A long period waveguide grating type sensor and a manufacturing method thereof
By fabricating a long-period waveguide grating sensor with a waveguide core layer of sinusoidally varying radius on a glass substrate, the problem of insufficient sensitivity in existing gas sensors has been solved, achieving high-sensitivity gas detection at a low cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JINHUA INSTITUTE OF ZHEJIANG UNIVERSITY
- Filing Date
- 2024-10-09
- Publication Date
- 2026-06-02
AI Technical Summary
Existing gas sensors have shortcomings in terms of sensitivity, selectivity, and lifespan, and are greatly affected by environmental factors, especially infrared gas measurement sensors, whose sensitivity is greatly affected by temperature and humidity.
A long-period waveguide grating sensor is designed to utilize the high sensitivity of the absorption peak wavelength in the valley of the transmission spectrum to the refractive index disturbance of the external environment. By fabricating a waveguide core layer with a sinusoidally periodically varying radius on a glass substrate, and combining ion exchange and electric field-assisted exchange processes to form a buried waveguide core layer, high-sensitivity detection of gas is achieved.
It achieves high-sensitivity and rapid measurement of gases. The sensor is simple to manufacture and inexpensive, with a sensitivity of several thousand nanometers per RIU.
Smart Images
Figure CN119438135B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of integrated optics, and particularly relates to a glass-based graded long-period waveguide grating sensor and its manufacturing method. Background Technology
[0002] A gas sensor is an electronic device capable of detecting and measuring the composition or concentration of a gas. It is typically used to detect the presence or concentration changes of a specific gas and convert this information into an electrical signal output. Gas sensors have a wide range of applications, from detecting gas leaks in industrial environments to monitoring air quality in everyday life.
[0003] Currently, the gas sensors available on the market mainly fall into three categories: Electrochemical sensors generate current through a chemical reaction between the gas and electrodes, used to detect gases such as oxygen and carbon monoxide. They require initialization start-up time, have a short lifespan (2-3 years), good sensitivity and selectivity, and moderate power consumption and cost. Catalytic combustion sensors detect the presence of combustible gases through combustion reactions, commonly used in industrial safety monitoring. They have a small detection range (0-4%), are prone to causing secondary disasters, have high power consumption, and a short lifespan (2-3 years), but are widely used for detecting all combustible gases. MEMS oxide sensors detect gases by detecting changes in the conductivity of oxide materials in a specific gas environment. They have a long start-up time of several minutes, poor sensitivity and selectivity, high power consumption, and low cost.
[0004] In addition, infrared gas measurement sensing is a commonly used optical gas sensing technology. However, the sensitivity of the sensor is greatly affected by environmental factors such as temperature and humidity, and the gas molecules being measured must have corresponding infrared absorption capabilities.
[0005] Long-period gratings are periodic structures etched onto the core of optical fibers, possessing relatively long grating periods (typically ranging from 100 micrometers to several hundred micrometers). This periodic structure couples guided-mode light from the fiber core to the cladding mode, resulting in resonant losses within a specific wavelength range and causing spectral attenuation. These resonant wavelengths are highly sensitive to changes in the refractive index of the surrounding environment, and therefore can be used for gas detection. Summary of the Invention
[0006] This invention addresses the aforementioned problems by proposing a long-period waveguide grating sensor and its manufacturing method. The design concept is to utilize the high sensitivity of the absorption peak wavelength in the valley of the transmission spectrum to the refractive index disturbance of the external environment, thereby achieving rapid measurement of gases with high sensitivity.
[0007] The long-period waveguide grating type sensor includes a glass substrate 1, a cladding layer 2, a waveguide core layer 3, a first cylindrical core layer 4, a second cylindrical core layer 5, and a long-period grating core layer 6;
[0008] The glass substrate 1 has a linearly extending waveguide core layer 3, and a cladding layer 2 is provided around the waveguide core layer 3. The extension direction of the waveguide core layer 3 is defined as the front-to-back direction. The waveguide core layer 3 is composed of a first cylindrical core layer 4, a long-period grating core layer 6, and a second cylindrical core layer 5, which are arranged sequentially from front to back. The radius of the long-period grating core layer 6 changes sinusoidally from front to back. The first cylindrical core layer 4 is the optical signal input end, and the second cylindrical core layer 5 is the optical signal output end.
[0009] More specifically, the radius of waveguide core layer 3 ranges from 3.0 to 5.0 μm, and the length ranges from 100 to 2500 μm.
[0010] More specifically, the refractive index of waveguide core layer 3 has a Gaussian distribution, and the difference between its refractive index and that of the substrate is 0.005 to 0.010.
[0011] More specifically, the thickness of cladding 2 is 0–2 μm.
[0012] More specifically, the front end radius of the long-period grating core layer 6 is the same as that of the first cylindrical core layer (4), which is 3.5 μm; the length of the long-period grating core layer 6 is 1500 to 4000 μm.
[0013] More specifically, the radius of the narrowest part of the long-period grating core layer 6 is 3.0-3.5 μm, the radius of the widest part is 3.5-4.0 μm, and the variation period is 50-500 μm.
[0014] The manufacturing method of a long-period waveguide grating sensor includes the following steps:
[0015] 1) Coating, photolithography, and etching are performed on the upper surface of glass substrate 1;
[0016] 2) The waveguide pattern that varies sinusoidally from front to back is transferred to the mask previously deposited on the glass substrate 1 and used as a blocking film for the optical waveguide during the ion exchange process.
[0017] 3) The glass substrate 1 with the mask is immersed in a low-concentration silver ion exchange molten salt for heat exchange, so that a surface optical waveguide is formed in the waveguide pattern on the mask;
[0018] 4) Add a first electrode and a second electrode to the front and back sides of the glass substrate 1, and perform power plant auxiliary switching treatment so that the optical waveguide is buried into the glass substrate under the action of the electric field to form a buried waveguide core layer 3. The glass substrate 1 left above the waveguide core layer 3 due to burial constitutes the cladding layer 2.
[0019] When light passes through a long-period waveguide grating, coupling occurs between the two waveguide propagation modes. The use of long-period waveguide gratings for refractive index sensing is primarily based on the observable shift in the wavelength of their coupling absorption peak as the refractive index of the external environment changes. According to the phase-matching formula, the wavelength of the absorption peak in the transmission spectrum is:
[0020] λ res =(N0-N m )Λ
[0021] λ res For the absorption peak wavelength, N0 and N m Here, Λ represents the effective refractive index of the core layer's fundamental mode and higher-order modes, respectively. Λ is the sinusoidal period of the long-period waveguide grating. Changes in the refractive index of the external environment affect the effective refractive index and field distribution of higher-order modes, thus causing corresponding changes in the resonant wavelength. Therefore, the effective refractive index of higher-order modes can be written as:
[0022] N m =N m (n ex )
[0023] Where n ex The refractive index is the refractive index of the external environment. Normally, the period of the core layer fundamental mode and the grating is not affected by changes in the external refractive index; the change in external refractive index is Δn. ex The shift Δλ of the corresponding coupling absorption peak wavelength res Can be written as:
[0024]
[0025] When the concentration of external gas changes, the refractive index of the external environment changes. By monitoring the wavelength shift of the absorption peaks and troughs in the spectrum, information about the change in the concentration of external gas can be obtained, thus achieving a detection effect.
[0026] The technical advantages of this invention are: the waveguide core layer with a sinusoidally periodically varying radius enhances its sensitivity as a sensor, and the sensor is simple to manufacture and inexpensive. Attached Figure Description
[0027] Figure 1 This is a structural diagram of the long-period waveguide grating sensor of the present invention.
[0028] Figure 2 This is a schematic diagram of the cross-section of the long-period waveguide grating sensor of the present invention.
[0029] Figure 3 This is a schematic diagram of the core layer of the long-period waveguide grating sensor of the present invention.
[0030] Figure 4This is the transmission spectrum of the long-period waveguide grating sensor prepared with the parameters of Example 2, at 1450-1650 nm in the external refractive index range of 1.0000-1.0003.
[0031] Figure 5 This is a graph showing the relationship between the absorption peak wavelength of the long-period waveguide grating sensor prepared according to the parameters of Example 2 and the external refractive index in the range of 1.0000-1.0003.
[0032] Figure 6 This is the transmission spectrum of the long-period waveguide grating sensor prepared with the parameters of Example 3, at 1450-1650 nm in the external refractive index range of 1.0000-1.0003.
[0033] Figure 7 This is a graph showing the relationship between the absorption peak wavelength and the external refractive index of the long-period waveguide grating sensor prepared with the parameters of Example 3 in the external refractive index range of 1.0000-1.0003.
[0034] Figure 8 This is the transmission spectrum of the long-period waveguide grating sensor prepared with the parameters of Example 4, at 1450-1650 nm in the external refractive index range of 1.0000-1.0003.
[0035] Figure 9 This is a graph showing the relationship between the absorption peak wavelength and the external refractive index of the long-period waveguide grating sensor prepared with the parameters of Example 4 in the external refractive index range of 1.0000-1.0003.
[0036] Figure 10 This is the transmission spectrum of the long-period waveguide grating sensor prepared with the parameters of Example 5, at 1450-1650 nm in the external refractive index range of 1.0000-1.0003.
[0037] Figure 11 This is a graph showing the relationship between the absorption peak wavelength and the external refractive index of the long-period waveguide grating sensor prepared with the parameters of Example 5 in the external refractive index range of 1.0000-1.0003. Detailed Implementation
[0038] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.
[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.
[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0044] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments.
[0045] Example 1
[0046] according to Figure 1 , Figure 2 The long-period waveguide grating type sensor includes a glass substrate 1, a cladding layer 2, a waveguide core layer 3, a first cylindrical core layer 4, a second cylindrical core layer 5, and a long-period grating core layer 6.
[0047] The glass substrate 1 has a linearly extending waveguide core layer 3, and a cladding layer 2 is provided around the waveguide core layer 3. The extension direction of the waveguide core layer 3 is defined as the front-to-back direction. The waveguide core layer 3 is composed of a first cylindrical core layer 4, a long-period grating core layer 6, and a second cylindrical core layer 5, which are arranged sequentially from front to back. The radius of the long-period grating core layer 6 changes sinusoidally from front to back. The first cylindrical core layer 4 is the optical signal input end, and the second cylindrical core layer 5 is the optical signal output end.
[0048] When light passes through a long-period waveguide grating, coupling occurs between the two waveguide propagation modes. The use of long-period waveguide gratings for refractive index sensing is primarily based on the observable shift in the wavelength of their coupling absorption peak as the refractive index of the external environment changes. According to the phase-matching formula, the wavelength of the absorption peak in the transmission spectrum is:
[0049] λ res =(N0-N m )Λ
[0050] λ res For the absorption peak wavelength, N0 and N m Here, Λ represents the effective refractive index of the core layer's fundamental mode and higher-order modes, respectively. Λ is the sinusoidal period of the long-period waveguide grating. Changes in the refractive index of the external environment affect the effective refractive index and field distribution of higher-order modes, thus causing corresponding changes in the resonant wavelength. Therefore, the effective refractive index of higher-order modes can be written as:
[0051] Nm =N m (n ex )
[0052] Where n ex The refractive index is the refractive index of the external environment. Normally, the period of the core layer fundamental mode and the grating is not affected by changes in the external refractive index; the change in external refractive index is Δn. ex The shift Δλ of the corresponding coupling absorption peak wavelength res Can be written as:
[0053]
[0054] When the concentration of external gas changes, the refractive index of the external environment changes. By monitoring the wavelength shift of the absorption peaks and troughs in the spectrum, information about the change in the concentration of external gas can be obtained, thus achieving a detection effect.
[0055] Example 2
[0056] A long-period waveguide grating type sensor based on Embodiment 1, wherein the first cylindrical core layer 4 and the second cylindrical core layer 5 have a radius of 3.5 μm and a length of 4000 μm;
[0057] The refractive index of waveguide core layer 3 exhibits a Gaussian distribution, with the difference between the peak refractive index distribution and the substrate refractive index being 0.005.
[0058] The thickness of cladding 2 is 2.0 μm;
[0059] The starting node radius of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, which is 3.5 μm, and the length is 3750 μm.
[0060] The radius of the long-period waveguide grating 6 exhibits a sinusoidal periodic variation. During the variation period, the narrowest point of the core layer radius is 3.0 μm, the widest point is 3.5 μm, and the variation period is 50 μm.
[0061] The refractive index distribution of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, and the refractive index difference between the core layer and the substrate is 0.005.
[0062] like Figure 3 , 4 As shown, this invention was simulated using Rsoft optical simulation software. The input light source was a broadband light source centered at a wavelength of 1550nm. Simulations were performed within the environmental refractive index range of 1.0000-1.0003 to obtain transmission spectra for different environments. The simulation results show that this sensor structure can achieve good sensing performance within the gas refractive index range, with a sensitivity reaching 4000nm / RIU.
[0063] Example 3
[0064] A long-period waveguide grating type sensor based on Embodiment 1, wherein the first cylindrical core layer 4 and the second cylindrical core layer 5 have a radius of 3.5 μm and a length of 2000 μm;
[0065] The refractive index of waveguide core layer 3 exhibits a Gaussian distribution, with a refractive index difference of 0.008 between the peak of the refractive index distribution and the substrate.
[0066] The thickness of cladding layer 2 is 0.5 μm;
[0067] The starting node radius of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, which is 3.5 μm, and the length is 2000 μm.
[0068] The radius of the long-period waveguide grating 6 exhibits a sinusoidal periodic variation. During the variation period, the narrowest point of the core layer radius is 3.5 μm, the widest point is 3.75 μm, and the variation period is 150 μm.
[0069] The refractive index distribution of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, and the refractive index difference between the core layer and the substrate is 0.008.
[0070] like Figure 5 , 6 As shown, this invention was simulated using Rsoft optical simulation software. The input light source was a broadband light source centered at a wavelength of 1550 nm. Simulations were performed within the environmental refractive index range of 1.0000-1.0003 to obtain transmission spectra for different environments. The simulation results show that this sensor structure can achieve good sensing performance within the gas refractive index range, with a sensitivity reaching 8032 nm / RIU.
[0071] Example 4
[0072] A long-period waveguide grating type sensor based on Embodiment 1, wherein the first cylindrical core layer 4 and the second cylindrical core layer 5 have a radius of 3.5 μm and a length of 750 μm;
[0073] The refractive index of waveguide core layer 3 exhibits a Gaussian distribution, with a refractive index difference of 0.015 between the peak of the refractive index distribution and the substrate.
[0074] The thickness of cladding 2 is 1.0 μm;
[0075] The starting node radius of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, which is 3.5 μm, and the length is 5000 μm.
[0076] The radius of the long-period waveguide grating 6 exhibits a sinusoidal periodic variation. During the variation period, the narrowest point of the core layer radius is 3.5 μm, the widest point is 4.0 μm, and the variation period is 200 μm.
[0077] The refractive index distribution of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, and the refractive index difference between the core layer and the substrate is 0.015.
[0078] like Figure 7 , 8 As shown, this invention was simulated using Rsoft optical simulation software. The input light source was a broadband light source centered at a wavelength of 1550 nm. Simulations were performed within the environmental refractive index range of 1.0000-1.0003 to obtain transmission spectra for different environments. The simulation results show that this sensor structure can achieve good sensing performance within the gas refractive index range, with a sensitivity reaching 7632 nm / RIU.
[0079] Example 5
[0080] A long-period waveguide grating type sensor based on Embodiment 1, wherein the first cylindrical core layer 4 and the second cylindrical core layer 5 have a radius of 3.5 μm and a length of 500 μm;
[0081] The refractive index of waveguide core layer 3 exhibits a Gaussian distribution, with a refractive index difference of 0.008 between the peak of the refractive index distribution and the substrate.
[0082] The thickness of cladding layer 2 is 0.5 μm;
[0083] The starting node radius of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, which is 3.5 μm, and the length is 12500 μm.
[0084] The radius of the long-period waveguide grating 6 exhibits a sinusoidal periodic variation. During the variation period, the narrowest point of the core layer radius is 3.5 μm, the widest point is 4.0 μm, and the variation period is 500 μm.
[0085] The refractive index distribution of the long-period grating core layer 6 is the same as that of the first cylindrical core layer 4, and the refractive index difference between the core layer and the substrate is 0.008.
[0086] like Figure 9 , 10 As shown, this invention was simulated using Rsoft optical simulation software. The input light source was a broadband light source centered at a wavelength of 1550 nm. Simulations were performed within the environmental refractive index range of 1.0000-1.0003 to obtain transmission spectra for different environments. The simulation results show that this sensor structure can achieve good sensing performance within the gas refractive index range, with a sensitivity reaching 4100 nm / RIU.
[0087] The technical advantages of this invention are: the waveguide core layer with a sinusoidally periodically varying radius enhances its sensitivity as a sensor, and the sensor is simple to manufacture and inexpensive.
[0088] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.
Claims
1. A long-period waveguide grating type sensor, characterized in that: It includes a glass substrate (1), a cladding (2), a waveguide core layer (3), a first cylindrical core layer (4), a second cylindrical core layer (5), and a long-period grating core layer (6). The glass substrate (1) has a waveguide core layer (3) extending in a straight line, and a cladding layer (2) is provided around the waveguide core layer (3); the extension direction of the waveguide core layer (3) is defined as the front-to-back direction, and the waveguide core layer (3) is composed of a first cylindrical core layer (4), a long-period grating core layer (6) and a second cylindrical core layer (5) from front to back. The radius of the long-period grating core layer (6) changes sinusoidally from front to back; the first cylindrical core layer (4) is the optical signal input end, and the second cylindrical core layer (5) is the optical signal output end; The waveguide core layer (3) has a radius ranging from 3.0 to 5.0 μm and a length ranging from 100 to 2500 μm; The refractive index of the waveguide core layer (3) is Gaussian distributed, and the difference between the refractive index of the core layer and the substrate is 0.005~0.
010. The narrowest radius of the long-period grating core layer (6) is 3.0-3.5 μm, the widest radius is 3.5-4.0 μm, and the variation period is 50-500 μm.
2. A long-period waveguide grating type sensor according to claim 1, characterized in that: The thickness of the cladding (2) is 0~2μm.
3. A long-period waveguide grating type sensor according to claim 1, characterized in that: The front radius of the long-period grating core layer (6) is the same as that of the first cylindrical core layer (4), which is 3.5 μm; the length of the long-period grating core layer (6) is 1500~4000 μm.
4. The manufacturing method of the long-period waveguide grating type sensor according to claim 1, comprising the following steps: 1) Coating, photolithography and etching are performed on the upper surface of the glass substrate (1); 2) The waveguide pattern that varies sinusoidally from front to back is transferred to the mask previously deposited on the glass substrate (1) and used as a blocking film for the optical waveguide during ion exchange. 3) Immerse the glass substrate (1) with the mask into a low-concentration silver ion exchange molten salt for heat exchange, so that a surface optical waveguide is formed in the waveguide pattern on the mask; 4) Add a first electrode and a second electrode to the front and back sides of the glass substrate (1) and perform electric field-assisted exchange treatment so that the optical waveguide is buried in the glass substrate under the action of the electric field to form a buried waveguide core layer (3). The glass substrate (1) left above the waveguide core layer (3) due to burial constitutes a cladding layer (2).