JP7215161B2 - Optical waveguide evaluation method and optical module manufacturing method - Google Patents

Description

The present invention relates to an optical waveguide evaluation method and an optical module manufacturing method.

In an optical module including components of an optical waveguide and an optical element, a mirror having an inclined surface formed in the core of the optical waveguide converts the optical path of the core to couple with the optical element. Therefore, properties such as the angle of the inclined surface and the surface precision affect the loss in the optical module. Therefore, there is a demand for a method of evaluating the properties of the inclined surface in a short time.

Patent Document 1 discloses a method for inspecting an optical waveguide having a linear core and a light reflecting surface formed on the core. After the light is reflected from the optical waveguide, the emitted light is imaged and the luminance on the image is measured. A method for evaluating the degree of curvature of a light reflecting surface is disclosed. That is, in this method, the degree of curvature of the light reflecting surface is evaluated using the fact that there is a correlation between the degree of curvature of the light reflecting surface and the integrated area value.

JP 2017-111025 A

As described above, in the method described in Patent Literature 1, the number of pixels whose luminance is equal to or higher than a threshold value on a captured image is used as an area integrated value, and the degree of curvature of the light reflecting surface is calculated based on this area integrated value. I am evaluating. In other words, the integrated area value corresponds to an area that satisfies a predetermined luminance in an image obtained by picking up emitted light.

By the way, the evaluation based on such an area integrated value may not be able to achieve the purpose of suppressing the coupling loss between the optical waveguide and the optical element via the light reflecting surface. For example, there may be a case where the area integrated value is sufficiently large, but pixels with brightness equal to or higher than the threshold are scattered within the image. In such a case, depending on the optical coupling structure of the optical module, it may cause the coupling loss of the optical waveguide to deteriorate.

However, in the evaluation based on the area integrated value as described above, there is a problem that the distribution of the pixels whose brightness is equal to or higher than the threshold is not taken into consideration no matter how it is distributed.
Furthermore, since the luminance itself does not include information on the angular distribution of the light reflecting surface, there is a problem that it is insufficient as an evaluation for optimizing the mutual alignment between the light reflecting surface and the optical element. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an evaluation method for an optical waveguide that can easily evaluate an optical waveguide while taking into account the distribution state of the angles of reflected light at an optical path changing portion, and an optical module with a small coupling loss between components. To provide a method for manufacturing an optical module that can be manufactured well.

Such objects are achieved by the present invention of the following (1) to (6) .
(1) A method for evaluating an optical waveguide comprising a linearly extending core portion and an inclined surface for converting the optical path of the core portion, comprising:
a step of making light incident on the core portion, receiving emitted light reflected by the inclined surface and emitted by a detection surface, and obtaining a luminance distribution curve of the emitted light in a predetermined direction within the plane of the detection surface;
a step of obtaining an angle distribution curve of the inclined surface by subjecting the luminance distribution curve to conversion using a conversion formula obtained in advance ;
evaluating the optical waveguide based on the angular distribution curve;
A method for evaluating an optical waveguide, comprising:

(2) The step of evaluating the optical waveguide includes:
In the angular distribution curve, obtain the length of the portion where the angular displacement is continuously within the threshold range,
The optical waveguide evaluation method according to (1) above, which is a step of evaluating the optical waveguide based on the length of the portion and the length of the component of the inclined surface in the predetermined direction.

(3) The optical waveguide evaluation method according to (2) above, wherein the optical waveguide is evaluated based on the shape of the portion of the angular distribution curve.
(4) The thickness of the core portion obtained from an image obtained by capturing the light emitted from the core portion after light is incident from the inclined surface is defined as the length of the component of the inclined surface in the predetermined direction. A method for evaluating an optical waveguide according to the above (2) or (3).
(5) The conversion formula is
After obtaining the profile of the inclined surface in advance, dividing the profile into minute sections and obtaining an angle for each section,
By plotting the angle of the section, an angle distribution curve for calculating the conversion formula is obtained,
At least one of a coefficient and an offset amount that minimizes the difference between the angular distribution curve for calculating the conversion formula and the luminance distribution curve of the emitted light obtained in advance for the same optical waveguide as the optical waveguide is obtained. The method for evaluating an optical waveguide according to any one of the above (1) to (4), which is a derived formula.

(6) A method for manufacturing an optical module including an optical waveguide and an optical element, which includes a linearly extending core portion and an inclined surface for converting the optical path of the core portion,
Light is incident on the core portion of the optical waveguide, emitted light reflected by the inclined surface is received by a detection surface, and a luminance distribution curve of the emitted light in a predetermined direction within the detection surface is obtained. process and
a step of obtaining an angle distribution curve of the inclined surface by subjecting the luminance distribution curve to conversion using a conversion formula obtained in advance ;
determining the position of a portion of the angular distribution curve where the angular displacement is continuously within the threshold range;
positioning the optical element with respect to the inclined surface of the optical waveguide based on the position of the portion;
A method of manufacturing an optical module, comprising:

According to the present invention, an optical waveguide can be evaluated while considering the distribution of angles in the optical path changing portion.

Moreover, according to the present invention, an optical module with small coupling loss between components can be efficiently manufactured.

1 is a perspective view showing an example of an optical waveguide used in an optical waveguide evaluation method according to an embodiment; FIG. FIG. 2 is a side view schematically showing an example of an apparatus used in the method of evaluating the optical waveguide shown in FIG. 1; It is process drawing for demonstrating the evaluation method of the optical waveguide which concerns on embodiment. It is a figure which shows the example of a two-dimensional luminance distribution. 5 is an example of a luminance distribution curve CL in the extension direction of the core portion obtained from the two-dimensional luminance distribution shown in FIG. 4; FIG. 3 is a diagram showing a profile PR of a mirror (inclined surface) obtained by a confocal laser microscope, and an angular distribution curve CA' derived from this profile PR. FIG. 7 is a diagram for explaining a method of acquiring the profile PR of the mirror shown in FIG. 6; FIG. It is a figure for demonstrating the procedure which converts the luminance distribution curve CL into the angle distribution curve CA. It is a figure for demonstrating an evaluation process. It is a figure for demonstrating the method of calculating|requiring the length b of the predetermined direction component of a mirror (inclined surface). It is an example of a brightness distribution curve CL different from that of FIG. It is process drawing for demonstrating the manufacturing method of the optical module which concerns on embodiment. It is a figure for demonstrating the manufacturing method of the optical module which concerns on embodiment. It is a figure for demonstrating the manufacturing method of the optical module which concerns on embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION The method for evaluating an optical waveguide and the method for manufacturing an optical module according to the present invention will now be described in detail with reference to the preferred embodiments shown in the accompanying drawings.

(Optical waveguide)
First, before explaining the method for evaluating an optical waveguide according to an embodiment, an example of an optical waveguide used for this evaluation method will be described.

FIG. 1 is a perspective view showing an example of an optical waveguide provided for an optical waveguide evaluation method according to an embodiment.

The optical waveguide 9 shown in FIG. 1 is a layered member capable of transmitting an optical signal. The optical waveguide 9 is a laminated body in which a clad layer 91, a core layer 93 and a clad layer 92 are laminated in this order from below.

As shown in FIG. 1 , the core layer 93 is provided side by side with the core portion 94 extending linearly and each core portion 94 . and a side cladding portion 95 having a lower refractive index.

Although the width and height of the core portion 94 are not particularly limited, they are approximately 1 to 200 μm. Also, the number of core portions 94 formed in the core layer 93 is not particularly limited, and is, for example, approximately 2 to 100 pieces.

In the optical waveguide 9, a mirror 97 is formed in the middle of the core portion 94, as shown in FIG. For example, the mirror 97 changes the propagation direction of the light incident on the core portion 94 from the light input/output surface 96 , so that the light can be extracted to the outside in the thickness direction of the optical waveguide 9 . For example, by providing optical components such as optical fibers and optical elements in accordance with the position of the mirror 97, the optical waveguide 9 and these optical components can be optically connected.

The mirror 97 is formed by processing the core portion 94 so as to be recessed in the middle thereof, and is formed by an inclined surface of a recessed portion 970 obtained thereby. Accurate evaluation of the performance of the mirror 97 is important because the performance of the mirror 97 greatly affects the reflection angle of the signal light, and thus the optical coupling efficiency between the optical waveguide 9 and the optical components.

The inclined surface constituting the mirror 97 is a flat surface continuously formed from the clad layer 92 through the core layer 93 to the clad layer 91, as shown in FIG. It is inclined with respect to the optical axis of the core portion 94 .

Note that the mirror 97 may be formed on the side clad portion 95 positioned on the extension line of the core portion 94 instead of in the middle of the core portion 94 .

The refractive index distribution of the optical waveguide 9 used for measurement is not particularly limited, and may be, for example, a so-called step index (SI) type distribution in which the refractive index changes discontinuously. It may be a so-called graded index (GI) type distribution that varies dynamically.

(Optical waveguide evaluation device)
Next, an example of an apparatus used for the evaluation method of the optical waveguide according to the embodiment will be described.

FIG. 2 is a side view schematically showing an example of an apparatus used in the method for evaluating the optical waveguide shown in FIG. 1. FIG. In FIG. 2, the horizontal direction is the X-axis direction, the vertical direction is the Z-axis direction, and the thickness direction of the paper is the Y-axis direction.

The evaluation apparatus 1 shown in FIG. It is provided with an actuator 13 that drives in the axial direction, and a control unit 14 that obtains the luminance distribution curve of emitted light on the image captured by the camera 12 and obtains the angular distribution curve. The evaluation apparatus 1 shown in FIG. 2 also includes a stage 15 that holds the optical waveguide 9 . Each part of the evaluation device 1 will be described below.

The stage 15 is a stand on which the optical waveguide 9 can be placed. The stage 15 shown in FIG. 2 has a plate shape. The stage 15 is composed of, for example, a flat plate made of metal, glass, ceramics, resin, or the like.

Further, an adhesive layer 151 may be provided on the upper surface of the stage 15 as necessary. The adhesive layer 151 can easily fix the optical waveguide 9 on the stage 15 . When the adhesive layer 151 and the optical waveguide 9 are in close contact with each other, the adhesive layer 151 follows the shape of the lower surface of the optical waveguide 9 . is filled with adhesive. Therefore, it is possible to reduce the optical influence of the unevenness in the captured image. Therefore, the adhesive layer 151 preferably has flexibility.

The stage 15 may have a function of transporting the optical waveguide 9 along the XY plane or along the Z direction, if necessary. That is, the stage 15 may be a so-called XY stage or XYZ stage.

The light source 11 is installed facing the light input/output surface 96 of the optical waveguide 9 . The light source 11 shown in FIG. 2 includes a light emitting section 111 , an emitting section 112 , and a light guide 113 that optically connects the light emitting section 111 and the emitting section 112 .

Examples of the light emitting unit 111 include light emitting diodes (LEDs), various lamps such as halogen lamps, and light emitting elements such as various laser light sources. Among these, various laser light sources are preferably used.

The light emitted from the light emitting unit 111 is not particularly limited, but is, for example, light with a maximum peak wavelength of the emission spectrum of 350 to 1400 nm. The maximum peak wavelength of the emission spectrum is preferably about 600-1100 nm, more preferably about 625-950 nm.

The emitting portion 112 is arranged so as to allow the light propagated through the light guide 113 to enter the light incident/emitting surface 96 .

The camera 12 is installed above the optical waveguide 9 shown in FIG. 2 and captures the light emitted from the mirror 97 . The distance between the camera 12 and the optical waveguide 9 is appropriately selected according to the specifications of the optical system in the camera 12, such as the magnification and required illuminance.

A camera 12 shown in FIG. and a housing 123 that houses the element 122 .

Although the magnification of the objective lens 121 is not particularly limited, it is preferably about 2 to 300 times, more preferably about 5 to 200 times. Also, the numerical aperture (NA) of the objective lens 121 is preferably about 0.01 to 0.4, more preferably about 0.02 to 0.35.

The imaging element 122 may be any element that can specify the light receiving position and luminance, and examples thereof include a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), an imaging plate, and the like.

Also, the camera 12 may include other optical elements in addition to the objective lens 121, the imaging device 122, and the housing 123 as described above. Other optical elements include, for example, bandpass filters, collimating lenses, polarizers, and the like.

The actuator 13 is a driving device that drives the camera 12 in the Z direction. Since the actuator 13 can precisely adjust its drive amount, the separation distance between the mirror 97 and the imaging device 122 can be strictly controlled.

The actuator 13 may be a linear actuator, a hydraulic cylinder, a power cylinder such as an electric cylinder, or the like.

The control unit 14 is electrically connected to the light source 11, the camera 12 and the actuator 13 and controls their operations. Specifically, the amount of light emitted from the light source 11 is adjusted, and the light reflected by the mirror 97 is captured by the camera 12 . Then, the obtained image is analyzed to obtain the luminance distribution of the emitted light on the image. Further, the distance between the mirror 97 and the imaging device 122 is changed by the actuator 13, and the imaging operation is performed in synchronization with the operation of changing the distance.

(Evaluation method of optical waveguide)
Next, a method for evaluating the optical waveguide according to the embodiment will be described.
FIG. 3 is a process diagram for explaining the evaluation method of the optical waveguide according to the embodiment.

In the evaluation method of the optical waveguide according to the present embodiment, as shown in FIG. A luminance distribution curve acquisition step S01 of obtaining a luminance distribution curve CL of emitted light in a predetermined direction in the plane of the imaging device 122, and an angle distribution curve CA of the mirror 97 is obtained based on the luminance distribution curve CL. It has an angular distribution curve obtaining step S02 to be obtained and an evaluating step S03 for evaluating the optical waveguide 9 based on the angular distribution curve CA. Each step will be described below in sequence.

[1] Brightness distribution curve acquisition step S01
First, light is emitted from the light source 11 and is made to enter the core portion 94 through the light incidence/emission surface 96 . The light incident on the core portion 94 is reflected by the mirror 97 , and the optical path is changed by 90° toward the upper direction of the optical waveguide 9 . Then, it enters the camera 12 and is imaged by the imaging device 122 . Thereby, the image sensor 122 can acquire the reflected light as an image. The acquired image is transmitted to the control unit 14 and image processing is performed in the control unit 14 . Specifically, since luminance information is attached to each pixel forming an image, the control unit 14 can obtain a two-dimensional luminance distribution.

FIG. 4 shows an example of the two-dimensional luminance distribution thus obtained. In the two-dimensional luminance distribution shown in FIG. 4, the luminance of the reflected light is expressed in a rectangular range, and the magnitude of the luminance acquired by each pixel is expressed by shading. Specifically, areas with high luminance are expressed in light colors, and areas with low luminance are expressed in dark colors.

Next, the controller 14 extracts a one-dimensional luminance distribution in a predetermined direction from such a two-dimensional luminance distribution. The predetermined direction is not particularly limited as long as it is the in-plane direction of the two-dimensional luminance distribution, that is, the in-plane direction of the imaging element 122. do. In FIG. 4, it is the horizontal direction. Then, a one-dimensional luminance distribution curve in the extending direction of the core portion 94 is obtained from the two-dimensional luminance distribution.

FIG. 5 is an example of a luminance distribution curve CL in the extending direction of the core portion 94 obtained from the two-dimensional luminance distribution shown in FIG. Specifically, the luminance distribution curve CL shown in FIG. 5 is parallel to the extending direction of the core portion 94 and drawn so as to pass through the center in the vertical direction of the two-dimensional luminance distribution shown in FIG. A luminance distribution curve CL on the direction axis. Note that the maximum luminance on the vertical axis is normalized to 1 in the luminance distribution curve CL shown in FIG. Therefore, the vertical axis in FIG. 5 is in arbitrary units. The horizontal axis is the distance when the bottom of the concave portion 970 formed in the optical waveguide 9 is set as the origin.

As shown in FIG. 5, the luminance distribution is not constant and often has luminance fluctuations. For this reason, the brightness distribution curve CL is not constant and changes according to the distance.

[2] Angular distribution curve acquisition step S02
Next, based on the luminance distribution curve CL, the angle distribution curve of the mirror 97 is obtained in a procedure described later.

The angle distribution curve is a curve representing the distribution of angles of the mirror 97 on the direction axis when the direction axis parallel to the extending direction of the core portion 94 is projected onto the mirror 97 . Such an angular distribution curve is usually obtained by scanning a contact probe or a laser for distance measurement on an inclined surface that constitutes the mirror 97, acquiring the displacement amount distribution of the inclined surface, that is, the profile of the mirror 97, and calculating the displacement amount. is obtained by calculating the angle change from Therefore, obtaining the angular distribution curve of the mirror 97 has hitherto involved the laborious task of directly measuring the displacement of such an inclined surface. Therefore, obtaining the angular distribution curve is not easy, and evaluation of the optical waveguide 9 based on it requires much labor and cost.

In order to solve this problem, the present inventors have extensively studied a method for easily performing evaluation based on the angular distribution of the mirror 97 . Then, they found that the angular distribution curve CA can be derived from the luminance distribution curve CL, and completed the present invention. Specifically, the inventor found that there is a certain correlation between transition of the change rate of the luminance distribution curve CL and transition of the change rate of the angular distribution curve CA. In other words, the inventors have found that the shape of the luminance distribution curve CL can be converted into the shape of the angle distribution curve CA.

FIG. 6 is a diagram showing a profile PR of the mirror 97 (inclined surface) determined by a confocal laser microscope and an angular distribution curve CA' derived from this profile PR. Also, FIG. 7 is a diagram for explaining a method of obtaining the profile PR of the mirror 97 shown in FIG.

The profile PR of the mirror 97 is the distribution of the surface displacement of the mirror 97, where the horizontal axis represents the distance from the origin set at the bottom of the recess 970 of the optical waveguide 9 and the vertical axis represents the amount of displacement of the mirror 97. It represents In acquiring this profile PR, as shown in FIG. 7, first, the optical waveguide 9 is fixed so that the mirror 97 is substantially horizontal. Next, a confocal laser microscope M is placed so as to face the mirror 97 . Then, the distance to the mirror 97 is measured using a confocal laser microscope M, and based on this, the distribution of the amount of displacement of the mirror 97, that is, the profile PR of the mirror 97 is obtained.

Note that the numerical values on the horizontal axis in FIG. 6 are obtained by dividing the measured horizontal distance by 1.414 so as to match the horizontal axis of the luminance distribution curve CL shown in FIG. The value of 1.414 is obtained from the ratio (√2/1) of the length of the mirror 97 to the thickness of the core layer 93 when the angle θ is 45°.

Since the angular distribution curve CA' of FIG. 6 derived from the profile PR in this way is a curve derived directly from the profile PR, its vertical axis is the angular displacement. In FIG. 6, the vertical axis of the angular distribution curve CA' is based on the angle θ formed by the mirror 97 and the lower surface of the cladding layer 91 shown in FIG. It is expressed as an angular displacement when Since such an angular distribution curve CA' is derived from the profile PR of the mirror 97 obtained using distance measuring means or the like, it can be said that the angular distribution of the mirror 97 is faithfully represented. Therefore, originally, this angular distribution curve CA' should be easily obtained, but as described above, obtaining it requires a lot of time and effort.

Therefore, in the present embodiment, the angular distribution curve CA is estimated from the luminance distribution curve CL as described above.

Since the vertical axis of the coordinate system representing the luminance distribution curve CL is a coordinate axis in arbitrary units as shown in FIG. It is necessary to convert the numerical value of the vertical axis of the curve CL into the numerical value of the vertical axis of the angular distribution curve CA. In other words, although the shape of the curve can be converted, the vertical axis must be converted.

An angular distribution curve CA' shown in FIG. 6 is a curve obtained separately from the profile PR of the mirror 97. As shown in FIG. Specifically, the profile PR of the mirror 97 is divided into minute sections, and the angle of each section is obtained. An angle distribution curve CA' is obtained by plotting the angle of each section. Therefore, the angular distribution curve CA' reflects the actual angular distribution of the mirror 97 almost faithfully. Therefore, in order to estimate the angular distribution curve CA from the luminance distribution curve CL, first, for the same optical waveguide 9, the luminance distribution curve CL is obtained in advance, and the profile PR of the mirror 97 is also obtained. An angular distribution curve CA' is derived therefrom. Then, when the luminance distribution curve CL is converted into the angle distribution curve CA, a conversion formula may be obtained so that the conversion result, that is, the angle distribution curve CA, approaches the separately obtained angle distribution curve CA'.

FIG. 8 is a diagram for explaining the procedure for converting the luminance distribution curve CL into the angular distribution curve CA.
Specifically, first, the luminance distribution curve CL is directly used as the angle distribution curve CA1. The vertical axis of the angular distribution curve CA1 is in arbitrary units.

Next, the angle distribution curve CA' obtained in advance is compared with the angle distribution curve CA1. Then, the angular distribution curve CA1 is multiplied by an arbitrary coefficient, the angular distribution curve CA1 is offset by an arbitrary amount, or both are performed so that the difference between the angular distribution curve CA' and the angular distribution curve CA1 becomes as small as possible. Perform "conversion" such as As an example, in the case of FIG. 8, in order to minimize the difference between the angle distribution curve CA1 and the angle distribution curve CA', the angle distribution curve CA1 is multiplied by a coefficient "1.0" and the angle distribution curve CA1 is shifted downward. A transformation such as an offset of "0.45" to . By applying this conversion formula, the angular distribution curve CA1 is converted into the "angular distribution curve CA". It can be seen from FIG. 8 that the angular distribution curve CA after conversion is in good approximation with the angular distribution curve CA'. The offset direction may be the vertical axis direction or the horizontal axis direction.

By using the conversion formula obtained in advance as described above, the angular distribution curve CA can be quickly and easily estimated from the luminance distribution curve CL.

[3] Evaluation step S03
Next, the optical waveguide 9 is evaluated based on the angular distribution curve CA.
FIG. 9 is a diagram for explaining the evaluation process.

This evaluation step is a step of evaluating the optical waveguide 9 based on the angular distribution curve CA, and the content of the evaluation is not particularly limited as long as it is based on the angular distribution curve CA. Here, as an example, an evaluation process composed of three processes, which will be described later, will be described.

The evaluation process according to the present embodiment includes a specific angle range length measurement process S31 for obtaining the length a of a portion A in which the angular displacement is continuously within the threshold range Th in the angle distribution curve CA, and a predetermined It has an inclined plane length measuring step S32 for obtaining the length b of the directional component, and a length comparing step S33 for evaluating the optical waveguide 9 based on the length a and the length b. Each step will be described below in sequence.

[3-1] Specific angle range length measurement step S31
First, in the angular distribution curve CA, the length a of the portion A where the angular displacement is continuously within the threshold range Th is obtained. As described above, the angular distribution curve CA represents the angular displacement when the angle θ of 45° is set to 0°. Therefore, if the angular distribution curve CA is greater than 0°, it means that the angle θ of the mirror 97 at that position is greater than 45°, while if the angular distribution curve CA is less than 0°, that It means that the angle θ of the mirror 97 at the position is less than 45°. Therefore, in the angular distribution curve CA, the closer the angular displacement is to 0°, the closer the angle θ of the mirror 97 is to 45°. It turns out that.

In the example of FIG. 9, the range of angular displacements from -4° to 4° is set as the threshold range Th, and is shaded. Then, the angular distribution curve CA is continuously within the threshold range Th when the distance on the horizontal axis is between approximately 17 μm and approximately 60 μm. In the portion A included in this range of the angular distribution curve CA, since the angular displacement is continuous and relatively small, it can be said that the mirror 97 is of high quality in terms of angular distribution.

In other words, this proves that there is an area in the plane of the mirror 97 that has a high angle accuracy and that is relatively large. This makes it possible to evaluate that the optical waveguide 9 having this mirror 97 can realize high-quality optical communication.

Specifically, when there is an area with high angle accuracy and a certain size in the plane of the mirror 97, the radiation angle of the reflected light in that area is approximately as designed. Therefore, when arranging, for example, an optical element so as to be coupled with the mirror 97, by arranging the optical element 3 and the lens 54 so as to irradiate the area with light, high optical coupling efficiency can be easily realized. can.

In addition, since such regions are grouped together to some extent, there are few regions with low angle accuracy in the irradiation region of the light emitted from the optical element. , the light is emitted from the optical element 3 via the mirror 97 and the light waveguide 1 via the light input/output surface 96, and the integrated value of the brightness incident on the optical component such as the optical fiber can be increased. Therefore, high optical coupling efficiency and high S/N ratio can be realized also from the viewpoint of the total luminance value.

It should be noted that the extent to which the regions are grouped together can be determined based on the size of the portion A of the angular distribution curve CA. For example, in the portion A of the angular distribution curve CA, if there is a portion having a shape that is particularly close to 0° and has a particularly small angular displacement, the area on the mirror 97 corresponding to that portion is the reflected light is highly likely to be reflected in a certain direction with high accuracy.

Therefore, the optical waveguide 9 may be evaluated based on the shape of the portion A in this way. As a result, more useful evaluation can be performed in order to further improve the optical coupling efficiency between the optical waveguide 9 and other optical components.

On the other hand, outside the portion A, that is, the portion where the distance on the horizontal axis is smaller than 17 μm and the portion where the distance is larger than 60 μm, the angular displacement represented by the angular distribution curve CA is less than −4°. there is Therefore, since the angular displacement is relatively large at this portion, it can be determined that the accuracy of the angle of the mirror 97 is low.

As described above, the optical waveguide 9 can be evaluated, in particular, the superiority or inferiority of the optical coupling efficiency via the mirror 97 can be evaluated. Then, the length a of the portion A within the threshold range Th is obtained. The length a of this portion A refers to the length along the horizontal axis. In the example of FIG. 6, about 43 [μm] (=60−17) corresponds to the length a of the portion A.

[3-2] Inclined surface length measurement step S32
Subsequently, the length b of the component in the predetermined direction of the mirror 97 is obtained. The length b of the predetermined direction component of the mirror 97 is the length of the projected plane in the predetermined direction when the mirror 97 tilted with respect to the core layer 93 is projected onto the plane on which the core layer 93 spreads. 94 is the length in the extending direction. This length b may be a known value obtained in advance, or may be a value obtained as follows.

FIG. 10 is a diagram for explaining a method of obtaining the length b of the component in the predetermined direction of the mirror 97 (inclined surface). In the method shown in FIG. 10, the positions of light source 11 and camera 12 are opposite to the method shown in FIG. The light source 11 shown in FIG. 10 is installed above the optical waveguide 9 so as to face the mirror 97 . That is, it is installed at the position of the camera 12 shown in FIG. The camera 12 shown in FIG. 10 is installed facing the light input/output surface 96 of the optical waveguide 9 . That is, it is installed at the position of the light source 11 shown in FIG.

10, when light is emitted from the light source 11, the light enters the mirror 97 from the upper surface of the optical waveguide 9. As shown in FIG. When the light is reflected by the mirror 97 , it propagates through the core portion 94 and exits from the light incident/exiting surface 96 . This light enters the camera 12 and is imaged by the imaging device 122 . In the image thus captured, the length in the thickness direction of the optical waveguide 9 is "length b".

[3-3] Length comparison step S33
The length a and the length b obtained as described above are compared.

Length b is substantially equal to the thickness of core portion 94 . Therefore, the length b can be said to be the maximum value of the predetermined direction component of the mirror 97 . Then, it can be considered that the closer the length a is to the length b, the higher the accuracy of the angle as described above, and the larger the area of the mirror 97 occupies a relatively large area. In other words, the area where the angular distribution is good and continuous occupies a larger area on the mirror 97 . Therefore, the optical waveguide 9 can be quantitatively evaluated using the ratio of the length a to the length b as an evaluation index.

As an example, when the mirror angle is 45 degrees, the ratio of length a to length b is preferably 90% or more, more preferably 95% or more. An optical waveguide 9 that satisfies such a ratio has a good angular distribution in the mirror 97 and a high occupancy rate of continuous regions. Therefore, it becomes possible to accurately evaluate the optical waveguide 9 that can realize good optical coupling efficiency in the mirror 97, and such an evaluation method becomes useful.

In the example of FIG. 9, since the length a is almost equal to the length b, the ratio of the length a to the length b is almost 100%.

Here, FIG. 11 is another example of the luminance distribution curve CL different from that in FIG. FIG. 11 also shows an angular distribution curve CA obtained by converting this luminance distribution curve CL.

In the example shown in FIG. 11, the length a of portion A is shorter than in the example shown in FIG. Therefore, the ratio of length a to length b is less than 90%. Therefore, the example shown in FIG. 11 can be evaluated as having higher angle accuracy and less areas that are included in the mirror 97, compared to the examples shown in FIGS. can. Therefore, the example shown in FIG. 11 has an evaluation index that is 10% or more lower than the examples shown in FIGS. It is possible to quantitatively evaluate the optical waveguide 9 such that there is

As described above, the evaluation process according to the present embodiment includes the specific angle range length measurement process S31 for obtaining the length a of the portion A in which the angular displacement is continuously within the threshold range Th in the angle distribution curve CA. , and a length comparison step S33 for evaluating the optical waveguide 9 based on the length a and the length b.

By having each of these steps, the evaluation step can quantitatively evaluate the optical coupling efficiency between the optical waveguide and other optical components. Therefore, more useful evaluation can be performed.

(Method for manufacturing optical module)
Next, a method for manufacturing an optical module according to the embodiment will be described.

12A to 12C are process diagrams for explaining the method for manufacturing the optical module according to the embodiment. 13 and 14 are diagrams for explaining the method of manufacturing the optical module according to the embodiment. 13 and 14 are referred to as "top", and the bottom as "bottom" in the following description. Also, in FIGS. 13 and 14, the same components as in the above-described embodiment are denoted by the same reference numerals as described above, and detailed description thereof will be omitted.

The method for manufacturing an optical module according to the embodiment is a method for manufacturing an optical module 100 having an optical waveguide 9, an optical element 3, and a lens array 5, as shown in FIG.
First, before describing the manufacturing method, the optical module 100 shown in FIG. 14 will be described.

The optical module 100 shown in FIG. 14 has an optical waveguide 9, an electric substrate 2, an optical element 3 optically connected to the optical waveguide 9, a control element 4, and a lens array 5. . In such an optical module 100, an optical fiber (not shown) is connected to the optical waveguide 9 via a receptacle. Light emitted from the optical fiber is introduced into the optical waveguide 9 and reflected by the mirror 97, thereby A certain optical element 3 receives the light. If the optical element 3 is a light-emitting element, the light emitted from the optical element 3 is reflected by the mirror 97 and made incident on the optical fiber via the optical waveguide 9 . Thereby, optical communication can be performed between the optical fiber and the optical module 100 .

The electric board 2 shown in FIG. 14 includes an insulating substrate 21 , and a conductive layer 22 and contacts 23 provided on the upper surface of the insulating substrate 21 .

Further, an optical element 3 and a control element 4 are mounted on the upper surface of the electric board 2 shown in FIG. These elements and the conductive layer 22 are electrically connected via bonding wires (not shown). Note that this connection structure is not limited to bonding wires, and may be replaced by other structures such as flip-chip bonding.

When the optical element 3 is a light emitting element, examples of the optical element 3 include a surface emitting laser (VCSEL), a light emitting diode (LED), an organic EL element, and the like.

Moreover, when the optical element 3 is a light receiving element, the optical element 3 may be, for example, a photodiode (PD, APD), a phototransistor, or the like.

Also, the control element 4 may be, for example, a driver IC, a transimpedance amplifier (TIA), a limiting amplifier (LA), or a combination IC combining these elements.

In addition to the elements described above, the electric board 2 is equipped with a CPU (central processing unit), MPU (microprocessor unit), LSI, IC, RAM, ROM, capacitors, coils, resistors, diodes, and the like. good too.

An MT type optical connector 62 is attached to the right end of the optical waveguide 9 shown in FIG. This MT type optical connector 62 is inserted from one end side into a receptacle (not shown).

A lens array 5 is provided between the optical waveguide 9 and the electrical substrate 2 . The lens array 5 shown in FIG. 14 includes a base portion 51 and a wall portion 52 erected downward from the edge of the base portion 51 . The bottom surface of the wall portion 52 is bonded to the top surface of the electric substrate 2 , and the optical waveguide 9 is bonded to the top surface of the base portion 51 . A lens 54 is formed on the base portion 51 . This lens 54 is, for example, a convex lens and can focus the light passing through the base 51 .

In addition to the lens 54, the lens array 5 may be provided with a diffraction grating, a polarizer, a prism, a filter, and the like.

Next, a method for manufacturing the optical module 100 shown in FIG. 14 will be described. As shown in FIG. 12, this manufacturing method includes a luminance distribution curve acquisition step S01, an angle distribution curve acquisition step S02, and a portion A where the angular displacement is continuously within the threshold range Th in the angle distribution curve CA. A specific angle range position acquisition step S04 for obtaining the position, and a positioning step S05 for positioning the optical element 3 with respect to the mirror 97 (inclined surface) of the optical waveguide 9 based on the position of the portion A. Each step will be described below in order.

[1] Brightness distribution curve acquisition step S01
First, a luminance distribution curve CL is obtained in the same manner as in the evaluation method of the optical waveguide.

[2] Angular distribution curve acquisition step S02
Next, an angular distribution curve CA of the mirror 97 is obtained based on the luminance distribution curve CL.

[3] Specific angle range position acquisition step S04
Next, as described above, in the angular distribution curve CA, the position of the portion A where the angular displacement is continuously within the threshold range Th is determined. As described above, this portion A can be said to correspond to an area in which the angle is highly accurate and which is relatively large in the plane of the mirror 97 . Therefore, the light reflected by the area of the mirror 97 corresponding to this portion A is the light most likely to contribute to optical communication among the light reflected by the entire mirror 97 . Therefore, the optical module is manufactured by aligning the optical waveguide 9 and the optical element 3 so that the area of the mirror 97 corresponding to this portion A is irradiated with the radiation light emitted from the optical element 3. It is possible to maximize the optical coupling efficiency of

When extracting the brightness distribution curve CL from the image shown in FIG. 4 as shown in FIG. 5, by changing the extraction direction, it is possible to obtain a plurality of brightness distribution curves CL with different directions. In this case, it is possible to more accurately specify the region of the mirror 97 corresponding to the portion A based on the plurality of angular distribution curves CA obtained by converting the plurality of luminance distribution curves CL. can be done accurately.

Also, the position of the portion A on the image sensor 122 changes as the distance between the image sensor 122 and the mirror 97 changes. Therefore, in order to accurately align the optical element 3 with respect to the mirror 97, information on the angular distribution on the mirror 97 is required. In other words, by performing an evaluation based on the angular distribution curve CA, even if the distance between the mirror 97 and the optical element 3 changes, the traveling direction of the light reflected from the area corresponding to the portion A of the mirror 97 can be predicted. can. As a result, it becomes possible to more accurately specify the position where the optical element 3 should be arranged, that is, the position of the optical element 3 capable of achieving high optical coupling efficiency.

[4] Positioning step S05
Next, the optical element 3 is positioned with respect to the mirror 97 based on the position of the portion A specified.

Thereby, the optical coupling efficiency between the mirror 97 and the optical element 3 can be maximized. As a result, an optical module with small coupling loss between components can be efficiently manufactured.

Specifically, based on the angular distribution curve CA, the position of the optical element 3 with a high probability that the radiated light emitted from the optical element 3 is surely incident on the region corresponding to the portion A of the mirror 97 is obtained. Therefore, the lens 54 should be placed on the optical path. Therefore, it is possible to more accurately grasp the position where the lens array 5 should be arranged. First, as shown in FIG. 13, the lens array 5 is aligned with the optical waveguide 9 and adhered. As a result, the lensed optical waveguide 10 shown in FIG. 14, in which the coupling loss between the mirror 97 and the lens 54 is sufficiently small, is obtained.

Subsequently, as shown in FIG. 14, the optical waveguide 10 with lens is mounted on the electric substrate 2 on which the optical element 3 is mounted. At this time, from the viewpoint of making the radiation emitted from the optical element 3 incident on the area corresponding to the portion A of the mirror 97, the position where the optical element 3 should be arranged is obtained, and the optical element 3 is arranged at that position. The position of the optical waveguide 10 with a lens is adjusted as shown in FIG. Then, when the adjustment is completed, the optical waveguide 10 with lens and the electric substrate 2 are bonded. As described above, the optical module 100 with small coupling loss between components can be manufactured.

Although the method for evaluating an optical waveguide and the method for manufacturing an optical module according to the present invention have been described above based on the illustrated embodiments, the present invention is not limited to these.

For example, if necessary, the concave portion for forming the mirror may be filled with a material having a lower refractive index than the core portion, or a metal film or the like may be formed on the mirror.

Further, in the method for evaluating an optical waveguide and the method for manufacturing an optical module, steps for any purpose may be added to the above-described embodiments.

1 evaluation device 2 electric substrate 3 optical element 4 control element 5 lens array 9 optical waveguide 10 optical waveguide with lens 11 light source 12 camera 13 actuator 14 control unit 15 stage 21 insulating substrate 22 conductive layer 23 contact 51 base 52 wall 54 lens 62 MT type optical connector 91 clad layer 92 clad layer 93 core layer 94 core portion 95 side clad portion 96 light input/output surface 97 mirror 100 optical module 111 light emitting portion 112 light emitting portion 113 light guide 121 objective lens 122 imaging element 123 housing 151 adhesive Layer 970 recess CA angle distribution curve CA' angle distribution curve CA1 angle distribution curve CL brightness distribution curve M confocal laser microscope PR profile S01 brightness distribution curve acquisition step S02 angle distribution curve acquisition step S03 evaluation step S04 specific angle range position acquisition step S05 Positioning step S31 Specific angle range length measurement step S32 Inclined surface length measurement step S33 Length comparison step Th Threshold range θ Angle

Claims (6)

A method for evaluating an optical waveguide comprising a linearly extending core portion and an inclined surface for converting an optical path of the core portion, comprising:
a step of making light incident on the core portion, receiving emitted light reflected by the inclined surface and emitted by a detection surface, and obtaining a luminance distribution curve of the emitted light in a predetermined direction within the plane of the detection surface;
a step of obtaining an angle distribution curve of the inclined surface by subjecting the luminance distribution curve to conversion using a conversion formula obtained in advance ;
evaluating the optical waveguide based on the angular distribution curve;
A method for evaluating an optical waveguide, comprising: The step of evaluating the optical waveguide includes:
In the angular distribution curve, obtain the length of the portion where the angular displacement is continuously within the threshold range,
2. The method for evaluating an optical waveguide according to claim 1, wherein the optical waveguide is evaluated based on the length of the portion and the length of the component of the inclined surface in the predetermined direction. 3. The optical waveguide evaluation method according to claim 2, wherein the optical waveguide is evaluated based on the shape of the portion of the angular distribution curve. The thickness of the core portion obtained from an image obtained by capturing the light emitted from the core portion by allowing light to enter from the inclined surface is obtained as the length of the component in the predetermined direction of the inclined surface. 4. The method for evaluating an optical waveguide according to 2 or 3. The conversion formula is
After obtaining the profile of the inclined surface in advance, dividing the profile into minute sections and obtaining an angle for each section,
By plotting the angle of the section, an angle distribution curve for calculating the conversion formula is obtained,
At least one of a coefficient and an offset amount that minimizes the difference between the angular distribution curve for calculating the conversion formula and the luminance distribution curve of the emitted light obtained in advance for the same optical waveguide as the optical waveguide is obtained. 5. The method for evaluating an optical waveguide according to claim 1, which is a derived formula. A method for manufacturing an optical module including an optical waveguide and an optical element, the optical waveguide having a linearly extending core portion and an inclined surface for converting the optical path of the core portion, the method comprising:
Light is incident on the core portion of the optical waveguide, emitted light reflected by the inclined surface is received by a detection surface, and a luminance distribution curve of the emitted light in a predetermined direction within the detection surface is obtained. process and
a step of obtaining an angle distribution curve of the inclined surface by subjecting the luminance distribution curve to conversion using a conversion formula obtained in advance ;
determining the position of a portion of the angular distribution curve where the angular displacement is continuously within the threshold range;
positioning the optical element with respect to the inclined surface of the optical waveguide based on the position of the portion;
A method of manufacturing an optical module, comprising:

Images