Dual-mode self-calibration optical electric field sensor and integrated optical sensing chip thereof

Abstract

The application belongs to the technical field of photoelectric sensing and power system online monitoring, and discloses a dual-mode self-calibration optical electric field sensor and an integrated optical sensing chip thereof. The sensor comprises a light source module, an integrated optical sensing chip, a balance detection module and a signal processing module. On the integrated optical sensing chip, the input TE0 mode is partially converted into the TE1 mode through a mode control unit, the two modes propagate in the same waveguide, and enter the same single micro-ring coupled MZI sensitive unit. Under the action of an external electric field, the refractive index of the electro-optic polymer changes, and the TE0 and the TE1 produce differential phase modulation and resonance response. The output end separates the two modes through a mode beam splitter, and the balance detection module performs amplitude matching and differential processing to extract the electric field difference signal and realize self-calibration measurement. The application has the advantages of compact structure, strong common mode rejection capability, high sensitivity and easy integration, and is suitable for power equipment state monitoring and miniaturized high-precision electric field measurement scenes.

Description

Technical Field

[0001] This invention relates to the field of optical electric field sensing technology, and in particular to a dual-mode self-calibrated optical electric field sensor and its integrated optical sensing chip. Background Technology

[0002] With the increasing demands for smart grids, online monitoring of high-voltage power transmission and transformation equipment, and sensing of complex electromagnetic environments, higher requirements are being placed on the accuracy, stability, anti-interference capability, and integration level of electric field measurement technology. Traditional electric field measurement methods include field-milled electric field sensors, capacitive probes, and optical sensors based on bulk electro-optic crystals. Field-milled sensors typically have complex mechanical structures and low dynamic response speeds, making it difficult to meet the requirements for high-precision, miniaturized, and high-speed response measurements. Capacitive probes are susceptible to the influence of external conductor distribution, grounding status, and electromagnetic coupling, resulting in insufficient insulation safety and anti-interference capabilities. While bulk electro-optic crystal sensors offer certain insulation advantages, they are usually large in size, have complex optical paths, are difficult to debug, and are not conducive to on-chip integration and mass production.

[0003] With the development of silicon-based integrated photonics technology, electric field sensors based on on-chip optical structures such as Mach-Zehnder interferometers (MZI) and microring resonators have gradually become a research hotspot. Mach-Zehnder interferometers can convert minute refractive index changes caused by external electric fields into detectable light intensity changes, exhibiting high phase resolution. Microring resonators can amplify response changes caused by refractive index perturbations using high quality factor resonance characteristics, demonstrating high sensitivity. Based on this, by combining MZI interferometer structures with microring resonator structures and using electro-optic polymers with nonlinear electro-optic effects as the sensing material, a new type of integrated optical electric field sensor scheme with MZI, microrings, and electro-optic polymers as the core architecture has been formed.

[0004] However, existing integrated optical electric field sensors still have the following shortcomings: First, single-mode sensing structures are highly sensitive to environmental disturbances such as temperature drift, mechanical vibration, packaging stress, and light source fluctuations. Output drift caused by external common-mode factors often masks the actual electric field signal, leading to insufficient measurement stability. Second, while using a traditional dual-arm differential structure with a reference arm and a sensing arm can suppress common-mode interference to some extent, the spatial separation of the two optical paths makes it difficult for them to experience completely identical temperature, stress, and vibration disturbances, thus limiting the differential compensation effect. Further analysis reveals that although the two sensing units in this spatially separated differential structure can be designed to be vertically symmetrical or frontally and backally symmetrical, there is a physical distance between them. Under actual packaging and operating conditions, the temperature, stress, and mechanical vibration coupling paths at the two locations cannot be exactly the same. Therefore, the prerequisite for differential operation—that the two sensors are subjected to the same disturbance—is not strictly true in practice. The residual error after differential processing still includes spatial temperature gradient and stress gradient terms, limiting further improvement in the common-mode suppression capability of this type of sensor. When the application environment experiences significant temperature variations or mechanical vibrations, this residual error may increase significantly, affecting measurement accuracy and long-term stability. Finally, a single interferometric or resonant sensing structure cannot simultaneously achieve a balance between sensitivity, dynamic range, and stability, making it difficult to meet the requirements of high resolution and high interference immunity.

[0005] Furthermore, existing integrated optical electric field sensor chips generally employ a single-mode transmission architecture, and the implementation of differential reference functions relies on multiple mutually separated sensing units or microrings on the chip, increasing chip area and the difficulty of process matching. Therefore, it is necessary to propose an on-chip optical electric field sensor with a more compact structure, higher sensitivity, stronger anti-interference capability, and self-calibration capability to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] The technical problem this invention aims to solve is as follows: To overcome the aforementioned technical problems, this invention provides a dual-mode self-calibrated optical electric field sensor and its integrated optical sensing chip. Instead of using two spatially separated sensors or two spatially separated optical paths to achieve differential reference, it simultaneously propagates two transverse electric modes, TE0 and TE1, in the same physical waveguide. The difference in mode field distribution between the two modes in the same sensing element generates different responses to the applied electric field, and the electric field signal is extracted through mode splitting and balanced detection differential. Because the two modes propagate along a common path, common-mode disturbances such as temperature, vibration, packaging stress, and light source power fluctuations are naturally highly consistent, potentially eliminating the inherent spatial inconsistency error term in spatially separated differential structures from a physical mechanism perspective.

[0007] The technical solution adopted by the present invention to solve its technical problem is: on the one hand, an integrated optical sensing chip is provided, and on the other hand, a dual-mode self-calibrated high-precision optical electric field sensor including the integrated optical sensing chip is provided.

[0008] The present invention provides an integrated optical sensing chip, comprising: an input grating coupler, a mode modulation unit, an MZI interference structure, a resonant microring, an electro-optic polymer, a mode beam splitter, and an output grating coupler.

[0009] The input grating coupler is used to couple light from an external light source into the on-chip waveguide in TE0 mode; the mode modulation unit is located after the input grating coupler and is used to convert some TE0 mode components into TE1 mode components, and then combine the TE0 mode components and TE1 mode components and connect them to the dual-mode waveguide so that the TE0 mode components and TE1 mode components propagate together in the same waveguide.

[0010] The dual-mode waveguide is connected to the same single-microring coupled MZI sensing unit. The sensing unit is composed of the MZI interference structure coupled to a single resonant microring, and the electro-optic polymer covers the resonant microring. Under the action of an applied electric field, the electro-optic polymer, an organic electro-optic material with nonlinear electro-optic effects, undergoes a refractive index change due to the Pockels effect, altering the effective refractive index and phase of the TE0 and TE1 mode components. Furthermore, due to the different mode field distributions of the two mode components, the effective refractive index changes differ between them, resulting in differentiated responses to the electric field within the same sensing unit. Simultaneously, because the two mode components propagate along the same path, non-electric field common-mode disturbances such as temperature changes, mechanical vibrations, packaging stress, and light source power fluctuations have a high degree of consistency in their effects on the two mode components.

[0011] The mode beam splitter is located after the output of the single micro-ring coupled MZI sensitive unit and is used to re-separate the TE0 mode component and TE1 mode component after common propagation. The re-separated TE0 mode component and TE1 mode component enter the two output grating couplers from the two output ports of the mode beam splitter, respectively.

[0012] Furthermore, the mode modulation unit includes a Y-branch structure and a mode multiplexer; the input end of the Y-branch structure is connected to the output end of the input grating coupler, the first output branch of the Y-branch structure maintains the TE0 mode, and the second output branch of the Y-branch structure is connected to the input end of the mode multiplexer; the mode multiplexer is an asymmetric directional coupler, composed of a narrow waveguide and a wide waveguide arranged side by side, and its output end is combined with the first output branch of the Y-branch structure and connected to the same dual-mode waveguide to output a dual-mode composite light containing both TE0 and TE1 mode components. The beam splitting ratio of the Y-branch structure, the coupling length of the asymmetric directional coupler, and the width and spacing of the narrow and wide waveguides are configured such that the power ratio of the TE0 mode component to the TE1 mode component in the dual-mode composite light is 1:1, to ensure that the signal amplitudes of the two detection branches connected to the balanced detection module and the output grating coupler are matchable within the gain adjustment range.

[0013] Furthermore, the MZI interferometric structure includes two interferometric arms split by a 1×2 beam splitter and a beam combiner, with the two interferometric arms serving as the sensing arm and the reference arm, respectively. The resonant microring, a racetrack microring, is positioned on one of the interferometric arms and coupled to it via a coupling waveguide. It utilizes high-quality factor resonance characteristics to enhance the effective refractive index perturbation response caused by the applied electric field, thereby improving detection sensitivity. The dimensions of the dual-mode waveguide and the parameters of the resonant microring are configured such that the TE0 mode component and the TE1 mode component have different mode field distributions, effective refractive index changes, or electric field overlap integrals in the MZI interferometric structure and the resonant microring, exhibiting different sensitivities to the applied electric field.

[0014] Furthermore, the mode beam splitter is a mode demultiplexer, used to import the TE0 mode component and TE1 mode component after common propagation into different output ports so that the subsequent balanced detection module can detect them independently.

[0015] Furthermore, the integrated optical sensing chip is manufactured using silicon-on-insulator (SOI) technology, with a top silicon layer thickness of 210 nm. 230nm, preferably 220nm, with a dual-mode waveguide width of 0.8μm. 1.5 μm, preferably 1 μm, with a microring radius of 20 μm. 100 μm, preferably 60 μm. This invention does not rely on the complete overlap of the two mode resonant peaks, nor does it require the resonant wavelength interval to be smaller than the linewidth of the narrow-linewidth laser. The preferred approach is to use a broadband light source, ensuring that the resonant peaks of both the TE0 and TE1 mode components fall within the light source's operating bandwidth and detection window, and setting their respective readout points in the linear ramp region of the corresponding resonant peak. The two resonant peaks can partially overlap, but this is not a necessary condition; more reasonably, they should remain distinguishable but both within the readable resonant slope range, thus achieving both resonance enhancement and preserving the differentiated electric field response due to different mode field distributions. The dual-mode waveguide is coupled to the resonant microring, and its waveguide width, coupling gap, and microring radius are configured to satisfy the following conditions: both the TE0 and TE1 mode components transmit with low loss; a broadband light source is used so that the resonance peaks of both the TE0 and TE1 mode components fall within the light source's operating bandwidth and detection window, and their respective readout points are set in the linear ramp region of the corresponding resonance peak, so that both mode components obtain effective resonant ramp responses; the resonant responses of the two mode components are different to form a detectable differential signal.

[0016] Furthermore, the mode multiplexer in the mode modulation unit, the bent section on the dual-mode waveguide in the integrated optical sensing chip, the beam splitting and combining regions in the MZI interference structure, the coupling region of the resonant microring, and the waveguide dimensions, bending radius, coupling gap, and coupling length of the mode beam splitter are jointly configured to ensure that the crosstalk between the TE0 mode component and the TE1 mode component is less than -15dB, so as to ensure that the two output signals after mode beam splitting have a stable and calibrable relationship.

[0017] Furthermore, the resonant microring is a single racetrack-shaped microring. Existing solutions typically employ a dual-microring structure, with a sensing microring and a reference microring providing the electric field response and reference standard, respectively. However, during the manufacturing process, the two microrings are affected by factors such as sidewall roughness, etching deviation, and local stress, leading to differences in resonant wavelength, quality factor, and coupling coefficient. Moreover, the matching relationship may drift during long-term operation. This invention uses a single microring where the TE0 and TE1 mode components generate a resonant response within the same microring. External temperature and stress disturbances affect the microring as a whole simultaneously, impacting both mode components and ensuring high consistency in non-electric field common-mode disturbances. The electro-optic polymer covers the microring, and the different mode field overlap integrals between the TE0 and TE1 mode components and the electro-optic polymer cause differentiated electric field responses in the two mode components. Thus, consistency in the common-mode environment and differences in the electric field response are simultaneously achieved within the same physical structure.

[0018] This invention provides a dual-mode self-calibrating high-precision optical electric field sensor, comprising a light source module, an optical sensing chip, a balanced detection module, and a signal processing module. The optical sensing chip is an integrated optical sensor provided by this invention, and the light source module serves as an external light source for the optical sensing chip. The balanced detection module has at least two detection branches, with two output grating couplers connected to the two detection branches of the balanced detection module respectively. Both detection branches are equipped with gain adjustment units. The output terminal of the balanced detection module is connected to the signal processing module; the signal processing module performs differential processing on the two signals, outputting a difference signal related to the applied electric field, thereby achieving self-calibration measurement.

[0019] Furthermore, the balanced detection module includes a first optical detection branch and a second optical detection branch. The first optical detection branch receives the TE0 mode component signal, and the second optical detection branch receives the TE1 mode component signal. The gain adjustment unit is configured to adjust the amplitudes of the two signals received by the first and second optical detection branches to be equal under zero electric field or calibration conditions to maximize common-mode rejection capability. The signal processing module includes a differential operation unit. The input terminals of the differential operation unit are connected to the output terminals of the first and second optical detection branches, respectively, to eliminate common-mode components caused by temperature drift, mechanical vibration, packaging stress, and light source power fluctuations. The output terminal of the differential operation unit outputs a difference signal related to the external electric field. The resonant response difference between the TE0 mode component and the TE1 mode component is within the gain compensation range and linear operating range of the balanced detection module.

[0020] Furthermore, the light source module is a broadband light source, and its output spectrum covers the working band of the single micro-ring coupled MZI sensing unit to ensure stable transmission and response detection of the TE0 mode component and the TE1 mode component in the integrated optical sensing chip.

[0021] The present invention has the following advantages over the prior art: 1. The integrated optical sensing chip provided by this invention employs TE0 and TE1 dual-mode propagation in the same waveguide, ensuring that the two modes experience identical physical environments. This eliminates spatial inconsistency errors introduced by the different positions of the two sensing units from a physical mechanism perspective. The use of a single microring structure avoids the process mismatch problem between the two microrings. Both TE0 and TE1 modes share the same microring, simultaneously achieving both common-mode consistency and electric field response differences. Only a single microring and a dual-mode waveguide are needed to generate dual signals for differential self-calibration, offering significant advantages in terms of on-chip area and process consistency. Through a composite design of MZI interference structure and microring resonant structure, the advantages of high resolution in interferometric detection and high sensitivity in resonance enhancement are combined. The dual-mode self-calibrated high-precision optical electric field sensor provided by this invention, by integrating the aforementioned optical sensing chip and combining it with a gain-adjustable balanced detection module and a differential signal processing module, effectively eliminates the common-mode effects caused by temperature drift, mechanical vibration, packaging stress, and light source power fluctuations, achieving high-precision self-calibrated electric field measurement. The device is manufactured using silicon-on-insulator (SiI) technology, featuring a compact structure that facilitates on-chip integration and mass production. It is suitable for applications such as power equipment condition monitoring, electromagnetic compatibility testing, sensing of complex electromagnetic environments, and miniaturized high-precision electric field measurement.

[0022] 2. This invention combines a single microring coupled to an MZI sensing element with dual-mode co-path propagation to simultaneously achieve common environmental reference and differential response extraction within the same physical structure. Existing solutions typically require two independent sensors or a dual-microring structure to achieve differential self-calibration, while this invention achieves the same differential self-calibration effect with only a single microring and a dual-mode waveguide. It offers significant advantages in terms of on-chip area, packaging consistency, and process error consistency, and its structure is more compact and easier to integrate.

[0023] 3. The single-microring structure avoids the process mismatch problem between dual microrings. In the dual-microring scheme, even if the two microrings have the same design parameters, processing errors, local stress, and long-term drift can lead to resonance condition mismatch, affecting differential accuracy. In this invention, the TE0 and TE1 modes share the same microring. The influence of external disturbances on the microring as a whole acts simultaneously on both modes, resulting in higher consistency of the non-electric field common mode, which is beneficial for differential cancellation. The change in refractive index of the electro-optic polymer caused by the applied electric field shows response differences due to the different mode field distributions of the two modes, thus achieving both common mode consistency and electric field response differences.

[0024] 4. By combining the MZI interference structure and the micro-ring resonator structure, the advantages of high resolution in interferometric detection and high sensitivity in resonance enhancement are combined. This can significantly enhance the optical phase change caused by a small electric field and achieve high-sensitivity detection of weak electric field disturbances.

[0025] 5. By using a gain-adjustable balanced detection module in conjunction with a mode beam splitter, amplitude matching and precise differential analysis are performed on TE0 and TE1 mode signals, effectively eliminating the common-mode effects caused by temperature drift, mechanical vibration, packaging stress, and light source power fluctuations, and achieving self-calibration measurement.

[0026] 6. The device is manufactured using silicon-on-insulator (SiI) technology, featuring a compact structure that facilitates on-chip integration and mass production. It is suitable for applications such as power equipment condition monitoring, electromagnetic compatibility testing, sensing of complex electromagnetic environments, and miniaturized high-precision electric field measurement. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the integrated optical sensing chip structure of the present invention.

[0028] Figure 2 This is a schematic diagram of the pattern multiplexer in this invention.

[0029] Figure 3 This is a schematic diagram illustrating the optical field transmission principle of a single micro-ring coupled MZI sensing unit.

[0030] Figure 4 This is a schematic diagram of the overall composition of the dual-mode self-calibrated high-precision optical electric field sensor of the present invention.

[0031] In the figure, 1 is the input grating coupler, 2 is the Y-branch structure, 3 is the mode multiplexer, 4 is the MZI interference structure, 5 is the electro-optic polymer, 6 is the resonant micro-ring, 7 is the mode demultiplexer, and 8 is the output grating coupler. Detailed Implementation

[0032] The invention will now be described in further detail with reference to the accompanying drawings. It should be emphasized that the following description is merely exemplary and not intended to limit the scope or application of the invention.

[0033] Example 1

[0034] This embodiment provides an integrated optical sensing chip, such as Figure 1 As shown, the chip includes an input grating coupler 1, a mode modulation unit, an MZI interference structure 4, a resonant microring 6, an electro-optic polymer 5, a mode beam splitter, and an output grating coupler 8. This chip is manufactured using silicon-on-insulator (SiI) technology, with a top silicon layer thickness of 210 nm. 230nm, preferably 220nm, with a dual-mode waveguide width of 0.8μm. 1.5 μm, preferably 1 μm, with a microring radius of 20 μm. 100μm, preferably 60μm.

[0035] External light is coupled into the on-chip waveguide in TE0 mode via input grating coupler 1. The mode modulation unit is located after input grating coupler 1, converting part of the TE0 mode component into TE1 mode component, and then combining the TE0 mode component and TE1 mode component and connecting them to the dual-mode waveguide, so that the TE0 mode component and TE1 mode component propagate together in the same waveguide.

[0036] The dual-mode waveguide is connected to the same single micro-ring coupled MZI sensing element, such as Figure 1 As shown, the sensitive unit consists of an MZI interference structure 4 coupled with a single resonant microring 6, with an electro-optic polymer 5 covering the resonant microring 6. Under the action of an applied electric field, the electro-optic polymer 5 is an organic electro-optic material with a nonlinear electro-optic effect. Due to the Pockels effect, its refractive index changes, altering the effective refractive index and phase of the TE0 and TE1 mode components. The electro-optic polymer 5 can be made of poly(methyl methacrylate-co-Disperse Red 1 acrylate) (PMMA / DR1), with polymethyl methacrylate (PMMA) as the main chain and Disperse Red 1 (DR1) functional groups branched on the sides. The chromophore accounts for 25%, the electro-optic coefficient is 11 pm / V, and the glass transition temperature is 102℃. After completing the chip waveguide etching and electro-optic polymer coating, the electro-optic polymer layer covering the resonant microring needs to be polarized to give it a significant Pockels effect. The specific polarization steps are as follows: First, upper and lower electrodes are respectively set above and below the chip, or a silicon substrate is used as the lower electrode, and the upper electrode is formed above the micro-ring region by metal evaporation. Then, the chip is heated to near the glass transition temperature of the polymer. For the PMMA / DR1 material used in this embodiment, it is heated to 130℃±5℃. At this temperature, a DC high voltage is applied through the electrodes to make the electric field strength in the electro-optic polymer layer reach 60V / μm~100V / μm, and the polarization time is 20~30 minutes. The temperature is kept constant during the polarization process. Finally, while maintaining the polarization electric field, the chip is slowly cooled to room temperature at a rate of 5~10℃ / min, and the electric field is removed, thereby fixing the molecular orientation of the chromophores. After the above polarization treatment, the electro-optic polymer has a stable linear electro-optic effect and can change the effective refractive index of the covering waveguide under the action of an external electric field.

[0037] The dimensions of the dual-mode waveguide and the parameters of the resonant microring 6 are configured such that the TE0 mode component and the TE1 mode component have different mode field distributions, effective refractive index changes, or electric field overlap integrals in the MZI interference structure 4 and the resonant microring 6, thus forming differentiated responses to the electric field within the same sensitive unit. Simultaneously, due to the co-path propagation of the two mode components, the effects of non-electric field common-mode disturbances such as temperature changes, mechanical vibrations, packaging stress, and light source power fluctuations on the two mode components are highly consistent. The sensing arm and reference arm of the MZI interference structure are both of the same type of dual-mode waveguide, and the two arms are of equal length or have a fixed length difference. The reference arm does not have a microring and only serves as a straight waveguide transmission channel. Since the dual-mode waveguide structures of the two arms are identical, the propagation constants of the TE0 and TE1 modes differ consistently in the two arms. Therefore, without an external electric field, the interference state output by the MZI is the same for both modes. An external electric field only changes the mode phase in the microring region of the sensing arm, thereby disrupting the equilibrium. In this embodiment, the two interferometer arms of the MZI interferometer structure are arranged in a symmetrical layout with equal lengths, and the sensing arm and the reference arm are located in the same material layer of the same chip, and are formed synchronously through the same photolithography step. The spacing between the two interferometer arms is on the order of micrometers, exhibiting high consistency in terms of heat conduction and stress distribution. Therefore, the temperature and stress gradients between the two arms of the MZI are much smaller than the spatial temperature and stress gradients between two independent sensors in traditional schemes. Furthermore, since the TE0 mode component and the TE1 mode component both pass through the same MZI arm, even if there is a slight residual mismatch between the two arms, the impact of this mismatch on the two mode components is synchronous, and can be further suppressed as common-mode components in subsequent balanced detection differential processing.

[0038] A mode beamsplitter is positioned after the output of the single-micro-ring coupled MZI sensing unit. It re-separates the TE0 and TE1 mode components after co-path propagation. The re-separated TE0 and TE1 mode components then enter two output grating couplers 8 from the two output ports of the mode beamsplitter, respectively, for independent detection in subsequent stages. The mode beamsplitter is a mode demultiplexer 7, which, using the inverse principle of a mode multiplexer, directs the TE0 and TE1 modes to different output ports.

[0039] In this embodiment, the mode modulation unit includes a Y-branch structure 2 and a mode multiplexer 3. The input end of the Y-branch structure 2 is connected to the output end of the input grating coupler 1, splitting the input TE0 mode light into two branches: the first output branch maintains the TE0 mode, and the second output branch is connected to the input end of the mode multiplexer 3. By designing the length and width of the waveguide, the beam splitting ratio can be precisely controlled. Figure 2 As shown, mode multiplexer 3 is an asymmetric directional coupler, consisting of a narrow waveguide and a wide waveguide arranged side by side. Figure 2The width W2 corresponds to a narrow waveguide, which is used to hold the input TE0 mode. Figure 2 The width W1 corresponds to a wide waveguide, which is designed to support the TE1 mode. The two waveguides interact through near-field coupling in the coupling region, transferring some energy from the TE0 mode in the narrow waveguide to the wide waveguide to generate the TE1 mode. The coupling process follows coupled-mode theory, and the mode amplitude satisfies the following differential equation: .in, For the narrow waveguide TE0 mode amplitude, For the wide waveguide TE1 mode amplitude, The coupling coefficient is determined by the waveguide spacing, waveguide width, and the difference in refractive index of the materials. Under phase-matching conditions ( ), after coupling length Afterwards, efficient energy conversion from TE0 to TE1 can be achieved.

[0040] The output of mode multiplexer 3 is combined with the first output branch of Y-branch structure 2 and connected to the same dual-mode waveguide to output a dual-mode composite light containing both TE0 and TE1 mode components. By configuring the beam splitting ratio of Y-branch structure 2, the coupling length of the asymmetric directional coupler, and the width and spacing of the narrow and wide waveguides, the power ratio of the TE0 mode component to the TE1 mode component in the dual-mode composite light is kept at 1:1. This power ratio directly affects the initial amplitude difference between the two signals in the subsequent balanced detection stage. If it deviates too much from the design value, it will exceed the compensation range of the gain adjustment unit and reduce the differential common-mode rejection ratio.

[0041] The combined dual-mode light propagates along a common waveguide, with TE0 and TE1 simultaneously undergoing subsequent MZI and micro-ring sensitive structures. Due to the different transverse mode field distributions of the two modes, their refractive index responses to the applied electric field differ in the region covered by the electro-optic polymer 5, providing a basis for subsequent differential self-calibration.

[0042] In this embodiment, the MZI interference structure 4 converts the refractive index changes of the TE0 and TE1 modes caused by the applied electric field into light intensity changes. It includes two interference arms split by a 1×2 beam splitter and a beam combiner, with the two interference arms serving as the sensing arm and reference arm, respectively. The resonant microring 6, a racetrack-shaped microring, is positioned on one of the interference arms and coupled to it via a coupling waveguide. The radius, coupling coefficient, and waveguide width of the microring resonant cavity are optimized through design to ensure a high quality factor (Q value) within the operating wavelength range, thereby enhancing the effective refractive index response difference between the TE0 and TE1 mode components to the applied electric field.

[0043] like Figure 3 As shown, the initial optical fields entering the sensing arm and reference arm after passing through the 1×2 beam splitter are E and E, respectively. 10 and E 20For a standalone MZI structure, the output light intensities of its sensing arm and reference arm are respectively:

[0044] in , The input Y branch determines the proportion of power distributed between the upper and lower arms. The lengths of the upper and lower arms. Let be the propagation constant. The propagation loss coefficient, Let be the input optical field. For the microring resonator structure, its transfer function is:

[0045] in λ is the wavelength, and t is the transmission coefficient. Let be the transmission coefficient of light traveling one revolution in the micro-ring. This represents the phase change of light as it travels through the microring for one revolution. H For amplitude transmission coefficient, This is the phase response.

[0046] Combining the two equations, the output light intensity of the MZI sensing arm of the composite microring resonator can be obtained as follows:

[0047] Therefore, the output field of the MZI composite microring sensing unit can be derived as follows:

[0048] in These are the equivalent complex weights of the bundle combiner on each of the two arms. and These are the power weighting coefficients, and These represent the phase bias introduced by the beam combiner. Therefore, the final output response can be obtained as follows:

[0049] If the MZI structure is perfectly symmetrical, and both Y branches are ideal 3dB splitters / combiners, and losses are negligible, then the output response can be simplified to:

[0050] As can be seen from the above formula, the output transmittance of the MZI composite microring sensing unit is... Simultaneously affected by the phase difference of the interferometer arms Phase response of microrings Modulation. Under the action of an external electric field, the refractive index of the electro-optic polymer 5 covering the microring changes, leading to... Tiny changes are converted into significant changes in transmittance, thus enabling highly sensitive detection of the electric field.

[0051] Under the dual-mode co-path propagation conditions of this embodiment, both TE0 and TE1 modes propagate together in the same MZI and microring. Due to the differences in mode field distribution, effective refractive index, and overlap integral with the electro-optic polymer 5, the propagation constants of the two modes differ. Phase response of microrings The difference in response coefficients to the applied electric field affects the transmittance of the two output paths. and The differences create a detectable differential signal. Meanwhile, common-mode disturbances such as temperature changes, mechanical vibrations, and packaging stress have a largely synchronous effect on the propagation constants and microring resonance conditions of the two modes, and can be effectively canceled out as common-mode quantities in subsequent differential operations.

[0052] The parameter design of the coupling region between the dual-mode waveguide and the microring is a key engineering aspect of this embodiment. The dual-mode waveguide is coupled to the resonant microring 6, and its waveguide width, coupling gap, and microring radius are configured to meet the following conditions: both the TE0 and TE1 mode components exhibit low-loss transmission, where low-loss transmission means that the transmission loss of both the TE0 and TE1 mode components in the dual-mode waveguide is less than 3dB / cm. Both the TE0 and TE1 mode components form effective resonant responses in the resonant microring 6. An effective resonant response means that the extinction ratio of the resonant peak formed by the mode component in the microring meets the signal detection requirements of the subsequent balanced detection stage, and can generate a resolvable interference signal with the output optical field of the reference arm. The resonant responses of the two mode components have differences to form a detectable differential signal. A detectable differential signal means that after the difference between the two optical signals is processed by gain matching and differential processing of the balanced detection module, the signal-to-noise ratio of the output signal meets the preset electric field measurement accuracy requirements; and the difference does not exceed the range that the subsequent balanced detection stage can compensate for. In this embodiment, the effective resonant response of both modes is achieved as follows: It does not rely on the complete overlap of the resonant peaks of the two modes, nor does it require the resonant wavelength interval to be smaller than the linewidth of the narrow-linewidth laser. A broadband light source, such as a superluminescent diode (SLED) with a center wavelength of 1550 nm and a 3dB bandwidth of 40 nm, is used to ensure that the resonant peaks of both the TE0 and TE1 mode components fall within the operating bandwidth and detection window of the light source. By optimizing the waveguide width and micro-ring radius, for example, a waveguide width of 1.0 μm and a micro-ring radius of 60 μm, the two resonant peaks are made distinguishable but both fall within the spectral range of the light source. The sensor's readout point, i.e., the center wavelength of the light source, is set in the linear ramp region of the corresponding resonant peak. Thus, both mode components can obtain an effective resonant ramp response; that is, a small change in the refractive index of the micro-ring can be converted into a significant change in light intensity. Simultaneously, due to the different mode field distributions of the two modes, their ramp slopes, i.e., resonant sensitivities, differ, thereby forming a detectable differential signal.

[0053] The specific parameters of the sensor chip are determined by selecting appropriate SOI top silicon thickness, dual-mode waveguide width, mode modulation unit structural parameters, and micro-ring radius, so that the chip can stably support TE0 mode and TE1 mode propagation and ensure that the micro-ring has a high quality factor Q value.

[0054] In this embodiment, the waveguide dimensions, bending radius, coupling gap, and coupling length of the mode multiplexer 3 in the mode control unit, the bent section on the dual-mode waveguide in the integrated optical sensing chip, the beam splitting and combining regions in the MZI interference structure 4, the coupling region of the resonant microring 6, and the mode beam splitter are jointly configured to ensure that the crosstalk between the TE0 mode component and the TE1 mode component is less than -15dB. Through the above-mentioned joint optimization control of mode crosstalk, a stable and calibrable relationship is ensured between the two output signals after mode beam splitting.

[0055] In this embodiment, the TE0 mode component and the TE1 mode component propagate in the same waveguide, the same MZI structure, and the same single microring. The two mode components are subjected to the same temperature perturbation and stress perturbation. Common mode suppression depends on the common propagation characteristics of the two intrinsic modes, rather than on the processing consistency and packaging consistency between multiple devices.

[0056] In summary, the integrated optical sensing chip provided in this embodiment simultaneously achieves common environmental reference and differential response extraction within the same physical structure. It achieves the differential self-calibration effect that traditional schemes require two independent sensors or a dual-micro-ring structure using only a single micro-ring and a single dual-mode waveguide. This offers advantages in terms of structural complexity, on-chip area, and packaging consistency. Furthermore, the differential reference shifts from relying on inter-device matching to relying on the common-path propagation characteristics of two intrinsic modes within the same waveguide, breaking through the common-mode suppression limitation caused by the different positions of sensing units in spatially separated differential schemes from a physical mechanism perspective.

[0057] Example 2

[0058] This embodiment provides a dual-mode self-calibrated high-precision optical electric field sensor, such as... Figure 4 As shown, it includes a light source module, an optical sensor chip, a balance detection module, and a signal processing module. The optical sensor chip is an integrated optical sensor chip as described in Embodiment 1, and the light source module serves as an external light source for the optical sensor chip.

[0059] The light source module is a broadband light source, and its output spectrum covers the operating wavelength of the single micro-ring coupled MZI sensing unit to ensure stable transmission and response detection of the TE0 and TE1 mode components in the integrated optical sensing chip. The light output from the light source module is coupled into the on-chip waveguide in TE0 mode through the input grating coupler 1. After passing through the mode modulation unit, dual-mode waveguide, single micro-ring coupled MZI sensing unit, and mode beam splitter, the TE0 and TE1 mode components are output from the two output grating couplers 8, respectively.

[0060] The balanced detection module has at least two detection branches, including a first optical detection branch and a second optical detection branch. Two output grating couplers 8 are connected to the first and second optical detection branches, respectively. The first optical detection branch receives the TE0 mode component signal, and the second optical detection branch receives the TE1 mode component signal. Both branches are equipped with gain adjustment units, which are configured to adjust the amplitudes of the two signals received by the first and second optical detection branches to be equal in zero electric field or calibration conditions, thereby maximizing common-mode rejection capability. The balanced detection module also includes a variable gain transimpedance amplifier (TIA) and a microcontroller. In zero electric field calibration conditions, the microcontroller reads the digital values ​​of the two TIA outputs and adjusts the gain resistor of one of the TIAs via an I2C interface until the two outputs are equal. After calibration, this gain value is fixed.

[0061] Let the output light intensity of the TE0 mode component be The component output light intensity of TE1 mode is The corresponding output currents of the photodetectors are as follows:

[0062] The first and second photodetector branches are equipped with a first photodetector and a second photodetector, respectively, and both photodetectors have a responsivity of 1. After gain adjustment, differential operation is performed to obtain a balanced output signal. :

[0063] in and This is the gain adjustment coefficient for the two detectors. Adjustment is made so that the amplitudes of the two signals are equal when there is no electric field disturbance. This achieves common-mode suppression.

[0064] The output of the balanced detection module is connected to the signal processing module. The signal processing module includes a differential operation unit, whose inputs are connected to the outputs of the first and second photodetector branches, respectively. The differential operation unit performs differential processing on the two signals, and its output outputs a difference signal related to the external electric field.

[0065] Combined with the MZI composite microring transmittance formula The two-channel mode signal can be represented as:

[0066] The balanced differential signal can then be written as:

[0067] Under the influence of an applied electric field, due to the difference in effective refractive index and phase response between the TE0 mode component and the TE1 mode component, the resulting differential signal is related to the electric field intensity. It exhibits a near-linear relationship, and the electric field measurement value can be obtained through calibration:

[0068] in The system sensitivity coefficient, Zero electric field reference bias. Real-time data acquisition... It can achieve high-precision measurement of external electric fields and effectively suppress common-mode noise such as temperature drift, mechanical vibration, packaging stress and light source power fluctuation.

[0069] In this embodiment, the TE0 mode component and the TE1 mode component propagate in the same waveguide, the same MZI structure, and the same single microring. The residual error after differential propagation mainly originates from the difference in response coefficients between the two mode components under the same environment, and no longer includes the temperature gradient and stress gradient terms introduced by the different spatial positions of the sensing units. The difference in response coefficients between the two mode components can be compensated by the gain adjustment unit.

[0070] This embodiment provides a dual-mode self-calibrated high-precision optical electric field sensor. It significantly enhances the optical phase change caused by a small electric field through a single micro-ring coupled MZI structure. Utilizing the common-path propagation of TE0 and TE1 mode components within the same waveguide and sensing element, it achieves high consistency in common-mode perturbations, while the electric field response varies due to different mode field distributions. Combining mode beam splitting and gain-adjustable balanced detection differential processing, it achieves high-precision self-calibrated electric field measurement. This sensor offers advantages such as miniaturization, all-optical integration, and fast response, providing accurate and real-time data output for both AC and static electric field measurements.

[0071] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An integrated optical sensing chip, characterized in that, include: Input grating coupler, mode modulation unit, MZI interference structure, resonant microring, electro-optic polymer, mode beam splitter, and output grating coupler; The input grating coupler is used to couple light from an external light source into the on-chip waveguide in TE0 mode; the mode modulation unit is located after the input grating coupler and is used to convert some TE0 mode components into TE1 mode components, and then combine the TE0 mode components and TE1 mode components and connect them to the dual-mode waveguide so that the TE0 mode components and TE1 mode components propagate together in the same waveguide. The dual-mode waveguide is connected to the same single microring coupled MZI sensing unit, which is composed of the MZI interference structure coupled with a single resonant microring, and the electro-optic polymer is covered on the resonant microring. The mode beam splitter is located after the output of the single micro-ring coupled MZI sensitive unit and is used to re-separate the TE0 mode component and TE1 mode component after co-path propagation. The re-separated TE0 mode component and TE1 mode component enter the two output grating couplers from the two output ports of the mode beam splitter respectively. The mode control unit includes a Y-branch structure and a mode multiplexer; the input end of the Y-branch structure is connected to the output end of the input grating coupler, the first output branch of the Y-branch structure maintains the TE0 mode, and the second output branch of the Y-branch structure is connected to the input end of the mode multiplexer; the mode multiplexer is an asymmetric directional coupler, composed of a narrow waveguide and a wide waveguide arranged side by side, and its output end is combined with the first output branch of the Y-branch structure and connected to the same dual-mode waveguide to output a dual-mode composite light that simultaneously contains TE0 mode components and TE1 mode components.

2. The integrated optical sensing chip as described in claim 1, characterized in that: The beam splitting ratio of the Y-branch structure, the coupling length of the asymmetric directional coupler, and the width and spacing of the narrow and wide waveguides are configured such that the power ratio of the TE0 mode component to the TE1 mode component in the dual-mode composite light is 1:

1.

3. The integrated optical sensing chip as described in claim 1, characterized in that: The MZI interference structure includes two interference arms split by a 1×2 beam splitter and a beam combiner. The two interference arms serve as a sensing arm and a reference arm, respectively. The resonant microring is a racetrack microring, which is set on one of the interference arms and coupled to the interference arm through a coupling waveguide.

4. The integrated optical sensing chip as described in claim 1, characterized in that: The electro-optic polymer is an organic electro-optic material with a nonlinear electro-optic effect. After polarization treatment, it exhibits the Pockels effect, which allows an applied electric field to cause a change in the refractive index of the electro-optic polymer, thereby altering the effective refractive index and phase of the TE0 and TE1 mode components.

5. The integrated optical sensing chip as described in claim 1, characterized in that: The dimensions of the dual-mode waveguide and the parameters of the resonant microring are configured such that the TE0 mode component and the TE1 mode component have different mode field distributions, effective refractive index changes, or electric field overlap integrals in the MZI interference structure and the resonant microring.

6. The integrated optical sensing chip as described in claim 1, characterized in that: The mode beam splitter is a mode demultiplexer used to import the TE0 mode components and TE1 mode components after common propagation into different output ports.

7. The integrated optical sensing chip as described in claim 1, characterized in that: It is manufactured using silicon-on-insulator (SiI) technology, with a top silicon layer thickness of 210 nm. 230nm, dual-mode waveguide width of 0.8μm 1.5μm, microring radius 20μm 100μm.

8. The integrated optical sensing chip as described in claim 7, characterized in that: It is manufactured using silicon-on-insulator (SiI) technology, with a top silicon thickness of 220 nm, a dual-mode waveguide width of 1 μm, and a micro-ring radius of 60 μm.

9. The integrated optical sensing chip as described in claim 7, characterized in that: The dual-mode waveguide is coupled to the resonant microring, and its waveguide width, coupling gap, and microring radius are configured to satisfy the following conditions: both the TE0 and TE1 mode components transmit with low loss; a broadband light source is used so that the resonance peaks of both the TE0 and TE1 mode components fall within the light source's operating bandwidth and detection window, and their respective readout points are set in the linear ramp region of the corresponding resonance peak, so that both mode components obtain effective resonant ramp responses; the resonant responses of the two mode components are different to form a detectable differential signal.

10. The integrated optical sensing chip as described in claim 1, characterized in that: The mode multiplexer in the modal modulation unit, the bent section on the dual-mode waveguide in the integrated optical sensing chip, the beam splitting and combining regions in the MZI interference structure, the coupling region of the resonant microring, and the waveguide dimensions, bending radius, coupling gap, and coupling length of the mode beam splitter are jointly configured to make the crosstalk between the TE0 mode component and the TE1 mode component less than -15dB.

11. A dual-mode self-calibrated high-precision optical electric field sensor, characterized in that, The system includes a light source module, an optical sensing chip, a balanced detection module, and a signal processing module. The optical sensing chip is an integrated optical sensing chip as described in any one of claims 1-10, and the light source module serves as an external light source for the optical sensing chip. The balanced detection module has at least two detection branches, and two output grating couplers are respectively connected to the two detection branches of the balanced detection module. Each of the two detection branches is equipped with a gain adjustment unit. The output terminal of the balanced detection module is connected to the signal processing module. The signal processing module performs differential processing on the two signals and outputs a difference signal related to the applied electric field.

12. The dual-mode self-calibrated high-precision optical electric field sensor as described in claim 11, characterized in that: The balanced detection module includes a first optical detection branch and a second optical detection branch. The first optical detection branch receives the TE0 mode component signal, and the second optical detection branch receives the TE1 mode component signal. The gain adjustment unit is configured to adjust the amplitudes of the two signals received by the first optical detection branch and the second optical detection branch to be equal in a zero electric field or calibration state.

13. The dual-mode self-calibrated high-precision optical electric field sensor as described in claim 11, characterized in that: The signal processing module includes a differential operation unit. The input terminal of the differential operation unit is connected to the output terminal of the first photodetector branch and the output terminal of the second photodetector branch, respectively. The output terminal of the differential operation unit outputs a difference signal related to the external electric field. The difference in the resonant response between the TE0 mode component and the TE1 mode component is within the gain compensation range and linear operating range of the balanced detection module.

14. The dual-mode self-calibrated high-precision optical electric field sensor as described in claim 11, characterized in that: The light source module is a broadband light source, and its output spectrum covers the operating band of the single micro-ring coupled MZI sensing unit.

Images