An alcohol detection device and method based on a width-graded double-ring microring resonator

Abstract

This invention discloses an alcohol detection chip and detection method based on a cascaded dual-ring resonator with dual-gradient curvature, belonging to the field of optical micro-nano sensing and integrated optics technology. This invention aims to solve the technical problems of low sensitivity, poor resolution, complex spectral analysis, and weak environmental adaptability in traditional micro-ring sensing devices, as well as the low detection accuracy of existing miniaturized equipment. The chip uses a silicon-based substrate and includes input and output waveguides, cascaded dual micro-rings, a coupling region, and two sets of miniature heating electrodes. The micro-rings employ dual-gradient waveguides with circular and Euler-circular curved structures for the inner and outer curves, respectively. The cascaded dual rings create a vernier effect, broadening the free spectral range. By adjusting the resonant wavelength through the heating electrodes, scanning detection is completed in the characteristic alcohol band around 1400nm, and high-precision alcohol measurement is achieved by combining transmission spectroscopy. This invention has a compact structure and low cost, and is suitable for rapid quantitative detection of alcohol in industrial monitoring, vehicle safety, food safety, and other scenarios.

Description

Technical Field

[0001] This invention relates to the fields of optical micro-nano sensing technology, integrated optical chip technology, and liquid concentration detection technology. Specifically, it relates to an alcohol concentration detection device and corresponding detection method based on a width-gradient dual-ring micro-ring resonator. Background Technology

[0002] Alcohol concentration detection has irreplaceable application value in many fields, such as the concentration detection of alcoholic beverages in food safety, the concentration monitoring of alcohol solvents in industrial production, and the detection of blood alcohol content in the medical field. Currently, traditional alcohol detection methods mainly include electrochemical methods and gas chromatography. Electrochemical methods suffer from drawbacks such as slow response speed, susceptibility to environmental temperature and humidity interference, and short lifespan. Gas chromatography methods are characterized by bulky equipment, complex operation, and high detection costs, making it difficult to meet the needs of rapid, miniaturized on-site detection.

[0003] Optical microring resonators, as a novel micro-nano sensing structure, have become a research hotspot in the field of liquid refractive index sensing due to their outstanding advantages such as small size, high sensitivity, label-free detection, and on-chip integration, and are widely used in various liquid concentration detection applications. However, existing microring resonators mostly employ single-ring, equal-width waveguide structures, which have the following technical drawbacks: First, the mode dispersion of equal-width waveguides is difficult to control, resulting in limited optical field confinement and low sensing sensitivity; second, the resonance peak modulation capability of single-ring structures is weak, and the half-width at half-maximum (FWHM) of the resonance peak is large, leading to insufficient detection resolution and making it difficult to meet the requirements for high-precision alcohol concentration detection; third, the working wavelength of traditional microrings has poor compatibility with the refractive index variation range of alcohol solutions, easily resulting in detection blind zones.

[0004] Therefore, developing a microring resonator structure and detection method that can solve the above-mentioned defects, meet the needs of alcohol detection, and has high sensitivity has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing micro-ring sensors, such as low sensitivity, poor dispersion matching, single resonance characteristics, and insufficient detection resolution. It provides an alcohol concentration detection device and method based on a width-gradient double-ring micro-ring resonator, which achieves rapid, high-precision, and label-free detection of alcohol concentration, while also having the advantages of integration and miniaturization.

[0006] To address the shortcomings of existing alcohol detection technologies, this invention provides an alcohol detection device based on a width-gradient dual-ring microring resonator. The device includes: a first microring resonator, a second microring resonator, an input waveguide, an intermediate waveguide, an output waveguide, a coupling region, a first contact electrode, a first micro heating electrode, a second contact electrode, and a second micro heating electrode.

[0007] The input waveguide is used to receive the probe optical signal, and the output waveguide is used to output the resonantly modulated optical signal. Both the input and output waveguides adopt a curved waveguide structure and are coupled to a microring resonator through a coupling region. The first microring resonator is connected to the intermediate waveguide through the coupling region, and the intermediate waveguide is then connected to the second microring resonator through the coupling region, forming a cascaded double-ring structure.

[0008] Furthermore, miniature heating electrodes are respectively disposed above the ring waveguides of the first and second micro-ring resonators. The miniature heating electrodes are connected to an external driving power supply through contact electrodes. The resonant wavelength of the micro-ring resonator is dynamically adjustable through thermal modulation. By applying thermal modulation to the micro-ring resonator through the miniature heating electrodes, the resonant wavelength can be precisely and rapidly tuned.

[0009] Furthermore, both the first and second micro-ring resonators employ a structure combining a width-gradient waveguide and a curvature-gradient bent waveguide. The inner curve of the bent waveguide is circular, while the outer curve is an Euler-circular bend. The width-gradient structure is used to control the micro-ring mode dispersion, enhance the optical field confinement capability, and reduce optical transmission loss, while also optimizing the double-ring vernier effect. The curvature-gradient structure is used to reduce waveguide bending radiation loss, improve the micro-ring quality factor, and thus enhance sensing sensitivity.

[0010] Furthermore, by optimizing the selection of the double-ring radius, waveguide width, and bending curvature, the operating wavelength of the resonator is precisely matched with the range of refractive index variation of the alcohol solution, ensuring efficient and stable alcohol concentration detection.

[0011] Furthermore, this invention employs a cascade of two micro-ring resonators with slight differences in their free spectral ranges. The transmission spectra of the two rings are superimposed to form an envelope spectrum, which significantly expands the overall effective free spectral range. Only a single envelope peak is generated over a wide wavelength range, greatly simplifying the spectral analysis process. Concentration inversion can be achieved simply by tracking a single envelope peak.

[0012] Furthermore, by adjusting the heating power of the micro-heating electrode, the resonant wavelengths of the first and second micro-ring resonators are controlled respectively, enabling continuous scanning of the resonant peak within the optimal detection band for alcohol. Whenever the resonant peak position changes by a set wavelength step, the corresponding light intensity signal is recorded by a photodetector. Finally, the complete transmittance spectrum of the test solution in the target band is reconstructed from multiple sets of light intensity data obtained through the complete scan.

[0013] Furthermore, the input light wavelength coverage is smaller than the effective free spectrum range after the double-ring cascade, in order to avoid spectral aliasing caused by the overlap of resonant modes and ensure measurement accuracy.

[0014] Furthermore, this invention achieves detection based on optical transmission spectroscopy absorption method. When the light signal emitted by the broadband light source passes through the alcohol solution to be tested, the alcohol molecules selectively absorb at a specific wavelength, and the absorption intensity follows the Lambert-Beer law. The alcohol concentration can be inverted by the change of characteristic absorption peak.

[0015] Furthermore, the input waveguide, intermediate waveguide, and output waveguide all adopt a curved waveguide structure to reduce optical transmission loss.

[0016] Based on the above structure and principle, the alcohol detection method of the present invention includes the following steps:

[0017] The first step involves applying thermal modulation to the first and second micro-ring resonators using miniature heating electrodes, and adjusting the heating power to align the double-ring resonance peaks at the starting position of the characteristic band for alcohol detection.

[0018] The second step is to connect the broadband light source to the chip's optical path. After the output single-wavelength light signal passes through the solution to be tested, the light intensity signal is collected by the photodetector to obtain the light transmittance of the solution to be tested at that wavelength.

[0019] The third step is to fine-tune the output power of the heating electrode to cause a small red shift in the double-ring resonance peak, and repeat the transmittance detection and signal acquisition steps to obtain the transmittance data for the next corresponding wavelength.

[0020] The fourth step involves adjusting the heating power sequentially to complete a full-band step scan, thereby obtaining the complete transmission spectrum of the test solution within the characteristic band of alcohol.

[0021] The fifth step is to compare the obtained transmission spectrum with the standard transmission spectra of alcohol solutions of different concentrations, and calculate the detection result of the alcohol concentration of the test solution.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) High sensitivity and high resolution: The innovative dual-ring cascaded microring resonator structure with double-gradient width curvature is adopted. By controlling the mode dispersion through width gradient and reducing bending radiation loss through curvature gradient, the optical field confinement capability is effectively enhanced and the quality factor of the resonator is improved. The vernier effect formed by the dual-ring cascade can not only greatly broaden the effective free spectrum range of the device, but also form a sharp single envelope peak in a wide band, which greatly improves the sensing sensitivity. Combined with fine wavelength step scanning, the resonant peak spacing between two adjacent scans is strictly controlled to achieve narrow-interval wavelength sampling, thereby significantly improving the detection resolution and completely solving the technical pain points of insufficient sensitivity and low resolution of traditional microring resonators.

[0024] (2) Precise alignment of working wavelength: By optimizing the selection of the radius, waveguide width and bending curvature of the double ring resonator, the working wavelength of the chip can be precisely matched with the alcohol characteristic detection wavelength, ensuring that the device works in the optimal detection range, effectively solving the problem of poor compatibility between the working wavelength of traditional micro-ring and the alcohol absorption wavelength.

[0025] (3) Label-free, real-time detection: The optical transmission spectroscopy detection principle is adopted to achieve label-free detection, which avoids the damage to the sample caused by traditional detection methods. At the same time, the response speed is fast and the alcohol concentration can be monitored online in real time.

[0026] (4) Miniaturization and low cost: The overall structure is based on the silicon-on-insulator platform, which can be integrated on the chip. It is small in size and light in weight, and is suitable for rapid on-site testing scenarios such as vehicle and portable applications. The manufacturing process is mature and does not require complex hardware equipment, which effectively reduces the testing cost and application threshold, and facilitates large-scale promotion. Attached Figure Description

[0027] Figure 1 : Overall schematic diagram of the invention,

[0028] Figure 2 : Schematic diagram of the width-gradient dual-ring micro-ring resonator of this invention.

[0029] Figure 3 The present invention provides a width-gradient dual-ring microring resonator with varying transmittance for different wavelengths of light.

[0030] Figure 4 : Schematic diagram of the testing process.

[0031] The markings in the figure are as follows: 1-Input waveguide, 2-Coupled region, 3-First micro-ring, 4-Intermediate waveguide, 5-Second micro-ring, 6-Output waveguide, 7-First contact electrode, 8-First micro-heating electrode, 9-Second contact electrode, 10-Second micro-heating electrode. Detailed Implementation

[0032] To make the objectives, features, and advantages of this disclosure more apparent and understandable, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0033] Figure 2 This illustration shows a schematic diagram of a spectral analysis chip based on a dual-ring cascaded microring resonator with a width curvature of double gradient, according to an embodiment of this disclosure. Figure 2As shown, the spectral analysis chip includes: an input waveguide, a coupling region, a first micro-ring resonator, an intermediate waveguide, a second micro-ring resonator, an output waveguide, a first contact electrode, a first micro heating electrode, a second contact electrode, and a second micro heating electrode.

[0034] In this embodiment, the optical substrate is made of silicon, with a thickness controlled between 200nm and 400nm. The silicon-based optical substrate is compatible with complementary metal-oxide-semiconductor (CMOS) processes, enabling large-scale, low-cost on-chip integration. It also possesses excellent thermal conductivity and mechanical stability, ensuring long-term stable chip operation. The input waveguide employs a bent waveguide structure with a width of 400nm–600nm and a bending angle of 20°–80°. It is primarily used to receive the probe optical signal. The bent waveguide structure optimizes the overall chip layout, reduces device size, and achieves miniaturized integration, while maintaining extremely low optical transmission loss. The output waveguide is also a bent waveguide, coupled to the second micro-ring resonator. It is responsible for extracting the transmitted spectral signal after resonant modulation and frequency selection, transmitting it to an external photodetector or spectrometer for signal acquisition and analysis.

[0035] In this embodiment, an intermediate waveguide is positioned between the first and second microring resonators, serving as an optical path connection and signal transmission mechanism. It transmits the optical signal processed by the first microring resonator. The intermediate waveguide has a width of 400nm–600nm and a bending angle of 20°–80°. It uses the same material and dimensions as the input waveguide to ensure the continuity and low loss of the optical signal transmission between the two rings. The first and second microring resonators are cascaded through the intermediate waveguide. A slight difference exists between their radii and free spectral ranges, creating a vernier effect. When the transmission spectra of the two microrings are superimposed, an envelope spectrum is formed. The free spectral range of the envelope spectrum is much larger than that of a single microring, significantly broadening the effective free spectral range of the overall structure. Only a single envelope peak is generated over a wide wavelength range, greatly simplifying the spectral analysis process. During detection, only the shift of the single envelope peak needs to be tracked to complete the concentration inversion.

[0036] In this embodiment, the radii of the first and second micro-ring resonators are set to 4μm to 8μm. The micro-ring radius directly determines the resonant wavelength and quality factor, thus affecting the device's filtering characteristics and detection selectivity. By precisely controlling the difference in the radii of the two rings, the operating wavelength of the resonator is highly compatible with the refractive index variation range of the alcohol solution, ensuring the accuracy of alcohol concentration detection. Both micro-ring resonators adopt a waveguide structure combining width gradient and curvature gradient. The curvature gradient curved waveguide adopts a combination of inner and outer curves. The inner curve is a circular curve, and the outer curve is an Euler-circular curve. The equivalent bending radius R0 is set to 4μm to 8μm. By optimizing the rate of change of curvature, the bending radiation loss is controlled below 0.0056 dB / 90°, significantly improving the micro-ring quality factor and enhancing the optical field confinement effect.

[0037] In this embodiment, the width of the micro-ring waveguide gradually varies along the light propagation direction, ranging from 400 nm to 520 nm. Specifically, the coupling region between the micro-ring and the straight waveguide uses a narrow width of 400 nm to enhance optical field coupling efficiency; the optical transmission region of the micro-ring uses a width of 520 nm to reduce optical transmission loss. This design effectively reduces the wavelength dependence of the coupling coefficient, solving the technical challenge of balancing bandwidth and resolution in traditional micro-ring designs. The micro-ring resonant cavity structure of this embodiment is as follows: Figure 3 As shown, an Euler-circular arc hybrid boundary design is adopted. The outer boundary is a complete Euler spiral to achieve a continuous and gradual change in curvature. The inner boundary is a combination structure of Euler spiral and circular arc. The mixing ratio is determined through numerical optimization so that the 45° symmetry point satisfies the geometric constraint conditions.

[0038] In this embodiment, couplers are respectively disposed between the input waveguide and the first microring resonator, between the intermediate waveguide and the two microring resonators, and between the output waveguide and the second microring resonator. The coupling spacing is set to 100nm to 200nm, and in this embodiment, the preferred coupling spacing is 0.10μm. The input waveguide width is fixed at 0.40μm. The coupling angle range of the upper input waveguide bus is -120° to -60°, and the coupling angle range of the lower bus is 60° to 120°. By optimizing the coupling structure and coupling spacing, the coupling coefficient is stably controlled, ensuring efficient transmission of optical signals in the cascaded optical path and providing support for the full utilization of the vernier effect.

[0039] Preferably, the equivalent radius of the ring resonator centerline is set to 5.000 μm, the minimum waveguide width is set to 0.40 μm, the maximum waveguide width is set to 0.52 μm, the equivalent radius of the outer boundary is set to 5.200 μm, and the equivalent radius of the inner boundary is set to 4.800 μm. The waveguide adopts a three-segment structure: a horizontal straight waveguide segment with a length of 5.0 μm; a Hermite curve transition segment with a length of 3.0 μm, using a cubic Hermite curve to ensure tangential continuity; and a curved coupling segment, extracted from the surface of the ring resonator by offset, the offset distance being determined by the local width on the ring, the coupling gap, and the bus width. The dual-ring resonance peak data obtained from the above parameter settings are obtained from... Figure 3 As shown.

[0040] In this embodiment, a first micro-heating electrode and a second micro-heating electrode are integrated above the first and second micro-ring resonators, respectively. The two sets of micro-heating electrodes are connected to an external driving power supply via a first contact electrode and a second contact electrode, respectively. By independently adjusting the heating power of the two micro-heating electrodes, the effective refractive index of the microrings is changed using the thermo-optic effect, precisely controlling the resonant wavelength of the dual rings. This ensures that the center wavelength of the single envelope peak generated by the vernier effect is precisely aligned with the characteristic absorption peak of ethanol molecules at 1400 nm, allowing the device to always operate within its optimal sensitivity range.

[0041] Figure 4 This disclosure illustrates a method flow chart for detecting low-concentration alcohol based on the aforementioned spectral analysis chip, comprising the following steps:

[0042] Step S1: A broadband light source with a wavelength range of 1350nm to 1450nm is connected to the chip input waveguide. The dual-ring resonator is thermo-optically tuned through a micro heating electrode. The heating power is adjusted so that the center wavelength of the single envelope peak formed by the vernier effect is aligned with multiple preset wavelength points in sequence to complete the full-band step wavelength scan.

[0043] In step S2, under each tuning state, the monochromatic light output by the chip is sequentially passed through the alcohol solution to be tested. The transmitted light intensity signal corresponding to each wavelength point is collected using a photodetector, and multiple sets of complete transmission spectrum data are collected to record the light absorption information of the solution to be tested at different wavelengths.

[0044] Step S3: The transmission spectrum data of the test solution obtained from multiple rounds of collection are compared with the pre-calibrated standard spectral library of alcohol concentration, and the changes in absorption characteristics at different wavelengths are analyzed to eliminate interference signals and extract effective feature information.

[0045] Step S4: Based on the detection data from multiple rounds and multiple wavelength points, and combined with the calibrated concentration correspondence, calculate the final concentration of the alcohol solution to be tested, and output the detection result.

[0046] The above detection method can achieve high-precision and rapid quantitative detection of alcohol at different concentrations. It is label-free and non-destructive throughout the process, with a fast response speed, and can realize real-time online monitoring. It is suitable for various application scenarios such as industrial production, environmental monitoring, and vehicle safety, and has broad prospects for promotion.

[0047] In this disclosure, the above-described detection method enables high-precision and rapid quantitative analysis of low-concentration alcohol. This method offers advantages such as label-free operation, real-time detection, and strong resistance to environmental interference, and can be widely applied in industrial production, environmental monitoring, and vehicle safety.

[0048] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. An alcohol detection device based on a dual-ring cascaded microring resonator with double-gradient width curvature, characterized in that, It includes an optical substrate, an input waveguide, a first microring resonator, an intermediate waveguide, a second microring resonator, an output waveguide, a coupling region, a first contact electrode, a first micro heating electrode, a second contact electrode, and a second micro heating electrode; The first microring resonator and the second microring resonator are cascaded together through an intermediate waveguide. After cascading, a vernier effect is formed, which expands the effective free spectrum range of the overall structure and forms a single envelope peak in a wide wavelength range. The input waveguide is connected to the first micro-ring resonator through a coupling region for receiving the probe optical signal; The intermediate waveguide is used to transmit the optical signal after it has been resonantly modulated by the first micro-ring resonator. The output waveguide is connected to the second microring resonator through a coupling region, and is used to output the optical signal after double-ring cascade filtering. Both the first and second microring resonators employ a structure combining a width-gradient waveguide and a curvature-gradient bent waveguide. Gradiently tapered waveguides are used to modulate mode dispersion and reduce wavelength dependence of coupling coefficients, while tapered curved waveguides are used to suppress bending radiation loss and improve the quality factor of microrings. The first micro heating electrode and the second micro heating electrode are respectively disposed above the first micro-ring resonator and the second micro-ring resonator. The micro heating electrode is connected to an external driving power supply through a contact electrode and is used to independently adjust the resonant wavelength of the dual rings to achieve wavelength alignment, step scanning and environmental temperature drift compensation. The device operates in the 1350-1450nm wavelength range, which is compatible with the refractive index variation range of alcohol solutions, enabling the detection of alcohol concentration based on optical transmission spectroscopy absorption.

2. The alcohol detection device based on a dual-ring cascaded microring resonator with double-gradient width curvature according to claim 1, characterized in that, The optical substrate is made of silicon-based material.

3. The alcohol detection device based on a dual-ring cascaded microring resonator with double-gradient width curvature according to claim 1, characterized in that, The waveguide widths of the first and second microring resonators gradually change along the direction of light propagation. The coupling region uses a waveguide width of 0.4 μm to improve coupling efficiency, while the transmission region uses a waveguide width of 0.5 μm to reduce transmission loss.

4. The alcohol detection device based on a dual-ring cascaded microring resonator with double-gradient width curvature according to claim 1, characterized in that, The inner curve of the gradually curvature curved waveguide is a circular curve, and the outer curve is an Euler-circular curve.

5. The alcohol detection device based on a dual-ring cascaded microring resonator with double-gradient width curvature according to claim 1, characterized in that, The input waveguide, intermediate waveguide, and output waveguide all adopt a curved waveguide structure.

6. The alcohol detection device based on a dual-ring cascaded microring resonator with double-gradient width curvature according to claim 1, characterized in that, The connection between the input waveguide and the first microring resonator, and the connection between the second microring resonator and the output waveguide, both adopt Hermite curve transitions.

7. An alcohol detection method based on the alcohol detection device according to claims 1-6, characterized in that, Includes the following steps: (1) The first micro-ring resonator and the second micro-ring resonator are thermally modulated by micro heating electrodes respectively, and the heating power is adjusted to align the double ring resonant peaks at the starting position of the characteristic band of alcohol detection. (2) Connect the broadband light source to the chip optical path so that the single-wavelength light signal output by the chip passes through the alcohol solution to be tested. The transmitted light intensity at that wavelength is collected by the photodetector to obtain the light transmittance of the corresponding wavelength. (3) Fine-tune the heating power of the micro heating electrode to make the double ring resonant peak generate a small range wavelength red shift, repeat the transmission detection and light intensity acquisition steps, and obtain the transmittance of the next corresponding wavelength. (4) Adjust the heating power step by step according to the set step size to complete the full-band step scan of the alcohol characteristic band and obtain the complete transmission spectrum of the alcohol solution to be tested in the characteristic band. (5) Compare the measured transmission spectrum with the standard transmission spectra of alcohol solutions of different concentrations to obtain the concentration detection results of the alcohol solution to be tested.

8. The alcohol detection method according to claim 7, characterized in that, The operating wavelength of the broadband light source covers the characteristic absorption peak of ethanol molecules.

9. The alcohol detection method according to claim 7, characterized in that, During the detection process, the resonant wavelength is adjusted in real time by a miniature heating electrode to keep the envelope peak formed by the double-ring vernier effect in the optimal detection band for alcohol, thus ensuring detection sensitivity and stability.

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