Polymer-based cascaded Mach-Zehnder weak voltage sensor

Abstract

The invention discloses a polymer-based cascaded Mach-Zehnder weak voltage sensor, which comprises an upper cladding, a core layer and a lower cladding, and is characterized in that the core layer of the sensor comprises a first-stage Mach-Zehnder electro-optical modulator and a second-stage Mach-Zehnder electro-optical modulator which are connected with each other through a 180-degree bent optical waveguide; wherein the half-wave voltage of the first-stage Mach-Zehnder electro-optical modulator is higher than that of the second-stage Mach-Zehnder electro-optical modulator, and two electric signal paths are arranged in each of the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator; and the output light intensity of the second-stage Mach-Zehnder electro-optical modulator is used for representing a weak voltage signal. The sensor overcomes the defect that a traditional silicon-based material Mach-Zehnder electro-optical modulator is high in half-wave voltage. The electro-optical modulator adopting the two-stage Mach-Zehnder cascade structure has the characteristics of linear output and small size, and is a weak voltage sensing photonic device which is resistant to electromagnetic interference and high in sensitivity.

Description

Technical Field

[0001] The invention relates to the technical field of voltage sensors, in particular to a polymer-based cascade Mach-Zehnder weak voltage sensor. Background Art

[0002] With the development of photonic integration technology, photonic integration technology based on optical signals has gradually received more and more research and attention. As the core device for electro-optical modulation in photonic integrated chips, Mach-Zehnder electro-optic modulator plays a very important role in photonic integrated chips. At present, the research on Mach-Zehnder electro-optic modulator is mostly focused on improving its modulation rate and bandwidth. As an important parameter of Mach-Zehnder electro-optic modulator, half-wave voltage has an important influence on reducing the amplitude of demodulated signal, improving device performance and reducing system power consumption. Therefore, Mach-Zehnder electro-optic modulator with low half-wave voltage, low loss and compact structure has important research value for building photonic integrated sensing system. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a polymer-based cascade Mach-Zehnder weak voltage sensor, which overcomes the disadvantage of high half-wave voltage of the traditional silicon-based material Mach-Zehnder electro-optical modulator. The electro-optical modulator adopting a two-stage Mach-Zehnder cascade structure has the characteristics of linear output and small size, and is a weak voltage sensing photonic device that is resistant to electromagnetic interference, light weight, small size, and high sensitivity.

[0004] In order to solve the above problems, the present invention provides a polymer-based cascade Mach-Zehnder weak voltage sensor for weak electrical signal detection. The polymer-based cascade weak voltage sensor adopts a three-layer waveguide structure, including an upper cladding layer, a core layer and a lower cladding layer. The upper cladding layer and the lower cladding layer are made of PDMS, and the core layer is made of PMMA.

[0005] The core layer of the sensor includes a first-stage Mach-Zehnder electro-optical modulator and a second-stage Mach-Zehnder electro-optical modulator interconnected by a 180° bent optical waveguide; wherein the half-wave voltage of the first-stage Mach-Zehnder electro-optical modulator is higher than the half-wave voltage of the second-stage Mach-Zehnder electro-optical modulator, two electrical signal paths are arranged in the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator, and the first-stage Mach-Zehnder electro-optical modulator has no bias voltage, which is conducive to the second-stage Mach-Zehnder electro-optical modulator to use its lower half-wave voltage to perform more efficient optical signal modulation;

[0006] The first-stage Mach-Zehnder electro-optic modulator also includes a 1×2 multimode interference coupler and a first X-type coupler; two ports of the 1×2 multimode interference coupler are respectively connected to the signal input ends of two electrical signal paths in the first-stage Mach-Zehnder electro-optic modulator; the signal input end of the first X-type coupler is respectively connected to the two electrical signal paths, and the signal output end of the first X-type coupler is connected to the 180° bent optical waveguide;

[0007] The second-stage Mach-Zehnder electro-optical modulator also includes a second X-type coupler and an output waveguide; the signal input end of the second X-type coupler is connected to the 180° bent optical waveguide, and the signal output end of the second X-type coupler is respectively connected to the signal input ends of two electrical signal paths in the second-stage Mach-Zehnder electro-optical modulator; the two ports of the output waveguide are respectively connected to the signal output ends of the two electrical signal paths in the second-stage Mach-Zehnder electro-optical modulator;

[0008] The output light intensity of the second-stage Mach-Zehnder electro-optic modulator is used to characterize the weak voltage signal.

[0009] Preferably, the thickness of the upper cladding layer and the lower cladding layer is 10 μm, and the refractive index is 1.41; the thickness of the core layer is 1 μm, and the refractive index is 1.488.

[0010] Preferably, the electrical signal path includes a modulation arm, and a curved waveguide connected at both ends of the modulation arm.

[0011] Preferably, the four modulation arms in the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator are arranged in parallel in sequence, and both ends of the four modulation arms are aligned and have equal lengths.

[0012] Preferably, the first X-type coupler and the second X-type coupler are both composed of two bent waveguides in the coupling region and two parallel straight waveguides in the coupling region, wherein each bent waveguide in the coupling region is connected to one end of a straight waveguide in the coupling region, a coupling region is formed between the two straight waveguides in the coupling region, a coupling gap between the two straight waveguides in the coupling region is 1 μm, a length of the straight waveguide in the coupling region is 100 μm, and a coupling efficiency is not less than 90%.

[0013] Preferably, the modulation arms of the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator have a length of 7000 μm and a width of 2 μm.

[0014] Preferably, the polymer-based cascade weak voltage sensor includes three signal electrodes and two ground electrodes; wherein the ground electrodes are arranged between the two modulation arms in the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator, and the signal electrodes are arranged on the outside of the modulation arms, and the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator share one signal electrode during the cascade process.

[0015] The advantages of the present invention compared with the prior art are:

[0016] The polymer-based cascade Mach-Zehnder weak voltage sensor of the present invention is composed of two-stage Mach-Zehnder electro-optical modulators with different structures. Due to the secondary modulation, the half-wave voltage is effectively reduced, and the half-wave voltage can be reduced to 1V, which can realize high-sensitivity electrocardiogram detection based on optical sensing. At the same time, the polymer-based cascade weak voltage sensor of the present invention also has the advantages of light weight, small size, high output linearity, etc.

[0017] In the present invention, the external voltage and the output light intensity are in a linear relationship within the range of 0.2V-2.4V, and weak voltage signals can be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a side cross-sectional structural schematic diagram of the present invention;

[0020] Figure 2 Schematic diagram of the top view of the core layer pattern of the present invention;

[0021] Figure 3 It is a schematic diagram of electrode distribution of the present invention;

[0022] Figure 4 is a flow chart of the preparation process of the present invention (in the figure, ag sequentially demonstrates the preparation process of the present invention);

[0023] Figure 5 is a light field diagram of the cascade region of the present invention;

[0024] Figure 6 is a curve diagram showing the relationship between the output light intensity and the applied voltage in the present invention;

[0025] Figure 7 The figure is a comparison diagram of the input signal and output voltage signal effects under different weak signal detection of the present invention.

[0026] In the figure: 1-upper cladding; 2-core layer; 3-lower cladding; 21-180° bent optical waveguide; 22-first-stage Mach-Zehnder electro-optic modulator; 23-second-stage Mach-Zehnder electro-optic modulator; 24-1×2 multimode interference coupler; 25-bent waveguide; 26-modulation arm; 27-first X-type coupler; 28-second X-type coupler; 29-output waveguide. DETAILED DESCRIPTION

[0027] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0028] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0030] Combination Figure 1 to Figure 7 The present invention discloses a polymer-based cascaded Mach-Zehnder weak voltage sensor, comprising: a lower cladding layer 3, a core layer 2 and an upper cladding layer 1; the core layer comprises a first-stage Mach-Zehnder electro-optical modulator 22 and a second-stage Mach-Zehnder electro-optical modulator 23, the first-stage Mach-Zehnder electro-optical modulator comprises a 1×2 multimode interference coupler 24, a curved waveguide 25, a modulation arm 26 and a first X-type coupler 27, the second-stage Mach-Zehnder electro-optical modulator comprises a second X-type coupler 28, a modulation arm, a curved waveguide and an output end waveguide 29, and the two stages are interconnected through a 180° curved optical waveguide 21; the polymer-based cascaded weak voltage sensor comprises three signal electrodes and two ground electrodes, a weak voltage is input through the signal electrode, the electric field around the modulation arm changes, and the effective refractive index changes under the action of the external electric field, resulting in a change in the optical phase in the modulation arm. Subsequently, the output light of the first-stage Mach-Zehnder electro-optical modulator is used as the input light source of the second stage, and the weak voltage signal is detected by using the secondary electro-optical modulation of the second stage. The polymer-based cascade weak voltage sensor can measure voltages below 1V, and the applied voltage and output light intensity are linearly related in the range of 0.2V-2.4V.

[0031] Preferably, in a polymer-based cascade weak voltage sensor, an X-type coupler is composed of two curved waveguides and two parallel straight waveguides in the coupling region. Each curved waveguide in the X-type coupler is connected to one end of a straight waveguide in the coupling region. The coupling region is between the two straight waveguides in the coupling region. The coupling gap between the two straight waveguides in the coupling region is 1 μm, the length of the straight waveguide in the coupling region is 100 μm, and the coupling efficiency is not less than 90%.

[0032] Preferably, in a polymer-based cascade weak voltage sensor, an output port of a first X-type coupler of a first-stage Mach-Zehnder electro-optic modulator and an input port of a second X-type coupler of an adjacent second-stage Mach-Zehnder electro-optic modulator are connected together through a 180° bent optical waveguide, the second X-type coupler is the input end of the second-stage Mach-Zehnder electro-optic modulator, four modulation arms are arranged side by side in parallel, both ends of the four modulation arms are aligned, and the modulation arms are 7000 μm long and 2 μm wide.

[0033] Preferably, in a polymer-based cascade weak voltage sensor, a ground electrode is arranged between the two modulation arms of the first-stage and second-stage Mach-Zehnder electro-optical modulators, a signal electrode is arranged on the outside of the two modulation arms, and the two modulators share a signal electrode during the cascade process; the first-stage Mach-Zehnder electro-optical modulator has no bias voltage, the half-wave voltage of the second-stage Mach-Zehnder electro-optical modulator is lower than the half-wave voltage of the first-stage Mach-Zehnder electro-optical modulator, and after modulation by the second-stage Mach-Zehnder electro-optical modulator, the half-wave voltage is 1V.

[0034] In order to more clearly illustrate the specific implementation mode of the present invention, an embodiment is provided below:

[0035] like Figure 1 As shown, the polymer-based cascade weak voltage sensor adopts a three-layer waveguide structure, including an upper cladding layer 1, a core layer 2, and a lower cladding layer 3. The upper cladding layer 1 and the lower cladding layer 3 are formed by spin coating of PDMS, with a thickness of 10 μm and a refractive index of 1.41; the core layer 2 is formed by spin coating of PMMA, with a thickness of 1 μm and a refractive index of 1.488.

[0036] like Figure 2 As shown, the core layer of the sensor includes a first-stage Mach-Zehnder electro-optic modulator 22 and a second-stage Mach-Zehnder electro-optic modulator 23; the first-stage Mach-Zehnder electro-optic modulator 22 and the second-stage Mach-Zehnder electro-optic modulator 23 are connected to each other through a 180° bent optical waveguide 21. The half-wave voltage of the second-stage Mach-Zehnder electro-optic modulator 23 is lower than the half-wave voltage of the first-stage Mach-Zehnder electro-optic modulator 22, and the first-stage Mach-Zehnder electro-optic modulator 22 has no bias voltage, which provides a relatively "pure" input state for the second-stage Mach-Zehnder electro-optic modulator 23, which is conducive to the second-stage Mach-Zehnder electro-optic modulator 23 to use its lower half-wave voltage to perform more efficient optical signal modulation.

[0037] The first-stage Mach-Zehnder electro-optic modulator is composed of a 1×2 multimode interference coupler 24, a curved waveguide 25, a modulation arm 26 and a first X-type coupler 27; two ports of the 1×2 multimode interference coupler 24 are respectively connected to one end of a modulation arm 26 through a curved waveguide 25, and the other ends of the two modulation arms 26 are respectively connected to two ports on the side where the curved waveguide of the first X-type coupler 27 is located; the first X-type coupler 27 is the output end of the first-stage Mach-Zehnder electro-optic modulator;

[0038] The structure of the second-stage Mach-Zehnder electro-optic modulator is similar to that of the first-stage Mach-Zehnder electro-optic modulator, except that an X-type coupler is used at the input end, which is composed of a second X-type coupler 28, a modulation arm, a curved waveguide 25 and an output end waveguide; two ports on the side where the curved waveguide of the second X-type coupler 28 is located are respectively connected to one end of a modulation arm 26, and the other ends of the two modulation arms 26 are also respectively connected to two ports of the output end waveguide 29 through a curved waveguide; an output port of the first X-type coupler of the first-stage Mach-Zehnder electro-optic modulator and an input port of the second X-type coupler 28 of the adjacent second-stage Mach-Zehnder electro-optic modulator are connected together through a 180° curved optical waveguide 21, and the output light intensity of the second-stage Mach-Zehnder electro-optic modulator represents a weak voltage signal. The second X-type coupler 28 is the input end of the second-stage Mach-Zehnder electro-optic modulator, and the four modulation arms are arranged in parallel in sequence, and the two ends of the four modulation arms are aligned and have equal lengths.

[0039] The X-type coupler in the present invention is composed of two curved waveguides and two parallel straight waveguides in the coupling region, each curved waveguide is connected to one end of a straight waveguide in the coupling region, the two curved waveguides are symmetrically arranged along the horizontal axis, the coupling region is between the two straight waveguides in the coupling region, and the coupling efficiency between the two straight waveguides in the coupling region is sufficiently large by setting a coupling gap. In this embodiment, the coupling gap between the two straight waveguides in the coupling region is 1 μm, the length of the straight waveguide in the coupling region is 100 μm, and the final coupling efficiency is not less than 90%.

[0040] The length of the modulation arms of the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator are both 7000 μm and 2 μm in width.

[0041] The straight waveguide length L_X of the coupling region of the X-type coupler is 100μm, the coupling gap W_X is 1μm, and the waveguide width of the X-type coupler is 2μm.

[0042] In this embodiment, the arm length L of the modulation arm is 7000 μm, the width is 2 μm, the waveguide length L_X of the coupling region of the X-type coupler is 100 μm, the coupling gap is 1 μm, and the parameters are shown in Table 1.

[0043] Table 1 Parameters of polymer-based cascade weak voltage sensor

[0044]

[0045] like Figure 3 As shown, the present invention includes five electrodes, which are signal electrode, ground electrode and signal electrode, ground electrode and signal electrode in sequence. Ground electrode is set between two modulation arms of the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator, signal electrode is set outside the two modulation arms, and the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator share one signal electrode in the cascade process.

[0046] When a weak voltage is input by the signal electrode, the electric field around the modulation arm will change. When affected by the external electric field, the effective refractive index of the modulation arm will change, thereby causing the light phase in the modulation arm to change. The output light modulated by the first-stage Mach-Zehnder electro-optic modulator is used as the input light source of the second-stage Mach-Zehnder electro-optic modulator, and secondary electro-optic modulation is performed in the second-stage Mach-Zehnder electro-optic modulator to detect weak voltage signals.

[0047] like Figure 4 As shown, the present invention includes a PDMS cladding layer and a PMMA core layer using a spin coating process to form a thin film, wherein the PDMS cladding layer spin coating parameters are: low speed 500r / min, duration 5s, high speed 4700r / min, duration 100s, and then placed on a heating table for curing, the curing parameters are low temperature 80°C, duration 5min, high temperature 110°C, duration 25min; PMMA core layer spin coating parameters are: low speed 500r / min, duration 5s, high speed 3000r / min, duration 60s, and then, thermal curing is performed on the heating table, the curing parameters are 65°C, duration 10min. The specific process is:

[0048] Clean the ITO substrate (see Figure 4 PDMS is spin-coated on the substrate. After the PDMS cladding film is successfully spin-coated, it is cured to form a PDMS lower cladding (see Figure 4 (b) in the figure); the cured PDMS lower cladding is cleaned by oxygen plasma, the oxygen plasma cleaning time is 5 minutes, the power is 400W, the cleaned PDMS cladding film is immersed in a silanization agent, and finally the PDMS lower cladding film is taken out and dried to complete the surface modification of the PDMS cladding film, and the cleaned and modified PDMS is obtained (see Figure 4 (c) in the figure); and then spin-coating the polymer core material on top (see Figure 4 (d) in the figure), the polymer core layer material is PMMA; then the core layer pattern is formed by etching on PMMA using a dry etching process (see Figure 4(e) in the figure), the etching parameters of the core layer are: RF power 200W, gas flow rate ratio SF4: O2=10: 50sccm, rate about 140nm / min; then the core layer pattern is cleaned by oxygen plasma (see Figure 4 After the PDMS cladding film is successfully spun, it is cured to form a PDMS upper cladding layer (see Figure (f) in the figure). Figure 4 (g) in the figure).

[0049] like Figure 5 As shown in the figure, the polymer-based cascaded weak voltage sensor is formed by connecting the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator with a 180° curved waveguide. The output end of the first-stage Mach-Zehnder electro-optic modulator and the input end of the second-stage Mach-Zehnder electro-optic modulator are connected by an X-type coupler. The two coupling region straight waveguides of the X-type coupler constitute the coupling region. It can be seen from the light field diagram that the coupling gap is 1μm. At this time, the coupling efficiency is not less than 90%, and the light does not scatter at the cascade during the two-stage cascade, which ensures the effective transmission of light. The coupling efficiency between the two coupling region straight waveguides of the two X-type couplers is large enough to achieve almost lossless cascade.

[0050] like Figure 6 As shown, the polymer-based cascade weak voltage sensor is a voltage sensing photonic device, the output light intensity and the applied voltage are sinusoidal, the difference between the highest and lowest voltages is 1.0V, and the half-wave voltage is 1.0V. The change in the output light intensity can be used to linearly characterize the change in the voltage applied to the voltage sensing photonic device. The applied voltage and the output light intensity are linearly related within a certain range, and a linear relationship between the voltage and the output light intensity is obtained. The certain range is that the applied voltage ranges from 0.2V to 2.4V. Within this range, the output light intensity presents a sinusoidal curve. In the case of a two-stage cascade, it can always output at a lower half-wave voltage. During the cascade process, the light is not scattered, and stable light transmission is achieved.

[0051] like Figure 7 As shown, (a) is a polymer-based cascade weak voltage sensor that inputs a 500mV sinusoidal input signal to both the first and second stages through a signal electrode. The left side of (a) is a waveform diagram of the sinusoidal input signal, and the right side is a waveform diagram of the corresponding output voltage signal. The output light intensity is obtained through a voltage sensing photonic device, and the detection voltage at different times is obtained according to the relationship between the output light intensity and the voltage, and then the output voltage signal diagram is obtained. The input signal frequency is set to 10Hz, and the output voltage waveform is observed. The output voltage waveform is also a periodic sinusoidal wave, with less noise and is smoother and without distortion. The results show that under a weak voltage input signal of 500mV, the output voltage corresponding to the input signal can be obtained, and the output voltage has the same waveform type as the input signal. Figure 7Figure (b) shows the waveform of a 250mV sinusoidal input signal and the corresponding output voltage signal of a polymer-based cascade weak voltage sensor input through a signal electrode. The input signal frequency is set to 10Hz, and the output voltage waveform is observed. The output voltage waveform is also a periodic sinusoidal wave with low noise and is smooth and distortion-free. The results show that under a weak voltage input signal of 500mV, the output voltage corresponding to the input signal can be obtained. The weak voltage sensor can restore the input weak sinusoidal signal and realize the detection of weak voltage. Figure 7 Figure (c) shows the waveform of the polymer-based cascade weak voltage sensor inputting a 100mV sine wave input signal through the signal electrode and the waveform of the corresponding output voltage signal. The input signal frequency is set to 10Hz, and the output voltage waveform is observed. The output voltage waveform is also a periodic wave, but there are noise and distortion phenomena, so it can still reflect the periodic law. The weak voltage sensor can also obtain the output voltage corresponding to the input signal, but the effect is relatively poor. Therefore, the polymer-based cascade weak voltage sensor of this embodiment can measure voltages below 1V, preferably 100mV-1.5V, and more preferably 250-500mV.

[0052] Finally, all the parts not fully described in the present invention adopt mature products and mature technical means in the prior art.

[0053] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A polymer-based cascade Mach-Zehnder weak voltage sensor for weak electrical signal detection, the polymer-based cascade weak voltage sensor adopts a three-layer waveguide structure, including an upper cladding layer, a core layer and a lower cladding layer, wherein the upper cladding layer and the lower cladding layer are made of PDMS, and the core layer is made of PMMA; characterized in that: The core layer of the sensor includes a first-stage Mach-Zehnder electro-optical modulator and a second-stage Mach-Zehnder electro-optical modulator interconnected by a 180° bent optical waveguide; wherein the half-wave voltage of the first-stage Mach-Zehnder electro-optical modulator is higher than the half-wave voltage of the second-stage Mach-Zehnder electro-optical modulator, and two electrical signal paths are provided in the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator; The first-stage Mach-Zehnder electro-optic modulator further includes a 1×2 multimode interference coupler and a first X-type coupler; two ports of the 1×2 multimode interference coupler are respectively connected to the signal input ends of two electrical signal paths in the first-stage Mach-Zehnder electro-optic modulator; the signal input end of the first X-type coupler is respectively connected to the two electrical signal paths, and the signal output end of the first X-type coupler is connected to the 180° bent optical waveguide; The second-stage Mach-Zehnder electro-optical modulator further includes a second X-type coupler and an output waveguide; the signal input end of the second X-type coupler is connected to the 180° bent optical waveguide, and the signal output end of the second X-type coupler is respectively connected to the signal input ends of two electrical signal paths in the second-stage Mach-Zehnder electro-optical modulator; the two ports of the output waveguide are respectively connected to the signal output ends of the two electrical signal paths in the second-stage Mach-Zehnder electro-optical modulator; The output light intensity of the second-stage Mach-Zehnder electro-optic modulator is used to characterize the weak voltage signal.

2. The polymer-based cascade Mach-Zehnder weak voltage sensor according to claim 1, characterized in that: The electrical signal path includes a modulation arm and a curved waveguide connected at two ends of the modulation arm.

3. The polymer-based cascade Mach-Zehnder weak voltage sensor according to claim 2, characterized in that: The four modulation arms in the first-stage Mach-Zehnder electro-optical modulator and the second-stage Mach-Zehnder electro-optical modulator are arranged in parallel in sequence, and both ends of the four modulation arms are aligned and have equal lengths.

4. The polymer-based cascade Mach-Zehnder weak voltage sensor according to claim 1, characterized in that: The thickness of the upper cladding layer and the lower cladding layer is 10 μm, and the refractive index is 1.41; the thickness of the core layer is 1 μm, and the refractive index is 1.

488.

5. The polymer-based cascade Mach-Zehnder weak voltage sensor according to claim 1, characterized in that: The first X-type coupler and the second X-type coupler are both composed of two bent waveguides in the coupling area and two parallel straight waveguides in the coupling area, wherein each bent waveguide in the coupling area is connected to one end of a straight waveguide in the coupling area, the two straight waveguides in the coupling area are between the coupling area, the coupling gap between the two straight waveguides in the coupling area is 1 μm, the length of the straight waveguide in the coupling area is 100 μm, and the coupling efficiency is not less than 90%.

6. The polymer-based cascade Mach-Zehnder weak voltage sensor according to claim 1, characterized in that: The modulation arms of the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator have a length of 7000 μm and a width of 2 μm.

7. The polymer-based cascade Mach-Zehnder weak voltage sensor according to claim 1, characterized in that: The polymer-based cascade weak voltage sensor comprises three signal electrodes and two ground electrodes; A ground electrode is arranged between two modulation arms in the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator, and a signal electrode is arranged outside the modulation arm. The first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator share a signal electrode during the cascade process.

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