Integrated optical waveguide biosensor and method for manufacturing the same

Abstract

The present invention belongs to the technical field of biosensors, and discloses a method for manufacturing an integrated optical waveguide biosensor machine. This biosensor includes a pigtail semiconductor laser, a double microlens and an optical waveguide. The optical waveguide has a ridge waveguide core, and the double microlens includes a first microlens and a second microlens. The tail end of the pigtail semiconductor laser has a first microlens, and the beginning of the ridge waveguide core has a second microlens. The first microlens is aligned with the second microlens, and the end of the ridge waveguide core has a distributed Bragg reflector. The optical waveguide of the present invention not only retains the high sensitivity of the traditional interference optical waveguide, but also has the characteristics of simple structure and high manufacturing repeatability. In addition, the optical coupling method of the present invention realizes efficient optical coupling between the light source and the optical waveguide, and between the optical waveguide and the optical detector, thereby reducing the cost of the entire sensing system and improving its integration and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical waveguide biosensors, and in particular relates to an integrated optical waveguide biosensor and a manufacturing method thereof. Background Art

[0002] Biosensors are scientific analytical devices mainly composed of bioactive materials (such as enzymes, antigens, cells, etc.), physicochemical transducers (also known as signal converters) and signal detectors. It mainly reacts with the analyte to be measured by the bioactive material attached to the transducer, thereby inducing changes in one or more physicochemical properties (such as pH value, mass, temperature, refractive index, resonant frequency, etc.), and then the transducer converts these changes into secondary signals that can be detected by the signal detector. The strength, frequency or phase changes of these secondary signals are related to the concentration of the analyte to be measured bound by the bioactive material, thereby realizing the analysis and determination of the analyte to be measured. According to the different transducers, biosensors can be divided into piezoelectric quartz crystals, mechanical microcantilevers, and optical waveguide biosensors. Among them, optical waveguide biosensors have become the fastest-growing biosensors and the most studied biosensors at home and abroad in recent years due to their advantages such as label-free, real-time and fast, high sensitivity, strong anti-electromagnetic interference ability, low detection limit, and small size (micro-nano size).

[0003] At present, most optical waveguide biosensors are based on the evanescent wave sensing principle: when the light wave propagates along the core layer of the optical waveguide, a part of the light wave will penetrate into a very thin layer of the peripheral medium where the biological reaction occurs (about one wavelength), propagate along the interface for a distance (Goos-Hanchen displacement), and finally return to the waveguide core layer. The light wave that penetrates into the peripheral medium of the waveguide is called an evanescent wave. The guided mode evanescent wave can be used to sense the changes in the characteristics of the analyte to be measured caused by the biological reaction near the waveguide surface, thereby changing the phase, polarization, or amplitude of the light wave, and then use the appropriate optical path and circuit to detect and obtain the information of the analyte to be measured.

[0004] Among several different types of optical waveguide biosensors, the optical waveguide biosensor based on the interference effect has extremely high sensitivity and can be used to detect analytes with extremely low concentrations, such as extracting human growth hormone protein from urine for diagnosing growth disorder-related diseases. Usually, this type of optical waveguide biosensor splits light from the Y-shaped waveguide to the sensing arm and the reference arm. The light after the evanescent wave effect in the sensing arm and the light after the reference arm mix and interfere at the output end of the waveguide, and the information of the analyte to be measured is obtained by detecting the intensity of the interference light.

[0005] However, to date, the optical waveguide biosensor technology based on the interference effect has not been able to enter the market in the form of an integrated, low-cost, stable, mass-producible, simple and easy-to-operate product. The reasons may include the following two points: (1) The optical waveguide structure is complex and precise in design, with low manufacturing repeatability, and is not suitable for large-scale mass production. In order to obtain a stable and clear interference signal for extracting information about the analyte to be measured, the spectroscopic part on the waveguide needs to be precisely designed so that the light wave can be divided into two completely identical light waves that enter the sensing arm and the participating arm respectively. Such a design is easily affected by the environment, and it is difficult to effectively and accurately repeat the manufacture of such a spectroscopic part with current standard micromachining technology. (2) The integration level is not high, and it is built by relying on separate components, which makes the entire system bulky and expensive. At present, optical waveguide biosensors (not limited to interference type) use external light sources and couple light into ultra-thin (nanoscale) and ultra-narrow (micrometer-scale) optical waveguides through optical devices such as lenses, prisms and collimators, and then couple the light carrying the analyte information derived from the optical waveguide to an external light detector through a series of optical devices. Obviously, these will increase the size of the entire system, increase the cost, and reduce stability. Summary of the invention

[0006] The object of the present invention is to provide an integrated optical waveguide biosensor and a method for manufacturing the same to solve the above-mentioned technical problems.

[0007] In order to solve the above technical problems, the specific technical solutions of an integrated optical waveguide biosensor and a method for manufacturing the same are as follows:

[0008] An integrated optical waveguide biosensor comprises a pigtail semiconductor laser, a double microlens and an optical waveguide, wherein the optical waveguide has a ridge waveguide core; the double microlens comprises a first microlens and a second microlens, the tail end of the pigtail semiconductor laser has the first microlens, the beginning end of the ridge waveguide core has the second microlens, the first microlens is aligned with the second microlens, and the end of the ridge waveguide core has a distributed Bragg reflector; the pigtail semiconductor laser is used to emit laser light and receive feedback light from the ridge waveguide core; the double microlens is used for laser mutual coupling; and the optical waveguide is used to conduct laser light and reflect feedback light carrying information of an analyte to be measured.

[0009] Furthermore, the pigtail semiconductor laser includes a pigtail cladding and a pigtail core layer, and the pigtail cladding is coated on the outside of the pigtail core layer; the optical waveguide includes a substrate, a waveguide lower interlayer, a waveguide core layer and a waveguide upper interlayer, a sensing interval and a ridge waveguide core; the substrate is located at the bottom layer, above the substrate is the waveguide lower interlayer, above the waveguide lower interlayer is the waveguide core layer, above the waveguide core layer is the waveguide upper interlayer, the ridge-type optical waveguide is in the waveguide upper interlayer, and a window is opened on the top of the waveguide upper interlayer as a sensing interval.

[0010] Furthermore, the substrate is silicon, the waveguide core layer is silicon nitride, the waveguide lower interlayer and the waveguide upper interlayer are silicon dioxide, and the ridge-type optical waveguide is an insulating material of silicon nitride.

[0011] The present invention also discloses a method for manufacturing an integrated optical waveguide biosensor, comprising the following steps:

[0012] Step 1: Design and manufacture a ridge waveguide core with a distributed Bragg reflector at the end;

[0013] Step 2: Design and manufacture dual microlenses, integrated pigtailed semiconductor lasers and optical waveguides;

[0014] Step 3: Characterize an integrated optical waveguide biosensor based on laser self-mixing interference effect;

[0015] Step 4: Verify an integrated optical waveguide biosensor based on laser self-mixing interference effect.

[0016] Furthermore, the step 1 includes the following specific steps:

[0017] Step 1.1 Design the optical waveguide;

[0018] Firstly, the feedback laser rate equation is solved by using Matlab to obtain the stable range of the feedback semiconductor laser. Then, based on the obtained stable range, the commercial software COMSOL Multiphysics is used to perform a full 3D numerical simulation of the mode propagation characteristics of the optical waveguide. By optimizing the waveguide structural parameters, including ridge length, ridge height, ridge width, number of DBR layers, layer height and spacing between each layer, the penetration depth d of the evanescent wave is ensured to be small while the fundamental mode completes low-loss propagation and reflection in the waveguide. p It can also reach the maximum value;

[0019] The penetration depth of the evanescent wave is d p Described by the following formula, d p =λ(2πn Si3N4 ) -1 (sin 2 θ-n 2 SiO2 / n 2 Si3N4 ) -1 / 2 , where λ is the guided wavelength, n Si3N4 and n SiO2 are the refractive indices of the waveguide core layer, the waveguide lower interlayer, and the waveguide upper interlayer, respectively; θ is the incident angle of the guided wave at the interface between the waveguide core layer and the waveguide lower interlayer and the waveguide upper interlayer;

[0020] Step 1.2: making an optical waveguide;

[0021] Step 1.2.1: Thermally grow a silicon dioxide waveguide lower interlayer on the entire four-inch silicon wafer substrate using plasma enhanced chemical vapor deposition;

[0022] Step 1.2.2: Depositing a silicon nitride waveguide core layer on the silicon dioxide waveguide lower interlayer prepared in step 1.2.1 by using a low pressure chemical vapor deposition method;

[0023] Step 1.2.3: A silicon nitride ridge waveguide core and a distributed Bragg reflector at its end are etched on the waveguide core layer obtained in step 1.2.2 by using a mask and a reactive ion etching method;

[0024] Step 1.2.4: Plasma enhanced chemical vapor deposition is again used to deposit a silicon dioxide waveguide upper interlayer on the silicon nitride waveguide core layer obtained in step 1.2.3;

[0025] Step 1.2.5: A window is cut into the silicon dioxide waveguide prepared in step 1.2.4 using a mask as a sensing region, so that a portion of the ridge waveguide core is exposed to the external environment for biosensing.

[0026] Furthermore, it is characterized in that the step 2 comprises the following specific steps:

[0027] Step 2.1: Design double microlenses;

[0028] First, the spot size required for mutual coupling is determined according to the diameter size of the pigtail core layer and the cross-sectional size of the optical waveguide; the spot size must meet the following requirements: after the Gaussian beam output by the pigtail semiconductor laser passes through the double microlens mutual coupling system, the waist spot of the Gaussian spot output by the pigtail semiconductor laser must be smaller than or equal to the cross-sectional size of the optical waveguide to be coupled, and the numerical aperture corresponding to the half-far-field divergence angle must be smaller than or equal to the cross-sectional size of the optical waveguide to be coupled; then, the commercial software Zemax is used to perform full 3D numerical simulation of the double microlens; the double microlens is selected as a plano-convex lens to reduce the spherical aberration of the system; by optimizing the structural parameters of the double microlens, including thickness, numerical aperture, and the distance between the two lenses, the pigtail semiconductor laser and the optical waveguide can be easily calibrated and efficient mutual coupling between the two can be achieved;

[0029] Step 2.2: Make a double microlens; build a double microlens production platform: fix the fixture on the three-dimensional precision fine-tuning mobile platform, the upper end of the fixture has a microscope, the lower part of the microscope is an objective lens, and the femtosecond laser is set on one side of the microscope; use femtosecond laser two-photon direct etching technology to make the designed double microlens, the steps are as follows:

[0030] Step 2.2.1: Strip the pigtail semiconductor laser to expose the pigtail core layer and fix it on the fixture;

[0031] Step 2.2.2: Under a microscope, use a capillary needle to drop liquid two-photon photoresist on the surface of the pigtail core layer fixed in step 2.2.1;

[0032] Step 2.2.3: The laser of the femtosecond laser is emitted into the microscope, and then hits the photoresist dripped in step 2.2.2 through the objective lens and stimulates the two-photon absorption effect of the photoresist material to realize photolithography. The designed first microlens structure can be photolithographically produced by the computer-controlled three-dimensional precision fine-tuning moving platform. Finally, the unexposed photoresist is removed with a developer to form the final first microlens.

[0033] Step 2.2.4: Pull out the pigtail core layer from the fixture;

[0034] Step 2.2.5: The process of manufacturing the second microlens on the front end face of the ridge waveguide core is the same as that on the pigtail core layer, and the fixing device is adjusted according to the diameter of the ridge waveguide core.

[0035] Step 2.2.6: Integration: According to the spacing between the two microlenses designed in step 2.1, a groove is etched near the end face of the optical waveguide. Then, with the help of a microscope, the pigtail semiconductor laser with the first microlens is placed in the groove and aligned with the second microlens on the optical waveguide. Finally, with the help of a microscope again, a capillary needle is used to drip interlayer glue to cover the entire groove and perform thermal curing to complete the integration of the pigtail semiconductor laser and the optical waveguide.

[0036] Furthermore, the characterization of step 3 is divided into two parts: determination of the detection limit and determination of the surface sensitivity, and the characterization process uses a commercial microfluidic chip and an injection system to inject the sample into the sensing area on the optical waveguide;

[0037] The determination of the detection limit includes: first, gradually replacing the water flow injected at a uniform speed in the sensing interval with a hydrogen chloride solution of known concentration, which will cause a change in the refractive index of the sensing surface and then cause a change in the light phase through the evanescent wave effect. The changed light phase Δφ can then be obtained from the self-mixing signal The refractive index difference (n HCl -n H2O , n HCl and n H2O The refractive indices of hydrogen chloride and water, respectively, are measured in advance by a refractometer; by replacing hydrogen chloride solutions of different known concentrations several times, several sets of data between phase change and refractive index difference can be obtained, and a calibration curve is fitted based on these data. Finally, the detection limit can be obtained on the calibration curve through the minimum measurable phase change;

[0038] The surface sensitivity is determined by the following formulas:

[0039]

[0040] ΔN eff =(λΔφ)(2π1) -1 (2);

[0041] ΔΓ=A·d p ΔN eff (3);

[0042] Where G is the self-mixing signal, Δφ is the optical phase change, λ is the guided wavelength, ΔN eff is the effective refractive index change, A is the receptor adsorption coefficient, d p is the penetration depth of the evanescent wave, ΔΓ is the surface sensitivity (surface receptor adsorption ng / mm 2 ); After obtaining the self-mixing signal G, Δφ is unrolled from G by the method, and then ΔΓ is obtained according to equations (2) and (3). The receptor adsorption coefficient A in equation (3) is unknown, and the A value of different receptors is also different. It is proposed to analyze the characteristics of the self-mixing signal and combine equations (1), (2), (3) with appropriate advanced signal processing methods, that is, to design the corresponding algorithm in both time domain and frequency domain to extract the A value, and then obtain the surface sensitivity.

[0043] Furthermore, step 4 includes the following specific steps:

[0044] An integrated optical waveguide biosensor was validated by measuring the pesticide carbaryl content in fruit juice. The specific validation process is as follows:

[0045] Step 4.1: The silicon nitride surface in the sensing area can be covalently fixed with receptor molecules at the nanoscale through an esterification process. The receptor molecules used are complete antigens formed by coupling artificially synthesized carbaryl hapten with bovine serum albumin;

[0046] Step 4.2: After the receptors are fixed in step 4.1, the juice doped with standard carbaryl and diluted in PBS is injected into the sensing area to react biologically with the receptors therein and obtain a self-mixing signal;

[0047] Step 4.3: Obtain the optical phase change from the self-mixing signal obtained in step 4.2 by phase unwrapping method, and record the optical phase change and carbaryl concentration;

[0048] Step 4.4: Inject hydrogen chloride solution to clean the sensor surface;

[0049] Step 4.5: Repeat steps 4.1 to 4.4 and use different concentrations of standard carbaryl in step 4.2, repeat 10-20 times;

[0050] Step 4.6: Through the above steps, 10-20 sets of data between the light phase change and the carbaryl concentration are obtained, and the relationship expression between the light phase change and the carbaryl concentration is fitted based on these data.

[0051] The integrated optical waveguide biosensor and the manufacturing method thereof of the present invention have the following advantages:

[0052] The novel self-mixing interference micro / nano optical waveguide of the present invention not only retains the high sensitivity of the traditional interference optical waveguide, but also has the characteristics of simple structure and high manufacturing repeatability.

[0053] The method of connecting a pigtail semiconductor laser and an optical waveguide of the present invention realizes efficient optical coupling between a light source and an optical waveguide, and between an optical waveguide and an optical detector, thereby reducing the cost of the entire sensing system and improving its integration and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of the structure of the integrated optical waveguide biosensor of the present invention;

[0055] Figure 2 is a flow chart of a method for manufacturing an integrated optical waveguide biosensor of the present invention;

[0056] Figure 3 is a schematic diagram of the optical waveguide structure of the present invention;

[0057] Figure 4 A schematic diagram of manufacturing a double microlens of the present invention;

[0058] Figure 5 This is a working diagram of the integrated optical waveguide biosensor of the present invention;

[0059] Explanation of the marks in the figure: 1. Pigtail semiconductor laser; 11. Pigtail cladding; 12. Pigtail core; 2. Double microlens; 21. First microlens; 22. Second microlens; 3. Optical waveguide; 31. Substrate; 32. Waveguide lower interlayer; 33. Waveguide core; 34. Waveguide upper interlayer; 35. Sensing area; 36. Ridge waveguide core; 37. Distributed Bragg reflector; 4. Femtosecond laser; 5. Microscope; 6. Objective lens; 7. Photoresist; 8. Fixing device; 9. Three-dimensional precision fine-tuning moving platform. DETAILED DESCRIPTION

[0060] In order to better understand the purpose, structure and function of the present invention, the integrated optical waveguide biosensor and the manufacturing method thereof of the present invention are further described in detail below with reference to the accompanying drawings.

[0061] like Figure 1As shown, an integrated optical waveguide biosensor of the present invention comprises a pigtail semiconductor laser 1, a double microlens 2 and an optical waveguide 3, wherein the optical waveguide 3 has a ridge waveguide core 36. The double microlens 2 comprises a first microlens 21 and a second microlens 22, the tail end of the pigtail semiconductor laser 1 has the first microlens 21, the beginning end of the ridge waveguide core 36 has the second microlens 22, the first microlens 21 is aligned with the second microlens 22, and the end of the ridge waveguide core 36 has a distributed Bragg reflector 37.

[0062] The pigtail semiconductor laser 1 includes a pigtail cladding 11 and a pigtail core 12, wherein the pigtail cladding 11 is coated on the outside of the pigtail core 12. The optical waveguide 3 includes a substrate 31, a waveguide lower interlayer 32, a waveguide core 33, a waveguide upper interlayer 34, a sensing region 35, and a ridge waveguide core 36; the substrate 31 is silicon and is located at the bottom layer, the substrate 31 is above the waveguide lower interlayer 32, the waveguide lower interlayer 32 is above the waveguide core 33, the waveguide core 33 is silicon nitride, the waveguide upper interlayer 34 is above the waveguide core 33, and the ridge optical waveguide 3 is in the waveguide upper interlayer 34. The waveguide lower interlayer 32 and the waveguide upper interlayer 34 are silicon dioxide, and the ridge optical waveguide 3 is an insulating material of silicon nitride. A window is opened on the top of the waveguide upper interlayer 34 as a sensing region 35 to allow the evanescent wave to interact with the external biological environment. The main reason for choosing silicon nitride insulating material optical waveguide 3 is that it is transparent to visible light, because most biosensors currently use visible light sources and most biomolecules are only transparent to visible light. Silicon nitride also has the advantages of high density and strong chemical inertness, making it resistant to the penetration of oxygen and water, and its surface can be covalently modified for different biosensing purposes.

[0063] The pigtail semiconductor laser 1 is used to emit laser light and receive feedback light from the ridge waveguide core 36;

[0064] The double microlens 2 is used for laser mutual coupling;

[0065] The optical waveguide 3 is used to conduct laser light and reflect feedback light carrying information of the analyte to be measured.

[0066] like Figure 2 As shown, a method for manufacturing an integrated optical waveguide biosensor of the present invention comprises the following steps:

[0067] Step 1: Design and manufacture an optical waveguide 3 with a distributed Bragg reflector 37 at the end.

[0068] First, by using Matlab to solve the feedback laser rate equation (Lang and KobayashiEquations), the stability range of the feedback semiconductor laser is obtained (usually described by parameters such as external object reflectivity and feedback length). Then, based on the obtained stability range, the commercial software COMSOL Multiphysics is used to perform a full 3D numerical simulation of the mode propagation characteristics of the optical waveguide 3. By optimizing the waveguide structure parameters, including ridge length (feedback length), ridge height, ridge width, DBR layer number, layer height and spacing length between each layer (reflectivity), it is ensured that the fundamental mode completes low-loss propagation and reflection in the waveguide, while the penetration depth d of the evanescent wave is p can also reach the maximum value.

[0069] The penetration depth of the evanescent wave is d p Described by the following formula, d p =λ(2πn Si3N4 ) -1 (sin 2 θ-n 2 SiO2 / n 2 Si3N4 ) -1 / 2 , where λ is the guided wavelength, n Si3N4 and n SiO2 are the refractive indices of the waveguide core layer 33, the waveguide lower interlayer 32, and the waveguide upper interlayer 34, respectively; and θ is the incident angle of the guided wave at the interface between the waveguide core layer 33 and the waveguide lower interlayer 32 and the waveguide upper interlayer 34.

[0070] like Figure 3 As shown, the designed optical waveguide 3 will be manufactured in a clean room, and the process steps are as follows:

[0071] (1) Using plasma enhanced chemical vapor deposition (PECVD) to thermally grow a silicon dioxide waveguide lower interlayer 32 on the entire four-inch silicon wafer substrate 31. This layer of silicon dioxide can both constrain the light propagation in the waveguide core layer 33 and prevent the light from penetrating into the substrate 31 that can absorb visible light;

[0072] (2) using low pressure chemical vapor deposition (LPCVD) to deposit a silicon nitride waveguide core layer 33 on the silicon dioxide waveguide lower interlayer 32 produced in step (1);

[0073] (3) etching a silicon nitride ridge waveguide core 36 and a distributed Bragg reflector 37 (DBR) at its end on the waveguide core layer 33 obtained in step (2) by using a mask and reactive ion etching;

[0074] (4) using plasma enhanced chemical vapor deposition (PECVD) again to deposit a silicon dioxide waveguide upper interlayer 34 on the silicon nitride waveguide core layer 33 obtained in step (3);

[0075] (5) using a mask to carve a window as a sensing region 35 on the silicon dioxide waveguide upper interlayer 34 obtained in step (4), so that a portion of the ridge waveguide core 36 is exposed to an external environment for biosensing;

[0076] After fabrication, the entire wafer is covered with a protective resist layer and cut into individual chips using a slicer. There are about 10 waveguides on each chip, and about 10 chips can be cut out of one wafer. Therefore, about 100 waveguides can be made on one wafer to verify its manufacturing repeatability.

[0077] Step 2: Design and manufacture a double microlens 2, integrating a pigtailed semiconductor laser 1 and an optical waveguide 3.

[0078] First, the spot size required for mutual coupling is determined based on the diameter size of the pigtail core layer 12 and the cross-sectional size of the optical waveguide 3. The spot size must meet the following requirements: after the Gaussian beam output by the pigtail semiconductor laser 1 (pigtail) passes through the double microlens 2 mutual coupling system, the waist spot of the Gaussian spot output by it must be less than or equal to the cross-sectional size of the optical waveguide 3 (pigtail) to be coupled, and the numerical aperture corresponding to the half-far-field divergence angle must be less than or equal to the cross-sectional size of the optical waveguide 3 (pigtail) to be coupled. Then, the commercial software Zemax is used to perform a full 3D numerical simulation of the double microlens 2. The double microlens 2 is selected as a plano-convex lens to reduce the spherical aberration of the system. By optimizing the structural parameters of the double microlens 2, including thickness, numerical aperture, and the distance between the two lenses, the pigtail semiconductor laser 1 and the optical waveguide 3 can be easily calibrated and efficient mutual coupling between the two can be achieved.

[0079] like Figure 4 As shown, the designed double microlens 2 is manufactured using femtosecond laser two-photon direct etching technology, and the steps are as follows:

[0080] Build a double microlens 2 production platform: fix the fixture 8 on the three-dimensional precision fine-tuning mobile platform 9, the upper end of the fixture 8 has a microscope 5, the lower end of the microscope 5 is an objective lens 6, and the femtosecond laser 4 is set on one side of the microscope 5.

[0081] (1) peeling the pigtail semiconductor laser 1 to expose the pigtail core layer 12 and fixing it on a fixing device 8 (the fixing device 8 can be a specially made metal ring, etc.);

[0082] (2) Under a microscope 5, use a capillary needle to drop liquid two-photon photoresist 7 (IP-Resins is used for two-photon polymerization) on the surface of the pigtail core layer 12 fixed in step (1);

[0083] (3) The laser of the femtosecond laser 4 is emitted into the microscope 5, and then hits the photoresist 7 dripped in step (2) through the objective lens 6 and stimulates the two-photon absorption effect of the photoresist 7 material to realize photolithography. The designed first microlens 21 structure can be photolithographically produced by computer-controlled three-dimensional precision fine-tuning moving platform 9. Finally, the unexposed photoresist 7 is removed using a developer to form the final first microlens 21;

[0084] (4) extracting the pigtail core layer 12 from the fixture 8;

[0085] The process of manufacturing the second microlens 22 on the front end face of the ridge waveguide core 36 is the same as that on the pigtail core layer 12 , except that the fixing device 8 is different. The fixing device 8 is adjusted according to the diameter of the ridge waveguide core 36 .

[0086] Integration: According to the previously designed spacing between the dual microlenses 2, a groove is etched near the end face of the optical waveguide 3. Then, with the help of a microscope 5, the pigtail semiconductor laser 1 with the first microlens 21 is placed in the groove and aligned with the second microlens 22 on the optical waveguide 3. Finally, with the help of a microscope 5 again, a capillary needle is used to drip interlayer glue to cover the entire groove and perform thermal curing to complete the integration of the pigtail semiconductor laser 1 and the optical waveguide 3.

[0087] Step 3: Characterize an integrated optical waveguide biosensor based on laser self-mixing interference effect.

[0088] The characterization is divided into two parts: determination of the detection limit and determination of the surface sensitivity. The characterization process will use a commercial microfluidic chip and injection system to inject the sample into the sensing area 35 on the optical waveguide 3.

[0089] Determination of the detection limit: First, the water flow injected at a constant speed in the sensing area 35 is gradually replaced by a hydrogen chloride solution of known concentration. This replacement will cause a change in the refractive index of the sensing surface and then cause a change in the light phase through the evanescent wave effect. The changed light phase Δφ can then be obtained from the self-mixing signal The refractive index difference (n HCl -n H2O ,n HCl and n H2O The refractive indexes of hydrogen chloride and water, respectively, can be measured in advance by a refractometer. By replacing hydrogen chloride solutions of different known concentrations several times, several sets of data between phase change and refractive index difference can be obtained. Based on these data, a calibration curve can be fitted. Finally, the detection limit (minimum refractive index difference RIU) can be obtained on the calibration curve through the minimum measurable phase change.

[0090] Determination of surface sensitivity:

[0091] Surface sensitivity is determined by the following formulas:

[0092]

[0093] ΔN eff =(λΔφ)(2π1) -1 (2);

[0094] ΔΓ=A·d p ΔN eff (3);

[0095] Where G is the self-mixing signal, Δφ is the optical phase change, λ is the guided wavelength, ΔN eff is the effective refractive index change, A is the receptor adsorption coefficient, d p is the penetration depth of the evanescent wave, ΔΓ is the surface sensitivity (surface receptor adsorption ng / mm 2 ). After obtaining the self-mixing signal G, Δφ can be unrolled from G by a method. Then, according to equations (2) and (3), ΔΓ can be obtained. The receptor adsorption coefficient A in equation (3) is unknown, and the A value of different receptors is also different. It is proposed to extract the A value by analyzing the characteristics of the self-mixing signal and combining equations (1), (2), (3) with appropriate advanced signal processing methods (i.e., in the time domain and in the frequency domain) and the corresponding algorithm design to obtain the surface sensitivity.

[0096] Step 4: Verify an integrated optical waveguide biosensor based on laser self-mixing interference effect.

[0097] An integrated optical waveguide biosensor based on the laser self-mixing interference effect was verified by measuring the content of pesticide carbaryl in juice. The specific verification process is as follows:

[0098] (1) Through the esterification process, the silicon nitride surface in the sensing area 35 can covalently fix the receptor molecule on the nanoscale. The receptor molecule used is a complete antigen formed by coupling the artificially synthesized carbaryl hapten with bovine serum albumin;

[0099] (2) After the receptors are fixed in step (1), the juice doped with standard carbaryl and diluted in PBS is injected into the sensing area 35 to cause a biological reaction with the receptors therein and obtain a self-mixing signal;

[0100] (3) obtaining the optical phase change from the self-mixing signal obtained in step (2) by a phase unwrapping method, and recording the optical phase change and the carbaryl concentration;

[0101] (4) Injecting hydrogen chloride solution to clean the sensor surface;

[0102] (5) Repeat steps (1) to (4) and use different concentrations of standard carbaryl in step (2). Repeat 10-20 times;

[0103] Through the above steps, 10-20 sets of data between the light phase change and the carbaryl concentration can be obtained. Based on these data, a relationship expression between the light phase change and the carbaryl concentration can be fitted.

[0104] like Figure 5 As shown, the workflow of the present invention is as follows:

[0105] Step S501: the pigtail conductor laser 1 emits laser;

[0106] Step S502: The laser light is coupled from the first microlens 21 at the tail end of the pigtail core layer 12 to the beginning end of the optical waveguide 3;

[0107] Step S503: The laser travels along the ridge waveguide core 36 and passes through the sensing area 35 to generate an evanescent wave;

[0108] Step S504: a portion of the light passing through the sensing region 35 will be reflected by the distributed Bragg reflector 37 (DBR) at the end of the ridge waveguide core 36;

[0109] Step S505: The reflected laser light is coupled back to the pigtail core layer 12 via the second microlens 22 at the beginning of the ridge waveguide core 36;

[0110] Step S506: Due to the evanescent wave effect, the laser light coupled back to the pigtail core layer 12 (referred to as feedback light) carries the information of the analyte to be measured and its optical properties have changed relative to the intracavity light. When it is mixed with the intracavity light, the output optical power of the pigtail conductor laser 1 is modulated;

[0111] Step S507: the modulated signal is similar to a conventional double-beam interference signal, and a photodiode sealed inside the pigtail semiconductor laser 1 detects the modulated self-mixing signal;

[0112] Step S508: analyzing the information of the object to be tested according to the detected self-mixing signal.

[0113] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. An integrated optical waveguide biosensor, characterized in that: The invention comprises a pigtail semiconductor laser (1), a double microlens (2) and an optical waveguide (3), wherein the optical waveguide (3) has a ridge waveguide core (36); the double microlens (2) comprises a first microlens (21) and a second microlens (22); the tail end of the pigtail semiconductor laser (1) has the first microlens (21), the beginning end of the ridge waveguide core (36) has the second microlens (22), the first microlens (21) is aligned with the second microlens (22), and the end of the ridge waveguide core (36) has a distributed Bragg reflector (37); the pigtail semiconductor laser (1) is used to emit laser light and receive feedback light from the ridge waveguide core (36); the double microlens (2) is used for laser mutual coupling; the optical waveguide (3) is used to conduct laser light and reflect the light carrying the feedback light. The invention relates to feedback light of information of an analyte to be measured, wherein the pigtail semiconductor laser (1) comprises a pigtail cladding (11) and a pigtail core layer (12), wherein the pigtail cladding (11) is coated on the outside of the pigtail core layer (12); the optical waveguide (3) comprises a substrate (31), a waveguide lower sandwich layer (32), a waveguide core layer (33), a waveguide upper sandwich layer (34), a sensing region (35) and a ridge waveguide core (36); the substrate (31) is located at the bottom layer, the substrate (31) is above the waveguide lower sandwich layer (32), the waveguide core layer (33) is above the waveguide lower sandwich layer (32), the waveguide upper sandwich layer (34) is above the waveguide core layer (33), the optical waveguide (3) is in the waveguide upper sandwich layer (34), and a window is opened at the top of the waveguide upper sandwich layer (34) as a sensing region (35).

2. The integrated optical waveguide biosensor according to claim 1, characterized in that: The substrate (31) is silicon, the waveguide core layer (33) is silicon nitride, the waveguide lower interlayer (32) and the waveguide upper interlayer (34) are silicon dioxide, and the ridge-type optical waveguide (3) is an insulating material of silicon nitride.

3. A method for manufacturing an integrated optical waveguide biosensor according to any one of claims 1 to 2, characterized in that: The steps include: Step 1: designing and manufacturing a ridge waveguide core (36) with a distributed Bragg reflector (37) at the end; Step 2: Design and manufacture a double microlens (2), integrate a pigtailed semiconductor laser (1) and an optical waveguide (3); Step 3: Characterize an integrated optical waveguide biosensor based on laser self-mixing interference effect; Step 4: Verify an integrated optical waveguide biosensor based on laser self-mixing interference effect.

4. The method for manufacturing an integrated optical waveguide biosensor according to claim 3, characterized in that: The step 1 comprises the following specific steps: Step 1.1 Designing an optical waveguide (3); Firstly, the feedback laser rate equation is solved by using Matlab to obtain the stability range of the feedback semiconductor laser. Then, based on the obtained stability range, the commercial software COMSOL Multiphysics is used to perform a full 3D numerical simulation of the mode propagation characteristics of the optical waveguide (3). By optimizing the waveguide structural parameters, including ridge length, ridge height, ridge width, number of DBR layers, layer height and spacing between each layer, the fundamental mode is ensured to complete low-loss propagation and reflection in the waveguide while the penetration depth d of the evanescent wave is minimized. p It can also reach the maximum value; The penetration depth of the evanescent wave is d p Described by the following formula, Where λ is the guided wave wavelength, and are the refractive indices of the waveguide core layer (33), the waveguide lower interlayer (32), and the waveguide upper interlayer (34), respectively; and θ is the incident angle of the guided wave at the interface between the waveguide core layer (33) and the waveguide lower interlayer (32) and the waveguide upper interlayer (34); Step 1.2: preparing an optical waveguide (3); Step 1.2.1: thermally growing a silicon dioxide waveguide lower interlayer (32) on the entire four-inch silicon wafer substrate (31) using a plasma enhanced chemical vapor deposition method; Step 1.2.2: using low pressure chemical vapor deposition to deposit a silicon nitride waveguide core layer (33) on the silicon dioxide waveguide lower interlayer (32) produced in step 1.2.1; Step 1.2.3: etching a silicon nitride ridge waveguide core (36) and a distributed Bragg reflector (37) at its end on the waveguide core layer (33) obtained in step 1.2.2 by using a mask and a reactive ion etching method; Step 1.2.4: Depositing a silicon dioxide waveguide upper interlayer (34) on the silicon nitride waveguide core layer (33) obtained in step 1.2.3 by plasma enhanced chemical vapor deposition again; Step 1.2.5: A window is carved into the upper interlayer (34) of the silicon dioxide waveguide prepared in step 1.2.4 by using a mask as a sensing region (35), so that a portion of the ridge waveguide core (36) is exposed to the external environment for biosensing.

5. The method for manufacturing an integrated optical waveguide biosensor according to claim 3, characterized in that: The step 2 comprises the following specific steps: Step 2.1: Design double microlenses (2); First, the spot size required for mutual coupling is determined according to the diameter size of the pigtail core layer (12) and the cross-sectional size of the optical waveguide (3); the spot size must meet the following requirements: after the Gaussian light beam output by the pigtail semiconductor laser (1) passes through the double microlens (2) mutual coupling system, the waist spot of the Gaussian light spot output by the pigtail semiconductor laser (1) must be smaller than or equal to the cross-sectional size of the optical waveguide (3) to be coupled, and the numerical aperture corresponding to the half far-field divergence angle must be smaller than or equal to the cross-sectional size of the optical waveguide (3) to be coupled; then, the commercial software Zemax is used to perform a full 3D numerical simulation of the double microlens (2); the double microlens (2) is selected as a plano-convex lens to reduce the spherical aberration of the system; By optimizing the structural parameters of the double microlens (2), including thickness, numerical aperture, and the distance between the two lenses, the pigtail semiconductor laser (1) and the optical waveguide (3) can be easily calibrated and highly efficient mutual coupling can be achieved between the two. Step 2.2: Make a double microlens (2); build a double microlens (2) production platform: fix a fixture (8) on a three-dimensional precision fine-tuning mobile platform (9), the fixture (8) has a microscope (5) on the upper end, the microscope (5) is located below the objective lens (6), and a femtosecond laser (4) is arranged on one side of the microscope (5); use a femtosecond laser two-photon direct etching technology to manufacture the designed double microlens (2), the steps are as follows: Step 2.2.1: peeling the pigtail semiconductor laser (1) to expose the pigtail core layer (12) and fixing it on a fixing device (8); Step 2.2.2: Under a microscope (5), use a capillary needle to drop liquid two-photon photoresist (7) on the surface of the pigtail core layer (12) fixed in step 2.2.1; Step 2.2.3: The laser light from the femtosecond laser (4) is emitted into the microscope (5), and then is hit on the photoresist (7) deposited in step 2.2.2 through the objective lens (6) to stimulate the two-photon absorption effect of the photoresist (7) material to realize photolithography. The designed first microlens (21) structure can be photolithographically produced by controlling the three-dimensional precision fine-tuning moving platform (9) by computer. Finally, a developer is used to remove the unexposed photoresist (7) to form the final first microlens (21); Step 2.2.4: Pull out the pigtail core layer (12) from the fixture (8); Step 2.2.5: The process of manufacturing the second microlens (22) on the front end face of the ridge waveguide core (36) is the same as that on the pigtail core layer (12), and the fixing device (8) is adjusted according to the diameter of the ridge waveguide core (36); Step 2.2.6: Integration: Based on the spacing between the two microlenses (2) designed in step 2.1, a groove is etched near the end face of the optical waveguide (3). Then, with the help of a microscope (5), the pigtail semiconductor laser (1) with the first microlens (21) is placed in the groove and aligned with the second microlens (22) on the optical waveguide (3). Finally, with the help of a microscope (5), a capillary needle is used to drip interlayer glue to cover the entire groove and perform thermal curing to complete the integration of the pigtail semiconductor laser (1) and the optical waveguide (3).

6. The method for manufacturing an integrated optical waveguide biosensor according to claim 3, characterized in that: The characterization of step 3 is divided into two parts: determination of the detection limit and determination of the surface sensitivity. The characterization process uses a commercial microfluidic chip and an injection system to inject the sample into the sensing area (35) on the optical waveguide (3); The determination of the detection limit comprises: firstly, gradually replacing the water flow uniformly injected into the sensing area (35) with a hydrogen chloride solution of known concentration, which will cause a change in the refractive index of the sensing surface and then cause a change in the light phase through the evanescent wave effect. The changed light phase Δφ can then be obtained from the self-mixing signal The phase difference is extracted by the method and matched with the refractive index difference, which is measured by a refractometer in advance; several sets of data between the phase change and the refractive index difference are obtained by replacing the hydrogen chloride solution with different known concentrations several times, and a calibration curve is fitted based on these data. Finally, the detection limit is obtained on the calibration curve by the minimum measurable phase change; The surface sensitivity is determined by the following formulas: ΔN eff =(λΔφ)(2πl) -1 (1-2); ΔΓ=A·d p ·ΔN eff (1-3); Where G is the self-mixing signal, Δφ is the optical phase change, λ is the guided wavelength, ΔN eff is the effective refractive index change, A is the receptor adsorption coefficient, d p is the penetration depth of the evanescent wave, ΔΓ is the surface sensitivity; when the self-mixing signal G is obtained, Δφ is unrolled from G through the method, and then ΔΓ is obtained according to equations (1-2) and (1-3). The receptor adsorption coefficient A in equation (1-3) is unknown, and the A value of different receptors is also different. It is intended to analyze the characteristics of the self-mixing signal and combine equations (1-1), (1-2), and (1-3), and adopt appropriate advanced signal processing methods, that is, to design corresponding algorithms in both time domain and frequency domain to extract the A value, and then obtain the surface sensitivity.

7. The method for manufacturing an integrated optical waveguide biosensor according to claim 3, characterized in that: The step 4 comprises the following specific steps: An integrated optical waveguide biosensor was validated by measuring the pesticide carbaryl content in fruit juice. The specific validation process is as follows: Step 4.1: The silicon nitride surface of the sensing region (35) can be covalently fixed with a receptor molecule at the nanoscale through an esterification process, wherein the receptor molecule used is a complete antigen formed by coupling an artificially synthesized carbaryl hapten with bovine serum albumin; Step 4.2: After the receptors are fixed in step 4.1, the juice doped with standard carbaryl and diluted in PBS is injected into the sensing area (35) to react biologically with the receptors therein and obtain a self-mixing signal; Step 4.3: Obtain the optical phase change from the self-mixing signal obtained in step 4.2 by phase unwrapping method, and record the optical phase change and carbaryl concentration; Step 4.4: Inject hydrogen chloride solution to clean the sensor surface; Step 4.5: Repeat steps 4.1 to 4.4 and use different concentrations of standard carbaryl in step 4.2, repeat 10-20 times; Step 4.6: Through the above steps, 10-20 sets of data between the light phase change and the carbaryl concentration are obtained, and the relationship expression between the light phase change and the carbaryl concentration is fitted based on these data.

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