High-precision asymmetric silicon-based MZI weak electric signal sensor

Abstract

The invention relates to the technical field of silicon-based photon chips, in particular to a high-precision asymmetric silicon-based MZI weak electric signal sensor. Existing physiological electric signal detection mainly adopts an electrical method and has the problems of wearing discomfort, serious motion artifacts, easiness in environmental interference and the like. The silicon-based photon integration technology has the advantages of high sensitivity, strong interference resistance and the like, but the traditional symmetric MZI sensor is limited in detection precision and sensitivity. According to the asymmetric silicon-based MZI sensor provided by the invention, a special organic electro-optical polymer is introduced as a waveguide cladding, and the device structure is optimized, so that the sensor realizes high detection precision of 0.1 mV and high sensitivity of 0.46 mW / V under the conditions of wide range and low driving voltage; a new scheme is provided for non-invasive continuous monitoring of weak physiological electric signals such as electrocardio, myoelectricity and electroencephalogram of the human body, and the method has wide application prospects in the fields of disease diagnosis, health monitoring and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-based photonic chips, and particularly relates to a high-precision asymmetric silicon-based MZI weak electrical signal sensor. Background Art

[0002] Silicon-based photonic chips mainly use optical signals for detection, and have advantages such as high sensitivity, stable performance, miniaturization, and integration. The skin, as the most easily accessible human organ, can provide a large amount of electrophysiological signals for research fields such as medical diagnosis, disease treatment, health monitoring, and human-computer interaction, such as potential signals like ECG, EMG, and EEG. Among them, the ECG signal is one of the important indicators reflecting heart health and is widely used in clinical diagnosis. EMG signals widely exist on the surface of the human skin, and EMG signals can be detected on the epidermis of the human body involving subcutaneous muscle movement. EMG signals can be used in fields such as neuromuscular injury identification, abnormal swallowing muscle monitoring, and athlete rehabilitation and training. EEG signals originate from the tiny potential changes generated in the head by neuron activities in the brain, and the recorded EEG signals can be used in fields such as epilepsy diagnosis and emotion monitoring. Combining with the current health detection field that people are more concerned about, the vital sign signal monitoring technology is mainly used to detect weak electrical signals of the human body such as ECG, EMG, and EEG, and the fluctuation of the bioelectrical signals of ECG, EMG, and EEG is closely related to the health status of the human body.

[0003] Currently, electrocardiographs, electroencephalographs, electromyographs, etc. are generally used in medical treatment to assist doctors in diagnosis and treatment. The above detection methods are all based on the electrical sensing principle to collect vital sign signals. However, because both the skin and the flexible electrode have a certain degree of stretchability, and there are problems such as mechanical behavior mismatch between the skin and the flexible electrode, it will cause discomfort to the skin during wearing and will cause motion artifacts, resulting in inaccurate signal extraction. Although sensors based on the electrical sensing principle to collect vital sign signals have been developed to a certain extent, this method still has disadvantages such as low detection accuracy and relatively single detection environment. At the same time, the current will have a certain stimulation to the skin and is likely to cause discomfort to the human body during the test. As an alternative, optical detection usually uses information such as the intensity, wavelength, phase, and polarization angle of the transmitted light to characterize weak electrical signals of the human body. It collects weak electrical signals of the human body through electrodes on the waveguide surface to achieve continuous weak electrical signal detection, and has characteristics such as continuous detection, fast measurement speed, and strong operability. Therefore, medical devices based on bio-weak electrical signal monitoring technology combined with silicon-based optical waveguide sensing technology can be used for vital sign signal monitoring, and are expected to achieve higher sensitivity and more accurate weak electrical signal detection, bringing more possibilities to the health detection field. This new sensor technology may improve the performance of medical devices in the future and bring more development opportunities to fields such as personalized medicine and telemedicine. Summary of the invention

[0004] The key problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned method of collecting vital signs signals based on the principle of electrical sensing, and to obtain the fluctuation of human electrical signals by combining silicon-based optical waveguide sensing technology for vital signs signal monitoring, so as to achieve high-precision, high-sensitivity and high-integration detection and achieve the purpose of disease diagnosis. Combining photonic chips with weak electrical signals of the human body and using integrated photonic chips to obtain the fluctuation of human electrical signals is a technical problem that needs to be solved in this field.

[0005] A high-precision asymmetric silicon-based MZI weak electric signal sensor, comprising: Lower cladding; A chip layer, wherein an upper coupler, a long modulation arm, a short modulation arm and a lower coupler are arranged in the chip layer; The upper coupler is used to split the input light wave into the long modulation arm and the short modulation arm; the lower coupler is used to converge the light waves transmitted by the long modulation arm and the short modulation arm and output them, so as to realize the detection of the output optical power under different voltages; The long modulation arm comprises a modulation arm and a curved waveguide section, a relatively long straight waveguide section and a curved waveguide section sequentially extending at both ends of the modulation arm, and the short modulation arm comprises a modulation arm and a curved waveguide section, a relatively short straight waveguide section and a curved waveguide section sequentially extending at both ends of the modulation arm; The upper coupler and the lower coupler are arranged on the same straight line, and the upper coupler couples the curved waveguide section at one end of the long modulation arm with the curved waveguide section at one end of the short modulation arm, and the lower coupler couples the curved waveguide section at the other end of the long modulation arm with the curved waveguide section at the other end of the short modulation arm; The long modulation arm is covered with a filling layer; and, The upper cladding layer is provided with a driving electrode and a ground electrode, wherein the driving electrode is used to receive a driving voltage so as to utilize the electro-optic effect of the filling layer to change the effective refractive index of the long modulation arm, thereby causing a phase delay in the light wave on the modulation arm.

[0006] Furthermore, the modulation arm lengths of the long modulation arm and the short modulation arm are consistent, and the modulation arm lengths are both in the range of 300 μm to 380 μm; Furthermore, the modulation arms of the long modulation arm and the short modulation arm are arranged in parallel, and the spacing between them is in the range of 100 μm to 170 μm.

[0007] Furthermore, the modulation arm of the long modulation arm is arranged perpendicularly to the longer straight waveguide section, and the modulation arm of the short modulation arm is arranged perpendicularly to the shorter straight waveguide section; Further, the length of the longer straight waveguide section is greater than the length of the shorter straight waveguide section; Further, the length range of the long straight waveguide section is 30 μm to 42 μm, and the bending radii of the bent waveguide and the curved waveguide section are 20 μm to 27 μm.

[0008] Further, the upper surface of the filling layer is flush with the upper surface of the upper cladding.

[0009] Further, the output optical intensity I of the sensor out satisfies: , where I in is the input optical intensity, and Δθ is the phase difference between the long modulation arm and the short modulation arm; and / or the sensitivity S of the sensor satisfies: , where ΔL is the difference in the modulation arm lengths between the long modulation arm and the short modulation arm, is the relationship between the refractive index of the modulation arm and the refractive index of the waveguide.

[0010] Further, it further includes a signal generator for applying a sine wave electrical signal to the modulation arm to test the electro-optic modulation characteristics of the device through a demodulation system; Further, it further includes an electromyogram signal simulator for applying a weak modulation electrical signal to the modulation arm to test the detection performance of the sensor for physiological electrical signals through a demodulation system.

[0011] By adopting the above technical solutions, each functional layer is sequentially prepared on the base layer, and an asymmetric MZI structure is designed on the chip layer. The CLD-1 / PMMA electro-optic polymer is introduced as the cladding, and driving electrodes are prepared on the modulation arm. The refractive index is modulated by voltage to achieve efficient modulation of optical signals, thereby obtaining high-precision and high-sensitivity weak electrical signal detection performance, overcoming the limitations of traditional electrical measurement methods, and realizing non-invasive continuous detection of weak physiological electrical signals. The filling layer provides necessary mechanical support for the optical waveguide structure, ensuring that the waveguide can remain stable when subjected to external forces or temperature changes and is not easily deformed or broken. Setting the electrode layer on the upper cladding can facilitate processing and integration more conveniently. During the manufacturing process, the upper cladding is the last layer, so manufacturing the electrode layer on it can avoid interfering with the lower-layer structure and is also convenient for subsequent packaging and connection. Setting the electrode layer on the upper cladding can also play a role in protecting the internal structure. As the outermost layer, the electrode layer can effectively prevent the external environment from eroding and damaging the internal structure of the sensor, improving the durability and reliability of the sensor.

[0012] Further, the modulation arm lengths of the long modulation arm and the short modulation arm are both 320 μm, and the arm spacing between the long modulation arm and the short modulation arm is 135 μm.

[0013] By adopting the above technical solutions, the lengths and spacings of the upper short modulation arms are reasonably designed. While ensuring the compact integration of the device, a large modulation arm length difference is obtained, improving the device sensitivity. At the same time, a modulation arm length of 320 μm can achieve efficient electro-optic modulation at a lower driving voltage, reducing the device power consumption.

[0014] Further, the long modulation arm includes a curved waveguide and a straight waveguide. A straight waveguide with a length of 37 μm is provided at the curved waveguide, and the bending radius of the curved waveguide is 24.3 μm.

[0015] By adopting the above technical solutions, a straight waveguide with a specific length and a curved waveguide with a bending radius are introduced into the long modulation arm, balancing the transmission loss of the straight waveguide and the bending loss of the curved waveguide, reducing the transmission loss. At the same time, the device layout is optimized, reducing the device size, which is beneficial to the high-density integration of the device.

[0016] Further, the upper surface of the filling layer is flush with the upper surface of the upper cladding. The doping ratio of CLD-1 in the filling layer is 35 wt%, and the electro-optic coefficient is 79.5 pm / V.

[0017] By adopting the above technical solutions, a straight waveguide with a specific length and a curved waveguide with a bending radius are introduced into the long modulation arm, balancing the transmission loss of the straight waveguide and the bending loss of the curved waveguide, reducing the transmission loss. At the same time, the device layout is optimized, reducing the device size, which is beneficial to the high-density integration of the device.

[0018] By adopting the above technical solutions, a CLD-1 / PMMA polymer with a high electro-optic coefficient is used as the cladding material, and the doping concentration is optimized to make the polymer layer flush with the upper surface of the upper cladding, which not only improves the electro-optic modulation efficiency of the device but also ensures the compatibility of the device manufacturing process, realizing the optimal design of performance and process.

[0019] Further, the modulation arm length difference between the long modulation arm and the short modulation arm is 74 μm, and / or the length of the overall device is 529 μm and the width is 1360 μm.

[0020] By adopting the above technical solutions, the modulation arm length difference of the asymmetric MZI is designed to be 74 μm, ensuring a small device size while achieving high sensitivity, which is convenient for integration; and / or controlling the length and width of the overall device within 529 μm × 136 cm, realizing the miniaturized design of the sensor, providing convenience for integrated applications.

[0021] Further, the driving electrode is used to receive a driving voltage of 0V to 2.1V. Within this voltage range, the input optical power of the sensor changes from 0.96 mW to 0.0003 mW, and / or the detection accuracy of the sensor is not less than 0.1 mV, and the sensitivity is 0.46 mW / V.

[0022] By adopting the above technical solution, by controlling the driving voltage within the range of 0 to 2.1V, a large dynamic range output of 0.96 to 0.0003 mW is obtained, realizing high-precision detection of weak electrical signals; and / or realizing a high detection accuracy of 0.1 mV and a high sensitivity of 0.46 mW / V, greatly improving the performance of the sensor and expanding the application scenarios of the device.

[0023] Further, the upper coupler is used to split the input optical wave into the long modulation arm and the short modulation arm, and / or the driving electrode is used to receive a driving voltage to utilize the electro-optic effect of the filling layer to change the effective refractive index of the long modulation arm, causing a phase delay of the optical wave on the modulation arm, and the lower coupler is used to converge the optical waves transmitted by the long modulation arm and the short modulation arm and output them to realize the detection of the output optical power under different voltages.

[0024] By adopting the above technical solution, the optical wave sequentially undergoes 1×2 MMI splitting, asymmetric MZI modulation, and 2×1 MMI combining. By modulating the refractive index of the long modulation arm with voltage, introducing a phase delay, and amplifying through MZI double-arm interference, the weak electrical signal is converted into an obvious change in the output optical intensity, realizing the functions of electro-optical conversion amplification and high-sensitivity detection.

[0025] Further, the sensor further includes a signal generator and an electromyogram signal simulator. The signal generator is used to apply a sine-wave electrical signal on the modulation arm to test the electro-optic modulation characteristics of the device through a demodulation system, and / or the electromyogram signal simulator is used to apply a weak modulation electrical signal on the modulation arm to test the detection performance of the sensor for physiological electrical signals through a demodulation system.

[0026] By adopting the above technical solution, by using the signal generator to provide a sine-wave electrical signal, the electro-optic modulation characteristics of the device are systematically tested, and the modulation performance is characterized; and / or by using the electromyogram signal simulator to provide real weak physiological electrical signals, the actual detection performance of the sensor is evaluated, laying a foundation for the application of the device in the field of health monitoring. Description of the Drawings

[0027] Figure 1 is the overall structural schematic diagram of the asymmetric silicon-based MZI high-precision weak electrical signal sensor of the present invention; Figure 2 is the top cross-sectional structural schematic diagram of the asymmetric silicon-based MZI high-precision weak electrical signal sensor of the present invention; Figure 3 is a schematic side-sectional structure diagram of the asymmetric silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor of the present invention; Figure 4 is a schematic diagram comparing the output optical powers of the asymmetric silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor of the present invention with different modulation arm lengths and different modulation arm length differences; Figure 5 is the optical field diagram of the asymmetric silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor of the present invention; Figure 6 is a curve graph showing the variation of the output optical power of the asymmetric silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor with different voltages; Figure 7 is a curve graph showing the variation of the output optical power of the asymmetric silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor with different weak electrical signals.

[0028] Reference numerals: 1, base layer; 2, lower cladding layer; 3, chip layer; 4, filling layer; 5, upper cladding layer; 6, electrode layer; 7, long modulation arm; 8, driving electrode; 9, ground electrode; 10, upper coupler; 11, bent waveguide; 12, straight waveguide; 13, lower coupler; 14, short modulation arm; 15, center line. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment

[0030] As Figures 1 to 3 shown, this embodiment provides a high-precision asymmetric silicon-based MZI weak electrical signal sensor, including a base layer 1, a lower cladding layer 2, a chip layer 3, a filling layer 4, an upper cladding layer 5, and an electrode layer 6 arranged in sequence from bottom to top.

[0031] Among them, the base layer 1 serves as the support layer of the device, and materials such as high-resistance silicon, SOI silicon, sapphire, and quartz can be selected. High-resistance silicon is preferred, and the resistivity is not less than 1000 Ω·cm to reduce substrate leakage and parasitic capacitance. The thickness of the base is generally 200 - 1000 μm, preferably 525 μm.

[0032] The lower cladding layer 2 is commonly made of SiO2 and is formed on the surface of the base layer by thermal oxidation or plasma-enhanced chemical vapor deposition (PECVD) process, serving as the buried oxide insulation layer and the lower substrate of the chip layer 3. The thickness of the lower cladding layer is 1 - 5 μm, preferably 3 μm, to suppress the light leakage loss of the substrate. The refractive index of the lower cladding layer is about 1.46, with a large difference from the refractive index of Si, which can form a vertical light confinement condition.

[0033] The chip layer 3 is the layer where the core optical waveguide structure of the device is located. It can be prepared by the SOI wafer smart cut technology or by the solid phase epitaxy technology after the epitaxy of amorphous silicon or polycrystalline silicon by PECVD. The thickness of the core layer is generally less than 500 nm, preferably 220 nm, to meet the single-mode condition. The key optical path structure of the Mach–Zehnder interferometer (MZI interferometer for short) is etched and constructed in the core layer, including the upper coupler 10, the curved waveguide 11, the straight waveguide 12, the long modulation arm 7 and the short modulation arm 14 with unequal lengths, and the lower coupler 13. Among them, the MMI coupler is prepared by the mask plate lithography and ICP etching process, and its size is generally 30 - 90 μm in length and 2 - 6 μm in width, preferably 60 μm in length and 4 μm in width, which can achieve a 3 dB 50:50 beam splitting ratio and the insertion loss is less than 1 dB. The modulation arm is an embedded ridge waveguide, which adopts a two-step etching process. First, a shallow groove is etched, and then it is etched to the base layer, and the embedding depth is 80 - 150 nm, preferably 100 nm. The width of the modulation arm is 400 - 600 nm, preferably 450 nm, to achieve single-mode transmission. The upper short modulation arms are arranged asymmetrically, with the arm lengths both being 300 - 500 μm, preferably 320 μm, the difference in modulation arm lengths being 50 - 100 μm, preferably 74 μm, and the arm spacing being 100 - 200 μm, preferably 135 μm, to balance the phase modulation length and the transmission loss. The length of the straight waveguide in the middle of the long modulation arm is generally 20 - 50 μm, preferably 37 μm, for arranging the driving electrode. The radius of the curved waveguide is generally 20 - 50 μm, preferably 24.3 μm, to reduce the bending radiation loss. The overall transmission loss of the chip layer can be controlled below 3 dB / cm.

[0034] The filling layer 4 achieves high-efficiency electro-optic modulation by utilizing its excellent electro-optic effect. CLD-1 (Controlled Layer Deposited 1) is a technique for thin-film deposition on a polystyrene (PMMA) substrate. CLD-1 is a high-performance organic electro-optic polymer with a π-conjugated structure in the main chain and strong polar substituents in the side chain, having good macroscopic asymmetry and a high electro-optic coefficient. PMMA is a transparent thermoplastic plastic commonly used in optical and electronic devices. As a polymer matrix, PMMA forms an interpenetrating network structure with CLD-1, endowing the material with excellent film-forming properties and stability. The CLD-1 technique can form a uniform functional coating on the PMMA surface, thereby improving its performance. In this embodiment, the mass ratio of CLD-1 doped in PMMA is 20 - 50 wt%, preferably 43 wt%. At this time, the electro-optic coefficient can reach about 80 pm / V, which is an order of magnitude higher than that of traditional LiNbO3, and has small birefringence and low half-wave voltage. The filling layer is prepared by a spin-coating process. The CLD-1 / PMMA solution is spin-coated on the long modulation arm region and cured, and the thickness is the same as that of the upper cladding part. The spin-coating speed is 1000 - 5000 rpm, preferably 3500 rpm, and it is maintained for 60 s. The curing temperature is 120 - 180 °C, preferably 150 °C, and the curing time is 1 - 2 h, preferably 1.5 h. The thickness of the filling layer is 1 - 2 μm, preferably 1.6 μm, and the surface roughness is less than 5 nm. This process is simple to operate and can obtain a polymer film that is uniform, dense, has small roughness, and controllable thickness.

[0035] The upper cladding 5 is commonly made of SiO2 and is deposited on the surface of the core layer by PECVD technology. It serves as a passivation and protection layer for the device and provides a platform for electrode preparation. The thickness of the upper cladding is 1 - 5 μm, preferably 2.5 μm. Before filling with CLD-1 / PMMA, the SiO2 in the long modulation arm region needs to be etched away using BOE solution and mask plate lithography technology. The etching depth is equivalent to the thickness of the filling layer, and then the filling layer is spin-coated to obtain a device structure with a flat surface.

[0036] The electrode layer 6 prepares electrode patterns on the surface of the upper cladding using MEMS processes such as mask plate lithography, sputtering, and stripping. The electrode material can be selected from Al, Au, ITO, etc., preferably Al, which has high conductivity and low cost. The electrode thickness is generally 100 - 500 nm, preferably 300 nm. In this embodiment, the electrodes are in the form of 3 parallel strips. The middle is the ground electrode, and the two sides are signal electrodes. The width is 3 - 10 μm, preferably 5 μm, the spacing is 10 - 50 μm, preferably 20 μm, and the length corresponds to the modulation arm, both being 320 μm. The two signal electrodes on both sides respectively cover the two modulation arms, and an electric field is formed in the filling layer by applying a voltage to adjust the refractive index.

[0037] The overall size of the MZI sensor in this embodiment is approximately 500 - 1000 μm in length and 1000 - 2000 μm in width, preferably 529 μm in length and 1360 μm in width. When voltage signals are applied to the signal electrodes on both sides, the electric field is mainly concentrated in the filling layer of the long modulation arm. Affected by the electro - optic effect, the refractive index of the filling layer changes, thereby modulating the effective refractive index of this modulation arm and causing its phase delay. While for the short modulation arm, since no electric field is applied, the refractive index and phase remain unchanged. When the two light waves are recombined and interfered at the subsequent MMI, due to the phase difference, the output intensity changes. By reasonably setting the modulation arm length difference, electrode length, and driving voltage, when the phase difference Δθ=(2n + 1)π (n is an integer), the two light waves are superposed in the reverse direction, and at this time, the minimum light intensity can be achieved at the output port of the MZI. Through calculation and testing, for the device in this embodiment at a wavelength of 1.55 μm, when Δθ = π, the modulation arm length difference is 74 μm, and the modulation arm length is 320 μm, the driving voltage range only needs to be 0 - 2.1V. At this time, the output optical power changes from 0.96 mW to 0.0003 mW, and the modulation depth is greater than 30 dB. Compared with traditional thermal modulation, pn modulation and other schemes, the driving voltage is greatly reduced, and the modulation sensitivity is improved. By fitting the output response curve to be linear, the sensitivity of the MZI sensor can reach 0.46 mW / V. The change in optical power of the order of 0.1 μW can be detected by an optical power meter, and the corresponding voltage sensitivity can reach the order of 0.1 mV, fully meeting the detection requirements of physiological electrical signals such as electrocardiogram, electromyogram, and electroencephalogram. This sensing scheme has the advantages of high sensitivity, low driving, small size, and easy integration, opening up a new way for silicon - based biosensing.

[0038] Figure 4 It is a schematic diagram comparing the output optical powers of an asymmetric silicon - based MZI high - precision asymmetric silicon - based MZI weak electrical signal sensor with different modulation arm lengths and different modulation arm length differences. For a high - precision asymmetric silicon - based MZI, its output optical field intensity can be expressed as: (1) (2) Therefore, the sensitivity of a high - precision asymmetric silicon - based MZI can be expressed as: (3) In the formula, ΔNeff is the difference in the effective refractive indices of the long modulation arm and the short modulation arm, L is the modulation arm length, λ is the optical wavelength, and are the phase changes between the long modulation arm and the short modulation arm, Δθ is the phase difference generated by the two modulation arms, I in is the input optical intensity, I outLet \(I_{out}\) be the output optical intensity, \(S\) be the sensitivity of the MZI, \(\Delta L\) be the length difference between the long modulation arm and the short modulation arm, and \(n_{eff}\) be the relationship between the effective refractive index of the modulation arm and the waveguide. From the above equations (1) and (2), it can be obtained that the MZI controls the change of its output power intensity by controlling the phase difference between the two modulation arms. From the above equations (3) and [omitted part], it is proportional to the length difference between the long modulation arm and the short modulation arm, and the sensitivity is proportional to the length difference.

[0039] Output optical power comparison for different modulation arm lengths is as Figure 4 As shown in Figure (a) below, when a voltage of 0V - 7V is applied to the driving electrode 8 on the upper surface of the electrode layer 6, the effective refractive index of the long modulation arm 7 changes with the applied external electric field. Therefore, the output optical power of the MZI will change with the change of the applied external electric field. Only when the arm lengths of the long modulation arm 7 and the short modulation arm 14 are 320 µm, the output optical power is monotonic in the voltage range of 0V - 2.1V, and the driving voltage of the MZI can reach the minimum and the sensitivity is the largest at 0.46 mW / (V) at this time; when the arm lengths of the long modulation arm 7 and the short modulation arm 14 are greater than 320 µm, the output optical power is not monotonic in the voltage range of 0V - 2.1V, and the driving voltages of the MZI are all greater than 2.1V, and the sensitivities are all lower than 0.46 mW / (V).

[0040] Output optical power comparison for different modulation arm length differences is as Figure 4 As shown in Figure (b) below, only when the modulation arm length difference of the modulation arm is 74 µm, the output optical power is monotonic in the voltage range of 0V - 2.1V, and the driving voltage of the MZI can reach the minimum of 2.1V, and the sensitivity is the largest at 0.46 mW / (V) at this time; when the modulation arm length difference of the modulation arm is not 74 µm, the output optical power is not monotonic in the voltage range of 0V - 2.1V, and the driving voltages of the MZI are all greater than 2.1V, and the sensitivities are all lower than 0.46 mW / (V).

[0041] Figure 5 is the optical field diagram of the high-precision asymmetric silicon-based MZI weak electrical signal sensor. Only when the arm lengths of the long modulation arm 7 and the short modulation arm 14 are 320 µm, the modulation arm length difference of the asymmetric structure is 74 µm, the arm spacing between the long modulation arm 7 and the lower modulation 14 is 135 µm, the bending radius of the bent waveguide is 24.3 µm, and the length of the straight waveguide is 37 µm, the optical field is effectively confined within the chip layer 3 region. At this time, the extinction ratio of the high-precision asymmetric silicon-based MZI weak electrical signal sensor is 34.77 dB.

[0042] Figure 6It is a graph showing the variation of the output optical power of a silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor with different voltages. The input voltage is taken as the abscissa, and the output optical power when the input optical power is 1 mW is taken as the ordinate. When the arm lengths of the long modulation arm 7 and the short modulation arm 14 are 320 µm and the length difference of the modulation arms of the asymmetric structure is 74 µm, when a voltage of 0 V to 2.1 V is input on the long modulation arm, the input optical power of the corresponding silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor changes from 0.92 mW to 0.0001 mW, its sensing accuracy is not less than 0.1 mV, and the sensitivity is 0.46 mW / (V), which can achieve the detection of high-precision and high-sensitivity weak electrical signals. Table 1 shows the relationship between the output optical power of the silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor and different voltages.

[0043] Table 1 Relationship table of the output optical power of the silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor with different voltages Voltage (V) Output optical power (mW) 0 0.960621316 0.1 0.937154675 0.2 0.90083465 0.3 0.853366048 0.4 0.796797998 0.5 0.733351479 0.6 0.665259392 0.7 0.59463638 0.8 0.523388523 0.9 0.45316583 1.0 0.38535416 1.1 0.321097609 1.2 0.261337439 1.3 0.206849774 1.4 0.158264692 1.5 0.116057966 1.6 0.080523595 1.7 0.051751205 1.8 0.029633727 1.9 0.013913872 2.0 0.004255998 2.1 0.0003297655 Figure 7 It is a graph showing the variation of the output optical power of an asymmetric silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor with different weak electrical signals. The input voltage is taken as the abscissa, and the output optical power is taken as the ordinate. When the arm lengths of the long modulation arm 7 and the short modulation arm 14 are 320 µm and the length difference of the modulation arms of the asymmetric structure is 74 µm, a sine-wave modulation electrical signal is applied to the modulation arm through a signal generator and loaded onto the driving electrode of the asymmetric silicon-based MZI, and its output optical power is as Figure 7 shown in Figure (a) below. The electro-optic modulation phenomenon of the device can be observed, but for signals with small amplitudes, the signals still do not distort the waveform; because EMG signals widely exist on the surface of human skin, EMG signals can be detected on any human epidermis involving subcutaneous muscle movement. EMG signals can be used in fields such as neuromuscular injury identification, abnormal swallowing muscle monitoring, and athlete rehabilitation and training. The present invention constructs a demodulation system for an asymmetric silicon-based MZI high-precision asymmetric silicon-based MZI weak electrical signal sensor, applies a modulation electrical signal to the modulation arm through an electromyogram signal simulator and loads it onto the driving electrode of the asymmetric silicon-based MZI, and experimentally tests the performance of the system, and its output optical power is as Figure 7 shown in Figure (b) below. Embodiment

[0044] On the basis of Embodiment 1, this embodiment optimizes and improves the device structure and material system.

[0045] A stress release layer is inserted between the chip layer and the lower cladding layer, adopting a SiO2 / SiON / SiO2 sandwich structure. The thickness of the middle SiON layer is 20 - 100 nm, preferably 50 nm. This structure can effectively release the thermal mismatch stress between the chip layer and the SiO2 buried oxide layer, reduce the bending deformation of the core layer, and lower the transmission loss.

[0046] The molecular structure of CLD-1 / PMMA is optimized by introducing groups such as C-O-C and C=O into the CLD-1 molecule to enhance the intramolecular charge transfer and further improve the nonlinear electro-optic effect of the material. The electro-optic coefficient of the optimized CLD-1 / PMMA can be increased to over 100 pm / V. At the same time, epoxy resin is doped in PMMA to increase the glass transition temperature of the material to over 200 °C, enhancing the thermal stability of the device.

[0047] A stress compensation design is carried out for the Si waveguide by etching stress release grooves on both sides of the waveguide, with a width of 50 - 200 nm and a depth equal to that of the waveguide. The release grooves can effectively suppress the stress concentration on the sidewalls of the waveguide, reducing the transmission loss of the waveguide to below 1 dB / cm. A gradual curvature design is introduced at the waveguide turning point, changing the arc to an involute, which greatly reduces the intermodal crosstalk at the turning point. At the same time, a parabolic gradual structure is adopted to achieve the gradual modulation of the transverse size of the waveguide, reducing the fiber coupling loss. Embodiment

[0048] Based on Embodiment 1 or 2, this embodiment further integrates an MZI array structure and a CMOS drive circuit.

[0049] The device is monolithically integrated with an N×N MZI sensor array, where the number of rows and columns N of the array can be 4, 8, 16, etc. The structural parameters of each MZI sensor are the same, and the total area of the device is less than 5 mm × 5 mm. The N×N MZI devices are respectively connected to M multiplexers through bus wiring to achieve column selection. Each column has one multiplexer, and each multiplexer controls N MZI devices. The control signal of the multiplexer is provided by the column decoder, which outputs the corresponding M column selection signals (M = 2m) according to the input m-bit binary code. Similarly, the N×N MZI devices are simultaneously connected to N row selection switches through bus wiring, and the control signal of the row selection switch is provided by the row decoder, corresponding to an n-bit binary code (N = 2n). Through the above array addressing scheme, m + n signals can be used to independently address and control the N×N MZI devices.

[0050] A CMOS driver chip is integrated around the silicon photonics chip and fabricated using the CMOS 180nm process. On-chip integrated components include a transimpedance amplifier, an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), a temperature compensation circuit, and a digital signal processing unit, etc. The transimpedance amplifier converts and amplifies the photocurrent output by the MZI into a voltage signal, with an amplification factor of 104 - 108. The ADC digitizes the voltage signal with a resolution of no less than 16 bits. The temperature compensation circuit suppresses temperature drift by regulating the device operating point through negative feedback. The signal processing unit processes the signal, such as amplifying, filtering, and feature extraction. The processed signal is converted by the DAC and sent to an external processor through the IO interface, realizing real-time demodulation and readout of the on-chip signal. This integration scheme highly integrates functional units such as the control, signal acquisition, and processing of multiple MZI sensors within a millimeter-scale chip, featuring small size, low power consumption, high integration, and anti-interference. Embodiment

[0051] Based on any one of Embodiments 1 - 3, this embodiment describes the device packaging and application.

[0052] The vertical packaging of the device is realized by using the through-silicon via (TSV) technology. Ti / Au is sputtered on the back of the silicon substrate as the back metal, and a TSV via array with a diameter of 20 - 50μm is etched. An insulating layer of Si3N4 is sputtered, and copper is electroplated as the filling material. The surface copper is polished off, and finally, Ti / Au is sputtered as the surface metal. The TSV technology can vertically interconnect the top metal and the back pad, realizing the three-dimensional integrated packaging of the chip and effectively reducing the packaging size.

[0053] A convex piezoelectric thin film is prepared on the back of the silicon substrate as an integrated bioelectrode to achieve non-invasive acquisition of weak physiological electrical signals. The piezoelectric thin film material is PVDF, with a thickness of 10 - 50μm and a diameter of 0.5 - 2mm. When there are minute deformations on the skin surface, the piezoelectric thin film generates polarization charges under stress and outputs an electrical signal corresponding to the deformation signal. The MZI sensor can be used for highly sensitive detection of it.

[0054] The MZI sensor chip prepared in this embodiment can be widely applied to wearable devices such as health monitoring electronic skin, smart watches, and smart clothing. By welding the flexible circuit board to the chip and connecting functional modules such as power supply and wireless communication, real-time acquisition of physiological health information such as human heart rate, blood pressure, muscle activity, motion posture, and emotion can be achieved. The test results show that when attached to parts such as the wrist and chest, this MZI sensor can clearly detect electrocardiogram signals with an amplitude of 0.1 - 5 mV, and the repeatability error is less than 5%. After wearing for 8 hours, the performance shows no obvious attenuation. When the sensor array is attached to parts such as the forehead and temple, electroencephalogram signals with rhythms such as α, β, and δ can be effectively acquired, with an amplitude in the range of 5 - 100 μV and a frequency of 0.5 - 30 Hz, and the coincidence degree with the results of medical electroencephalographs is higher than 90%. When attached to the muscle surface, the corresponding electromyogram signals can be detected, with an amplitude of 0.1 - 2 mV and a frequency of 20 - 500 Hz, enabling the assessment of muscle activity status and early warning of fatigue degree.

[0055] In addition, the MZI sensor device provided by the present invention can also be applied to medical health detection instruments. By integrating with modules such as signal amplification and human-machine interface, electrocardiographs, electroencephalographs, electromyographs, etc. with the function of detecting weak physiological electrical signals can be constructed. Compared with traditional instruments, the instruments based on silicon-based MZI have the advantages of small size, light weight, low power consumption, high integration, and high sensitivity. They have broad application prospects in clinical medicine, home healthcare, sports monitoring, and other scenarios.

[0056] In summary, the present invention provides a high-precision asymmetric silicon-based MZI weak electrical signal sensor and its detection method. Compared with the prior art, the innovation points of the present invention are as follows: 1. Introducing a high electro-optic coefficient organic polymer as the waveguide cladding material significantly improves the electro-optic modulation efficiency and sensitivity of the device; 2. Adopting an asymmetric MZI structure, by optimizing the modulation arm length difference and electrode design, a high modulation depth is achieved at a lower driving voltage; 3. Combining the detection of weak physiological electrical signals with silicon-based photon integration technology overcomes many deficiencies of traditional electrical methods and realizes high-sensitivity, low-power-consumption, and small-size wearable physiological signal sensing and analysis. This is of great significance for promoting the application of silicon optoelectronic devices in the field of biomedicine.

[0057] It should be noted that the above embodiments are only the preferred embodiments of the present invention and are not used to limit the protection scope of the present invention. Those skilled in the art can make routine modifications or replacements to the parameters of materials, structures, processes, etc. in the above embodiments without departing from the technical solutions of the present invention, and such modifications or replacements still fall within the protection scope of the present invention. For example, the size parameters, material selection, doping concentration, voltage range, etc. mentioned in the above embodiments are all exemplary, and their specific values can be appropriately adjusted according to actual needs and process conditions, as long as they can solve the technical problems to be solved by the present invention, they are within the protection scope of the present invention.

Claims

1. A high-precision asymmetric silicon-based MZI weak electrical signal sensor, characterized in that, Including, arranged successively from bottom to top: Lower cladding; Chip layer, in which an upper coupler, a long modulation arm, a short modulation arm and a lower coupler are provided; The upper coupler is used to split the input optical wave into the long modulation arm and the short modulation arm; The lower coupler is used to converge the optical waves transmitted by the long modulation arm and the short modulation arm and output them, so as to realize the detection of the output optical power under different voltages; The long modulation arm includes a modulation arm and a bent waveguide section, a longer straight waveguide section and a curved waveguide section arranged successively at both ends of the modulation arm, and the short modulation arm includes a modulation arm and a bent waveguide section, a shorter straight waveguide section and a curved waveguide section arranged successively at both ends of the modulation arm; The upper coupler and the lower coupler are arranged on the same straight line, and the upper coupler couples the curved waveguide section at one end of the long modulation arm and the curved waveguide section at one end of the short modulation arm, and the lower coupler couples the curved waveguide section at the other end of the long modulation arm and the curved waveguide section at the other end of the short modulation arm; The long modulation arm is covered with a filling layer; and, Upper cladding, on which a driving electrode and a ground electrode are provided, and the driving electrode is used to receive a driving voltage, so as to change the effective refractive index of the long modulation arm by using the electro-optic effect of the filling layer, so that the optical wave on the modulation arm generates a phase delay.

2. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, wherein The modulation arm lengths of the long modulation arm and the short modulation arm are the same, and the modulation arm lengths are both in the range of 300μm to 380μm.

3. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, characterized in that The modulation arms of the long modulation arm and the short modulation arm are arranged in parallel, and the spacing range is 100μm to 170μm.

4. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, wherein The modulation arm of the long modulation arm is perpendicular to the longer straight waveguide section, and the modulation arm of the short modulation arm is perpendicular to the shorter straight waveguide section.

5. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, wherein The length of the longer straight waveguide section is greater than the length of the shorter straight waveguide section.

6. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, characterized in that, The length range of the long straight waveguide section is 30μm to 42μm, and the bending radii of the bent waveguide and the curved waveguide section are 20μm to 27μm.

7. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, wherein The upper surface of the filling layer is flush with the upper surface of the upper cladding.

8. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, characterized in that The output optical intensity I of the sensor out satisfies: , where I in is the input optical intensity, and ∆θ is the phase difference between the long modulation arm and the short modulation arm; And / or, the sensitivity S of the sensor satisfies: , where ΔL is the difference in the modulation arm lengths between the long modulation arm and the short modulation arm, is the variation relationship of the refractive index of the modulation arm with respect to the refractive index of the waveguide.

9. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, characterized in that, It also includes a signal generator for applying a sine wave electrical signal to the modulation arm to test the electro-optic modulation characteristics of the device through a demodulation system.

10. The high-precision asymmetric silicon-based MZI weak electrical signal sensor according to claim 1, characterized in that, It also includes an electromyogram signal simulator for applying a weak modulation electrical signal to the modulation arm to test the detection performance of the sensor for physiological electrical signals through a demodulation system.

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