JPH1172635A - Optical device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical device capable of easily optically coupling various kinds of optical elements with low loss by providing the device with a core diameter-reducing region where the core diameter of a waveguide core is reduced toward both ends of >=1 opening groove into which the optical elements are packaged. SOLUTION: This device has the opening groove 6 where the optical elements are disposed between a light incident side core and light exit side core constituting the waveguide core 4. The core diameter facing the optical element on the light incident side core is made smaller than the core diameter of the light incident end 4a of the light incident side core and the core diameter facing the optical element on the light exit side is made smaller than the core diameter at the light exit end 4b of the light exit side core in such a manner that the mode field diameter of the guided light transmitted through the optical element is made wider than the mode field diameter of the guided light at the light exit end 4b of the light exit side core. The opening groove 6 may be disposed in a plurality. More adequately the opening groove 6 is provided with a mode field expanding part near the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid mounting of a bulk type optical element used for an optical communication device, an optical recording device, an optical sensor, and the like, and a laser diode, an optical waveguide, an optical fiber, and the like. In particular, the present invention relates to an optical device such as a waveguide for hybrid mounting and a method for manufacturing the same, which can be suitably used for a laser module used in an optical communication device.

[0002]

2. Description of the Related Art Conventionally, optical devices such as optical isolators, polarizers, various filters, and attenuators have been known. Recently, in addition to such bulk-type conventional optical components, waveguide-type optical components have been known. Has appeared a lot. However, since the dimensional tolerance of waveguide formation is severe and the wavelength dependence is large, many of them have not been put to practical use. Bulk-type components and some waveguide-type components, optical fibers, optical active At present, devices are used in a mixed state.

FIG. 6 shows a conventional optical device having optical fibers connected to both ends, and is a cross-sectional view of a pigtail type bulk component J1. As shown in FIG. 6, an optical element 52 such as an optical isolator, a filter, an attenuator, and a polarizer is housed inside the package 51. The light emitted from the optical fiber 53a is collimated by the lens 54a, passes through the optical element 52, and then returns to the lens 5a.
The light is condensed at 4b and is incident on the optical fiber 53b.

[0006] As shown in FIG. 7 (b), as a bulk component similar to FIG.
There has also been proposed an optical device J2 in which the mode field diameter of the end faces of 1a and 61b is enlarged to sandwich the optical component 62.

As shown in FIG. 7A, a predetermined area of the optical fiber 61 is heated and the core 6 of the optical fiber 61 is heated.
1C is obtained by diffusing a dopant such as Ge doped in 1c to widen a diffusion region of the dopant and reduce a difference in refractive index. As a result, the mode field diameter is increased while maintaining the single mode.
Then, the optical fiber 61 is fixed to the V-groove substrate 63, and then, after forming an opening 65 in which a part of the V-groove substrate 63 is cut at the center of the core enlarged portion 64, the optical element 62 is inserted.

As shown in FIG. 8, an optical isolator J3 having a structure in which an opening 82 is provided in the middle of a waveguide 80 and a bulk optical element 81 is installed in the opening 82 has been proposed (see FIG. 8). For example, see Patent Publication No. 2586606). This is because the opening 8 is wider than the width of the optical element 81.
2 and the optical element 81 and the exposed end 83 of the opening 82
The optical element 81 is installed so that there is a gap between the two layers, and the gap is filled with a photocurable film 84, and the photocurable film 84 is irradiated with ultraviolet rays UV through a waveguide in contact with each film. Things.

The photocurable film 84 is made of, for example, a material in which polymethacrylic acid is used as a base material and to which styrene, benzyl methacrylate, and the like are added, and has a hemispherical shape according to the shape of ultraviolet rays emitted radially from the waveguide. The base material is polymerized with styrene or benzyl methacrylate, and then immersed in methyl alcohol to remove the unpolymerized additive, thereby forming a hemispherical lens 85 having a large refractive index only in the light receiving portion.

[0008]

However, the conventional pigtail type component as shown in FIG. 6 requires the precision of the position adjustment of the lens and the optical fiber, and takes a very long time to assemble. In addition, since the adjustment becomes more difficult as the optical path length becomes longer, there are restrictions on the thickness of the optical element inserted therebetween and the number of optical elements. Furthermore, since each optical element is fixed to a package after being attached to a fixing holder, the number of components is very large, which also increases the cost and the complexity of assembly.

In the case of a core-expanded fiber as shown in FIG. 7, if the core diameter of a single-mode optical fiber is simply increased, a higher-order mode is excited and the transmission characteristics are degraded. Therefore, it is necessary to adjust the refractive index difference so that r × (D) ^1/2 becomes constant even when the core diameter changes so as not to excite the higher-order mode. Here, r is the core radius, D is the relative refractive index difference, and r × (D) ^1/2 is a numerical value proportional to the normalized frequency.

Further, since it is difficult to adjust the refractive index according to the change in the core diameter, a method of thermally diffusing the dopant of the core of the single mode optical fiber is used. In this method, the dopant in the core is diffused into the clad by heat, and the core diameter is increased and the refractive index is reduced at the same time, so that r × (D) ^1/2 is kept constant.

[0011] Further, in this method, although there is no axial deviation between the fibers, it is difficult to uniformly heat the enlarged portion of the core, so that a region long in the traveling direction cannot be produced. Further, since the core enlarged portion is local and short, it is not suitable for inserting a thick element or a plurality of elements.

Further, the biggest problem is that the heat diffusion process takes a long time. For example, in order to reduce the core diameter of 8 μm to 40 μm, it takes several tens of hours depending on the heat source, the heating range, the temperature and the like. It costs. Thus, it is not suitable as an inexpensive and easy-to-make process.

In the method of forming the resin lens shown in FIG. 8, it is necessary to control the curvature of the hemispherical lens 85 in accordance with the width of the opening for mounting the optical element, and to obtain the optimum light coupling. However, curvature control is not easy. Further, the number of steps such as resin filling, photosensitization, and treatment with methyl alcohol increases, and the number of members also increases. Further, in some semiconductor laser modules, resin may not be used in the package in order to avoid deterioration of the resin and release of gas from the resin for a long period of time.

That is, hybrid mounting of a waveguide-type optical component such as an optical fiber, a laser diode, or an optical waveguide and a bulk-type optical component is a very important industrial issue, but there is no suitable mounting structure.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide a very excellent optical device capable of optically coupling various optical elements easily and with low loss, and a method of manufacturing the same. More specifically, it is an object of the present invention to provide an optical device having a structure in which a mode field is easily expanded without exciting a higher-order mode, an optimal structure and dimensions for optical coupling with low loss, and a method of manufacturing the same. And

[0016]

In order to solve the above-mentioned problems, in the optical device of the present invention, an optical element is disposed between a light incident side core and a light exit side core constituting a waveguide core. With the opening groove, the mode field diameter of the guided light transmitted through the optical element is made larger than the mode field diameter of the guided light at the light incident end of the light incident side core and the light exit end of the light exit side core. The core diameter of the light incident side core facing the optical element is smaller than the core diameter of the light incident end of the light incident side core, and the core diameter of the light emitting side core facing the optical element is light emitting side. It is characterized in that the diameter is smaller than the core diameter of the light emitting end of the core. Note that a plurality of the above-described opening grooves may be provided. More preferably, a mode field expanding portion is provided near the opening groove, and the mode field diameter ω of the mode field expanding portion is ω ² > 7.85 × 10 ^−4.
λ / (πn) is satisfied.

The gap width G of the opening groove satisfies the following expression. G <0.25πnω ² / λ
(Where, λ: wavelength of guided light, n: refractive index of optical element,
ω: mode field radius of guided light). More preferably, G <0.08πnω ² / λ.

Further, an optical element is provided in an opening groove of the optical device, and an optical fiber is provided at a light input end and / or a light output end of the waveguide core.

A non-reciprocal rotator for rotating the polarization plane non-reciprocally by a predetermined angle and a reciprocal rotator for rotating the polarization plane reciprocally by a predetermined angle are arranged in series in the opening groove. The polarization mode of incoming and outgoing guided light is selectively passed.

Further, the method for manufacturing an optical device according to the present invention comprises:
Forming a trapezoidal sub-cladding layer in the center of the substrate, forming a waveguide layer covering the sub-cladding layer on the substrate, and patterning the waveguide layer into a predetermined shape to form a waveguide core layer. Forming, forming a main cladding layer on the waveguide core layer, and forming an opening groove traversing the waveguide core layer and in which the optical element is provided.

The mode field diameter means the width of the light beam where the light intensity is 1 / e ^{2 of the} peak value.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 2 (i), an optical waveguide body K, which is an optical device of the present invention, forms a waveguide core 4 and is located on the light incident side (light incident side core).
One or more apertures in which an optical element is mounted in a direction crossing the waveguide core 4 between the light incident end 4a of the optical waveguide and the light exit end 4b of the core located on the light exit side (light exit side core). A core diameter reduction region A in which the core diameter of the waveguide core 4 is reduced toward the both ends 6a and 6b of the opening groove 6;
(Taper portion 3, core diameter minimum region 2). That is, the core diameter is extremely small at both ends 6a and 6b of the opening groove 6 (region B). That is, the mode field diameter of the guided light transmitted through the optical element is smaller than the light incident end 4a.
The core diameter of the light incident side core facing the optical element is made smaller than the core diameter of the light incident side core of the light incident side core so as to be wider than the mode field diameter of the guided light at the light emitting end section 4b; The core diameter of the light emitting side core facing the optical element is
It is characterized in that the diameter of the light exit side core is smaller than the diameter of the core at the light exit end. The mode field enlarged portion M (FIG. 2 (h)) is formed by combining the core diameter minimum region 2 and the opening groove 6.
The core size means the thickness of the core in a slab type waveguide using a thin film waveguide core, and means the diameter of the core when the core is circular. When the core is rectangular, it means the length of the short side, and when the core is square, it means the length of one side.

Here, a suitable gap width G of the opening groove 6 is set.
G <0.25πnω ² / λ (where λ: wavelength of guided light, n: refractive index of optical element,
ω: mode field radius of guided light).

This means that, when there is a gap between the two waveguide cores 4 filled with a substance having a refractive index of n, the gap width at which the power transmission coefficient is greater than 0.794 (the diffraction loss is less than 1 dB) Is calculated.

More preferably, G <0.08πnω
² / λ. In this case, it can be obtained by calculating a gap width at which the power transmission coefficient is greater than 0.975 (diffraction loss is less than 0.1 dB).

In general, when there is a gap filled with a substance having a refractive index of n between two opposing waveguides, the gap width is G, the power transmission coefficient is T, the wavelength of the guided light is λ, and the mode field radius is Let ω be the relationship of the following equation:

T = (1 + ((2λG) / (πnω ² )) ² ) ^-1 The preferred opening width G is obtained by substituting 0.794 into T in the above relational expression, and 0.794 <(1 + (( 2λG) / (πnω ² )) ² )
^-1 was obtained by modifying this equation.

When G is less than 100 μm, the opening groove 6
The optical element to be inserted into the
Since it is about 0 μm or less, it is very limited, or it is easily broken and is difficult to handle, so that it cannot be used practically. Therefore, in the case of industrial use, it is necessary to define a suitable range of the mode field diameter from the practical gap width G, and set the mode field diameter ω to ω ² > 7.85 × 10 ^−4. λ / (π
n). This means that the gap width G is 200 μm or more,
It is calculated as a diffraction loss of less than 1 dB.

As shown in FIG. 9, a plurality of open grooves,
For example, by providing the opening grooves 22 and 23 and arranging the optical elements 24 and 25 in the respective opening grooves 22 and 23 as shown in FIG. 10, the total width of the plurality of opening grooves (= G
1 + G2) is preferable because the diffraction loss is reduced as compared with the case where the optical element is provided in one gap having a gap width equal to 1 + G2).

This is because, as is apparent from the graph of FIG. 4, the diffraction loss increases sharply as the facing distance increases. For example, referring to FIG.
When the mode field diameter is 31 μm, the mode field diameter is 30 μm, and the gap width of the opening groove is 600 μm, the diffraction loss is 1.17 dB. However, when the gap width of the opening groove is 300 μm, the diffraction loss is 0.32 dB, and there are two 300 μm gaps. Even so, the total diffraction loss is 0.64 dB. this is,
This shows that even if the total element thickness is the same, the loss is smaller when the element is divided. In addition, by providing the mode field enlarging portion of 1 mm or more in the direction parallel to the traveling direction of light, a relatively thick element can be inserted, and a plurality of opening grooves can be easily formed. By dividing the gap with a small gap width into a plurality of pieces as described above, the total coupling loss can be suppressed to be lower than the case where one gap is provided.

Next, a method of manufacturing the optical waveguide body K will be described. First, as shown in FIGS. 2A and 2B,
For example, a taper clad 13 is formed in a trapezoidal shape with a predetermined thickness (for example, a thickness of about 7.5 μm) on a substrate 1 such as quartz (SiO ₂ ) by a film forming method such as a CVD method. I do. This can be made relatively easily by floating the mask from the substrate 1 by several tens μm to several hundred μm to form a film. The degree of taper is controlled by the floating distance.

Next, as shown in FIG.
A waveguide layer 14 whose relative refractive index is about 0.3% higher than that of SiO ₂ by doping iO ₂ with Ge or the like has a thickness of 8 μm from the substrate 1 and a thickness of 0.5 μm from the taper clad 13.
m is formed by a CVD method or the like.

Next, as shown in FIG.
A mask 15 is formed on 4. Here, the mode field enlarging portion M narrows the width D1 to 0.5 μm, and the width D2 at both ends is 8 μm.

Next, as shown in FIG.
By etching by (Reactive Ion Etching), the waveguide core 4 is formed by removing the waveguide side portion, and the mask 15 is removed as shown in FIG.

Next, as shown in FIG.
The waveguide core 4 is covered with SiO ₂ having the same refractive index as the tapered clad 13 as the main clad layer 5. Here, FIG. 2H illustrates a state in which the waveguide core 4 is seen through.

Finally, as shown in FIG. 2I, an opening groove 6 for fixing the optical element is ground by, for example, a dicing saw.

The above manufacturing method is different from the case of manufacturing a normal straight (linear) waveguide in FIGS.
Only the process of (d) is different, and the waveguide body can be manufactured by slightly changing the normal manufacturing process.

That is, in FIG. 2B, only the formation of the tapered cladding 13 is increased, but another apparatus can be prepared because it can be manufactured by the same apparatus (for example, a CVD apparatus) as a series of other film formation. There is no trouble of setting or setting, and the increase of the manufacturing time is slight. FIG.
In (d), the process is not complicated because the mask pattern is different from the straight waveguide.

Next, FIG. 4 shows the light coupling efficiency when two waveguides are opposed to each other. The horizontal axis is the facing distance between the waveguides, and corresponds to the width B of the opening groove 6 in the present invention. The vertical axis indicates light loss. The mode field assumes a Gaussian distribution, the wavelength is 1.31 μm, and the refractive index in the open groove is air (n = 1). The broken line indicates the case of a waveguide having a mode field diameter W of 10 μm, and indicates that if the width of the facing space (gap width of the opening groove 6) becomes 500 μm, the loss becomes 12 dB or more. However, when the mode field diameter is enlarged to 40 μm (solid line), the light loss is 0.3 d even when the facing distance is 500 μm.
It can be seen that it can be reduced to about B.

FIG. 5 shows the relationship between the thickness of the waveguide layer (corresponding to the core diameter) and the mode field diameter in a slab-type waveguide as a measure of the relationship between the core diameter and the mode field diameter. As is clear from FIG. 5, the mode field diameter increases as the thickness of the waveguide layer increases, but the mode field diameter can be increased even when the thickness of the waveguide layer decreases at a thickness of about 4 μm. If the relative refractive index difference does not change, a higher-order mode will occur if the core diameter increases, and the transmission characteristics will deteriorate, but if the waveguide core is reduced, the higher-order mode will not occur, so the relative refractive index will not occur. There is no need to change the difference.

As described above, there has been no proposal of hybrid mounting in which waveguides each having a reduced waveguide core are opposed to each other to realize low-loss coupling. Since the length of the mode field expanding portion (= the two core minimum portions 2 + region B) including the bulk mounting portion can be freely designed, a plurality of bulk optical elements having an arbitrary thickness and an optical fiber or an optical active element can be used. Can be easily combined. It is also possible to prepare the mode field enlarging portion in advance with a length exceeding several mm, and to make it universally applicable, even if the thickness and number of elements to be inserted are not predetermined.

In the above mounting structure, a bulk non-reciprocal polarization rotator and a reciprocal rotator are provided in the groove for mounting the element, and a metal or a metal is provided outside the region where the core diameter decreases around the groove. A waveguide-type mode splitter can be formed by loading a composite thin film of an anisotropic dielectric, metal, or dielectric, and can be used as a surface-mounted optical isolator that is an optical device. A small surface-mount optical isolator can be easily realized.

[0043]

EXAMPLES Next, specific examples will be described.

Example 1 FIG. 1 is a perspective view of an optical device in which optical fibers 8, 8 are optically coupled to a light input end 4a and a light output end 4b of an optical waveguide body K as an optical device. Show. 8a is a fiber core. As shown in FIG. 1, on a quartz substrate 1, a mode field enlarged portion having a substantially square cross section and a core size of 0.5 μm (gap width L3 of the opening groove 6: 0.5 mm, each core having a square shape of 15 mm) is provided. The length L2 of the minimum diameter part 2: 1 mm) is 2.5 m
m, a taper portion 3 (length L1) on each side of 5 mm,
The light incident portion 4a and the light emitting portion 4b each having a core size of 8 μm and having a substantially square cross section are each set to have a length of 6.25 mm.
The core shape was formed by a CVD method and an etching method.
The waveguide core 4 has a relative refractive index difference of 0.3% with respect to the quartz substrate 1, and the refractive index does not change over the entire core. A quartz cladding layer 5 was formed thereon.

The mode field diameter is 0.5 for the core size.
The mode field diameter is about 30 μm in the μm mode field expanding section, and about 10 μm in the light input / output sections 4 a and 4 b.

An optical fiber 8 was connected to the light input / output ends 4a and 4b by a butt joint. Reference numeral 9 denotes a substrate having a V-groove for aligning and fixing the surface mounting waveguide 7 and the optical fiber 8, and has a V-groove 10 for positioning and holding the fiber.

In the enlarged mode field portion, a gap width of the opening groove 6 is cut to about 500 μm by a dicing saw, and a wavelength filter 12 made of a dielectric multilayer film is inserted and fixed therein. The dielectric multilayer film is, for example, a combination of ZnS and MgF _{2 or} a combination of TiO ₂ and SiO ₂ .

Light incident on the light input end 4a and the light output end 4
When the light loss was measured for the light emitted from b,
Diffraction loss at a gap width of 500 μm is 1.31 μm in wavelength
Was about 0.85 dB.

The wavelength filter may be fixed with solder or the like. In this case, both surfaces of the wavelength filter 12 are provided with an AR coating (anti-refrection coating) for air.
It is necessary to provide an air gap. Further, both surfaces of the wavelength filter 12 are coated with an AR coating for an adhesive, and the gap at the time of insertion of the wavelength filter 12 is adjusted in refractive index (refractive index: about 1.6), a thermosetting epoxy adhesive. And the like. Although not shown in FIG. 1, the package is finally sealed in a package for improving reliability.

Example 2 FIG. 3 shows an optical isolator S2 which is an optical device using the mounting structure of the present invention. Substrate 1,
The clad 5 is made of quartz glass, and the waveguide core 4 is made of quartz glass doped with Ge or the like to increase the refractive index by 0.3%. The core diameter of the mode field expansion section is 0.5 μm
And the mode field diameter is about 30 μm.
a and 4b have a core diameter of 8 μm and a mode field diameter of about 1
It was set to 0 μm.

An Al thin film is formed on the core 4 so as to sandwich the opening groove 6 for mounting the optical element, and a first polarization mode splitter 16a and a second polarization mode splitter 16b are formed.
Was formed.

A non-reciprocal polarization rotator 17 made of a magnetic garnet having a thickness of about 400 μm and a 90 μm thick
A reciprocal polarization rotator 18 made of m-quartz was provided, and these optical elements were arranged in tandem.

The C axis of the crystal has an angle of 22.5 degrees from the horizontal plane. A non-reciprocal polarization rotator made of a magnetic garnet or the like may be called a Faraday rotator, and a reciprocal polarization rotator made of a birefringent material such as quartz may be called a half-wave plate.

Next, the operation of the surface mount type optical isolator will be described. Here, when looking in the direction from the entrance 4a to the exit 4b, the clockwise direction is plus (+) and the reverse is minus (-).

The light 20 incident on the incident part 4a becomes only TE polarized light by the first polarization mode splitter 16a, and the mode field of the light is expanded by the mode field expanding part. Then the plane of polarization in the non-reciprocal polarizing rotator 17 is rotated ° + 45, reciprocal polarization rotator 18 in rotated -45 degrees, passes through the second polarization mode splitter 16b as TE polarized light.

The incident light 21 in the opposite direction becomes TE-polarized light by the second polarization mode splitter 16b, and the reciprocal polarization rotator 1
8, the polarization plane is rotated by -45 degrees, and the non-reciprocal polarization rotator 17 is rotated.
Then, the polarized light is further rotated by -45 degrees to become TM polarized light. This light is removed by the first polarization mode splitter 16a.

According to the surface mount type optical isolator 12, excellent characteristics such as insertion loss of 1 dB or less and isolation of 36 dB or more could be easily realized.

The substrate 1 may be made of a polymer material other than quartz glass, another optical glass, or a semiconductor. Furthermore, as a polarization mode splitter, besides Al, Cu or A
g, which absorbs TM polarized light, which is loaded with quartz or rutile and emits one mode using the anisotropy of the refractive index, There are those that branch to modes. Therefore, contrary to the embodiment, it is possible to remove the TE polarized light and transmit only the TM polarized light.

Further, it is possible to provide a plurality of opening grooves 6 and mount an optical isolator and a filter or two optical isolators at the same time. For example, according to the graph of FIG. 4, when two optical elements each having a thickness of 300 μm are inserted into a waveguide, if a groove of 600 μm is formed at a mode field enlarging portion having a mode field diameter of 30 μm, the diffraction loss at the groove is reduced. Although it is 1.17 dB, it can be seen that when two 300 μm grooves are formed, the total diffraction loss is only 0.64 dB. That is, even if the total of the optical path lengths is the same, if the element can be divided, the loss at the time of mounting the element can be reduced. This is a great advantage that cannot be realized with a lens.

Example 3 Another shape and manufacturing method of the optical waveguide K as an optical device will be described. First, FIG.
As shown in (a), (a ′) and (b) and (b ′), for example, Ge is doped into SiO ₂ by, for example, CVD on a substrate 1 made of, for example, quartz (SiO 2). The waveguide layer 14 having a relative refractive index higher than that of SiO ₂ by about 0.3%
It is formed so that the thickness from the substrate 1 becomes 8 μm.

Next, as shown in FIGS. 11C and 11 C, a mask 15 is formed on the waveguide layer 14. here,
The mode field enlarging portion M narrows the width D1 to 0.5 μm, and the width D2 at both ends is 8 μm.

Next, as shown in FIGS. 11 (d) and 11 (d '), the waveguide side is removed by etching by RIE to form the waveguide core 4, and as shown in FIGS. 11 (e) and (e'). Then, the mask 15 is removed.

Next, as shown in FIGS. 11F and 11F, the central portion of the waveguide core 4 has a predetermined thickness (for example, 0.5%).
Etching is performed by RIE to reduce the thickness. The light input / output end portions 4a and 4b are connected by a gentle taper. This can be easily formed by floating the mask from the waveguide core 4 by several tens μm to several hundred μm and performing etching. Further, the degree of taper is controlled by the floating distance.

Next, as shown in FIGS. 11 (g) and (g ′), the waveguide core 4 is covered with SiO ₂ having the same refractive index as the substrate 1 as the main cladding layer 5. Here, FIGS. 11 (g) and 11 (g ') show a state where the waveguide core 4 is seen through.

[Example 4] Further, another shape of the optical waveguide K,
A manufacturing method will be described.

First, FIGS. 12 (a), (a '), and (b)
As shown in (b '), the taper clad 13 is formed on the substrate 1 such as quartz (SiO ₂ ) by a film forming method such as a CVD method.
Is formed in a trapezoidal shape with a predetermined thickness (for example, a thickness of about 3.75 μm) to form a sub-cladding layer. This can be relatively easily achieved by forming a film by floating the mask from the substrate 1 by several tens μm to several hundred μm. Further, the degree of taper is controlled by the floating distance.

Next, as shown in FIGS. 12 (c) and 12 (c '), the waveguide layer 14 having a relative refractive index about 0.3% higher than that of SiO ₂ by doping SiO ₂ with Ge or the like is formed on the substrate. It is formed by a CVD method or the like so that the thickness from 1 is 8 μm and the thickness from the tapered clad 13 is 7.75 μm.

Next, as shown in FIGS. 12D and 12D, a mask 15 is formed on the waveguide layer 14. here,
The mode field enlarging portion M narrows the width D1 to 0.5 μm, and the width D2 at both ends is 8 μm.

Next, as shown in FIGS. 12E and 12E, the waveguide side portion is removed by etching by RIE to form the waveguide core 4, and as shown in FIGS. 12F and 12F. Then, the mask 15 is removed.

Next, as shown in FIGS. 12 (g) and 12 (g '), the central portion of the waveguide core 4 has a predetermined thickness (for example, 0.5 μm).
(Thickness of about m) Etching by RIE so as to be thin. The light input / output end portions 4a and 4b are connected by a gentle taper. This can be easily formed by floating the mask from the waveguide core 4 by several tens μm to several hundred μm and performing etching. Further, the degree of taper is controlled by the floating distance.

Next, as shown in FIGS. 12H and 12H, the waveguide core 4 is covered with SiO ₂ having the same refractive index as the substrate 1 as the main cladding layer 5. Here, FIG. 12H shows a state where the waveguide core 4 is seen through.

The shape of the waveguide can be a shape suitable for an optical element to be inserted into the opening groove 6. In the optical waveguide body K shown in FIG. 2, since the mode field expanding portion is biased upward, the mode field is also biased upward. When forming the optical isolator shown in FIG. This is preferable because light interaction easily occurs. Further, since the optical waveguide body K shown in FIG. 12 has high symmetry, light loss at the tapered portion is small and versatility is high.

[0073]

As described above, according to the present invention, the following excellent effects can be obtained.

Parts for holding optical elements for optical alignment are not required, so that the number of parts, the volume, etc. can be reduced, and the assembling work can be simplified and the size can be reduced.

[0086] Since only one design (product) can support mounting of optical elements of various thicknesses and numbers,
Multiple optical elements can be easily and simultaneously mounted. Further, by dividing the mounting position of the optical element, the loss at the time of mounting can be reduced, and the tolerance of the opening groove forming position is very large.

Since there is almost no space propagating portion in the light passing portion, a change in characteristics due to a change in environment is unlikely to occur.

When the core is reduced, no higher-order mode is generated, so that it is not necessary to change the relative refractive index difference, thereby facilitating the production of the mode field expanding portion.

A special manufacturing apparatus, additional members, and labor are not required just by slightly changing the process of manufacturing a normal linear waveguide, and the manufacturing can be easily performed with almost no change in the manufacturing time.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an optical waveguide body for surface mounting and an optical device according to the present invention.

FIG. 2 is a perspective view schematically illustrating a manufacturing process of an optical waveguide according to the present invention.

FIG. 3 is a perspective view illustrating an optical isolator according to the present invention.

FIG. 4 is a graph illustrating a relationship among a mode field radius, a facing distance, and a diffraction loss.

FIG. 5 is a graph illustrating a relationship between a waveguide layer thickness and a mode field diameter of a slab waveguide.

FIG. 6 is a cross-sectional view showing a conventional pigtail type component.

FIGS. 7A and 7B are partial cross-sectional views illustrating a mounting method using a conventional core-expanded fiber.

FIG. 8 is a partial sectional view showing a conventional optical isolator.

FIG. 9 is a perspective view of an optical device according to the present invention.

FIG. 10 is a perspective view of an optical device according to the present invention.

11 (a) to 11 (g) are top views showing another manufacturing step of the optical waveguide according to the present invention, and FIGS.
Is a side view thereof.

12 (a) to 12 (h) are top views showing other steps of manufacturing the optical waveguide according to the present invention, and are (a ′) to (h ′).
Is a side view thereof.

[Explanation of symbols]

 1: substrate 4: waveguide core 4a: light incident end 4b: light emitting end 5: waveguide layer (cladding layer) 6: open groove K: optical waveguide body (optical device) S1: optical device S2: optical isolator

Claims (5)

[Claims] 1. An optical device according to claim 1, wherein an optical element is provided between the light incident side core and the light output side core, and the mode field diameter of the guided light transmitted through the optical element is reduced. The core diameter of the light incident side core facing the optical element is set to be larger than the mode field diameter of the guided light at the light incident end of the light incident side core and the light exit end of the light exit side core. The diameter of the light incident side core is smaller than the diameter of the light incident end, and the diameter of the light exit side core facing the optical element is smaller than the diameter of the light exit end of the light exit side core. An optical device, comprising: 2. The optical device according to claim 1, wherein a gap width G of the opening groove satisfies the following expression. G <0.25πnω ² / λ (where λ: wavelength of guided light, n: refractive index of optical element,
ω: mode field radius of guided light) 3. An optical element is disposed in an opening groove of the optical device, and an optical fiber is disposed on a light incident end and / or a light exit end of the waveguide core. 2. The optical device according to 1. 4. A non-reciprocal rotator for rotating the polarization plane non-reciprocally by a predetermined angle and a reciprocal rotator for rotating the polarization plane reciprocally by a predetermined angle are arranged in series in the opening groove. 2. The optical device according to claim 1, wherein the polarization mode of the guided light entering and leaving the groove is selectively passed. 5. A step of forming a trapezoidal sub-cladding layer at the center of a substrate, a step of forming a waveguide layer covering the sub-cladding layer on the substrate, and patterning the waveguide layer into a predetermined shape. Forming a waveguide core layer, forming a main clad layer on the waveguide core layer, and forming an opening groove traversing the waveguide core layer and in which an optical element is provided. An optical device manufacturing method including: