Thermo-optic phase modulation module and optical modulator

Abstract

Provided are thermo-optical phase modulation modules and optical modulators. The thermo-optical phase modulation module includes a substrate, an isolation layer disposed above the substrate, a first waveguide disposed above the isolation layer, and at least one heating element disposed above the isolation layer and not overlapping with the first waveguide in a direction perpendicular to the bottom surface of the substrate. The thermo-optical phase modulation module has a plurality of side thermal isolation grooves extending downward from the top surface and exposing the substrate, the plurality of side thermal isolation grooves being disposed around the first waveguide and the at least one heating element.

Description

[Technical Field]

[0001] TECHNICAL FIELD The present disclosure relates to the field of optical communications, and in particular to thermo-optic phase modulation modules and optical modulators. [Background technology]

[0002] Optical communication has rapidly developed into a major mode of information transmission due to its advantages such as wide frequency band and large capacity. To realize optical communication, optical modulation and demodulation must be performed.

[0003] A phase modulator is a device that modulates the phase of an output optical signal and may include one or more phase modulation modules. Based on different modulation mechanisms, the phase modulation modules may be, for example, electro-optic phase modulation modules based on the electro-optic effect or thermo-optic phase modulation modules based on the thermo-optic effect. While electro-optic phase modulation modules have a relatively fast modulation speed, their phase modulation range is small, which results in limited applications. Furthermore, heat generated due to large current injection reduces the electro-optic modulation efficiency. Materials with large thermo-optic coefficients and high thermal conductivity are well suited for thermo-optic phase modulation modules, which have the advantages of a relatively slow modulation speed, a large phase modulation range, and high modulation efficiency.

[0004] How to improve the modulation efficiency of the thermo-optic phase modulation module is currently an urgent technical problem that needs to be solved. Summary of the Invention

[0005] According to an aspect of the present disclosure, there is provided a thermo-optical phase modulation module including a substrate, a separation layer disposed on the substrate, a first waveguide disposed on the separation layer, and at least one heating element disposed on the separation layer and not overlapping with the first waveguide in a direction perpendicular to the lower surface of the substrate, the thermo-optical phase modulation module being provided with a plurality of side thermal isolation grooves extending downward from the upper surface and exposing the substrate, the plurality of side thermal isolation grooves being disposed around the first waveguide and the at least one heating element.

[0006] In some embodiments, the thermo-optic phase modulation module further includes a second waveguide interposed between the separation layer and the first waveguide and integrally connected to the first waveguide to form a ridge waveguide structure.

[0007] In some embodiments, the at least one heating element is formed on the upper surface of the isolation layer and does not overlap the second waveguide in a direction perpendicular to the lower surface of the substrate.

[0008] In some embodiments, at least one heating element is formed on an upper surface of the second waveguide.

[0009] In some embodiments, the thermo-optic phase modulation module comprises: a plurality of electrical wires connected to the at least one heating element disposed on the isolation layer and not overlapping with any of the first waveguide and the plurality of side thermal isolation grooves in a direction perpendicular to the lower surface of the substrate; Further includes:

[0010] In some embodiments, the thermo-optic phase modulation module includes a first end face and a second end face arranged opposite each other, and a third end face and a fourth end face arranged opposite each other, the first waveguide extending to the first end face and the second end face, and the plurality of electrical wires extending to the third end face and / or the fourth end face.

[0011] In some embodiments, the thermo-optic phase modulation module further includes a covering layer for covering the first waveguide and the at least one heating element.

[0012] In some embodiments, the side of the substrate facing the isolation layer is provided with a lower thermal isolation groove for connecting the lower portions of the plurality of side thermal isolation grooves with each other.

[0013] In some embodiments, the at least one heating element includes one heating element, an orthographic projection of the heating element onto the lower surface of the substrate is rectangular, an orthographic projection of each side thermal isolation groove onto the lower surface of the substrate is rectangular, and the plurality of side thermal isolation grooves include a first side thermal isolation groove, a second side thermal isolation groove, a third side thermal isolation groove, and a fourth side thermal isolation groove; a long side of an orthogonal projection of the heating element onto the lower surface of the substrate, a long side of an orthogonal projection of the first side thermal insulating groove onto the lower surface of the substrate, and a long side of an orthogonal projection of the second side thermal insulating groove onto the lower surface of the substrate are substantially parallel to the extension direction of the first waveguide; The long side of the orthogonal projection of the third lateral thermal insulation groove onto the lower surface of the substrate and the long side of the orthogonal projection of the fourth lateral thermal insulation groove onto the lower surface of the substrate are substantially perpendicular to the extension direction of the first waveguide.

[0014] In some embodiments, the at least one heating element comprises a plurality of heating elements, and the orthogonal projections of the plurality of heating elements onto the lower surface of the substrate are distributed on one or two sides of the orthogonal projection of the first waveguide onto the lower surface of the substrate.

[0015] In some embodiments, the heating element is any one of a metallic heating element, a ceramic heating element, a nanomaterial heating element, a microcrystalline heating element, and an infrared heating element.

[0016] According to an aspect of the present disclosure, provided is an optical modulator including a thermo-optic phase modulation module according to any one of the technical solutions described above.

[0017] It should be understood that the content described in this section is not intended to identify critical or important features of the embodiments of the present disclosure, and is not intended to limit the scope of the present disclosure. Other features of the present disclosure will be readily apparent from the description that follows.

[0018] More details, features and advantages of the present disclosure are disclosed in the following description of exemplary embodiments, which refer to the accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic perspective view of a thermo-optic phase modulation module according to some embodiments of the present disclosure. FIG. [Figure 2] 1 is a schematic top view of a thermo-optic phase modulation module according to some embodiments of the present disclosure. [Figure 3] FIG. 2 is a schematic cross-sectional view taken along the line AA in FIG. [Figure 4] FIG. 2 is a schematic cross-sectional view taken along the line BB in FIG. [Figure 5] 1 is a schematic perspective view of a thermo-optic phase modulation module according to some embodiments of the present disclosure. FIG. [Figure 6] 1 is a schematic top view of a thermo-optic phase modulation module according to some embodiments of the present disclosure. [Figure 7] 1 is a cross-sectional view of a thermo-optic phase modulation module according to some embodiments of the present disclosure taken along a plane parallel to a first end face. [Figure 8] 1 is a cross-sectional view of a thermo-optic phase modulation module according to some embodiments of the present disclosure taken along a plane parallel to a first end face. DETAILED DESCRIPTION OF THE INVENTION

[0020] Only a few exemplary embodiments are briefly described below. As will be recognized by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Accordingly, the accompanying drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive.

[0021] The inventors of the present disclosure recognize that the modulation efficiency of thermo-optical phase modulation modules in the related art is still not ideal due to large heat losses, and thus further improvement of the modulation efficiency of optical modulators is limited.

[0022] Based on this, embodiments of the present disclosure provide a thermo-optic phase modulation module and an optical modulator for improving the modulation efficiency of the thermo-optic phase modulation module, and thus improving the modulation efficiency of the optical modulator.

[0023] 1, 2, 3, and 4, a thermo-optical phase modulation module 100 according to some embodiments of the present disclosure includes a substrate 101, an isolation layer 102 disposed on the substrate 101, a first waveguide 104 disposed on the isolation layer 102, and at least one heating element 105 (shown in the illustrated embodiment as including one heating element 105) disposed on the isolation layer 102 and not overlapping with the first waveguide 104 in a direction perpendicular to the lower surface of the substrate 101. The thermo-optical phase modulation module 100 is provided with a plurality of side thermal isolation grooves 106 extending downward from the upper surface and exposing the substrate 101, the plurality of side thermal isolation grooves 106 being disposed around the first waveguide 104 and the at least one heating element 105.

[0024] 1, in this embodiment, the thermo-optic phase modulation module 100 further includes a second waveguide 103. The second waveguide 103 is disposed between the separation layer 102 and the first waveguide 104 and is integrally connected to the first waveguide 104 to form a ridge waveguide structure. The ridge waveguide has a series of excellent properties, such as a low fundamental mode cutoff frequency, a wide frequency band, and low impedance, and can have better performance when applied to the thermo-optic phase modulation module 100.

[0025] In an embodiment of the present disclosure, the side surface of the substrate 101 away from the separation layer 102 is defined as the lower surface of the substrate 101, the side surface of the substrate 101 close to the separation layer 102 is defined as the upper surface of the substrate 101, and the side surface of the thermo-optical phase modulation module 100 away from the lower surface of the substrate 101 is defined as the upper surface of the thermo-optical phase modulation module 100.

[0026] The basic working principle of the thermo-optical phase modulation module 100 is that the first waveguide 104 is heated by the heating element 105, the temperature of the first waveguide 104 and the surrounding area of ​​the first waveguide 104 will increase, and the refractive index of the material of the first waveguide 104 will change accordingly, so as to achieve the purpose of modulating the phase of the light field in the waveguide.

[0027] The thermo-optical phase modulation module 100 of the embodiment of the present disclosure is provided with a plurality of side thermal insulating grooves 106 around the first waveguide 104 and at least one heating element 105. The plurality of side thermal insulating grooves 106 can change the heat within the enclosed internal area so that the heat can be more concentrated and conducted to the first waveguide 104 and the vicinity of the first waveguide 104, rather than dissipating to the surrounding environment. Therefore, the heating efficiency of the first waveguide 104 can be improved, which in turn improves the modulation efficiency of the thermo-optical phase modulation module 100 based on the principle of the thermo-optical effect and the modulation efficiency of an optical modulator including the thermo-optical phase modulation module 100.

[0028] 3 and 4 , in some embodiments of the present disclosure, the side of the substrate 101 facing the separation layer 102 is provided with a lower thermal insulating groove 109 for connecting the lower portions of the multiple side thermal insulating grooves 106 to each other. Because the lower thermal insulating groove 109 is connected to the multiple side thermal insulating grooves 106, a three-dimensional compartment space is formed that can reduce heat dissipation from the side surface of the thermo-optical phase modulation module 100, as well as reduce heat dissipation from the lower portion of the thermo-optical phase modulation module 100, thereby further improving the heating efficiency of the first waveguide 104 and improving the modulation efficiency of the thermo-optical phase modulation module 100.

[0029] Embodiments of the present disclosure are not limited to the use of the ridge waveguide structure shown in Figure 1. As shown in Figure 5, the thermo-optic phase modulation module 100 may not include the second waveguide 103 in Figure 1, and may still be equipped with a heating element 105, etc., to realize a phase modulation function based on the principle of the thermo-optic effect.

[0030] As shown in FIG. 1 , the thermo-optic phase modulation module 100 includes a first end face 100a and a second end face 100b that are disposed opposite each other, and a third end face 100c and a fourth end face 100d that are disposed opposite each other. A first waveguide 104 extends to the first end face 100a and the second end face 100b. The first end face 100a may be used as the input end face of the thermo-optic phase modulation module 100, and the second end face 100b may be used as the output end face of the thermo-optic phase modulation module 100. Alternatively, the second end face 100b may be used as the input end face of the thermo-optic phase modulation module 100, and the first end face 100a may be used as the output end face of the thermo-optic phase modulation module 100. The specific shape of the first waveguide 104 is not defined and is not limited to the constant width strip waveguide shown in the figure. The first waveguide may also be designed into other shapes according to spot size modulation requirements. For example, at least a portion of the first waveguide has a shape with an increasing or decreasing width along the elongation direction of the first waveguide.

[0031] In an embodiment of the present disclosure, the number of heating elements 105 is not limited and may be one or more. As shown in FIG. 1, there is one heating element 105. As shown in FIG. 6, when there are multiple heating elements 105 (specifically, two in this embodiment), the multiple heating elements 105 are distributed on two sides of the first waveguide 104 when viewed from a top view. That is, the orthogonal projections of the multiple heating elements 105 onto the lower surface of the substrate 101 are distributed on two sides of the orthogonal projection of the first waveguide 104 onto the lower surface of the substrate 101. A plurality of side thermal insulation grooves 106 are arranged around the first waveguide 104 and the multiple heating elements 105.

[0032] The multiple heating elements 105 may be arranged on two sides or one side of the first waveguide 104 according to requirements, so as to heat the first waveguide 104 from both sides or one side of the first waveguide 104. The number and arrangement of the side thermal insulation grooves 106 are not limited. When multiple heating elements 105 exist, the multiple side thermal insulation grooves 106 are arranged around the first waveguide 104 and the multiple heating elements 105 to minimize heat dissipation.

[0033] In the present disclosure, the specific number, specific shape, and specific location of the heating element 105 and the side thermal insulation grooves are not particularly limited. As shown in Figure 2, in some embodiments of the present disclosure, there is one heating element 105, the orthographic projection of the heating element 105 onto the lower surface of the substrate 101 is rectangular, the orthographic projection of each side thermal insulation groove 106 onto the lower surface of the substrate 101 is also rectangular, and there are four side thermal insulation grooves 106, namely, a first side thermal insulation groove 106a, a second side thermal insulation groove 106b, a third side thermal insulation groove 106c, and a fourth side thermal insulation groove 106d. The long sides of the orthogonal projections of the heating element 105 onto the lower surface of the substrate 101, the long sides of the orthogonal projections of the first side thermal insulating groove 106a onto the lower surface of the substrate 101, and the long sides of the orthogonal projections of the second side thermal insulating groove 106b onto the lower surface of the substrate 101 are substantially parallel to the extension direction of the first waveguide 104, while the long sides of the orthogonal projections of the third side thermal insulating groove 106c onto the lower surface of the substrate 101 and the long sides of the orthogonal projections of the fourth side thermal insulating groove 106d onto the lower surface of the substrate 101 are substantially perpendicular to the extension direction of the first waveguide 104. Here, "substantially parallel" means that two things can be considered parallel to each other within a predetermined error range. Similarly, "substantially orthogonal" means that two things can be considered orthogonal to each other within a predetermined error range. This arrangement has a relatively compact structure and helps reduce the size of the thermo-optic phase modulation module 100 .

[0034] In the embodiments of the present disclosure, it is not limited that the downward extension direction of each side thermal isolation groove 106 must be perpendicular to the lower surface of the substrate 101. For example, each side thermal isolation groove 106 can be at a predetermined inclination angle relative to the lower surface of the substrate 101 and still effectively function to reduce heat dissipation. In some embodiments, each side thermal isolation groove 106 is formed using an etching process, and the wall surface of each side thermal isolation groove 106 exhibits a predetermined etching inclination angle relative to the lower surface of the substrate 101, so that the vertical cross section of each side thermal isolation groove 106 perpendicular to the length direction of the side thermal isolation groove 106 generally has an inverted trapezoidal shape.

[0035] In embodiments of the present disclosure, there is no limitation on the specific type of heating element 105. For example, the heating element may be a metallic heating element (such as a thin film resistor made from a nickel-chromium alloy), a ceramic heating element, a nanomaterial heating element, a microcrystalline heating element, an infrared heating element, or the like.

[0036] 1 and 2 , the thermo-optic phase modulation module 100 further includes a plurality of electrical wires 107 connected to at least one heating element 105 disposed on the isolation layer 102 and not overlapping any of the first waveguide 104 and the plurality of side thermal insulation grooves 106 in a direction perpendicular to the lower surface of the substrate 101. The electrical wires 107 may extend to the third end face and / or the fourth end face according to requirements, as long as they avoid the first waveguide 104 and each side thermal insulation groove 106. As shown in FIG. 1 , in this embodiment, there is one heating element 105 connected to two electrical wires 107, and the two electrical wires 107 extend to the third end face. When the heating element 105 is operating, the two electrical wires 107 are connected to the positive and negative terminals of a power supply, respectively. The electrical wires 107 may be made from metals with better conductivity, such as gold, copper, and aluminum.

[0037] 7, in some embodiments of the present disclosure, the heating element 105 is formed on the upper surface of the second waveguide 103. As shown in FIG. 8, in some other embodiments of the present disclosure, the heating element 105 may be formed on the upper surface of the isolation layer 102 and may not overlap with the second waveguide 103 in a direction perpendicular to the lower surface of the substrate 101. In these embodiments, the heating element 105 may indirectly transfer heat to the first waveguide 104.

[0038] 7 and 8, the thermo-optic phase modulation module 100 further includes a covering layer 108. The covering layer 108 covers the first waveguide 104 and at least one heating element 105. In addition, the covering layer 108 may also cover the electrical wire 107 or a portion of the electrical wire 107. In one embodiment, the covering layer 108 entirely covers the second waveguide 103, the first waveguide 104, the heating element 105, and the electrical wire 107. It can be seen that a plurality of side thermal insulating grooves 106 penetrate downwardly through the covering layer 108.

[0039] In some embodiments of the present disclosure, the first waveguide 104 and the second waveguide 103 are made of the same material and thus have the same refractive index, defined as n1, the refractive index of the cladding layer 108 is defined as n2, and the refractive index of the separation layer 102 is defined as n3. In some embodiments, the refractive indices of the above layers satisfy n1 > n2 and n1 > n3. The refractive indices of the separation layer 102 and the cladding layer 108 are less than the refractive indices of the first waveguide 104 and the second waveguide 103, so that light can be largely confined for transmission within the ridge waveguide, achieving the above-mentioned advantages of the ridge waveguide.

[0040] In the embodiment of the present disclosure, the material of each layer of the thermo-optical phase modulation module 100 is not specifically limited. For example, the main material of the substrate 101 may be silicon, the main material of the separation layer 102 may be silicon dioxide, the main material of the covering layer 108 may be silicon dioxide, and the main materials of the first waveguide 104 and the second waveguide 103 may be lithium niobate, silicon dioxide, a polymer, etc.

[0041] The embodiments of the present disclosure further provide an optical modulator including the thermo-optical phase modulation module 100 according to any one of the above-described embodiments. The specific product type of the optical modulator is not limited, and for example, the optical modulator may be an electro-optical modulator, an acousto-optical modulator, a magneto-optical modulator, an electro-absorption modulator, etc. The thermo-optical phase modulation module 100 of the embodiments of the present disclosure may be used as a bias modulation module in the optical modulator and may jointly achieve light modulation together with other phase modulation modules.

[0042] The thermo-optic phase modulation module 100 has high modulation efficiency based on the principle of the thermo-optic effect, and therefore the modulation efficiency of an optical modulator including the thermo-optic phase modulation module 100 is even higher.

[0043] As used herein, the term "substrate" may refer to the substrate of a cut wafer or to the substrate of an uncut wafer. It should be understood that the term "layer" includes a film and should not be construed as indicating vertical or horizontal thickness unless otherwise specified.

[0044] In this description, the orientations, positional relationships, or dimensions indicated by terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "lower," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are orientations, positional relationships, or dimensions shown with reference to the accompanying drawings, and it should be understood that these terms are used merely for ease of description, rather than to indicate or suggest that the referred-to devices or elements have a particular orientation and must be constructed and operated in a particular orientation, and therefore should not be construed as limiting the scope of protection of the present disclosure.

[0045] Additionally, the terms "first," "second," and "third" are for descriptive purposes only and should not be construed as indicating or suggesting the relative importance or implicitly indicating the number of technical features indicated. As such, features defined by "first," "second," and "third" may explicitly or implicitly include one or more features. In the description of this disclosure, the term "plurality" means two or more unless expressly and specifically defined otherwise.

[0046] In this disclosure, unless otherwise clearly stated or defined, terms such as "attach," "connect," "connected," and "secure" should be interpreted broadly, for example, they may refer to a fixed connection, a detachable connection, or an integral connection, a mechanical connection, or an electrical connection or communication, a direct connection, or an indirect connection by means of an intermediate medium, or an internal communication between two elements, or an interaction between two elements. A person of ordinary skill in the art may understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0047] In this disclosure, unless expressly stated or limited otherwise, a reference to a first feature being "above" or "below" a second feature may include cases where the first feature is in direct contact with the second feature, and may also include cases where the first and second features are not in direct contact but are contacted via another feature between them. Furthermore, a reference to a first feature being "above," "above," or "on" a second feature may include cases where the first feature is directly or diagonally above the second feature, or simply indicates that the first feature is at a higher elevation than the second feature. A reference to a first feature being "below," "below," or "below" a second feature may include cases where the first feature is directly or diagonally below the second feature, or simply indicates that the first feature is at a lower elevation than the second feature.

[0048] This description provides many different implementations or examples that can be used to realize the present disclosure. It should be understood that these different implementations or examples are purely illustrative and are in no way intended to limit the scope of protection of the present disclosure. Based on the disclosure of the description of the present disclosure, those skilled in the art will be able to think of various modifications or substitutions. All these modifications or substitutions shall fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the scope of protection of the claims.

Claims

1. A thermo-optic phase modulation module, comprising: A substrate; a separation layer overlying the substrate; a first waveguide disposed on the separation layer; at least one heating element disposed on the separation layer and not overlapping the first waveguide in a direction perpendicular to the lower surface of the substrate; the thermo-optic phase modulation module is provided with a plurality of side thermal isolation grooves extending downward from an upper surface thereof and exposing the substrate, the plurality of side thermal isolation grooves being disposed around the first waveguide and the at least one heating element; a side of the substrate facing the isolation layer is provided with a lower thermal isolation groove for connecting lower portions of the plurality of side thermal isolation grooves to each other; the at least one heating element includes one heating element, an orthographic projection of the heating element onto the lower surface of the substrate is rectangular, an orthographic projection of each side thermal isolation groove onto the lower surface of the substrate is rectangular, and the plurality of side thermal isolation grooves include a first side thermal isolation groove, a second side thermal isolation groove, a third side thermal isolation groove, and a fourth side thermal isolation groove; a long side of the orthogonal projection of the heating element onto the lower surface of the substrate, a long side of the orthogonal projection of the first side thermal insulation groove onto the lower surface of the substrate, and a long side of the orthogonal projection of the second side thermal insulation groove onto the lower surface of the substrate are substantially parallel to an elongation direction of the first waveguide; a long side of the orthogonal projection of the third lateral thermal isolation groove onto the lower surface of the substrate and a long side of the orthogonal projection of the fourth lateral thermal isolation groove onto the lower surface of the substrate are substantially perpendicular to the extension direction of the first waveguide; Thermo-optic phase modulation module.

2. a second waveguide interposed between the separation layer and the first waveguide and integrally connected to the first waveguide to form a ridge waveguide structure; The thermo-optic phase modulation module of claim 1 , further comprising:

3. the at least one heating element is formed on an upper surface of the isolation layer and does not overlap the second waveguide in the direction perpendicular to the lower surface of the substrate; The thermo-optic phase modulation module according to claim 2 .

4. the at least one heating element is formed on an upper surface of the second waveguide. The thermo-optic phase modulation module according to claim 2 .

5. a plurality of electrical wires connected to the at least one heating element that are disposed on the isolation layer and do not overlap any of the first waveguide and the plurality of side thermal isolation grooves in the direction perpendicular to the lower surface of the substrate; The thermo-optic phase modulation module of claim 1 , further comprising:

6. the thermo-optic phase modulation module includes a first end face and a second end face arranged opposite to each other, and a third end face and a fourth end face arranged opposite to each other, the first waveguide extending to the first end face and the second end face, and the plurality of electric wires extending to the third end face and / or the fourth end face; The thermo-optic phase modulation module according to claim 5 .

7. a covering layer for covering the first waveguide and the at least one heating element; The thermo-optic phase modulation module of claim 1 , further comprising:

8. the at least one heating element comprises a plurality of heating elements, and orthogonal projections of the plurality of heating elements onto the lower surface of the substrate are distributed on one or two sides of an orthogonal projection of the first waveguide onto the lower surface of the substrate; The thermo-optic phase modulation module according to claim 1 .

9. The thermo-optic phase modulation module of claim 8 , wherein the heating element is one of a metal heating element, a ceramic heating element, a nanomaterial heating element, a microcrystalline heating element, and an infrared heating element.

10. An optical modulator comprising a thermo-optic phase modulation module according to any one of claims 1 to 7.

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