Soil nitrogen photon chip sensor and detection method thereof

Abstract

The invention relates to the technical field of molecular detection, in particular to a soil nitrogen photon chip sensor and a detection method thereof. The device comprises a laser, a photon chip and two detectors, the photon chip is provided with two light interference structures, and light of the laser enters the photon chip and is divided into two paths to enter the two light interference structures; the light is divided into two parallel light in the light interference structure, and one light passes through the ion selection area; the light passing through the ion selection region in the light interference structure and the other path of light interfere with each other; the ion selection areas in the two light interference structures are respectively used for screening nitrate nitrogen ions and ammonium nitrogen ions, and the two corresponding detectors are respectively used for analyzing the concentration of the nitrate nitrogen ions and the concentration of the ammonium nitrogen ions in the solution to be detected based on the acquired spectrum. According to the method, the detection accuracy is greatly improved, and the defects that in the prior art, nitrate nitrogen and ammonium nitrogen detection time is long, operation is complex, cost is high, and field detection is difficult to achieve are overcome.

Description

Technical Field

[0001] The present invention relates to the field of molecular detection technology, and in particular to a soil nitrogen photon chip sensor and a detection method thereof. Background Art

[0002] Nitrate and ammonium are the most readily absorbed inorganic nitrogen forms by plants. They are limiting factors for crop yield and are therefore considered the primary components of nitrogen fertilizers. Nitrate is a stable, mobile anion that is easily transported in the soil, while ammonium is a positively charged ion that is easily adsorbed. Excessive use of nitrogen fertilizers can cause groundwater contamination. Therefore, monitoring soil nitrogen (nitrate and ammonium) is key to preventing water pollution. Traditional chemical soil nitrogen analysis methods are complex, time-consuming, and lack real-time performance, as well as being costly and difficult to apply on a large scale. There is an urgent need for in situ, rapid, and robust soil nitrogen sensing technologies.

[0003] Currently, compact sensing methods for soil nitrogen detection can be divided into two categories: potentiometric and optical. Potentiometric methods such as ion-selective electrodes and ion-selective field-effect transistors cannot avoid the inherent potential drift of the reference electrode, and the need for frequent calibration can hinder their practical application, particularly in soil sensing. In contrast, optical sensing methods for nitrogen detection have minimal electrical interference and can eliminate baseline shifts. Spectrophotometric methods for nitrate / nitrite determination have been well studied, including UV-visible spectroscopy, fluorescence, and chemiluminescence. However, these techniques require complex sample pretreatment, such as assay protocols involving redox reactions, which is not conducive to on-site, in situ nitrogen determination. Fourier transform infrared spectroscopy and Raman spectroscopy are also used for nitrogen detection. Although these methods can provide excellent sensitivity, the requirement for complex and expensive instrumentation has reduced interest in these techniques outside the laboratory. Summary of the Invention

[0004] In order to overcome the defects of the above-mentioned prior art in nitrogen detection, such as long cycle, complex operation, high cost and difficulty in on-site detection, the present invention proposes a soil nitrogen photonic chip sensor with enhanced ion selectivity, which greatly improves detection accuracy while ensuring high sensitivity and real-time detection.

[0005] The present invention proposes a soil nitrogen photonic chip sensor comprising a laser, a photonic chip, and two detectors. The photonic chip is provided with two optical interference structures. Laser light enters the photonic chip and is split into two paths that enter the two optical interference structures. The two detectors correspond to the two optical interference structures. The light is split into two parallel paths in the optical interference structures. One path passes through an ion-selective region and is coupled into the detector, while the other path is directly coupled into the detector. The light passing through the ion selection area in the optical interference structure interferes with another light beam, and the detector detects the concentration of the selected ions in the ion selection area through spectral analysis; the ion selection areas in the two optical interference structures are used to screen nitrate nitrogen ions and ammonium nitrogen ions, respectively, and the corresponding two detectors analyze the nitrate nitrogen ion concentration and ammonium nitrogen ion concentration in the test solution based on the acquired spectra.

[0006] Preferably, the optical interference structure includes an MZI and a front-end coupling grating and a rear-end coupling grating arranged at both ends of the MZI; the light from the laser enters the MZI through the front-end coupling grating and is split into two, and the two light paths pass through the sensing arm and reference arm of the MZI respectively and enter the rear-end coupling grating, and enter the corresponding detector through the rear-end coupling grating; the sensing arm passes through the ion selection area.

[0007] Preferably, it further comprises a nitrate nitrogen ion selection material and an ammonium nitrogen ion selection material, which are respectively arranged on the sensing arm of the first light interference structure and the sensing arm of the second light interference structure, and form an ion selection region communicating with the outside; The nitrate nitrogen ion selective material is composed of tridodecylmethylammonium nitrate dispersed in a plasticized PVC polymer matrix, and the concentration of the nitrate ion carrier is 6.1%; the ammonium nitrogen ion selective material is prepared from a calixarene material.

[0008] Preferably, the photonic chip also includes a substrate and a shell; the shell cooperates with the substrate to encapsulate the optical interference structure, and the shell is provided with a detection window for adding the solution to be tested; the nitrate nitrogen ions and ammonium nitrogen ions in the solution to be tested are respectively attached to the corresponding sensor arms through the nitrate nitrogen ion selective material and the ammonium nitrogen ion selective material.

[0009] Preferably, the nitrate nitrogen ion selective material and the ammonium nitrogen ion selective material are respectively coated on corresponding sensing arms.

[0010] Preferably, the laser is a distributed tunable laser.

[0011] Preferably, the detector is a silicon detector.

[0012] The present invention proposes a method for manufacturing a soil nitrogen photonic chip sensor: first, a photonic chip is manufactured, and then a laser and a detector are respectively arranged at both ends of the photonic chip; the manufacturing of the photonic chip includes the following steps: Spin-coat photoresist on the cleaned substrate, use electron beam exposure to irradiate the waveguide area, and after development and fixing, etch out the strip waveguide. After stripping, two MZIs are formed. Nitrate nitrogen ion selective material and ammonium nitrogen ion selective material are respectively provided on the sensing arms of the two MZIs; Grating areas are selected at both ends of each MZI on the substrate and photoresist is spin-coated. The grating areas are irradiated by electron beam exposure. After development and fixing, strip waveguides are etched out. After stripping, the front-end coupling grating and the rear-end coupling grating at both ends of the MZI are formed. A shell is provided to encapsulate the MZI structure, and a detection window is provided on the shell.

[0013] The present invention proposes a soil nitrogen detection method. First, deionized water is placed in the detection window, the laser is in a scanning state, and the two detectors respectively obtain the resonance wavelength of the nitrate nitrogen sensor arm. and the resonance wavelength of the ammonium nitrogen sensing arm ; The nitrate nitrogen sensing arm is a sensing arm of a material that selects nitrate nitrogen ions, and the ammonium nitrogen sensing arm is a sensing arm of a material that selects ammonium nitrogen ions; Place the solution to be tested in the detection window and put the laser into scanning state. The two detectors obtain the resonance wavelength of the nitrate nitrogen sensor arm respectively. and the resonance wavelength of the ammonium nitrogen sensing arm ; Resonance shift of nitrate ion Calculate the concentration of nitrate nitrogen ions by the resonance shift of ammonium nitrogen ions Calculate the concentration of ammonium nitrogen ions.

[0014] Preferably, the nitrate nitrogen ion concentration and ammonium nitrogen ion concentration The calculation formula is: ; ; Among them, a and b are nitrate nitrogen parameters, and c and d are ammonium nitrogen parameters; a, b, c, and d are obtained by fitting the known data set.

[0015] The advantages of the present invention are: (1) The soil nitrogen photonic chip sensor proposed in the present invention adopts an optical interference structure and combines spectral analysis technology to detect ion concentrations through the phase difference changes of two optical signals. Its sensitivity is significantly higher than that of traditional electrochemical methods. The direct coupling design of the laser and the detector can realize rapid real-time monitoring of soil nitrogen. In addition, two optical interference structures are set on the photonic chip of the present invention. The two optical interference structures are equipped with independent detectors. The simultaneous detection of nitrate nitrogen ion concentration and ammonium nitrogen ion concentration can be achieved through a single photonic chip, thereby quickly obtaining the concentration of common nitrogen-containing ions in the soil, effectively avoiding the presence of other ions in the soil (such as K, Na, Cl). - ) interference, greatly improving the detection accuracy.

[0016] (2) The MZI in this invention is integrated into a photonic chip and combined with grating coupling technology to significantly reduce the size of the sensor, making it easier to integrate and portable, thus achieving a compact photonic chip structure. Different ion-selective materials are set separately to distinguish and quantify the different forms of nitrogen in the soil, adapting to the needs of complex soil environments.

[0017] (3) In the present invention, the substrate and housing encapsulate and protect the core components of the photonic chip (MZI, grating), preventing the intrusion of soil particles or moisture, extending the sensor life, and ensuring the long-term stability of the sensor. The detection window is directly exposed to the solution to be tested, combined with the optimized position of the ion-selective material (window or sensing arm), ensuring efficient ion penetration and attachment to the sensing surface, shortening the response time.

[0018] (4) The present invention uses electron beam lithography and etching to prepare waveguides and gratings. This process is compatible with semiconductor mass production, which helps reduce manufacturing costs. The ion-selective material is directly integrated into the sensor arm or window, which helps avoid complex packaging steps and improves product yield.

[0019] (5) Distributed tunable lasers support wavelength scanning, adapting to the absorption spectrum requirements of different ion-selective materials and expanding the detection range. Silicon detectors have fast response, low cost, high compatibility with photonic chip materials (such as SOI), and excellent system integration.

[0020] (6) The soil nitrogen detection method proposed in this invention involves dropping the test solution directly into the detection window, eliminating the need for complex pretreatment and simplifying the operation steps, thus facilitating a fast and convenient on-site detection process. Spectral analysis combined with chemical formula conversion directly outputs nitrogen concentration, reducing reliance on specialized instruments and making it suitable for on-site use.

[0021] (7) The soil nitrogen detection method and sensor proposed in the present invention are applicable to various environments such as farmland and greenhouses, meet the needs of precision agricultural nitrogen fertilizer management, and have multi-scenario applicability; they are also environmentally friendly, do not require chemical reagents, and avoid secondary pollution; the combination of photonic chips and semiconductor technology takes into account both high performance and low cost, which is conducive to promoting large-scale applications.

[0022] (8) This invention has achieved significant breakthroughs in the sensitivity, selectivity, integration and practicality of soil nitrogen photonic chip sensors, providing an innovative solution for soil nitrogen monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the three-dimensional structure diagram of the soil nitrogen photonic chip sensor; Figure 2 This is the MZI process flow chart; Figure 3 Show for MZI; Figure 4The connection diagram of MZI and coupling grating; Figure 5 It is a coupled grating structure; Figure 6 Detailed display of coupled grating; Figure 7 This is a flow chart of the soil nitrogen detection method; Illustration: 1-1, first front-end coupling grating; 1-2, second front-end coupling grating; 2-1, first rear-end coupling grating; 2-2, second rear-end coupling grating; 3-1, first sensing arm; 3-2, second sensing arm; 4-1, first reference arm; 4-2, second reference arm; 5, housing; 50, detection window; 6, substrate; 7-1, nitrate nitrogen ion selection material; 7-2, ammonium nitrogen ion selection material; 8-1, first detector; 8-2, second detector; 9-1, first optical fiber; 9-2, second optical fiber; 9-3, third optical fiber; 10, laser. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] like Figure 1 、 Figure 4 As shown, this embodiment proposes a soil nitrogen photonic chip sensor, comprising: a laser 10, a photonic chip, a first detector 8-1, and a second detector 8-2. The photonic chip includes two identical optical interference structures, comprising a front-end coupling grating, a back-end coupling grating, and a Mach-Zehnder interferometer (MZI). The first detector 8-1 and the second detector 8-2 correspond to the two optical interference structures, respectively.

[0026] The front-end coupling grating and the rear-end coupling grating of one optical interference structure are respectively recorded as the first front-end coupling grating 1-1 and the first rear-end coupling grating 2-1, and the front-end coupling grating and the rear-end coupling grating of the other optical interference structure are respectively recorded as the second front-end coupling grating 1-2 and the second rear-end coupling grating 2-2.

[0027] The laser 10 is connected to the first front-end coupling grating 1-1 and the second front-end coupling grating 1-2 through the first optical fiber 9-1, the first rear-end coupling grating 2-1 is connected to the first detector 8-1 through the second optical fiber 9-2, and the second rear-end coupling grating 2-2 is connected to the second detector 8-2 through the third optical fiber 9-3.

[0028] The laser 10 is used as a light source and can be a distributed tunable laser with a central wavelength of 765 nm and a tunable range of 3 nm. The detector can be a silicon detector.

[0029] During operation, light from the laser 10 is split into two paths corresponding to the two optical interference structures through the first optical fiber 9-1. One path of light passes through the first front-end coupling grating 1-1 and enters the MZI of the first optical interference structure. The light is split into two paths of parallel light in the MZI, and then passes through the first rear-end coupling grating 2-1 and enters the first detector 8-1. The other path of light output from the first optical fiber 9-1 passes through the second front-end coupling grating 1-2 and enters the MZI of the second optical interference structure. The light is split into two paths of parallel light in the MZI, and then passes through the second rear-end coupling grating 2-2 and enters the second detector 8-2.

[0030] The first optical fiber 9 - 1 is a Y-type optical fiber, which is convenient for splitting the light output from the laser 10 into two and respectively entering the two optical interference structures.

[0031] Reference Figure 2 、 Figure 3 The MZI of the first optical interference structure includes a first incident arm, a first sensing arm 3-1, a first reference arm 4-1, and a first output arm; the first incident arm, the first sensing arm 3-1, the first reference arm 4-1, and the first output arm are arranged between the first front coupling grating 1-1 and the first rear coupling grating 2-1. The MZI of the second optical interference structure includes a second incident arm, a second sensing arm 3-2, a second reference arm 4-2, and a second output arm; the second incident arm, the second sensing arm 3-2, the second reference arm 4-2, and the second output arm are arranged between the second front coupling grating 1-2 and the second rear coupling grating 2-2.

[0032] In the first optical interference structure, the first sensing arm 3-1 and the first reference arm 4-1 are arranged vertically. The first input arm is located to the left of the first sensing arm 3-1 and the first reference arm 4-1 and connected between them, forming a Y-shaped structure. The first output arm is located to the right of the first sensing arm 3-1 and the first reference arm 4-1 and connected between them, forming a Y-shaped structure. The first front-end coupling grating 1-1 is located to the left of the first input arm, and the first rear-end coupling grating 2-1 is located to the right of the first output arm.

[0033] In the second optical interference structure, the second sensing arm 3-2 and the second reference arm 4-2 are arranged vertically. The second input arm is located to the left of the second sensing arm 3-2 and the second reference arm 4-2 and connected between them, forming a Y-shaped structure. The second output arm is located to the right of the second sensing arm 3-2 and the second reference arm 4-2 and connected between them, forming a Y-shaped structure. The second front-end coupling grating 1-2 is located to the left of the second input arm, and the second rear-end coupling grating 2-2 is located to the right of the second output arm.

[0034] That is, in the optical interference structure, the incident arm and the output arm are both Y-shaped structures, the three ends of the incident arm are respectively connected to the corresponding front-end coupling grating, sensor arm and reference arm, and the three ends of the output arm are respectively connected to the corresponding rear-end coupling grating, sensor arm and reference arm.

[0035] Laser light is split into two paths through first optical fiber 9-1. One path is coupled to the first input arm via first front-end coupling grating 1-1. It then splits into two paths, passing through first sensing arm 3-1 and first reference arm 4-1, before passing through the first output arm and entering first rear-end coupling grating 2-1. The first rear-end coupling grating 2-1 directs the coupled light into the corresponding first detector 8-1 for spectral analysis. Nitrate-selective material 7-1 is provided on first sensing arm 3-1.

[0036] The other path of light split off from the laser via the first optical fiber 9-1 is coupled to the second input arm via the second front-end coupling grating 1-2. The light then splits into two paths, passing through the second sensing arm 3-2 and the second reference arm 4-2, before passing through the second output arm and entering the second rear-end coupling grating 2-2. The second rear-end coupling grating 2-2 directs the coupled light into the corresponding second detector 8-2 for spectral analysis. The second sensing arm 3-2 is provided with an ammonium nitrogen ion selective material 7-2.

[0037] Specifically, the photonic chip also includes a substrate 6 and a shell 5; the shell 5 cooperates with the substrate 6 to encapsulate the optical interference structure, namely the first front-end coupling grating 1-1 and the second front-end coupling grating 1-2, the first rear-end coupling grating 2-1 and the second rear-end coupling grating 2-2 and two MZIs, and a detection window 50 is provided on the shell 5. When the solution to be tested is dropped on the detection window 50, nitrate nitrogen is attached to the first sensor arm 3-1 through the nitrate nitrogen ion selection material 7-1, and ammonium nitrogen is attached to the second sensor arm 3-2 through the ammonium nitrogen ion selection material 7-2.

[0038] It is worth noting that the first sensor arm 3-1 coated with the nitrate nitrogen ion selective material 7-1, the second sensor arm 3-2 coated with the ammonium nitrogen ion selective material 7-2, the first reference arm 4-1 and the second reference arm 4-2 are all exposed in the detection window 50. After the test solution is dropped into them, the first reference arm 4-1 and the second reference arm 4-2 are directly immersed in the test solution; while the first sensor arm 3-1 and the second sensor arm 3-2 have ions filtered by the corresponding ion selective materials.

[0039] In this way, the solution to be tested contacts the first sensor arm 3-1, the second sensor arm 3-2, the first reference arm 4-1 and the second reference arm 4-2 through the detection window 50, the first sensor arm 3-1 realizes the ion selection function through the nitrate nitrogen ion selection material 7-1, and the second sensor arm 3-2 realizes the ion selection function through the ammonium nitrogen ion selection material 7-2.

[0040] In this way, light passing through the first sensing arm 3-1 is affected by nitrate nitrogen ions, while light passing through the first reference arm 4-1 is unaffected. Light passing through the optical interference structure containing the nitrate nitrogen ion selective material 7-1 is spectrally analyzed by the first detector 8-1 to obtain the nitrate nitrogen ion concentration. Light passing through the second sensing arm 3-2 is affected by ammonium nitrogen ions, while light passing through the second reference arm 4-2 is unaffected. Light passing through the optical interference structure containing the ammonium nitrogen ion selective material 7-2 is spectrally analyzed by the second detector 8-2 to obtain the ammonium nitrogen ion concentration. In this way, the nitrate nitrogen ion concentration and the ammonium nitrogen ion concentration, which are highly correlated indicators of soil nitrogen content, are obtained.

[0041] The photonic chip preparation process is divided into two stages: MZI preparation stage and coupled grating preparation stage.

[0042] The MZI preparation process is as follows Figure 2 As shown, the details are as follows: (1) the substrate 6, i.e., the silicon substrate, is cleaned; (2) a 220 nm thick SU8 photoresist is spin-coated on the substrate 6; (3) the waveguide area is exposed to electron beam exposure. After development and fixing, a 220 nm strip waveguide is etched using inductive coupling or other font etching techniques. The resist is then removed to form two MZIs; (4) the MZI sensor arms are functionalized with ion-selective materials. Dual functionalization is used here, i.e., the first sensor arm 3-1 and the second sensor arm 3-2 are modified with two ion-selective materials, nitrate nitrogen and ammonium nitrogen, respectively.

[0043] The coupled grating preparation process includes: (1) spin coating 220nm thick SU8 photoresist on the grating area on the substrate 6 (i.e., both ends of the MZI); (2) electron beam exposure to the grating area, after development and fixing, using inductive coupling and other font etching techniques to etch out a 70nm square waveguide to form four Figure 5The coupling gratings shown are a first front-end coupling grating 1-1, a second front-end coupling grating 1-2, a first rear-end coupling grating 2-1 and a second rear-end coupling grating 2-2.

[0044] In one specific embodiment, the waveguides of the first sensing arm 3-1, the second sensing arm 3-2, the first reference arm 4-1, and the second reference arm 4-2 have a thickness H of 0.22 μm and a width W of 0.5 μm. The reference arm length L0 and the sensing arm length L1 are both 1200 μm. The radius r of the Y-branch of the incident and exit arms is set to 30 μm.

[0045] The coverage length of the nitrate-selective material 7-1 on the first sensing arm 3-1 and the coverage length of the ammonium-selective material 7-2 on the second sensing arm 3-2 are both L2 = 200 μm. The external environment can only interact with the sensing arms through the ion-selective materials. The first sensing arm 3-1 is covered with the nitrate-selective material 7-1, allowing nitrate-nitrogen in the measured environment to pass through and attach to the first sensing arm 3-1. The second sensing arm 3-2 is covered with the ammonium-selective material 7-2, allowing ammonium-nitrogen in the measured environment to pass through and attach to the second sensing arm 3-2.

[0046] The integrated structure of MZI and coupled grating is as follows: Figure 4 As shown, the coupled grating structure is as follows Figure 5 、 Figure 6 As shown. The grating etching depth is 0.07um and the width is W g is 16um, the number of cycles n is 32, the cycle It is 0.615um.

[0047] In this example, the nitrate ion-selective membrane (nitrate-nitrogen ion-selective material) is composed of tridodecylmethylammonium nitrate (TDDMA) dispersed in a plasticized PVC polymer matrix. To improve sensor sensitivity, the nitrate ion carrier concentration is 6.1%, four times higher than the 1.5% concentration of commercial ion-selective materials. The ammonium ion-selective membrane (ammonium-nitrogen ion-selective material) is made of a calixarene material. Both ion-selective materials are 100 μm thick.

[0048] Reference Figure 7 The soil nitrogen detection method proposed in this embodiment is used to detect nitrate nitrogen and ammonium nitrogen in a test solution. The test solution can be a soil solution or soil pore water. The specific steps are as follows: First, deionized water is placed in the detection window 50; the light output by the laser 10 is split by the first Y-shaped optical fiber 9-1 and enters the first front-end coupling grating 1-1 and the second front-end coupling grating 1-2 on the photonic chip respectively; the light output from the first front-end coupling grating 1-1 is divided into two paths by the first incident arm, and enters the first rear-end coupling grating 2-1 along the first sensor arm 3-1 and the first reference arm 4-1 respectively, and is then received by the first detector 8-1 and subjected to spectral analysis; the light output from the second front-end coupling grating 1-2 is divided into two paths by the second incident arm, and enters the second rear-end coupling grating 2-2 along the second sensor arm 3-2 and the second reference arm 4-2 respectively, and is then received by the second detector 8-2 and subjected to spectral analysis; the laser 10 is placed in a scanning state, and the first detector 8-1 and the second detector 8-2 respectively obtain the resonance wavelength of the nitrate nitrogen sensor arm through spectral analysis. and the resonance wavelength of the ammonium nitrogen sensing arm The nitrate nitrogen sensing arm is the first sensing arm 3-1 corresponding to the nitrate nitrogen ion selection material, and the ammonium nitrogen sensing arm is the second sensing arm 3-2 corresponding to the ammonium nitrogen ion selection material; The solution to be tested is placed in the detection window 50; the first sensor arm 3-1 and the second sensor arm 3-2 respectively select nitrate nitrogen ions and ammonium nitrogen ions to enter the selection material under the action of the ion selection material; the laser is in a scanning state, and the first detector 8-1 and the second detector 8-2 respectively obtain the resonance wavelength of the nitrate nitrogen sensor arm through spectral analysis and the resonance wavelength of the ammonium nitrogen sensing arm ; Due to the presence of nitrate nitrogen and ammonium nitrogen ions, the resonance wavelength of the solution to be tested is offset from the resonance wavelength obtained previously when deionized water was added, and the resonance offset is related to the ion concentration, thereby obtaining the nitrate nitrogen and ammonium nitrogen ion concentrations.

[0049] The resonance shifts of nitrate nitrogen and ammonium nitrogen are: ; ; in, and are the resonance shifts of nitrate nitrogen and ammonium nitrogen, respectively.

[0050] The relationship formulas between nitrate nitrogen and ammonium nitrogen offset and concentration are: ; ; in 、 where a and b represent the nitrate and ammonium ion concentrations, respectively. The parameters a and b represent nitrate nitrogen, while c and d represent ammonium nitrogen. These parameters can be determined using a series of soil solutions with known nitrate and ammonium ion concentrations. Once a, b, c, and d are determined, the nitrate and ammonium ion concentrations can be determined by measuring the resonance shift.

[0051] Of course, it will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, but also encompasses the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and it is intended that all variations that fall within the meaning and range of equivalents of the claims be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0052] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0053] The technology, shape, and structure not described in detail in the present invention are all well-known technologies.

Claims

1. A soil nitrogen photon chip sensor, characterized in that: include: A laser, a photonic chip, and two detectors. The photonic chip is equipped with two optical interference structures. Laser light enters the photonic chip and is split into two paths that enter the two optical interference structures. The two detectors correspond to the two optical interference structures. The light is split into two parallel paths in the optical interference structures. One path passes through the ion selection region and is coupled into the detector, while the other path is directly coupled into the detector. The light passing through the ion selection area in the optical interference structure interferes with another light beam, and the detector detects the concentration of the selected ions in the ion selection area through spectral analysis; the ion selection areas in the two optical interference structures are used to screen nitrate nitrogen ions and ammonium nitrogen ions, respectively, and the corresponding two detectors analyze the nitrate nitrogen ion concentration and ammonium nitrogen ion concentration in the test solution based on the acquired spectra.

2. The soil nitrogen photonic chip sensor according to claim 1, characterized in that: The optical interference structure includes an MZI and a front-end coupling grating and a rear-end coupling grating arranged at both ends of the MZI; the laser light enters the MZI through the front-end coupling grating and is split into two. The two light paths pass through the sensing arm and reference arm of the MZI respectively and enter the rear-end coupling grating, and then enter the corresponding detector through the rear-end coupling grating; the sensing arm passes through the ion selection area.

3. The soil nitrogen photonic chip sensor according to claim 2, characterized in that: It also includes a nitrate nitrogen ion selection material and an ammonium nitrogen ion selection material, which are respectively arranged on the sensing arm of the first light interference structure and the sensing arm of the second light interference structure to form an ion selection area that flows with the outside; The nitrate nitrogen ion selective material is composed of tridodecylmethylammonium nitrate dispersed in a plasticized PVC polymer matrix, and the concentration of the nitrate ion carrier is 6.1%; the ammonium nitrogen ion selective material is prepared from a calixarene material.

4. The soil nitrogen photonic chip sensor according to claim 2 or 3, characterized in that: The photonic chip further comprises a substrate (6) and a shell (5); the shell (5) cooperates with the substrate (6) to encapsulate the light interference structure, and a detection window (50) for adding a solution to be tested is provided on the shell (5); the nitrate nitrogen ions and ammonium nitrogen ions in the solution to be tested are attached to the corresponding sensor arms through the nitrate nitrogen ion selection material and the ammonium nitrogen ion selection material respectively.

5. The soil nitrogen photonic chip sensor according to claim 4, characterized in that: The nitrate nitrogen ion selective material and the ammonium nitrogen ion selective material are respectively coated on the corresponding sensing arms.

6. The soil nitrogen photonic chip sensor according to claim 5, characterized in that: The laser adopts a distributed tunable laser.

7. The soil nitrogen photonic chip sensor according to claim 5, characterized in that: The detector uses a silicon detector.

8. A method for manufacturing the soil nitrogen photonic chip sensor according to claim 5, characterized in that: First, a photonic chip is manufactured, and then a laser and a detector are set at both ends of the photonic chip. The manufacturing of the photonic chip includes the following steps: Spin-coat photoresist on the cleaned substrate (6), irradiate the waveguide area with electron beam exposure, and etch out the strip waveguide after development and fixing. After de-resisting, two MZIs are formed; Nitrate nitrogen ion selective material and ammonium nitrogen ion selective material are respectively provided on the sensing arms of the two MZIs; Selecting grating regions at both ends of each MZI on the substrate (6) and spin-coating photoresist, irradiating the grating regions with electron beam exposure, etching out strip waveguides after development and fixing, and forming front-end coupling gratings and rear-end coupling gratings at both ends of the MZI after removing the resist; A housing (5) is provided to encapsulate the MZI structure, and a detection window (50) is provided on the housing (5).

9. A soil nitrogen detection method using the soil nitrogen photonic chip sensor according to claim 5, characterized in that: First, deionized water is placed in the detection window (50), and the laser (10) is in a scanning state. The two detectors respectively obtain the resonance wavelength of the nitrate nitrogen sensor arm. and the resonance wavelength of the ammonium nitrogen sensing arm The nitrate nitrogen sensing arm is a sensing arm of a material that selects nitrate nitrogen ions, and the ammonium nitrogen sensing arm is a sensing arm of a material that selects ammonium nitrogen ions. The solution to be tested is placed in the detection window (50), and the laser (10) is in a scanning state. The two detectors respectively obtain the resonance wavelength of the nitrate nitrogen sensor arm. and the resonance wavelength of the ammonium nitrogen sensing arm ; Resonance shift of nitrate ion Calculate the concentration of nitrate nitrogen ions by the resonance shift of ammonium nitrogen ions Calculate the concentration of ammonium nitrogen ions.

10. The soil nitrogen detection method according to claim 9, wherein: Nitrate nitrogen ion concentration and ammonium nitrogen ion concentration The calculation formula is: ； ； Among them, a and b are nitrate nitrogen parameters, and c and d are ammonium nitrogen parameters; a, b, c, and d are obtained by fitting the known data set.

Images