Sensing unit, sensing system and measuring method of enhanced mode resonant seawater temperature and salinity

Abstract

The application discloses a kind of sensitized mode resonant seawater temperature and salt sensing unit, sensing system and measurement method, sensing unit is sequentially from bottom to top substrate layer, temperature-sensitive layer and periodic arrangement nanometer cylinder, the material of substrate layer is quartz glass or sapphire, the material of temperature-sensitive layer requires that refractive index is greater than or equal to 2 in working wavelength range and the absolute value of thermo-optic coefficient is greater than or equal to 10 ‑6 / ℃, the material of nanometer cylinder is one of silicon, germanium, titanium dioxide.The sensing system includes wide-spectrum light source, transmission optical fiber, optical fiber isolator, optical fiber coupler, optical spectrometer, and sensing unit.The sensing unit and sensing system disclosed by the application can simultaneously realize sensing of seawater salinity and temperature, have good sensing effect and high sensitivity, and have good application potential in the field of ocean exploration.

Description

Technical Field

[0001] This invention relates to the field of micro-nano optoelectronic integrated optical device technology, and in particular to a sensitive guided mode resonant seawater temperature and salinity sensing unit, sensing system and measurement method. Background Technology

[0002] Common devices for measuring seawater temperature and salinity are primarily electrical. While electrical sensors are highly mature, they still suffer from drawbacks such as high cost, weak electromagnetic interference resistance, high watertightness requirements, high power consumption, large size, and deployment difficulties. Therefore, the development of optoelectronic devices has gradually become a hot topic. Optoelectronic devices are the cornerstone of modern information technology. With the rapid development of semiconductor micro-nano fabrication processes and information technology, higher demands are placed on optoelectronic devices in terms of miniaturization, high integration, multifunctionality, high speed, and low power consumption. However, the inherent limitations of traditional materials in optoelectronic performance restrict the development of optoelectronic devices. Firstly, most current optoelectronic devices are discrete devices, making optimized integration difficult. Secondly, the diffraction limit of light in a medium prevents it from being localized within the nanoscale, making device miniaturization a challenge. However, metasurface sensors can readily address these problems, even demonstrating absolute advantages, such as intrinsic insulation, strong electromagnetic interference resistance, lower watertightness requirements, pressure and corrosion resistance, small size, low power consumption, high sensitivity, and ease of integration and reuse.

[0003] Compared to traditional electrical sensors and general optical sensors, optical metasurface sensors offer significantly superior performance in terms of size, electromagnetic interference resistance, corrosion resistance, and large-scale monitoring. However, improvements are still needed in measurement accuracy and stability. Existing optical metasurfaces typically utilize guided-mode resonance for refractive index sensing, but they exhibit poor temperature sensing performance and low sensitivity, and suffer from cross-sensitivity to multiple parameters. According to research, no reports have been found regarding temperature-enhanced guided-mode resonance metasurface structures. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an enhanced-sensitivity guided-mode resonant seawater temperature and salinity sensing unit, a sensing system, and a measurement method to achieve synchronous and high-precision measurement of seawater temperature and salinity.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A sensitive guided-mode resonant seawater temperature and salinity sensing unit comprises, from bottom to top, a substrate layer, a temperature-sensitive layer, and periodically arranged nanocylinders. The substrate layer is made of quartz glass or sapphire, and the temperature-sensitive layer is required to have a refractive index greater than or equal to 2 and an absolute value of a thermo-optic coefficient greater than or equal to 10 within the operating wavelength range. -6 / ℃, the material of the nanocylinder is one of silicon, germanium, and titanium dioxide.

[0007] In the above scheme, the material of the temperature-sensitive layer is PLZT.

[0008] In the above scheme, the arrangement period P of the nanocylinders ranges from 300nm to 800nm, the diameter L of the nanocylinders ranges from 100nm to 400nm, and the height H1 of the nanocylinders ranges from 500nm to 1000nm.

[0009] Preferably, the arrangement period P of the nanocylinders is 450 nm, the diameter L of the nanocylinders is 375 nm, and the height H1 of the nanocylinders is 750 nm.

[0010] In the above scheme, the thickness H2 of the temperature-sensitive layer ranges from 250nm to 500nm.

[0011] Preferably, the thickness H2 of the temperature-sensitive layer is 375 nm.

[0012] A method for fabricating a sensitized guided-mode resonant seawater temperature and salinity sensing unit as described above includes the following steps: rinsing the substrate layer with ultrasound in an anhydrous ethanol environment; depositing a temperature-sensitive layer thin film on the substrate layer; depositing a high-refractive-index material for forming nanocylinders on the temperature-sensitive layer using low-pressure chemical vapor deposition; spin-coating photoresist onto the plane of the high-refractive-index material and allowing it to dry fully; depicting a circular periodic array shape using electron beam exposure; etching the high-refractive-index material using inductively coupled plasma; and finally removing the photoresist to obtain periodically arranged nanocylinders.

[0013] A hypersensitive guided-mode resonance seawater temperature and salinity sensing system includes a broadband light source, a transmission optical fiber, an optical fiber isolator, an optical fiber coupler, a spectrometer, and a sensing unit as described above. The broadband light source emits incident light which is transmitted through the transmission optical fiber, passes through the optical fiber isolator to the optical fiber coupler, and then enters the sensing unit normally. After being reflected by the sensing unit, the light passes through the optical fiber coupler and is received by the spectrometer.

[0014] In a further technical solution, when light is incident directly into the sensing unit, three resonances can be excited. The left resonance peak in the obtained spectrum is resonance peak one, the middle resonance peak is resonance peak two, and the right resonance peak is resonance peak three. Resonance peak one is excited by the nanocylinder alone, while resonance peaks two and three are excited by guided mode resonance.

[0015] A measurement method for a sensing system as described above includes the following steps:

[0016] Step 1: Calibrate the sensitivity of the sensing unit:

[0017] The sensing unit was placed in seawater at a known temperature, and spectrum one was obtained by measurement. The seawater temperature was adjusted and spectrum two was obtained by measurement again. The corresponding temperature sensitivity was calculated based on the temperature difference and the peak shift change of resonance peak three. The sensing unit was placed in seawater with a known salinity, and spectrum three was obtained by measurement. The seawater salinity was adjusted while keeping the temperature constant, and spectrum four was obtained by measurement again. The corresponding salinity sensitivity was calculated based on the salinity difference and the peak shift change of resonance peak one.

[0018] Step 2: Place the sensing unit in the seawater to be measured. When the temperature and salinity of the seawater change simultaneously, obtain the peak shifts of resonance peak one and resonance peak three based on the different spectral patterns before and after the temperature and salinity changes. Combined with the measured temperature sensitivity and salinity sensitivity, list the following matrix equation:

[0019]

[0020] Among them, S salt,1 S T,1 Δλ1 represents the salinity sensitivity, temperature sensitivity, and peak shift of resonance peak 1, respectively. salt,2 S T,2 Δλ2 represents the salinity sensitivity, temperature sensitivity, and peak shift of resonance peak three, respectively.

[0021] Solving the above matrix equations will yield the salinity change Δs and the temperature change ΔT.

[0022] Through the above technical solutions, the enhanced-sensitivity guided-mode resonant seawater temperature and salinity sensing unit, sensing system, and measurement method provided by the present invention have the following beneficial effects:

[0023] This invention adds a temperature-sensitive layer to the sensing unit. When incident light is perpendicularly incident on the nanoarray from the positive z-axis, it propagates in the temperature-sensitive layer and can excite guided mode resonance, thereby enhancing the electromagnetic field in the temperature-sensitive layer. This makes it very sensitive to changes in the environment. When the temperature changes, the spectral shift increases, thus achieving high-sensitivity temperature sensing.

[0024] This invention constructs a metasurface by rationally building a three-layer structure (upper cylindrical array, middle temperature-sensitive layer, and lower high-refractive-index substrate). Utilizing the flexible and tunable resonant characteristics of the sensing unit metasurface and the enhanced local field generated during resonant excitation, it achieves the sensing function of seawater temperature and salinity. On one hand, because the metamaterial's resonant response is designed as a narrowband resonance, it possesses higher spectral resolution. On the other hand, the enhanced local electromagnetic field couples with the seawater being measured, resulting in considerably high sensing sensitivity.

[0025] Existing metasurface structures designed using guided-mode resonance mostly focus on the sensitivity of guided-mode resonance to refractive index in order to obtain highly sensitive refractive index sensors. However, they suffer from poor temperature sensing performance and low sensitivity, and there are no reports of temperature-enhanced guided-mode resonance metasurfaces. This invention creatively adds a PLZT (lanthanum lead zirconate titanate ceramic) temperature-sensitive layer, allowing resonance to occur within this layer. This significantly improves the structure's temperature sensing performance and physically separates the temperature-sensitive region from the refractive index-sensitive region, effectively solving the cross-sensitivity problem that exists when measuring multiple parameters. Furthermore, the metamaterial's miniaturization capability, combined with a testing system, enables real-time, non-destructive, rapid, and portable sensing. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0027] Figure 1 This is a schematic diagram of a sensitive-enhanced guided-mode resonant seawater temperature and salinity sensing unit structure disclosed in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of a sensitive guided mode resonant seawater temperature and salinity sensing system disclosed in an embodiment of the present invention;

[0029] Figure 3 This is the electric field diagram when the sensing unit in this invention excites guided mode resonance.

[0030] Figure 4 This is a temperature sensing reflection diagram of the sensing unit in this invention.

[0031] Figure 5 This is a refractive index sensing reflection diagram of the sensing unit in this invention.

[0032] In the figure, 1 is the substrate layer; 2 is the temperature-sensitive layer; and 3 is the nanocylinder. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0034] This invention provides a sensitive guided-mode resonant seawater temperature and salinity sensing unit, such as... Figure 1 As shown, from bottom to top, the layers consist of a substrate, a thermosensitive layer, and periodically arranged nanocylinders. The substrate is made of quartz glass or sapphire, and the thermosensitive layer is required to have a refractive index greater than or equal to 2 and an absolute value of a thermo-optic coefficient greater than or equal to 10 within the operating wavelength range. -6 / ℃, in this embodiment, the material of the temperature-sensitive layer is PLZT (lead lanthanum zirconate titanate ceramic); the material of the nanocylinder is one of silicon, germanium, and titanium dioxide.

[0035] The arrangement period P of the nanocylinders ranges from 300nm to 800nm, the diameter L of the nanocylinders ranges from 100nm to 400nm, the height H1 of the nanocylinders ranges from 500nm to 1000nm, and the thickness H2 of the temperature-sensitive layer ranges from 250nm to 500nm.

[0036] In this embodiment, the arrangement period P of the nanocylinders is 450 nm, the diameter L of the nanocylinders is 375 nm, the height H1 of the nanocylinders is 750 nm, and the thickness H2 of the temperature-sensitive layer is 375 nm.

[0037] A method for fabricating a sensitive guided-mode resonant seawater temperature and salinity sensing unit includes the following steps:

[0038] The substrate was rinsed with ultrasound in an anhydrous ethanol environment, and a temperature-sensitive layer film was deposited on the substrate. A high-refractive-index material for forming nanocylinders was deposited on the temperature-sensitive layer using low-pressure chemical vapor deposition. Photoresist was spin-coated onto the plane of the high-refractive-index material and allowed to dry fully. The shape of a circular periodic array was depicted using electron beam exposure. The high-refractive-index material was etched using inductively coupled plasma. Finally, the photoresist was removed to obtain the periodically arranged nanocylinders.

[0039] This invention also discloses a sensitive guided-mode resonant seawater temperature and salinity sensing system, such as... Figure 2 As shown, the system includes a broadband light source, a transmission optical fiber, an optical fiber isolator, an optical fiber coupler, a spectrometer, and the aforementioned sensing unit. Incident light emitted from the broadband light source is transmitted through the transmission optical fiber, passes through the optical fiber isolator to the optical fiber coupler, and then enters the sensing unit normally. After being reflected by the sensing unit, it passes through the optical fiber coupler and is received by the spectrometer. The optical fiber isolator reduces the amount of reflected and scattered light reaching the broadband light source, minimizing damage to the device.

[0040] When light is incident directly into the sensing unit, three resonances can be excited. The electric field diagram at the resonance is as follows: Figure 3 As shown, from Figure 3 As can be seen, guided mode resonance is excited, and the electromagnetic field is concentrated in the temperature-sensitive layer 2. The electromagnetic field at the substrate layer 1 and the nanocylinder 3 is relatively weak. Therefore, the temperature-sensitive layer 2 is more sensitive to temperature changes and can realize high refractive index sensing of temperature.

[0041] The obtained spectrum shows that the left resonance peak is resonance peak one, the middle resonance peak is resonance peak two, and the right resonance peak is resonance peak three. Resonance peak one is excited by the nanocylinder alone and serves as the main resonance for refractive index sensing. Resonance peaks two and three are both excited by guided mode resonance and serve as the main resonance for temperature sensing.

[0042] A measurement method for a sensitive guided-mode resonant seawater temperature and salinity sensing system includes the following steps:

[0043] Step 1: Calibrate the sensitivity of the sensing unit:

[0044] The sensing unit was placed in seawater at 0°C, and spectrum one was obtained. Keeping the refractive index constant, the seawater temperature was adjusted to 100°C, and spectrum two was obtained again. Figure 4 As shown, it can be seen that the resonance peaks all exhibit a redshift as the ambient temperature increases. Resonance peaks two and three are the main resonances for temperature sensing. The peak wavelengths of resonance peak two are 1578.6 nm and 1588.85 nm at 0℃ and 100℃, respectively, while the peak wavelengths of resonance peak three are 1709.53 nm and 1725.07 nm at 0℃ and 100℃, respectively. Their sensitivities are 102.5 pm / ℃ and 155.4 pm / ℃, respectively, demonstrating excellent performance among similar temperature sensors. Therefore, resonance peak three, with its higher sensitivity, is selected for calculation. The corresponding temperature sensitivity is calculated based on the temperature difference and the peak shift change of resonance peak three.

[0045] The sensing unit was placed in seawater with a known salinity and a refractive index of 1.33, and spectrum three was obtained. The seawater salinity was adjusted, changing the refractive index to 1.34, and the temperature was kept constant, resulting in spectrum four. Figure 5 As shown, it can be seen that all three resonance peaks redshift with increasing surrounding refractive index. Resonance peak one, as the dominant resonance for refractive index sensing, has peak wavelengths of 1494.12 nm and 1497.25 nm at refractive indices of 1.33 and 1.34, respectively, with a sensitivity of 313 nm / RIU. This performance is excellent among similar refractive index sensors. Based on the salinity difference and the peak shift of resonance peak one, the corresponding salinity sensitivity was calculated.

[0046] Step 2: Place the sensing unit in the seawater to be measured. When the temperature and salinity of the seawater change simultaneously, obtain the peak shifts of resonance peak one and resonance peak three based on the different spectral patterns before and after the temperature and salinity changes. Combined with the measured temperature sensitivity and salinity sensitivity, list the following matrix equation:

[0047]

[0048] Among them, S salt,1 S T,1 Δλ1 represents the salinity sensitivity, temperature sensitivity, and peak shift of resonance peak 1, respectively. salt,2 S T,2 Δλ2 represents the salinity sensitivity, temperature sensitivity, and peak shift of resonance peak three, respectively.

[0049] Solving the above matrix equations will yield the salinity change Δs and the temperature change ΔT.

[0050] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A sensitive guided-mode resonant seawater temperature and salinity sensing system, characterized in that, It includes a broadband light source, a transmission optical fiber, an optical fiber isolator, an optical fiber coupler, a spectrometer, and a sensing unit. The broadband light source emits incident light that is transmitted through the transmission optical fiber, passes through the optical fiber isolator to the optical fiber coupler, and then enters the sensing unit normally. After being reflected by the sensing unit, it passes through the optical fiber coupler and is received by the spectrometer. The sensing unit consists of a substrate layer, a thermosensitive layer, and periodically arranged nanocylinders, from bottom to top. The substrate layer is made of quartz glass or sapphire, and the thermosensitive layer is required to have a refractive index greater than or equal to 2 and an absolute value of a thermo-optic coefficient greater than or equal to 10 within the operating wavelength range. -6 / ℃, the material of the nanocylinder is one of silicon, germanium, and titanium dioxide; The material of the temperature-sensitive layer is PLZT; When light is incident directly into the sensing unit, three resonances can be excited. The left resonance peak in the obtained spectrum is resonance peak one, the middle resonance peak is resonance peak two, and the right resonance peak is resonance peak three. Resonance peak one is excited by the nanocylinder alone, while resonance peaks two and three are excited by guided mode resonance.

2. The enhanced-sensitivity guided-mode resonant seawater temperature and salinity sensing system according to claim 1, characterized in that, The arrangement period P of the nanocylinders ranges from 300nm to 800nm, the diameter L of the nanocylinders ranges from 100nm to 400nm, and the height H1 of the nanocylinders ranges from 500nm to 1000nm.

3. The enhanced-sensitivity guided-mode resonant seawater temperature and salinity sensing system according to claim 2, characterized in that, The arrangement period P of the nanocylinders is 450 nm, the diameter L of the nanocylinders is 375 nm, and the height H1 of the nanocylinders is 750 nm.

4. The enhanced-sensitivity guided-mode resonant seawater temperature and salinity sensing system according to claim 1, characterized in that, The thickness H2 of the temperature-sensitive layer ranges from 250nm to 500nm.

5. The enhanced-sensitivity guided-mode resonant seawater temperature and salinity sensing system according to claim 4, characterized in that, The thickness H2 of the temperature-sensitive layer is 375 nm.

6. A method for preparing a sensitive guided-mode resonant seawater temperature and salinity sensing system as described in claim 1, characterized in that, The process includes the following steps: rinsing the substrate layer with ultrasound in an anhydrous ethanol environment; depositing a temperature-sensitive layer film on the substrate layer; depositing a high-refractive-index material for forming nanocylinders on the temperature-sensitive layer using low-pressure chemical vapor deposition; spin-coating photoresist onto the plane of the high-refractive-index material and allowing it to dry fully; using electron beam exposure to depict the shape of a circular periodic array; using inductively coupled plasma etching to etch the high-refractive-index material; and finally removing the photoresist to obtain the periodically arranged nanocylinders.

7. A measurement method for a sensing system as described in claim 1, characterized in that, Includes the following steps: Step 1: Calibrate the sensitivity of the sensing unit: The sensing unit was placed in seawater at a known temperature, and spectrum one was obtained by measurement. The seawater temperature was adjusted and spectrum two was obtained by measurement again. The corresponding temperature sensitivity was calculated based on the temperature difference and the peak shift change of resonance peak three. The sensing unit was placed in seawater with a known salinity, and spectrum three was obtained by measurement. The seawater salinity was adjusted while keeping the temperature constant, and spectrum four was obtained by measurement again. The corresponding salinity sensitivity was calculated based on the salinity difference and the peak shift change of resonance peak one. Step 2: Place the sensing unit in the seawater to be measured. When the temperature and salinity of the seawater change simultaneously, obtain the peak shifts of resonance peak one and resonance peak three based on the different spectral patterns before and after the temperature and salinity changes. Combined with the measured temperature sensitivity and salinity sensitivity, list the following matrix equation: ； Among them, S salt,1 S T,1 Δ 1 represents the salinity sensitivity, temperature sensitivity, and peak shift of resonance peak 1, respectively. salt,2 S T,2 Δ 2 represents the salinity sensitivity, temperature sensitivity, and peak shift of resonance peak 3, respectively; Solving the above matrix equations will yield the salinity change Δs and the temperature change ΔT.

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