Mach-zehnder electro-optic modulator and modulation method
By employing a silicon substrate and coplanar waveguide electrode structure in the Mach-Zehnder electro-optic modulator, combined with a ridge waveguide, efficient modulation and miniaturization are achieved, solving the problems of large size and high modulation voltage in existing technologies, and meeting the requirements of high density and large bandwidth.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-01-30
- Publication Date
- 2026-04-07
AI Technical Summary
Existing Mach-Zehnder electro-optic modulators suffer from problems such as large size, high modulation voltage, and increased power consumption in high-bandwidth and high-density applications, and their driving voltage is limited, making it difficult to meet the high integration requirements of data centers.
A silicon substrate structure is adopted, with first and second coplanar waveguide electrodes embedded, and voltage signals of the same frequency and phase are applied to the upper and lower sides of the waveguide layer. By adjusting the voltage and electrode length, a 0-degree or 180-degree phase difference of the optical signal is achieved. Combined with the ridge waveguide structure, the modulation efficiency is improved and the modulator size is reduced.
It achieves high modulation efficiency, reduces modulator size, meets the application requirements of high density and high bandwidth, reduces voltage-length product, and is suitable for highly integrated designs in data centers.
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Figure CN116224675B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of electro-optic modulator technology, and more specifically, relates to a Mach-Zehnder electro-optic modulator and modulation method. Background Technology
[0002] A Mach-Zehnder modulator (MZM), also known as an MZ modulator, is a device used to split input light into two equal signals, each entering a separate optical branch of the modulator. Both optical branches are made of electro-optical materials whose refractive index varies with the magnitude of the applied electrical signal. Because the change in refractive index of the optical branches causes a change in signal phase, when the two signals are combined again at the modulator output, the resulting optical signal is an interference signal with varying intensity. This effectively converts the change in electrical signal into a change in optical signal, thus achieving light intensity modulation. In short, a Mach-Zehnder modulator can achieve modulation of different bandwidths by controlling its bias voltage.
[0003] In existing technologies, with the increasing demands for data transmission, communication equipment is increasingly requiring higher bandwidth and smaller form factors. While traditional MZ modulators offer wide bandwidth, their large size and high modulation voltage make them unsuitable for high-density applications in data centers. Furthermore, as data transmission rates increase, the output voltage of the MZ modulator's driver becomes increasingly limited, leading to continuously increasing power consumption. The performance of an MZ modulator is evaluated using the voltage-length product, with the evaluation criterion being: the smaller the Vpi*L, the better the MZ modulator's performance.
[0004] like Figure 1 As shown, Figure 1 A longitudinal cross-sectional view of an existing MZ modulator is shown, in which the waveguide layer is made of lithium niobate, and both the upper and lower layers of the lithium niobate are made of SiO2. Since the refractive index of the SiO2 layer is lower than that of the lithium niobate, the light transmitted through the waveguide layer is confined within the waveguide layer and does not leak into the SiO2 layer and be lost, thus reducing the light loss during transmission through the waveguide layer.
[0005] Figure 2 The working principle diagram of an existing MZ modulator is shown, such as Figure 1 and Figure 2 As shown, a conventional MZ modulator uses a coplanar waveguide 04 as an electrode and Si as a substrate 01. A signal S is fed from the electrode and propagates on the electrode, which will form an electric field in the waveguide layer 02 and the SiO2 layer 03. The electric field of the waveguide layer will change its refractive index of light, and the direction of the refractive index change is related to the direction of the electric field: that is, on both sides of the two coplanar waveguides, the electric field has opposite effects on the refractive index of lithium niobate, with the refractive index increasing on one side and decreasing on the other side.
[0006] The principle can be derived based on the following calculation formula:
[0007]
[0008]
[0009] Where, n x' and n y' n is the refractive index of lithium niobate along its new axis after a transverse electric field is applied. o It is the ordinary refractive index, r 22 E is the electro-optic coefficient of lithium niobate. x It is the intensity of the applied electric field.
[0010] As can be seen from the two formulas above, the change in refractive index is linearly related to the electric field strength. Therefore, there are two ways to increase the electric field strength: one is to increase the electrode voltage, and the other is to reduce the distance between the electrodes. However, due to the high data transmission rate requirements of communication equipment, the output voltage of the device driver is limited; moreover, when the distance between the electrodes decreases to a certain extent, the electrodes will absorb the light field, which will increase light attenuation and thus be detrimental to the bandwidth and speed of communication transmission.
[0011] Furthermore, the MZ modulator utilizes the different propagation delays of light in different waveguides to achieve coherent destructive phase at the waveguide output, thereby modulating high-speed signals. The phase is the integral of the delay; that is, the longer the electrode, the larger the modulation phase, and the smaller the refractive index difference between the two waveguides. This requires longer electrodes, ultimately increasing the size of the MZ modulator and hindering highly integrated designs.
[0012] Secondly, the following calculation formula is used for derivation:
[0013]
[0014] Because lithium niobate has a high refractive index, typically 28, while SiO2 has a low refractive index, typically 4, and according to the electromagnetic field boundary conditions, the electric displacement at the junction of lithium niobate and SiO2 is continuous, the field strength of lithium niobate is only 15% of that of SiO2. The weaker field strength in lithium niobate reduces the modulation efficiency of the MZ modulator.
[0015] In summary, there is an urgent need to provide a Mach-Zehnder electro-optic modulator and modulation method that can achieve high modulation efficiency, reduce modulator size, and meet the requirements of high-density and high-bandwidth applications. Summary of the Invention
[0016] The purpose of this application is to provide a Mach-Zehnder electro-optic modulator and modulation method that can achieve high modulation efficiency, reduce modulator size, and meet the requirements of high-density and high-bandwidth applications.
[0017] To achieve the above objectives, the technical solution adopted in this application is as follows:
[0018] A Mach-Zehnder electro-optic modulator is provided, the modulator comprising a silicon substrate layer, a first silicon dioxide layer coated on the silicon substrate layer, a first coplanar waveguide electrode embedded in the first silicon dioxide layer, a waveguide layer coated on the first silicon dioxide layer, the first coplanar waveguide electrode and the waveguide layer being in contact connection; a second coplanar waveguide electrode is provided on the surface of the waveguide layer opposite to the first silicon dioxide layer, and a second silicon dioxide layer is coated in the gap formed by the waveguide layer and the second coplanar waveguide electrode.
[0019] The first coplanar waveguide electrode and the second coplanar waveguide electrode are used to apply voltage signals of the same frequency and phase.
[0020] In one embodiment, the thickness of the first coplanar waveguide electrode is less than the thickness of the first silicon dioxide layer;
[0021] Furthermore, the surface of the first coplanar waveguide electrode facing the waveguide layer and the surface of the first silicon dioxide layer facing the waveguide layer are flush.
[0022] In one embodiment, the second coplanar waveguide electrode includes a central band disposed at the center of the surface of the waveguide layer, and two ground bands symmetrically and spaced apart on both sides of the central band, namely a first ground band and a second ground band;
[0023] The second silicon dioxide layer is coated on the surface of the waveguide layer located between the center band and the first ground band, and on the surface of the waveguide layer located between the center band and the second ground band.
[0024] In one embodiment, the first coplanar waveguide electrode includes a central strip embedded in the middle of the first silicon dioxide layer, and two ground strips symmetrically and spaced apart on both sides of the central strip; the second coplanar waveguide electrode includes a central strip disposed at the center of the surface of the waveguide layer, and two ground strips symmetrically and spaced apart on both sides of the central strip.
[0025] Furthermore, the center bands of the first coplanar waveguide electrode and the second coplanar waveguide electrode are symmetrically arranged about the waveguide layer; the two ground bands of the first coplanar waveguide electrode and the two ground bands of the second coplanar waveguide electrode are respectively symmetrically arranged about the waveguide layer.
[0026] In one embodiment, the middle portion of the surface of the waveguide layer located between the center band and the first ground band protrudes in a direction away from the waveguide layer, and the middle portion of the second silicon dioxide layer located on the surface of the waveguide layer between the center band and the first ground band protrudes in a direction away from the waveguide layer.
[0027] In one embodiment, the middle portion of the surface of the waveguide layer located between the center band and the second ground band protrudes in a direction away from the waveguide layer, and the middle portion of the second silicon dioxide layer located on the surface of the waveguide layer between the center band and the second ground band protrudes in a direction away from the waveguide layer.
[0028] In one embodiment, the protrusion extends in a direction parallel to the direction of the gap between the center strip and the ground strip.
[0029] In one embodiment, the waveguide layer is a lithium niobate layer.
[0030] In one embodiment, the waveguide layer has a ridge waveguide structure.
[0031] The beneficial effects of the Mach-Zehnder electro-optic modulator provided in this application are as follows:
[0032] Compared with the prior art, the Mach-Zehnder electro-optic modulator provided in this application has a first silicon dioxide layer on a silicon substrate, a first coplanar waveguide electrode embedded in the first silicon dioxide layer, a waveguide layer on the first silicon dioxide layer, the first coplanar waveguide electrode and the waveguide layer being in contact and connected, and a second coplanar waveguide electrode on the surface of the waveguide layer opposite to the first silicon dioxide layer, the gap formed between the waveguide layer and the second coplanar waveguide electrode being coated with a second silicon dioxide layer, and the first coplanar waveguide electrode and the second coplanar waveguide electrode being used to apply voltage signals of the same frequency and phase.
[0033] When a voltage signal of the same frequency and phase is applied to the first and second coplanar waveguide electrodes, the voltage signal flows through the electrodes and generates an electric field on both sides of the electrodes. The change in the electric field causes a change in the refractive index of the waveguide layer, thereby changing the phase of the optical signal in the waveguide layer. By adjusting the voltage and the electrode length, the two optical signals can be made to have a 0-degree or 180-degree phase difference at the output end, thereby achieving coherent cancellation. This allows for the modulation of the modulator's optical carrier. This application achieves advantages that existing modulators do not possess, such as high modulation efficiency, reduced modulator size, and meeting the requirements of high-density and large-bandwidth applications, by using two coplanar waveguide electrodes respectively located on the upper and lower sides of the waveguide layer.
[0034] Another object of this application is to provide a modulation method adapted to the Mach-Zehnder electro-optic modulator as described above, the method comprising:
[0035] The driver and the modulator are electrically connected so that the dual differential output in-phase ports of the driver are electrically connected to the first coplanar waveguide electrode and the second coplanar waveguide electrode of the modulator, respectively; wherein, the driver has collectors T1, T2, T3 and T4, wherein T1 and T3 are transistor collectors, and T2 and T4 are dual differential output in-phase ports, for applying voltage signals of the same frequency and in phase to the modulator;
[0036] When the data input from the driver to the modulator requires a high level "1", the internal circuit of the driver controls the collectors of transistors T1 and T3 to be turned on, while the collectors of T2 and T4 are turned off. Then, the collector outputs of transistors T1 and T3 are low level "0", and the collector outputs of T2 and T4 are high level "1". At this time, T2 and T4, as dual differential output in-phase ports, apply a high level "1" of the same frequency and phase to the first coplanar waveguide electrode and the second coplanar waveguide electrode, respectively.
[0037] When the data input from the driver to the modulator must be a low level "0", the internal circuit of the driver controls the collectors of transistors T1 and T3 to be cut off and T2 and T4 to be turned on. Then, the collectors of transistors T1 and T3 output a high level "1" and the collectors of T2 and T4 output a low level "0". At this time, T2 and T4, as dual differential output in-phase ports, apply a low level "0" of the same frequency and phase to the first coplanar waveguide electrode and the second coplanar waveguide electrode, respectively.
[0038] The advantages of the modulation method of the Mach-Zehnder electro-optic modulator provided in this application compared with the prior art are the same as the advantages of the Mach-Zehnder electro-optic modulator provided in this application compared with the prior art, and will not be repeated here. Attached Figure Description
[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0040] Figure 1 A longitudinal cross-sectional view of an existing Mach-Zehnder modulator;
[0041] Figure 2 for Figure 1 The schematic diagram of the Mach-Zehnder modulator shown is shown below;
[0042] Figure 3 A longitudinal sectional view of a Mach-Zehnder modulator provided in an embodiment of this application;
[0043] Figure 4 for Figure 3 The schematic diagram of the Mach-Zehnder modulator shown is shown below;
[0044] Figure 5 A schematic diagram of the electrical connection between the driver and the Mach-Zehnder modulator provided in an embodiment of this application;
[0045] Figure 6 A comparison chart of Vpi values for existing Mach-Zehnder modulators and the Mach-Zehnder modulator provided in this application, respectively, using a single motor and a dual electrode.
[0046] Figure 7 A comparison chart of Vpi values between existing Mach-Zehnder modulators and the Mach-Zehnder modulator provided in this application, using electrodes of the same length.
[0047] Figure 8 A schematic diagram of the bandwidth of a Mach-Zehnder modulator provided in an embodiment of this application.
[0048] The following are the labeling elements in the figure:
[0049] 10. Silicon substrate layer; 20. First silicon dioxide layer; 30. Waveguide layer; 40. First coplanar waveguide electrode; 50. Second coplanar waveguide electrode; 60. Second silicon dioxide layer. Detailed Implementation
[0050] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.
[0051] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.
[0052] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.
[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0054] The Mach-Zehnder electro-optic modulator and modulation method provided in the embodiments of this application will now be described.
[0055] Please see Figures 3 to 5 As shown in the embodiment of this application, the Mach-Zehnder electro-optic modulator includes a silicon substrate 10, a first silicon dioxide layer 20 covered on the silicon substrate 10, a first coplanar waveguide electrode 40 embedded in the first silicon dioxide layer 20, a waveguide layer 30 covered on the first silicon dioxide layer 20, and the first coplanar waveguide electrode 40 and the waveguide layer 30 are in contact connection; a second coplanar waveguide electrode 50 is provided on the surface of the waveguide layer 30 away from the first silicon dioxide layer 20, and a second silicon dioxide layer 60 is coated in the gap formed by the waveguide layer 30 and the second coplanar waveguide electrode 50; wherein, the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50 are used to apply voltage signals of the same frequency and phase.
[0056] When a voltage signal of the same frequency and phase is applied to the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50, the voltage signal flows through the electrodes and generates an electric field on both sides of the electrodes. The change in the electric field causes a change in the refractive index of the waveguide layer 30, thereby changing the phase of the optical signal in the waveguide layer 30. By adjusting the voltage and the electrode length, the two optical signals can generate a 0-degree or 180-degree phase difference at the output end, thereby achieving coherent cancellation. This allows for the modulation of the modulator's optical carrier. This application achieves advantages that existing modulators do not possess, such as high modulation efficiency, reduced modulator size, and meeting the requirements of high-density and large-bandwidth applications, by using two coplanar waveguide electrodes respectively located on the upper and lower sides of the waveguide layer 30.
[0057] In one embodiment, the thickness of the first coplanar waveguide electrode 40 is less than the thickness of the first silicon dioxide layer 20; and the surface of the first coplanar waveguide electrode 40 facing the waveguide layer 30 and the surface of the first silicon dioxide layer 20 facing the waveguide layer 30 are flush to ensure the contact reliability between the first coplanar waveguide electrode 40 and the waveguide layer 30.
[0058] In one embodiment, the second coplanar waveguide electrode 50 includes a central band disposed at the center of the surface of the waveguide layer 30, and two ground bands symmetrically and spaced apart on both sides of the central band, namely a first ground band and a second ground band; wherein, a second silicon dioxide layer 60 is coated on the surface of the waveguide layer 30 located between the central band and the first ground band and on the surface of the waveguide layer 30 located between the central band and the second ground band.
[0059] In a preferred embodiment, the middle portion of the surface of the waveguide layer 30 located between the center band and the first ground band protrudes in a direction away from the waveguide layer 30, and the middle portion of the second silicon dioxide layer 60 located on the surface of the waveguide layer 30 located between the center band and the first ground band protrudes in a direction away from the waveguide layer 30.
[0060] The middle portion of the surface of the waveguide layer 30 located between the center band and the second ground band protrudes in a direction away from the waveguide layer 30, and the middle portion of the second silicon dioxide layer 60 located on the surface of the waveguide layer 30 located between the center band and the second ground band protrudes in a direction away from the waveguide layer 30.
[0061] Furthermore, in a preferred embodiment, the extension direction of the protrusion is parallel to the extension direction of the gap between the center strip and the ground strip.
[0062] In one embodiment, the first coplanar waveguide electrode 40 includes a central band embedded in the middle of the first silicon dioxide layer 20, and two ground bands symmetrically and spaced apart on both sides of the central band; the second coplanar waveguide electrode 50 includes a central band disposed at the center of the surface of the waveguide layer 30, and two ground bands symmetrically and spaced apart on both sides of the central band.
[0063] Furthermore, the center band of the first coplanar waveguide electrode 40 and the center band of the second coplanar waveguide electrode 50 are symmetrically arranged about the waveguide layer 30; the two grounding bands of the first coplanar waveguide electrode 40 and the two grounding bands of the second coplanar waveguide electrode 50 are respectively symmetrically arranged about the waveguide layer 30.
[0064] In a preferred embodiment, the waveguide layer 30 is a lithium niobate layer, and the structure of the waveguide layer 30 is a ridge waveguide.
[0065] In one embodiment, the lengths of the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50 are both 1 cm; the voltage-length product of the modulator, Vpi*L, is 1.5 V.cm; and the bandwidth of the modulator is 100 G.
[0066] Another objective of this application is to provide a modulation method adapted to the above-mentioned Mach-Zehnder electro-optic modulator, the method comprising:
[0067] The driver and modulator are electrically connected at their feed terminals so that the dual differential output in-phase ports of the driver are electrically connected to the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50 of the modulator, respectively; wherein the driver has collectors T1, T2, T3 and T4, wherein T1 and T3 are transistor collectors, and T2 and T4 are dual differential output in-phase ports for applying voltage signals of the same frequency and phase to the modulator;
[0068] When the data input from the driver to the modulator requires a high level "1", the internal circuit of the driver controls the collectors of transistors T1 and T3 to be turned on, while the collectors of T2 and T4 are turned off. At this time, the collector outputs of transistors T1 and T3 are low level "0", and the collector outputs of T2 and T4 are high level "1". T2 and T4, as dual differential output in-phase ports, apply the same frequency and in-phase high level "1" to the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50, respectively.
[0069] When the data input from the driver to the modulator must be a low level "0", the internal circuit of the driver controls the collectors of transistors T1 and T3 to be cut off and T2 and T4 to be turned on. Then the collectors of transistors T1 and T3 output a high level "1" and the collectors of T2 and T4 output a low level "0". At this time, T2 and T4, as dual differential output in-phase ports, apply a low level "0" of the same frequency and phase to the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50, respectively.
[0070] When a voltage signal of the same frequency and phase is applied to the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50, the voltage signal flows through the electrode and generates an electric field on both sides of the electrode. The change in the electric field will cause the refractive index of the waveguide layer 30 to change, thereby changing the phase of the optical signal in the waveguide layer 30. By adjusting the voltage and the electrode length, the two optical signals can generate a phase difference of 0 degrees or 180 degrees at the output end, so as to achieve coherent cancellation. In this way, the modulation of the modulator optical carrier can be realized.
[0071] Specifically, when a voltage signal of the same frequency and phase is applied to the first coplanar waveguide electrode 40 and the second coplanar waveguide electrode 50, an electric field is generated between the two electrodes located at different positions above and below and ground. The generated electric field passes through the waveguide layer 30, and the electric fields generated by the upper and lower electrodes are superimposed in the middle, which increases the electric field strength. This improves the modulation efficiency of the modulator, reduces the voltage length product of the modulator, and meets the requirements of high-density and large-bandwidth applications, which are advantages that existing modulators do not have.
[0072] like Figure 6 As shown, Figure 6 The figure shows a comparison of field strength and Vpi between two-electrode and single-electrode schemes. In the figure, the horizontal axis represents the electrode spacing in μm, and the vertical axis represents the electric field in V / m. Figure 6It can be seen that the electric field of the two electrodes tends to be twice that of the single electrode.
[0073] like Figure 7 As shown, Figure 7 The figure shows a comparison of modulation Vpi under the condition of electrodes of the same length, from Figure 7 As can be seen, under the same electrode length conditions, the Vpi of the dual electrode is about half that of the single electrode. Therefore, the dual electrode achieves improved modulation efficiency while miniaturizing the modulator, making it easier to integrate, and thus meeting the high-density application requirements of data centers.
[0074] like Figure 8 As shown, Figure 8 The image shows the photoelectric bandwidth of a modulator with dual electrodes according to an embodiment of this application. Figure 8 The data shows that when the electrode length is 1cm, the electro-optic modulation bandwidth can reach 100G and Vpi*L=1.5V.cm, while in the existing technology, the electro-optic modulation bandwidth is only 40G and Vpi*L=1.75V.cm.
[0075] comprehensive Figure 6 , Figure 7 and Figure 8 As can be seen, the modulator implementation scheme proposed in this application improves modulation efficiency while reducing the size of the modulator, which can meet the application requirements of high density and large bandwidth.
[0076] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A Mach-Zehnder electro-optic modulator, characterized in that: The modulator includes a silicon substrate (10), on which a first silicon dioxide layer (20) is disposed, a first coplanar waveguide electrode (40) is embedded, and a waveguide layer (30) is disposed on the first silicon dioxide layer (20). The first coplanar waveguide electrode (40) and the waveguide layer (30) are in contact connection. A second coplanar waveguide electrode (50) is disposed on the surface of the waveguide layer (30) away from the first silicon dioxide layer (20), and a second silicon dioxide layer (60) is coated in the gap formed between the waveguide layer (30) and the second coplanar waveguide electrode (50). The first coplanar waveguide electrode (40) and the second coplanar waveguide electrode (50) are provided for applying voltage signals of the same frequency and phase.
2. The Mach-Zehnder electro-optic modulator as described in claim 1, characterized in that: The thickness of the first coplanar waveguide electrode (40) is less than the thickness of the first silicon dioxide layer (20); Furthermore, the surface of the first coplanar waveguide electrode (40) facing the waveguide layer (30) and the surface of the first silicon dioxide layer (20) facing the waveguide layer (30) are flush.
3. The Mach-Zehnder electro-optic modulator as described in claim 1, characterized in that: The second coplanar waveguide electrode (50) includes a central band disposed at the center of the surface of the waveguide layer (30), and two ground bands symmetrically and spaced apart on both sides of the central band, namely the first ground band and the second ground band; The second silicon dioxide layer (60) is coated on the surface of the waveguide layer (30) located between the center band and the first ground band and on the surface of the waveguide layer (30) located between the center band and the second ground band.
4. The Mach-Zehnder electro-optic modulator as described in claim 1, characterized in that: The first coplanar waveguide electrode (40) includes a central strip embedded in the middle of the first silicon dioxide layer (20) and two ground strips symmetrically and spaced apart on both sides of the central strip; the second coplanar waveguide electrode (50) includes a central strip disposed at the center of the surface of the waveguide layer (30) and two ground strips symmetrically and spaced apart on both sides of the central strip. Furthermore, the center band of the first coplanar waveguide electrode (40) and the center band of the second coplanar waveguide electrode (50) are symmetrically arranged about the waveguide layer (30); the two ground bands of the first coplanar waveguide electrode (40) and the two ground bands of the second coplanar waveguide electrode (50) are respectively symmetrically arranged about the waveguide layer (30).
5. The Mach-Zehnder electro-optic modulator as described in claim 3, characterized in that: The middle portion of the surface of the waveguide layer (30) located between the center band and the first ground band protrudes in a direction away from the waveguide layer (30), and the middle portion of the second silicon dioxide layer (60) on the surface of the waveguide layer (30) located between the center band and the first ground band protrudes in a direction away from the waveguide layer (30).
6. The Mach-Zehnder electro-optic modulator as described in claim 5, characterized in that: The middle portion of the surface of the waveguide layer (30) located between the center band and the second ground band protrudes in a direction away from the waveguide layer (30), and the middle portion of the second silicon dioxide layer (60) on the surface of the waveguide layer (30) located between the center band and the second ground band protrudes in a direction away from the waveguide layer (30).
7. The Mach-Zehnder electro-optic modulator as described in claim 5 or 6, characterized in that: The protrusion extends in a direction parallel to the direction of the gap between the center strip and the ground strip.
8. The Mach-Zehnder electro-optic modulator as described in claim 1, characterized in that: The waveguide layer (30) is a lithium niobate layer.
9. The Mach-Zehnder electro-optic modulator as described in claim 8, characterized in that: The waveguide layer (30) has a ridge waveguide structure.
10. A modulation method adapted to the Mach-Zehnder electro-optic modulator as described in any one of claims 1-9, characterized in that, The method includes: The driver and the feed terminal of the modulator are electrically connected so that the dual differential output in-phase ports of the driver are electrically connected to the first coplanar waveguide electrode (40) and the second coplanar waveguide electrode (50) of the modulator, respectively; wherein the driver has collectors T1, T2, T3 and T4, wherein T1 and T3 are transistor collectors, and T2 and T4 are dual differential output in-phase ports for applying voltage signals of the same frequency and phase to the modulator; When the data input from the driver to the modulator must be a high level "1", the internal circuit of the driver controls the collectors of transistors T1 and T3 to be turned on, while the collectors of T2 and T4 are turned off. Then, the collectors of transistors T1 and T3 output a low level "0", and the collectors of T2 and T4 output a high level "1". At this time, T2 and T4, as dual differential output in-phase ports, apply a high level "1" of the same frequency and phase to the first coplanar waveguide electrode (40) and the second coplanar waveguide electrode (50) respectively. When the data input from the driver to the modulator must be low level "0", the internal circuit of the driver controls the collectors T1 and T3 of the transistors to be cut off and T2 and T4 to be turned on. Then the collectors of the transistors T1 and T3 output high level "1" and the collectors of T2 and T4 output low level "0". At this time, T2 and T4, as dual differential output in-phase ports, apply low level "0" of the same frequency and in phase to the first coplanar waveguide electrode (40) and the second coplanar waveguide electrode (50) respectively.
Citation Information
Patent Citations
Modulator and optical module
CN104749800A
Wafer structure for Mach-Zehnder optical modulator
CN106019643A