A method for calibrating static bias point of electro-optical sensor and electro-optical sensor

Abstract

The present invention discloses a method for process correction of the static bias point of an electro-optical sensor and an electro-optical sensor. The method comprises the following steps: measuring the deviation of the static bias point of the electro-optical sensor from π / 2; and adjusting the effective refractive index of an optical waveguide so that the static bias point of the electro-optical sensor reaches π / 2. The present invention applies an external voltage across a transition metal oxide resistive switching material to adjust its dielectric constant, thereby changing the effective refractive index of the optical waveguide and adjusting the static bias point to π / 2, thereby correcting the process errors that are inevitable in the manufacture of electro-optical sensors. After the external voltage is removed, the dielectric constant of the transition metal oxide resistive switching material remains unchanged, and thus the effective refractive index of the optical waveguide remains unchanged, making the technology passive. The transition metal oxide resistive switching material has a continuous optical adjustment function, continuously changing its dielectric constant under different voltage excitations to meet different application requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a method for process correction of a static bias point of an electro-optical sensor and the electro-optical sensor. Background Art

[0002] Electro-optical sensors based on the linear electro-optical effect of lithium niobate material have become the most mature and widely used type of electric field sensor due to their advantages such as large bandwidth, fast response, small interference to the original field, and resistance to electromagnetic interference.

[0003] Bulk lithium niobate waveguides are fabricated using titanium diffusion or proton exchange processes, while thin-film lithium niobate waveguides are fabricated using dry etching. When the external electric field changes, the refractive index of the lithium niobate material changes linearly, causing a phase shift in the light passing through the lithium niobate waveguide. Through Mach–Zehnder (MZ) interferometry or common-path interferometry, the resulting phase shift is converted into intensity changes, which are then read by a photodetector, enabling electric field measurement.

[0004] The transfer function of the lithium niobate electro-optical sensor needs to operate in the linear region, so a static bias point of π / 2 is required. The static bias point refers to the phase of the electro-optical sensor when there is no external electric field, and is often called the static operating point. For the MZ interference optical path, an asymmetric two-arm structure is required to design the optical path difference between the two arms; for the common-path interference optical path, the width and length of the optical waveguide need to be designed. Due to errors in processes such as photolithography, etching, and scribing, the electro-optical sensor after completion has a problem of static bias point deviation, resulting in a reduced dynamic range of the electric field sensor or even inability to measure. Therefore, using effective methods to correct the problem of static bias point deviation caused by unavoidable process errors is crucial for improving the yield, reducing costs, and improving the performance of electro-optical sensors.

[0005] Existing technology typically involves fabricating multiple optical waveguides on a single chip. This involves coupling an optical fiber to each waveguide, passing light through it, measuring the static bias point, and then selecting the waveguide with the static bias point closest to π / 2 for adhesive dispensing, curing, and packaging. This method is costly, has low yield, is time-consuming, and labor-intensive. Furthermore, it cannot achieve an accurate π / 2 static bias point, compromising the accuracy of electric field measurements.

[0006] Other techniques use active monitoring and feedback control to modulate the static bias point of an electro-optical sensor. However, these techniques not only complicate the electro-optical sensor system, but also introduce power supply issues due to the introduction of active components. This increases the sensor's interference with the field, reduces its electromagnetic interference resistance, and increases the likelihood of system instability. The technical problem addressed by the present invention is how to achieve a precise static bias point for an electro-optical sensor through a passive, efficient, and simple method to correct for inevitable process errors. Summary of the Invention

[0007] In response to the above problems, the present invention discloses a method for process calibration of a static bias point of an electro-optical sensor, comprising the following steps:

[0008] Measure the deviation of the static bias point of the electro-optical sensor from π / 2;

[0009] The effective refractive index of the optical waveguide is adjusted so that the static bias point of the electro-optical sensor reaches π / 2.

[0010] Furthermore, the adjusting the effective refractive index of the optical waveguide so that the static bias point of the electro-optical sensor reaches π / 2 comprises the following sub-steps:

[0011] By applying an external voltage on both sides of the transition metal oxide resistive switching material, the dielectric constant of the transition metal oxide resistive switching material is adjusted, thereby changing the effective refractive index of the optical waveguide so that the static bias point reaches π / 2;

[0012] When the external voltage is removed, the dielectric constant of the transition metal oxide resistive switching material remains unchanged.

[0013] Furthermore, the transition metal oxide resistive switching material includes tungsten trioxide, titanium dioxide and niobium pentoxide.

[0014] Furthermore, the optical path structure of the electro-optical sensor is an MZ interference optical path or a common-path interference optical path.

[0015] An electro-optical sensor is calibrated using the above-mentioned electro-optical sensor static bias point process calibration method, comprising:

[0016] Substrate, lithium niobate optical waveguide, lower electrode, transition metal oxide resistive material layer and upper electrode;

[0017] A lithium niobate optical waveguide is provided on the substrate;

[0018] The lower electrode is arranged on the surface of the substrate and connected to the positive electrode / negative electrode of the external power supply;

[0019] The upper electrode is arranged on the surface of the substrate and connected to the negative electrode / positive electrode of the external power supply;

[0020] The transition metal oxide resistive material layer is arranged between the lower electrode and the upper electrode.

[0021] Furthermore, it also includes: a bonding buffer layer and a supporting material;

[0022] The substrate is arranged on the surface of the supporting material through a bonding buffer layer.

[0023] Furthermore, the substrate is bulk lithium niobate or thin film lithium niobate.

[0024] Furthermore, the bonding buffer layer is silicon dioxide or benzocyclobutene.

[0025] Furthermore, the lower electrode is indium tin oxide or fluorine-doped tin oxide.

[0026] Furthermore, the upper electrode is indium tin oxide, fluorine-doped tin oxide, platinum, aluminum or titanium nitride.

[0027] Furthermore, the support material is bulk lithium niobate, silicon or quartz.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1) By adding a transition metal oxide resistive switching material and adjusting its dielectric constant, the static bias point of the electro-optical sensor is accurately set to π / 2 after fabrication. This corrects the process errors that are inevitable in electro-optical sensor fabrication, improves the yield of the electro-optical sensor chip, and is highly efficient, reducing the cost of electro-optical sensor fabrication.

[0030] 2) The external voltage used to adjust the dielectric constant of the transition metal oxide resistive switching material is removed after the adjustment is completed, leaving the dielectric constant of the transition metal oxide resistive switching material unchanged, and thus the effective refractive index of the optical waveguide remains unchanged. Therefore, this technology is passive, reducing the complexity of the electro-optical sensor system and improving the reliability of the electro-optical sensor system;

[0031] 3) Modulators based on transition metal oxide resistive switching materials have the advantages of simple structure, compatibility with CMOS processes, good size reduction characteristics, and good stability. They can be applied to a variety of electro-optical sensor structures and improve the stability of electro-optical sensor systems.

[0032] 4) The transition metal oxide resistive switching material used has a continuous light regulation function, continuously changes the dielectric constant under different voltage excitations, and reconstructs the electro-optical sensor chip according to the wavelength of the light source, which can meet different application requirements.

[0033] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures indicated in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 It shows a structural schematic diagram according to embodiment 1 of the present invention;

[0036] Figure 2 It shows a structural schematic diagram according to embodiment 2 of the present invention;

[0037] Figure 3 It shows a structural schematic diagram according to embodiment 3 of the present invention;

[0038] Figure 4 A structural diagram of embodiment 4 of the present invention is shown.

[0039] Figure numerals: 1. substrate; 2. lithium niobate optical waveguide; 3-1. lower electrode; 3-2. transition metal oxide resistive material layer; 3-3. upper electrode; 4. bonding buffer layer; 5. supporting material. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0041] Transition metal oxide resistive switching materials have electrochromic properties. Under the action of an external electric field, the optical properties (dielectric constant) of the material will undergo stable and reversible changes due to changes in the carrier concentration distribution.

[0042] A method for process calibration of a static bias point of an electro-optical sensor comprises the following steps:

[0043] Measure the deviation of the static bias point of the electro-optical sensor from π / 2;

[0044] The effective refractive index of the optical waveguide is adjusted so that the static bias point of the electro-optical sensor reaches π / 2.

[0045] Adjusting the effective refractive index of the optical waveguide so that the static bias point of the electro-optical sensor reaches π / 2 comprises the following sub-steps:

[0046] By applying an external voltage across the transition metal oxide resistive switching material, the dielectric constant of the transition metal oxide resistive switching material is adjusted, thereby changing the effective refractive index of the optical waveguide so that the static bias point reaches π / 2; preferably, the external voltage range is 1-10V, that is, the voltage that can cause the transition metal oxide resistive switching material to undergo resistive switching; illustratively, applying an external voltage of 10V across the transition metal oxide resistive switching material reduces its dielectric constant;

[0047] When the external voltage is removed, the dielectric constant of the transition metal oxide resistive switching material remains unchanged, so that the effective refractive index of the optical waveguide remains unchanged, and the static bias point of the electro-optical sensor reaches π / 2.

[0048] Transition metal oxide resistive switching materials include tungsten trioxide (WO3), titanium dioxide (TiO2), and niobium pentoxide (Nb2O5). Modulator devices based on transition metal oxide resistive switching materials have advantages such as simple structure, compatibility with CMOS processes, good size reduction characteristics, and excellent stability. They can be applied to various electro-optical sensor structures and improve the stability of electro-optical sensor systems.

[0049] The optical path structure of the electro-optical sensor is an MZ interference optical path or a common-path interference optical path.

[0050] By adjusting the dielectric constant of the transition metal oxide resistive switching material, the static bias point of the electro-optical sensor is accurately set to π / 2 after fabrication, correcting the inevitable process errors in electro-optical sensor fabrication and improving the yield of the electro-optical sensor chip. The method is highly efficient and reduces the fabrication cost of the electro-optical sensor. The external voltage used to adjust the dielectric constant of the transition metal oxide resistive switching material is removed after the adjustment is completed, leaving the dielectric constant of the transition metal oxide resistive switching material unchanged, thereby keeping the effective refractive index of the optical waveguide unchanged. Therefore, the technology is passive, reducing the complexity of the electro-optical sensor system and improving the reliability of the electro-optical sensor system.

[0051] The principle of the static bias point of the electro-optical sensor is as follows: In the electro-optical sensor of the present invention, the ratio of the output to the input light intensity can be expressed by the following formula:

[0052]

[0053] Among them, the output light intensity I out , input light intensity I in, A is the proportional coefficient, b is the extinction ratio, is the static bias point, is the phase difference caused by the external electric field. Ideally, At this time, the measurement system has linear input-output characteristics under the action of a small electric field; When it deviates seriously from π / 2, such as or The output waveform of the electro-optical sensor will be distorted, leading to the failure of the electro-optical sensor. Therefore, it is hoped that the static bias point Infinitely close to π / 2.

[0054] like Figure 1 As shown in the figure, for the MZ interference optical path, the optical path consists of two optical waveguide arms and two Y branches. The light is evenly divided into two paths at the first Y branch and enters two asymmetric optical waveguide arms. The change of the external electric field causes the refractive index of lithium niobate to change through the linear electro-optic effect, making the optical path of the light passing through the two optical waveguide arms different, and generating a phase difference at the second Y branch. According to formula (1), the intensity of the output light is different, so the phase modulation is converted into intensity modulation. The static bias point of the electro-optical sensor based on the MZ interference optical path The expression is:

[0055]

[0056] Where λ is the wavelength of the light source, n eff is the effective refractive index of the lithium niobate optical waveguide 2, and △L is the optical path difference between the two arms of the MZ interference optical path.

[0057] like Figure 2 As shown, for the common-path interference optical path, the optical path is composed of only a simple straight optical waveguide, and the light becomes linearly polarized light through a polarizer outside the chip. The linearly polarized light is transmitted to the optical waveguide along the slow axis of the polarization-maintaining fiber. The slow axis direction of the incident polarization-maintaining fiber is 45° to the x-axis of the lithium niobate crystal. When the linearly polarized light enters the optical waveguide, the optical power distributed into the TE mode polarized in the y direction and the TM mode polarized in the x direction is basically equal. In the same straight optical waveguide, the two different modes of polarized light are modulated by the external electric field to produce different optical path differences. At the output end of the optical waveguide, the slow axis of the output polarization-maintaining fiber is also 45° to the x-axis of the lithium niobate crystal. At this time, the two modes of light interfere in the fast axis and slow axis of the polarization-maintaining fiber respectively. The fast and slow axis signals in the polarization-maintaining fiber are separated by a polarization beam splitter, and the photodetector can extract the signal of any path to obtain the change in the external electric field. Static bias point of the electro-optical sensor based on the common-path interference optical path The expression is:

[0058]

[0059] Among them, △n eff =nTE -n TM , n TE and n TM are the effective refractive indices of TE mode and TM mode respectively, and L is the length of the optical waveguide modulated by the external electric field.

[0060] According to formulas (2) and (3), the static bias point of the electro-optical sensor is related to the effective refractive index of the mode in the optical waveguide and the length of the optical waveguide. In the process of electro-optical sensor manufacturing, the error of the photolithography process will cause the length and width of the optical waveguide to change, affecting n eff and L; process errors in titanium diffusion or proton exchange can cause variations in the width and depth of the optical waveguide, affecting n eff ; The scribing process will cause the length of the optical waveguide to change, affecting L.

[0061] According to formulas (2) and (3), the static bias point of the electro-optical sensor is also related to the wavelength of the light source. When using an electro-optical sensor, if the wavelength of the existing light source is different from the designed wavelength of the electro-optical sensor, this method can be used to reconfigure the electro-optical sensor chip according to the light source wavelength to meet different application requirements.

[0062] The present invention proposes an electro-optical sensor, which is calibrated using the above-mentioned electro-optical sensor static bias point process calibration method, including:

[0063] Substrate 1, lithium niobate optical waveguide 2, lower electrode 3-1, transition metal oxide resistive material layer 3-2 and upper electrode 3-3;

[0064] A lithium niobate optical waveguide 2 is provided on the substrate 1;

[0065] The lower electrode 3-1 is provided on the surface of the substrate 1 and is connected to the positive / negative pole of the external power supply;

[0066] The upper electrode 3-3 is provided on the surface of the substrate 1 and is connected to the negative electrode / positive electrode of the external power supply;

[0067] The transition metal oxide resistive material layer 3-2 is provided between the lower electrode 3-1 and the upper electrode 3-3, and is used to adjust the effective refractive index of the optical waveguide;

[0068] The electro-optical sensor further comprises: a bonding buffer layer 4 and a supporting material 5;

[0069] The substrate 1 is arranged on the surface of the support material 5 through a bonding buffer layer 4 .

[0070] The optical path structure of the electro-optical sensor is an MZ interference optical path or a common-path interference optical path.

[0071] The resistive switching device includes a lower electrode 3-1, a transition metal oxide resistive switching material layer 3-2, and an upper electrode 3-3.

[0072] The substrate 1 is a bulk lithium niobate or a thin film lithium niobate, and is used to manufacture an optical waveguide.

[0073] The bonding buffer layer 4 is made of silicon dioxide or benzocyclobutene (BCB), and is used to form a buffer between the lattice-mismatched substrate 1 and the supporting material 5 to achieve bonding.

[0074] The lower electrode 3 - 1 is made of indium tin oxide (ITO) or fluorine-doped tin oxide (FTO), and is used to connect to the positive electrode / negative electrode of an external power source.

[0075] The transition metal oxide resistive material layer 3 - 2 serves as a dielectric constant modulation layer.

[0076] The upper electrode 3 - 3 is made of indium tin oxide, fluorine-doped tin oxide, platinum (Pt), aluminum (Al) or titanium nitride (TiN), and is used to connect to the negative electrode / positive electrode of an external power supply.

[0077] The supporting material 5 is bulk lithium niobate, silicon or quartz, which is used to support and stabilize the electro-optical sensor.

[0078] The method for process calibration of the static bias point of an electro-optical sensor of the present invention is applicable to a variety of different electro-optical sensors and is exemplified by the following four different implementations.

[0079] Example 1:

[0080] like Figure 1 As shown, the electro-optical sensor substrate 1 is a bulk lithium niobate substrate, so the electro-optical sensor does not include a bonding buffer layer 4 or a supporting material 5. The lithium niobate optical waveguide 2 utilizes an MZ interference optical path fabricated using a titanium diffusion or proton exchange process. The lower electrode 3-1 is made of indium tin oxide (ITO); the transition metal oxide resistive material layer 3-2 is made of tungsten trioxide (WO3); and the upper electrode 3-3 is made of indium tin oxide. Both Y branches in the MZ interference optical path can be replaced by multimode interferometers (MMIs).

[0081] In this technical solution, the tangent direction of the bulk lithium niobate substrate is x-direction, and the propagation direction of light is along the y-direction. The crystal coordinate system is as follows: Figure 1 The middle coordinate axis is shown.

[0082] Example 2:

[0083] like Figure 2As shown, the electro-optical sensor substrate 1 is a bulk lithium niobate substrate, so the electro-optical sensor does not include a bonding buffer layer 4 or a supporting material 5. The lithium niobate optical waveguide 2 is a common-path interference optical path fabricated using a titanium diffusion or proton exchange process. The lower electrode 3-1 is made of fluorine-doped tin oxide (FTO); the transition metal oxide resistive material layer 3-2 is made of titanium dioxide (TiO2); and the upper electrode 3-3 is made of platinum (Pt).

[0084] In this technical solution, the tangent direction of the bulk lithium niobate substrate is x-cut, and the propagation direction of light is along the z direction. The crystal coordinate system is as follows Figure 2 The middle coordinate axis is shown.

[0085] Example 3:

[0086] like Figure 3 As shown, the electro-optical sensor substrate 1 is made of thin-film lithium niobate, which is deposited on the surface of the support material 5 via a bonding buffer layer 4. The lithium niobate optical waveguide 2 is fabricated using an MZ interferometer optical path using etching or laser processing. The lower electrode 3-1 is made of indium tin oxide (ITO); the transition metal oxide resistive material layer 3-2 is made of niobium pentoxide (Nb2O5); and the upper electrode 3-3 is made of fluorine-doped tin oxide. The bonding buffer layer 4 is made of silicon dioxide. The support material 5 is bulk lithium niobate.

[0087] In this technical solution, the tangent direction of the thin film lithium niobate is x-direction, and the propagation direction of light is along the y direction. The crystal coordinate system is as follows Figure 3 The middle coordinate axis is shown.

[0088] Example 4:

[0089] like Figure 4 As shown, the electro-optical sensor substrate 1 is made of thin-film lithium niobate, which is deposited on the surface of the support material 5 via a bonding buffer layer 4. The lithium niobate optical waveguide 2 is fabricated using a common-path interference optical path using etching or laser processing. The lower electrode 3-1 is made of fluorine-doped tin oxide; the transition metal oxide resistive material layer 3-2 is made of tungsten trioxide (WO3); and the upper electrode 3-3 is made of titanium nitride (TiN). The bonding buffer layer 4 is made of benzocyclobutene. The support material 5 is made of silicon.

[0090] In this technical solution, the tangent direction of the thin film lithium niobate is x-cut, and the propagation direction of light is along the z direction. The crystal coordinate system is as follows Figure 4 The middle coordinate axis is shown.

[0091] The transition metal oxide resistive switching material used has continuous light regulation function, continuously changes the dielectric constant under different voltage excitations, and reconstructs the electro-optical sensor chip according to the wavelength of the light source, which can meet different application requirements.

[0092] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for process calibration of static bias point of electro-optical sensor, characterized in that: The following steps are involved: Measure the deviation of the static bias point of the electro-optical sensor from π / 2; Adjusting the effective refractive index of the optical waveguide so that the static bias point of the electro-optical sensor reaches π / 2 comprises the following sub-steps: A transition metal oxide resistive material layer is used as a dielectric constant modulation layer and is disposed between the lower electrode and the upper electrode; By applying an external voltage on both sides of the transition metal oxide resistive switching material, the dielectric constant of the transition metal oxide resistive switching material is adjusted, thereby changing the effective refractive index of the optical waveguide so that the static bias point reaches π / 2; When the external voltage is removed, the dielectric constant of the transition metal oxide resistive switching material remains unchanged.

2. The method for process calibration of the static bias point of an electro-optical sensor according to claim 1, characterized in that: The transition metal oxide resistive switching material includes tungsten trioxide, titanium dioxide and niobium pentoxide.

3. The method for process calibration of static bias point of electro-optical sensor according to claim 1, characterized in that: The optical path structure of the electro-optical sensor is an MZ interference optical path or a common-path interference optical path.

4. An electro-optical sensor calibrated using the electro-optical sensor static bias point process calibration method according to any one of claims 1 to 3, characterized in that: include: A substrate (1), a lithium niobate optical waveguide (2), a lower electrode (3-1), a transition metal oxide resistive material layer (3-2) and an upper electrode (3-3); A lithium niobate optical waveguide (2) is provided on the substrate (1); The lower electrode (3-1) is arranged on the surface of the substrate (1) and is connected to the positive electrode / negative electrode of the external power supply; The upper electrode (3-3) is arranged on the surface of the substrate (1) and is connected to the negative electrode / positive electrode of the external power supply; The transition metal oxide resistive material layer (3-2) is arranged between the lower electrode (3-1) and the upper electrode (3-3).

5. The electro-optical sensor according to claim 4, characterized in that Also includes: bonding a buffer layer (4) and a support material (5); The substrate (1) is arranged on the surface of the support material (5) via a bonding buffer layer (4).

6. The electro-optical sensor according to claim 4 or 5, characterized in that The substrate (1) is bulk lithium niobate or thin film lithium niobate.

7. The electro-optical sensor according to claim 5, wherein: The bonding buffer layer (4) is silicon dioxide or benzocyclobutene.

8. The electro-optical sensor according to claim 4, wherein: The lower electrode (3-1) is indium tin oxide or fluorine-doped tin oxide.

9. The electro-optical sensor according to claim 4, wherein: The upper electrode (3-3) is indium tin oxide, fluorine-doped tin oxide, platinum, aluminum or titanium nitride.

10. The electro-optical sensor according to claim 5, wherein: The supporting material (5) is bulk lithium niobate, silicon or quartz.

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