Ring resonator and manufacturing method therefor

Abstract

To provide a ring resonator that suppresses a nonlinear effect from becoming apparent, and a manufacturing method therefor.SOLUTION: The ring resonator comprises: an input waveguide; an output waveguide; a ring waveguide including a first waveguide section optically connecting to the input waveguide, a second waveguide section optically connecting to the output waveguide, and two curved waveguide sections that respectively connect the first waveguide section and the second waveguide section; and a heater disposed along a third waveguide section which is longer of the two waveguide sections. The lengths of the two waveguide sections are different from each other. A first orientation along the first waveguide section and a second orientation along the second waveguide section are not parallel to each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to ring resonators and methods for manufacturing the same. [Background technology]

[0002] Patent Document 1 discloses a technique for realizing an optical filter using a ring resonator and a heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2022-522796 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 does not describe how to suppress the occurrence of nonlinear phenomena within the ring resonator, and there is a risk that nonlinear effects may become apparent.

[0005] The present disclosure has been made to solve such problems, and has an object to provide a ring resonator that suppresses the manifestation of nonlinear effects, and a method for manufacturing the same. [Means for solving the problem]

[0006] The ring resonator according to the present disclosure comprises: an input waveguide; an output waveguide; and a ring waveguide comprising a first waveguide portion optically connecting to the input waveguide, a second waveguide portion optically connecting to the output waveguide, and two curved waveguide portions each connecting the first waveguide portion and the second waveguide portion; Equipped with the lengths of the two waveguide portions are different from each other; a heater disposed along a third longer waveguide portion of the two waveguide portions; A first orientation along the first waveguide portion and a second orientation along the second waveguide portion are non-parallel to each other.

[0007] A method for manufacturing a ring resonator according to the present disclosure includes: forming an input waveguide, a ring waveguide, and an output waveguide; forming a heater; Including, the ring waveguide comprises a first waveguide portion optically connected to the input waveguide, a second waveguide portion optically connected to the output waveguide, and two curved waveguide portions each connecting the first waveguide portion and the second waveguide portion; the lengths of the two waveguide portions are different from each other; a first orientation along the first waveguide portion and a second orientation along the second waveguide portion are not parallel to each other; The heater is formed along a third waveguide portion that is the longer of the two waveguide portions. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a ring resonator that suppresses the manifestation of nonlinear effects and a method for manufacturing the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic plan view of a ring resonator according to the present disclosure. [Figure 2] FIG. 1 is a schematic cross-sectional view of a ring resonator according to the present disclosure. [Figure 3] FIG. 1 is a schematic cross-sectional view of a ring resonator according to the present disclosure. [Figure 4] FIG. 1 is a schematic plan view of a ring resonator according to the present disclosure. [Figure 5] 1 is a flowchart illustrating a method for manufacturing a ring resonator according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiment 1 The configuration of ring resonator 10 will be described below with reference to Fig. 1. Fig. 1 is a schematic plan view of ring resonator 10. Ring resonator 10 includes an input waveguide 2, a ring waveguide 3, an output waveguide 4, a heater 5, and a heat insulating structure 6.

[0011] The input waveguide 2, the ring waveguide 3, and the output waveguide 4 each include a core through which light propagates. The core is surrounded by a cladding. The core is made of, for example, Si. The cladding is made of, for example, SiO2. The refractive index of the material forming the core is different from the refractive index of the material forming the cladding. The ring resonator 10 may be formed on an SOI (Silicon on Insulator) substrate having a BOX (Buried Oxide) layer. When the core is made of Si and the cladding is made of SiO2, the difference in refractive index between Si and SiO2 is large. Therefore, the bending radius of each waveguide can be reduced to about 10 μm, allowing the ring resonator to be miniaturized.

[0012] The input waveguide 2 is optically connected to the ring waveguide 3. Light is input to one end of the input waveguide 2 (for example, the end on the left side in the figure). A part of the input light propagates to the ring waveguide 3.

[0013] The ring waveguide 3 includes a waveguide portion 31, a waveguide portion 32, a waveguide portion 33, and a waveguide portion 34. The waveguide portions 31, 32, and 33 correspond to the first waveguide portion, the second waveguide portion, and the third waveguide portion, respectively. The waveguide portion 31 is a portion of the ring waveguide 3 included in a region 91. The input waveguide 2 and the ring waveguide 3 are optically connected to each other in the region 91. The waveguide portion 32 is a portion of the ring waveguide 3 included in a region 92. The ring waveguide 3 and the output waveguide 4 are optically connected to each other in the region 92.

[0014] Waveguide portion 31 is optically connected to input waveguide 2. Waveguide portion 32 is optically connected to output waveguide 4. Two curved waveguide portions each connect waveguide portion 31 and waveguide portion 32. Curved means, for example, a shape represented by a line including a continuously curved line. The two waveguide portions have different lengths. Waveguide portion 33 is the longer of the two waveguide portions. Waveguide portion 34 is the shorter of the two waveguide portions. Waveguide portions 33 and 34 are each physically and optically connected to waveguide portions 31 and 32.

[0015] Light input from the waveguide portion 31 circulates in one direction (for example, counterclockwise in the figure) through the ring waveguide 3. Then, light having a wavelength close to the resonance wavelength of the ring waveguide 3 propagates from the waveguide portion 32 to the output waveguide 4.

[0016] Arrow 93 represents the direction along waveguide portion 31. Arrow 94 represents the direction along waveguide portion 32. The direction along waveguide portion 31 (also referred to as the first direction) and the direction along waveguide portion 32 (also referred to as the second direction) are not parallel to each other. Arrow 93 represents the first direction. Arrow 94 represents the second direction. The first direction and the second direction may be perpendicular to each other.

[0017] The ring waveguide 3 has, for example, a racetrack shape. The racetrack shape is composed of two parallel lines and two curved lines connecting the two parallel lines. The two parallel lines are parallel to a first direction or a second direction. The lengths of the two parallel lines are equal. The two parallel lines shown are parallel to the first direction. In the example of FIG. 1, the waveguide portion 31 is at least a part of one of the two parallel lines. In the example of FIG. 1, the waveguide portion 32 is at least a part of one of the two curved lines. In the example of FIG. 1, the waveguide portion 33 includes one of the two parallel lines and one of the two curved lines. In this case, the length of the waveguide contributing to the coupling between the ring waveguide 3 and the output waveguide 4, i.e., the length of the linear waveguide contributing to the coupling of the directional coupler, is relatively short. The ring waveguide 3 may be circular (e.g., perfect circular). The curved line may be a semicircular arc.

[0018] The output waveguide 4 is optically connected to the waveguide portion 32 of the ring waveguide 3. The output waveguide 4 outputs light from one end (for example, the upper end in the figure).

[0019] The heater 5 and the heat insulating structure 6 are arranged along the waveguide portion 33 of the ring waveguide 3. The heater 5 and the heat insulating structure 6 may be arranged along the entire waveguide portion 33. The heat insulating structure 6 is, for example, an air layer or a vacuum layer arranged below the ring waveguide 3 and the heater 5. The arrangement of the heater 5 and the heat insulating structure 6 reduces the power input to the heater 5. The length of the waveguide of the ring waveguide 3 where the heater 5 is arranged may be, for example, half or more of the circumferential length of the ring waveguide 3.

[0020] 2 is a schematic diagram illustrating a first example of the AA cross section of FIG. 1. The ring resonator 10 includes a SiO2 layer 7 formed on a substrate (not shown). The SiO2 layer 7 may include a lower SiO2 layer 71 disposed below the ring waveguide 3 and an upper SiO2 layer 72 formed on the lower SiO2 layer 71. The lower SiO2 layer 71 may be, for example, a BOX layer of an SOI substrate. The ring waveguide 3 is formed of, for example, Si.

[0021] The heater 5 is disposed near the ring waveguide 3. Although the heater 5 is shown disposed on the side of the ring waveguide 3, the heater 5 may be disposed above or below the ring waveguide 3.

[0022] The heater 5 is made of, for example, a metal. When power is applied to the heater 5, the resonance wavelength of the ring waveguide 3 shifts.

[0023] The heat insulating structure 6 in the figure is an air layer disposed below the ring waveguide 3. The air layer is formed, for example, by etching the SiO2 layer 7 on both sides of the ring waveguide 3 in the depth direction to form openings O, and then performing isotropic etching. The heater 5 is located between the openings O and the ring waveguide 3. The heat insulating structure 6 covers the ring waveguide 3 and the heater 5 from below.

[0024] 3 is a schematic diagram showing a second example of the AA cross section of FIG. 1. The heat insulating structure 6 in the figure is a vacuum layer provided below the ring waveguide 3. The vacuum layer is formed, for example, by isotropically etching the lower SiO2 layer 71 on both sides of the ring waveguide 3 in the depth direction before forming the upper SiO2 layer 72. After the vacuum layer is formed, the upper SiO2 layer 72 may be formed on the lower SiO2 layer 71.

[0025] Next, the problem that the present disclosure aims to solve will be specifically described. It is known that when light with high optical intensity is input to ring resonator 10, the transmission spectrum is distorted due to nonlinear phenomena, limiting the optical intensity of the input light. This also limits the optical intensity of the light output from ring resonator 10. However, when heater 5 and thermal insulation structure 6 are arranged along ring waveguide 3, the filtering function of ring resonator 10 can be realized with low power consumption. However, when heater 5 and thermal insulation structure 6 are provided, there is a problem in that nonlinear phenomena become apparent at lower optical power.

[0026] More specifically, when the core is made of Si and the cladding is made of SiO2, the ring waveguide 3 heats up due to two-photon absorption, a nonlinear phenomenon. It is known that two-photon absorption does not occur in SiO2 or Si3N4 waveguides, but does occur in Si waveguides. The thermal insulation structure 6 increases the change in the refractive index of the waveguide due to heating. This significantly distorts the shape of the transmission spectrum of the ring resonator 10. In other words, there is a trade-off between the reduction in power consumption achieved by adding the thermal insulation structure 6 and the distortion of the transmission spectrum due to two-photon absorption.

[0027] Next, the effects of the present disclosure will be described with reference to Figure 1. Light propagated from input waveguide 2 to waveguide portion 31 of ring waveguide 3 is guided by waveguide portion 34, and part of the light propagates from waveguide portion 32 to output waveguide 4. Therefore, the optical intensity of light guided by waveguide portion 33 is reduced to a certain extent. This makes it possible to suppress the manifestation of nonlinear phenomena caused by heater 5 and thermal insulation structure 6. Furthermore, if the length of waveguide portion 33 in which heater 5 and thermal insulation structure 6 are arranged is sufficiently long, low power consumption can also be achieved.

[0028] Embodiment 2 The configuration of the ring resonator 1 will be described using Figure 4. Comparing Figure 1 with Figure 4, the ring resonator 1 does not need to include the heat insulating structure 6. Each waveguide only needs to be made of a material in which a nonlinear optical phenomenon can occur. The ring resonator 1 can suppress the manifestation of nonlinear phenomena.

[0029] A method for manufacturing the ring resonator 1 will be described with reference to FIG. 5. In step S11, the input waveguide 2, ring waveguide 3, and output waveguide 4 are formed. The input waveguide 2, ring waveguide 3, and output waveguide 4 are formed, for example, by forming a resist pattern by lithography and etching the SOI substrate using the resist as a mask. After etching the SOI substrate, an upper SiO2 layer 72 may be formed.

[0030] In step S12, the heater 5 is formed along the waveguide portion 33 (third waveguide portion) of the ring waveguide 3. The heater 5 may be formed, for example, by forming a resist pattern by lithography, depositing a metal film, and then peeling off the resist. Alternatively, the heater 5 may be formed by depositing a metal film and then etching the metal film.

[0031] The order of steps S11 and S12 may be reversed. The method for manufacturing the ring resonator 1 may also include forming a heat insulating structure 6 along the waveguide portion 33. The heat insulating structure 6 may include forming an opening in the SiO2 layer using a resist or the like as a mask, and performing isotropic etching after the opening is formed.

[0032] The manufacturing method shown in FIG. 5 can manufacture a ring resonator that suppresses the manifestation of nonlinear phenomena.

[0033] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0034] Each drawing is merely an example for describing one or more embodiments. Each drawing may relate not only to one particular embodiment, but also to one or more other embodiments. As will be understood by those skilled in the art, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings to create, for example, an embodiment not explicitly shown or described. Not all features or steps shown in any one drawing are necessary to describe an exemplary embodiment, and some features or steps may be omitted. The order of steps described in any drawing may be changed as appropriate.

[0035] Some or all of the elements (e.g., configurations and functions) described in Supplementary Notes 2 to 9 that are dependent on Supplementary Note 1 may also be dependent on Supplementary Note 10 in the same dependent relationship as Supplementary Notes 2 to 9. Some or all of the elements described in any Supplementary Note may be applied to various hardware, software, recording means for recording software, systems, and methods.

[0036] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes. (Appendix 1) an input waveguide; an output waveguide; and a ring waveguide comprising a first waveguide portion optically connecting to the input waveguide, a second waveguide portion optically connecting to the output waveguide, and two curved waveguide portions each connecting the first waveguide portion and the second waveguide portion; Equipped with the lengths of the two waveguide portions are different from each other; a heater disposed along a third longer waveguide portion of the two waveguide portions; A first direction along the first waveguide portion and a second direction along the second waveguide portion are not parallel to each other. Ring resonator. (Appendix 2) The first direction and the second direction are perpendicular to each other. 2. The ring resonator of claim 1. (Appendix 3) and a heat insulating structure disposed along the third waveguide portion. 3. The ring resonator of claim 1 or 2. (Appendix 4) The heat insulating structure covers the ring waveguide and the heater from below. 4. The ring resonator of claim 3. (Appendix 5) The ring waveguide includes a core made of Si. 3. The ring resonator of claim 1 or 2. (Appendix 6) the ring waveguide is composed of two parallel lines and two curved lines connecting the two parallel lines; the two parallel lines are parallel to the first direction or the second direction; The two parallel lines are equal in length 3. The ring resonator of claim 2. (Appendix 7) the first waveguide portion is at least a part of one of the two parallel lines; The second waveguide portion is at least a portion of one of the two curves. 7. The ring resonator of claim 6. (Appendix 8) The third waveguide portion includes one of the two parallel lines and one of the two curved lines. 7. The ring resonator of claim 6. (Appendix 9) The heater is disposed along the entire third waveguide portion. 3. The ring resonator of claim 1 or 2. (Appendix 10) forming an input waveguide, a ring waveguide, and an output waveguide; forming a heater; Including, the ring waveguide comprises a first waveguide portion optically connecting to the input waveguide, a second waveguide portion optically connecting to the output waveguide, and two waveguide portions each connecting the first waveguide portion and the second waveguide portion; the lengths of the two waveguide portions are different from each other; a first orientation along the first waveguide portion and a second orientation along the second waveguide portion are not parallel to each other; The heater is formed along the third waveguide portion, which is the longer of the two waveguide portions. Method for manufacturing a ring resonator. [Explanation of symbols]

[0037] 1, 10 Ring resonator 2. Input waveguide 3 Ring waveguide 31, 32, 33, 34 Waveguide section 4 Output waveguide 5 Heater 6. Insulated structure 7 SiO2 layer 71 Lower SiO2 layer 72 Upper SiO2 layer 91, 92 area 93, 94 Arrows

Claims

1. an input waveguide; an output waveguide; and a ring waveguide comprising a first waveguide portion optically connecting to the input waveguide, a second waveguide portion optically connecting to the output waveguide, and two curved waveguide portions each connecting the first waveguide portion and the second waveguide portion; Equipped with the two waveguide portions have different lengths; a heater disposed along a third longer waveguide portion of the two waveguide portions; A first orientation along the first waveguide portion and a second orientation along the second waveguide portion are not parallel to each other. Ring resonator.

2. The first orientation and the second orientation are perpendicular to each other. The ring resonator of claim 1 .

3. a heat insulating structure disposed along the third waveguide portion; 3. The ring resonator according to claim 1.

4. The heat insulating structure covers the ring waveguide and the heater from below. The ring resonator of claim 3 .

5. The ring waveguide includes a core made of Si.

3. The ring resonator according to claim 1.

6. the ring waveguide is composed of two parallel lines and two curved lines connecting the two parallel lines, the two parallel lines are parallel to the first direction or the second direction; The two parallel lines are equal in length The ring resonator of claim 2 .

7. the first waveguide portion is at least a part of either one of the two parallel lines; The second waveguide portion is at least a portion of one of the two curves. The ring resonator of claim 6 .

8. The third waveguide portion includes one of the two parallel lines and one of the two curved lines. The ring resonator of claim 6 .

9. The heater is disposed along the entire third waveguide portion.

3. The ring resonator according to claim 1.

10. forming an input waveguide, a ring waveguide, and an output waveguide; forming a heater; Including, the ring waveguide comprises a first waveguide portion optically connected to the input waveguide, a second waveguide portion optically connected to the output waveguide, and two curved waveguide portions each connecting the first waveguide portion and the second waveguide portion; the two waveguide portions have different lengths; a first orientation along the first waveguide portion and a second orientation along the second waveguide portion are not parallel to each other; The heater is formed along the third waveguide portion, which is the longer of the two waveguide portions. Method for manufacturing a ring resonator.

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