A thermo-optical phase shifter

Abstract

The present invention provides a thermo-optical phase shifter, which includes a cladding and an optical waveguide core; the cladding surrounds the optical waveguide core; the optical waveguide core includes a first section and a second section, and the radial dimensions of the first section and the second section are different. The thermo-optical phase shifter can improve the efficiency of the phase shifter and reduce optical crosstalk.

Description

Technical Field

[0001] The invention relates to the field of integrated optical components, and in particular to a thermo-optical phase shifter. Background Art

[0002] Thermo-optical phase shifters are an important component in photonic integrated circuits. Conventional thermo-optical phase shifters usually feature a conductive heater adjacent to or integrated with an optical waveguide. When current flows through the heater, the heater generates heat that can change the refractive index of the waveguide through the thermo-optic effect. In this way, the phase of the light wave propagating through the light guide is shifted.

[0003] Currently, in order to improve the efficiency of thermo-optical phase shifters, one method is to turn the waveguide into a loop shape so that the heat generated by one heater can be shared by multiple waveguides, thereby improving the efficiency of the thermo-optical phase shifter. However, in this structure, the waveguide is usually very long, and some parts of the waveguide, such as some parts in the loop waveguide, cannot be heated, so these parts of the waveguide do not promote phase shift while still occupying a large space. In addition, the geometry of the loop waveguide must be carefully optimized; otherwise, additional optical losses will be caused. However, in the ring waveguide, when the waveguide spacing is too small, although it can improve the efficiency of the thermo-optical phase shifter, it will cause optical crosstalk between the waveguides; when the waveguide spacing is too large, it makes the device less compact and reduces the heating efficiency.

[0004] Therefore, there is an urgent need to provide a thermo-optical phase shifter that can balance the heating efficiency and optical crosstalk of the thermo-optical phase shifter. Summary of the invention

[0005] An object of the present invention is to provide a thermo-optical phase shifter to improve the efficiency of the phase shifter and reduce optical crosstalk.

[0006] In a first aspect, the present invention provides a thermo-optical phase shifter, which comprises a cladding and an optical waveguide core. The cladding surrounds the optical waveguide core; the optical waveguide core comprises a first section and a second section, and the radial dimensions of the first section and the second section are different.

[0007] The beneficial effect of the thermo-optical phase shifter provided by the present invention is that based on the coupled mode theory, the evanescent coupling between the segments of different radial sizes in the optical waveguide core cannot achieve phase matching, so the optical crosstalk between the segments of different radial sizes at a certain spacing can be ignored. Compared with the thermo-optical phase shifter using the optical waveguide core of the same radial size, the thermo-optical phase shifter provided by the present invention has a more compact structure, thereby greatly improving the phase shifting efficiency. It can be seen that the thermo-optical phase shifter provided by the present invention can improve the efficiency of the phase shifter and reduce the optical crosstalk.

[0008] In a possible embodiment, the thermo-optical phase shifter further includes a resistive heater, which is surrounded by the cladding and located on one side of the optical waveguide core and separated from the optical waveguide core by the cladding. A certain distance is maintained between the resistive heater and the optical waveguide core, which can ensure that the optical waveguide core can be fully heated and improve the efficiency of the phase shifter. It should be noted that the distance between the resistive heater and the optical waveguide core cannot be too far, otherwise it will affect the heating efficiency. In this way, when current flows through the heater, heat energy is generated, and the waveguides of different radial sizes under the heater undergo changes in refractive index due to the thermo-optical effect, which ultimately causes the light waves to be phase shifted after propagating through the optical waveguide core.

[0009] In a possible embodiment, the optical waveguide core formed of some semiconductor materials can be made to have resistance properties through ion doping. In this way, the doped optical waveguide core itself has a heating function. When current flows through the optical waveguide core, heat energy is generated, and the refractive index of waveguides of different radial sizes changes due to the thermo-optical effect, which ultimately causes the light wave to be phase shifted after propagating through the optical waveguide core.

[0010] In a possible embodiment, the optical waveguide core is in a spiral or ring shape in space, which helps to save space on the optical integrated circuit components and the optical integrated circuit components have a higher degree of integration.

[0011] In a possible embodiment, the optical waveguide core further comprises a bridge structure, one end of the bridge structure is connected to the first section, and the other end of the bridge structure is connected to the second section. The bridge structure helps to connect different sections together. Optionally, the curved shape of the bridge structure comprises at least one of an arc shape, an Euler curved shape, and a sine shape.

[0012] In a possible embodiment, the curved portion of the segment of the optical waveguide core also includes at least one of an arc shape, an Euler curve shape, and a sinusoidal shape, so as to achieve a spiral distribution or a ring distribution in space.

[0013] In a possible embodiment, the radial dimension of the bridge structure gradually increases from small to large or from large to small from one end to the other end.

[0014] In a possible embodiment, the bridge structure includes a first bridge structure portion and a second bridge structure portion, the first bridge structure portion is a curved waveguide with uniform radial dimensions, and the second bridge structure portion is a straight waveguide with radial dimensions gradually changing from one end to the other.

[0015] In a possible embodiment, an air wall or air bottom groove for heat insulation is provided in the cladding, and the air wall or air bottom groove is located around the optical waveguide core. Through deep dry etching and wet etching processes, an air wall or air bottom groove, such as an air-filled closed cavity or air opening, can be created around the above-mentioned thermo-optical phase shifter. Such an air wall or air bottom groove reduces the heat conduction path, thereby locally capturing heat energy to improve heating efficiency.

[0016] In a possible embodiment, the material of the resistive heater includes but is not limited to titanium nitride, doped silicon, tungsten, gold or at least one of other types.

[0017] In a possible embodiment, the resistance material includes but is not limited to at least one of titanium nitride, doped silicon, tungsten, and gold.

[0018] In a possible embodiment, the material of the optical waveguide core includes but is not limited to at least one of silicon, silicon nitride, silicon dioxide, aluminum oxide, lithium niobate, polymer, germanium or III-V material or other types.

[0019] In a possible embodiment, the waveguide type of the optical waveguide core includes but is not limited to at least one of a channel waveguide, a ridge waveguide, a slot waveguide, a diffused waveguide or other types.

[0020] In a possible embodiment, the wavelength of the optical waveguide core includes but is not limited to at least one of the visible light range, O band, C band, mid-infrared or other ranges.

[0021] Other features will be described in the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A top view and a cross-sectional view of a thermo-optical phase shifter provided by the present invention without showing an external resistive heater;

[0023] Figure 2 Two different bridge structures are provided for the present invention;

[0024] Figure 3A A top view of another thermo-optical phase shifter provided by the present invention without showing an external resistive heater;

[0025] Figure 3B The present invention provides Figure 3A The cross section along line L in the figure;

[0026] Figure 4 A top view and a cross-sectional view of another thermo-optical phase shifter provided by the present invention without showing an external resistive heater;

[0027] Figure 5AA perspective view of another thermo-optical phase shifter with a resistive heater provided by the present invention;

[0028] Figure 5B The present invention provides Figure 5A A top view of the thermo-optical phase shifter in FIG.

[0029] Figure 5C The present invention provides Figure 5B The cross-section along line L in ;

[0030] Figure 5D The present invention provides Figure 5A Schematic diagram of a thermo-optical phase shifter having air walls or air bottom grooves;

[0031] Figure 6 Simulation results for the operating efficiency of three thermo-optical phase shifters on a silicon photonics platform.

[0032] Numbers in the figure:

[0033] 10. Thermo-optical phase shifter; 101. Cladding; 102. Optical waveguide core; 103. Resistive heater. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0035] In view of the problems existing in the prior art, the first embodiment of the present invention provides a thermo-optical phase shifter 10, such as Figure 1 As shown, it includes: a cladding 101 and an optical waveguide core 102 which has resistance properties by ion doping in advance.

[0036] The optical waveguide core 102 includes a first section 1021 and a second section 1022, and the radial dimensions of the first section 1021 and the second section 1022 are different. Figure 1In the embodiment, the radial dimension of the first segment 1021 is larger than the radial dimension of the second segment 1022. It should be noted that the radial dimension of the first segment 1021 may also be smaller than the radial dimension of the second segment 1022. Figure 1 It is only used for illustrative purposes and is not intended to be a specific limitation.

[0037] In another possible embodiment, the optical waveguide core 102 itself is made conductive by ion doping. In this way, the doped optical waveguide core 102 itself has a heating function. When current flows through the optical waveguide core, heat energy is generated. The refractive index of waveguides of different radial sizes changes due to the thermo-optical effect, which eventually causes the light waves propagating through the optical waveguide core to shift in phase. For example, Figure 1 It is shown that the optical waveguide core can be composed of a lightly doped silicon ridge waveguide.

[0038] in addition Figure 1 The cross-sectional view corresponding to the L line is also shown, from which it can be seen that the radial dimensions of adjacent optical waveguide cores on the cross section are different. Based on the coupled mode theory, the evanescent coupling between different waveguides cannot achieve phase matching, so the optical crosstalk between the segments of different radial dimensions of the optical waveguide core at a certain spacing can be ignored. Compared with the optical waveguide core of the same radial dimension, the thermal optical phase shifter has a more compact structure, which greatly improves the phase shifting efficiency and can also reduce optical crosstalk.

[0039] exist Figure 1 In the waveguide, parts of the signal (S) pad and the ground (G) pad are heavily doped to make ohmic contacts. Voltage can pass through the signal (S) and ground (G) regions, generating a current through the waveguide. Figure 1 The solid arrow between the signal (S) pad and the ground (G) pad in the figure shows the direction of current flow. Figure 1 The dotted arrow 01 in FIG. 1 represents the input direction of light and the dotted arrow 02 represents the output direction of light.

[0040] In one possible embodiment, in addition to Figure 1 The optical waveguide cores shown are spatially distributed in a spiral shape, and the optical waveguide cores can also be spatially distributed in a ring shape. The following text uses the optical waveguide cores distributed in a spiral shape as an example for explanation, and the following structural design is also applicable to the thermo-optical phase shifter with the optical waveguide cores distributed in a ring shape.

[0041] In other possible embodiments, in order to achieve a transitional connection between the first section 1021 and the second end 1022 of the optical waveguide core, the thermo-optical phase shifter 10 further includes a curved bridge structure 1023. One end of the bridge structure 1023 is connected to the first section 1021, and the other end of the bridge structure 1023 is connected to the second section 1022. Since the radial dimensions of the first section 1021 and the first section 1022 are different, the radial dimension of the bridge structure 1023 gradually increases from one end to the other end, such as Figure 2 As shown in (a) in FIG. 1 . Optionally, the curved shape of the bridge structure 1023 may include at least one of an arc shape, a line curved shape, an Euler curved shape, a sine shape or other types of shapes. In addition, optionally, the bridge structure 1023 includes a first bridge structure portion and a second bridge structure portion, the first bridge structure portion is a curved waveguide with a uniform radial dimension, and the second bridge structure portion is a straight waveguide with a radial dimension that gradually changes from small to large or from large to small from one end to the other end. For example, as Figure 2 As shown in (b), the curved bridge structure 1023 may include a regular curved (having a constant radial dimension) shape and a linear cone shape.

[0042] Although Figure 1 , an optical waveguide core having two different radial sizes is illustrated, but the optical waveguide core is not limited to only including two optical waveguide cores with different radial sizes. In a possible embodiment, the optical waveguide core 102 may include more than two segments with different radial sizes, that is, it may also include N third segments and M bridge structures, and the radial sizes of the N third segments may be completely or partially different, so that the radial sizes of two segments adjacent to each other in space of the thermo-optical phase shifter are different. For example, Figure 3A The optical waveguide core 102 in the thermo-optical phase shifter shown includes a first section 3021, a second section 3022, a third section 3023, and a bridge structure 3024. It should be noted that: Figure 3A The thermo-optical phase shifter in the embodiment further includes a signal (S) pad and a ground (G) pad (not shown in the figure). The radial dimensions of the first segment 3021, the second segment 3022 and the third segment 3023 are different. For example, Figure 3A In the embodiment, the radial dimension of the first segment 3021 is larger than the radial dimension of the second segment 3022, and the radial dimension of the third segment 3023 is larger than the radial dimension of the first segment 3021. In addition, the bridge structures 3024 are respectively of different curved shapes to achieve bending. Figure 3A The cross-sectional view corresponding to the dotted line L in Figure 3B As shown. Figure 3BIt can be seen that the radial dimensions of adjacent optical waveguide cores on the cross section are different. Based on the coupled mode theory, the optical waveguide core cannot achieve phase matching for the evanescent coupling between segments of different radial dimensions. Therefore, the optical crosstalk between optical waveguide cores of different radial dimensions at a certain spacing can be ignored. Compared with optical waveguide cores of the same radial dimension, the thermal optical phase shifter has a more compact structure, which greatly improves the phase shifting efficiency and reduces the optical crosstalk.

[0043] In another possible embodiment, an air wall for heat insulation is provided in the cladding 101, and the air wall is located around the optical waveguide core. The purpose of doing so is to further improve the phase shift efficiency. Figure 4 As shown, a thermo-optical phase shifter 10 with air walls or air bottom grooves is schematically shown, as well as a cross-sectional view of the thermo-optical phase shifter 10 along line L. Vertical grooves are made near different waveguides and substrates are cut under different waveguides. Air openings can be created around the thermo-optical phase shifter through deep dry etching and wet etching processes. This isolation reduces the heat conduction path, so that heat energy can be captured locally to improve heating efficiency.

[0044] In view of the problems existing in the prior art, an embodiment of the present invention further provides a thermo-optical phase shifter 10, such as FIG. 5A to FIG. 5C As shown, it includes: a cladding 101 , an optical waveguide core 102 and a resistive heater 103 .

[0045] That is, the optical waveguide core 102 may not be pre-doped with ions, that is, the thermo-optical phase shifter 10 is an ordinary thermo-optical phase shifter without electrical properties, but because the thermo-optical phase shifter 10 includes a resistive heater 103, the resistive heater 103 is surrounded by the cladding 101, and is located on one side of the optical waveguide core 102, and maintains a certain distance from the optical waveguide core 102 through the cladding 101, so as to fully heat the optical waveguide core 102. Optionally, the resistive heater 103 can be located on the upper layer of the optical waveguide core 102, or on the side of the optical waveguide core 102, or on the lower layer of the optical waveguide core 102, and the material of the resistive heater includes but is not limited to at least one of titanium nitride, doped silicon, tungsten, gold or other types.

[0046] For example, Figure 5A Schematically shows a three-dimensional structure of a thermo-optical phase shifter 10 including a resistive heater 103 and an optical waveguide core 102. Figure 5B Indicated Figure 4 A top view of Figure 5C for Figure 5B The cross-sectional view along the line L shows that the radial dimensions of adjacent optical waveguide cores in the cross section are different.

[0047] from Figure 5A and Figure 5B In the structure shown, a resistive heater 103 is placed on top of the spiral waveguide core. When a voltage is applied across the resistive heater 103, for example, through a signal (S) pad and a ground (G) pad, a current is generated. Figure 5B The solid arrow between the signal (S) pad and the ground (G) pad in the figure shows the direction of current flow. Figure 5B The dashed arrow 01 in the figure indicates the input direction of light and the dashed arrow 02 indicates the output direction of light. The current passing through the resistive heater 103 generates heat, so the refractive index of different sections of the optical waveguide core under the resistive heater 103 changes due to the thermo-optical effect, which eventually causes the light waves of the light wave propagation to shift in phase. Since the radial dimensions between different sections are different, based on the coupled mode theory, the evanescent coupling between different waveguides cannot achieve phase matching, so the optical crosstalk between sections of different radial dimensions at a certain spacing of the optical waveguide core can be ignored. Compared with the optical waveguide core of the same radial dimension, the optical crosstalk at a smaller spacing can be ignored. Compared with the waveguide of the same width, its structure is more compact, thereby greatly improving the phase shift efficiency.

[0048] In another possible embodiment, in a thermo-optical phase shifter with a resistive heater, an air wall or air bottom groove for heat insulation may be further provided in the cladding 101. Figure 5D As shown, a thermo-optical phase shifter 10 with air walls or air bottom grooves is illustrated, vertical grooves are made near different waveguides and substrates are cut under different waveguides, and air openings can be created around the above thermo-optical phase shifter through deep dry etching and wet etching processes. This isolation reduces the heat conduction path, so that thermal energy can be locally captured to improve heating efficiency.

[0049] It is worth noting that the number of wheels in the spiral cycle of the optical waveguide core in space can be adjusted according to demand. The number of wheels shown in the figure is only an example, and more wheels or fewer wheels can be used to make the total waveguide length larger or smaller. In this embodiment, the radius of curvature of the segment and the bridge structure needs to be selected according to actual needs to minimize the optical loss caused by bending. In addition, the shape of the bend can also be appropriately selected, including but not limited to at least one of an arc, a spline curve, an Euler bend, a sinusoidal shape or other types. In order to further reduce the loss, a multimode waveguide can be used for different sections of the waveguide. The material of the optical waveguide core includes but is not limited to at least one of silicon, silicon nitride, silicon dioxide, aluminum oxide, lithium niobate, polymer, germanium, III-V or other types. The waveguide type of the optical waveguide core includes but is not limited to at least one of a channel waveguide, a ridge waveguide, a slot waveguide, a diffusion waveguide or other types. The wavelength of the optical waveguide core includes but is not limited to at least one of the visible light range, the O band, the C band, the mid-infrared range or other ranges.

[0050] It is worth noting that the application fields of the above-mentioned thermo-optical phase shifter include but are not limited to optical sensing, optical computing, optical communication, optical storage, optical radar or other scenarios, and the present invention does not impose any restrictions on this.

[0051] To verify the negligible crosstalk in different optical waveguide cores, we performed simulations on a set of silicon waveguides with five different radial sizes. For example, in this simulation, five optical waveguide cores with different radial sizes are placed horizontally in parallel, and the radial sizes of adjacent segments will be different, such as 0.5um and 0.8um respectively, and the center spacing of adjacent waveguides is as small as 2um. Light is launched to one end of the optical waveguide core, and then the light passes completely through the waveguide to the right without passing through other waveguides. Therefore, the optical crosstalk between adjacent waveguides can be ignored. Although this simulation is performed on straight and different waveguides here, the same concept can also be applied to the thermo-optical phase shifter shown in this embodiment. For comparison of the experimental results, if the five waveguides have the same width, the light will pass through other waveguides, and there will be serious crosstalk problems, while the thermo-optical phase shifter in this embodiment has very little optical crosstalk.

[0052] To verify the improved efficiency of the phase shifter, Figure 6 The simulation results of the working efficiency of three types of thermo-optical phase shifters on the silicon photonics platform are shown as examples. The three curves represent three types of phase shifter structures, the traditional straight waveguide phase shifter, the spiral equal-size waveguide phase shifter and the phase shifter provided in this embodiment (the present invention). It can be seen that in order to achieve a certain phase shift, the spiral unequal-size waveguide phase shifter has the lowest power consumption.

[0053] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A thermo-optical phase shifter, characterized in that: including a cladding, an optical waveguide core, a signal electrode and a ground electrode; The cladding surrounds the optical waveguide core; The optical waveguide core comprises a first section and a second section, wherein the first section and the second section have different radial dimensions; The optical waveguide core is distributed in a spiral shape in space; The signal electrode is arranged around the optical waveguide core, and the ground electrode is located in an idle area in the center of the optical waveguide core. When a voltage is applied between the signal electrode and the ground electrode, a current is generated that flows from the outside of the optical waveguide core to the inside of the optical waveguide core, and the current generates heat for heating the optical waveguide core.

2. The thermo-optical phase shifter according to claim 1, characterized in that: The optical waveguide core has resistance performance through ion doping.

3. The thermo-optical phase shifter according to claim 1, characterized in that: The optical waveguide core further includes a bridge structure, one end of the bridge structure is connected to the first section, and the other end of the bridge structure is connected to the second section.

4. The thermo-optical phase shifter according to claim 3, characterized in that: The curved portion of the optical waveguide core and the bridge structure include at least one of an arc shape, a linear bend shape, an Euler bend shape, or a sinusoidal shape.

5. The thermo-optical phase shifter according to claim 3, characterized in that: The radial dimension of the bridge structure gradually increases from one end to the other end.

6. The thermo-optical phase shifter according to claim 3, characterized in that: The bridge structure includes a first bridge structure part and a second bridge structure part, the first bridge structure part is a curved waveguide with a uniform radial dimension, and the second bridge structure part is a straight waveguide with a radial dimension that gradually changes from one end to the other end.

7. The thermo-optical phase shifter according to any one of claims 1 to 2, characterized in that: An air wall or an air bottom groove for heat insulation is arranged in the cladding, and the air wall or the air bottom groove is located around the optical waveguide core.

8. The thermo-optical phase shifter according to any one of claims 1 to 2, characterized in that: The thermo-optical phase shifter further includes N third segments and M bridge structures. The N third segments have different radial sizes. The radial sizes of two spatially adjacent segments of the thermo-optical phase shifter are different.

9. The thermo-optical phase shifter according to any one of claims 1 to 2, characterized in that: The material of the optical waveguide core includes at least one of silicon, silicon nitride, silicon dioxide, aluminum oxide, lithium niobate, polymer, germanium or III-V material.

10. The thermo-optical phase shifter according to any one of claims 1 to 2, characterized in that: The waveguide type of the optical waveguide core includes at least one of a channel waveguide, a ridge waveguide, a slot waveguide or a diffused waveguide.

11. The thermo-optical phase shifter according to any one of claims 1 to 2, characterized in that: The wavelength of the optical waveguide core includes but is not limited to at least one of a visible light range, an O band, a C band, and a mid-infrared range.

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