An optical waveguide sensor and its fabrication method, apparatus and detection method

Abstract

This invention provides an optical waveguide sensor and its fabrication, apparatus, and detection method. The optical waveguide sensor includes a coupling module and an interference module. The coupling module includes a first coupler and a second coupler, and the interference module is located between the first coupler and the second coupler. The interference module includes a sensing arm and a reference arm. The first output terminal of the first coupler is connected to the first end of the sensing arm, and the second output terminal of the first coupler is connected to the first end of the reference arm. The first input terminal of the second coupler is connected to the second end of the sensing arm, and the second input terminal of the second coupler is connected to the second end of the reference arm. The sensing arm includes a first nonlinear gradient waveguide structure, a first mode-spot conversion waveguide structure, a sensing waveguide structure, a second mode-spot conversion waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially and adjacently. By using the optical waveguide sensor provided by this invention and designing multiple waveguide structures in the sensing arm, the detection accuracy of the sensor is effectively improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the fields of optical waveguide technology and optical sensing technology, and particularly to an optical waveguide sensor and its preparation method, device and detection method. Background Technology

[0002] Waveguide optical sensors are optical sensors based on on-chip waveguide structures. These sensors are widely used due to their excellent sensitivity performance resulting from the interaction of the light field between the on-chip strip waveguide and the analyte. To better meet current needs, it is necessary to continuously improve the sensing accuracy of these sensors. Summary of the Invention

[0003] This invention provides an optical waveguide sensor and its fabrication, apparatus, and detection method. By designing multiple waveguide structures in the sensing arm, the detection accuracy of the sensor is effectively improved.

[0004] In a first aspect, embodiments of the present invention provide an optical waveguide sensor, including a coupling module and an interference module;

[0005] The coupling module includes a first coupler and a second coupler, and the interference module is located between the first coupler and the second coupler;

[0006] The interference module includes a sensing arm and a reference arm;

[0007] The first coupler includes a first output terminal and a second output terminal, the first output terminal being connected to a first end of the sensing arm and the second output terminal being connected to a first end of the reference arm; the second coupler includes a first input terminal and a second input terminal, the first input terminal being connected to a second end of the sensing arm and the second input terminal being connected to a second end of the reference arm.

[0008] The sensing arm includes a first nonlinear gradient waveguide structure, a first mode-spot conversion waveguide structure, a sensing waveguide structure, a second mode-spot conversion waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially and adjacently. The first nonlinear gradient waveguide structure is close to the first end of the sensing arm. The first mode-spot conversion waveguide structure is located on the side of the first nonlinear gradient waveguide structure away from the first end of the sensing arm. The sensing waveguide structure is located on the side of the first mode-spot conversion waveguide structure away from the first nonlinear gradient waveguide structure. The second mode-spot conversion waveguide structure is located on the side of the sensing waveguide structure away from the first mode-spot conversion waveguide structure. The second nonlinear gradient waveguide structure is located on the side of the second mode-spot conversion waveguide structure away from the sensing waveguide structure. The second nonlinear gradient waveguide structure is close to the second end of the sensing arm.

[0009] In a second aspect, embodiments of the present invention provide a method for fabricating an optical waveguide sensor, used to fabricate the optical waveguide sensor described in the first aspect, characterized in that the fabrication method includes:

[0010] An interferometric module is fabricated, comprising a sensing arm and a reference arm. The sensing arm includes a first nonlinear gradient waveguide structure, a mode conversion waveguide structure, a sensing waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially adjacent to each other. The first nonlinear gradient waveguide structure is located near a first end of the sensing arm. The first mode conversion waveguide structure is located on the side of the first nonlinear gradient waveguide structure away from the first end of the sensing arm. The sensing waveguide structure is located on the side of the first mode conversion waveguide structure away from the first nonlinear gradient waveguide structure. The second mode conversion waveguide structure is located on the side of the sensing waveguide structure away from the first mode conversion waveguide structure. The second nonlinear gradient waveguide structure is located on the side of the second mode conversion waveguide structure away from the sensing waveguide structure, and the second nonlinear gradient waveguide structure is located near a second end of the sensing arm.

[0011] The control coupling module is connected to the interference module; the first coupler includes a first output terminal and a second output terminal, the first output terminal is connected to the first end of the sensing arm, and the second output terminal is connected to the first end of the reference arm; the second coupler includes a first input terminal and a second input terminal, the first input terminal is connected to the second end of the sensing arm, and the second input terminal is connected to the second end of the reference arm.

[0012] Thirdly, embodiments of the present invention provide an optical waveguide sensing device, including the optical waveguide sensor and laser described in the first aspect, wherein the laser is connected to the input end of the first coupler.

[0013] Fourthly, embodiments of the present invention provide a detection method for an optical waveguide sensing device, comprising the optical waveguide sensing device described in the third aspect, wherein the detection method includes:

[0014] The laser beam is controlled to be input to the first coupler, and the beam is input to the sensing arm and the reference arm through the first output terminal and the second output terminal of the first coupler;

[0015] The interaction between the gas to be measured and the light is controlled within the sensing waveguide structure;

[0016] Calculate the phase difference between the light transmitted from the reference arm to the second coupler and the light transmitted from the sensor to the second coupler;

[0017] The concentration of the gas to be tested is determined based on the phase difference.

[0018] This invention provides an optical waveguide sensor, comprising a coupling module and an interference module. The coupling module includes a first coupler and a second coupler, with the interference module located between the first and second couplers. Further, the interference module includes a sensing arm and a reference arm. The gas to be detected acts at the sensing arm, and the reference arm serves as a reference group to achieve the detection of the gas. The sensing arm comprises a first nonlinear gradient waveguide structure, a first mode-spot conversion waveguide structure, a sensing waveguide structure, a second mode-spot conversion waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially and adjacently. By integrating a slot waveguide Mach-Zehnder interferometer (MZI) into the sensing arm—that is, realizing an MZI-type optical waveguide sensor—and by enriching the structure of the sensing arm, the detection accuracy of the optical waveguide sensor can be effectively improved. Under the same sensing sensitivity requirements, the required length of the optical waveguide can be effectively reduced, thereby reducing the overall size, material, and manufacturing costs of the optical waveguide sensor, improving ease of use, and making it easier to integrate into various terminal electronic devices.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of exemplary embodiments of the present invention, the accompanying drawings used in describing the embodiments are briefly introduced below. Obviously, the accompanying drawings described are only a portion of the drawings of the embodiments to be described in this invention, and not all of the drawings. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of an optical waveguide sensor provided in an embodiment of the present invention;

[0022] Figure 2 yes Figure 1 Enlarged schematic diagram of the middle sensor arm;

[0023] Figure 3 yes Figure 2 A schematic diagram of a cross-section along section line A-A';

[0024] Figure 4 yes Figure 2 A schematic diagram of a cross-section along section line B-B';

[0025] Figure 5 yes Figure 2 A schematic diagram of a cross-section along section line C-C';

[0026] Figure 6 This is a schematic diagram of another optical waveguide sensor provided in an embodiment of the present invention;

[0027] Figure 7 yes Figure 6 Enlarged schematic diagram of the middle sensor arm;

[0028] Figure 8 This is a flowchart of a method for fabricating an optical waveguide sensor according to an embodiment of the present invention;

[0029] Figure 9 This is a flowchart of another method for fabricating an optical waveguide sensor provided in an embodiment of the present invention;

[0030] Figure 10 This is a diagram illustrating the fabrication process of a sensing arm in an optical waveguide sensor provided in an embodiment of the present invention.

[0031] Figure 11 This is a diagram illustrating the fabrication process of the sensing arm in another optical waveguide sensor provided in this embodiment of the invention.

[0032] Figure 12 This is a diagram illustrating the fabrication process of the sensing arm in another optical waveguide sensor provided in this embodiment of the invention.

[0033] Figure 13 This is a schematic diagram of the structure of an optical waveguide sensing device provided in an embodiment of the present invention;

[0034] Figure 14 This is a flowchart of a detection method for an optical waveguide sensing device provided in an embodiment of the present invention. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the invention and not the entire structure. It should be noted that the terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. Moreover, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0036] Figure 1 This is a schematic diagram of the structure of an optical waveguide sensor provided in an embodiment of the present invention. Figure 2 yes Figure 1 A magnified schematic diagram of the middle sensor arm, for reference. Figure 1 and Figure 2As shown, this embodiment of the invention provides an optical waveguide sensor 10, which includes a coupling module 100 and an interference module 200. The coupling module 100 includes a first coupler 110 and a second coupler 120, and the interference module 200 is located between the first coupler 110 and the second coupler 120. The interference module 200 includes a sensing arm 210 and a reference arm 220. The first coupler 110 includes a first output terminal 110a and a second output terminal 110b, the first output terminal 110a being connected to the first end 210a of the sensing arm, and the second output terminal 110b being connected to the first end 220a of the reference arm. The second coupler 120 includes a first input terminal 120a and a second input terminal 120b, the first input terminal 120a being connected to the second end 210b of the sensing arm, and the second input terminal 120b being connected to the second end 220b of the reference arm. The sensing arm 210 includes a first coupler 210a and a second input terminal 220b arranged sequentially adjacent to the second coupler 210a. The system comprises a nonlinear tapered waveguide structure 211, a first mode-spot conversion waveguide structure 212, a sensing waveguide structure 213, a second mode-spot conversion waveguide structure 214, and a second nonlinear tapered waveguide structure 215. The first nonlinear tapered waveguide structure 211 is located near the first end 210a of the sensing arm. The first mode-spot conversion waveguide structure 212 is located on the side of the first nonlinear tapered waveguide structure 211 away from the first end 210a of the sensing arm. The sensing waveguide structure 213 is located on the side of the first mode-spot conversion waveguide structure 212 away from the first nonlinear tapered waveguide structure 211. The second mode-spot conversion waveguide structure 214 is located on the side of the sensing waveguide structure 213 away from the first mode-spot conversion waveguide structure 212. The second nonlinear tapered waveguide structure 215 is located on the side of the second mode-spot conversion waveguide structure 214 away from the sensing waveguide structure 213, and the second nonlinear tapered waveguide structure 215 is located near the second end 210b of the sensing arm.

[0037] Among them, reference Figure 1 As shown, the optical waveguide sensor 10 includes a coupling module 100 and an interference module 200. The coupling module 100 includes a first coupler 110 and a second coupler 120, and the interference module 200 includes a sensing arm 210 and a reference arm 220. The first coupler 110 and the second coupler 120 are located on opposite sides of the interference module 200. The first coupler 110 includes two output ports: a first output terminal 110a connected to the sensing arm 210, and a second output terminal 110b connected to the reference arm 220. The second coupler 120 includes two input ports: a first input port 120a connected to the sensing arm 210, and a second input port 120b connected to the reference arm 220. This arrangement allows the sensing arm 210 and the reference arm 220 in the interference module 200 to be positioned between the first coupler 110 and the second coupler 120.

[0038] For details regarding the connection relationship between the interference module 200 and the coupling module 100, please refer to [reference needed]. Figure 1 As shown, the first output terminal 110a of the first coupler 110 is connected to the first end 210a of the sensing arm 210, and the second output terminal 110b of the first coupler 110 is connected to the first end 220a of the reference arm 220; the first input terminal 120a of the second coupler 120 is connected to the second end 210b of the sensing arm 210, and the second input terminal 120b of the second coupler 120 is connected to the second end 220b of the reference arm 220.

[0039] Furthermore, the optical waveguide sensor 10 detects the gas to be measured using an optical waveguide. An optical waveguide is a medium device that guides light waves to propagate; it is also called a dielectric optical waveguide. The transmission of light waves is achieved through the waveguide structure. The first coupler 110 also ensures at least one input port (…). Figure 1 (Not specifically shown), the input port transmits light to the first coupler 110. The light received by the first coupler 110 can be transmitted to the sensing arm 210 and the reference arm 220 through two output ports, respectively, where the sensing arm 210 and the reference arm 220 are waveguide structures. At the sensing arm 210, the light interacts with the gas being measured, for example, causing a change in the refractive index of the light; while at the reference arm 220, the light remains in its original state. The second coupler 120 also includes at least two output ports ( Figure 1 (Not specifically shown in the image) The second coupler 120 is used to output the light transmitted in the reference arm 220 and the sensing arm 210. By comparing the two types of light output by the second coupler 120, such as comparing the light intensity, the optical waveguide sensor 10 can detect the gas to be measured by combining the light judgment.

[0040] Alternatively, the basic principle of the optical waveguide sensor 10 can be understood as follows: the waveguide structure at the sensing waveguide structure 213 interacts with external gas molecules, altering the light transmission characteristics. Therefore, during the sensing and detection process, the reference arm 220 is placed in the air, and the sensing arm 210 is used to introduce the gas to be measured. The concentration of the gas to be measured is calculated by the ratio of the light field intensity after interference of the output light on both sides. When the optical waveguide transmitted in the sensing waveguide structure 213 interacts with the gas to be measured, or when they are coupled, the overall structure of the sensing waveguide structure 213 is an important indicator affecting the coupling loss. By adjusting the structure of the sensing waveguide structure 213, the detection accuracy of the gas to be measured can be improved.

[0041] Among them, reference Figure 1 and Figure 2As shown, the sensing arm 210 includes a first nonlinear gradient waveguide structure 211, a first mode-spot conversion waveguide structure 212, a sensing waveguide structure 213, a second mode-spot conversion waveguide structure 214, and a second nonlinear gradient waveguide structure 215. These waveguide structures are arranged sequentially adjacent to each other. Specifically, along the direction from the first coupler 110 to the second coupler 120, the waveguide structures in the sensing arm 210 are, in sequence: the first nonlinear gradient waveguide structure 211, the first mode-spot conversion waveguide structure 212, the sensing waveguide structure 213, the second mode-spot conversion waveguide structure 214, and the second nonlinear gradient waveguide structure 215. By enriching the waveguide structure in the sensing arm 210, the interaction between the sensing arm 210 and the gas to be measured can be improved, thereby ensuring the detection accuracy of the optical waveguide sensor 10 for the gas to be measured.

[0042] Furthermore, the light transmitted to the sensing arm 210 via the first coupler 110 can first undergo optical field mode conversion via the first nonlinear gradient waveguide structure 211, for example, from TE0 to TE1 or TE2, i.e., from the fundamental mode of the transverse electric mode to a higher-order mode of the transverse electric mode, where TE0, TE1, and TE2 represent different modes of the optical field. Further, after passing through the first nonlinear gradient waveguide structure 211, the light is transmitted to the sensing waveguide structure 213 via the first mode-spot conversion waveguide structure 212, where it interacts with the gas to be measured at the sensing waveguide structure 210. The first mode-spot conversion waveguide structure 212 allows for adjustment of the number of light transmission paths and the size of the light spot, thereby ensuring better interaction between the light and the gas to be measured at the sensing waveguide structure 210. Furthermore, the sensing arm 210 also includes a second mode-spot conversion waveguide structure 214 and a second nonlinear gradient waveguide structure 215. The second mode-spot conversion waveguide structure 214 is used to adjust the number of transmission paths and the spot size of the light rays after interacting with the gas to be measured back to their original state when they were transmitted to the first mode-spot conversion waveguide structure 212. Then, the second nonlinear gradient waveguide structure 215 adjusts the light field mode back to its original state, for example, from TE1 or TE2 to TE0, that is, converting the higher-order mode of the transverse electric mode to the fundamental mode of the transverse electric mode. The first nonlinear gradient waveguide structure 211 and the first mode-spot conversion waveguide structure 212 can ensure that the light rays transmitted to the sensing waveguide structure 213 interact fully with the gas to be measured. This can also be understood as adjusting the light transmission effect through the cooperation of the nonlinear gradient waveguide structure and the mode-spot conversion waveguide structure. The light can be adjusted back to its original mode by the second mode conversion waveguide structure 214 and the second nonlinear gradient waveguide structure 215, ensuring that the light emitted from the sensing arm 210 corresponds to the light emitted from the reference arm 220, which facilitates the comparison of parameters such as light intensity. Combined with the judgment of the light, the optical waveguide sensor 10 can detect the gas to be measured.

[0043] Furthermore, the sequentially adjacent waveguide structures in the sensing arm 210 can be understood as follows: with the sensing waveguide structure 213 as the center, the first mode-spot conversion waveguide structure 212 and the second mode-spot conversion waveguide structure 214 are symmetrically arranged, as are the first nonlinear gradient waveguide structure 211 and the second nonlinear gradient waveguide structure 215. By utilizing the different transmission modes in the sensing arm 210 and the reference arm 220, the sensitivity of the optical waveguide sensor 10 can be improved within a limited arm length.

[0044] In summary, this invention provides an optical waveguide sensor, wherein the interference module includes a sensing arm and a reference arm. The gas to be detected interacts with the sensing arm, and the reference arm serves as a reference group to achieve the detection of the gas. Furthermore, the sensing arm includes a first nonlinear gradient waveguide structure, a first mode-spot conversion waveguide structure, a sensing waveguide structure, a second mode-spot conversion waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially adjacent to each other. By enriching the structure of the sensing arm, the detection accuracy of the optical waveguide sensor can be effectively improved.

[0045] Figure 3 yes Figure 2 A schematic diagram of a cross-section along section line A-A'. Figure 4 yes Figure 2 A schematic diagram of a cross-section along section line B-B'. Figure 5 yes Figure 2 A schematic diagram of a cross-section along section line C-C', for reference. Figures 1 to 5 As shown, the optical waveguide sensor 10 includes a substrate 300 and a cladding 400. The cladding 400 includes a first cladding 410 and a second cladding 420. The first cladding 410 is located on one side of the substrate 300, and the second cladding 420 is located on the side of the first cladding 410 away from the substrate 300. The first cladding 410 includes a first groove 411 penetrating the first cladding 410, and the second cladding 420 includes a second groove 421 penetrating the second cladding 420. The orthographic projection of the first groove 411 onto the substrate 300 overlaps with the orthographic projection of the second groove 421 onto the substrate 300. Along the thickness direction X1 of the substrate 300, the reference arm 220, the first nonlinear gradient waveguide structure 211, the first mode conversion waveguide structure 212, the second mode conversion waveguide structure 214, and the second nonlinear gradient waveguide structure 215 are located at the first... Between the first cladding 410 and the second cladding 420; along the direction X2 from the first coupler 110 to the second coupler 120, the projection of the sensing waveguide structure 213 at least partially overlaps with the projection of the first mode conversion waveguide structure 212; the orthographic projection of the sensing waveguide structure 213 onto the substrate 400 at least partially overlaps with the orthographic projection of the first groove 411 onto the substrate 400; the sensing waveguide structure 213 includes a first waveguide 213a and a second waveguide 213b, the first end 213a1 of the first waveguide is connected to the first mode conversion waveguide structure 212, the first end 213b1 of the second waveguide is connected to the first mode conversion waveguide structure 213; the second end 213a2 of the first waveguide is connected to the second mode conversion waveguide structure 214, and the second end 213b2 of the second waveguide is connected to the second mode conversion waveguide structure 214.

[0046] Further reference Figures 2 to 5As shown, the optical waveguide sensor 10 includes a substrate 300, and a cladding layer 400 is provided on one side of the substrate 300. The cladding layer 400 includes a first cladding layer 410 and a second cladding layer 420, which are used to cover the waveguide structure.

[0047] Specifically, the reference arm 220, the first nonlinear gradient waveguide structure 211, the first mode-spot conversion waveguide structure 212, the second mode-spot conversion waveguide structure 214, and the second nonlinear gradient waveguide structure 215 are located between the first cladding 410 and the second cladding 420. This can also be understood as the first cladding 410 and the second cladding 420 enclosing the reference arm 220, the first nonlinear gradient waveguide structure 211, the first mode-spot conversion waveguide structure 212, the second mode-spot conversion waveguide structure 214, and the second nonlinear gradient waveguide structure 215. For example, the reference... Figure 2 and Figure 3 As shown, Figure 3 The diagram shows the positional relationship between the first nonlinear gradient waveguide structure 211 in the first cladding 410 and the second cladding 420. Similarly, the positions of the reference arm 220, the first mode conversion waveguide structure 212, the second mode conversion waveguide structure 214, and the second nonlinear gradient waveguide structure 215 are similar and will not be listed individually.

[0048] Further reference Figure 2 As shown, the sensing waveguide structure 213 includes a first waveguide 213a and a second waveguide 213b. Light rays transmitted to the sensing waveguide structure 213 continue to propagate through the first waveguide 213a and the second waveguide 213b. Alternatively, it can be understood that setting two waveguide structures at the sensing waveguide structure 213 can improve the interaction efficiency between light and the gas to be measured. In this design, the first end 213a1 of the first waveguide is connected to the first mode-spot conversion waveguide structure 212, and the second end 213a2 of the first waveguide is connected to the second mode-spot conversion waveguide structure 214, ensuring that the first waveguide 213a exists between the first mode-spot conversion waveguide structure 212 and the second mode-spot conversion waveguide structure 214. Similarly, the first end 213b1 of the second waveguide is connected to the first mode-spot conversion waveguide structure 213, and the second end 213b2 of the second waveguide is connected to the second mode-spot conversion waveguide structure 214, ensuring that the second waveguide 213b exists between the first mode-spot conversion waveguide structure 212 and the second mode-spot conversion waveguide structure 214. Furthermore, along the direction X2 from the first coupler 110 to the second coupler 120, the projection of the sensing waveguide structure 213 at least partially overlaps with the projection of the first mode-spot conversion waveguide structure 212. This can be understood as the first waveguide 213a and the second waveguide 213b being fabricated in the same layer as the remaining waveguide structures. Figures 3 to 5 As shown ( Figure 5(Taking the second waveguide 213b as an example) The sensing waveguide structure 213 is arranged in the same layer as the first mode conversion waveguide structure 212, and the sensing waveguide structure 213 is also arranged in the same layer as the first nonlinear gradient waveguide structure 211.

[0049] Further reference Figure 2 , Figure 4 and Figure 5 As shown, the first cladding layer 410 includes a first groove 411, which penetrates the first cladding layer 410, thus exposing the substrate 300 through the first groove 411. The second cladding layer 420 includes a second groove 421, which penetrates the second cladding layer 420. The orthographic projection of the first groove 411 onto the substrate 300 overlaps with the orthographic projection of the second groove 421 onto the substrate 300, thus exposing the substrate 300 through both the second groove 421 and the first groove 411.

[0050] In this configuration, the orthographic projection of the sensing waveguide structure 213 onto the substrate 400 at least partially overlaps with the orthographic projection of the first groove 411 onto the substrate 400, in combination with... Figure 2 , Figure 4 and Figure 5 As shown, the first waveguide 213a and the second waveguide 213b are suspended within the space formed by the first groove 411 and the second groove 421, and serve as suspension support points for the first waveguide 213a and the second waveguide 213b through their connection with the first mode conversion waveguide structure and the second mode conversion waveguide structure. This can be understood as the sensing waveguide structure 213 being located within the groove region formed by the first cladding 410 and the second cladding 420.

[0051] The optical waveguide sensor 10 provided in this embodiment of the invention features a grooved design in the sensing waveguide structure 213 of the sensing arm 210. Specifically, the first waveguide 213a and the second waveguide 213b are positioned within the groove. This grooved waveguide structure maximizes the evanescent field confinement factor of the cladding. Furthermore, the concentration of the gas to be measured is analyzed by the interference result with the optical signal in the reference arm 220, thereby improving the detection accuracy of the gas to be measured.

[0052] Optionally, the waveguide structure can be made of silicon, that is, the first waveguide 213a and the second waveguide 213b can be made of silicon. The substrate 300 and the cladding 400 can be made of silicon oxide.

[0053] Due to the generally high refractive index of silicon oxide, a first waveguide 213a and a second waveguide 213b are provided to enhance the efficient interaction between the transmitted light and the gas molecules of the target gas within the sensing waveguide structure 213. A slit exists between the first waveguide 213a and the second waveguide 213b; this slit waveguide allows the light field to propagate between them. The waveguide structure within the sensing waveguide structure 213 is further optimized using the time-difference finite element method, thereby improving the interaction between the gas molecules and the light within the waveguide structure. Specifically, the first nonlinear gradient waveguide structure 211 effectively couples the external laser into the optical waveguide sensor 10, reducing coupling loss and thus lowering system power consumption. It can also be combined with a first mode-spot conversion waveguide structure 212 to reduce structural differences caused by the slit waveguide, significantly improving coupling efficiency and ensuring the effective interaction between the sensing waveguide structure 213 and the target gas, thereby enhancing the detection accuracy of the optical waveguide sensor 10.

[0054] Continue to refer to Figure 2 and Figure 4 As shown, along the first direction X3, the gap between the first waveguide 213a and the second waveguide 213b is d, where 0.1 micrometers ≤ d ≤ 0.3 micrometers, and the first direction is perpendicular to the transmission direction of the optical waveguide in the sensing waveguide structure.

[0055] Furthermore, along the first direction X3, the gap between the first waveguide 213a and the second waveguide 213b is d. And d satisfies: 0.1 μm ≤ d ≤ 0.3 μm. The specific parameter of the gap d can be adaptively adjusted based on the dimensions of the first waveguide 213a and the second waveguide 213b. For example, when the width of the first waveguide 213a along the first direction X3 is 0.52 μm, the gap d can be 0.2 μm. At this point, the cladding confinement factor is maximized (optical energy is distributed to the maximum extent in the gap between the first waveguide 213a and the second waveguide 213b), and the transmission loss is minimized, for example, around 1 dB / cm. Specific values ​​can be adjusted according to different practical needs.

[0056] Continue to refer to Figure 2As shown, along direction X2 from the first coupler 110 to the second coupler 120, the length of the first nonlinear tapered waveguide structure 211 is L1, the length of the first mode-spot conversion waveguide structure 212 is L2, the length of the sensing waveguide structure 213 is L3, the length of the second mode-spot conversion waveguide structure 214 is L4, and the length of the second nonlinear tapered waveguide structure 215 is L5; along direction X3 perpendicular to the first coupler 110 to the second coupler 120, the length of the first nonlinear tapered waveguide structure... The width of the first mode-spot conversion waveguide structure 211 away from the first mode-spot conversion waveguide structure 212 is W1; the width of the first nonlinear gradient waveguide structure 211 close to the first mode-spot conversion waveguide structure 212 is W2; the width of the first mode-spot conversion waveguide structure 212 close to the first nonlinear gradient waveguide structure 211 is W3; the width of the first mode-spot conversion waveguide structure 212 close to the sensing waveguide structure 213 is W4; the width of the sensing waveguide structure 213 is W5; and the width of the second mode-spot conversion waveguide structure 214 close to the sensing waveguide structure 213 is W5. The width of waveguide structure 213 is W6; the width of the second mode-spot conversion waveguide structure 214 near the second nonlinear tapered waveguide structure 215 is W7; the width of the second nonlinear tapered waveguide structure 215 near the second mode-spot conversion waveguide structure 214 is W8; and the width of the second nonlinear tapered waveguide structure 215 away from the second mode-spot conversion waveguide structure 214 is W9; wherein: 500 μm ≤ L1 ≤ 700 μm, 30 μm ≤ L2 ≤ 70 μm, 100 μm ≤ L3 ≤ 300 μm. Meters; 30 micrometers ≤ L4 ≤ 70 micrometers, 500 micrometers ≤ L5 ≤ 700 micrometers; 0.1 micrometers ≤ W1 ≤ 0.5 micrometers, 0.5 micrometers ≤ W2 ≤ 1.0 micrometers, 0.5 micrometers ≤ W3 ≤ 1.0 micrometers, 1.0 micrometers ≤ W4 ≤ 1.5 micrometers, 1.0 micrometers ≤ W5 ≤ 1.5 micrometers, 1.0 micrometers ≤ W6 ≤ 1.5 micrometers, 0.5 micrometers ≤ W7 ≤ 1.0 micrometers, 0.5 micrometers ≤ W8 ≤ 1.0 micrometers, 0.1 micrometers ≤ W9 ≤ 0.5 micrometers.

[0057] Further reference Figure 1 and Figure 2As shown, along the direction X2 from the first coupler 110 to the second coupler 120, the length of the first nonlinear tapered waveguide structure 211 is L1, and the length of the second nonlinear tapered waveguide structure 215 is L5. L1 and L5 satisfy: 500 μm ≤ L1 ≤ 700 μm, 500 μm ≤ L5 ≤ 700 μm. For example, L1 can be 600 μm, and L5 can be 600 μm. Furthermore, to ensure the structural regularity of the optical waveguide sensor 10, the length of the first nonlinear tapered waveguide structure 211 and the length of the second nonlinear tapered waveguide structure 215 can be adjusted to be the same as or similar. For example, calculations show that when the first nonlinear tapered waveguide structure 211 and the second nonlinear tapered waveguide structure 215 reach 600 μm, the coupling efficiency gradually stabilizes, and the coupling loss is relatively small. Meanwhile, along direction X3 perpendicular to the first coupler 110 and pointing towards the second coupler 120, the first nonlinear gradient waveguide structure 211 and the second nonlinear gradient waveguide structure 215 are waveguide structures with gradually changing dimensions. Their widths away from the sensing waveguide structure 213 are W1 and W9, respectively, and their widths near the sensing waveguide structure 213 are W2 and W8, respectively. W1 and W9 satisfy the following conditions: 0.1 μm ≤ W1 ≤ 0.5 μm, 0.1 μm ≤ W9 ≤ 0.5 μm (e.g., W1 could be 0.2 μm, W9 could be 0.2 μm), 0.5 μm ≤ W2 ≤ 1.0 μm, 0.5 μm ≤ W8 ≤ 1.0 μm (e.g., W2 could be 0.8 μm, W8 could be 0.8 μm). Furthermore, to ensure the structural regularity of the optical waveguide sensor 10, the width of the first nonlinear gradient waveguide structure 211 can be adjusted to be the same as or similar to the width of the second nonlinear gradient waveguide structure 215.

[0058] Further reference Figure 1 and Figure 2As shown, along the direction X2 from the first coupler 110 to the second coupler 120, the length of the first mode-spot conversion waveguide structure 212 is L2, and the length of the second mode-spot conversion waveguide structure 214 is L4. L2 and L4 satisfy: 30 μm ≤ L2 ≤ 70 μm, 30 μm ≤ L4 ≤ 70 μm. For example, L2 can be 50 μm, and L4 can be 50 μm. Furthermore, to ensure the structural regularity of the optical waveguide sensor 10, the length of the first mode-spot conversion waveguide structure 212 and the length of the second mode-spot conversion waveguide structure 214 can be adjusted to be the same as or similar. For example, calculations show that when the first mode-spot conversion waveguide structure 212 and the second mode-spot conversion waveguide structure 214 reach 50 μm, the optical waveguide transmission effect is higher. Simultaneously, along direction X3 perpendicular to the first coupler 110 and pointing towards the second coupler 120, the widths of the first mode-spot conversion waveguide structure 212 and the second mode-spot conversion waveguide structure 214 that are far from the sensing waveguide structure 213 are W3 and W7, respectively, and the widths of their widths that are close to the sensing waveguide structure 213 are W4 and W6, respectively. W3 and W7 satisfy the following conditions: 0.5 μm ≤ W3 ≤ 1.0 μm, 0.5 μm ≤ W7 ≤ 1.0 μm (e.g., W3 can be 0.8 μm, W7 can be 0.8 μm); 1.0 μm ≤ W4 ≤ 1.5 μm, 1.0 μm ≤ W6 ≤ 1.5 μm (e.g., W4 can be 1.24 μm, W8 can be 1.24 μm). Furthermore, to ensure the structural regularity of the optical waveguide sensor 10, the widths of the first mode-spot conversion waveguide structure 212 and the second mode-spot conversion waveguide structure 214 can be adjusted to be the same or similar.

[0059] Further reference Figure 2 As shown, along the direction X2 from the first coupler 110 to the second coupler 120, the length of the sensing waveguide structure 213 is L3, which satisfies the condition: 100 μm ≤ L3 ≤ 300 μm, and L3 can be 200 μm. Along the direction X3 perpendicular to the first coupler 110 to the second coupler 120, the width of the sensing waveguide structure 213 is W5, which can satisfy the condition: 1.0 μm ≤ W5 ≤ 1.5 μm, for example, W5 can be 1.24 μm. The specific dimensions of the waveguide structure can also be adaptively adjusted according to actual needs.

[0060] Figure 6 This is a schematic diagram of another optical waveguide sensor provided in an embodiment of the present invention. Figure 7 yes Figure 6 A magnified schematic diagram of the middle sensor arm, for reference. Figure 1 and Figure 2 ,refer to Figure 6 and Figure 7 As shown, the sensing waveguide structure 213 includes a linear waveguide structure or a curved waveguide structure.

[0061] Further reference Figure 1 and Figure 2 As shown, the sensing waveguide structure 213 in the optical waveguide sensor 10 is linear in shape, meaning it is a linear waveguide structure. The fabrication process of a linear waveguide structure is simple, which can reduce the manufacturing cost of the optical waveguide sensor 10. (Reference) Figure 6 and Figure 7 As shown, the shape is curved, meaning the sensing waveguide structure 213 is a curved waveguide structure. The curved waveguide structure increases the aperture area in contact with the gas being measured, improving detection efficiency. Combined with... Figure 1 , Figure 2 , Figure 6 and Figure 7 As shown, the configuration of the sensing waveguide structure 213 is diverse.

[0062] Based on the same inventive concept, embodiments of the present invention also provide a method for fabricating an optical waveguide sensor. Figure 8 This is a flowchart illustrating a method for fabricating an optical waveguide sensor according to an embodiment of the present invention. (Refer to...) Figure 8 As shown, the preparation method includes:

[0063] S110, Prepare the interference module.

[0064] Furthermore, the optical waveguide sensor detects the gas to be measured using an optical waveguide. An optical waveguide is a medium device that guides light waves to propagate; it is also called a dielectric optical waveguide. The transmission of light waves is achieved through the waveguide structure. The interference module includes a sensing arm and a reference arm. The sensing arm comprises a first nonlinear gradient waveguide structure, a first mode-spot conversion waveguide structure, a sensing waveguide structure, a second mode-spot conversion waveguide structure, and a second nonlinear gradient waveguide structure. These waveguide structures are arranged sequentially and adjacently. By enriching the waveguide structure in the sensing arm, the interaction between the sensing arm and the gas to be measured can be improved, thereby ensuring the detection accuracy of the optical waveguide sensor.

[0065] S120, the control coupling module is connected to the interference module.

[0066] The optical waveguide sensor further includes a coupling module and an interference module. The coupling module includes a first coupler and a second coupler, which are positioned on opposite sides of the interference module. The first coupler has two output ports: a first output port connected to a sensing arm and a second output port connected to a reference arm. The second coupler has two input ports: a first input port connected to the sensing arm and a second input port connected to the reference arm, thus positioning the sensing arm and reference arm in the interference module between the first and second couplers.

[0067] For details regarding the connection relationship between the interference module 200 and the coupling module 100, please refer to [reference needed]. Figure 1 As shown, the first output terminal 110a of the first coupler 110 is connected to the first end 210a of the sensing arm 210, and the second output terminal 110b of the first coupler 110 is connected to the first end 220a of the reference arm 220; the first input terminal 120a of the second coupler 120 is connected to the second end 210b of the sensing arm 210, and the second input terminal 120b of the second coupler 120 is connected to the second end 220b of the reference arm 220.

[0068] The first coupler also ensures at least one input port, through which light is transmitted. The light received by the first coupler can be transmitted through two output ports to the sensing arm and reference arm, respectively, where the sensing arm and reference arm are waveguide structures. At the sensing arm, the light interacts with the gas being measured, for example, causing a change in the refractive index of the light; while the light transmitted at the reference arm 220 remains in its original state. The second coupler also includes at least two output ports. The second coupler 120 is used to output the light transmitted from the reference arm and sensing arm. By comparing the two types of light output from the second coupler, such as comparing light intensity, and combining this information with the light analysis, the optical waveguide sensor can detect the gas being measured.

[0069] Alternatively, the basic principle of an optical waveguide sensor can be understood as follows: the waveguide structure at the sensing waveguide interacts with external gas molecules, altering the light transmission characteristics. Therefore, during the sensing and detection process, the reference arm is placed in the air, and the sensing arm is used to introduce the gas to be measured. The concentration of the gas to be measured is calculated by the ratio of the light field intensities after interference from the output light on both sides. When the optical waveguide propagating in the sensing waveguide interacts with the gas to be measured, or when they are coupled, the overall structure of the sensing waveguide is a crucial indicator affecting the coupling loss. By adjusting the structure of the sensing waveguide, the detection accuracy of the gas to be measured can be improved.

[0070] Furthermore, the light transmitted to the sensing arm via the first coupler can first undergo optical field mode conversion through the first nonlinear gradient waveguide structure, for example, from TE0 to TE1 or TE2, i.e., from the fundamental mode of the transverse electric mode to a higher-order mode of the transverse electric mode, where TE0, TE1, and TE2 represent different modes of the optical field. Further, after passing through the first nonlinear gradient waveguide structure, the light is transmitted to the sensing waveguide structure through the first mode-spot conversion waveguide structure, where it interacts with the gas to be measured. The first mode-spot conversion waveguide structure allows for adjustment of the number of light transmission paths and the size of the light spot, thereby ensuring better interaction between the light and the gas to be measured at the sensing waveguide structure. Furthermore, the sensing arm also includes a second mode-spot conversion waveguide structure and a second nonlinear gradient waveguide structure. The second mode-spot conversion waveguide structure is used to adjust the light rays after interacting with the gas to be measured back to their original path length and spot size when transmitted to the first mode-spot conversion waveguide structure. Then, the second nonlinear gradient waveguide structure adjusts the light field mode back to its original mode, for example, from TE1 or TE2 to TE0, i.e., converting a higher-order mode of the transverse electric mode to the fundamental mode of the transverse electric mode. The first nonlinear gradient waveguide structure and the first mode-spot conversion waveguide structure ensure that the light rays transmitted to the sensing waveguide structure interact fully with the gas to be measured. This can also be understood as adjusting the light transmission effect through the cooperation of the nonlinear gradient waveguide structure and the mode-spot conversion waveguide structure. The second mode-spot conversion waveguide structure and the second nonlinear gradient waveguide structure adjust the light rays back to their original mode, ensuring a correspondence between the light rays emitted from the sensing arm and the light rays emitted from the reference arm, facilitating the comparison of parameters such as light intensity. Combined with the judgment of the light rays, the optical waveguide sensor can detect the gas to be measured.

[0071] Furthermore, the sequentially adjacent waveguide structures within the sensing arm can be understood as follows: with the sensing waveguide structure at the center, the first and second mode-spot conversion waveguide structures are symmetrically arranged, as are the first and second nonlinear gradient waveguide structures. By utilizing the different transmission modes in the sensing arm and reference arm, the sensitivity of the optical waveguide sensor can be improved within a limited arm length.

[0072] In summary, the method for fabricating an optical waveguide sensor provided in this embodiment of the invention can effectively improve the detection accuracy of the optical waveguide sensor by adjusting the sensing arm in the interference module. Specifically, the sensing arm includes a first nonlinear gradient waveguide structure, a first mode-spot conversion waveguide structure, a sensing waveguide structure, a second mode-spot conversion waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially adjacent to each other.

[0073] Figure 9 This is a flowchart of another method for fabricating an optical waveguide sensor provided in an embodiment of the present invention. Figure 10This is a diagram illustrating the fabrication process of the sensing arm in an optical waveguide sensor according to an embodiment of the present invention. Figure 11 This is a diagram illustrating the fabrication process of the sensing arm in another optical waveguide sensor provided in this embodiment of the invention. Figure 12 This is a fabrication process diagram of the sensing arm in another optical waveguide sensor provided in this embodiment of the invention, for reference. Figures 9 to 12 As shown, the fabrication process of the interference module includes:

[0074] S210, providing a substrate and a first cladding layer.

[0075] refer to Figure 1 and Figure 2 As shown, the sensing arm 210 of the interference module 200 includes a first nonlinear gradient waveguide structure 211, a first mode-spot conversion waveguide structure 212, a sensing waveguide structure 213, a second mode-spot conversion waveguide structure 214, and a second nonlinear gradient waveguide structure 215.

[0076] For the fabrication of the first nonlinear gradient waveguide structure 211, the first mode-spot conversion waveguide structure 212, the second mode-spot conversion waveguide structure 214, and the second nonlinear gradient waveguide structure 215, the following reference can be made: Figure 10 As shown, the following can be used as a reference when fabricating the sensing waveguide structure 213. Figure 11 and Figure 12 As shown.

[0077] When preparing the interference module, refer to Figure 10 Step a, Figure 11 In step a and Figure 12 As shown in step a, a substrate 300 and a first cladding layer 410 on one side of the substrate 300 are prepared.

[0078] S220. Deposit a waveguide structure layer on the side of the first cladding away from the substrate.

[0079] Further reference Figure 10 Step b, Figure 11 middle step b and Figure 12 As shown in step b, a waveguide structure layer 2100 is deposited on the side of the first cladding layer 410 away from the substrate 300. Subsequently, the waveguide structure layer 2100 is etched to realize the fabrication of the first nonlinear gradient waveguide structure 211, the first mode-spot conversion waveguide structure 212, the sensing waveguide structure 213, the second mode-spot conversion waveguide structure 214, and the second nonlinear gradient waveguide structure 215.

[0080] S230, patterned waveguide structure layer and fabrication of reference arm, first nonlinear gradient waveguide structure, first mode-spot conversion waveguide structure, sensing waveguide structure, second mode-spot conversion waveguide structure and second nonlinear gradient waveguide structure.

[0081] Further reference Figure 10 As shown in step c, the first nonlinear gradient waveguide structure 211 is prepared by patterning and etching the waveguide structure layer 2100. Figure 10 The preparation of the first nonlinear gradient waveguide structure is used as an example for illustration. The preparation processes of the first mode-spot conversion waveguide structure, the second mode-spot conversion waveguide structure, and the second nonlinear gradient waveguide structure are similar and will not be illustrated one by one.

[0082] refer to Figure 11 middle step c and Figure 12 As shown in step c, the sensing waveguide structure 213 is fabricated by patterning and etching the waveguide structure 2100.

[0083] The patterning process can be understood as follows: photoresist is coated on the side of the waveguide structure away from the substrate, and then exposed using an electron beam. After development and fixing, inductively coupled plasma etching is used to form the final waveguide structure, namely, a first nonlinear gradient waveguide structure, a first mode-conversion waveguide structure, a sensing waveguide structure, a second mode-conversion waveguide structure, and a second nonlinear gradient waveguide structure. Finally, the coated photoresist is removed.

[0084] S240. A second cladding is prepared on the side of the waveguide structure away from the first cladding, and the second cladding covers the waveguide structure.

[0085] Further reference Figure 10 Step d, Figure 11 middle step d and Figure 12 As shown in step d, a second cladding layer 420 is fabricated on the side of the patterned waveguide structure (first nonlinear gradient waveguide structure, first mode-spot conversion waveguide structure, sensing waveguide structure, second mode-spot conversion waveguide structure, and second nonlinear gradient waveguide structure) away from the substrate. The second cladding layer 420 covers the waveguide structure, or it can be understood that the first cladding layer 410 and the second cladding layer 420 encapsulate the waveguide structure.

[0086] Optionally, after patterning the waveguide structure layer to prepare the waveguide structure, a silicon dioxide layer of about 2 micrometers is deposited on the surface of the waveguide structure using plasma-enhanced chemical vapor deposition (PECVD) technology, i.e., a second cladding layer is deposited to cover the waveguide structure.

[0087] S250, pattern the first cladding layer and the second cladding layer, and prepare the first groove and the second groove.

[0088] Further reference Figure 11 middle step e and Figure 12As shown in step e, the first cladding layer 410 and the second cladding layer 420 are etched to form the first groove 411 and the second groove 412, thereby exposing at least a portion of the substrate 300.

[0089] In this configuration, the orthographic projection of the sensing waveguide structure 213 onto the substrate 400 at least partially overlaps with the orthographic projection of the first groove 411 onto the substrate 400, in combination with... Figure 2 , Figure 4 and Figure 5 As shown, the first waveguide 213a and the second waveguide 213b are suspended within the space formed by the first groove 411 and the second groove 421, and serve as suspension support points for the first waveguide 213a and the second waveguide 213b through their connection with the first mode conversion waveguide structure and the second mode conversion waveguide structure. This can be understood as the sensing waveguide structure 213 being located within the groove region formed by the first cladding 410 and the second cladding 420.

[0090] Optionally, after fabricating the second cladding layer, photoresist is spin-coated again on the side of the second cladding layer away from the first cladding layer, and the second cladding layer is irradiated with an electron beam (irradiating the area where the first and second grooves are to be fabricated). After development and fixing, the entire structure is immersed in a hydrofluoric acid (HF) solution. Areas not irradiated by the electron beam are protected by the photoresist; that is, the first and second cladding layers in the areas where the first nonlinear gradient waveguide structure, the first mode-spot conversion waveguide structure, the second mode-spot conversion waveguide structure, and the second nonlinear gradient waveguide structure are located do not come into contact with HF and are thus preserved. However, the areas not covered by photoresist, i.e., the second and first cladding layers at the sensing waveguide structure, are etched away by HF. Therefore, the first and second waveguides form a suspended waveguide, and finally, the photoresist is removed.

[0091] The optical waveguide sensor provided in this embodiment of the invention features a grooved design in the sensing waveguide structure of the sensing arm, where the first and second waveguides are positioned within the groove. This grooved waveguide structure maximizes the evanescent field confinement factor of the cladding. Furthermore, the concentration of the analyte gas is analyzed by examining the interference results with the optical signal in the reference arm, thereby improving the detection accuracy of the analyte gas.

[0092] After the interference module is fabricated, the control coupling module is connected to the interference module to realize the fabrication of the optical waveguide sensor.

[0093] Based on the same inventive concept, this invention also provides an optical waveguide sensing device. Figure 13 This is a schematic diagram of the structure of an optical waveguide sensing device provided in an embodiment of the present invention, as shown below. Figure 13As shown, the optical waveguide sensing device 1 includes the optical waveguide sensor 10 and laser 20 described in any of the above embodiments. The laser 20 is connected to the first coupler 210. Therefore, the optical waveguide sensing device 1 provided in the embodiments of the present invention has the corresponding beneficial effects in the above embodiments, which will not be repeated here.

[0094] Based on the same inventive concept, embodiments of the present invention also provide a detection method for an optical waveguide sensing device. Figure 14 This is a flowchart of a detection method for an optical waveguide sensing device provided in an embodiment of the present invention, referred to as [reference]. Figure 13 and Figure 14 As shown, the preparation method includes:

[0095] S310, control the laser to input its light beam to the first coupler, and input the light beam to the sensing arm and the reference arm through the first output terminal and the second output terminal of the first coupler.

[0096] S320, controlling the interaction between the gas to be measured and light in the sensing waveguide structure.

[0097] S330, Calculate the phase difference between the light transmitted from the reference arm to the second coupler and the light transmitted from the sensor to the second coupler.

[0098] S340. Determine the concentration of the gas to be measured based on the phase difference.

[0099] Among them, reference Figure 13 As shown, in the interference module 200, the length of the sensing arm 210 is L1, and the length of the reference arm 220 is L2. The laser 20 emits a probe light I0, which is split into two independent beams after passing through the first coupler 210. These are the signal light I1 transmitted in the sensing arm 210 and the reference light I2 transmitted in the reference arm 220. After the interaction between the sensing arm 210 and the gas to be measured, the coherent light transmitted by the reference arm 220 and the signal light I1 are combined and interfered with each other in the second coupler 220. The output light intensity at the output port 220C of the second coupler 220 is I3, and the output light intensity at the output port 220D of the second coupler 220 is I3.

[0100] ;

[0101] ;

[0102] in: ΔL is the phase difference during the interference of two coherent beams, ΔL is the length difference between L1 and L2, n0 is the refractive index of the waveguide structure, and λ is the wavelength of the probe light. From the above formula, it can be seen that the energy output spectrum functions of output ports 220C and 220D are complementary and are periodic cosine functions with respect to Δλ.

[0103] When the gas to be measured is distributed on the sensing arm 210, specifically within the gaps of the slot waveguides in the sensing arm 210 (the gaps between the first waveguide 213a and the second waveguide 213b), the gas interacts fully with the light field within these gaps. This causes a change in the refractive index along this transmission path, resulting in a change in the optical path length of the signal light I1 transmitted in the sensing arm 210. Consequently, this alters the phase difference φ during the interference of the two coherent beams from the reference arm 220 and the sensing arm 210. This phase difference information is reflected in the change in the output light intensity. By simply observing the change in the output signal intensity, the change in the optical signal within the sensing arm 210 can be determined, allowing for the demodulation of the measured parameters of the gas. Optionally, the measured parameters can be the concentrations of gases such as CO2, NH3, and CH4. Optical waveguide sensing devices can be used in various fields, including biomedicine, environmental monitoring, and disaster early warning.

[0104] Optionally, the laser outputs a laser beam with a center wavelength of 2334 nm. This beam is split into a reference beam, which propagates in the reference arm, and a sensing beam, which propagates in the sensing arm, through a first coupler. The beams then interfere in a second coupler and are subsequently output through the output port of the second coupler. The optical waveguide sensing device may further include a first photodetector and / or a second photodetector, with the first photodetector connected to one output port of the second coupler (reference...). Figure 13 Couple the output port (reference 220C) to the 220C. Figure 13 The beam signal output from the 220C is converted into a first electrical signal, and the second photodetector is connected to another output port of the second coupler (reference). Figure 13 Couple the output port (reference 220D) to the 220D. Figure 13 The beam signal output by the 220D optical waveguide sensor is converted into a second electrical signal. The data acquisition device and data processor are electrically connected to the first and second photodetectors. Based on the intensity change of the first or second electrical signal and the Lambert-Beer law, the concentration of the detected gas in the environment can be obtained. Optionally, the optical waveguide sensing device includes a first photodetector and a second photodetector, with one detector serving as the data source and the other used for inspection and calibration.

[0105] Furthermore, based on the intensity changes of the first and / or second electrical signals (the difference in light intensity when there is no gas to be measured and when there is gas to be measured), the phase change (phase difference Δt) between the sensing arm and the reference arm can be calculated. The relationship between Δt and the concentration of the gas to be measured conforms to the Lambert-Beer law and has a definite curvilinear relationship. This ensures the stability and reliability of the detection of the gas to be measured using an optical waveguide sensing device.

[0106] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. An optical waveguide sensor, characterized in that, Includes coupling modules and interference modules; The coupling module includes a first coupler and a second coupler, and the interference module is located between the first coupler and the second coupler; The interference module includes a sensing arm and a reference arm; The first coupler includes a first output terminal and a second output terminal, the first output terminal being connected to a first end of the sensing arm and the second output terminal being connected to a first end of the reference arm; the second coupler includes a first input terminal and a second input terminal, the first input terminal being connected to a second end of the sensing arm and the second input terminal being connected to a second end of the reference arm. The sensing arm includes a first nonlinear gradient waveguide structure, a first mode-spot conversion waveguide structure, a sensing waveguide structure, a second mode-spot conversion waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially and adjacently. The first nonlinear gradient waveguide structure is close to the first end of the sensing arm. The first mode-spot conversion waveguide structure is located on the side of the first nonlinear gradient waveguide structure away from the first end of the sensing arm. The sensing waveguide structure is located on the side of the first mode-spot conversion waveguide structure away from the first nonlinear gradient waveguide structure. The second mode-spot conversion waveguide structure is located on the side of the sensing waveguide structure away from the first mode-spot conversion waveguide structure. The second nonlinear gradient waveguide structure is located on the side of the second mode-spot conversion waveguide structure away from the sensing waveguide structure. The second nonlinear gradient waveguide structure is close to the second end of the sensing arm.

2. The optical waveguide sensor according to claim 1, characterized in that, The optical waveguide sensor includes a substrate and a cladding layer. The cladding layer includes a first cladding layer and a second cladding layer. The first cladding layer is located on one side of the substrate, and the second cladding layer is located on the side of the first cladding layer away from the substrate. The first cladding layer includes a first groove penetrating the first cladding layer, and the second cladding layer includes a second groove penetrating the second cladding layer. The orthographic projection of the first groove onto the substrate overlaps with the orthographic projection of the second groove onto the substrate. Along the thickness direction of the substrate, the reference arm, the first nonlinear gradient waveguide structure, the first mode-spot conversion waveguide structure, the second mode-spot conversion waveguide structure, and the second nonlinear gradient waveguide structure are located between the first cladding and the second cladding. Along the direction from the first coupler to the second coupler, the projection of the sensing waveguide structure at least partially overlaps with the projection of the first mode-spot conversion waveguide structure; the orthographic projection of the sensing waveguide structure onto the substrate at least partially overlaps with the orthographic projection of the first groove onto the substrate. The sensing waveguide structure includes a first waveguide and a second waveguide. A first end of the first waveguide is connected to a first mode-spot conversion waveguide structure, and a first end of the second waveguide is connected to the first mode-spot conversion waveguide structure. A second end of the first waveguide is connected to the second mode-spot conversion waveguide structure, and a second end of the second waveguide is connected to the second mode-spot conversion waveguide structure.

3. The optical waveguide sensor according to claim 2, characterized in that, The substrate is made of silicon oxide, the first waveguide is made of silicon, and the second waveguide is made of silicon.

4. The waveguide sensor according to claim 2, characterized in that, Along the first direction, the gap between the first waveguide and the second waveguide is d, where 0.1 micrometers ≤ d ≤ 0.3 micrometers, and the first direction is perpendicular to the transmission direction of the optical waveguide in the sensing waveguide structure.

5. The optical waveguide sensor according to claim 1, characterized in that, Along the direction from the first coupler to the second coupler, the length of the first nonlinear gradient waveguide structure is L1, the length of the first mode-spot conversion waveguide structure is L2, the length of the sensing waveguide structure is L3, the length of the second mode-spot conversion waveguide structure is L4, and the length of the second nonlinear gradient waveguide structure is L5. Along a direction perpendicular to the first coupler pointing to the second coupler, the width of the first nonlinear tapered waveguide structure away from the first mode-spot conversion waveguide structure is W1; the width of the first nonlinear tapered waveguide structure closer to the first mode-spot conversion waveguide structure is W2; the width of the first mode-spot conversion waveguide structure closer to the first nonlinear tapered waveguide structure is W3; the width of the first mode-spot conversion waveguide structure closer to the sensing waveguide structure is W4; the width of the sensing waveguide structure is W5; the width of the second mode-spot conversion waveguide structure closer to the sensing waveguide structure is W6; the width of the second mode-spot conversion waveguide structure closer to the second nonlinear tapered waveguide structure is W7; the width of the second nonlinear tapered waveguide structure closer to the second mode-spot conversion waveguide structure is W8; and the width of the second nonlinear tapered waveguide structure away from the second mode-spot conversion waveguide structure is W9. Wherein: 500 micrometers ≤ L1 ≤ 700 micrometers, 30 micrometers ≤ L2 ≤ 70 micrometers, 100 micrometers ≤ L3 ≤ 300 micrometers; 30 micrometers ≤ L4 ≤ 70 micrometers, 500 micrometers ≤ L5 ≤ 700 micrometers; 0.1 μm ≤ W1 ≤ 0.5 μm, 0.5 μm ≤ W2 ≤ 1.0 μm, 0.5 μm ≤ W3 ≤ 1.0 μm, 1.0 μm ≤ W4 ≤ 1.5 μm, 1.0 μm ≤ W5 ≤ 1.5 μm, 1.0 μm ≤ W6 ≤ 1.5 μm, 0.5 μm ≤ W7 ≤ 1.0 μm, 0.5 μm ≤ W8 ≤ 1.0 μm, 0.1 μm ≤ W9 ≤ 0.5 μm.

6. The optical waveguide sensor according to claim 1, characterized in that, The sensing waveguide structure includes a linear waveguide structure or a curved waveguide structure.

7. A method for fabricating an optical waveguide sensor, used to fabricate the optical waveguide sensor according to any one of claims 1-6, characterized in that, The preparation method includes: An interferometric module is fabricated, comprising a sensing arm and a reference arm. The sensing arm includes a first nonlinear gradient waveguide structure, a mode conversion waveguide structure, a sensing waveguide structure, and a second nonlinear gradient waveguide structure arranged sequentially adjacent to each other. The first nonlinear gradient waveguide structure is located near a first end of the sensing arm. The first mode conversion waveguide structure is located on the side of the first nonlinear gradient waveguide structure away from the first end of the sensing arm. The sensing waveguide structure is located on the side of the first mode conversion waveguide structure away from the first nonlinear gradient waveguide structure. The second mode conversion waveguide structure is located on the side of the sensing waveguide structure away from the first mode conversion waveguide structure. The second nonlinear gradient waveguide structure is located on the side of the second mode conversion waveguide structure away from the sensing waveguide structure, and the second nonlinear gradient waveguide structure is located near a second end of the sensing arm. The control coupling module is connected to the interference module; the first coupler includes a first output terminal and a second output terminal, the first output terminal is connected to the first end of the sensing arm, and the second output terminal is connected to the first end of the reference arm; the second coupler includes a first input terminal and a second input terminal, the first input terminal is connected to the second end of the sensing arm, and the second input terminal is connected to the second end of the reference arm.

8. The preparation method according to claim 7, characterized in that, The interference preparation module includes: Provide a substrate and a first cladding layer; A waveguide structure layer is deposited on the side of the first cladding layer away from the substrate; The waveguide structure layer is patterned, and the reference arm, the first nonlinear gradient waveguide structure, the first mode-spot conversion waveguide structure, the sensing waveguide structure, the second mode-spot conversion waveguide structure, and the second nonlinear gradient waveguide structure are fabricated. The sensing waveguide structure includes a first waveguide and a second waveguide. A first end of the first waveguide is connected to the first mode-spot conversion waveguide structure, and a first end of the second waveguide is connected to the first mode-spot conversion waveguide structure. A second end of the first waveguide is connected to the second mode-spot conversion waveguide structure, and a second end of the second waveguide is connected to the second mode-spot conversion waveguide structure. A second cladding is prepared on the side of the waveguide structure away from the first cladding, and the second cladding covers the waveguide structure; The first cladding layer and the second cladding layer are patterned, and a first groove and a second groove are prepared; wherein the first groove penetrates the first cladding layer, the second groove penetrates the second cladding layer, the orthographic projection of the first groove onto the substrate overlaps with the orthographic projection of the second groove onto the substrate, and the orthographic projection of the sensing waveguide structure onto the substrate at least partially overlaps with the orthographic projection of the first groove onto the substrate.

9. An optical waveguide sensing device, characterized in that, It includes the optical waveguide sensor and laser as described in claims 1-6, wherein the laser is connected to the input end of the first coupler.

10. A detection method for an optical waveguide sensing device, characterized in that, Including the optical waveguide sensing device of claim 9, the detection method includes: The laser beam is controlled to be input to the first coupler, and the beam is input to the sensing arm and the reference arm through the first output terminal and the second output terminal of the first coupler; The interaction between the gas to be measured and the light is controlled within the sensing waveguide structure; Calculate the phase difference between the light transmitted from the reference arm to the second coupler and the light transmitted from the sensor to the second coupler; The concentration of the gas to be tested is determined based on the phase difference.

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