A dual-mode interferometric sensor based on selective mode control

Abstract

The application provides a dual-mode interference sensor based on selective mode regulation, which comprises a dual-mode waveguide (2), and a covering layer (3) is arranged in the middle position of the upper surface of the dual-mode waveguide (2) or on both sides of the upper surface; the sensitivity of the dual-mode waveguide detection can be improved by changing the width of the covering layer (3). The dual-mode interference sensor has the advantages of the simple structure of the single channel, compactness, easy integration, applicability to multiplexing and the like, and meanwhile, the optical path difference change of the two modes in the dual-mode waveguide is increased to improve the sensitivity.

Description

Technical Field

[0001] This invention relates to the field of sensors, and more particularly to a dual-mode interferometric sensor based on selective mode modulation. Background Technology

[0002] Optical sensors can be used for rapid health assessment, on-site disease diagnosis, and rapid detection of environmental pollution. Integrated micro / nano optical sensors based on refractive index detection technology offer advantages such as high sensitivity, low cost, label-free operation, large-scale integration, and low-cost mass production. Typical sensor structures include Mach-Zehnder interferometers, microring resonators, and photonic crystal resonators. While these devices are relatively complex and achieve high sensitivity, their small effective sensing area results in long detection times at low concentrations and poor repeatability, limiting their practical application. In contrast, sensors based on dual-mode interferometry not only offer high sensitivity but also feature a simple, single-channel, compact structure that is easy to integrate, making them one of the most promising integrated optical multiplexed analytical biosensors.

[0003] In recent years, researchers have mainly employed three methods to improve the sensitivity of dual-mode waveguide detection. The first method uses polymer materials as the sensing layer of a dual-mode interferometer. The selected polymer material can excite first-order modes within a narrow waveguide. In a narrow waveguide, the transverse first-order mode exhibits a strong evanescent field on both sides, resulting in stronger interaction with the analyte solution and thus improving sensor sensitivity. The second method uses ridge waveguides as the sensing waveguide, employing a vertical fundamental mode and first-order modes for sensing. The tail of the vertical first-order mode effectively interacts with the analyte solution, further enhancing sensor sensitivity. The third method uses micro / nano structures (such as holes, gaps, or subwavelength structures) to alter the light field distribution of the modes in the sensing layer, thereby enhancing the interaction between light and matter and improving sensor sensitivity.

[0004] The first type of sensor, which uses polymer materials, is incompatible with mainstream optical chip processing technology and is not suitable for large-scale manufacturing. The second type of method requires etching ridge waveguides downwards during manufacturing, making the process more complex, and the structure generally has a large size to achieve high sensitivity. The third type of method not only has a complex manufacturing process and small structural tolerance, but also the micro-nano structure has many uneven defects on its surface after etching and other processing techniques, which reduces the effective sensing area and leads to greater uncertainty in the interaction between the sensor surface and biomolecules, thus affecting the reliability of the detection results. Summary of the Invention

[0005] This invention provides a dual-mode interferometric sensor based on selective mode modulation, comprising a dual-mode waveguide, wherein a cover layer is disposed at the middle position or both sides of the upper surface of the dual-mode waveguide, and the sensitivity of dual-mode waveguide detection can be improved by changing the width of the cover layer.

[0006] As a further improvement of the present invention, when the capping layer is provided at the middle position of the upper surface of the dual-mode waveguide, the solution to be tested is located on both sides of the capping layer. By changing the width of the capping layer, the effective refractive index of the fundamental mode and the first-order mode under different capping layer widths can be obtained, and thus the change of phase sensitivity with the change of the capping layer width can be obtained.

[0007] As a further improvement of the present invention, the fundamental mode and the first-order mode can be a transverse electric mode TE or a transverse magnetic mode TM.

[0008] As a further improvement of the present invention, when the capping layer is disposed at the middle position of the upper surface of the dual-mode waveguide and the solution to be tested is located on both sides of the capping layer, the effective refractive index of the fundamental mode and the first-order mode in the dual-mode waveguide under different capping layer widths is obtained by using a finite difference eigenmode solver.

[0009] As a further improvement of the present invention, when the covering layer is disposed at the middle position of the upper surface of the dual-mode waveguide, and the fundamental mode and the first-order mode in the dual-mode waveguide are in TM mode, the waveguide width is fixed at 930nm.

[0010] As a further improvement of the present invention, when the cladding layer is disposed at the middle position of the upper surface of the dual-mode waveguide, and when the fundamental mode and the first-order mode in the dual-mode waveguide are TM modes, the phase sensitivity is as high as 201.4πrad / RIU when the width of the cladding layer is 480nm.

[0011] As a further improvement of the present invention, when the capping layer is disposed on both sides of the upper surface of the dual-mode waveguide, the solution to be tested is located between the two capping layers.

[0012] As a further improvement of the present invention, the dual-mode interferometric sensor further includes a single-mode waveguide, with the single-mode waveguide disposed before and after the dual-mode waveguide, and the dual-mode waveguide being connected to the single-mode waveguide before and after the dual-mode waveguide.

[0013] The beneficial effects of the present invention are: the dual-mode interferometric sensor of the present invention retains the advantages of the single-channel dual-mode waveguide sensor, such as simple structure, compactness, easy integration, and suitability for multiplexing, while increasing the optical path difference between the two modes in the dual-mode waveguide to improve sensitivity. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the covered dual-mode interferometric biosensor of the present invention;

[0015] Figure 2 This is a cross-sectional view of the dual-mode interferometric biosensor of the present invention, with a covering layer disposed in the middle of the upper surface;

[0016] Figure 3This is a cross-sectional view of the dual-mode interferometric biosensor of the present invention, which has a covering layer on both sides of its upper surface;

[0017] Figure 4 This is a schematic diagram illustrating the change in phase sensitivity of the present invention with varying coverage width;

[0018] Figure 5 This is a schematic diagram of the phase change of the output spectrum of the present invention. Detailed Implementation

[0019] This invention discloses a dual-mode interferometric sensor based on selective mode modulation, including a dual-mode waveguide 2. A cover layer 3 is provided at the middle position or both sides of the upper surface of the dual-mode waveguide 2. By changing the width of the cover layer 3, the sensitivity of the dual-mode waveguide detection can be improved.

[0020] When the capping layer 3 is disposed at the middle position of the upper surface of the dual-mode waveguide 2, the solution to be tested 4 is located on both sides of the capping layer 3. By changing the width of the capping layer 3, the effective refractive index of the fundamental mode and the first-order mode in the dual-mode waveguide 2 under different widths of the capping layer 3 can be obtained, and thus the change of phase sensitivity with the change of the width of the capping layer 3 can be obtained.

[0021] The fundamental mode and the first-order mode can be either a transverse electric mode (TE) or a transverse magnetic mode (TM).

[0022] When the capping layer 3 is disposed at the middle position of the upper surface of the dual-mode waveguide 2, and the solution to be tested 4 is located on both sides of the capping layer 3, the effective refractive indices of the fundamental mode and the first-order mode under different widths of the capping layer 3 are obtained by using a finite difference eigenmode solver.

[0023] When the cladding layer 3 is disposed at the middle position of the upper surface of the dual-mode waveguide 2, and the fundamental mode and the first-order mode are in TM mode, the fixed waveguide width is 930nm.

[0024] When the cladding layer 3 is disposed at the middle position of the upper surface of the dual-mode waveguide 2, and the fundamental mode and the first-order mode are in TM mode, the phase sensitivity is 201.4πrad / RIU when the width of the cladding layer 3 is 480nm.

[0025] When the cover layer 3 is disposed on both sides of the upper surface of the dual-mode waveguide 2, the solution to be tested 4 is located between the two cover layers 3.

[0026] The dual-mode interferometric sensor also includes a single-mode waveguide 1. The single-mode waveguide 1 is disposed before and after the dual-mode waveguide 2, and the dual-mode waveguide 2 is connected to the single-mode waveguide 1 before and after.

[0027] The present invention discloses the working principle of a dual-mode interferometric sensor based on selective mode modulation:

[0028] The dual-mode interferometer-based sensor consists of a single-mode region and a dual-mode region supporting both the fundamental and first-order modes. The two modes have different effective refractive indices and phase velocities. Compared to the fundamental mode, the first-order mode exhibits a stronger evanescent field due to its interaction with external matter. Therefore, when the analyte is present in the evanescent fields of both the fundamental and first-order modes, changes in the refractive index of the sensor surface cause different changes in the effective refractive indices of the two modes. Sensing of the analyte is achieved by monitoring the phase change of the output dual-mode interferometric spectrum. Phase sensitivity S phase The ratio of the phase change to the refractive index change is given by the following formula:

[0029]

[0030] in Output interference spectrum phase change, δn ex It is the change in the refractive index of the sensing surface. and denoted by , respectively, the effective refractive index difference between the fundamental mode and the first-order mode, and L is the length of the two-mode waveguide.

[0031] As can be seen from the above formula, in a dual-mode interferometric sensor, the phase sensitivity can be improved by increasing the length of the dual-mode waveguide, but this also means that the waveguide size becomes larger.

[0032] The method proposed in this invention, which utilizes the middle or both sides of the upper surface of a dual-mode waveguide for coverage, can increase the rate of change of the effective refractive index difference between the two modes, thereby generating a larger phase change. Compared with increasing the length of the dual-mode waveguide, this method not only improves sensitivity but also retains the advantages of the dual-mode waveguide's simplicity, compactness, and ease of manufacture.

[0033] To verify the effectiveness of this method, the finite-difference time-domain method is used to simulate and verify the proposed method.

[0034] Figure 1 This is a schematic diagram of a covered dual-mode interferometric biosensor. Figure 2 A cross-sectional view showing the covering layer 3 in the middle of the upper surface is provided. This structure is defined as structure A. Figure 3 A cross-sectional view of the cladding layer 3 on both sides of the upper surface is shown, and this structure is defined as structure B. Taking structure A as an example, with the waveguide width fixed at 930 nm, the width of the cladding layer 3 is varied. The effective refractive indices of TM0 and TM1 under different cladding layer 3 widths are obtained using a finite difference eigenmode solver, and then the change in phase sensitivity with the change of cladding layer 3 width is obtained as follows: Figure 4As shown in the figure, the dashed line represents the sensor's sensitivity reference without the cover layer 3. The solid line indicates that changing the width of the cover layer 3 effectively improves the sensor's phase sensitivity. When the width of the cover layer 3 is 480 nm, the phase sensitivity reaches a maximum of 201.4 π rad / RIU, an improvement of 109.58% compared to when no cover is applied.

[0035] Finally, by varying the refractive indices of the cladding of the dual-mode interferometer from 1.311 to 1.329 to simulate solutions of different concentrations, and with a sensing region length of 500 μm, TM polarized light was input at the input end of single-mode waveguide 1 to obtain the interference spectrum of the dual-mode interferometer. The phase information of the spectrum was extracted using Fast Fourier Transform, and the phase change of the output spectrum with varying cladding refractive index was obtained as follows: Figure 5 The phase sensitivity is 558.08 rad / RIU.

[0036] The beneficial effects of the present invention are as follows: The dual-mode interferometric sensor of the present invention retains the advantages of the single-channel dual-mode waveguide sensor, such as simple structure, compactness, easy integration, and suitability for multiplexing, while increasing the optical path difference between the two modes in the dual-mode waveguide to improve sensitivity.

[0037] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A dual-mode interferometric sensor based on selective mode modulation, characterized in that: Includes a dual-mode waveguide (2), wherein a cover layer (3) is provided at the middle position or both sides of the upper surface of the dual-mode waveguide (2). By changing the width of the cover layer (3), the sensitivity of dual-mode waveguide detection can be improved. When the cover layer (3) is provided at the middle position of the upper surface of the dual-mode waveguide (2), the solution to be tested (4) is located on both sides of the cover layer (3); When the capping layer (3) is set on both sides of the upper surface of the dual-mode waveguide (2), the solution to be tested (4) is located between the two capping layers (3); By changing the width of the cladding layer (3), the effective refractive index of the fundamental mode and the first-order mode in the dual-mode waveguide (2) is obtained under different widths of the cladding layer (3), and then the change in phase sensitivity with the change of the width of the cladding layer (3) is obtained.

2. The dual-mode interferometric sensor according to claim 1, characterized in that: The fundamental mode and the first-order mode are either transverse electric mode TE or transverse magnetic mode TM.

3. The dual-mode interferometric sensor according to claim 1, characterized in that: When the capping layer (3) is provided at the middle position of the upper surface of the dual-mode waveguide (2), and the solution to be tested (4) is located on both sides of the capping layer (3), the effective refractive index of the fundamental mode and the first-order mode in the dual-mode waveguide (2) under different widths of the capping layer (3) is obtained by using a finite difference eigenmode solver.

4. The dual-mode interferometric sensor according to claim 3, characterized in that: When the cover layer (3) is set at the middle position of the upper surface of the dual-mode waveguide (2), and the fundamental mode and the first-order mode in the dual-mode waveguide (2) are TM modes, the fixed waveguide width is 930nm.

5. The dual-mode interferometric sensor according to claim 4, characterized in that: When the cover layer (3) is provided at the middle position of the upper surface of the dual-mode waveguide (2), and the fundamental mode and the first-order mode in the dual-mode waveguide (2) are TM modes, the phase sensitivity is 201.4π rad / RIU when the width of the cover layer (3) is 480nm.

6. The dual-mode interferometric sensor according to claim 1, characterized in that: The dual-mode interferometric sensor also includes a single-mode waveguide (1), with the single-mode waveguide (1) disposed before and after the dual-mode waveguide (2), and the dual-mode waveguide (2) is connected to the single-mode waveguide (1) before and after.

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