Thermo-optical phase shifter based on thermo-optical effect

Abstract

The invention relates to the technical field of thermo-optical phase shifters, in particular to a thermo-optical effect-based thermo-optical phase shifter, which comprises a base and a thermo-optical phase shifter, and is characterized in that the base comprises a substrate, a lower cladding and an upper cladding which are sequentially arranged from bottom to top; the thermo-optical phase shifter comprises an input waveguide, a central waveguide and an output waveguide which are arranged on the upper surface of the lower cladding at intervals and are connected in sequence; the first slab waveguide is arranged on the upper surface of the lower cladding and located between the input waveguide and the central waveguide, the middle area of the first slab waveguide is subjected to N-type doping or P-type doping to form a first heavily-doped area, and a first electrode and a first plated-through hole are arranged on the upper cladding and located above the first heavily-doped area; the second slab waveguide is arranged on the upper surface of the lower cladding and located between the central waveguide and the output waveguide, the middle area of the second slab waveguide is subjected to N-type doping or P-type doping to form a second heavily doped area, and a second electrode and a second plated-through hole are arranged on the upper cladding and located above the second heavily doped area. The phase shift efficiency can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of thermo-optical phase shifter technology, and more particularly to a thermo-optical phase shifter based on the thermo-optical effect. Background Technology

[0002] Thermo-optic phase shifters are core devices in photonic integrated circuits, achieving phase modulation of optical signals by altering the effective refractive index of a waveguide through the thermo-optic effect. Their working principle is based on localized heating of the waveguide region by a heater, which, in turn, causes a change in refractive index due to the material's thermo-optic coefficient, thereby modulating the phase of the optical signal. Due to their compact structure, good process compatibility, and ease of large-scale integration, thermo-optic phase shifters are widely used in fields such as optical switching, optical phased arrays, optical neural networks, and quantum optics.

[0003] However, traditional thermo-optical phase shifters often struggle to achieve an ideal balance between losses, phase shift efficiency, response speed, integration density, and fabrication complexity. In traditional thermo-optical phase shifters, insufficient optimization of the heater's thermal field distribution and waveguide structure leads to a significant portion of heat being dissipated into the cladding and substrate, resulting in low phase shift efficiency. Summary of the Invention

[0004] Therefore, in order to address the above problems, this invention proposes a high-efficiency thermo-optical phase shifter that can effectively improve phase shift efficiency while maintaining a compact device size and extremely low optical loss.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A thermo-optical phase shifter based on thermo-optical effect includes a base and a thermo-optical phase shifter disposed on the base, wherein the base includes a substrate, a lower cladding layer and an upper cladding layer disposed sequentially from bottom to top; The thermo-optical phase shifter includes: An input waveguide, a center waveguide, and an output waveguide are spaced apart and parallel to each other on the upper surface of the lower cladding. The input waveguide and the center waveguide, as well as the center waveguide and the output waveguide, are connected by a strip-shaped curved waveguide that turns 180°. A first planar waveguide is disposed on the upper surface of the lower cladding layer and located between the input waveguide and the center waveguide. The central region of the first planar waveguide is N-type doped or P-type doped to form a first heavily doped region. A first electrode and a first metallization hole are disposed on the upper cladding layer above the first heavily doped region. The first electrode is electrically connected to the first heavily doped region through the first metallization hole to form a first heater. A second planar waveguide is disposed on the upper surface of the lower cladding layer and located between the center waveguide and the output waveguide. The middle region of the second planar waveguide is N-type doped or P-type doped to form a second heavily doped region. A second electrode and a second metallization hole are disposed on the upper cladding layer above the second heavily doped region. The second electrode is electrically connected to the second heavily doped region through the second metallization hole to form a second heater.

[0006] Furthermore, a ridge transition structure is provided at the connection points of the input waveguide, the center waveguide, the output waveguide, and the strip-shaped curved waveguide.

[0007] Furthermore, through-holes are formed on the lower and upper cladding layers, and thermal insulation trenches are etched through the through-holes in a portion of the substrate located below the thermo-optical phase shifter to isolate the thermo-optical phase shifter from the substrate.

[0008] Furthermore, the widths of the input waveguide and the output waveguide are 350nm-550nm, and the width of the center waveguide is 400nm-700nm.

[0009] Furthermore, the thickness of the input waveguide, center waveguide, and output waveguide is 160nm-300nm.

[0010] Furthermore, the thickness of the first planar waveguide and the second planar waveguide is 60nm-150nm.

[0011] Furthermore, the thickness of the lower cladding layer is 2μm-3μm, and the thickness of the upper cladding layer is 1μm-7μm.

[0012] Furthermore, the thickness of the substrate is between 200 μm and 1000 μm.

[0013] By adopting the aforementioned technical solution, the beneficial effects of the present invention are: By distributing the input waveguide, the first heater, the center waveguide, the second heater, and the output waveguide at intervals, and by applying an electrical signal to the first and second heaters, heat is generated in the first and second heavily doped regions. Due to the thermo-optical effect of silicon material, the refractive index of light in the input waveguide, the center waveguide, and the output waveguide will change after being affected by the heat generated by the first and second heavily doped regions, and thus the optical phase will change, thereby achieving thermo-optical phase modulation. Attached Figure Description

[0014] Figure 1 A schematic top view of a thermo-optical phase shifter according to an embodiment of the present invention is shown.

[0015] Figure 2 A schematic cross-sectional view of a thermo-optical phase shifter according to an embodiment of the present invention is shown.

[0016] Figure 3 The diagram schematically illustrates a cross-sectional view of a thermo-optical phase shifter after a portion of the substrate has been etched away, according to an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures: 11. Input waveguide; 12. Center waveguide; 13. Output waveguide; 141. First planar waveguide; 142. Second planar waveguide; 151. First heavily doped region; 152. Second heavily doped region; 16. Ridge transition structure; 17. Strip-shaped curved waveguide; 21. Upper cladding; 22. Lower cladding; 3. Substrate; 41. First electrode; 42. First metallized via; 51. Second electrode; 52. Second metallized via; 5. Thermal insulation trench. Detailed Implementation

[0018] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0019] Example 1

[0020] refer to Figures 1-2 This embodiment provides a thermo-optical phase shifter based on the thermo-optical effect, including a base and a thermo-optical phase shifter disposed on the base. The base includes a substrate 3, a lower cladding layer 22, and an upper cladding layer 21 arranged sequentially from bottom to top. The substrate 3 is made of silicon, and the lower cladding layer 22 and the upper cladding layer 21 are made of silicon dioxide, forming an optical cladding structure through the lower cladding layer 22 and the upper cladding layer 21. The materials used for the substrate 3, the lower cladding layer 22, and the upper cladding layer 21 are all existing materials and will not be described in detail here. In this specific embodiment, the thickness of the substrate 3 is 200μm-1000μm, the thickness of the lower cladding layer 22 is 2μm-3μm, and the thickness of the upper cladding layer 21 is 1μm-7μm.

[0021] The thermo-optical phase shifter includes: An input waveguide 11, a center waveguide 12, and an output waveguide 13 are spaced apart and parallel to each other on the upper surface of the lower cladding 22. The input waveguide 11 and the center waveguide 12, as well as the center waveguide 12 and the output waveguide 13, are connected by a strip-shaped curved waveguide 17 with a 180° bend, in order to balance device size and low bending loss. There is no planar waveguide in the area where the strip-shaped curved waveguide 17 is located.

[0022] In this specific embodiment, preferably, the width of the input waveguide 11 and the output waveguide 13 is 350nm-550nm, the width of the center waveguide 12 is 400nm-700nm, and the thickness of the input waveguide 11, the center waveguide 12 and the output waveguide 13 is 160nm-300nm.

[0023] A first planar waveguide 141 is disposed on the upper surface of the lower cladding 22, between the input waveguide 11 and the center waveguide 12. The central region of the first planar waveguide 141 is N-type or P-type doped to form a first heavily doped region 151. The first heavily doped region 151 forms a good ohmic contact (ohmic contact refers to a non-rectified contact formed between a metal and a semiconductor, characterized by a contact resistance much smaller than the device's bulk resistance, without significantly changing the carrier concentration inside the semiconductor). A first electrode 41 and a first metallized via 42 are disposed on the upper cladding 21 above the first heavily doped region 151. The first electrode 41 is electrically connected to the first heavily doped region 151 through the first metallized via 42. The input waveguide 11, the center waveguide 12, and the first planar waveguide 141 constitute an optical waveguide for transmitting optical signals. The first electrode 41, the first metallized via 42, and the first heavily doped region 151 constitute a first heater. In use, an electrical signal is applied to the first electrode 41 of the first heater and transmitted to the first heavily doped region 151 through the first metallization hole 42 to generate heat. Due to the thermo-optical effect of silicon material, the light refractive index in the input waveguide 11 and the center waveguide 12 will change after being affected by the heat generated by the first heavily doped region 151, and thus the light phase will change, thereby realizing thermo-optical phase modulation.

[0024] Similarly, a second planar waveguide 142 is disposed on the upper surface of the lower cladding 22 and located between the central waveguide 12 and the output waveguide 13. The central region of the second planar waveguide 142 is N-type or P-type doped to form a second heavily doped region 152, which forms a good ohmic contact. A second electrode 51 and a second metallized via 52 are disposed on the upper cladding 21 above the second heavily doped region 152. The second electrode 51 is electrically connected to the second heavily doped region 152 through the second metallized via 52. The central waveguide 12, the output waveguide 13, and the second planar waveguide 142 constitute an optical waveguide for transmitting optical signals. The second electrode 51, the second metallized via 52, and the second heavily doped region 152 constitute a first heater. In use, an electrical signal is applied to the second electrode 51 of the second heater and transmitted to the second heavily doped region 152 through the second metallization hole 52 to generate heat. Due to the thermo-optic effect of silicon material, the refractive index of light in the center waveguide 12 and the output waveguide 13 will change after being affected by the heat generated by the second heavily doped region 152, and thus the light phase will change, thereby realizing thermo-optic phase modulation.

[0025] In this specific embodiment, preferably, the thickness of the first planar waveguide 141 and the second planar waveguide 142 is 60nm-150nm.

[0026] With the above structural setup, the input waveguide 11, the first heater, the center waveguide 12, and the second heater are configured. The 13-spacing distribution of the output waveguide effectively enhances the thermo-optical effect and improves the thermo-optical phase shift efficiency.

[0027] Further: A ridge conversion structure 16 is provided at the connection points of the input waveguide 11, the center waveguide 12, and the output waveguide 13 with the strip-shaped curved waveguide 17 to reduce conversion loss.

[0028] In this specific embodiment, preferably, the thickness of the substrate 3 is 200μm-1000μm, and the thickness of the lower cladding layer 22 and the upper cladding layer 21 is 3μm; the width of the input waveguide 11 and the output waveguide 13 is 400nm, and the width of the center waveguide 12 is 500nm; the thickness of the input waveguide 11, the center waveguide 12, and the output waveguide 13 is 220nm; and the thickness of the first planar waveguide 141 and the second planar waveguide 142 is 90nm. With the above parameter settings, the thermo-optical phase shifter can achieve a thermo-optical phase shift efficiency of 7mW / π, a response time of less than 20 microseconds, and an optical loss of less than 0.05 dB, exhibiting high thermo-optical phase shift efficiency and low optical loss.

[0029] Example 2

[0030] In the above embodiment one, some of the heat in the thermo-optical phase shifter will be dissipated into the substrate 3, affecting the thermo-optical effect.

[0031] like Figure 3 In this embodiment, based on the first embodiment described above, through-holes (not shown in the figure) are formed in the lower cladding layer 22 and the upper cladding layer 21. Etching solution is injected through these through-holes to etch a thermal insulation trench 5 in the portion of the substrate located below the thermo-optical phase shifter, thereby isolating the thermo-optical phase shifter from the substrate 3. The thermal insulation trench 5 can form effective thermal isolation below the thermo-optical phase shifter, thus further increasing the thermo-optical phase shifting efficiency.

[0032] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A thermo-optical phase shifter based on the thermo-optical effect, characterized in that: It includes a base and a phase shifter disposed on the base. The base includes a substrate (3), a lower cladding layer (22) and an upper cladding layer (21) disposed sequentially from bottom to top. The thermo-optical phase shifter includes: An input waveguide (11), a center waveguide (12), and an output waveguide (13) are spaced apart and parallel to each other on the upper surface of the lower cladding (22). The input waveguide (11) and the center waveguide (12) are connected to each other and the center waveguide (12) and the output waveguide (13) are connected by a strip-shaped curved waveguide (17) with a 180° bend. A first planar waveguide (141) is disposed on the upper surface of the lower cladding (22) and between the input waveguide (11) and the center waveguide (12). The middle region of the first planar waveguide (141) is N-type doped or P-type doped to form a first heavily doped region (151). A first electrode (41) and a first metallization hole (42) are disposed on the upper cladding (21) above the first heavily doped region (151). The first electrode (41) is electrically connected to the first heavily doped region (151) through the first metallization hole (42) to form a first heater. A second planar waveguide (142) is disposed on the upper surface of the lower cladding (22) and between the center waveguide (12) and the output waveguide (13). The middle region of the second planar waveguide (142) is N-type doped or P-type doped to form a second heavily doped region (152). A second electrode (51) and a second metallization hole (52) are disposed on the upper cladding (21) above the second heavily doped region (152). The second electrode (51) is electrically connected to the second heavily doped region (152) through the second metallization hole (52) to form a second heater.

2. The thermo-optical phase shifter based on the thermo-optical effect according to claim 1, characterized in that: A ridge transition structure (16) is provided at the connection points of the input waveguide (11), the center waveguide (12), the output waveguide (13), and the strip-shaped curved waveguide (17).

3. A thermo-optical phase shifter based on the thermo-optical effect according to claim 1, characterized in that: Through holes are provided on the lower cladding (22) and the upper cladding (21), and through the through holes, heat insulation trenches (5) are etched on the part of the substrate (3) located below the thermo-optical phase shifter to isolate the thermo-optical phase shifter from the substrate (3).

4. A thermo-optical phase shifter based on the thermo-optical effect according to claim 1, characterized in that: The widths of the input waveguide (11) and the output waveguide (13) are 350nm-550nm, and the width of the center waveguide (12) is 400nm-700nm.

5. A thermo-optical phase shifter based on the thermo-optical effect according to claim 1, characterized in that: The thickness of the input waveguide (11), center waveguide (12) and output waveguide (13) is 160nm-300nm.

6. A thermo-optical phase shifter based on the thermo-optical effect according to claim 1, characterized in that: The thickness of the first planar waveguide (141) and the second planar waveguide (142) is 60nm-150nm.

7. A thermo-optical phase shifter based on the thermo-optical effect according to claim 1, characterized in that: The thickness of the lower cladding layer (22) is 2μm-3μm, and the thickness of the upper cladding layer (21) is 1μm-7μm.

8. A thermo-optical phase shifter based on the thermo-optical effect according to claim 1, characterized in that: The thickness of the substrate (3) is between 200 μm and 1000 μm.

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