Isolator and method for manufacturing an isolator

Abstract

To provide an isolator that reduces the impact of YIG in a semiconductor process, and a method for manufacturing the isolator.SOLUTION: An isolator 10 comprises: a substrate 50 that has a substrate surface 50A; waveguides 21, 22 that are located on the substrate surface 50A and have first surfaces 211, 221 that face the substrate surface 50A, second surfaces 212, 222 that are reverse thereto, and side surfaces 213, 223; a groove 30 that has a bottom part and a side part where at least some of the side surfaces 213, 223 of the waveguides 21, 22 is exposed; a mask 40 that is located overlapping a region of the second surfaces 212, 222 of the waveguides 21, 22 that is at least in contact with the groove 30 as seen from the normal direction of the substrate surface 50A; and a non-reciprocity member 31 that is located so as to be in contact with the side surfaces 213, 223 of the waveguides 21, 22 in the groove 30.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an isolator and a method for manufacturing the isolator.

Background Art

[0002] An optical isolator using a magneto-optical material Ce:YIG as a waveguide layer is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When forming an isolator using YIG as a waveguide layer on a semiconductor substrate, it is required to reduce the influence of YIG in the semiconductor process.

[0005] An object of the present disclosure is to provide an isolator and a method for manufacturing the same that reduce the influence of YIG in the semiconductor process.

Means for Solving the Problems

[0006] An isolator according to an embodiment of the present disclosure includes a substrate having a substrate surface, a waveguide, a groove, a mask, and a non-reciprocal member. The waveguide is located on the substrate surface and has a first surface facing the substrate surface, a second surface located on the opposite side of the first surface, and a side surface connecting the first surface and the second surface. The groove has a bottom and a side portion where at least a part of the side surface of the waveguide is exposed. The mask is positioned so as to overlap at least a region of the second surface of the waveguide that contacts the groove when viewed from the normal direction of the substrate surface. The non-reciprocal member is positioned so as to contact the side surface of the waveguide in the groove.

[0007] A method for manufacturing an isolator according to one embodiment of the present disclosure includes forming a waveguide on a substrate having a substrate surface, forming an insulating layer and a mask on the waveguide, etching the insulating layer to form a groove so as to expose the side surface of the waveguide, forming a non-reciprocal member in the groove, and irradiating the non-reciprocal member with laser light such that the transmittance of the mask is less than a transmission threshold. [Effects of the Invention]

[0008] According to an isolator and a method for manufacturing the same as one embodiment of the present disclosure, the influence of YIG in semiconductor processes can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view showing an example configuration of an isolator according to one embodiment. [Figure 2] This is a cross-sectional view AA in Figure 1. [Figure 3] This is a plan view showing an example configuration in which a groove is located between the first waveguide and the second waveguide. [Figure 4] Figure 2 is a cross-sectional view of BB. [Figure 5] This is a plan view showing an example configuration in which waveguides are arranged in a zigzag pattern within a roughly circular laser irradiation area, and a groove that is in common contact with the first and second waveguides. [Figure 6] This is a plan view showing an example configuration in which waveguides are arranged in a zigzag pattern within a roughly circular laser irradiation area, and does not include a groove that is in common contact with the first and second waveguides. [Figure 7] This is a cross-sectional view showing an example configuration in which the bottom of the groove is lower than the first surface of the waveguide. [Figure 8] This is a cross-sectional view showing an example configuration in which an absorbent member is further provided on top of a non-reciprocal member. [Figure 9] This is a cross-sectional view showing an example configuration in which the mask does not overlap with at least a portion of the edge of the second surface of the waveguide that is located on the groove side, in a plan view. [Figure 10]In FIG. 9, it is a cross-sectional view in which the cross-sectional shape of the waveguide is a rib shape. [Figure 11] It is a cross-sectional view showing a configuration example in which a non-reciprocal member is formed only on one side of the two sides of the groove. [Figure 12] It is a plan view showing a configuration example of an isolator further provided with a heater. [Figure 13A] It is a cross-sectional view showing a process of forming a waveguide on a substrate. [Figure 13B] It is a cross-sectional view showing a process of forming a first insulating layer on the waveguide. [Figure 13C] It is a cross-sectional view showing a process of forming a mask on the first insulating layer. [Figure 13D] It is a cross-sectional view showing a process of forming a second insulating layer on the mask. [Figure 13E] It is a cross-sectional view showing a process of forming a groove so that the side surface of the waveguide is exposed. [Figure 13F] It is a cross-sectional view showing a process of forming a non-reciprocal member in the groove.

Embodiments for Carrying Out the Invention

[0010] (Configuration Example of Isolator 10) As shown in FIGS. 1 and 2, an isolator 10 according to an embodiment includes a first waveguide 21, a second waveguide 22, a non-reciprocal member 31, a mask 40, a first branch portion 81, and a second branch portion 82. The first waveguide 21 and the second waveguide 22 are also simply referred to as waveguides.

[0011] The isolator 10 is configured to transmit a TE-mode electromagnetic wave input to the first branch portion \alpha to the second branch portion 82 and block a TE-mode electromagnetic wave input to the second branch portion 82 and not transmit it to the first branch portion 81. The direction in which the electromagnetic wave propagates from the first branch portion 81 to the second branch portion 82 is also referred to as the first direction. The direction in which the electromagnetic wave propagates from the second branch portion 82 to the first branch portion E is also referred to as the second direction. That is, the isolator 10 transmits a TE-mode electromagnetic wave in the first direction and does not transmit it in the second direction.

[0012] The isolator 10 realizes the propagation characteristics of an asymmetric electromagnetic wave by using the principle of an asymmetric Mach-Zehnder interferometer. The isolator 10 is configured such that the phase shift of the electromagnetic wave propagating in the first waveguide 21 in the first direction is the same as the phase shift of the electromagnetic wave propagating in the second waveguide 22 in the first direction. Also, the isolator 10 is configured such that there is a difference corresponding to 1 / 4 of the wavelength (90-degree phase) between the phase shift of the electromagnetic wave propagating in the first waveguide 21 in the second direction and the phase shift of the electromagnetic wave propagating in the second waveguide 22 in the second direction.

[0013] The phase shift can be adjusted by the line length of the waveguide or by the effective refractive index of the waveguide. Assume that the isolator 10 is configured such that the phase of the electromagnetic wave propagating in the first waveguide 21 lags behind the phase of the electromagnetic wave propagating in the second waveguide 22 by 90 degrees when the non-reciprocal member 31 is absent. When the non-reciprocal member 31 is absent, the phase of the electromagnetic wave propagating in the first waveguide 21 lags behind the phase of the electromagnetic wave propagating in the second waveguide 22 by 90 degrees whether the electromagnetic wave propagates through the isolator 10 in the first direction or in the second direction. Therefore, even if only the line length or the effective refractive index of the waveguide is set, the way the phase of the electromagnetic wave propagating in the first direction shifts is the same as the way the phase of the electromagnetic wave propagating in the second direction shifts. Thus, the isolator 10 includes a non-reciprocal member 31 positioned along at least a part of the waveguide so as to make the phase shift of the electromagnetic wave propagating in the first direction of the waveguide different from the phase shift of the electromagnetic wave propagating in the second direction of the waveguide. The waveguide including the non-reciprocal member 31 functions as a non-reciprocal waveguide by the application of a magnetic field.

[0014] Non-reciprocal waveguides advance or delay the phase of propagating electromagnetic waves. In this embodiment, the isolator 10 delays the phase of the electromagnetic wave by an amount equivalent to 1 / 8 of the wavelength (a 45-degree phase) when the non-reciprocal member 31 is located on the right side of the waveguide when the waveguide is viewed in the direction of electromagnetic wave propagation. Conversely, the isolator 10 advances the phase of the electromagnetic wave by an amount equivalent to 1 / 8 of the wavelength (a 45-degree phase) when the non-reciprocal member 31 is located on the left side of the waveguide when the waveguide is viewed in the direction of electromagnetic wave propagation.

[0015] In the example in Figure 1, when the electromagnetic wave propagates in the first direction (the positive direction of the X-axis in Figure 1), the non-reciprocal member 31 is located to the left of the first waveguide 21 in the first direction. Also, the non-reciprocal member 31 is located to the right of the second waveguide 22 in the first direction. Therefore, the phase of the electromagnetic wave propagating in the first direction advances by 45 degrees in the first waveguide 21 and lags by 45 degrees in the second waveguide 22. As described above, the isolator 10 is configured such that, when the non-reciprocal member 31 is absent, the phase of the electromagnetic wave propagating in the first direction through the first waveguide 21 lags by 90 degrees compared to the phase of the electromagnetic wave propagating in the first direction through the second waveguide 22. In this case, the phase lag of the electromagnetic wave propagating in the first direction through the first waveguide 21 becomes 45 degrees. On the other hand, the phase lag of the electromagnetic wave propagating in the first direction through the second waveguide 22 becomes 45 degrees. As a result, the difference between the phase shift of the electromagnetic wave propagating through the first waveguide 21 in the first direction and the phase shift of the electromagnetic wave propagating through the second waveguide 22 in the first direction becomes 0 degrees. In other words, the phase shift of the electromagnetic wave propagating through the first waveguide 21 in the first direction and the phase shift of the electromagnetic wave propagating through the second waveguide 22 in the first direction become the same.

[0016] On the other hand, when electromagnetic waves propagate in the second direction (the negative direction of the X-axis in Figure 1), the non-reciprocal member 31 is located to the right of the first waveguide 21 in the direction of the second direction. Also, the non-reciprocal member 31 is located to the left of the second waveguide 22 in the direction of the second direction. Therefore, the phase of the electromagnetic wave propagating in the second direction lags by 45 degrees in the first waveguide 21 and advances by 45 degrees in the second waveguide 22. As described above, the isolator 10 is configured such that, when the non-reciprocal member 31 is not present, the phase of the electromagnetic wave propagating in the second direction through the first waveguide 21 lags by 90 degrees compared to the phase of the electromagnetic wave propagating in the second direction through the second waveguide 22. In this case, the phase lag of the electromagnetic wave propagating in the second direction through the first waveguide 21 becomes 135 degrees. On the other hand, the phase advance of the electromagnetic wave propagating in the second direction through the second waveguide 22 becomes 45 degrees. As a result, the difference between the phase shift of the electromagnetic wave propagating through the first waveguide 21 in the second direction and the phase shift of the electromagnetic wave propagating through the second waveguide 22 in the first direction becomes 180 degrees.

[0017] In the isolator 10 configured as described above, the phase difference between the electromagnetic wave propagating in the first waveguide 21 and the electromagnetic wave propagating in the second waveguide 22 is 0 degrees when propagating in the first direction and 180 degrees when propagating in the second direction. In this way, the isolator 10 is configured to transmit electromagnetic waves propagating in the first direction but not transmit electromagnetic waves propagating in the second direction.

[0018] The waveguide and non-reciprocal member 31 of the isolator 10 are formed on a substrate 50 having a substrate surface 50A. The substrate 50 may be composed of a conductor such as metal, a semiconductor such as silicon, glass, or resin. In this embodiment, the substrate 50 is assumed to be silicon (Si), but it is not limited to this and may be made of various other materials.

[0019] The substrate 50 includes a box layer 52 made of an insulator such as a silicon oxide film on the substrate surface 50A. The waveguide is located on the box layer 52. The first waveguide 21 has a first surface 211 located on the side facing the substrate surface 50A, a second surface 212 located on the opposite side of the first surface 211, and a side surface 213 connecting the first surface 211 and the second surface 212. The second waveguide 22 has a first surface 221 located on the side facing the substrate surface 50A, a second surface 222 located on the opposite side of the first surface 221, and a side surface 223 connecting the first surface 221 and the second surface 222. The substrate 50 further includes a first insulating layer 54 located on the waveguide. The substrate 50 further includes a mask 40 located on the first insulating layer 54. The substrate 50 further includes a second insulating layer 56 located on the mask 40.

[0020] The waveguide is surrounded by a box layer 52, a first insulating layer 54, and a non-reciprocal member 31. The waveguide is also called the core. The box layer 52 and the first insulating layer 54 are also called the cladding. The core and cladding may be composed of a dielectric material. The waveguide is also called a dielectric line. The materials of the core and cladding are determined such that the relative permittivity of the core is greater than that of the cladding. In other words, the materials of the core and cladding are determined such that the refractive index of the cladding is greater than that of the core. In this way, electromagnetic waves propagating through the core can be totally reflected at the boundary with the cladding. As a result, the loss of electromagnetic waves propagating through the core can be reduced.

[0021] The relative permittivity of the core and cladding may be greater than that of air. By making the relative permittivity of the core and cladding greater than that of air, leakage of electromagnetic waves from the isolator 10 can be suppressed. As a result, losses due to electromagnetic waves radiated from the isolator 10 to the outside can be reduced.

[0022] In this embodiment, the material of the waveguide as the core is silicon (Si), but it is not limited to this and may be various other materials. The material of the box layer 52 and the first insulating layer 54 as cladding is quartz glass or silicon oxide film (SiO2), but it is not limited to this and may be various other materials. The relative permittivity of silicon and quartz glass is about 12 and about 2, respectively. Silicon can propagate electromagnetic waves having near-infrared wavelengths of about 1.2 μm to about 6 μm with low loss. When the waveguide is made of silicon, it can propagate electromagnetic waves having wavelengths in the 1.3 μm band or 1.55 μm band used in optical communication with low loss.

[0023] The isolator 10 includes grooves 30 formed by etching the first insulating layer 54. The grooves 30 extend along the waveguide. The grooves 30 have a bottom and a side in a cross-section (Figure 2) viewed in the direction of their extension (X-axis direction in Figure 1). The grooves 30 located along the first waveguide 21 are formed such that their side exposes at least a portion of the side surface 213 of the first waveguide 21. The grooves 30 located along the second waveguide 22 are formed such that their side exposes at least a portion of the side surface 223 of the second waveguide 22. The position of the bottom of the grooves 30 may be substantially the same as the position of the bottom surface of the waveguide (the first surface 211 of the first waveguide 21 or the first surface 221 of the second waveguide 22).

[0024] The non-reciprocal member 31 is formed by depositing a film on the bottom and sides of the groove 30. In the groove 30 located along the first waveguide 21, the non-reciprocal member 31 contacts the side surface 213 of the first waveguide 21. In the groove 30 located along the second waveguide 22, the non-reciprocal member 31 contacts the side surface 223 of the second waveguide 22.

[0025] The groove 30 may be composed of two stages: a portion located on the first insulating layer 54 and a portion located on the second insulating layer 56. The width of the groove 30 in the second insulating layer 56 (dimension in the Y-axis direction in Figure 2) is wider than the width of the groove 30 in the first insulating layer 54. This makes it easier for the non-reciprocal member 31 to be deposited up to the portion where the waveguide is exposed. The non-reciprocal member 31 may be deposited with the substrate 50 tilted in the positive or negative direction of the Y-axis so that it is deposited up to the portion where the bottom and side of the groove 30 intersect.

[0026] In this embodiment, Ce:YIG (cerium-substituted yttrium iron garnet) is used as the material for the non-reciprocal member 31. A transparent magnetic material such as a partially substituted YIG, such as Bi:YIG (bismuth-substituted YIG), may also be used as the material for the non-reciprocal member 31. A ferromagnetic material such as FeCo, FeNi, or CoPt, or a material containing a ferromagnetic material, may also be used as the material for the non-reciprocal member 31. A dielectric material composited with magnetic nanoparticles, such as a nanogranular material, may also be used as the material for the non-reciprocal member 31. However, various other magnetic materials may be used as the non-reciprocal member 31, although these are not limited to the above.

[0027] The YIG-based non-reciprocal member 31 exhibits sufficient non-reciprocity when its crystallization progresses sufficiently. Crystallization of the non-reciprocal member 31 progresses when it is heated above a predetermined temperature. However, considering the impact on other components such as waveguides or wiring formed on the substrate 50, it is difficult to heat the entire substrate 50 above a predetermined temperature when depositing the non-reciprocal member 31. Therefore, the non-reciprocal member 31 formed in the groove 30 by film deposition without heating the substrate 50 is not sufficiently crystallized and does not exhibit sufficient non-reciprocity in that state.

[0028] Therefore, in the isolator 10 according to this embodiment, the non-reciprocal member 31 is heated by irradiation with laser light in order to crystallize the non-reciprocal member 31. As the laser light, light of a wavelength that has a high absorption efficiency of light by the non-reciprocal member 31 is used. When the non-reciprocal member 31 is Ce:YIG, it has a high absorption efficiency of visible light. Therefore, a visible light laser may be used for heating.

[0029] The laser beam spreads within a finite range at the irradiation point due to optical limitations. The irradiation range of the laser beam is wider than the width of the groove 30. In the isolator 10 according to this embodiment, the mask 40 is configured such that the transmittance of the laser beam is less than the transmission threshold, or the reflectance of the laser beam is greater than or equal to the reflection threshold. For example, a metal such as aluminum may be used as the material of the mask 40. However, various materials are not limited to these and can be used as the material of the mask 40. The mask 40 is positioned so as to overlap with at least the region of the second surface 212 or 222 of the waveguide that is in contact with the groove 30 in a plan view of the substrate 50 (when viewed from the direction normal to the substrate surface 50A). In other words, in a plan view of the substrate 50, the mask 40 is positioned to overlap with the waveguide and not with the groove 30. Because the mask 40 is positioned to overlap with the waveguide, the laser beam irradiated onto the substrate 50 from the side of the substrate surface 50A has difficulty reaching the waveguide. Because the mask 40 does not overlap the groove 30, the laser light can more easily reach the non-reciprocal member 31 inside the groove 30. As a result, only the non-reciprocal member 31 inside the groove 30 is more easily heated by the irradiation of the laser light.

[0030] As described above, in the isolator 10 according to this embodiment, the non-reciprocal member 31 is heated in such a way that it does not easily affect other components of the substrate 50. In this way, even when a material that requires heat treatment is used as the non-reciprocal member 31, the impact on the semiconductor process can be reduced. Furthermore, the performance of the isolator 10 can be improved.

[0031] The performance of the isolator 10 may change depending on the degree of crystallization of the non-reciprocal member 31. After the completion of the isolator 10, additional laser light may be irradiated to adjust its performance. By including the mask 40 in the isolator 10 according to this embodiment, the influence on other components of the non-reciprocal member 31 can be reduced even if additional laser light is irradiated.

[0032] As shown in Figures 3 and 4, the groove 30 may be positioned along both the first waveguide 21 and the second waveguide 22. This reduces the area occupied by the isolator 10 on the substrate 50. In other words, the isolator 10 can be miniaturized. The side of the groove 30 that exposes at least a portion of the side surface 213 of the first waveguide 21 is also referred to as the first side. The side of the groove 30 that exposes at least a portion of the side surface 223 of the second waveguide 22 is also referred to as the second side.

[0033] As shown in Figures 5 and 6, the waveguides may be arranged in a zigzag pattern. In other words, the waveguides may have portions in which the direction of extension changes. The waveguides may be located in a zigzag pattern within a substantially circular region. The waveguides may be arranged so as to fall within a substantially circular laser irradiation region LS. In this way, the laser light can be effectively utilized to heat the non-reciprocal member 31. In addition, the laser light is less likely to irradiate other components of the isolator 10 on the substrate 50.

[0034] Waveguides may be arranged such that portions with electromagnetic wave propagation directions differing by 180 degrees are aligned. Grooves 30 may be placed between portions of the waveguide with electromagnetic wave propagation directions differing by 180 degrees. In this way, non-reciprocal members 31 located on both sides of one groove 30 can be utilized to make the waveguide function as a non-reciprocal waveguide.

[0035] The isolator 10 may be configured such that the groove 30 is located between the first waveguide 21 and the second waveguide 22, as shown in Figure 5, or it may be configured such that the groove 30 is not located between the first waveguide 21 and the second waveguide 22, as shown in Figure 6. This can increase the design flexibility of the isolator 10. Furthermore, even if the non-reciprocal members 31 deposited on the two sides of the groove 30 become asymmetrical due to the location of separate grooves 30 in the first waveguide 21 and the second waveguide 22, as shown in Figure 6, this effect can be reduced because the waveguides pass through both sides of the groove 30.

[0036] As shown in Figure 7, the groove 30 may be formed such that its bottom is lower than the first waveguide 21. In other words, the groove 30 may be configured such that the portion of the waveguide that is exposed is away from the bottom of the groove 30. When a non-reciprocal member 31 is deposited inside the groove 30, it is difficult for the non-reciprocal member 31 to enter the portion where the bottom and side intersect. By separating the portion of the waveguide that is exposed from the bottom, the non-reciprocal member 31 is more easily deposited on the exposed portion of the waveguide. In this way, the characteristics of the non-reciprocal member 31 that is in contact with the waveguide can be more easily controlled. As a result, the performance of the isolator 10 can be improved.

[0037] As shown in Figure 8, an absorbing member 32 may be formed on top of the non-reciprocal member 31 formed in the groove 30. A material with high laser light absorption efficiency is used as the absorbing member 32. Alternatively, a material having different absorption characteristics from the non-reciprocal member 31 may be used. Carbon or the like, which has high infrared light absorption efficiency, may be used as the absorbing member 32.

[0038] As shown in Figure 9, in a plan view of the substrate 50, the mask 40 may be positioned so as not to overlap with a portion of the waveguide. This makes the waveguide more easily exposed on the side of the groove 30 and more easily in contact with the non-reciprocal member 31. As a result, the performance of the isolator 10 may be more stable. In addition, the manufacturing process of the isolator 10 may be simplified. As shown in Figure 10, the cross-sectional shape of the waveguide may be rib-shaped.

[0039] As described above, the non-reciprocal member 31 deposited in the groove 30 may be asymmetrical on both sides of the groove 30. As shown in Figure 11, the non-reciprocal member 31 may be deposited on only one of the two sides of the groove 30. In this case, the non-reciprocal member 31 is not in contact with the waveguide located on the right side of the groove 30. However, the waveguides on both sides of the groove 30 are connected in series. Therefore, the length of the waveguide as a whole that is in contact with the non-reciprocal member 31 can be adjusted in either the first waveguide 21 or the second waveguide 22. By depositing the non-reciprocal member 31 on only one side of the groove 30, the non-reciprocal member 31 on one side of the groove 30 can be stably deposited. As a result, the performance of the isolator 10 can be improved.

[0040] The phase of electromagnetic waves propagating through a waveguide also changes with the waveguide temperature. The isolator 10 may control the waveguide temperature to adjust the phase of the electromagnetic waves. As shown in Figure 12, the isolator 10 may further include heaters 71 and 72 that control the temperatures of portions of the first waveguide 21 and the second waveguide 22, respectively. Heater 71 can control the temperature of a portion of the first waveguide 21. Heater 72 can control the temperature of a portion of the first waveguide 21. In this way, the isolator 10 can compensate for the phase by temperature control even if there is an error in the line length of the waveguide formed on the substrate 50. As a result, the performance of the isolator 10 can be improved.

[0041] In Figure 12, in the section where heaters 71 and 72 are located, the waveguide is bent 180 degrees with a small radius of curvature. By bending the waveguide with such a small radius of curvature, TM mode electromagnetic waves passing through this section are radiated outwards and removed. The combination of the waveguide of the isolator 10 and the non-reciprocal member 31 according to this embodiment exhibits non-reciprocity with respect to TE mode electromagnetic waves. Therefore, by having a section that removes TM mode electromagnetic waves, it is possible to prevent TM mode electromagnetic waves from propagating from the second branching section 82 toward the first branching section 81. The section that removes TM mode electromagnetic waves is also collectively referred to as the filter section. As the filter section, in addition to the configuration in which the waveguide is bent with a small radius of curvature, a directional coupler that does not couple TM mode electromagnetic waves may also be used.

[0042] The isolator 10 may be configured such that the distance at which the first waveguide 21 is in contact with the non-reciprocal member 31 is equal to the distance at which the second waveguide 22 is in contact with the non-reciprocal member 31. This makes it easier to adjust the phase. As a result, the performance of the isolator 10 may be improved.

[0043] (Method for manufacturing isolator 10) The manufacturing method of the isolator 10 according to this embodiment will be explained with reference to the cross-sectional views illustrated in Figures 13A to 13F.

[0044] As shown in Figure 13A, a first waveguide 21 and a second waveguide 22 are formed on the box layer 52 of the substrate 50. The waveguides may be formed by a combination of a film deposition process and an etching process. As the film deposition process, plasma CVD (Chemical Vapor Deposition) or sputtering may be performed. As the etching process, dry etching such as RIE (Reactive Ion Etching) or wet etching may be performed.

[0045] As shown in Figure 13B, a first insulating layer 54 is formed on the first waveguide 21 and the second waveguide 22. The first insulating layer 54 may be formed by plasma CVD or the like. As shown in Figure 13C, a mask 40 is formed on the first insulating layer 54. The mask 40 may be formed by a combination of a film formation process and an etching process. As shown in Figure 13D, a second insulating layer 56 is formed on the mask 40. The second insulating layer 56 may be formed by plasma CVD or the like.

[0046] As shown in Figure 13E, a groove 30 is formed. The groove 30 may be formed by dry etching. The portion of the groove 30 formed in the first insulating layer 54 is formed by performing dry etching using the mask 40 as an etching mask. Wet etching may be further performed so that the waveguide is exposed on the side of the groove 30.

[0047] As shown in Figure 13F, non-reciprocal members 31 are formed on the sides and bottom of the groove 30. The non-reciprocal members 31 may be formed by sputtering or the like. Furthermore, the non-reciprocal members 31 are irradiated with laser light. The non-reciprocal members 31 are heated by the irradiation with laser light. By controlling the temperature and heating time of the non-reciprocal members 31, the degree of crystallization of the non-reciprocal members 31 can be controlled.

[0048] As explained above with reference to Figures 13A to 13F, the isolator 10 can be manufactured. Even after completion, the characteristics of the isolator 10 can be adjusted by irradiating it with additional laser light.

[0049] (Examples of applications for Isolator 10) The isolator 10 may be used in combination with a configuration for transmitting electromagnetic waves. The isolator 10 may be applied to an optical switch, an optical transceiver, or a data center. The isolator 10 may be applied to, for example, an electromagnetic wave transmitter. The electromagnetic wave transmitter comprises the isolator 10 and a light source. The electromagnetic wave transmitter inputs electromagnetic waves from the light source to the isolator 10 and outputs electromagnetic waves from the isolator 10 toward a receiver. The isolator 10 is configured such that the transmittance of electromagnetic waves propagating from the light source toward the receiver is greater than the transmittance of electromagnetic waves propagating from the receiver toward the light source. In this way, it is difficult for electromagnetic waves to incident toward the light source. As a result, the light source can be protected.

[0050] The light source may be, for example, a semiconductor laser such as an LD (Laser Diode) or a VCSEL (Vertical Cavity Surface Emitting Laser). The light source may include a device that emits electromagnetic waves of various wavelengths, not limited to visible light. The light source may be formed on the substrate 50 together with the isolator 10. The light source may input TE mode electromagnetic waves to the isolator 10.

[0051] The electromagnetic wave transmitter may further include a modulator and a signal input section. The modulator modulates by changing the intensity of the electromagnetic wave. The modulator may be located between the isolator 10 and the receiver, rather than between the light source and the isolator 10. The modulator may, for example, pulse-modulate the electromagnetic wave. The signal input section receives signals from external devices, etc. The signal input section may include, for example, a D / A converter. The signal input section outputs a signal to the modulator. The modulator modulates the electromagnetic wave based on the signal acquired by the signal input section.

[0052] The light source may include a modulator and a signal input unit. In this case, the light source may output a modulated electromagnetic wave and input it to the isolator 10.

[0053] The electromagnetic wave transmitter may be mounted on the circuit board 50. The light source may be mounted to connect to the first branch 81 via a modulator. The light source may be mounted to connect to the first branch 81 without a modulator. The receiver may be mounted to connect to the second branch 82 without a modulator. The receiver may be mounted to connect to the second branch 82 via a modulator. In this case, the modulator may be mounted to connect to the second branch 82.

[0054] While embodiments relating to this disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications or alterations are within the scope of this disclosure. For example, the functions included in each component can be rearranged in a logically consistent manner, and multiple components can be combined into one or separated.

[0055] In this disclosure, the terms "First," "Second," etc., are identifiers used to distinguish the configurations. Configurations distinguished by the terms "First," "Second," etc., in this disclosure may have their numbers swapped. For example, the first waveguide 21 may swap the identifiers "First" and "Second" with the second waveguide 22. The identifier swapping occurs simultaneously. The configurations remain distinguishable even after the identifier swapping. Identifiers may be deleted. Configurations from which identifiers have been deleted are distinguished by codes. The terms "First," "Second," etc., in this disclosure should not be used alone to interpret the order of the configurations or to justify the existence of smaller numbered identifiers.

[0056] In this disclosure, the X, Y, and Z axes are provided for explanatory purposes and may be interchanged. The configurations relating to this disclosure have been described using a Cartesian coordinate system composed of the X, Y, and Z axes. The positional relationships of the configurations relating to this disclosure are not limited to being orthogonal. [Explanation of symbols]

[0057] 10 Isolators 21 First waveguide (211: first surface, 212: second surface, 213: side surface) 22 Second waveguide (221: first surface, 222: second surface, 223: side surface) 30 grooves 31 Non-reciprocal members 32 Absorbing material 40 masks 50 substrates (50A: substrate surface, 52: box layer) 54. First insulating layer 56 Second insulating layer 71, 72 Heater 81 First branching point 82 Second Branch LS laser irradiation range

Claims

1. A substrate having a substrate surface, A waveguide located on the substrate surface and having a first surface facing the substrate surface, a second surface located on the opposite side of the first surface, and a side surface connecting the first surface and the second surface, A groove having a bottom portion and a side portion in which at least a part of the side surface of the waveguide is exposed, A mask located on the second surface of the waveguide such that it overlaps with at least the region in contact with the groove when viewed from the direction normal to the substrate surface, A non-reciprocal member positioned in the groove so as to contact the side surface of the waveguide and Equipped with, The waveguide includes a first waveguide and a second waveguide that are arranged in a zigzag pattern within a substantially circular region when viewed from the direction normal to the substrate surface, and the isolator is configured such that the groove is not located between the first waveguide and the second waveguide.

2. The isolator according to claim 1, wherein a laser light absorbing member is further formed on the non-reciprocal member formed in the groove.

3. The isolator according to claim 1 or 2, wherein, in a plan view of the substrate, the mask is positioned so as not to overlap with a part of the waveguide.

4. The isolator according to claim 3, wherein the cross-sectional shape of the waveguide is rib-shaped.

5. The isolator according to any one of claims 1 to 4, wherein the non-reciprocal member includes YIG (yttrium iron garnet).

6. The isolator according to any one of claims 1 to 5, wherein the position of the bottom of the groove in the direction normal to the substrate surface is substantially the same as the position of the first surface of the waveguide.

7. The isolator according to any one of claims 1 to 5, wherein the position of the bottom of the groove in the direction normal to the substrate surface is lower than the position of the first surface of the waveguide.

8. The isolator according to any one of claims 1 to 7, wherein the waveguide has a filter section that transmits TE-mode electromagnetic waves and removes TM-mode electromagnetic waves.

9. The isolator according to any one of claims 1 to 8, wherein at least a portion of the groove has a first side portion in which at least a portion of the side surface of the first waveguide is exposed, and a second side portion in which at least a portion of the side surface of the second waveguide is exposed.

10. The isolator according to any one of claims 1 to 9, wherein the distance at which the first waveguide is in contact with the non-reciprocal member is equal to the distance at which the second waveguide is in contact with the non-reciprocal member.

11. The isolator according to any one of claims 1 to 10, further comprising a heater for controlling the temperature of the first waveguide and the second waveguide, respectively.

12. A waveguide is formed on a substrate having a substrate surface. An insulating layer and a mask are formed on the waveguide. The insulating layer is etched to form a groove, exposing the side surface of the waveguide. A non-reciprocal member is formed in the groove, A method for manufacturing an isolator, comprising irradiating the non-reciprocal member with laser light whose transmittance to the mask is less than the transmittance threshold of the mask.

Images