Optical waveguide device, and method for manufacturing an optical waveguide device

Abstract

To provide an optical waveguide device with excellent strength even without a support substrate, and a method for manufacturing the same. [Solution] The optical waveguide device 110 according to the present invention comprises a substrate 10 made of an electro-optic material, the substrate 10 integrally formed with a thin portion 12 that extends in one direction, thick portions 13 that are thicker than the thin portion 12 and provided on both sides of the thin portion 12, and a ridge-type optical waveguide 11 formed along the direction in which the thin portion 12 extends.

Description

Technical Field

[0001] The present invention relates to an optical waveguide device and a method for manufacturing an optical waveguide device.

Background Art

[0002] A ridge-type optical waveguide formed by providing a pair of ridge grooves in an optical material is known. For example, Patent Document 1 discloses an optical waveguide substrate in which an optical material layer having a core for propagating light is provided on a support substrate via a cladding.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an optical waveguide device as exemplified in Patent Document 1, the optical waveguide is provided on an optical material thin film. Therefore, when handling such as processing and transportation, a support substrate for supplementing the strength of the optical material thin film, a cladding for connecting the support substrate and the optical material thin film, etc. are required. For this reason, there is a problem that the number of parts required for device manufacturing increases and the cost increases.

[0005] In view of the above problems, an object of the present disclosure is to provide an optical waveguide device excellent in strength even without a support substrate and a method for manufacturing the same.

Means for Solving the Problems

[0006] An optical waveguide device according to one aspect of the present disclosure comprises a substrate made of an electro-optic material, the substrate integrally comprising a thin portion formed to extend in one direction, thick portions provided on both sides of the thin portion and thicker than the thin portion, and a ridge-type optical waveguide formed along the direction in which the thin portion extends.

[0007] A method for manufacturing an optical waveguide device according to one aspect of the present disclosure comprises the steps of: preparing a substrate made of an electro-optic material; forming a thin-walled portion and a thick-walled portion by providing the substrate with grooves extending in one direction; masking a part of the surface of the thin-walled portion along the direction in which the grooves extend; etching the masked thin-walled portion to form an optical waveguide; and removing the mask from the etched substrate. [Effects of the Invention]

[0008] The present invention provides an optical waveguide device with excellent strength even without a support substrate, and a method for manufacturing the same. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view of an optical waveguide device according to the first embodiment. [Figure 2] This is a cross-sectional view of the optical waveguide device along the cutting line II-II in Figure 1. [Figure 3] This is a cross-sectional view in the zx plane of an optical waveguide device according to a second embodiment. [Figure 4] This is a cross-sectional view in the zx plane of an optical waveguide device according to the third embodiment. [Figure 5] This is a plan view of an optical waveguide device according to the fourth embodiment. [Figure 6] Figure 5 is a cross-sectional view of the optical waveguide device along the cutting line VI-VI. [Figure 7] This is a plan view of an optical waveguide device according to the fifth embodiment. [Figure 8]Figure 7 shows a cross-sectional view of the optical waveguide device along the cutting line VIII-VIII. [Figure 9] This is a cross-sectional view in the zx plane of an optical waveguide device according to the sixth embodiment. [Figure 10] This is a cross-sectional view in the zx plane of an optical waveguide device according to the seventh embodiment. [Figure 11] This is a flowchart illustrating the manufacturing method of the optical waveguide device described herein. [Figure 12] This is a cross-sectional view in the zx plane at each step of the manufacturing process of the optical waveguide device according to the fourth embodiment. [Figure 13] This is a cross-sectional view in the zx plane at each step of the manufacturing process of the optical waveguide device according to the sixth embodiment. [Modes for carrying out the invention]

[0010] (Optical waveguide devices) Specific embodiments to which the present invention is applied will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. The multiple configuration examples described below can be implemented independently or in combination as appropriate. These multiple configuration examples have novel features that are different from each other. Therefore, these multiple configuration examples contribute to solving different purposes or problems and contribute to producing different effects. For clarity of explanation, the following description and drawings have been simplified as appropriate. In each drawing, the same or corresponding elements are denoted by the same reference numeral, and redundant explanations are omitted as necessary for clarity of explanation. Also, the right-handed xyz coordinate system shown in Figure 1 and the other figures is for explaining the positional relationships of the components. In each figure, the direction of propagation of light L in the optical waveguide is the positive y-axis direction, and the vertically upward direction is the positive z-axis direction.

[0011] [First Embodiment] FIG. 1 is a plan view of an optical waveguide device 110 according to a first embodiment. FIG. 2 is a cross-sectional view of the optical waveguide device 110 taken along the cutting line II-II in FIG. 1. As shown in FIGS. 1 and 2, the optical waveguide device 110 is composed of a substrate 10.

[0012] The substrate 10 is made of an electro-optic material. The electro-optic material constituting the substrate 10 is not particularly limited and can be selected, for example, from lithium niobate, lithium tantalate, etc. Note that the substrate 10 being made of an electro-optic material means that the substrate 10 contains an electro-optic material and may contain other inevitable components as long as the effects of the present invention are not impaired.

[0013] The substrate 10 is integrally formed with a thin portion 12 formed to extend in one direction, thick portions 13 provided on both sides of the thin portion 12 and thicker than the thin portion 12, and a ridge-type optical waveguide 11 formed along the direction in which the thin portion 12 extends. In the present embodiment, the thin portion 12 is formed by providing a groove extending in the y-axis direction at the lower part of the substrate 10, and the upper surface of the thin portion 12 and the upper surface of the thick portion 13 are flush. The optical waveguide 11 is provided so as to protrude from the upper surface side of the thin portion 12.

[0014] The optical waveguide device 110 having the above configuration has the optical waveguide 11 supported by the rigid thick portion 13. Therefore, the optical waveguide device 110 is excellent in strength even without a support substrate.

[0015] The thickness (length in the z-axis direction) and width (length in the x-axis direction) of the optical waveguide 11 and the thin portion 12 are not particularly limited and can be appropriately designed according to the type of guided light. For example, when guiding light with a wavelength of 1550 nm, the thickness a of the optical waveguide 11 can be 1 μm or less, the thickness b of the thin portion 12 can be 500 nm or less, and the width c of the optical waveguide 11 can be 1 μm or less.

[0016] The width d of the thin-walled portion 12 is not particularly limited and should be greater than or equal to the width c of the optical waveguide 11. The width d is preferably 10 μm or more from the viewpoint of facilitating the manufacturing process of the optical waveguide device 110, and preferably 100 μm or less from the viewpoint of maintaining the strength of the optical waveguide device 110.

[0017] The thickness e of the thickened portion 13 is not particularly limited, but from the viewpoint of maintaining the strength of the optical waveguide device 110, it is preferably 100 μm or more, and more preferably 500 μm or more.

[0018] In the example shown in Figure 2, the cross-section of the groove below the thin-walled portion 12 is approximately rectangular, but the shape of the cross-section is not particularly limited. For example, the groove may have an inverted mesa structure where the thin-walled portion 12 side (upper part) is narrow and the opposite side (lower part) is wide, or a forward mesa structure where the thin-walled portion 12 side (upper part) is wide and the opposite side (lower part) is narrow. From the viewpoint of ease of manufacturing and processing, it is preferable that the groove has an inverted mesa structure where the thin-walled portion 12 side is narrow and the opposite side is wide.

[0019] In this embodiment, the optical waveguide 11 is surrounded by air, which has a low refractive index. Therefore, the refractive index difference between the inside and outside of the optical waveguide 11 is large in all directions, resulting in a large light confinement effect. On the other hand, in an optical waveguide device equipped with a support substrate, the optical waveguide has a bonding surface with the support substrate or cladding. At this bonding surface, the refractive index difference between the inside and outside of the optical waveguide is relatively small, resulting in a small light confinement effect. Based on the above, it can be said that the optical waveguide device 110 is superior to conventional optical waveguide devices equipped with a support substrate in terms of light confinement effect.

[0020] [Second Embodiment] Next, an optical waveguide device 120 according to the second embodiment will be described with reference to Figure 3. In the description of the second embodiment, elements that are the same as or corresponding to elements in the first embodiment will be assigned a new reference number in the 20s with the same last digit, and their descriptions will be omitted as appropriate.

[0021] Figure 3 is a cross-sectional view of the optical waveguide device 120 in the zx plane. Compared to the optical waveguide device 110, the optical waveguide device 120 differs in the arrangement of the thin-walled portion 22. The thin-walled portion 22 is formed by providing a groove extending in the y-axis direction on the upper part of the substrate 20, and the lower surface of the thin-walled portion 22 and the lower surface of the thick-walled portion 23 are flush.

[0022] The optical waveguide device 120 having the above configuration also has excellent strength even without a support substrate, because the optical waveguide 21 is supported by the rigid, thickened portion 23. Furthermore, since the optical waveguide 21 does not protrude from the main outer surface of the substrate 20, i.e., the upper surface of the thickened portion 23, the optical waveguide 21 is protected from external impacts.

[0023] [Third Embodiment] Next, an optical waveguide device 130 according to the third embodiment will be described with reference to Figure 4. In the description of the third embodiment, elements that are the same as or corresponding to elements in the first embodiment will be assigned a new reference number in the 30s with the same last digit, and their descriptions will be omitted as appropriate.

[0024] Figure 4 is a cross-sectional view of the optical waveguide device 130 in the zx plane. Compared to the optical waveguide device 110, the optical waveguide device 130 differs in the arrangement of the optical waveguide 31 and the thin-walled portion 32. The thin-walled portion 32 is formed by providing grooves extending in the y-axis direction on the top and bottom of the substrate 30 and is located between the top and bottom surfaces of the thick-walled portion 33. The optical waveguide 31 is provided to protrude from both the top and bottom sides of the thin-walled portion 32.

[0025] The optical waveguide device 130 having the above configuration also has excellent strength even without a support substrate, because the optical waveguide 31 is supported by the rigid, thick-walled portion 33. Furthermore, since the optical waveguide 31 does not protrude from the main outer surface of the substrate 30, i.e., the upper surface of the thick-walled portion 33, the optical waveguide 31 is protected from external impacts.

[0026] In the example shown in Figure 4, the optical waveguide 31 is provided to protrude from both the upper and lower sides of the thin-walled portion 32. However, the optical waveguide 31 only needs to protrude from at least one of the upper or lower sides of the thin-walled portion 32. In either structure, the optical waveguide 31 has a ridge shape and functions as an optical waveguide.

[0027] [Fourth Embodiment] Next, the optical waveguide device 140 according to the fourth embodiment will be described with reference to Figures 5 and 6. In the description of the fourth embodiment, elements that are the same as or corresponding to the elements in the first embodiment will be assigned a new reference numeral in the 40s range with the same last digit, and their descriptions will be omitted as appropriate.

[0028] Figure 5 is a plan view of the optical waveguide device 140 according to the fourth embodiment. Figure 6 is a cross-sectional view of the optical waveguide device 140 along the cutting line VI-VI in Figure 5. Compared to the optical waveguide device 110, the optical waveguide device 140 differs in that, in addition to the substrate 40, it includes a low refractive index film 48 and electrodes 49a and 49b. Furthermore, the optical axis (not shown) of the optical waveguide 41 is horizontal to the upper surface of the thin-walled portion 42 and perpendicular to the direction in which the thin-walled portion 42 extends. That is, the optical axis of the optical waveguide 41 is in the x-axis direction in Figure 6.

[0029] The low refractive index film 48 is made of a material with a lower refractive index than the optical waveguide 41 and is provided on the upper surface of the thin portion 42 so as to cover the optical waveguide 41. The thickness of the low refractive index film 48 is not particularly limited, but for example, the thickness of the thickest part can be 5 μm or less.

[0030] Electrodes 49a and 49b are electrodes that extend in the same direction as the optical waveguide 41. Electrodes 49a and 49b are provided on both sides of the optical waveguide 41 in the optical axis direction (x-axis direction) of the optical waveguide 41. By connecting electrodes 49a and 49b to a power supply (not shown), a high-frequency voltage can be applied in the optical axis direction (x-axis direction) of the optical waveguide 41, thereby modulating the phase of light L. Therefore, the optical waveguide device 140 functions as an optical modulator.

[0031] Furthermore, the difference between the refractive index of the optical waveguide 41 for light with a wavelength of 1550 nm and the refractive index of the low refractive index film 48 for light with a frequency of 10 GHz is preferably 0.8 or less, and more preferably 0.5 or less. For example, when the optical waveguide 41 is composed of lithium niobate, the refractive index of the optical waveguide 41 for light with a wavelength of 1550 nm is about 2.1, so suitable materials for the low refractive index film 48 include SiO2 and Al2O3. When the refractive indices of the optical waveguide 41 and the low refractive index film 48 satisfy the above relationship, the speed of 1550 nm light passing through the optical waveguide 41 and the speed of electromagnetic waves of about 10 GHz passing through the low refractive index film 48 become close. Therefore, when a high-frequency voltage of 10 GHz or more is applied in the optical axis direction of the optical waveguide 41, the speed of electrical signals and the speed of light are easily matched, and optical modulation can be performed efficiently.

[0032] In the example shown in Figure 6, electrodes 49a and 49b are provided on the surface of the low refractive index film 48, but electrodes 49a and 49b may also be arranged inside the low refractive index film 48. In this case, it is preferable that electrodes 49a and 49b are arranged opposite each other across the optical waveguide 41. In such a configuration, voltage can be applied to the optical waveguide 41 more efficiently.

[0033] Furthermore, in the example shown in Figure 6, the low refractive index film 48 is provided so as to cover the entire upper surface of the thin-walled portion 42, but it is sufficient for the low refractive index film 48 to cover the optical waveguide 41. Therefore, the low refractive index film 48 may be provided so as to cover only a part of the thin-walled portion 42, or it may cover at least a part of the thick-walled portion 43.

[0034] [Fifth Embodiment] Next, the optical waveguide device 150 according to the fifth embodiment will be described with reference to Figures 7 and 8. In the description of the fifth embodiment, elements that are the same as or corresponding to the elements in the fourth embodiment will be assigned a new reference numeral in the 50s range, with the same last digit, and their descriptions will be omitted as appropriate.

[0035] Figure 7 is a plan view of the optical waveguide device 150 according to the fifth embodiment. Figure 7 is a cross-sectional view of the optical waveguide device 150 along the cutting line VIII-VIII in Figure 8. Compared to the optical waveguide device 140, the optical waveguide device 150 differs in the arrangement of the low refractive index film 58 and electrodes 59a and 59b, and in the direction of the optical axis (not shown) of the optical waveguide 51.

[0036] The low refractive index film 58 is provided on both the upper and lower surfaces of the thin-walled portion 52. Furthermore, the optical axis of the optical waveguide 51 is perpendicular to the upper surface of the thin-walled portion 52. That is, the optical axis of the optical waveguide 51 is in the z-axis direction. Electrodes 59a and 59b are provided on both sides of the optical waveguide 51 in the optical axis direction (z-axis direction).

[0037] In this embodiment as well, by connecting electrodes 59a and 59b to a power supply (not shown), a high-frequency voltage can be applied in the optical axis direction (z-axis direction) of the optical waveguide 51, thereby modulating the phase of light L. Therefore, the optical waveguide device 150 functions as an optical modulator.

[0038] It is preferable that electrodes 59a and 59b are positioned opposite each other across the optical waveguide 51. In this configuration, voltage can be applied to the optical waveguide 51 more efficiently. In this case, electrodes 59a and 59b may be positioned on the surface of the low refractive index film 58, or at least one of them may be positioned inside the low refractive index film 58.

[0039] [Sixth Embodiment] Next, an optical waveguide device 160 according to the sixth embodiment will be described with reference to Figure 9. In the description of the sixth embodiment, elements that are the same as or corresponding to elements in the fourth embodiment will be assigned a new reference number in the 60s range with the same last digit, and their descriptions will be omitted as appropriate.

[0040] Figure 9 is a cross-sectional view of the optical waveguide device 160 in the zx plane. Compared to the optical waveguide device 140, the optical waveguide device 160 differs in the arrangement of the thin-walled portion 62. The thin-walled portion 62 is formed by providing a groove extending in the y-axis direction on the upper part of the substrate 60, and the lower surface of the thin-walled portion 62 and the lower surface of the thick-walled portion 63 are flush.

[0041] The optical waveguide device 160 having the above configuration can also have a high-frequency voltage applied in the optical axis direction (x-axis direction) of the optical waveguide 61 by connecting electrodes 69a and 69b to a power supply (not shown), thereby modulating the phase of the light L. Therefore, the optical waveguide device 160 functions as an optical modulator.

[0042] [Seventh Embodiment] Next, an optical waveguide device 170 according to the seventh embodiment will be described with reference to Figure 10. In the description of the seventh embodiment, elements that are the same as or corresponding to elements in the fifth embodiment will be assigned a new reference numeral in the 70s with the same last digit, and their descriptions will be omitted as appropriate.

[0043] Figure 10 is a cross-sectional view of the optical waveguide device 170 in the zx plane. Compared to the optical waveguide device 150, the optical waveguide device 170 differs in the arrangement of the optical waveguide 71 and the thin-walled portion 72. The thin-walled portion 72 is formed by providing grooves extending in the y-axis direction on the top and bottom of the substrate 70 and is located between the top and bottom surfaces of the thick-walled portion 73. The optical waveguide 71 is provided to protrude from both the top and bottom sides of the thin-walled portion 72.

[0044] The optical waveguide device 170, having the above configuration, can also have a high-frequency voltage applied in the optical axis direction (x-axis direction) of the optical waveguide 71 by connecting electrodes 79a and 79b to a power supply (not shown), thereby modulating the phase of the light L. Therefore, the optical waveguide device 170 functions as an optical modulator.

[0045] (Manufacturing method for optical waveguide devices) Next, a method for manufacturing the optical waveguide device according to this disclosure will be described. Below, as an example of the present invention, a method for manufacturing the optical waveguide device 140 and the optical waveguide device 160 will be described.

[0046] [First manufacturing method] First, as a first manufacturing method, the manufacturing method for the optical waveguide device 140 will be described with reference to Figures 11 and 12. Figure 11 is a flowchart illustrating the manufacturing method for the optical waveguide device according to this disclosure. Figure 12 is a cross-sectional view in the zx plane at each step of the manufacturing process of the optical waveguide device 140. As shown in Figure 11, the manufacturing method for the optical waveguide device 140 comprises steps S1 to S7.

[0047] First, in step S1, a substrate S made of an electro-optic material is prepared (Figure 12(a)). The electro-optic material constituting the substrate S is not particularly limited and can be selected from, for example, lithium niobate or lithium tantalate. In the manufacture of the optical waveguide device 140, a substrate S is prepared such that the optical axis is the x-axis direction in Figure 12(a). Note that when we say that the substrate S is made of an electro-optic material, we mean that the substrate S contains an electro-optic material and may also contain other unavoidable components to the extent that they do not impair the effects of the present invention.

[0048] Next, in step S2, a groove extending in one direction is provided in the substrate S to form a thin-walled portion and a thick-walled portion. If the etching rate differs between the upper and lower surfaces of the substrate S, it is preferable to form them using the following procedure. First, a groove extending in the y-direction is made on the side of the substrate S with the higher etching rate (Figure 12(b)). The method of making the groove is not particularly limited and can be appropriately selected from machining or etching. By making the groove on the side with the higher etching rate and easier processing, thin-walled and thick-walled sections can be formed in a short time. Next, the side of the substrate S with the lower etching rate is machined to adjust the thin-walled portion to the desired thickness (Figure 12(c)). By machining the side with the lower etching rate and which is more difficult to process, the thickness of the thin-walled portion can be precisely controlled.

[0049] Next, in step S3, a portion of the surface of the formed thin-walled portion is masked along the direction in which the groove extends. In the manufacturing of the optical waveguide device 140, a mask M is formed along the y-axis direction on the side of the thin-walled portion where the groove is not formed (Figure 12(d)). The material of the mask M is not particularly limited and can be appropriately selected from materials resistant to etching solutions.

[0050] Next, in step S4, the masked thin portion is etched to form the optical waveguide 41. At this time, the masked area forms the optical waveguide 41, and the unmasked areas form the thin portion 42 and the thick portion 43 (Figure 12(e)).

[0051] Next, in step S5, the mask M is removed from the etched substrate S (substrate 40). This yields a substrate 40 having an optical waveguide 41, a thin section 42, and a thick section 43 (Figure 12(f)).

[0052] Next, in step S6, a low refractive index film 48 is deposited on the substrate 40 so as to cover the optical waveguide 41. In the manufacturing of the optical waveguide device 140, the low refractive index film 48 is deposited so as to cover the upper surface of the thin-walled portion 42 (Figure 12(g)). The low refractive index film 48 is composed of a material with a lower refractive index than the substrate 40, such as SiO2 or Al2O3, in the form of a film. The method for depositing the low refractive index film 48 can be appropriately selected from known methods such as thermal oxidation, chemical vapor deposition (CVD), and physical vapor deposition (PVD).

[0053] Finally, in step S7, electrodes 49a and 49b are formed on the surface of the low refractive index film 48 on both sides of the optical waveguide 41 in the optical axis direction of the optical waveguide 41. In this example, the optical axis of the optical waveguide 41 is the x-axis direction, so electrodes 49a and 49b are formed on both sides of the optical waveguide 41 in the x-axis direction (Figure 12(h)). As described above, by providing steps S1 to S7, the optical waveguide device 140 can be manufactured.

[0054] As shown in Figure 12(f), the substrate 40 obtained by removing the mask M is identical to the optical waveguide device 110. Therefore, the optical waveguide device 110 can be manufactured by the steps S1 to S5 described above.

[0055] Furthermore, as shown in Figures 12(a) to (h), the width of the groove formed in step S2 corresponds to the width of the thin-walled portion 42, and the thickness of the thin-walled portion formed in step S2 corresponds to the thickness of the optical waveguide 41. Also, the width of the mask M formed in step S3 corresponds to the width of the optical waveguide 41. Moreover, the thickness of the thin-walled portion 42 is determined by the etching depth in step S4. Therefore, the thickness and width of the optical waveguide 41 and the thin-walled portion 42 can be appropriately designed by adjusting each parameter of the above steps.

[0056] Furthermore, although the low refractive index film 48 was deposited only on the upper surface of the thin-walled portion 42 in step S6, the low refractive index film 48 may also be deposited on both the upper and lower surfaces of the thin-walled portion 42. If the optical axis of the substrate S is in the z-axis direction, the optical waveguide device 150 can then be manufactured by placing electrodes on both the upper and lower low refractive index films in step S7.

[0057] Alternatively, after forming electrodes on the low refractive index film in step S7, another low refractive index film may be deposited on top of those electrodes. By incorporating such a process, an optical waveguide device with electrodes embedded in a low refractive index film can be manufactured.

[0058] [Second manufacturing method] Next, as a second manufacturing method, the manufacturing method for the optical waveguide device 160 will be described with reference to Figures 11 and 13. Figure 13 is a cross-sectional view in the zx plane at each step of the manufacturing process for the optical waveguide device 160. As shown in Figure 11, the manufacturing method for the optical waveguide device 160 also includes steps S1 to S7. Therefore, parts that overlap with the manufacturing method for the optical waveguide device 140 will be omitted from the explanation as appropriate.

[0059] First, in step S1, the substrate S is prepared (Figure 13(a)). In the manufacturing of the optical waveguide device 160, the substrate S is prepared such that the optical axis is in the x-axis direction as shown in Figure 13(a). Next, in step S2, grooves extending in one direction are made in the substrate S to form thin-walled and thick-walled sections. In the second manufacturing method, a mask M is formed on the upper surface of the substrate S, excluding the area where the grooves are formed (Figure 13(b)). Next, the side on which the mask M is formed is etched to form grooves in the substrate S (Figure 13(c)).

[0060] Next, in step S3, a portion of the surface of the formed thin-walled portion is masked along the direction in which the groove extends. In the manufacturing of the optical waveguide device 160, a mask M is formed along the y-axis direction on the surface of the thin-walled portion where the groove is formed (Figure 13(d)).

[0061] Next, in step S4, the masked thin portion is etched to form the optical waveguide 61. At this time, the masked area forms the optical waveguide 61 and the thick portion 63, and the unmasked area forms the thin portion 62 (Figure 13(e)).

[0062] Next, in step S5, all masks M are removed from the etched substrate S (substrate 60). This results in a substrate 60 having optical waveguides 61, thin sections 62, and thick sections 63 (Figure 12(f)).

[0063] Next, in step S6, a low refractive index film 68 is deposited on the substrate 60 so as to cover the optical waveguide 61. In the manufacturing of the optical waveguide device 160, the low refractive index film 68 is deposited so as to cover the upper surface of the thin portion 62 (Figure 13(g)).

[0064] Finally, in step S7, electrodes 69a and 69b are formed on the surface of the low refractive index film 68 on both sides of the optical waveguide 61 in the optical axis direction of the optical waveguide 61 (Figure 12(h)). As described above, by providing steps S1 to S7, the optical waveguide device 160 can be manufactured.

[0065] As shown in Figure 13(f), the substrate 60 obtained by removing the mask M is identical to the optical waveguide device 120. Therefore, the optical waveguide device 120 can be manufactured by the steps S1 to S5 described above.

[0066] Furthermore, as shown in Figures 13(a) to (h), the width of the groove formed in step S2 corresponds to the width of the thin-walled portion 62, and the thickness of the thin-walled portion formed in step S2 corresponds to the thickness of the optical waveguide 61. Also, the width of the mask M formed in step S3 corresponds to the width of the optical waveguide 61. Moreover, the thickness of the thin-walled portion 62 is determined by the etching depth in step S4. Therefore, the thickness and width of the optical waveguide 61 and the thin-walled portion 62 can be appropriately designed by adjusting each parameter of the above steps.

[0067] Furthermore, by combining the first and second manufacturing methods described above, optical waveguide devices of other embodiments or variations thereof can be manufactured. For example, an optical waveguide device 130 can be manufactured by creating grooves on both the upper and lower surfaces of a substrate and etching each surface. In addition, an optical waveguide device 170 can be manufactured by forming a low refractive index film on both the upper and lower surfaces of the thin portion of the optical waveguide device 130 and arranging electrodes on top of it.

[0068] Although the present invention has been specifically described above based on embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence. [Explanation of Symbols]

[0069] 10, 20, 30, 40, 50, 60, 70 circuit boards 11, 21, 31, 41, 51, 61, 71 Optical waveguide 12, 22, 32, 42, 52, 62, 72 Thin-walled section 13, 23, 33, 43, 53, 63, 73 Thick wall part 48, 58, 68, 78 Low refractive index film 49a, 49b, 59a, 59b, 69a, 69b, 79a, 79b electrode 110, 120, 130, 140, 150, 160, 170 Optical waveguide devices L light M Mask S substrate

Claims

1. It comprises a substrate made of electro-optical material, The substrate is integrally formed with a thin-walled portion that extends in one direction, thicker portions that are thicker than the thin-walled portion and provided on both sides of the thin-walled portion, and a ridge-shaped optical waveguide formed along the direction in which the thin-walled portion extends. Optical waveguide devices.

2. The upper surface of the thin-walled portion and the upper surface of the thick-walled portion are flush. The optical waveguide is provided so as to protrude from the upper surface side of the thin-walled portion. The optical waveguide device according to claim 1.

3. The lower surface of the thin-walled portion and the lower surface of the thick-walled portion are flush. The optical waveguide is provided so as to protrude from the upper surface side of the thin-walled portion. The optical waveguide device according to claim 1.

4. The thin-walled portion is provided between the upper and lower surfaces of the thick-walled portion. The optical waveguide is provided so as to protrude from at least one of the upper or lower surfaces of the thin-walled portion. The optical waveguide device according to claim 1.

5. The optical waveguide further comprises a low refractive index film made of a material with a lower refractive index than the optical waveguide, The low refractive index film is provided so as to cover the optical waveguide, The optical waveguide device according to claim 1.

6. The difference between the refractive index of the optical waveguide for light with a wavelength of 1550 nm and the refractive index of the low refractive index film for light with a frequency of 10 GHz is 0.8 or less. The optical waveguide device according to claim 5.

7. The optical axis of the optical waveguide is horizontal to the upper surface of the thin-walled portion and perpendicular to the aforementioned one direction. In the optical axis direction of the optical waveguide, electrodes are provided on both sides of the optical waveguide. The optical waveguide device according to claim 1.

8. The optical axis of the optical waveguide is perpendicular to the upper surface of the thin-walled portion. In the optical axis direction of the optical waveguide, electrodes are provided on both sides of the optical waveguide. The optical waveguide device according to claim 1.

9. The thickness of the thin-walled portion is 500 nm or less. The optical waveguide device according to claim 1.

10. The width of the thin-walled portion is 10 μm or more and 100 μm or less. The optical waveguide device according to claim 1.

11. The steps include preparing a substrate made of electro-optical material, The steps include forming a thin-walled portion and a thick-walled portion by providing the substrate with grooves extending in one direction, The steps include: masking a portion of the surface of the thin-walled portion along the direction in which the groove extends; The steps include etching the masked thin portion to form an optical waveguide, The process includes the step of removing the mask from the etched substrate, A method for manufacturing optical waveguide devices.

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