Vernier effect-based high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor

Abstract

The invention discloses a vernier effect-based high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor, and belongs to the technical field of planar optical waveguide integrated devices. The polymer electrolyte consists of a substrate layer, a polymer lower cladding, a polymer grooving layer, a polymer electrolyte core layer and a polymer upper cladding. The polymer electrolyte core layer is of a runway type MRR cascaded optical waveguide structure and is composed of a reference ring, a temperature sensing ring and a humidity sensing ring, a polymer electrolyte core layer material can adsorb water molecules in air, the free ion concentration can change along with the change of humidity and temperature, and then the refractive index of the material changes; the temperature and humidity dual-mode sensing device overcomes the defects of integration level, sensitivity and interference resistance of an existing temperature and humidity sensing device, ultra-compact and ultra-high-sensitivity temperature and humidity dual-mode sensing is achieved, the optical waveguide device is made of polymer materials, and the temperature and humidity dual-mode sensing device has the remarkable advantages of being good in flexibility, simple in process, low in cost, high in efficiency and the like. The method is suitable for various scenes requiring precise environment control or real-time monitoring of tiny changes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of planar optical waveguide integrated devices, and particularly relates to a polymer micro-ring temperature and humidity optical waveguide sensor based on a vernier effect. BACKGROUND

[0002] Temperature and humidity, as key parameters of the environment and physiological state, have important monitoring requirements in many fields such as medical health monitoring, biological reaction process control, industrial automation and modern agriculture. In order to meet the requirements of accurate environmental control and state perception, temperature and humidity sensors need to efficiently and accurately convert the temperature and humidity physical quantities in the environment into electrical signals or optical signals that can be detected and analyzed. Current temperature and humidity measurement technology mainly relies on discrete devices based on electrical principles (such as thermistors and capacitive humidity sensors). Although these technologies are mature, they gradually show limitations when facing the increasing measurement requirements: it is difficult to realize miniaturization and on-chip integration, which limits their application in microsystems; electrical sensors are susceptible to electromagnetic interference and the sensitivity improvement faces physical limits, making it difficult to meet the detection requirements of rapid and weak change signals; and measuring temperature and humidity usually requires two independent sensor units, increasing system complexity, space occupation and cost. In view of the urgent need for integrated and high-performance temperature and humidity sensors, existing research attempts to integrate temperature and humidity sensing functions in a single device unit. However, these integrated schemes often have complex structural designs, requiring high precision and consistency of micro-nano fabrication processes, leading to rising manufacturing costs and declining yields, making it difficult to achieve large-scale, low-cost production and application promotion. Therefore, developing a new type of sensor technology that can simultaneously and rapidly and highly sensitively perceive temperature and humidity changes, with the advantages of compact structure, easy integration, simple preparation process and controllable cost, has become a key problem to be solved in this field. Optical waveguide sensing technology, especially micro-ring resonators based on functional polymer materials, provides a promising technical route for simultaneous sensing of temperature and humidity multi-modal signals due to its inherent high sensitivity, miniaturization, electromagnetic interference resistance and easy on-chip integration. Among them, the vernier effect, as an optical phenomenon that can significantly amplify small resonant wavelength shifts and greatly improve detection sensitivity, provides a new idea for breaking through the performance bottleneck of existing sensors. SUMMARY

[0003] The present application aims at the deficiencies of the existing temperature and humidity sensor in integration, sensitivity and anti-interference performance, and proposes a high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect.

[0004] The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 1 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top.

[0005] The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 1 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 1 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 2 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 1 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 2 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 1 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top. Figure 2 The high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect comprises a substrate layer 1, a polymer lower cladding layer 2, a polymer notch layer 3, a polymer electrolyte core layer 4 and a polymer upper cladding layer 5 from bottom to top.

[0006] The polymer under cladding layer 2 is prepared by a spin coating method on the substrate layer 1, the thickness H1 of the substrate layer 1 is 0.2-1mm, and the thickness H2 of the polymer under cladding layer 2 is 2-20μm; the polymer etching groove layer 3 is prepared by a spin coating and photo-curing, the polymer electrolyte core layer 4 is obtained by photo-etching, wet etching, filling and reactive ion etching (RIE) on the polymer etching groove layer 3, the thickness H3 of the polymer electrolyte core layer 4 and the polymer etching groove layer 3 is the same and is 0.5-10μm, and the width W1 of the polymer electrolyte core layer 4 is 0.5-10μm; the polymer upper cladding layer 5 is prepared by a spin coating and photo-curing, the thickness H4 of the polymer upper cladding layer 5 is 2-10μm; the humidity sensing window 6 is obtained by etching the polymer upper cladding layer 5, the thickness of the humidity sensing window 6 is the same as that of the polymer upper cladding layer 5, and the width W3 of the humidity sensing window 6 is 150-950μm; and the temperature sensing window 7 is obtained by vacuum evaporation, spin coating, photo-etching and wet etching, the thickness H5 of the temperature sensing window 7 is 20-200nm, the width W4 of the temperature sensing window 7 is 10-950μm, and W4>W1, W4=2×R4.

[0007] attached Figure 3(a) is a schematic diagram of the polymer electrolyte core layer 4 structure of the high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on the vernier effect of the application, which is a cascaded runway-type micro-ring resonator (MRR) planar optical waveguide structure composed of a first input straight waveguide 8, a second input straight waveguide 9, a first coupling straight waveguide 10, a second coupling straight waveguide 11, a first semicircular waveguide 12, a third coupling straight waveguide 14, a second semicircular waveguide 13, a first output straight waveguide 15, a third input straight waveguide 16, a fourth input straight waveguide 17, a fourth coupling straight waveguide 18, a fifth coupling straight waveguide 19, a third semicircular waveguide 20, a first straight waveguide 22, a fourth semicircular waveguide 21, a second output straight waveguide 23, a third output straight waveguide 24, a second straight waveguide 25, a sixth coupling straight waveguide 26, a fourth output straight waveguide 27, a fifth input straight waveguide 28, a sixth input straight waveguide 29, a seventh coupling straight waveguide 30, a third straight waveguide 31, an eighth coupling straight waveguide 32, a fifth semicircular waveguide 33, a ninth coupling straight waveguide 34, a sixth semicircular waveguide 36, a fourth straight waveguide 37, a tenth coupling straight waveguide 35, a fifth output straight waveguide 38, and a sixth output straight waveguide 39; the first input straight waveguide 8, the second input straight waveguide 9, the first coupling straight waveguide 10, the first output straight waveguide 15, the third input straight waveguide 16, the fourth input straight waveguide 17, the fourth coupling straight waveguide 18, the second output straight waveguide 23, and the third output straight waveguide 24 are sequentially connected from left to right to form a downlink straight waveguide; the second straight waveguide 25, the sixth coupling straight waveguide 26, the fourth output straight waveguide 27, the fifth input straight waveguide 28, the sixth input straight waveguide 29, the seventh coupling straight waveguide 30, and the third straight waveguide 31 are sequentially connected from right to left to form a middle straight waveguide; the fourth straight waveguide 37, the tenth coupling straight waveguide 35, the fifth output straight waveguide 38, and the sixth output straight waveguide 39 are sequentially connected from left to right to form an uplink straight waveguide; the second coupling straight waveguide 11, the first semicircular waveguide 12, the third coupling straight waveguide 14, and the second semicircular waveguide 13 are sequentially connected in a ring to form a reference ring (MRR F ) of the runway-type micro-ring resonator (MRR) structure; the fifth coupling straight waveguide 19, the third semicircular waveguide 20, the first straight waveguide 22, and the fourth semicircular waveguide 21 are sequentially connected in a ring to form a temperature sensing ring (MRR T ) of the runway-type micro-ring resonator (MRR) structure; the eighth coupling straight waveguide 32, the fifth semicircular waveguide 33, the ninth coupling straight waveguide 34, and the sixth semicircular waveguide 36 are sequentially connected in a ring to form a humidity sensing ring (MRR H ) of the runway-type micro-ring resonator (MRR) structure; the reference ring (MRR F ) and the temperature sensing ring (MRR T ) are located between the downlink straight waveguide and the middle straight waveguide, and the humidity sensing ring (MRR H ) is located between the middle straight waveguide and the uplink straight waveguide; in the direction of the sensor from left to right, the humidity sensing ring (MRRH ) is arranged in front of the reference ring (MRR F ) is arranged in front of the temperature sensing ring (MRR F ) is arranged in front of the temperature sensing ring (MRR T ); the first input straight waveguide 8 is an optical signal input port, the third output straight waveguide 24 is a temperature sensing output port, and the sixth output straight waveguide 39 is a humidity sensing output port; the downlink straight waveguide, the intermediate straight waveguide, the uplink straight waveguide, the second coupling straight waveguide 11, the third coupling straight waveguide 14, the fifth coupling straight waveguide 19, the first straight waveguide 22, the eighth coupling straight waveguide 32, and the ninth coupling straight waveguide 34 are arranged in parallel with each other, and the first coupling straight waveguide 10 and the second coupling straight waveguide 11, the fourth coupling straight waveguide 18 and the fifth coupling straight waveguide 19, the seventh coupling straight waveguide 30 and the eighth coupling straight waveguide 32, the third coupling straight waveguide 14 and the sixth coupling straight waveguide 26, and the ninth coupling straight waveguide 34 and the tenth coupling straight waveguide 35 respectively constitute a coupling structure; the polymer upper cladding layer 5 above the area where the humidity sensing ring is located is etched away to form a humidity sensing window 6 with a rectangular groove structure, the humidity sensing window 6 and the center of symmetry of the humidity sensing ring are arranged in coincidence, most of the fifth semicircular waveguide 33 and the sixth semicircular waveguide 36 are exposed in the humidity sensing window 6, while the eighth coupling straight waveguide 32 and the ninth coupling straight waveguide 34 and a small part of the fifth semicircular waveguide 33 and the sixth semicircular waveguide 36 connected thereto are not exposed; a temperature sensing window 7 is prepared on the polymer upper cladding layer 5 above the area where the temperature sensing ring is located, the temperature sensing window 7 is a combined structure of a middle rectangle and two identical semicircles at both ends, and the temperature sensing window 7 covers all the remaining waveguides in the temperature sensing ring except the fifth coupling straight waveguide 19 and a small part of the third semicircular waveguide 20 and the fourth semicircular waveguide 21 connected to the fifth coupling straight waveguide 19; the length direction edge of the humidity sensing window 6 is parallel to the intermediate straight waveguide, and the middle rectangle edge of the temperature sensing window 7 is parallel to the intermediate straight waveguide.

[0008] The width W1 of all waveguides in the polymer electrolyte core layer 4 is the same and is 0.5 μm to 10 μm; the length L1 of the first input straight waveguide 8 is 100 μm to 2000 μm; the length L2 of the second input straight waveguide 9, the first output straight waveguide 15, the fourth output straight waveguide 27, and the radius R1 of the first semicircular waveguide 12 and the second semicircular waveguide 13 are the same and are 100 μm to 500 μm; the length L3 of the first coupling straight waveguide 10, the second coupling straight waveguide 11, the third coupling straight waveguide 14, the fourth coupling straight waveguide 18, the fifth coupling straight waveguide 19, the sixth coupling straight waveguide 26, the seventh coupling straight waveguide 30, the eighth coupling straight waveguide 32, the ninth coupling straight waveguide 34, the tenth coupling straight waveguide 35, and the first straight waveguide 22 are the same and are 100 μm to 500 μm; the waveguide center coupling interval W2 between the first coupling straight waveguide 10 and the second coupling straight waveguide 11, the third coupling straight waveguide 14 and the sixth coupling straight waveguide 26, the fourth coupling straight waveguide 18 and the fifth coupling straight waveguide 19, the seventh coupling straight waveguide 30 and the eighth coupling straight waveguide 32, and the ninth coupling straight waveguide 34 and the tenth coupling straight waveguide 35 is the same and is 1 μm to 8 μm, and W2 > W1; the length L4 of the third input straight waveguide 16 is 100 μm to 1000 μm; the length L5 of the fourth input straight waveguide 17 and the second output straight waveguide 23 and the radius R2 of the third semicircular waveguide 20 and the fourth semicircular waveguide 21 are the same and are 100 μm to 500 μm; the length L6 of the third output straight waveguide 24 is 100 μm to 1000 μm; the length L7 of the second straight waveguide 25, the third straight waveguide 31, and the fourth straight waveguide 37 is the same and is 10 μm to 100 μm; the length L8 of the fifth input straight waveguide 28 is 50 μm to 500 μm; the length L9 of the sixth input straight waveguide 29 and the fifth output straight waveguide 38 and the radius R3 of the fifth semicircular waveguide 33 and the sixth semicircular waveguide 36 are the same and are 100 μm to 500 μm; and the length L 10 of the sixth output straight waveguide 39 is 850 μm to 5500 μm, and L 10 =L8+2×L2+2×L3+L4+2×L5+L6.

[0009] The (b) in the accompanying Figure 3 is a structure diagram of a humidity sensing window 6 and a temperature sensing window 7 of the temperature and humidity optical waveguide sensor; the width W3 of the humidity sensing ring (MRR H ) is 150 μm to 950 μm, and W3 < 2×R3; the length L 11 of the humidity sensing ring (MRR H ) is 350 μm to 1600 μm, and L 11 > 2×R3+L3; the width W4 of the middle rectangle of the temperature sensing window 7 is 10 μm to 950 μm, and 2×R2 > W4 > W1, W4 = 2×R4, the length L 12is 100μm~500μm, and L 12 =L3, the radius R4 of the two identical semicircles at both ends is the same, ranging from 200μm to 900μm, and 2×R2>R4>R2.

[0010] The substrate layer 1 of the present invention is made of any one of silicon, gallium arsenide, and indium phosphide; The polymer lower cladding layer 2, the polymer groove layer 3, and the polymer upper cladding layer 5 of the present invention are any one of a series of UV direct-write photoresist materials with good transparency, including fluorinated bisphenol A novolac resin (F-SU8), SU82002, SU82005, EpoCore, and EpoClad; The polymer electrolyte core layer 4 material of the present invention is a chlorine-containing electrolyte material PILs-Cl. The preparation method and experimental spectrum of the material are detailed in the reference: (Yunlong Yu, Zhiyan Ma, Xiaoya Miao, Yanyu Cui, Yaping Song, Sen Liu, Teng Fei, Tong Zhang. Humidity sensors based on cross-linked poly (ionic liquid)s for low humidity sensing. Sensors and Actuators B: Chemical. Volume 399, 2024, 134840, ISSN 0925-4005). First, the material has high transparency and low light absorption loss, and its refractive index is higher than that of the cladding material, which can ensure the effective transmission of optical signals. Secondly, it contains a positively charged polymer cross-linked network and negatively charged free ions Cl - , and free ion Cl - The concentration of will increase with the increase of ambient temperature and humidity. Finally, the refractive index of the material is adjustable, and its refractive index is related to the internal free ion Cl - The concentration of Figure 4 As shown in (a), the refractive index of the electrolyte material PILs-Cl decreases with increasing temperature, and its thermo-optical coefficient is approximately -9.3×10 -4 / ℃; the electrolyte material PILs-Cl can absorb water molecules in the air, such as Figure 4 As shown in (b), its refractive index decreases with increasing humidity, and the wet optical coefficient is about -3.1×10 -4 / %RH.

[0011] The humidity sensing window 6 described in the present invention is an air slot.

[0012] The temperature sensing window 7 of the present invention is an alloy composed of one or more of aluminum, gold, silver, copper and platinum with good thermal conductivity.

[0013] As attached Figure 5 The figure shows the working principle of a highly sensitive polymer micro-ring temperature and humidity optical waveguide sensor based on the vernier effect described in the present invention. The wide spectrum optical signal λ (wavelength range 1270~1360nm, power P range 0.2~2.0mW) input from the input end first enters the reference ring (MRR F ), and then enter the temperature sensing ring (MRR) through the transmission port and the downlink port respectively. T ) and humidity sensing ring (MRR H ). MRR T 、MRR H and MRR F The corresponding resonant wavelengths are λ T 、 λ H ,and λ F , and the corresponding free spectral regions are FSR T 、 FSR H and FSR F ,and FSR F > FSR T 、 FSR F > FSR H , MRR T and MRR H By connecting with MRR F Cascade to achieve the vernier effect. For the temperature sensing path, MRR T with MRR F The output spectrum is MRR T with MRR F The product of the output spectrum of T The i-th resonant wavelength λ T (i) With MRR F The jth resonant wavelength λ T (j) is the same as the output spectrum of the temperature sensor output port O1 at the resonance wavelength λ C The suppression trough at the wavelength is the deepest, and its depth depends on the overlap of the output spectra of the two rings at this wavelength. The suppression trough at other adjacent wavelengths becomes smaller, and finally an envelope band-stop spectrum is output (the spectrum is shown in the attached figure). Figure 7 In the temperature sensing process, when MRR TWhen the temperature of the temperature sensing window above changes, the free ions Cl in the electrolyte material PILs-Cl in this area - Changes in concentration cause changes in refractive index ΔN T , MRR T The resonant wavelength λ T Offset occurs Δλ T , MRR F The resonant wavelength λ F Unchanged, making MRR T The i'th resonant wavelength λ T (i') and MRR F The j'th resonant wavelength λ T (j') overlaps, and the output spectrum of the temperature sensor output port O1 is at the new resonance wavelength. λ' C The suppression trough is the deepest, and the entire spectrum is equivalent to the spectrum drift of the envelope band rejection type with the change of temperature. Δλ C =λ ' C -λ C , so the sensitivity of the temperature sensor S T for: ; Cursor magnification factor F T for: ; For MRR H with MRR F The output spectrum is MRR H with MRR F The product of the output spectrum of H The kth resonant wavelength λ H (k) and MRR F The first resonant wavelength λ H (l) When the humidity sensor output port O2 has the same output spectrum, the resonant wavelength λ C The peak value at the wavelength is the largest, and its peak value depends on the overlap of the output spectra of the two rings at this wavelength. The peak values ​​at other adjacent wavelengths become smaller, and finally an envelope bandpass spectrum is output (the spectrum is shown in the attached figure). Figure 8In the humidity sensing process, when the MRR H When the relative humidity of the air in the humidity sensing window changes, the electrolyte material PILs-Cl in this area absorbs water molecules in the air and free ions Cl - Changes in concentration cause changes in refractive index ΔN H , MRR H The resonant wavelength λ H Offset occurs Δλ H , MRR F The resonant wavelength λ F Unchanged, making MRR H The k'th resonant wavelength λ T (k') and MRR F The l'th resonant wavelength λ T (l') overlaps, and the output spectrum of the humidity sensor output port O2 is at the new resonance wavelength. λ' C The peak value is the largest, and the entire spectrum is equivalent to the spectrum of the envelope bandpass type drifting with the change of humidity. Δλ C =λ' C -λ C , so the sensitivity of the humidity sensor S H for: ; Cursor magnification factor F H for: ; In summary, when the temperature and humidity of the sensing window change, the envelope band-stop spectrum and envelope band-pass spectrum output by the corresponding detection port will drift. The change in temperature and humidity can be detected based on the drift amount, thereby realizing ultra-compact and ultra-sensitive on-chip dual-modal temperature and humidity sensing. This sensor is suitable for use in precision laboratories and metrological testing, storage and monitoring of specific items, biomedical research and cell / tissue culture, and other scenarios that require precise control of the environment or real-time monitoring of small changes. Its optical, miniaturized, and anti-interference properties further enhance its applicability in complex or micro systems. At the same time, the present invention contributes to the development of highly integrated, low-cost on-chip integrated optical sensors. Compared with existing device structures and preparation technologies, the present invention has the following beneficial effects: 1. The present invention is based on the vernier effect and uses a polymer waveguide structure to design MRR T and MRRH With the same MRR F Cascade. This structure significantly amplifies the tiny resonance drift of the micro-ring itself, thereby achieving high-resolution monitoring of subtle changes in temperature and humidity. At the same time, through precise design, FSR T 、 FSR H and FSR F The difference is small, ensuring that the sensor output spectrum forms a clear periodic envelope (such as the attached Figure 7 (a) and Figure 8 (a) in Figure 1). The peak position of this envelope exhibits continuous linear drift with temperature and humidity changes, facilitating continuous tracking of the temperature and humidity sensing spectrum. The device boasts a simple fabrication process, low cost, compact size, and high integration.

[0014] Second, compared to traditional electrical sensors, this invention utilizes an all-optical polymer waveguide sensing mechanism, avoiding electromagnetic interference. The electrolyte material, PILs-Cl, absorbs water molecules from the air, exhibiting humidity and temperature sensitivity. Combined with the evanescent field enhancement effect of the waveguide, this significantly improves the sensor's sensitivity and signal-to-noise ratio, while also providing excellent resistance to environmental interference.

[0015] Third, to address the drawbacks of existing optical sensors, which are mostly single-parameter sensors for temperature or humidity and suffer from cross-sensitivity to both temperature and humidity, the present invention innovatively designs a cascaded microring structure. The humidity sensing window is designed as an air slot structure, effectively blocking the heat conduction path and isolating the humidity sensing area from interference from temperature changes. The temperature sensing window is designed as a high-thermal-conductivity metal contact sheet covering the waveguide. On the one hand, it quickly and evenly transmits temperature change signals in the sensing area, and on the other hand, it isolates water molecules from penetrating, eliminating the influence of humidity on temperature measurement. This design achieves the first physical spatial decoupling of temperature and humidity signals on a monolithic polymer waveguide, ensuring independent measurement of the two parameters. At the same time, the spectral characteristics of the temperature and humidity sensor outputs are easily distinguishable (manifested as independent cursor envelopes), and the drift of their envelope peaks directly and linearly corresponds to the temperature and humidity changes. Parameter solution can be achieved by tracking the center wavelength of the envelope peak, eliminating the need for complex spectral fitting algorithms, significantly reducing the complexity of the system signal processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the three-dimensional structure of a highly sensitive polymer micro-ring temperature and humidity optical waveguide sensor based on the Vernier effect according to the present invention; Figure 2 for Figure 1 Schematic cross-section of some locations; Figure 3A high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on the Vernier effect, a polymer electrolyte core layer 4, a humidity sensing window 6, and a temperature sensing window 7 structure schematic diagram; Figure 4 The electrolyte material PILs-Cl refractive index and temperature and refractive index and relative temperature relationship curve of the high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor polymer electrolyte core layer 4 of the application; Figure 5 The working principle schematic diagram of the high-sensitivity polymer micro-ring temperature and humidity optical waveguide sensor of the application; Figure 6 The waveguide cross-section light field diagram of the device prepared in embodiment 1 of the application; Figure 7 The temperature sensing performance relationship curve of the device prepared in embodiment 1 of the application; Figure 8 The humidity sensing performance relationship curve of the device prepared in embodiment 1 of the application; Figure 9 The preparation process flow chart of the device in embodiment 1 of the application. DETAILED DESCRIPTION

[0017] The application will be described in greater detail below with reference to the drawings, it should be pointed out that the advantages and functions of the application will be understood more deeply by the person skilled in the art under the description, but the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by the person skilled in the art without creative labor belong to the protection scope of the application.

[0018] Figure 2 (a) in (a) is Figure 1 The cross-sectional schematic diagram at aa' position in (a); Figure 2 (b) in (b) is Figure 1 The cross-sectional schematic diagram at bb' position in (b); Figure 2 (c) in (c) is Figure 1 The cross-sectional schematic diagram at cc' position in (c); Figure 3 (a) in (a) is the structure schematic diagram of the polymer electrolyte core layer 4, Figure 3 (b) in (b) is the structure schematic diagram of the humidity sensing window 6 and the temperature sensing window 7; Figure 4 (a) in (a) is the relationship curve of the electrolyte material PILs-Cl refractive index and temperature, Figure 4 (b) in (b) is the relationship curve of the electrolyte material PILs-Cl refractive index and relative humidity; Figure 7 (a) in (a) is the drift condition diagram of the temperature sensing output port envelope band-stop type spectrum when the temperature sensing window temperature of the device in embodiment 1 changes; Figure 7 (b) in (b) isFigure 7 the wavelength corresponding to the deepest wave trough in (a) of FIG. 10 versus temperature; Figure 8 the shift of the envelope bandpass spectrum of the humidity sensing output port when the relative humidity of the humidity sensing window changes in (a) of FIG. 11; Figure 8 (b) of FIG. 11 is Figure 8 the wavelength corresponding to the deepest wave trough in (a) of FIG. 10 versus temperature;

[0019] Example 1: In this embodiment, the substrate layer 1 is a silicon substrate with a thickness H1 = 0.5 mm.

[0020] In this embodiment, the polymer lower cladding layer 2 is F-SU8 with a thickness H2 = 3 μm; the polymer groove layer 3 is F-SU8 with a thickness H3 = 2 μm; and the polymer upper cladding layer 5 is F-SU8 with a thickness H4 = 3 μm.

[0021] In this embodiment, the polymer electrolyte core layer 4 is a chlorine-containing polymer electrolyte material PILs-Cl with a refractive index sensitive to temperature and humidity. The light field mode transmitted in the polymer electrolyte core layer 4 is simulated by COMSOL Multiphysics software, as shown in FIG. 12. When the thickness H3 = 2 μm and the width W1 = 2 μm of the polymer electrolyte core layer 4, low-loss fundamental mode transmission can be achieved. Figure 6

[0022] ​The specific structural parameters of the polymer micro-ring temperature and humidity optical waveguide sensor based on the Vernier effect in this embodiment are as follows: the length L1 of the first input straight waveguide 8 is 500 μm; the length L2 of the second input straight waveguide 9, the first output straight waveguide 15, the fourth output straight waveguide 27, and the radius R1 of the first semicircular waveguide 12 and the second semicircular waveguide 13 are the same, 312.10 μm; the length L3 of the first coupling straight waveguide 10, the second coupling straight waveguide 11, the third coupling straight waveguide 14, the fourth coupling straight waveguide 18, the fifth coupling straight waveguide 19, the sixth coupling straight waveguide 26, the seventh coupling straight waveguide 30, the eighth coupling straight waveguide 32, the ninth coupling straight waveguide 34, the tenth coupling straight waveguide 35, and the first straight waveguide 22 is 300 μm; the coupling waveguide center spacing W2 between the first coupling straight waveguide 10 and the second coupling straight waveguide 11, the third coupling straight waveguide 14 and the sixth coupling straight waveguide 26, the fourth coupling straight waveguide 18 and the fifth coupling straight waveguide 19, the seventh coupling straight waveguide 30 and the eighth coupling straight waveguide 32, and the ninth coupling straight waveguide 34 and the tenth coupling straight waveguide 35 is 4.12 μm; the length L4 of the third input straight waveguide 16 is 200 μm; the length L5 of the fourth input straight waveguide 17 and the second output straight waveguide 23 and the radius R2 of the third semicircular waveguide 20 and the fourth semicircular waveguide 21 are the same, 310.35 μm; the length L6 of the third output straight waveguide 24 is 500 μm; the length L7 of the second straight waveguide 25, the third straight waveguide 31, and the fourth straight waveguide 37 is 20 μm; the length L8 of the fifth input straight waveguide 28 is 200 μm; the length L9 of the sixth input straight waveguide 29 and the fifth output straight waveguide 38 and the radius R3 of the fifth semicircular waveguide 33 and the sixth semicircular waveguide 36 are 311.94 μm; the length L 10 of the sixth output straight waveguide 39 is 2744.9 μm.

[0023] The humidity sensing window 6 in this embodiment has the same thickness H4, a width W3 of 600 μm, and a length L 11 of 1000 μm; the temperature sensing window 7 has a thickness H5 of 60 nm, a middle rectangular width W4 of 600 μm, and a length L 12 of 300 μm, and the radii R4 of the two semicircles are 300 μm.

[0024] The light signal wavelength λ range selected in this embodiment is 1270-1360 nm, and the light power P is 1 mW; the temperature T of the temperature sensing window changes in the range of 25.0-25.4 ℃; and the relative humidity of the humidity sensing window changes in the range of 52%-57% RH.

[0025] The device in this embodiment inputs a wide-spectrum light signal from the input signal end. When the temperature of the temperature sensing window changes, the output spectrum obtained at the temperature sensing output detection port is as shown in FIG. 6. As can be seen from FIG. 6, the output spectrum is a single peak, and the peak position changes with the temperature of the temperature sensing window. The peak position of the output spectrum is linearly related to the temperature of the temperature sensing window, and the linear relationship is as shown in FIG. 7. Figure 7As shown in (a), at the temperature T = 25.0 ° C, the temperature sensor output port obtains the envelope band-stop spectrum with the deepest suppression trough at the resonance wavelength of 1282.66 nm. As the temperature sensor window temperature increases, the T The gradually increasing of the envelope band-stop spectrum red-shifts, and the Figure 7 As shown in (b), the wavelength corresponding to the deepest trough of the envelope band-stop spectrum is linearly redshifted with temperature changes, and the relationship is: When the relative humidity of the air in the humidity sensor window changes, the output spectrum obtained at the humidity sensor output detection port is as shown in the attached figure. Figure 8 As shown in (a), when the relative humidity is 52%RH, the humidity sensor output port obtains an envelope bandpass spectrum with the maximum peak at the resonance wavelength of 1323.97nm. As the humidity in the humidity sensor window gradually increases, the envelope bandpass spectrum blue-shifts, and the attached Figure 8 As shown in (b), the wavelength corresponding to the highest peak of the envelope bandpass spectrum linearly blueshifts with humidity changes, as shown in the following relationship. In summary, when the temperature and humidity of the sensing window change, the envelope bandstop and envelope bandpass spectra output by the corresponding detection ports drift. The wavelength drift can be used to detect changes in temperature and humidity. This invention achieves ultra-compact and ultra-sensitive on-chip dual-mode temperature and humidity sensing, with sensitivities of 148.025 nm / °C and -8.504 nm / RH, respectively.

[0026] Example 2: The preparation steps of a polymer micro-ring temperature and humidity optical waveguide sensor based on the vernier effect in this embodiment are as shown in the attached figure. Figure 9 The specific description is as follows: (1) Cleaning the Si substrate 1: ultrasonically clean the Si substrate 1 with an acetone solution for 15 minutes; wipe the surface of the Si substrate four times in a single direction with an acetone-soaked cotton ball; repeat the above wiping process with an ethanol-soaked cotton ball to remove acetone residues; rinse with deionized water multiple times, and then dehydrate the surface with nitrogen purge technology; transfer the clean Si substrate 1 to a constant temperature oven for drying (temperature 120°C, time 30 minutes); finally, perform plasma surface treatment for 90 seconds; (2) Spin coating F-SU8 polymer lower cladding layer 2 and polymer groove layer 3: On the surface of the treated Si substrate 1, F-SU8 film was prepared by spin coating process, with a rotation speed of 2500r / min and a time of 30s; then pre-baking, the temperature / time is: 60℃ / 5min, 90℃ / 10min, 120℃ / 10min, to evaporate the organic solvent, and wait for it to naturally cool to room temperature; after cooling to room temperature, expose for 110s, and then carry out 60℃ / 5min, 90℃ / 10min, 120℃ / 10min. After post-baking for 10 min and waiting for natural cooling, an approximately 3 μm thick F-SU8 polymer lower cladding layer 2 was obtained, followed by plasma surface treatment for 90 s. A 3000 rpm, 30 s, spin-coating process was performed on the plasma-treated F-SU8 polymer lower cladding layer 2. Pre-baking was performed at 60°C / 5 min, 90°C / 10 min, and 120°C / 10 min to evaporate the organic solvent. The temperature was then allowed to cool naturally to room temperature, resulting in an approximately 2 μm thick F-SU8 polymer grooved layer 3. (3) Polymer groove layer 3 photolithography and development: the designed device structure (corresponding to the attached Figure 3 The photolithography mask (with the same structure as the prepared core layer structure) in (a) is covered on the negative F-SU8 polymer groove layer 3 of the polymer groove layer 3 and is in close contact with its surface. The non-grooved area is exposed to ultraviolet light with a wavelength of 365nm for 111s by a UV photolithography machine. After exposure, it is baked at a temperature / time of 120℃ / 10min, and then naturally cooled to room temperature; then wet etching is performed using the developer PGMEA to wet-etch the unexposed F-SU8 film to obtain a clearly visible groove morphology of the device core layer structure; then the developer on the surface is washed off with an isopropyl alcohol solution, and then the isopropyl alcohol solution on the surface is washed off with deionized water and blown dry with nitrogen; then the hard film is baked at a temperature / time of 120℃ / 10min, and then it is allowed to cool naturally to room temperature to complete the groove of the core layer structure of the polymer groove layer 3; (4) Spin coating to fill the polymer electrolyte core layer 4. IRE etching: Spin coat the electrolyte material PILs-Cl dissolved in methanol (the mass percentage of PILs-Cl material is 25%, the rotation speed is 2000r / min, and the time is 20s) on the entire device surface. Immediately after spin coating, expose to ultraviolet light (365nm, 0.12J / cm 2photocuring for 30 minutes, and the methanol solvent was volatilized to obtain the inverted-ridge electrolyte material coating, the ridge height in the groove and the depth of the groove were consistent, and were about 2 μm, and the thickness of the electrolyte material on the non-groove area of the polymer groove layer 3 was about 1 μm; then the IRE was used to etch the excess electrolyte material PILs-Cl (under the power of 200 W, mixed gas of O2:Ar2 with a volume ratio of 4:1 was introduced, and etching was performed for 4 min), and finally the waveguide structure containing the electrolyte material PILs-Cl only in the rectangular polymer groove layer 3 was obtained; (5) Spin coating F-SU8 polymer upper cladding layer 5: on the surface of the prepared waveguide structure, F-SU8 upper cladding layer was prepared by spin coating process, the rotation speed was 2500 r / min, and the time was 30 s; then pre-baking was performed with temperature / time of 60°C / 5 min, 90°C / 10 min and 120°C / 10 min, so that the organic solvent was volatilized, and then natural cooling to room temperature was waited for, to obtain an F-SU8 polymer upper cladding layer 5 with a thickness of about 3 μm; a designed humidity sensing window photoetching mask (with the same structure as the humidity sensing window structure) was covered on the polymer groove layer 3 negative F-SU8 film and closely contacted with the surface thereof, and the non-humidity sensing window area was exposed to ultraviolet light with a wavelength of 350-400 nm for 111 s by an ultraviolet photoetching machine; after the exposure, baking was performed with temperature / time of 120°C / 10 min, and then natural cooling to room temperature was performed; (6) Evaporation of aluminum film 6' and spin coating of BP212: a 60 nm thick aluminum metal film 6' was evaporated on the polymer upper cladding layer 5 without etching the humidity sensing window by vacuum evaporation process, and a positive BP-212 ultraviolet curing photoresist was spin coated on the aluminum film 6', the rotation speed was 2500 r / min, and the time was 20 s; then heating pre-baking was performed at 90°C for 20 min, and natural cooling to room temperature was performed; (7) Etching of temperature sensing window 7: a designed photoetching mask with the same structure as the temperature sensing window structure was covered on the surface of the positive BP-212 ultraviolet curing photoresist film, and 4 s exposure was performed by an ultraviolet photoetching machine with a wavelength of 365 nm; then development was performed with a 5% NaOH solution, the BP-212 film exposed in the non-temperature sensing window area was removed, heating post-baking was performed at 90°C for 15 min, and then natural cooling to room temperature was performed; then wet etching was performed on the sample with the 5% NaOH solution, and the aluminum film without the BP-212 film covering was removed, to obtain a clear temperature sensing window 7 shape; then the residual NaOH solution was washed away with deionized water, the deionized water was repeatedly washed clean and dried with nitrogen; then the BP-212 photoresist on the aluminum electrode 6 was washed away with ethanol, and finally the excess ethanol solution was washed away with deionized water and dried, to obtain the temperature sensing window 7; (8) Etching of humidity sensing window 6: using developer PGMEA for wet etching, the F-SU8 film in the humidity sensing window area which is not exposed in the step (5) is wet etched, to obtain the air slot topography of the humidity sensing window; then the developer on the surface is washed away with isopropyl alcohol solution, and the isopropyl alcohol solution on the surface is washed away with deionized water and dried with nitrogen; then the film is baked at a temperature / time of 120℃ / 10min, and then naturally cooled to room temperature, to obtain the humidity sensing window 6; finally, a polymer micro-ring temperature and humidity optical waveguide sensor based on vernier effect is obtained.

Claims

1. A high sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on Vernier effect, characterized in that: From bottom to top, it is composed of a substrate layer (1), a polymer lower cladding layer (2), a polymer groove layer (3), a polymer electrolyte core layer (4), and a polymer upper cladding layer (5). The polymer groove layer (3) and the polymer electrolyte core layer (4) are located between the polymer lower cladding layer (2) and the polymer upper cladding layer (5); the polymer electrolyte core layer (4) is a cascaded racetrack-type microring resonator planar optical waveguide structure, which is composed of a first input straight waveguide (8), a second input straight waveguide (9), a first coupling straight waveguide (10), a second coupling straight waveguide (11), a first semicircular waveguide (12), a third coupling straight waveguide (14), a second semicircular waveguide (13), a first output straight waveguide (15), a third input straight waveguide (16), a fourth input straight waveguide ( 17), the fourth coupled straight waveguide (18), the fifth coupled straight waveguide (19), the third semicircular waveguide (20), the first straight waveguide (22), the fourth semicircular waveguide (21), the second output straight waveguide (23), the third output straight waveguide (24), the second straight waveguide (25), the sixth coupled straight waveguide (26), the fourth output straight waveguide (27), the fifth input straight waveguide (28), the sixth input straight waveguide (29), the seventh coupled straight waveguide (30), the third straight waveguide (31), the eighth coupled straight waveguide (32), the fifth semicircular waveguide (33), the ninth coupled straight waveguide (34), the sixth semicircular waveguide (36), the fourth straight waveguide (37), the tenth coupled straight waveguide (35), the fifth output straight waveguide (38) and the sixth input straight waveguide (39). The first input straight waveguide (8), the second input straight waveguide (9), the first coupling straight waveguide (10), the first output straight waveguide (15), the third input straight waveguide (16), the fourth input straight waveguide (17), the fourth coupling straight waveguide (18), the second output straight waveguide (23), and the third output straight waveguide (24) are connected in sequence from left to right to form a downstream straight waveguide; the second straight waveguide (25), the sixth coupling straight waveguide (26), the fourth output straight waveguide (27), the fifth input straight waveguide (28), the sixth input straight waveguide (29), the seventh coupling straight waveguide (30), and the third straight waveguide (31) are connected in sequence from right to left to form an intermediate straight waveguide; the fourth straight waveguide (37), the tenth coupling straight waveguide (35 ), the fifth output straight waveguide (38), and the sixth output straight waveguide (39) are sequentially connected from left to right to form an uplink straight waveguide; the second coupled straight waveguide (11), the first semicircular waveguide (12), the third coupled straight waveguide (14), and the second semicircular waveguide (13) are sequentially connected in a ring shape to form a reference ring of a racetrack-type microring resonator structure; the fifth coupled straight waveguide (19), the third semicircular waveguide (20), the first straight waveguide (22), and the fourth semicircular waveguide (21) are sequentially connected in a ring shape to form a temperature sensing ring of a racetrack-type microring resonator structure; the eighth coupled straight waveguide (32), the fifth semicircular waveguide (33), the ninth coupled straight waveguide (34), and the sixth semicircular waveguide (36) are sequentially connected in a ring shape to form a humidity sensing ring of a racetrack-type microring resonator structure;The reference ring and the temperature sensing ring are located between the down straight waveguide and the middle straight waveguide, and the humidity sensing ring is located between the middle straight waveguide and the up straight waveguide; in the direction of the sensor from left to right, the humidity sensing ring is arranged in front of the reference ring, and the reference ring is arranged in front of the temperature sensing ring; the first input straight waveguide (8) is an optical signal input port, the third output straight waveguide (24) is a temperature sensing output port, and the sixth output straight waveguide (39) is a humidity sensing output port; the down straight waveguide, the middle straight waveguide, the up straight waveguide, the second coupling straight waveguide (11), the third coupling straight waveguide (14), the fifth coupling straight waveguide (19), the first straight waveguide (22), the eighth coupling straight waveguide (32) and the ninth coupling straight waveguide (34) are arranged in parallel with each other, the first coupling straight waveguide (10) and the second coupling straight waveguide (11), the fourth coupling straight waveguide (18) and the fifth coupling straight waveguide (19), the seventh coupling straight waveguide (30) and the eighth coupling straight waveguide (32), the third coupling straight waveguide (14) and the sixth coupling straight waveguide (26), and the ninth coupling straight waveguide (34) and the tenth coupling straight waveguide (35) respectively form a coupling structure; the polymer upper cladding layer (5) above the area where the humidity sensing ring is located is etched away to form a humidity sensing window (6) with a rectangular groove structure, the humidity sensing window (6) and the symmetry center of the humidity sensing ring are arranged in coincidence, most of the fifth semicircular waveguide (33) and the sixth semicircular waveguide (36) are exposed in the humidity sensing window (6), and the eighth coupling straight waveguide (32) and the ninth coupling straight waveguide (34) are not exposed; a temperature sensing window (7) is prepared above the polymer upper cladding layer (5) above the area where the temperature sensing ring is located, the temperature sensing window (7) is a combined structure of a middle rectangle and two same semicircles at both ends, the temperature sensing window (7) covers all the remaining waveguides except the fifth coupling straight waveguide (19) and a small part of the third semicircular waveguide (20) and the fourth semicircular waveguide (21) connected with the fifth coupling straight waveguide (19) in the temperature sensing ring; the length direction side of the humidity sensing window (6) is parallel to the middle straight waveguide, and the middle rectangle side of the temperature sensing window (7) is parallel to the middle straight waveguide.

2. A high sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on Vernier effect according to claim 1, characterized in that: The width W1 of all waveguides in the polymer electrolyte core layer (4) is the same and is 0.5 μm to 10 μm; the length L1 of the first input straight waveguide (8) is 100 μm to 2000 μm; the length L2 of the second input straight waveguide (9), the first output straight waveguide (15), the fourth output straight waveguide (27), and the radius R1 of the first semicircular waveguide (12) and the second semicircular waveguide (13) are the same and are 100 μm to 500 μm; the length L3 of the first coupling straight waveguide (10), the second coupling straight waveguide (11), the third coupling straight waveguide (14), the fourth coupling straight waveguide (18), the fifth coupling straight waveguide (19), the sixth coupling straight waveguide (26), the seventh coupling straight waveguide (30), the eighth coupling straight waveguide (32), the ninth coupling straight waveguide (34), the tenth coupling straight waveguide (35), and the first straight waveguide (22) are the same and are 100 μm to 500 μm; the waveguide center coupling interval W2 between the first coupling straight waveguide (10) and the second coupling straight waveguide (11), the third coupling straight waveguide (14) and the sixth coupling straight waveguide (26), the fourth coupling straight waveguide (18) and the fifth coupling straight waveguide (19), the seventh coupling straight waveguide (30) and the eighth coupling straight waveguide (32), the ninth coupling straight waveguide (34) and the tenth coupling straight waveguide (35) is the same and is 1 μm to 8 μm, and W2 > W1; the length L4 of the third input straight waveguide (16) is 100 μm to 1000 μm; the length L5 of the fourth input straight waveguide (17) and the second output straight waveguide (23) and the radius R2 of the third semicircular waveguide (20) and the fourth semicircular waveguide (21) are the same and are 100 μm to 500 μm; the length L6 of the third output straight waveguide (24) is 100 μm to 1000 μm; the length L7 of the second straight waveguide (25), the third straight waveguide (31), and the fourth straight waveguide (37) is the same and is 10 μm to 100 μm; the length L8 of the fifth input straight waveguide (28) is 50 μm to 500 μm; the length L9 of the sixth input straight waveguide (29) and the fifth output straight waveguide (38) and the radius R3 of the fifth semicircular waveguide (33) and the sixth semicircular waveguide (36) are the same and are 100 μm to 500 μm; the length L 10 of the sixth output straight waveguide (39) is 850 μm to 5500 μm, and L 10 =L8+2×L2+2×L3+L4+2×L5+L6; The width W3 of the humidity sensing ring is 150μm~950μm, and W3<2×R3; the length L of the humidity sensing ring 11 is 350μm~1600μm, and L 11 >2×R3+L3; the width W4 of the middle rectangle of the temperature sensing window (7) is 10μm~950μm, and 2×R2>W4>W1, W4=2×R4, the length L of the middle rectangle 12 is 100μm~500μm, and L 12 =L3, the radius R4 of the two identical semicircles at both ends is the same, ranging from 200μm to 900μm, and 2×R2>R4>R2.

3. A high sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on Vernier effect according to claim 1, characterized in that: The material of the substrate layer (1) is any one of silicon, gallium arsenide, indium phosphide; the material of the polymer lower cladding layer (2), the polymer etching groove layer (3) and the polymer upper cladding layer (5) is any one of fluorinated bisphenol A phenolic resin package, SU82002, SU82005, EpoCore, EpoClad; the polymer electrolyte core layer (4) is a chlorine-containing electrolyte material PILs-Cl; the material of the temperature sensing window (7) is an alloy composed of one or more of aluminum, gold, silver, copper and platinum.

4. The highly sensitive polymer micro-ring temperature and humidity optical waveguide sensor based on the Vernier effect according to claim 1, characterized in that: The thickness H1 of the substrate layer (1) is 0.2-1mm, the thickness H2 of the polymer lower cladding layer (2) is 2-20μm, the thickness H3 of the polymer etching groove layer (3) and the polymer electrolyte core layer (4) is the same and is 0.5-10μm, the thickness H4 of the polymer upper cladding layer (5) is 2-10μm, the thickness of the humidity sensing window (6) is the same as that of the polymer upper cladding layer (5), and the thickness H5 of the temperature sensing window (7) is 20-200nm.

5. A high sensitivity polymer micro-ring temperature and humidity optical waveguide sensor based on Vernier effect according to claim 1, characterized in that: The wavelength range of the input light signal λ in the first input straight waveguide (8) is 1270-1360nm, and the power P range is 0.2-2.0mW.

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