A temperature sensor of silicon-based non-equilibrium interference structure

Abstract

The application relates to the technical field of light sensing application and structure, in particular to a silicon-based unbalanced interference structure temperature sensor, which comprises an input waveguide, a Y beam splitter, a sensing arm waveguide, a reference arm waveguide and a total reflection structure; the tail end of the input waveguide is connected with the head end of the Y beam splitter, the first tail end and the second tail end of the Y beam splitter are respectively connected with the head end of the sensing arm waveguide and the head end of the reference arm waveguide; the total reflection structure is arranged at the tail ends of the sensing arm waveguide and the reference arm waveguide; the base mode light of the input waveguide is divided into two beams of equal power light through the Y beam splitter, and the two beams of equal power light are coupled to the sensing arm waveguide and the reference arm waveguide respectively, and are reflected through the total reflection structure at the tail ends of the sensing arm waveguide and the reference arm waveguide; the two-way reflected light returns to the Y beam splitter along the original path and interferes, the physical lengths of the sensing arm waveguide and the reference arm waveguide are not equal, and the unbalanced interference structure is formed. The application effectively improves the temperature detection precision.

Description

Technical Field

[0001] This invention relates to the field of optical sensing applications and structural technology, specifically to a temperature sensor with a silicon-based non-equilibrium interference structure. Background Technology

[0002] In industrial manufacturing and high-voltage power transmission, operating devices operate for extended periods in complex electromagnetic multiphysics environments, making core components susceptible to overheating, breakdown, and mechanical fatigue. Sensors are essential for accurately sensing their operational status. Traditional electrical sensor technology is mature, especially in data processing performance; however, due to environmental power limitations, it is difficult to meet the requirements of complex electromagnetic environments for sensor insulation, passive characteristics, vibration resistance, and compactness. Therefore, optical sensors, with their high insulation strength, simple structure, and strong resistance to electromagnetic interference, have become a viable option.

[0003] Traditional fiber Bragg grating sensors are susceptible to mechanical stress and thermal expansion, requiring additional encapsulation for isolation. Furthermore, they rely on manual splicing and encapsulation, resulting in high mass production costs. Due to the large minimum bending radius of fiber Bragg gratings, compact layouts are difficult to achieve, and splices increase size and complexity (occupying a larger footprint). Fiber optic Mach-Zehnder interferometer (MZI) sensors have sensitivity that depends on the optical path difference between unequal arms; a larger arm length difference provides higher sensitivity, but this also increases the overall size of the device (size > 2). It includes a bending compensation zone; and it is sensitive to the splitting ratio (failure occurs if the deviation is greater than 5%), resulting in stress concentration at the weld point and an increased risk of breakage.

[0004] With the continuous development of silicon-based integration technology, the bottleneck of highly integrated design of basic sensing and signal processing has been broken. Silicon waveguide devices can achieve high refractive contrast, making them compact in size. The Young's modulus of silicon substrates in silicon-based waveguide structures is as high as 130-180 GPa, which is close to the rigidity of steel. It can effectively resist micro-strain caused by external vibration, thus resulting in long device life and application in complex industrial and power scenarios. Silicon materials have high thermo-optic coefficients, making them sensitive to temperature changes. Thanks to the high refractive index contrast, the miniaturization and chip-based design of silicon-based waveguide sensors has become a development trend.

[0005] The Michelson interferometer based on a silicon-based waveguide structure achieves high temperature sensitivity through optimized geometry while miniaturizing on-chip dimensions. A single silicon chip integrates all optical paths (beam splitters, interferometer arms, etc.) without fusion joints, eliminating 90% of vibration-sensitive nodes. For temperature sensing, no external packaging is required, avoiding the problems associated with external packaging of fiber optic sensors, such as air gaps between the sensor and the package, which can lead to slow heat conduction and temperature gradients. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a silicon-based temperature sensor with a non-equilibrium interference structure. The specific technical solution adopted is as follows: This invention provides a silicon-based non-equilibrium interference structure temperature sensor, comprising: an input waveguide, a Y-beam splitter, a sensing arm waveguide, a reference arm waveguide, and a total internal reflection structure; the end of the input waveguide is connected to the beginning of the Y-beam splitter, the first end of the Y-beam splitter is connected to the beginning of the sensing arm waveguide, and the second end of the Y-beam splitter is connected to the beginning of the reference arm waveguide; the total internal reflection structure is disposed at the ends of the sensing arm waveguide and the reference arm waveguide; the fundamental mode light of the input waveguide is split into two equal-power beams by the Y-beam splitter and coupled to the sensing arm waveguide and the reference arm waveguide respectively, and is reflected at the ends of the sensing arm waveguide and the reference arm waveguide by the total internal reflection structure. The two reflected beams return to the Y-beam splitter along their original paths and interfere with each other. The physical lengths of the sensing arm waveguide and the reference arm waveguide are not equal, forming a non-equilibrium interference structure.

[0007] In some possible implementations, the total internal reflection structure includes a first total internal reflection mirror and a second total internal reflection mirror; the sensing arm waveguide includes a first curved asymptotic waveguide connected to its first end and a first straight waveguide connected to its last end; the reference arm waveguide includes a second curved asymptotic waveguide connected to its first end and a second straight waveguide connected to its last end; the shapes of the first curved asymptotic waveguide and the second curved asymptotic waveguide conform to cubic Bézier curves, such that the waveguide direction gradually changes from 0° to 180°, and the first straight waveguide and the second straight waveguide are arranged in opposite parallel directions; the physical length of the sensing arm waveguide is greater than the physical length of the reference arm waveguide; the last end of the first straight waveguide is arranged perpendicular to the mirror surface of the first total internal reflection mirror, and the last end of the second straight waveguide is arranged perpendicular to the mirror surface of the second total internal reflection mirror.

[0008] In some possible implementations, the bending radii of the first and second bent asymptotic waveguides are greater than or equal to... The bending loss is less than 0.007 dB / cm.

[0009] In some possible implementations, the total internal reflection structure includes a third total internal reflection mirror and a fourth total internal reflection mirror; the shape of the sensing arm waveguide conforms to the Euler curve, so that the waveguide direction gradually changes from 0° to 90°; the reference arm waveguide is a straight waveguide, and the end faces of the sensing arm waveguide and the reference arm waveguide intersect perpendicularly at 90°; the physical length of the sensing arm waveguide is greater than the physical length of the reference arm waveguide; the end of the sensing arm waveguide is arranged perpendicularly to the mirror surface of the third total internal reflection mirror, and the end of the reference arm waveguide is arranged perpendicularly to the mirror surface of the fourth total internal reflection mirror.

[0010] In some possible implementations, the minimum radius of curvature of the sensing arm waveguide is greater than or equal to The bending loss is less than 0.007 dB / cm.

[0011] In some possible implementations, the total internal reflection structure includes a total internal reflection mirror; the shape of the sensing arm waveguide conforms to an S-curve composed of two Euler curves, the two Euler curves being anti-symmetrical, and the first Euler curve varying from 0° to different bending radii. , The second Euler curve is obtained by rotating the first Euler curve 180° clockwise from its endpoint. The reference arm waveguide is a straight waveguide, and the ends of the sensing arm waveguide and the reference arm waveguide are on the same end face. The ends of the sensing arm waveguide and the reference arm waveguide are both arranged perpendicular to the mirror surface of the total reflection mirror.

[0012] In some possible implementations, the minimum radius of curvature of the sensing arm waveguide is greater than or equal to The bending loss is less than 0.007 dB / cm.

[0013] In some possible implementations, the sensor structure adopts an SOI structure, which includes a silicon substrate, a buried oxide layer, a waveguide core layer, and a silicon dioxide cladding layer; the waveguide core layer is made of silicon, with a height of 220 nm and a width of 450 nm-550 nm.

[0014] In some possible implementations, the total reflection mirror is a distributed Bragg mirror or a metallic mirror.

[0015] In some possible implementations, the distributed Bragg reflector is formed by alternating stacks of high-refractive-index layers and low-refractive-index layers, with a period number of 8 to 12 pairs, and the refractive index ratio of the high-refractive-index layer to the low-refractive-index layer is greater than or equal to 1.5; the metal structure of the metal reflector is covered with a protective medium layer.

[0016] The present invention has the following beneficial effects: The silicon-based unbalanced interference structure temperature sensor provided by the present invention, by setting a total internal reflection structure at the ends of the sensing arm waveguide and the reference arm waveguide, allows the fundamental mode light of the input waveguide to be split by a Y-beam splitter, then propagate back and forth in the sensing arm and the reference arm and return to the Y-beam splitter to interfere. This design doubles the effective transmission distance of the optical signal in the two arms, thereby increasing the effective optical path difference between the two arms to twice the physical length difference while keeping the on-chip physical size unchanged. This significantly enhances the phase accumulation corresponding to the unit physical length difference, achieving high-precision phase detection in a compact device size. At the same time, since a single Y-beam splitter is used as both the splitting and combining element, the problem of inconsistent splitting ratio caused by manufacturing errors in the traditional dual-coupler structure is avoided, effectively ensuring the light intensity balance of the two arms of interference and improving the contrast (extinction ratio) of the interference fringes. Attached Figure Description

[0017] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the SOI structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a double-armed, anti-parallel, length-asymmetric interference waveguide structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a double-armed vertical, length-asymmetric interference waveguide structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of an interference waveguide structure with two parallel arms in the same direction and asymmetrical length, according to an embodiment of the present invention. Figure 5 This is a structural diagram of the distributed Bragg reflector (DBR) according to an embodiment of the present invention; Figure 6 This is an optical field diagram of an interference waveguide structure with two antiparallel arms and asymmetrical length, according to an embodiment of the present invention. Figure 7 This is an optical field diagram of a double-armed, vertically aligned, length-asymmetric interference waveguide structure according to an embodiment of the present invention. Figure 8 This is an optical field diagram of an interference waveguide structure with parallel, co-directional arms and asymmetrical length, according to an embodiment of the present invention. Figure 9 This is a distributed Bragg reflector (DBR) reflectance spectrum diagram according to an embodiment of the present invention. Figure 10 This is a temperature change spectrum diagram according to an embodiment of the present invention; In the attached figures: 1 is the input waveguide, 2 is the Y-beam splitter, 3 is the first curved gradient waveguide, 4 is the second curved gradient waveguide, 55 is the first straight waveguide, 66 is the second straight waveguide, 5 is the sensor arm waveguide, 6 is the reference arm waveguide, 7 is the total reflection mirror, 8 is the waveguide core layer, 9 is the silicon dioxide cladding, 10 is the buried oxide layer, and 11 is the silicon substrate. Detailed Implementation

[0019] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0020] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0021] It should be understood that the various steps described in the method embodiments of the present invention may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present invention is not limited in this respect.

[0022] The term "comprising" and its variations as used herein are open-ended inclusion, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0023] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0024] Although operations or steps are described in a specific order in the accompanying drawings in the embodiments of the present invention, this should not be construed as requiring these operations or steps to be performed in the specific order or serial order shown, or requiring all of the shown operations or steps to be performed to obtain the desired result. In the embodiments of the present invention, these operations or steps may be performed serially; they may be performed in parallel; or a portion of these operations or steps may be performed.

[0025] The following will describe in detail, with reference to the accompanying drawings, a temperature sensor based on a silicon-based non-equilibrium interference structure provided by an embodiment of the present invention.

[0026] This invention provides a silicon-based non-equilibrium interference structure temperature sensor, comprising: an input waveguide, a Y-beam splitter, a sensing arm waveguide, a reference arm waveguide, and a total internal reflection structure; the end of the input waveguide is connected to the beginning of the Y-beam splitter, the first end of the Y-beam splitter is connected to the beginning of the sensing arm waveguide, and the second end of the Y-beam splitter is connected to the beginning of the reference arm waveguide; the total internal reflection structure is disposed at the ends of the sensing arm waveguide and the reference arm waveguide; the fundamental mode light of the input waveguide is split into two equal-power beams by the Y-beam splitter and coupled to the sensing arm waveguide and the reference arm waveguide respectively, and is reflected at the ends of the sensing arm waveguide and the reference arm waveguide by the total internal reflection structure. The two reflected beams return to the Y-beam splitter along the original path and interfere with each other. The physical lengths of the sensing arm waveguide and the reference arm waveguide are not equal, forming a non-equilibrium interference structure.

[0027] The working mechanism of the aforementioned silicon-based non-equilibrium interference temperature sensor is as follows: Utilizing the significant thermo-optical effect of silicon, the effective refractive index of the silicon waveguide changes with the ambient temperature. Because this invention employs a total internal reflection structure, the optical signal propagates back and forth between the sensing arm waveguide and the reference arm waveguide, making the effective optical path difference between the two arms twice the physical optical path difference of a single transmission. According to the principle of optical interference, the change in effective refractive index will cause the characteristic wavelengths (such as peaks or troughs) of the output interference spectrum to exhibit a monotonically linear shift with temperature. In this embodiment, the temperature sensing sensitivity of this structure can reach 87 pm / ℃.

[0028] The working process of the temperature sensor with the aforementioned silicon-based non-equilibrium interference structure is as follows: The fundamental mode light emitted by the light source enters through the input waveguide, is split into two beams by a 3dBY beam splitter, and enters the sensing arm waveguide and the reference arm waveguide respectively. After being reflected by a total internal reflection structure at the ends of their respective waveguides, the two beams return along their original paths to the Y beam splitter and interfere. Due to the round-trip transmission of the optical signal, the optical path lengths of the sensing arm waveguide and the reference arm waveguide are twice their actual physical lengths, i.e. and , and Let be the physical lengths of the sensing arm waveguide and the reference arm waveguide, respectively. Let the effective refractive indices of the fundamental modes of the sensing arm and the reference arm waveguide be respectively... and The optical path length of the sensing arm waveguide is OP = Optical path length of reference arm waveguide OP = The phase difference ΔΦ between the two waveguide arms is determined by the optical path difference, so ΔΦ = = m represents the interference order. When m is an integer, the interference is constructive; when m is a half-integer, the interference is destructive. When constructive interference occurs, the interference condition is satisfied: , The wavelength is the interference wavelength.

[0029] Refractive index n ( (wavelength) The function, both sides of the above equation Find the differential: Interference order m and dispersion effect Relatedly, M represents the offset of the equivalent interference order.

[0030] Interference order: M = abs(m) [ ]) In the formula: abs represents the absolute value sign.

[0031] Due to the thermal expansion coefficient of silicon (TOE, 2.6) Thermo-optic coefficient (TOC) of silicon 1.86 The difference is two orders of magnitude smaller, and the thermal expansion of the waveguide length can be neglected in temperature sensing analysis. Differentiating both sides of the interference condition formula with respect to temperature T, the temperature sensitivity can be derived. : = = Due to the group refractive index With effective refractive index The relationship is: Therefore, the above temperature sensitivity It can be represented as: = In the formula: T is the temperature. , Represented as width is The group refractive index of the waveguide fundamental mode. As shown in the formula, the temperature sensitivity can be altered by changing the waveguide width of the sensing arm and the reference arm, as well as the thermo-optic coefficient of the material.

[0032] When the length difference between the two arms is different, but the waveguide material and width are the same... , = =n. At this point, the temperature sensitivity can be expressed as: = The free spectral range (FSR) and full width at half maximum (FWHM) of this sensor are defined as follows: FSR= Due to the effect of the mirror, the free spectrum FSR of this structure is half that of the MZI structure with the same arm length difference. The full width at half maximum (FWHM) of this structure is half that of the MZI structure with the same arm length difference, thus doubling the wavelength resolution and improving the accuracy of sensing measurements.

[0033] In one possible implementation, the sensor structure adopts an SOI structure, such as... Figure 1 As shown, the SOI structure includes a silicon substrate 11, a buried oxide layer 10, a waveguide core layer 8, and a silicon dioxide cladding layer 9; the waveguide core layer 8 is made of silicon, with a height of 220 nm and a width of 450 nm-550 nm.

[0034] Specifically, the SOI structure is used to achieve device miniaturization. The thickness of the silicon substrate 11 in this SOI structure is approximately 725 μm; the thickness of the buried oxide layer 10 is approximately 2 μm; and the waveguide core layer 8 is made of silicon (Si), with a height of 220 nm and a width of approximately 500 nm. The core layer has a thickness of approximately 550 nm and a refractive index of 3.45. It supports TE fundamental mode transmission, ensuring single-mode optical transmission. The silicon dioxide cladding layer 9 has a thickness of approximately 550 nm and a refractive index of 1.4447. Due to the high refractive index difference between the core layer and the cladding layer, the fundamental mode light is confined to the core layer for transmission, enabling miniaturization and chip-based device manufacturing.

[0035] In one possible implementation, the total internal reflection structure is a distributed Bragg mirror or a metallic mirror. Both distributed Bragg mirrors (DBR) and metallic mirrors can achieve a reflectivity of ≥99% and a reflection bandwidth of approximately 250–300 nm.

[0036] In one possible implementation, the distributed Bragg reflector is formed by alternating stacks of high-refractive-index layers and low-refractive-index layers, with 8 to 12 pairs of periods, and the refractive index ratio of the high-refractive-index layer to the low-refractive-index layer is greater than or equal to 1.5; the metal structure of the metal reflector is covered with a protective medium layer.

[0037] Specifically, the distributed Bragg reflector (DBR) is formed by alternating deposition of 8–12 pairs of high-refractive-index layers and low-refractive-index layers made of materials such as TiO2 / SiO2, Si3N4 / SiO2, Ta2O5 / SiO2, and HfO2 / SiO2. The high-refractive-index layer of the DBR is made of one of TiO2, Ta2O5, HfO2, or Si3N4, specifically TiO2, with a thickness of 165 nm (n≈2.35). The low-refractive-index layer is made of SiO2 or SiOx, specifically SiO2, with a thickness of 267 nm (n≈1.45). Approximately 10 pairs of high-refractive-index and low-refractive-index layers are deposited alternately, resulting in a small number of alternating layers, an equivalent reflection loss of <0.02 dB, and high reflectivity. It boasts advantages such as 99% accuracy, a reflection bandwidth of 250–300 nm, and excellent thermal stability. The wide reflection bandwidth of the DBR allows it to adapt to broadband light sources or multi-wavelength temperature measurements, improving the dynamic range of temperature measurement. Plasma-enhanced chemical vapor deposition (PECVD) or magnetron sputtering deposition processes are employed to achieve film thickness uniformity of ±1 nm, ensuring the flatness of the reflection spectrum and the consistency of the reflection peak positions. During fabrication, the silicon waveguide end face is first planarized. A very thin dielectric impedance matching layer (10–50 nm) is deposited between the flat region of the waveguide end face and the first DBR layer to match the refractive index of the end face, reducing interface scattering and additional phase shift and improving end face adhesion. Then, multiple layers are deposited in the order of high refractive index layer / low refractive index layer. The bottom layer is SiO2 as a protective layer (stable, oxidation-resistant, and corrosion-resistant), with a small refractive index difference with air to reduce additional reflection. Figure 5 A structural diagram of the distributed Bragg reflector (DBR) is shown.

[0038] Metal mirrors are mirrors obtained by employing a metal coating. The advantages of metal mirrors are that their reflectivity is consistent over a wide spectral range and is independent of the incident angle and polarization state. Furthermore, metal mirrors exhibit weak dispersion, minimal correlation between reflection phase shift and wavelength, and do not introduce additional phase shift. This metal mirror is a thin film of Ag, Al, or Au, or a metal / dielectric composite structure, coated with a SiO2 or Si3N4 protective dielectric layer with a thickness of 50–200 nm to improve the mirror's environmental stability and interface compatibility with silicon waveguides. The protective dielectric layer, i.e., the metal coating, can be fabricated using vapor deposition or sputtering techniques, and is typically glass or metal placed on a substrate. This embodiment uses a 9-layer silver protective coating to enhance reflectivity (average reflectivity of 99.3%), exhibiting high reflectivity and a high damage threshold. Then, apply three or four thin layers of dielectric material, such as amorphous silicon dioxide (SiO2) or silicon nitride (Si3N4), on top of the metal coating. These two materials can increase wear resistance to protect the metal coating from oxidation or scratches.

[0039] The curved waveguide in the aforementioned silicon-based unbalanced interferometric temperature sensor is designed using Euler or Bezier curves, with a minimum radius of curvature ≥15μm, bending loss ≤0.007dB / cm, and mode matching degree ≥98%. This structure can be configured as a reverse parallel type, a vertical type, or an S-shaped forward parallel type. It can achieve adjustable on-chip aspect ratio and adjustable dual-arm coated end faces according to the requirements of interference structures with the same arm length difference.

[0040] In one possible implementation, the total internal reflection structure includes a first total internal reflection mirror and a second total internal reflection mirror; the sensing arm waveguide includes a first curved asymptotic waveguide connected to its first end and a first straight waveguide connected to its last end; the reference arm waveguide includes a second curved asymptotic waveguide connected to its first end and a second straight waveguide connected to its last end; the shapes of the first curved asymptotic waveguide and the second curved asymptotic waveguide conform to cubic Bézier curves, such that the waveguide direction gradually changes from 0° to 180°, and the first straight waveguide and the second straight waveguide are arranged in opposite parallel directions; the physical length of the sensing arm waveguide is greater than the physical length of the reference arm waveguide; the last end of the first straight waveguide is arranged perpendicular to the mirror surface of the first total internal reflection mirror, and the last end of the second straight waveguide is arranged perpendicular to the mirror surface of the second total internal reflection mirror.

[0041] Specifically, such as Figure 2 As shown, the silicon-based unbalanced interferometric temperature sensor provided in this embodiment is a dual-arm antiparallel, length-asymmetric interferometric waveguide structure. This structure adopts the aforementioned SOI structure, and its main body consists of an input waveguide 1, a 3dBY branch 2, a first curved asymmetric waveguide 3, a second curved asymmetric waveguide 4, a first straight waveguide 55, a second straight waveguide 66, and a total reflection mirror 7. The first curved asymmetric waveguide 3 and the first straight waveguide 55 constitute the sensing arm waveguide, while the second curved asymmetric waveguide 4 and the second straight waveguide 66 constitute the reference arm waveguide.

[0042] The input waveguide 1 is a single-mode straight-input waveguide used to receive incident light, and the 3dBY beam splitter 2 sets the branch angle. 3°, insertion loss The incident light, at a power of 0.15 dB, is split into two beams of equal power by a 3 dBY branch. These beams enter the first curved asymptotic waveguide 3 and the second curved asymptotic waveguide 4, respectively, and then enter the first straight waveguide 55 and the second straight waveguide 66. The shapes of both the first curved asymptotic waveguide 3 and the second curved asymptotic waveguide 4 conform to the cubic Bézier curve equation. In the formula: Indicates a parameter, 0≤ ≤1, , , and Here are the coordinates of the four control points of the Bézier curve, obtained through... , , and The coordinates of these four control points allow the waveguide bending angle to gradually change from 0° to 180°, avoiding losses caused by mode mismatch and the excitation of higher-order modes. The total reflection mirror 7 includes a first total reflection mirror and a second total reflection mirror, both of which employ the aforementioned distributed Bragg reflector or metallic reflector. The end of the first straight waveguide 55 is perpendicular to the mirror surface of the first total reflection mirror, and the end of the second straight waveguide 66 is perpendicular to the mirror surface of the second total reflection mirror. By placing the first and second total reflection mirrors at the ends of the two opposing waveguide arms, a double-mirror reflection structure with opposite end faces is obtained, achieving an antiparallel double-arm asymmetric interference structure. The two beams of light passing through the first straight waveguide 55 and the second straight waveguide 66 are reflected by the first and second total reflection mirrors respectively and return along their original physical paths.

[0043] In one possible implementation, the bending radii of the first and second curved asymptotic waveguides are greater than or equal to... The bending loss is less than 0.007 dB / cm.

[0044] Specifically, the bending radius R of the first curved asymptotic waveguide 3 and the second curved asymptotic waveguide 4 μm, bending loss less than 0.005 dB / cm. Physical length of the sensing arm waveguide. The physical length of the reference arm waveguide is greater than the reference arm waveguide. The difference in physical length between the two is defined as The two beams of light transmitted through the sensing arm waveguide and the reference arm waveguide are reflected by the total internal reflection mirror 7 and return along their original physical paths, resulting in a difference in the actual physical distance of the optical signal transmission between the two arms. The optical path difference between the two arms at the output end of the 3dBY branch 2 is 2n. Where n is the effective refractive index of the sensing arm and the reference arm. The change in effective refractive index of the sensing arm waveguide and the reference arm waveguide when the ambient temperature changes. Change in interference phase difference In the formula: This indicates the change in the ambient temperature. Indicates temperature. Indicates the effective refractive index of both arms. Indicates the initial ambient temperature. Indicates the initial ambient temperature The interference wavelength value. Because the total internal reflection mirror allows the optical signal to travel back and forth, this chip structure achieves twice the optical path difference while maintaining the same on-chip physical dimension arm length difference, under the same temperature change. Interference phase change This doubles the sensitivity of phase detection.

[0045] In one possible implementation, the total internal reflection structure includes a third total internal reflection mirror and a fourth total internal reflection mirror; the shape of the sensing arm waveguide conforms to the Euler curve, so that the waveguide direction gradually changes from 0° to 90°; the reference arm waveguide is a straight waveguide, and the end faces of the sensing arm waveguide and the reference arm waveguide intersect perpendicularly at 90°; the physical length of the sensing arm waveguide is greater than the physical length of the reference arm waveguide; the end of the sensing arm waveguide is arranged perpendicularly to the mirror surface of the third total internal reflection mirror, and the end of the reference arm waveguide is arranged perpendicularly to the mirror surface of the fourth total internal reflection mirror.

[0046] Specifically, such as Figure 3 As shown, the silicon-based unbalanced interferometric temperature sensor provided in this embodiment is a double-armed, vertically aligned, asymmetric interference waveguide structure. This structure also adopts the aforementioned SOI structure, and its main body consists of an input waveguide 1, a 3dBY beam splitter 2, a sensing arm waveguide 5, a reference arm waveguide 6, and a total reflection mirror 7. The sensing arm waveguide 5 is a curved waveguide, and the reference arm waveguide 6 is a straight waveguide. The end faces of the reference arm waveguide 5 and the sensing arm waveguide 6 intersect perpendicularly at 90°, and the shape change of the reference arm waveguide 6 conforms to the Euler curve, thus allowing the waveguide bending angle to gradually change from 0° to 90°. The Euler curve equation is: x(s) = y(s)= In the formula: x(s) is the abscissa of the arc length, y(s) is the ordinate of the arc length, and s represents the arc length. Curvature It is a change of angle For the derivative of the arc length s, we have Curve length L(s) = The total internal reflection mirror 7 includes a third total internal reflection mirror and a fourth total internal reflection mirror, both of which employ the aforementioned distributed Bragg reflector or metallic reflector. The end of the sensing arm waveguide 5 is arranged perpendicularly to the mirror surface of the third total internal reflection mirror, and the end of the reference arm waveguide 6 is arranged perpendicularly to the mirror surface of the fourth total internal reflection mirror. By arranging the end faces of the sensing arm waveguide 5 and the reference arm waveguide 6 orthogonally and perpendicularly, and each being equipped with a total internal reflection mirror, a double-arm asymmetric interference structure with vertical end face reflection is obtained. The two beams of light passing through the sensing arm waveguide 5 and the reference arm waveguide 6 are reflected by the third and fourth total internal reflection mirrors, respectively, and then return along their original physical paths.

[0047] In one possible implementation, the minimum radius of curvature of the sensing arm waveguide is greater than or equal to The bending loss is less than 0.007 dB / cm.

[0048] Specifically, the minimum radius of curvature of reference arm waveguide 6 is set to The bending loss is less than 0.007 dB / cm, avoiding the excitation of higher-order modes and minimizing mode mismatch loss. The length of waveguide 5 in the sensing arm. The length of the reference arm waveguide 6 is greater than That is, The difference in physical length between the two is defined as The light travels from input waveguide 1 to 3dBY beam splitter 2, where it is split into two beams of equal power. The output light from 3dBY beam splitter 2 enters the sensing arm waveguide 5 and reference arm waveguide 6 on the vertical end face, respectively. After being reflected by total reflection mirror 7, the light returns along its original physical path, resulting in a difference in the actual physical distance the optical signal travels between the two arms. The optical path difference between the two arms at the output end of the 3dBY branch 2 is 2n. Since the sensing arm and reference arm have the same waveguide cross-sectional dimensions (i.e., the same effective refractive index), and n is the effective refractive index of the sensing arm and reference arm, the optical path difference becomes twice the physical optical path difference. This results in the change in temperature of the measured environment. Affecting phase difference The mechanism and Figure 2 The waveguide structures are the same, but the sensing arm waveguide 5 and the reference arm waveguide 6 are perpendicular to each other. Under the premise of limited area in the lateral direction, the difference in length between the two arms in the vertical direction is precisely controlled by Euler bending, and a total reflection mirror is plated on the intersecting end face. This allows for the effective allocation of the fabrication area on the same wafer, so as to maximize the number of wafers per wafer and reduce the cost per wafer.

[0049] In one possible implementation, the total internal reflection structure includes a total internal reflection mirror; the shape of the sensing arm waveguide conforms to an S-curve composed of two Euler curves, which are inversely symmetrical, and the first Euler curve varies from 0° to different bending radii. , The second Euler curve is obtained by rotating the first Euler curve 180° clockwise from its endpoint. The reference arm waveguide is a straight waveguide, and the ends of the sensing arm waveguide and the reference arm waveguide are on the same end face. The ends of the sensing arm waveguide and the reference arm waveguide are both arranged perpendicular to the mirror surface of the total reflection mirror.

[0050] Specifically, such as Figure 4 As shown, the silicon-based unbalanced interferometric temperature sensor provided in this embodiment is a double-arm parallel interferometric waveguide structure with asymmetrical length. This structure also adopts the aforementioned SOI structure. Its main body consists of a single-mode input waveguide 1, a 3dBY beam splitter 2, a sensing arm waveguide 5, a reference arm waveguide 6, and a total reflection mirror 7. The sensing arm waveguide 5 is a curved waveguide, and the reference arm waveguide 6 is a straight waveguide. The relative positions of the sensing arm waveguide 5 and the reference arm waveguide 6 are positively parallel, and their ends are on the same end face. The shape of the sensing arm waveguide 5 conforms to two Euler curves. , Forming an S-curve, the curve , Reverse symmetry, the first segment of the Euler curve From 0 Change to , Then the second Euler curve Through the first Euler curve The endpoint is obtained by rotating 180° clockwise from the center. The ends of both the sensing arm waveguide 5 and the reference arm waveguide 6 are arranged perpendicularly to the surface of the total reflection mirror 7. By placing the ends of the sensing arm waveguide 5 and the reference arm waveguide 6 on the same end face and using the same total reflection mirror on the same end face, the beams from both arms are reflected simultaneously. The two beams of light passing through the sensing arm waveguide 5 and the reference arm waveguide 6 are reflected by the total reflection mirror 7 and return along their original physical paths. The total reflection mirror 7 uses either a distributed Bragg reflector or a metallic reflector as described above.

[0051] In one possible implementation, the minimum radius of curvature of the sensing arm waveguide is greater than or equal to The bending loss is less than 0.007 dB / cm.

[0052] Specifically, the minimum radius of curvature R of the sensing arm waveguide 5 The bending loss is less than 0.007 dB / cm, avoiding losses caused by mode mismatch or the excitation of multimodes. The length of waveguide 5 in the sensing arm. ( + (The length is greater than that of reference arm waveguide 6) That is, The difference in physical length between the two is defined as .same Figure 2 Change in ambient temperature to be measured Affecting phase difference The mechanism and Figure 2 The middle waveguide structure is the same, the difference is that the sensing arm waveguide 5 and the reference arm waveguide 6 are coated with a total reflection mirror 7 on the same end face. According to the actual needs of the project, a total reflection mirror is coated on a single end face to ensure the consistency of the reflectivity of the two arms and reduce the coating process steps and coating accuracy requirements.

[0053] Figure 6 The optical field diagram of the aforementioned double-armed, antiparallel, length-asymmetric interference waveguide structure is shown. Single-mode light is split into two beams of uniform power by a 3dBY branch. After reflection by the total reflection mirror 7, the two beams return along their original paths to the first curved asymmetric waveguide 3 and the second curved asymmetric waveguide 4. (As shown...) Figure 6 As shown in (a), the cross-sectional optical field distribution returning to the input end of the curved waveguide exhibits good symmetry and is consistent with... Figure 6The standard straight waveguide fundamental mode field distribution shown in (b) is highly approximate. This indicates that the optical signal transmitted in the waveguide maintains a good fundamental mode (single-mode) transmission state and does not excite significant higher-order modes due to waveguide bending. This proves that the mode mismatch loss of this structure is small, the light deflection on the bending side after passing through the two bending waveguides is small, the equivalent insertion loss of the distributed Bragg reflector is small, and the bending waveguide of the Bezier curve can control the additional loss within a reasonable range.

[0054] Figure 7 The optical field diagram of the above-mentioned double-armed vertical, length-asymmetric interference waveguide structure is shown. Figure 7 In Figure (a), the fundamental mode light propagates through the sensing arm (0° to 90°) formed by the Euler curves, returns to the waveguide cross-section at the 3dBY branch via the total reflection mirror. For example... Figure 7 As shown, although the optical signal propagates in a curved waveguide, a phase difference occurs due to the longer outer path than the inner path, and the two round trips through the curved Euler curve cause a slight shift in the optical field energy distribution (i.e., introducing a slight mode coupling loss), the optical field profile at the return point still maintains the complete fundamental mode shape. (Comparison) Figure 7 As can be seen from the fundamental mode light in the straight waveguide shown in (b), Figure 7 The high degree of matching between the returned light field and the standard fundamental mode light field in (a) indicates that the returned light signals from both arms maintain good fundamental mode properties and meet the conditions for coherent light interference.

[0055] Figure 8 The optical field diagram of the aforementioned interferometric waveguide structure with parallel arms in the same direction and asymmetrical length is shown. Figure 8 (a) is a cross-sectional optical field distribution diagram of the fundamental mode light transmitted through the S-shaped curved sensing arm waveguide and reflected back to the 3dBY beam splitter by the total reflection mirror. Figure 8 As shown, although the overlap between the fundamental mode optical field and the outer wall of the waveguide increases slightly (a characteristic of curved waveguides), the overall optical field distribution maintains good symmetry and exhibits clear TE fundamental mode characteristics. This indicates that the mode mismatch loss is small after the optical signal travels through the S-shaped curved waveguide twice. (Comparison) Figure 8 As shown in (b) of the standard straight waveguide fundamental mode optical field, the return optical field of the S-shaped curved waveguide has a high degree of overlap with the straight waveguide fundamental mode field, confirming that the optical signals returned by the two arms meet the coherence conditions required for interference.

[0056] Figure 9The figure shows a simulated reflection spectrum of a 10-pair DBR distributed Bragg reflector used in this embodiment. The results show that the reflectivity is close to 99.9% over a wide wavelength range of 1430 nm to 1820 nm. The reflection spectrum remains flat over the wide range, indicating that the reflector does not introduce a drastic frequency-dependent phase shift; at the same time, the extremely high reflectivity means that the reflected wave power loss is extremely low, which can well meet the requirements of the interference structure for light intensity balance and interference contrast.

[0057] Figure 10 The image shown is from this embodiment. Figure 2 The temperature sensing performance of a double-armed, antiparallel, asymmetric interference waveguide structure was tested. This sensor achieves sensing by monitoring the wavelength shift of the destructive interference (interference valley) in the interference spectrum. In this embodiment, the arm length difference ΔL of the silicon-based unbalanced interference sensor was set to 290 μm, and the widths of the two waveguides were fixed at W = 500 nm. When the temperature changed from 30°C to 80°C, the monitored interference wavelength red-shifted from 1551.5 nm to 1556 nm, with a sensitivity of 87 pm / °C.

[0058] The silicon-based unbalanced interferometric sensor chip provided in this embodiment has significant structural advantages and application value. Firstly, the sensor employs a single Y-branch structure, serving as both a beam splitter and a beam combiner. This avoids the inconsistent beam splitting / combining ratios caused by manufacturing process errors in traditional dual-coupler structures, thereby eliminating additional propagation losses, ensuring the symmetry of the interference light intensity, and effectively improving the interference contrast. Combined with the inherent opto-isolation characteristics of the SOI structure, this device is particularly suitable for harsh environments such as high temperature, high pressure, and strong electromagnetic interference (e.g., industrial manufacturing or nuclear energy monitoring).

[0059] Secondly, regarding layout flexibility, this embodiment provides three waveguide layout schemes. By precisely designing the curved waveguides, the angle between the end faces of the sensing arm and the reference arm can be 180° (reverse parallel), 90° (perpendicular), or 0° (forward parallel / same side). This design allows the ends of the two waveguides to be in different quadrants of the same coordinate system, enabling a high degree of selectivity in the mirror coating direction. While maintaining the same effective arm length difference, designers can flexibly adjust the chip's aspect ratio according to wafer layout requirements, maximizing the area utilization during the same wafer fabrication process, reducing space redundancy, and thus effectively reducing the manufacturing cost of a single chip.

[0060] Finally, compared to the traditional use of optical waveguide loops (LoopMirror) as the reflection structure, this embodiment uses DBR or metal total reflection mirrors at the waveguide end. This not only avoids the large bending radius limitation caused by the loop structure and significantly reduces the overall size of the device, but also eliminates the additional phase error that may be introduced by loop bending, further improving the performance stability and measurement accuracy of the sensor.

[0061] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A temperature sensor with a silicon-based non-equilibrium interference structure, characterized in that, include: The system comprises an input waveguide, a Y-beam splitter, a sensing arm waveguide, a reference arm waveguide, and a total internal reflection structure. The input waveguide is connected at its end to the beginning of the Y-beam splitter. The first end of the Y-beam splitter is connected to the beginning of the sensing arm waveguide, and the second end of the Y-beam splitter is connected to the beginning of the reference arm waveguide. The total internal reflection structure is located at the ends of the sensing arm waveguide and the reference arm waveguide. The fundamental mode light from the input waveguide is split into two equal-power beams by the Y-beam splitter and coupled to the sensing arm waveguide and the reference arm waveguide, respectively. The beams are reflected at the ends of the sensing arm waveguide and the reference arm waveguide by the total internal reflection structure. The two reflected beams return to the Y-beam splitter along their original paths and interfere. The physical lengths of the sensing arm waveguide and the reference arm waveguide are not equal, forming a non-equilibrium interference structure.

2. The temperature sensor with a silicon-based non-equilibrium interference structure according to claim 1, characterized in that, The total internal reflection structure includes a first total internal reflection mirror and a second total internal reflection mirror; the sensing arm waveguide includes a first curved asymptotic waveguide connected to its first end and a first straight waveguide connected to its last end; the reference arm waveguide includes a second curved asymptotic waveguide connected to its first end and a second straight waveguide connected to its last end; the shapes of the first curved asymptotic waveguide and the second curved asymptotic waveguide conform to cubic Bézier curves, so that the waveguide direction gradually changes from 0° to 180°, and the first straight waveguide and the second straight waveguide are arranged in opposite parallel directions; the physical length of the sensing arm waveguide is greater than the physical length of the reference arm waveguide; the last end of the first straight waveguide is arranged perpendicular to the mirror surface of the first total internal reflection mirror, and the last end of the second straight waveguide is arranged perpendicular to the mirror surface of the second total internal reflection mirror.

3. A temperature sensor with a silicon-based non-equilibrium interference structure according to claim 2, characterized in that, The bending radii of the first and second curved asymptotic waveguides are greater than or equal to... The bending loss is less than 0.007 dB / cm.

4. A temperature sensor with a silicon-based non-equilibrium interference structure according to claim 1, characterized in that, The total internal reflection structure includes a third total internal reflection mirror and a fourth total internal reflection mirror; the shape of the sensing arm waveguide conforms to the Euler curve, so that the waveguide direction gradually changes from 0° to 90°; the reference arm waveguide is a straight waveguide, and the end faces of the sensing arm waveguide and the reference arm waveguide intersect perpendicularly at 90°; the physical length of the sensing arm waveguide is greater than the physical length of the reference arm waveguide; the end of the sensing arm waveguide is perpendicular to the mirror surface of the third total internal reflection mirror, and the end of the reference arm waveguide is perpendicular to the mirror surface of the fourth total internal reflection mirror.

5. A temperature sensor with a silicon-based non-equilibrium interference structure according to claim 4, characterized in that, The minimum radius of curvature of the sensing arm waveguide is greater than or equal to The bending loss is less than 0.007 dB / cm.

6. A temperature sensor with a silicon-based non-equilibrium interference structure according to claim 1, characterized in that, The total internal reflection structure includes a total internal reflection mirror; the shape of the sensing arm waveguide conforms to an S-curve composed of two Euler curves, the two Euler curves being anti-symmetrical, and the first Euler curve varying from 0° to different bending radii. , The second Euler curve is obtained by rotating the first Euler curve 180° clockwise from its endpoint. The reference arm waveguide is a straight waveguide, and the ends of the sensing arm waveguide and the reference arm waveguide are on the same end face. The ends of the sensing arm waveguide and the reference arm waveguide are both arranged perpendicular to the mirror surface of the total reflection mirror.

7. A temperature sensor with a silicon-based non-equilibrium interference structure according to claim 6, characterized in that, The minimum radius of curvature of the sensing arm waveguide is greater than or equal to The bending loss is less than 0.007 dB / cm.

8. A temperature sensor with a silicon-based non-equilibrium interference structure according to any one of claims 1-7, characterized in that, The sensor structure adopts an SOI structure, which includes a silicon substrate, a buried oxide layer, a waveguide core layer, and a silicon dioxide cladding layer. The waveguide core layer is made of silicon, with a height of 220 nm and a width of 450 nm-550 nm.

9. A temperature sensor with a silicon-based non-equilibrium interference structure according to any one of claims 2-7, characterized in that, The total reflection mirror is a distributed Bragg reflector or a metallic reflector.

10. A temperature sensor with a silicon-based non-equilibrium interference structure according to claim 9, characterized in that, The distributed Bragg reflector is formed by alternating stacking of high-refractive-index layers and low-refractive-index layers, with a period of 8 to 12 pairs, and the refractive index ratio of the high-refractive-index layer to the low-refractive-index layer is greater than or equal to 1.5; the metal structure of the metal reflector is covered with a protective medium layer.

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