A polymer-based cascaded Mach-Zehnder weak voltage sensor

Abstract

The present invention discloses a polymer-based cascaded Mach-Zehnder weak voltage sensor, which includes an upper cladding, a core layer, and a lower cladding. The core layer of the sensor includes a first-stage Mach-Zehnder electro-optic modulator and a second-stage Mach-Zehnder electro-optic modulator interconnected by 180° bent optical waveguides. Among them, the half-wave voltage of the first-stage Mach-Zehnder electro-optic modulator is higher than that of the second-stage Mach-Zehnder electro-optic modulator, and both the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator are provided with two electrical signal paths. The weak voltage signal is characterized by the output optical intensity of the second-stage Mach-Zehnder electro-optic modulator. This sensor overcomes the drawback of the high half-wave voltage of the traditional silicon-based Mach-Zehnder electro-optic modulator. The electro-optic modulator adopting a two-stage Mach-Zehnder cascaded structure has the characteristics of linear output and small size, and is a weak voltage sensing photonic device with anti-electromagnetic interference and high sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage sensors, and particularly to a polymer-based cascaded Mach-Zehnder weak voltage sensor. Background Art

[0002] With the development of photon integration technology, the photon integration technology with optical signals as carriers has gradually received more and more research and attention. As the core device for electro-optic modulation in a photon integration chip, the Mach-Zehnder electro-optic modulator plays a very important role in the photon integration chip. At present, the research on the Mach-Zehnder electro-optic modulator mainly focuses on improving its modulation rate and bandwidth. As an important parameter of the Mach-Zehnder electro-optic modulator, the half-wave voltage has an important impact on reducing the amplitude of the demodulated signal, improving the device performance, and reducing the system power consumption. Therefore, a Mach-Zehnder electro-optic modulator with a low half-wave voltage, low loss, and compact structure has important research value for constructing a photon integration 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. For this reason, an object of the present invention is to provide a polymer-based cascaded Mach-Zehnder weak voltage sensor, which overcomes the disadvantage of the high half-wave voltage of the traditional silicon-based Mach-Zehnder electro-optic modulator. The electro-optic modulator adopting a two-stage Mach-Zehnder cascaded structure has the characteristics of linear output and small size, and is a weak voltage sensing photon device with anti-electromagnetic interference, light weight, small size, and high sensitivity.

[0004] To solve the above problems, the present invention provides a polymer-based cascaded Mach-Zehnder weak voltage sensor for detecting weak electrical signals. The polymer-based cascaded 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-optic modulator and a second-stage Mach-Zehnder electro-optic modulator connected by 180° bent optical waveguides; the half-wave voltage of the first-stage Mach-Zehnder electro-optic modulator is higher than that of the second-stage Mach-Zehnder electro-optic modulator. Both the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator are provided with two electrical signal paths, and the first-stage Mach-Zehnder electro-optic modulator has no bias voltage, which is beneficial for the second-stage Mach-Zehnder electro-optic modulator to perform more efficient optical signal modulation by using its lower half-wave voltage;

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

[0008] The weak voltage signal is characterized by the output optical intensity of the second-stage Mach-Zehnder electro-optic modulator.

[0009] Preferably, the thickness of the upper cladding and the lower cladding 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 bent waveguides connected to both ends of the modulation arm.

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

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

[0013] Preferably, the modulation arm lengths of the first-stage Mach-Zehnder electro-optic modulator and the second-stage Mach-Zehnder electro-optic modulator are 7000 μm, and the widths are 2 μm.

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

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

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

[0017] In the present invention, the externally applied voltage and the output light intensity are linearly related in 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 technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

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

[0020] Figure 2 is a schematic top-view structure diagram of the core layer pattern in the present invention;

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

[0022] Figure 4 is a process flow chart of the preparation of the present invention (a - g in the figure demonstrate the preparation process of the present invention in sequence);

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

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

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

[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 optical 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 Figures 1 to 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 on PMMA by dry etching process (see Figure 4(in figure (e)), the etching parameters of the core layer are: radio frequency power 200 W, gas flow rate ratio SF4: O2 = 10: 50 sccm, rate about 140 nm / min; then perform oxygen plasma cleaning on the core layer pattern (see Figure 4 in figure (f)), and then spin-coat PDMS again. After the PDMS cladding film is successfully spin-coated, it is cured to form a PDMS upper cladding (see Figure 4 in figure (g)).

[0049] As Figure 5 shown, the polymer-based cascaded weak voltage sensor is formed by connecting a first-stage Mach-Zehnder electro-optic modulator and a second-stage Mach-Zehnder electro-optic modulator with a 180° bent 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 straight waveguides in the coupling region of the X-type coupler form a coupling region. It can be seen from the optical field diagram that the coupling gap is 1 μm. At this time, the coupling efficiency is not less than 90%, and when the two stages are cascaded, light does not scatter at the cascade, ensuring the effective transmission of light. The coupling efficiency between the two straight waveguides in the two coupling regions of each of the two X-type couplers is large enough to achieve almost lossless cascading.

[0050] As Figure 6 shown, the polymer-based cascaded weak voltage sensor is a voltage-sensing photonic device. The output light intensity and the applied voltage present a sine curve. The voltage difference between the highest point and the lowest point is 1.0 V, and the half-wave voltage is 1.0 V. 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. To obtain the linear relationship between the voltage and the output light intensity, the certain range is that the applied voltage value range is 0.2 V - 2.4 V. Within this range, the output light intensity presents a sine curve. In the case of two-stage cascading, it can always output with a lower half-wave voltage, and light does not scatter during the cascading process, realizing the stable transmission of light.

[0051] As Figure 7 shown, in figure (a), the polymer-based cascaded weak voltage sensor inputs a 500 mV sine wave input signal to both the first stage and the second stage through signal electrodes. In figure (a), the waveform diagram of the sine wave input signal is on the left, and the waveform diagram of the corresponding output voltage signal is on the right. The output light intensity is obtained through the voltage-sensing photonic device. According to the relationship between the output light intensity and the voltage, the detected voltage at different times is obtained, and then the output voltage signal diagram is obtained. The input signal frequency is set to 10 Hz, and the output voltage waveform is observed. The output voltage waveform is also a periodic sine wave, with less noise and smoother, without distortion. The results show that under the input signal of a weak voltage of 500 mV, 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 7In Figure (b), the waveform diagram of the polymer-based cascaded weak voltage sensor with a 250 mV sinusoidal input signal input through the signal electrode and the waveform diagram of the corresponding output voltage signal are shown. The input signal frequency is set to 10 Hz. By observing the output voltage waveform, the output voltage waveform is also a periodic sinusoidal wave, with relatively small noise and smoothness, and no distortion. The results show that under the input signal of a weak voltage of 500 mV, the output voltage corresponding to the input signal can be obtained. This weak voltage sensor can recover the input weak sinusoidal signal and realize the detection of weak voltage. Figure 7 In Figure (c), the waveform diagram of the polymer-based cascaded weak voltage sensor with a 100 mV sinusoidal input signal input through the signal electrode and the waveform diagram of the corresponding output voltage signal are shown. The input signal frequency is set to 10 Hz. By observing the output voltage waveform, the output voltage waveform is also a periodic wave, but there are noise and distortion phenomena. Therefore, it can still reflect the periodic law. This weak voltage sensor can also obtain the output voltage corresponding to the input signal, but the effect is relatively poor. Therefore, the polymer-based cascaded weak voltage sensor in this embodiment can measure voltages below 1 V, preferably 100 mV - 1.5 V, and more preferably 250 - 500 mV.

[0052] Finally, the unmentioned parts of the present invention all adopt mature products and mature technical means in the prior art.

[0053] The present invention and its embodiments have been described above. Such description is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar structural modes and embodiments without creative work without departing from the gist of the present invention, they shall fall within 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 weak voltage signal is characterized by the output light intensity of the second-stage Mach-Zehnder electro-optic modulator, wherein the half-wave voltage of the first-stage Mach-Zehnder electro-optic modulator is higher than the half-wave voltage of the second-stage Mach-Zehnder electro-optic modulator, and the first-stage Mach-Zehnder electro-optic modulator has no bias voltage, which is conducive to the second-stage Mach-Zehnder electro-optic modulator to utilize its low half-wave voltage for more efficient optical signal modulation.

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 coupling area is between the two straight waveguides in 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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