JP2009192955A - Optically functional element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optically functional element which is easily manufactured and improves its manufacturing yield. <P>SOLUTION: The optically functional element includes: a light emitting element 12 as a light source; a dielectric substrate 14 with an optical waveguide 20 formed; and a light receiving element 16 for converting light to electricity. Light from the light emitting element 12 is modulated by an external electric signal, with the modulated light output as an electric signal by the light receiving element 16. The optical waveguide 20 is composed of an input waveguide part 20a formed on the surface 14a of the dielectric substrate 14, branching waveguide parts 20b, 20c divided from the input waveguide part 20a to receive modulation by the external electric signal, and an output waveguide part 20d connected to the modulation part. The optically waveguide 20 is designed such that a plurality of groups of optical waveguides 20A, 20B are formed in the dielectric substrate 14 and that the differences of the designed length of the two branching waveguide parts 20b, 20c in each group are different from each other. The light emitting element 12 and the light receiving element 16 are selected in the optical waveguides of the plurality of groups and arranged in a manner coupling to the optical waveguide that can generate a desired bias phase difference. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a light-emitting element as a light source, a dielectric substrate on which an optical waveguide is formed, and a light-receiving element that converts light into electricity, and modulates the light from the light source with an external electric signal and modulates the light The present invention relates to an optical functional element that outputs the emitted light as an electrical signal by a light receiving element and a method for manufacturing the same.

  Conventionally, as an optical functional element having this type of modulation function, those described in Patent Documents 1 and 2 are known, and the configuration described in these Patent Documents is generally as shown in FIG. Yes.

  In the figure, 112 is a light emitting element as a light source, 114 is a dielectric substrate, 116 is a light receiving element, an optical waveguide 120 is formed on the dielectric substrate 114, and the optical waveguide 120 is, for example, a Mach-Zehnder type An optical interferometer is configured, and the light emitting element 112 and the light receiving element 116 are disposed so as to face both sides of the optical waveguide 120.

  The light output from the light emitting element 112 is collected by the condenser lens 122 and is incident on one end of the optical waveguide 120 from the end face of the dielectric substrate 114. In the optical waveguide 120, it is branched into two branch waveguide parts, subjected to reverse modulation in one branch waveguide part or in both branch waveguide parts by an external electric signal, and then multiplexed again. The light is emitted from the other end of the optical waveguide 120, collected by the condenser lens 124, and received by the light receiving element 116.

  In order to give the desired bias phase difference and increase the sensitivity of the modulation, the two branch waveguide sections are designed to have a predetermined length difference.

JP-A-6-27427 JP 2003-131182 A

  However, since the difference in length is a very slight difference of about several tens of nanometers, the processing accuracy required to obtain the desired bias phase difference is very high, the manufacturing is difficult, and the yield is poor. There is a problem.

  The present invention has been made in view of such a problem, and an object thereof is to provide an optical functional element capable of facilitating manufacture and improving yield and a method for manufacturing the same.

In order to solve the above problems, the present invention includes a light emitting element as a light source, a dielectric substrate on which an optical waveguide is formed, and a light receiving element that converts light into electricity, The light emitting element, comprising: an input waveguide portion formed on a dielectric substrate; two branch waveguide portions separated from the input waveguide portion; and an output waveguide portion where the branch waveguide portions merge In the optical functional element that modulates the light from at least one of the branched waveguide portions by the external electric signal and outputs the modulated light as an electric signal by the light receiving element,
The optical waveguide is designed such that a plurality of sets are formed on the dielectric substrate, and the difference in design length between the two branch waveguide portions of each set is different for each set.
The light emitting element and the light receiving element are disposed so as to be coupled to a selected optical waveguide among the plurality of sets of optical waveguides.

  According to a second aspect of the present invention, in the first aspect of the present invention, the difference in design length between a pair of two branching waveguide portions is a length corresponding to 1 / 4λ with respect to the wavelength λ of the light used. On the other hand, the difference between the design lengths of two branching waveguide portions in another set is zero.

According to a third aspect of the present invention, the plurality of sets of optical waveguides according to the first or second aspect are respectively formed on a surface of the dielectric substrate, and the light emitting element is formed on the surface from the back side of the dielectric substrate. The light is emitted toward the start end of the input waveguide portion along a direction orthogonal to the
The start end of the input waveguide portion is provided with a turning means for directing light from a direction orthogonal to the surface to the input waveguide portion.

According to a fourth aspect of the present invention, a light emitting element as a light source, a dielectric substrate on which an optical waveguide is formed, and a light receiving element that converts light into electricity, the light from the light emitting element is converted into an external electric signal. In the method of manufacturing an optical functional element that modulates the modulated light and outputs the modulated light as an electrical signal by the light receiving element,
Multiple sets of optical waveguides comprising an input waveguide portion, two branch waveguide portions separated from the input waveguide portion, and an output waveguide portion joined by the branch waveguide portion on the same dielectric substrate Forming a difference in the design length of the two branch waveguide portions of each set, so that the start ends of the input waveguide portions of each set are close to each other,
Light from the light emitting elements is emitted toward the start ends of the input waveguide portions of all sets to propagate the light to all the optical waveguides, and the frequency f0 is sequentially modulated to the branch waveguide portions of each set. Light that has applied a signal and has reached the end of the output waveguide portion is received by a light receiving element, a frequency f0 component and a frequency 2f0 component are detected from the electrical signal converted by the light receiving element, and the frequency f0 component is a frequency 2f0. Select the pair that has the most dominance over the ingredients,
The final positioning of the light emitting element is performed with respect to the selected optical waveguide, the light from the light emitting element is coupled to the selected optical waveguide so that the light is propagated only to the selected optical waveguide, and external electrical A signal is applied to a selected optical waveguide.

According to a fifth aspect of the present invention, in the method of the fourth aspect, the plurality of sets of optical waveguides are respectively formed on the surface of the dielectric substrate, and the light emitting element is formed on the surface from the back side of the dielectric substrate. The light is emitted toward the start end of the input waveguide portion along a direction orthogonal to the
The start end of the input waveguide portion is provided with a turning means for directing light from a direction orthogonal to the surface to the input waveguide portion.

  It is very difficult to produce the difference in length between the two branch waveguide portions as designed so that a desired bias phase difference is generated in the two branch waveguide portions at least one of which is modulated by an external electric signal. However, by simultaneously manufacturing a plurality of sets of optical waveguides having different design length differences between the two branch waveguide portions on the same dielectric substrate, even if there is a manufacturing error, The difference in the branching waveguide portion can be set so that the bias phase difference becomes a desired phase difference or a phase difference close to the desired phase difference. Therefore, by selecting and using the optical waveguide having the desired phase difference, the yield can be increased. Can be improved.

  According to the third and fifth aspects of the present invention, since the position of the light spot from the light emitting element can be visually grasped as the position in the surface of the dielectric substrate, the position of the light spot is determined as the input guide. By aligning with the start end of the waveguide portion, the final positioning of the light emitting element can be easily performed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is an overall perspective view of the optical functional element of the present invention, FIG. 2 is a cutaway perspective view thereof, FIG. 3 is a plan view thereof, and FIG. 4 is a longitudinal sectional view thereof.

  In the figure, an optical functional element 10 includes a light emitting element 12 as a light source, a dielectric substrate 14 on which an optical waveguide is formed, and a light receiving element 16 that converts light into electricity.

  As the light emitting element 12, a light emitting diode or a laser can be used. Among them, a super luminescent diode, a surface emitting laser, or the like can be used. As the light receiving element 16, a photodiode can be used.

  The dielectric substrate 14 is made of a dielectric crystal having an electro-optic effect, such as lithium niobate, and has an x cut width of about 5 μm by titanium diffusion or annealed proton exchange along the y-axis direction on the surface 14a. The single mode optical waveguide 20 is formed.

  The optical waveguide 20 is composed of two sets of optical waveguides 20A and 20B formed substantially parallel to each other on a surface 14a that is a plane parallel to the plate surface of the dielectric substrate 14. Each of the optical waveguides 20A and 20B includes one input waveguide portion 20a, two branch waveguide portions 20b and 20c that are divided by a Y branch from the input waveguide portion 20a to form a modulation portion, and two branch waveguides. The portions 20b and 20c are composed of one output waveguide portion 20d joined by the Y branch.

  The optical waveguide 20A and the optical waveguide 20B have substantially the same configuration, but the length of the branching waveguide portions 20b and 20c of the optical waveguide 20A is set to the wavelength λ of the light to be used in the optical waveguide. The branching waveguide portions 20b and 20c of the optical waveguide 20B are designed to have the same length, that is, the difference is 0, while they are designed to be different from each other by ¼λ.

  The two branch waveguide portions 20b and 20c constitute a modulation portion, and a pair of electrodes 22 and 24 are formed with the branch waveguide portions 20b and 20c interposed therebetween.

  The input waveguide portions 20a of the respective optical waveguides 20A and 20B are partially bent, and are arranged so that their start ends are close to each other. Similarly, the output waveguide portion 20b of each of the optical waveguides 20A and 20B is partially bent, and the terminal ends thereof are arranged so as to approach each other.

  In the surface 14a of the dielectric substrate 14, a V-shaped cut having a slope having an inclination angle of 45 degrees with respect to the surface 14a so as to be orthogonal to the input waveguide portion 20a of each of the optical waveguides 20A and 20B. 14c is formed, and a V-shaped cut 14d having a slope having an inclination angle of 45 degrees with respect to the surface 14a is formed so as to be orthogonal to the output waveguide portion 20d. The cuts 14c and 14d can be collectively formed over the plurality of dielectric substrates 14 by a dicing operation on the wafer before being cut out as the dielectric substrate 14.

  As shown in FIG. 5, a reflective film is attached to the inclined surface having the inclination angle of 45 degrees on the side in contact with the input waveguide portion 20a of the V-shaped cut 14c (becoming the starting end of the input waveguide portion 20a). , The mirror 26 constituting the turning means is formed. The mirror 26 may be formed for each input waveguide portion 20a of each of the optical waveguides 20A and 20B, or may be formed across the input waveguide portions 20a of all the optical waveguides 20A and 20B.

  Similarly, a reflective film is attached to the inclined surface having an inclination angle of 45 degrees on the side in contact with the output waveguide portion 20d of the V-shaped cut 14d (which is the terminal end of the output waveguide portion 20d), so that the second turning direction is obtained. A mirror 28 constituting the means is formed. The mirror 28 may be formed for each output waveguide portion 20d of each of the optical waveguides 20A and 20B, or may be formed over the output waveguide portion 20d of all the optical waveguides 20A and 20B.

  Each reflective film can be formed by gold vapor deposition, and after the reflective film is formed, the V-shaped notch is filled with a material having a refractive index equal to or similar to that of the dielectric substrate 14. Good. However, this filling material is not shown in the drawing. The mirrors 26 and 28 as the deflecting means may be constituted by micromirrors inserted into 45-degree inclined grooves as shown in FIG. Alternatively, when there is a large reflectance at the inclined surfaces themselves of the end portions of the optical waveguide portions 20a and 20d, a means such as a separate reflecting film can be omitted by using it as a turning means.

An antireflection film (AR coating) is preferably attached to the entire surface of the back surface 14b of the dielectric substrate 14. The antireflection film can be composed of a SiO ₂ or TiO ₂ film, and this film can be formed in a lump on the wafer before being cut out as the dielectric substrate 14.

  A mounting plate 30 for supporting the light emitting element 12 and the light receiving element 16 is provided on the back side of the dielectric substrate 14. The mounting plate 30 can be made of ceramic or metal with good heat dissipation. As shown in FIG. 4, the mounting plate 30 is formed with vertical holes 30a and 30b whose longitudinal directions coincide with the notches 14c and 14d.

  A highly rigid cylindrical holder 32 made of metal, for example, that holds the light emitting element 12 and is fixed to the dielectric substrate 14 is attached to the vertical hole 30a. The cylindrical holder 32 has an inner cross-sectional shape that matches the shape of the vertical hole 30a. A flange 32 a is formed at the upper end of the cylindrical holder 32, and the flange 32 a is attached to the lower surface of the dielectric substrate 14 and fixed to the dielectric substrate 14.

  As shown in FIGS. 7 and 8, an annular groove 32b is formed on a part of the surface of the flange 32a. The annular groove 32b is filled with an ultraviolet curable resin, and the ultraviolet curable resin is bonded thereto. The cylindrical holder 32 and the dielectric substrate 14 are bonded as materials. By contracting when the ultraviolet curable resin is cured by being irradiated with ultraviolet rays, portions other than the annular groove 32b of the flange 32a come into contact with the dielectric substrate 14 and hold the dielectric substrate 14 on the flange surface. be able to. Further, in order to prevent the resin from leaching inside the cylindrical holder 32 before the ultraviolet curable resin is cured, an O-ring and a high surface tension are formed at the boundary portion of the inner peripheral surface of the flange 32a of the cylindrical holder 32. A watertight protective member 33 (FIG. 8) such as a material may be provided. Thus, since the cylindrical holder 32 and the dielectric substrate 14 are bonded to each other in the circumferential direction by the annular groove 32b, the dielectric substrate 14 can be reliably fixed in the two axial directions in the plane. Instead of the annular groove 32b, a plurality of radial grooves 32c formed at equal intervals in the circumferential direction as shown in FIG. 9 may be used. Further, instead of filling the grooves 32b and 32c with the ultraviolet curable resin, the flange surface can be solder-welded to the dielectric substrate 14. The flange 32a does not need to be fixed to the dielectric substrate 14 over the entire circumference, and a part of the flange 32a may protrude from the dielectric substrate 14 as shown in FIG. 7B. .

  As shown in FIG. 10, the light emitting element 12 is welded to the cylindrical holder 32 by laser welding or the like at equal intervals in the circumferential direction (usually three points at intervals of 120 degrees). The light is emitted toward the start end of the input waveguide portion 20a of the selected optical waveguide of the plurality of sets of optical waveguides 20A and 20B along a direction orthogonal to the optical waveguide 20A. The light emitting element 12 can be either a CAN type or a chip type. However, by using the CAN type as shown in the illustrated example, the light emitting element itself can be hermetic. An airtight structure is not required.

  A condenser lens 34 is provided between the light emitting element 12 and the start end of the input waveguide portion 20a. The light from the light emitting element 12 can be coupled to the optical waveguide 20 with high efficiency by the condenser lens 34. The condenser lens 34 may be attached to the inner peripheral surface of the cylindrical holder 32 separately from the light emitting element 12, but may be integrated with the CAN type light emitting element 12, or the rear surface 14 b of the dielectric substrate 14. It may be integrally fixed to.

  Returning to FIG. 4, a highly rigid metal cylindrical holder 38 that holds the light receiving element 16 and supports the dielectric substrate 14 is attached to the vertical hole 30 b of the attachment plate 30. A flange 38 a is formed at the upper end of the cylindrical holder 38, and the flange 38 a supports the back surface 14 b of the dielectric substrate 14. However, the flange 38a of the cylindrical holder 38 is only in contact with the back surface 14b and is not fixed to the back surface 14b. As a result, the dielectric substrate 14 is restrained only by the cylindrical holder 32 at one end thereof, and the generation of stress on the dielectric substrate 14 due to temperature change / vibration is prevented. However, a thin elastic sheet or coating 39 may be interposed between the flange 38a and the back surface 14b.

  The light receiving elements 16 are welded to the cylindrical holder 38 at equal intervals in the circumferential direction by laser welding or the like (usually three points at intervals of 120 degrees), and along the direction orthogonal to the front surface 14a and the back surface 14b of the dielectric substrate 14. The light propagated by reflecting off the mirror 28 from the end of the output waveguide portion 20d of the selected optical waveguide of the plurality of sets of optical waveguides 20A and 20B is received. A condensing lens 40 is provided between the end of the output waveguide portion 20 d and the light receiving element 16. Like the light emitting element 12, the light receiving element 16 can be either a CAN type or a chip type. However, by using the CAN type as shown in this example, the light emitting element itself can be hermetically sealed. Therefore, a separate airtight structure is not required.

  The condenser lens 40 may be attached to the inner peripheral surface of the cylindrical holder 38 separately from the light receiving element 16, but may be integrated with the CAN type light receiving element 16. The light from the optical waveguide 20 can be coupled to the light receiving element 16 with high efficiency by the condenser lens 40.

  Instead of directly or indirectly contacting the cylindrical holder 38 with the dielectric substrate 14, as shown in FIG. 14, the cylindrical holder 38 is separated and the elastic member 41 is interposed between the mounting plate 30 and the dielectric substrate 14. It may be inserted. The elastic member can be composed of RTV rubber, Teflon (registered trademark), or the like.

  Hereinafter, how to select an optical waveguide to be used from the two sets of optical waveguides 20A and 20B will be described.

  In the modulation portion, the lengths of the two branch waveguide portions 20b and 20c are preferably set to a difference in length of about ¼λ, thereby giving a desired bias phase difference of 90 degrees to increase the sensitivity of the modulation. Ideally higher. Therefore, if it is ideally manufactured, the optical waveguide 20A is selected. However, processing with an accuracy of about several tens of nanometers is very difficult, and may not be manufactured as designed due to various factors during the manufacturing process. In this embodiment, since the optical waveguides 20A and 20B having a difference of ¼λ and 0 in the branching waveguide portion which is the modulation portion are formed on the same dielectric substrate 14 at the same time, the actual value deviates from the design value. However, since the influence is considered to reach all the optical waveguides in the same manner, it can be expected that the bias phase difference between any of the optical waveguides 20A and 20B is equal to or close to the desired phase difference. Therefore, an optical waveguide whose actual bias phase difference is a desired phase difference is selected.

  For this purpose, first, before the light emitting element 12 is fixed, the light emitting element 12 is slightly separated from the dielectric substrate 14 so as to be out of focus, and diffused light is transmitted to the start ends of the two input waveguide portions 20a and 20a. In order to allow light to enter both the optical waveguides 20A and 20B, although they are weak. Then, a modulation signal (frequency f0) is sequentially applied to the modulation portions of the respective optical waveguides 20A and 20B (FIGS. 20A and 20B). The modulated light is received by the light receiving element 16, the f0 component and the 2f0 component are detected, and the bias phase is determined from the ratio of the f0 component and the 2f0 component. If the bias phase is 90 degrees, the f0 component is dominant (FIG. 20C), and if the bias phase is 0 degrees, the 2f0 component is dominant (FIG. 20D). In the example of FIG. 20, the optical waveguide 20A is selected.

  When the optical waveguide 20 is selected, fine alignment adjustment of the light emitting element 12 is performed. At this time, the light emitting element 12 is adjusted using the clearance between the light emitting element 12 and the inner peripheral surface of the cylindrical holder 32.

  When the light is incident from the end face of the dielectric substrate 14 as in the conventional structure, there is a problem in that it is difficult to make adjustments by visual means to confirm whether the light is coupled to the optical waveguide. In the present embodiment, since the light emitting element 12 is disposed on the back surface side of the dielectric substrate 14, the light from the light emitting element 12 can be visually confirmed from the front surface side of the dielectric substrate 14. The adjustment can be easily performed.

  In addition, since the area of the image formed by the condensing lens 34 on the light emitting surface of the light emitting element 12 is small (10 μm or less), it is normal to reliably propagate light to the start end of the input waveguide portion 20a of the optical waveguides 20A and 20B. Although difficult, it can be performed by visually confirming the light from the light emitting element 12 from the surface side of the dielectric substrate 14, and the adjustment thereof is also easy.

  In order to further facilitate the adjustment work, as shown in FIG. 11, marks 14 m may be formed on the surface of the dielectric substrate 14 so as to correspond to the respective optical waveguides 20 </ b> A and 20 </ b> B. The mark 14m can be formed at the same time in the substrate manufacturing process, and may be patterned with Cr or the like. The position of the mark 14m is determined in the vicinity of the mirror 26 by a predetermined distance and in a predetermined direction.

  In the adjustment operation, the position of the light spot where the light from the light emitting element 12 hits the dielectric substrate 14 is imaged by a CCD camera installed above the surface of the dielectric substrate 14, and the light emitting element in the cylindrical holder 32. 12 position is adjusted. Since the light spot that hits the mirror 26 cannot be imaged from the surface side, first, the position in the plane parallel to the surface 14a of the light emitting element 12 and / or the parallel plane so that the light spot coincides with the mark 14m. The vertical position of the light emitting element 12 is roughly adjusted so that the inclination of the light emitting element 12 with respect to is adjusted and the focus is set at the mark 14m. Then, as shown in FIG. 12, when the light spot coincides with the mark 14m and is in focus, the position of the light emitting element 12 is moved from the mark 14m in a predetermined direction by a predetermined distance. Adjust so that it is in position. Then, in the positioned state, the light emitting element 12 is fixed to the cylindrical holder 32 by the laser welding.

  The position of the mark 14m can be an arbitrary position in the vicinity of the mirror 26, but may be provided so as to cross the optical waveguide 20 as shown in FIG. As a result, the light spot is moved along the mark 14m to the optical waveguide 20 and then moved by a predetermined distance in the direction along the optical waveguide 20, thereby adjusting the light spot to be at the position of the mirror 26. be able to.

  Since the light receiving surface of the light receiving element 16 is larger than the light emitting surface of the light emitting element 12 (100 μm or more), the precision of the adjustment of the light emitting element 12 is not required. Therefore, the light receiving element 16 may be positioned similarly to the light emitting element 12 so as to match the end of the output waveguide portion 20d of the selected optical waveguide 20A, 20B, but simply, the two optical waveguides 20A, 20B It is sufficient to fix the light receiving element 16 to the cylindrical holder 38 so that it is aligned near the midpoint of the output waveguide portion 20d.

  The dielectric substrate 14 is provided with stray light preventing cuts 14g and 14h having V-shaped cross sections parallel to the cuts 14c and 14d on the outer side of the cuts 14c and 14d on the front surface 14a. As shown in FIG. 15, stray light preventing cuts 14i and 14j having a V-shaped or U-shaped cross section extending in a direction orthogonal to the cuts 14c and 14d are formed.

  In the optical functional element 10 configured as described above, the light emitted from the light emitting element 12 in the direction orthogonal to the front surface 14a and the back surface 14b of the dielectric substrate 14 is condensed on the mirror 26 by the condenser lens 34. After being turned 90 degrees by the mirror 26 and propagating through the input waveguide portion 20a of the selected optical waveguide 20, it is branched into the branched waveguide portions 20b and 20c.

  When an external electric signal is input to the electrodes 22 and 24, push-pull phase modulation opposite to each other is performed on the light propagating through the branched waveguide portions 20b and 20c due to a change in refractive index due to the electro-optic effect. The modulated light is combined and output to the output waveguide portion 20d. A signal corresponding to the modulation signal is output by the multiplexing.

  The light propagating through the output waveguide portion 20d is redirected by the mirror 28 in a direction orthogonal to the dielectric substrate 14, collected by the condenser lens 40, received by the light receiving element 16, and converted into an electrical signal. The

  As described above, in this embodiment, an optical functional element can be easily manufactured by selecting an optical waveguide capable of generating a desired bias phase difference among optical waveguides formed in a plurality of sets. Yield can be improved. In the above example, two sets of optical waveguides are formed. However, it is possible to form three or more sets of optical waveguides having different lengths in the branched waveguide portions, and the length of the design difference is also long. Any length is possible. However, as a minimum, if two sets of optical waveguides having a difference of λ / 4 between the branched waveguide portions are formed as in this example, one of them is close to the desired bias phase difference. I can expect that.

In addition, the following effects can be achieved in this embodiment.
The light emitted from the light emitting element 12 is turned 90 degrees and propagates through the optical waveguide 20, and the light that has passed through the modulation portion of the optical waveguide 20 is turned 90 degrees and received by the light receiving element 16. Since the direction and the light receiving direction differ by 180 degrees, stray light can be prevented as much as possible. Stray light can be further prevented by the stray light preventing cuts 14i, 14j, 14g, and 14h.
By preventing light diffusion by the condensing lenses 34 and 40, stray light can be further prevented, and the coupling efficiency between the light emitting element and the optical waveguide and between the optical waveguide and the light emitting element can be increased.

In this embodiment, since the position adjustment between the light emitting element 12 and the dielectric substrate 14 can be visually monitored from the surface side, the adjustment operation can be performed automatically at high speed and easily as necessary. It can be performed. Adjustment can be performed more easily by using the mark 14m that matches the light spot of the light emitting element 12. As described above, instead of adjusting the position of the light emitting element 12, the position of the dielectric substrate 14 may be adjusted.
In addition, in this embodiment, by using a CAN type as the light emitting element 12 and the light receiving element 16, the element can be airtight.
In this embodiment, since light is incident from the back surface of the dielectric substrate 14 and light does not need to be incident from the end surface of the dielectric substrate 14, a rough surface is obtained by cutting out the wafer by dicing. It is not necessary to polish the end face of the dielectric substrate 14.

  Next, FIG. 16 is a diagram illustrating a second embodiment of the present invention. In this example, the light receiving element 16 is arranged on the surface 14 a side of the dielectric substrate 14, and the light receiving element 16 is fixed to the surface 14 a side of the dielectric substrate 14 by solder bumps 42. According to this configuration, a bare chip type light receiving element 16 can be used. A cut 14d 'is formed in the surface 14a of the dielectric substrate 14. The cut 14d' has one surface orthogonal to the surface 14a and the other surface having an angle of 45 degrees with respect to the surface 14a. It has become. A reflecting film is preferably attached to the inclined surface having an inclination angle of 45 degrees to form the mirror 28 constituting the second turning means.

  Alternatively, as shown in FIG. 17, instead of forming the notch 14d ′, the end surface of the dielectric substrate 14 may be inclined at an angle of 45 degrees, and further, an inclined surface serving as a terminal end of the output waveguide portion 20d. A reflective film to be the mirror 28 may be attached to the substrate.

  Also in this example, the same operation and effect as the first embodiment can be obtained. In this case, a bare chip type can be suitably used as the light receiving element 16, and the vertical hole 30b and the cylindrical holder 38 can be omitted. Since the light receiving surface of the light receiving element 16 is larger than the light emitting surface of the light emitting element 12 and adjustment is not difficult, the adjustment in this example can be easily performed.

  FIG. 18 is a diagram illustrating a third embodiment of the present invention. In this example, the light emitting element 12 and the light receiving element 16 are arranged on the surface 14 a side of the dielectric substrate 14, and the light emitting element 12 and the light receiving element 16 are fixed to the front side of the dielectric substrate 14 by solder bumps 42. According to this configuration, a bare chip type can be used as the light receiving elements 12 and 16.

  A cut 14c ′ is formed in the surface 14a of the dielectric substrate 14, and the cut 14c ′ has one surface orthogonal to the surface 14a and the other surface having an angle of 45 degrees with respect to the surface 14a. It has become. A reflecting film is preferably attached to the inclined surface having an inclination angle of 45 degrees to form the mirror 26 constituting the turning means. Further, a cut 14d 'is formed, and the cut 14d' has one surface orthogonal to the surface 14a and the other surface having an angle of 45 degrees with respect to the surface 14a. A reflecting film is preferably attached to the inclined surface having an inclination angle of 45 degrees to form the mirror 28 constituting the second turning means.

  In the case of this example, since the light emitting element 12 and the light receiving element 16 and the optical waveguide 20 are in close contact with each other, the lenses 34 and 40 can be omitted.

  Alternatively, as shown in FIG. 19, the light emitting elements 12 and 16 can be attached to the dielectric substrate 14 via the attachment parts 50 and 50.

  Also in this example, the same effect as the first embodiment can be obtained. In this example, the light emitting element 12 cannot be adjusted by capturing the light spot from the surface 14a side, but the light emitting element 12 and the light receiving element 16 are chip type, so that the attachment is easy, and the light emitting element 12 and the light receiving element This can be easily performed by bonding the element 16 to the surface 14 a side of the dielectric substrate 14. Furthermore, since the light emitting element 12 and the light receiving element 16 can be combined with the dielectric substrate 14 to be a flat substrate as a whole, handling is facilitated.

FIG. 21 is a perspective view showing a fourth embodiment of the present invention.
The dielectric substrate 14 has a thermoelectromotive force acting in the z-axis direction (pyroelectric effect). Therefore, in order to avoid this, it is necessary to short-circuit both side surfaces of the dielectric substrate 14. As a countermeasure for this, as shown in FIG. 21, metal patterns (for example, gold patterns) 14n and 14n are further formed on both sides of the optical waveguide 20 on the surface 14a of the dielectric substrate 14, and these metal patterns 14n and 14n are optically transmitted. It is good to connect with the thin pattern which does not affect the waveguide 20, or to connect with a wire. Furthermore, as shown in FIG. 22, a conductive paint 14o may be applied to both sides of the dielectric substrate 14 so as to be in contact with the metal pattern 14n. Accordingly, even when the dielectric substrate 14 is supported in a cantilever manner as shown in FIG. 4 or FIG. 14, it is possible to short-circuit both side surfaces of the dielectric substrate 14.

1 is an overall perspective view of an optical functional element of the present invention. FIG. 2 is a cutaway perspective view of FIG. 1. FIG. 2 is a plan view of FIG. 1 (the vertical / horizontal scale ratio is changed from that of FIG. 1 for the sake of explanation). It is a longitudinal cross-sectional view of FIG. (A) is an enlarged perspective view near the start end of the input waveguide portion or near the end of the output waveguide portion, and (b) is an enlarged cross-sectional view of the start end of the input waveguide portion. It is an expanded sectional view showing other examples near the starting end of an input waveguide portion. It is a top view which shows the relationship between a cylindrical holder and a dielectric substrate (it shows with a virtual line). It is a fragmentary sectional view which shows the adhering state of a cylindrical holder and a dielectric substrate. It is a fragmentary perspective view showing the other example of a cylindrical holder. It is a bottom view which shows the adhering state of a light emitting element and a cylindrical holder. It is an explanatory perspective view showing adjustment of a light emitting element. It is an enlarged plan view of a mark and a light spot. It is an enlarged plan view showing the relationship between another mark, an optical waveguide, and a light spot. It is a longitudinal cross-sectional view showing a modification. It is a perspective view of the back surface side of a dielectric substrate. It is a longitudinal section showing a 2nd embodiment of the present invention. It is a longitudinal cross-sectional view showing the modification of 2nd Embodiment of this invention. It is a longitudinal section showing a 3rd embodiment of the present invention. It is a longitudinal cross-sectional view showing the modification of 3rd Embodiment of this invention. It is a wave form diagram showing the relation between the modulation signal by two optical waveguides, and an output signal. It is a perspective view of the dielectric substrate showing 4th Embodiment of this invention. It is a perspective view of the dielectric substrate showing 4th Embodiment of this invention. It is a top view showing the conventional optical functional element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical functional element 12 Light emitting element 14 Dielectric board | substrate 14a Front surface 14b Back surface 16 Light receiving element 20, 20A, 20B Optical waveguide 20a Input waveguide part 20b Branched waveguide part 20c Branched waveguide part 20d Output waveguide part 26 Mirror (direction change) means)
28 Mirror

Claims (5)

An input waveguide comprising: a light emitting element as a light source; a dielectric substrate on which an optical waveguide is formed; and a light receiving element that converts light into electricity, wherein the optical waveguide is formed on the dielectric substrate, respectively. And a branching waveguide part separated from the input waveguide part, and an output waveguide part joined by the branching waveguide part. The light from the light emitting element is branched and guided by the external electric signal. In an optical functional element that modulates at least one of the waveguide portions and outputs the modulated light as an electrical signal by the light receiving element,
The optical waveguide is designed such that a plurality of sets are formed on the dielectric substrate, and the difference in design length between the two branch waveguide portions of each set is different for each set.
The optical functional element, wherein the light emitting element and the light receiving element are disposed so as to be coupled to a selected one of the plurality of optical waveguides.   The difference in design length between the two branch waveguide portions in one set is a length corresponding to ¼λ with respect to the wavelength λ of the light used, whereas the two branch waveguides in another set. 2. The optical functional element according to claim 1, wherein the difference in design length of the portions is zero. The plurality of sets of optical waveguides are respectively formed on the surface of the dielectric substrate, and the light emitting element is a starting end of the input waveguide portion along a direction orthogonal to the surface from the back surface side of the dielectric substrate. Which emits light toward
The optical functional element according to claim 1, wherein the start end of the input waveguide portion is provided with a diverting unit that directs light from a direction orthogonal to the surface toward the input waveguide portion. . A light-emitting element as a light source; a dielectric substrate on which an optical waveguide is formed; and a light-receiving element that converts light into electricity. The light from the light-emitting element is modulated by an external electric signal and modulated. In the method of manufacturing an optical functional element that outputs light as an electrical signal by the light receiving element,
Multiple sets of optical waveguides comprising an input waveguide portion, two branch waveguide portions separated from the input waveguide portion, and an output waveguide portion joined by the branch waveguide portion on the same dielectric substrate Forming a difference in the design length of the two branch waveguide portions of each set, so that the start ends of the input waveguide portions of each set are close to each other,
Light from the light emitting elements is emitted toward the start ends of the input waveguide portions of all sets to propagate the light to all the optical waveguides, and the frequency f0 is sequentially modulated to the branch waveguide portions of each set. Light that has applied a signal and has reached the end of the output waveguide portion is received by a light receiving element, a frequency f0 component and a frequency 2f0 component are detected from the electrical signal converted by the light receiving element, and the frequency f0 component is a frequency 2f0. Select the pair that has the most dominance over the ingredients,
The final positioning of the light emitting element is performed with respect to the selected optical waveguide, the light from the light emitting element is coupled to the selected optical waveguide so that the light is propagated only to the selected optical waveguide, and external electrical A method of manufacturing an optical functional element, wherein a signal is applied to a selected optical waveguide. The plurality of sets of optical waveguides are respectively formed on the surface of the dielectric substrate, and the light emitting element is provided at the start of the input waveguide portion along a direction orthogonal to the surface from the back surface side of the dielectric substrate. To emit light toward
5. The method of manufacturing an optical functional element according to claim 4, wherein a turning means for directing light from a direction perpendicular to the surface to the input waveguide portion is provided at the start end of the input waveguide portion. .

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