for manufacturing an optical element according to an embodiment of the present invention will be described.

  2A, 2 </ b> B, and 2 </ b> C are schematic views illustrating a cut surface of a structure that is being manufactured in order to explain the manufacturing process of the optical element.

  A cut surface cut in the direction of the dashed line I-I ′ shown in FIG.

  As shown in FIG. 2A, first, an SOI substrate is prepared as a substrate 20 in this example. For example, a commercially available SOI substrate having a diameter of about 6 inches (15.24 cm) can be used.

  That is, it has a base layer 22 which is a silicon layer, a clad layer 24 made of a silicon oxide film stacked on the base layer 22, and an optical waveguide forming layer 26X stacked on the clad layer 24. A substrate 20 is prepared.

  The thickness of the underlayer 22 can be set to any suitable thickness on the condition that the above-described recess for forming the mirror part can be formed, and preferably about 620 μm, for example.

  The thickness of the clad layer 24 can be about 500 μm, but when the optical waveguide is made of silicon, it is preferably 2 μm or more, for example.

  The optical waveguide forming layer 26X has a resistivity as high as possible in order to obtain desired optical characteristics as an optical waveguide, that is, in consideration of light transmittance, and preferably in the range of, for example, about 10 Ωcm to 40 Ωcm. It is necessary to make it a layer having

  For this reason, in order to obtain desired optical characteristics in the optical waveguide forming layer 26X, an impurity such as phosphorus is doped in advance as an arbitrary suitable concentration according to a conventional method, or the optical waveguide forming layer 26X satisfying the optical characteristics is provided. It is preferable to prepare a substrate having

  In this substrate 20, a recess forming region 20 </ b> X is set in advance in a range corresponding to the design of the optical element.

  Next, the optical waveguide 26 is formed. The optical waveguide 26 is formed by a series of conventionally known wafer processes including a mask pattern formation by a photolithography process, a patterning of the optical waveguide formation layer 26X by an etching process using the mask pattern, and a removal of the mask pattern. It can be implemented using a manufacturing device.

  As the mask pattern forming step, it is preferable to form a resist pattern in accordance with a conventional method, preferably using, for example, a negative EB resist material corresponding to an electron beam drawing apparatus.

The etching step is preferably an etching step according to a conventional method using, for example, SF ₆ as an etching gas and using a parallel plate type RIE (reactive ion etching) apparatus.

  As shown in FIG. 2B, the exposed cladding layer is etched by etching the region exposed from the mask pattern until the upper surface 24X of the cladding layer 24 is exposed by the patterning process of the optical waveguide forming layer 26X. A precursor optical waveguide 26Y extending on the upper surface 24X of 24 is formed.

  Depending on the shape of the mask pattern, the precursor optical waveguide 26Y can have any suitable extended shape.

  At the end of this step, the first end face 26a is not yet formed, and the precursor optical waveguide 26Y also extends into the recess forming region 20X.

  As the formation process of the precursor optical waveguide 26Y, the resist pattern formation process using the electron beam drawing apparatus and the etching process using the RIE apparatus have been described. However, the present invention is not limited to this. You may implement by the formation process and the etching process using an ICP (Inductively Coupled Plasma) etching apparatus.

  As shown in FIG. 2C, next, the cladding layer 24 exposed in the recess forming region 20X is removed by patterning to expose a part of the base layer 22. Next, as shown in FIG.

  This step can be performed by a photolithography step and an etching step according to a conventional method.

  The region from which the cladding layer 24 is removed, that is, the exposed region 20Xa where the underlayer 22 is exposed, is an underlayer first side surface 22a formed by engraving the underlayer 22 already described with reference to FIG. The underlayer second side surface 22b and the bottom surface 22c are regions that can be formed by an etching process for the underlayer 22 described later.

  Although details will be described later, during the etching process for the base layer 22, the precursor optical waveguide 26Y extending into the recess forming region 20X and a portion of the cladding layer 24 including the region immediately below the portion are etched, referring to FIG. Thus, the first end face 26a and the clad layer second end face 24b already described are formed.

  Accordingly, the precursor optical waveguide 26Y extending into the recess forming region 20X and a portion of the cladding layer 24 including the region immediately below the precursor optical waveguide 26Y, that is, in this example, perpendicular to the major axis of the substrate 20 along the edge of the precursor optical waveguide 26Y. The remaining region 24c, which is a part of the cladding layer 24 in the region sandwiched between the extending line and the boundary line of the recess forming region 20X on the precursor optical waveguide 26Y side, is left.

  Next, a recess-forming resist pattern 50 is formed on the entire upper surface of the substrate 20. The recess forming resist pattern 50 is formed so as to cover the entire surface of the structure formed by the above-described steps.

  In the step of forming the recess-forming resist pattern 50 pattern, for example, an analog type positive EB resist material corresponding to an electron beam drawing apparatus is preferably used to form a resist pattern in accordance with a conventional method.

  Specifically, preferably, for example, OEBR-1000 (trade name) manufactured by Tokyo Ohka Co., Ltd. is used as an EB resist material, exposure is performed with an electron beam drawing apparatus with an acceleration voltage of 30 kV, and tetraethylammonium hydroxide ( A resist pattern can be formed by developing using TEAH.

  The recess forming resist pattern 50 has a resist recess 50a in the exposed region 20Xa.

  The resist recess 50a is transferred to the base layer 22 by the etching process using the resist pattern 50 for forming a recess, and the first side surface 22a of the base layer already described with reference to FIG. The mirror portion forming region 30X, the base layer second side surface 22b, and the bottom surface 22c can be formed.

  That is, the planar shape of the resist recess 50a viewed from the upper surface side is substantially the same as the shape of the formed underlying layer first side surface 22a, underlying layer second side surface 22b, and bottom surface 22c viewed from the upper surface side.

  The depth of the resist recess 50a, that is, the three-dimensional shape perpendicular to the substrate surface may be determined in consideration of the etching rate of the underlayer 22 and the etching rate of the resist pattern 50 for forming the recess.

  For example, when the etching rate ratio between the base layer 22 and the concave portion forming resist pattern 50 is 10: 1, the depth from the upper surface of the base layer 22 to the bottom surface 22c of the mirror portion concave portion 28 is 30 μm. If desired, the depth of the resist recess 50a of the recess forming resist pattern 50 may be set to 3 μm.

  Next, an etching process is performed to transfer the shape of the resist recess 50a of the recess forming resist pattern 50 to the base layer 22 in the recess forming region 20X.

This etching step preferably uses, for example, a mixed gas of SF ₆ and O ₂ as an etching gas by adjusting the etching rate ratio by adjusting the mixing ratio thereof, and a parallel plate type RIE (Reactive Ion Etching: An etching process according to a conventional method using a (reactive ion etching) apparatus is preferable.

  By this etching process, the reflective side surface 28a on which the mirror portion forming region 30X is set, that is, the base layer first side surface 22a and the cladding layer first side surface 24a, and the counter side surface 28b facing the reflective side surface 28a, that is, the base layer A recess 28 for forming a mirror part having the second side surface 22b is formed.

  At this time, a partial region extending into the recess forming region 20X of the precursor optical waveguide 26Y is also etched to complete the optical waveguide 26 having the first end face 26a capable of emitting and receiving an optical signal. That is, the concave portion forming resist pattern 50 is designed to have a shape that can form not only the mirror portion forming concave portion 28 but also the first end portion 26a of the optical waveguide 26 in particular.

  The concave portion forming resist pattern 50 is preferably formed in a shape such that the first end portion 26a can have a shape having an end surface which is an inclined plane having an inclination with respect to a vertical surface with respect to the upper surface of the substrate 20, for example.

  Therefore, in the concave portion forming resist pattern 50, a partial region located immediately above the precursor optical waveguide 26Y extending in the concave portion forming region 20X is perpendicular to the upper surface 24X of the substrate 20, that is, the clad layer 24 which is a flat surface. It may be designed and formed as an inclined plane having an inclination with respect to the surface.

  As a process for forming the recess 28 for forming the mirror part, a resist pattern is formed by an electron beam drawing apparatus and an etching process according to a conventional method using an RIE apparatus has been described. However, the manufacturing method of the present invention is not limited to this, for example By using a conventionally known technique such as multiple exposure, a recess forming resist pattern 50 having an arbitrarily suitable fine shape is formed, and this shape is transferred to the underlayer using the recess forming resist pattern 50 to form a mirror portion. The concave portion 28 can also be formed.

  Further, the resist material is exposed and developed using a so-called gray mask photomask capable of forming a fine and three-dimensional resist pattern, thereby forming a recess-forming resist pattern 50 having any suitable fine shape. Then, by using this concave portion forming resist pattern 50 and transferring this shape to the underlying layer, the mirror portion concave portion 28 can be formed.

  As shown in FIG. 3, next, the mirror part 30 is formed on the mirror part forming region 30X of the formed mirror part forming recess 28, that is, on the surface of the base layer first side face 22a.

  First, a mask for forming a mirror part that exposes only the mirror part forming region 30X using a resist material selected in consideration of an aspect ratio or the like in accordance with a desired mirror part mode by a conventionally known photolithography process. Form a pattern.

  Next, a mirror part material that can function as a reflecting mirror, preferably gold, for example, is deposited on the entire exposed surface by a conventionally known deposition process.

  Next, the resist pattern for forming the mirror part is removed by a technique suitable for the resist material used. By this step, the mirror part material existing outside the mirror part formation region 30X is removed, and the mirror part 30 is formed.

  Through the above steps, the optical element 10 is completed in the mirror portion formation region 30X.

  According to the method of manufacturing an optical element of the present invention, each process can be performed by a conventional so-called wafer process. Therefore, the optical element can be manufactured more efficiently without requiring further capital investment.

(Second Embodiment)
With reference to FIG. 4, a configuration example of an optical element according to another embodiment of the present invention and a manufacturing method thereof will be described.

  The optical element of this embodiment is characterized in that the mirror part forming recess 28 of the optical element 10 of the first embodiment already described is further embedded by the embedded part 40.

  The configuration other than the embedded portion 40 is not different from the components of the optical element 10 of the first embodiment already described. Therefore, the same numbers are assigned to the same configurations as those of the first embodiment. A detailed description thereof will be omitted.

(Configuration example of optical element)
FIG. 4A is a schematic plan view of the optical element as viewed from the upper surface side, and FIG. 4B is the same position as the one-dot chain line II ′ shown in FIG. It is the schematic which shows the cut surface which cut | disconnected.

  As shown in FIG. 4, the mirror portion forming recess 28 is embedded by the embedded portion 40.

  The embedded portion 40 integrally covers the mirror portion 30 in the mirror portion forming recess 28 and the first end surface 26 a of the optical waveguide 26 and embeds the entire mirror portion forming recess 28.

  The embedded portion 40 is preferably made of a material having a refractive index smaller than that of the optical waveguide 26 and larger than that of air, for example.

  When the optical waveguide 26 is made of, for example, silicon, the mirror portion is made of a material having a refractive index smaller than 3.4, which is the theoretical refractive index of silicon, and a refractive index of air, that is, a refractive index larger than 1. The formation recess 28 is preferably embedded to form the embedded portion 40.

  Specifically, the embedded portion 40 is a material that becomes a solid after being embedded, preferably, for example, on condition that the optical function performed by the optical element 10 of the first embodiment already described is at least not impaired. Any suitable polymer material such as epoxy resin, fluorinated polyimide, deuterated PMMA, and commercially available optical fiber adhesive can be used.

  In addition, the embedded portion 40 can be preferably formed of, for example, a high-refractive-index low-melting glass or a silicon nitride film.

  As described above, if the entire concave portion for forming the mirror portion is embedded with a high refractive material, the radiation angle of the signal light incident on the mirror portion, that is, the spread angle can be further reduced. Signal light can be incident more efficiently. Therefore, the optical devices can be connected more effectively.

  Further, the emission or light receiving end face of the optical waveguide and the mirror part can be more effectively protected.

(Optical element manufacturing method)
In the same manner as in the first embodiment described above, the process up to the formation of the mirror part 30 in the mirror part forming recess 28 is performed.

  Next, the inside of the recess 28 for forming the mirror part is embedded by a process corresponding to the selected material.

  For example, when a polymer material such as an epoxy resin is used, it is preferably formed by embedding by a conventional potting method using a conventionally known dispenser.

  For example, in the case of embedding with a silicon nitride film, it may be a process of embedding by a CVD (Chemical Vapor Deposition) process according to a conventional method.

(Evaluation test of optical element coupling state)
With reference to FIG. 5, FIG. 6 (A) and (B), the evaluation system of the evaluation test which evaluates a coupling state is demonstrated about each optical element concerning the 1st and 2nd form already demonstrated.

  FIG. 5 is a schematic diagram of an evaluation system. Although an example in which the optical element of the first embodiment is applied will be described as an example of illustration, the illustration and description thereof are omitted for the second embodiment because there is no change in the configuration other than the optical element. To do.

  As shown in FIG. 5, the optical element 10 optically couples the first fiber 60A and the second fiber 60B, which are optical fibers.

  In this example, the optical element 10 includes a mirror having a radius of curvature of 1 μm and formed of a gold thin film as the mirror portion 30.

  The optical element according to the second embodiment includes an embedded portion made of an epoxy resin.

  As the first fiber 60A and the second fiber 60B, so-called single mode fibers having a core diameter of 5 μm were used.

  The first fiber 60 </ b> A is disposed on the upper surface side, which is the side where the mirror-forming concave portion 28 of the optical element 10 opens.

  The first outgoing end 60Aa of the first fiber 60A is optically connected to face the mirror part 30 of the optical element 10.

  The second fiber 60B is disposed on the second end face 26b side of the optical waveguide 26 of the optical element 10.

  The incident end 60Ba of the second fiber 60B is optically connected so as to face the second end face 26b of the optical waveguide 26.

  A so-called optical power meter available on the market is connected to the second exit end 60Bb of the second fiber 60B (not shown).

  That is, the signal light emitted from the first emission end 60 </ b> Aa of the first fiber 60 </ b> A is reflected by the mirror unit 30.

  The signal light reflected by the mirror unit 30 is received by the first end face 26a of the optical waveguide 26 and emitted from the second end face 26b.

  The signal light emitted from the second end face 26b is received by the incident end 60Ba of the second fiber 60B and emitted from the second emission end 60Bb.

  The optical power meter observes the signal light emitted from the second emission end 60Bb.

(Evaluation test results)
With reference to FIG. 6 (A) and (B), it demonstrates per evaluation result. These were evaluated for the amount of axial deviation in the direction perpendicular to the drawing, that is, in the direction perpendicular to the optical axis of the optical fiber.

  FIG. 6A is a tolerance curve showing an evaluation result when the optical element of the first embodiment is used, and FIG. 6B is an evaluation when the optical element of the second embodiment is used. It is a tolerance curve which shows a result. The vertical axis represents coupling efficiency (dB), and the horizontal axis represents the amount of axial deviation (μm).

  The evaluation test was performed using signal light having a wavelength of 1.31 μm and an output of 10 dBm.

  As shown in FIG. 6A, according to the optical element of the first embodiment, a 1 dB down tolerance could be obtained with an axis deviation in the range of ± 3 μm. The maximum value of the coupling efficiency was -12 dB.

  As shown in FIG. 6B, according to the optical element of the second embodiment, a tolerance of 1 dB down can be obtained with an axis deviation amount in the range of ± 3.3 μm. The maximum value of the coupling efficiency was −9 dB.

  As described above, according to the optical element of the present invention, an optical signal can be incident from the upper surface side of the optical element. Even if an optical signal is incident from the upper surface side of the optical element, sufficient coupling efficiency can be obtained.

  The optical element of the present invention is suitable for optical coupling between optical devices used in an optical communication system.

FIG. 1A is a schematic view of the optical element as viewed from the upper surface side, and FIG. 1B is a schematic view showing a cut surface taken along the dashed line II ′ shown in FIG. FIG. 1C is a schematic view showing a cut surface taken along the dashed line II-II ′ shown in FIG. 2A, 2 </ b> B, and 2 </ b> C are schematic views illustrating a cut surface of a structure that is being manufactured in order to explain the manufacturing process of the optical element. FIG. 3 is a schematic diagram following FIG. FIG. 4A is a schematic plan view of the optical element as viewed from the upper surface side, and FIG. 4B is the same position as the one-dot chain line II ′ shown in FIG. It is the schematic which shows the cut surface which cut | disconnected. FIG. 5 is a schematic diagram of an evaluation system. 6A and 6B are tolerance curves showing the evaluation results.

Explanation of symbols

10: Optical element 20: Substrate 20X: Recessed region 20Xa: Exposed region 22: Underlayer 22a: Underlayer first side surface 22b: Underlayer second side surface 22c: Bottom surface 24: Clad layer 24a: Clad layer first side surface 24b: Clad layer second side surface 24c: remaining region 24X: upper surface 26: optical waveguide 26a: first end surface 26b: second end surface 26X: optical waveguide forming layer 26Y: precursor optical waveguide 28: concave portion 28a for mirror portion formation: reflective side surface 28b: Opposite side surface 30: Mirror part 30X: Mirror part forming region 40: Buried part 50: Recessed resist pattern 50a: Resist recessed part 60A: First fiber 60Aa: First exit end 60B: Second fiber 60Ba: Incident end 60Bb : Second exit end

Claims (13)

A substrate having a base layer and a clad layer provided on the base layer and having a flat upper surface;
An optical waveguide provided with at least one end face in the upper surface;
A reflective side surface provided with a mirror part that is a concave part for forming a mirror part and has a depth extending from the upper surface of the substrate to the thickness of the substrate, and reflecting the incident signal light, and the reflective side surface An optical element comprising: a concave portion for forming the mirror portion that has a facing side surface that is opposed to the end surface of the optical waveguide.   The end surface of the optical waveguide is inclined with respect to a plane perpendicular to the upper surface, and is an inclined plane that allows signal light to enter the mirror part or receive signal light reflected from the mirror part. The optical element according to claim 1.   The optical element according to claim 1, wherein the optical waveguide is a thin-line silicon optical waveguide extending on the upper surface.   The optical element according to claim 1, wherein the base layer is a silicon layer, and the cladding layer is a silicon oxide layer.   The optical element according to claim 1, wherein the mirror part is provided as a gold thin film.   The end face of the optical waveguide and the mirror part are integrally covered to embed the concave part for forming the mirror part, and a buried part having a refractive index smaller than that of the optical waveguide and larger than that of air is further provided. The optical element according to claim 1, wherein the optical element is provided.   The optical element according to claim 6, wherein the embedded portion is made of an epoxy resin. Preparing a substrate having a base layer, a clad layer provided on the base layer, and an optical waveguide forming layer provided on the clad layer;
Patterning the optical waveguide forming layer to form an optical waveguide extending in the middle of the cladding layer with one end face; and
Etching the region part on the side facing the one end face of the cladding layer exposed outside the optical waveguide to expose the foundation layer;
Covering the upper surface side of the substrate and forming a resist layer having a resist recess on the upper side of the exposed region of the base layer;
Transferring the shape of the resist concave portion to the underlayer, and forming a mirror portion forming concave portion having a reflective side surface and an opposite side surface facing the reflective side surface;
And a step of forming a mirror part in a mirror part forming region set on the reflection side surface.   9. The step of forming the recess for forming the mirror part forms an end surface of the optical waveguide into an inclined plane that is inclined with respect to a plane perpendicular to the upper surface of the cladding layer. Of manufacturing the optical element.   The step of forming the mirror portion is a step of depositing a gold thin film only on the mirror portion forming region using a resist pattern for forming the mirror portion exposing the mirror portion forming region. The manufacturing method of the optical element of 8 or 9.   11. The method according to claim 8, further comprising a step of forming an embedded portion that integrally covers the end face of the optical waveguide and the mirror portion and embeds the concave portion for forming the mirror portion. A method for manufacturing an optical element.   12. The optical system according to claim 11, wherein the step of forming the embedded portion is a step of forming the embedded portion with a material having a refractive index lower than that of the optical waveguide and higher than that of air. Device manufacturing method.   The method of manufacturing an optical element according to claim 12, wherein the manufacturing process of the embedded portion is performed using the material as an epoxy resin.

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