Hollow cylindrical seawater temperature and salinity sensing unit, sensing system and measuring method

Abstract

The application discloses a hollow cylinder-based seawater temperature and salinity sensing unit, a sensing system and a measuring method, and the sensing unit comprises a substrate layer, and hollow cylinders are periodically arranged on the substrate layer; four identical hollow cylinders are arranged in each period, and the four hollow cylinders are arranged in a square array in a plane; the material of the substrate layer is quartz glass or sapphire, and the material of the hollow cylinders is one of silicon, germanium and titanium dioxide; the sensing system comprises a wide-spectrum light source, a transmission optical fiber, an optical fiber isolator, an optical fiber polarizer, an optical spectrometer, an optical fiber coupler and the sensing unit. The application can simultaneously realize sensing of seawater salinity and temperature, has the advantages of good sensing effect, high sensitivity and low cost, and has 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 seawater temperature and salinity sensing unit, sensing system and measurement method based on a hollow cylinder. Background Technology

[0002] To date, devices for measuring seawater temperature and salinity have primarily been electrical. While electrical sensors are currently quite mature, several key challenges remain in their application: high cost, weak electromagnetic interference resistance, poor pressure and corrosion resistance, high watertightness requirements, high power consumption, large size, and difficult deployment. At present, traditional electrical measurement devices no longer offer significant advantages, and continued research and development will inevitably face high costs and long development cycles. However, metasurface sensors can effectively address these issues, 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 electrical sensors, optical sensors offer 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. Furthermore, simultaneously measuring multiple parameters and addressing cross-sensitivity issues is a crucial technology requiring breakthroughs. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a seawater temperature and salinity sensing unit, sensing system, and measurement method based on a hollow cylinder, thereby achieving the goal of simultaneously and accurately measuring seawater temperature and salinity.

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

[0006] A seawater temperature and salinity sensing unit based on hollow cylinders includes a substrate layer on which hollow cylinders are periodically arranged, with four identical hollow cylinders in each period, and the four hollow cylinders are arranged in a square in a plane; the substrate layer is made of quartz glass or sapphire, and the hollow cylinders are made of one of silicon, germanium, and titanium dioxide.

[0007] In the above scheme, the arrangement period P of the hollow cylinders ranges from 600 to 1100 nm, the inner radius w of the hollow cylinders ranges from 25 to 110 nm, the outer radius L of the hollow cylinders ranges from 110 to 165 nm, the distance n between the adjacent outer walls of two hollow cylinders in each period ranges from 100 to 180 nm, and the height H of the hollow cylinders ranges from 500 to 1000 nm.

[0008] Preferably, the arrangement period of the hollow cylinders is P = 860 nm, the outer radius of the hollow cylinder is L = 135 nm, the inner radius of the hollow cylinder is w = 47.5 nm, the distance between the adjacent outer walls of two hollow cylinders in one period is n = 140 nm, and the height of the hollow cylinder is H = 750 nm.

[0009] In the above scheme, the distance N > n between the outer walls of the two hollow cylinders that are closest to each other between two adjacent cycles.

[0010] In the above scheme, the offset distance d between the inner circle center O2 and the outer circle center O1 of the hollow cylinder is in the range of 0 ≤ d < Lw.

[0011] Preferably, the offset distance d between the inner circle center O2 and the outer circle center O1 of the hollow cylinder is 25nm or 0nm.

[0012] A method for fabricating a seawater temperature and salinity sensing unit based on a hollow cylinder as described above includes the following steps: depositing a high refractive index material for forming the hollow cylinder on a substrate using low-pressure chemical vapor deposition; spin-coating photoresist onto the plane of the high refractive index material and allowing it to dry sufficiently; using electron beam exposure to depict a circular periodic array shape; using inductively coupled plasma etching to etch the high refractive index material; and finally removing the photoresist to obtain the periodically arranged hollow cylinders.

[0013] A seawater temperature and salinity sensing system based on a hollow cylinder includes a broadband light source, a transmission optical fiber, an optical fiber isolator, an optical fiber polarizer, a spectrometer, an optical fiber coupler, and a sensing unit as described in claim 1. The incident light emitted by the broadband light source passes through the optical fiber isolator and the optical fiber polarizer to reach the optical fiber coupler, and then enters the sensing unit normally. It enters the hollow cylinder from the substrate layer, is reflected by the hollow cylinder, passes through the optical fiber coupler, and is received by the spectrometer.

[0014] In the above scheme, when light is incident directly into the sensing unit, two resonances can be excited. The left resonance peak in the obtained spectrum is resonance peak one, and the right resonance peak is resonance peak two. The resonance spectrum can be shifted by adjusting the offset distance d between the inner circle center O2 and the outer circle center O1 of the hollow cylinder.

[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 two. The sensing unit was placed in seawater with a known salinity, and spectrum three was obtained by measurement. The seawater salinity was adjusted while the temperature was kept 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 two based on the different spectral patterns before and after the temperature and salinity changes. Combined with the measured temperature sensitivity and salinity sensitivity, the following matrix equation is established:

[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 2, 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 seawater temperature and salinity sensing unit, sensing system, and measurement method based on a hollow cylinder provided by the present invention have the following beneficial effects:

[0023] A metasurface is constructed by rationally building a two-layer structure (an upper hollow cylindrical array and a lower high-refractive-index substrate). The metasurface's flexible and tunable resonant characteristics, along with the enhanced local field generated during resonant excitation, enable seawater sensing. On one hand, the metamaterial's resonant response is designed as a narrowband resonance, resulting in higher spectral resolution. On the other hand, the enhanced local electromagnetic field couples with the seawater being measured, providing considerably high sensing sensitivity. Furthermore, the metamaterial's miniaturization, combined with the testing system, enables real-time, non-destructive, rapid, and portable sensing. Attached Figure Description

[0024] 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.

[0025] Figure 1 This is a schematic diagram of a seawater temperature and salinity sensing unit structure based on a hollow cylinder disclosed in an embodiment of the present invention;

[0026] Figure 2 This is a top view of the sensing unit in Embodiment 1;

[0027] Figure 3 This is a top view of the hollow cylinder in Example 1;

[0028] Figure 4 This is a top view of the sensing unit in Embodiment 2;

[0029] Figure 5 The electromagnetic field diagrams are for resonance one and resonance two, respectively.

[0030] Figure 6 The spectra are shown at different offset distances d.

[0031] Figure 7 This is a schematic diagram of a seawater temperature and salinity sensing system based on a hollow cylinder, as disclosed in an embodiment of the present invention.

[0032] Figure 8 This is a temperature sensing reflection diagram from Example 1;

[0033] Figure 9 This is a refractive index sensing reflection diagram of Example 1;

[0034] Figure 10 This is a refractive index sensing reflection diagram from Example 2;

[0035] Figure 11 This is a salinity sensor reflectance diagram from Example 2;

[0036] Figure 12 This is a temperature sensing reflection diagram from Example 2.

[0037] In the diagram, 1 is the substrate layer; 2 is the hollow cylinder. Detailed Implementation

[0038] 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.

[0039] This invention provides a seawater temperature and salinity sensing unit based on a hollow cylinder, such as... Figure 1 As shown, it includes a substrate layer 1, on which hollow cylinders 2 are periodically arranged. There are four identical hollow cylinders 2 in each period, and the four hollow cylinders 2 are arranged in a square in the plane.

[0040] The substrate 1 is made of quartz glass or sapphire, and the hollow cylinder 2 is made of one of silicon, germanium, or titanium dioxide.

[0041] like Figure 2 and Figure 4As shown, the arrangement period P of the hollow cylinders 2 ranges from 600 to 1100 nm, the inner radius w of the hollow cylinders 2 ranges from 25 to 110 nm, the outer radius L of the hollow cylinders 2 ranges from 110 to 165 nm, the distance n between the adjacent outer walls of two hollow cylinders 2 in each period ranges from 100 to 180 nm, and the height H of the hollow cylinders 2 ranges from 500 to 1000 nm.

[0042] The distance N > n between the outer walls of the two closest hollow cylinders 2 in two adjacent cycles. For example... Figure 3 As shown, the offset distance d between the inner circle center O2 and the outer circle center O1 of the hollow cylinder 2 ranges from 0 to d < Lw.

[0043] When light is incident directly into the sensing unit, two resonances can be excited: the resonance between the hollow cylindrical tetramers and the resonance of a single hollow cylinder, such as... Figure 5 As shown, the electromagnetic field of resonance one is mainly concentrated between two adjacent hollow cylinders within the period, while the electromagnetic field of resonance two is mainly concentrated on both sides of each hollow cylinder. In the resulting spectrum, the left resonance peak is resonance peak one, and the right resonance peak is resonance peak two; as shown... Figure 6 As shown, the resonance spectrum can be shifted by adjusting the offset distance d between the inner center O2 and the outer center O1 of the hollow cylinder. The two resonance wavelengths are related to the temperature and refractive index of the surrounding environment. When the temperature and refractive index change, the resonance wavelength changes. By monitoring the shift of the wavelength, the temperature and refractive index of the surrounding environment can be sensed.

[0044] A method for fabricating a seawater temperature and salinity sensing unit based on hollow cylinders includes the following steps: depositing a high refractive index material for forming hollow cylinders on a substrate 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 hollow cylinders.

[0045] like Figure 2 As shown, in Embodiment 1 of the present invention, the offset distance d between the inner circle center O2 and the outer circle center O1 of the hollow cylinder is 25nm, the arrangement period P is 860nm, the outer circle radius L of the hollow cylinder is 135nm, the inner circle radius w of the hollow cylinder is 47.5nm, the height of the hollow cylinder is H is 750nm, and the distance between the adjacent outer walls of the two hollow cylinders in one period is n is 140nm.

[0046] like Figure 4 As shown, in Embodiment 2 of the present invention, the offset distance d = 0 nm between the inner circle center O2 and the outer circle center O1 of the hollow cylinder is 0 nm. At this time, the centers of the inner and outer circles of the hollow cylinder coincide, and the other parameters are the same as in Embodiment 1.

[0047] A seawater temperature and salinity sensing system based on a hollow cylinder, such as Figure 7 As shown, it includes a broadband light source, a transmission optical fiber, an optical fiber isolator, an optical fiber polarizer, a spectrometer, an optical fiber coupler, and a sensing unit as in Embodiment 1 or Embodiment 2. The incident light emitted by the broadband light source passes through the optical fiber isolator and the optical fiber polarizer to reach the optical fiber coupler, and then enters the sensing unit normally. It enters the hollow cylinder from the substrate layer, is reflected by the hollow cylinder, passes through the optical fiber coupler, and is received by the spectrometer.

[0048] A measurement method for a sensing system using the sensing unit of Embodiment 1 includes the following steps:

[0049] Step 1: Calibrate the sensitivity of the sensing unit:

[0050] The sensing unit of Example 1 was placed in seawater at a temperature of 0°C, and spectrum one was obtained by measurement. Keeping the refractive index constant, the seawater temperature was adjusted to 100°C, and spectrum two was obtained by measurement again. Figure 8 As shown, both resonance peaks exhibit a redshift with increasing temperature. The peak wavelengths of resonance peak one are 1637.16 nm and 1640.82 nm at 0℃ and 100℃, respectively, while the peak wavelengths of resonance peak two are 1705.16 nm and 1706.40 nm at 0℃ and 100℃, respectively. Based on the temperature difference and the peak shift of resonance peak two, the corresponding temperature sensitivities are calculated to be 36 pm / ℃ and 12.4 pm / ℃, respectively.

[0051] The sensing unit of Example 1 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, the refractive index became 1.34, and the temperature was kept constant, resulting in spectrum four. Figure 9 As shown, both resonance peaks exhibit a redshift with increasing refractive index. The peak wavelengths of resonance peak one are 1639.15 nm and 1643.13 nm, respectively, while those of resonance peak two are 1705.16 nm and 1708.94 nm, respectively. Based on the salinity difference and the peak shift of resonance peak one, the corresponding salinity sensitivities are calculated to be 398 nm / RIU and 378 nm / RIU, respectively.

[0052] Step 2: Place the sensing unit of Example 1 into 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 two 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:

[0053]

[0054] 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 2, respectively.

[0055] Solving the above matrix equations will yield the salinity change Δs and the temperature change ΔT.

[0056] A measurement method for a sensing system using the sensing unit of Embodiment 2 includes the following steps:

[0057] Step 1: Calibrate the sensitivity of the sensing unit:

[0058] The sensing unit of Example 2 was placed in seawater, and while maintaining a constant refractive index, the seawater temperature was adjusted to 0°C, 10°C, 20°C, 30°C, 40°C, and 50°C, respectively, to obtain the corresponding spectra. Figure 10 As shown, both resonance peaks exhibit a redshift as temperature increases. The peak wavelengths of resonance peak one are 1310.21 nm, 1310.4 nm, 1310.59 nm, 1310.79 nm, 1310.96 nm, and 1311.16 nm, respectively. The peak wavelengths of resonance peak two are 1358.73 nm, 1359.03 nm, 1359.33 nm, 1359.63 nm, 1359.93 nm, and 1360.23 nm, respectively. The sensitivities are 19 pm / ℃ and 30 pm / ℃, respectively, demonstrating excellent performance among similar temperature sensors.

[0059] By placing the sensing unit of Example 2 in seawater and keeping the temperature constant, and changing the refractive index of the surrounding environment to 1.33, 1.34, 1.35, and 1.36, corresponding spectra can be obtained. Figure 11 As shown, it can be seen that both resonance peaks redshift with the increase of the surrounding refractive index. The peak wavelengths of resonance peak one are 1310.44nm, 1314.99nm, 1319.68nm, and 1324.39nm, respectively, and the peak wavelengths of resonance peak two are 1359.33nm, 1364.67nm, 1370.06nm, and 1375.50nm, respectively. The sensitivities are 464nm / RIU and 540nm / RIU, respectively, which are excellent performances among similar refractive index sensors.

[0060] When other conditions remain unchanged, changes in the refractive index of seawater can directly reflect changes in its salinity, thus enabling the sensing of seawater salinity.

[0061] The sensing unit of Example 2 was placed in seawater, and while maintaining a constant temperature, the salinity of the seawater was adjusted to 0‰, 30‰, 32‰, 34‰, 36‰, 38‰, and 40‰, respectively, to obtain the corresponding spectra. Figure 12 As shown, it can be seen that both resonance peaks exhibit a redshift with increasing surrounding refractive index. The peak wavelengths of resonance peak one are 1311.77 nm, 1314.33 nm, 1314.51 nm, 1314.69 nm, 1314.85 nm, 1315.00 nm, and 1315.18 nm, respectively, while the peak wavelengths of resonance peak two are 1360.93 nm, 1363.87 nm, 1364.06 nm, 1364.25 nm, 1364.45 nm, 1364.64 nm, and 1364.84 nm, respectively. The sensitivities are 0.0839 nm / ‰ and 0.0978 nm / ‰, respectively.

[0062] Step 2: Place the sensing unit of Example 2 into 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 two 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:

[0063]

[0064] 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 2, respectively.

[0065] Solving the above matrix equations will yield the salinity change Δs and the temperature change ΔT.

[0066] 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 seawater temperature and salinity sensing system based on a hollow cylinder, characterized in that, It includes a broadband light source, transmission optical fiber, optical fiber isolator, optical fiber polarizer, spectrometer, optical fiber coupler, and sensing unit. The incident light emitted by the broadband light source passes through the optical fiber isolator and optical fiber polarizer to reach the optical fiber coupler, and then enters the sensing unit normally. It enters the hollow cylinder from the substrate layer, is reflected by the hollow cylinder, and then passes through the optical fiber coupler to be received by the spectrometer. The sensing unit includes a substrate layer on which hollow cylinders are periodically arranged. There are four identical hollow cylinders in each period, and the four hollow cylinders are arranged in a square in a plane. The substrate layer is made of quartz glass or sapphire, and the hollow cylinders are made of one of silicon, germanium, or titanium dioxide. When light is incident directly into the sensing unit, two resonances can be excited. The left resonance peak in the resulting spectrum is resonance peak one, and the right resonance peak is resonance peak two. The resonance spectrum can be shifted by adjusting the offset distance d between the inner circle center O2 and the outer circle center O1 of the hollow cylinder.

2. The seawater temperature and salinity sensing system based on a hollow cylinder according to claim 1, characterized in that, The arrangement period P of the hollow cylinders ranges from 600 to 1100 nm, the inner radius w of the hollow cylinders ranges from 25 to 110 nm, the outer radius L of the hollow cylinders ranges from 110 to 165 nm, the distance n between the adjacent outer walls of two hollow cylinders in each period ranges from 100 to 180 nm, and the height H of the hollow cylinders ranges from 500 to 1000 nm.

3. The seawater temperature and salinity sensing system based on a hollow cylinder according to claim 2, characterized in that, The hollow cylinders have an arrangement period P = 860 nm, an outer radius L = 135 nm, an inner radius w = 47.5 nm, a distance n = 140 nm between adjacent outer walls of two hollow cylinders in one period, and a height H = 750 nm.

4. A seawater temperature and salinity sensing system based on a hollow cylinder according to claim 2, characterized in that, The distance N > n between the outer walls of the two nearest hollow cylinders between two adjacent cycles.

5. A seawater temperature and salinity sensing system based on a hollow cylinder according to claim 2, characterized in that, The offset distance d between the inner center O2 and the outer center O1 of the hollow cylinder is in the range of 0 ≤ d < Lw.

6. A seawater temperature and salinity sensing system based on a hollow cylinder according to claim 5, characterized in that, The offset distance between the inner circle center O2 and the outer circle center O1 of the hollow cylinder is d = 25nm or 0nm.

7. A method for preparing a seawater temperature and salinity sensing system based on a hollow cylinder as described in claim 1, characterized in that, The process includes the following steps: depositing a high-refractive-index material for forming hollow cylinders onto a substrate using low-pressure chemical vapor deposition; spin-coating photoresist onto the plane of the high-refractive-index material and allowing it to dry thoroughly; 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 hollow cylinders.

8. 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 two. The sensing unit was placed in seawater with a known salinity, and spectrum three was obtained by measurement. The seawater salinity was adjusted while the temperature was kept 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 two based on the different spectral patterns before and after the temperature and salinity changes. Combined with the measured temperature sensitivity and salinity sensitivity, the following matrix equation is established: ； 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 2, respectively; Solving the above matrix equations will yield the salinity change Δs and the temperature change ΔT.

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