CN110296986B - An on-chip dense waveguide-based nanoparticle sensor and its sensing method - Google Patents

Abstract

Translated fromChinese

本发明公开了一种基于片上密集型波导的纳米颗粒传感器及其传感方法。本发明将单根波导以不产生耦合的条件下最大密度水平缠绕在基底的表面形成密集型波导，当附着在密集型波导表面的纳米颗粒位于波导模式的倏逝场范围内时，探测光被纳米颗粒散射或吸收，透射功率产生一个急剧下降的台阶信号，这个台阶信号编码了纳米颗粒的大小信息，计算机通过识别台阶信号判断纳米颗粒有无，并得到纳米颗粒的大小信息；本发明的密集型波导传感面积大，比直波导提高两个数量级；同时捕获效率高，时间响应快；能够探测的纳米颗粒的半径为100纳米的小球；另外TM偏振的波导模式的散射信号是TE偏振的30倍。

The invention discloses a nanoparticle sensor based on a dense waveguide on a chip and a sensing method thereof. In the present invention, a single waveguide is wound on the surface of the substrate at a maximum density level without coupling to form a dense waveguide. When the nanoparticles attached to the surface of the dense waveguide are located in the evanescent field range of the waveguide mode, the detection light is The nanoparticle scatters or absorbs, and the transmission power generates a sharply reduced step signal, which encodes the size information of the nanoparticle, and the computer judges the presence or absence of the nanoparticle by identifying the step signal, and obtains the size information of the nanoparticle; The sensing area of the waveguide is large, which is two orders of magnitude higher than that of the straight waveguide; at the same time, the capture efficiency is high and the time response is fast; the nanoparticles can be detected as small balls with a radius of 100 nanometers; in addition, the scattering signal of the TM-polarized waveguide mode is TE-polarized 30 times.

Description

Translated fromChinese

一种基于片上密集型波导的纳米颗粒传感器及其传感方法An on-chip dense waveguide-based nanoparticle sensor and its sensing method

技术领域technical field

本发明涉及纳米颗粒传感技术，具体涉及一种基于片上密集型波导的纳米颗粒传感器及其传感方法。The invention relates to a nanoparticle sensing technology, in particular to a nanoparticle sensor based on an on-chip dense waveguide and a sensing method thereof.

背景技术Background technique

目前国土安全、环境监测和早期诊断等相关领域都急需可以实现纳米尺度颗粒的原位、快速、超灵敏和可重复性的检测平台。在各种传感器中，光学倏逝场传感器由于很多独特的优势，比如高灵敏度、无需标记与非侵入性等，吸引了越来越多人的注意。近年来，相关研究主要聚集在探索新机制来提高传感器的灵敏度。例如，利用微腔中的奇异点或者结合等离激元增强效应将传感器的灵敏度提高到单个生物分子和单原子水平的检测。纳米光纤利用暗场中的光弹性散射概念甚至将探测极限降低至量子噪声水平。虽然这些传感器的灵敏度已经超过目前应用的需求，但是以下几个方面严重阻碍了他们的实际应用的推广：1.微纳尺度的谐振腔的传感面积极小，因此需要非常长的时间去捕获和表征纳米颗粒。虽然纳米光纤线圈和阵列可以增加探测面积，但是纳米光纤轴向的低均匀度、难以与微流集成以及相关的纳米光纤固定装置都限制了这种传感器的实际应用。2.微腔和等离激元谐振腔中的高功率密度会对生物分子具有光破坏作用。3.纳米光纤、微腔和半连续的等离激元薄膜等光学传感器的制备过程很难实现精确控制，导致所制备出来的传感器性能不一致。因此，考虑到及时诊断器件的快速发展，目前急需发展一个可高度重复的传感平台来实现纳米颗粒的快速与超灵敏检测。Currently, there is an urgent need for in situ, rapid, ultrasensitive, and reproducible detection platforms for nanoscale particles in related fields such as homeland security, environmental monitoring, and early diagnosis. Among various sensors, optical evanescent field sensors have attracted more and more attention due to many unique advantages, such as high sensitivity, no labeling, and non-invasiveness. In recent years, related research has mainly focused on exploring new mechanisms to improve the sensitivity of sensors. For example, the use of singularities in microcavities or combined with plasmon-enhanced effects can increase the sensitivity of the sensor to detection at the single biomolecule and single atom level. Nanofibers exploit the concept of photoelastic scattering in dark fields to even lower the detection limit to the level of quantum noise. Although the sensitivity of these sensors has exceeded the requirements of current applications, the following aspects have seriously hindered their practical application: 1. The sensing area of micro- and nano-scale resonators is very small, so it takes a very long time to capture and characterization of nanoparticles. Although nanofiber coils and arrays can increase the detection area, the low axial uniformity of nanofibers, the difficulty in integrating with microfluidics, and the associated nanofiber fixtures limit the practical application of such sensors. 2. High power densities in microcavities and plasmonic resonators can have photodamaging effects on biomolecules. 3. The fabrication process of optical sensors such as nanofibers, microcavities, and semi-continuous plasmonic films is difficult to precisely control, resulting in inconsistent performance of the fabricated sensors. Therefore, considering the rapid development of timely diagnostic devices, there is an urgent need to develop a highly reproducible sensing platform for rapid and ultrasensitive detection of nanoparticles.

发明内容SUMMARY OF THE INVENTION

针对以上现有技术中存在的问题，本发明提出了一种基于片上密集型波导的纳米颗粒传感器及其传感方法，利用波导倏逝场中的弹性散射原理，来检测非标记的单纳米颗粒。In view of the above problems in the prior art, the present invention proposes a nanoparticle sensor based on an on-chip dense waveguide and a sensing method thereof, which utilizes the principle of elastic scattering in the evanescent field of the waveguide to detect unlabeled single nanoparticles .

本发明的一个目的在于提出一种基于片上密集型波导的纳米颗粒传感器。An object of the present invention is to propose an on-chip dense waveguide-based nanoparticle sensor.

本发明的基于片上密集型波导的纳米颗粒传感器包括：基底、单根波导、光源装置、第一和第二光纤波导耦合器、光电探测器、数据采集卡和计算机；其中，单根波导在不会产生耦合的条件下以最大密度绕在基底上表面的平面上，缠绕形成的形状的曲率半径大于5μm，以降低光的损耗，从而在基底的表面形成密集型波导；在单根波导的一端设置第一光纤波导耦合器，在单根波导的另一端设置第二光纤波导耦合器；光电探测器连接至数据采集卡；数据采集卡连接至计算机；光源装置发出探测光，经第一光纤波导耦合器进入密集型波导，经密集型波导透射后，透射光经第二光纤波导耦合器由光电探测器接收；光电探测器将光信号转换为电信号后，传输至数据采集卡进行模数转换后，将数据传输至计算机进行数据均值滤波处理并提取传感信号；当附着在密集型波导表面的纳米颗粒位于密集型波导的波导模式的倏逝场范围内时，探测光被纳米颗粒散射或吸收，透射功率产生一个急剧下降的台阶信号，这个台阶信号编码了纳米颗粒的大小信息，计算机通过识别台阶信号判断纳米颗粒有无，并得到纳米颗粒的大小信息。The on-chip dense waveguide-based nanoparticle sensor of the present invention includes: a substrate, a single waveguide, a light source device, first and second optical fiber waveguide couplers, a photodetector, a data acquisition card and a computer; wherein the single waveguide is not Under the condition of coupling, it is wound on the plane of the upper surface of the substrate at the maximum density, and the curvature radius of the shape formed by the winding is greater than 5 μm to reduce the loss of light, thereby forming a dense waveguide on the surface of the substrate; at one end of a single waveguide A first optical fiber waveguide coupler is arranged, and a second optical fiber waveguide coupler is arranged at the other end of the single waveguide; the photodetector is connected to the data acquisition card; the data acquisition card is connected to the computer; the light source device emits detection light, and the first optical fiber waveguide The coupler enters the dense waveguide, and after being transmitted through the dense waveguide, the transmitted light is received by the photodetector through the second fiber waveguide coupler; after the photodetector converts the optical signal into an electrical signal, it is transmitted to the data acquisition card for analog-to-digital conversion Then, the data is transmitted to the computer for data averaging filtering and sensing signal extraction; when the nanoparticles attached to the surface of the dense waveguide are located in the evanescent field range of the waveguide mode of the dense waveguide, the probe light is scattered by the nanoparticles or The absorption and transmission power produces a sharply decreasing step signal, which encodes the size information of the nanoparticle. The computer judges the presence or absence of the nanoparticle by identifying the step signal, and obtains the size information of the nanoparticle.

基底和波导采用对探测光损耗小的材料，波导采用硅，基底采用硅上的二氧化硅，此时二氧化硅的厚度≥1μm。The substrate and the waveguide are made of materials with small loss to the detection light, the waveguide is made of silicon, and the substrate is made of silicon dioxide on silicon, and the thickness of the silicon dioxide is ≥1 μm.

单个波导的横截面的宽和高均为百纳米。The width and height of the cross-section of a single waveguide are both hundreds of nanometers.

第一和第二光纤波导耦合器采用光栅、光纤棱镜或者光纤锥-波导上下接触式耦合器。The first and second fiber-optic waveguide couplers employ gratings, fiber-optic prisms, or fiber-optic taper-waveguide up-and-down contact couplers.

光源装置包括激光器和函数发生器，激光器发出激光，经函数发生器形成光强稳定并具有设定形状和频率的探测光。The light source device includes a laser and a function generator. The laser emits laser light, and the function generator forms a probe light with stable light intensity and a set shape and frequency.

本发明的另一个目的在于提供一种基于片上密集型波导的纳米颗粒传感方法。Another object of the present invention is to provide an on-chip dense waveguide-based nanoparticle sensing method.

本发明的基于片上密集型波导的纳米颗粒传感方法，包括以下步骤：The nanoparticle sensing method based on the on-chip dense waveguide of the present invention includes the following steps:

1)光源装置发出探测光，经第一光纤波导耦合器进入密集型波导；经密集型波导透射后，1) The light source device emits probe light, which enters the dense waveguide through the first fiber waveguide coupler; after being transmitted through the dense waveguide,

透射光经第二光纤波导耦合器由光电探测器接收；The transmitted light is received by the photodetector through the second fiber waveguide coupler;

2)光电探测器将光信号转换为电信号后，传输至数据采集卡进行模数转换采集；然后将2) After the photodetector converts the optical signal into an electrical signal, it is transmitted to the data acquisition card for analog-to-digital conversion and acquisition; then the

数据传输至计算机进行均值滤波处理并提取传感信号；The data is transmitted to the computer for mean filtering processing and the sensing signal is extracted;

3)当附着在密集型波导表面的纳米颗粒位于密集型波导的波导模式的倏逝场范围内时，3) When the nanoparticles attached to the surface of the dense waveguide are located in the evanescent field range of the waveguide mode of the dense waveguide,

探测光被纳米颗粒散射或吸收，透射功率产生一个急剧下降的台阶信号，这个台阶信号The probe light is scattered or absorbed by the nanoparticles, and the transmitted power produces a sharply reduced step signal, which

编码了纳米颗粒的大小信息；Encodes the size information of the nanoparticle;

4)计算机识别台阶信号，并通过台阶信号判断纳米颗粒有无，进一步得到纳米颗粒的大4) The computer recognizes the step signal, and judges the presence or absence of nanoparticles through the step signal, and further obtains the size of the nanoparticles.

小信息。little information.

其中，在步骤4)中，计算机通过识别台阶信号包括以下步骤：Wherein, in step 4), the computer comprises the following steps by identifying the step signal:

a)将数据采集的时间区间内的数据划分为多个处理单元，为了使算法在提取信号时不受环境引起的缓变信号的影响，并同时能够识别两个时间间隔较近的台阶信号，这个处理单元的时间区间不宜太长，时间区域在0.06s～0.1s；a) Divide the data in the time interval of data collection into multiple processing units, so that the algorithm is not affected by the slowly changing signal caused by the environment when extracting the signal, and at the same time can identify two step signals with close time intervals, The time interval of this processing unit should not be too long, and the time range is 0.06s to 0.1s;

b)计算前后第(N-1)个处理单元和第(N+1)个处理单元的平均值之差，N为≥10的自然数；b) The difference between the average value of the (N-1)th processing unit and the (N+1)th processing unit before and after the calculation, N is a natural number ≥ 10;

c)通过对比所得到的差值与第(N-M)个处理单元和第(N+M)个处理单元区间内信号的噪声水平，将台阶识别出来，从而得到台阶信号，M为≤N的自然数，且10≤M≤100。c) By comparing the difference obtained with the noise level of the signal in the (N-M)th processing unit and the (N+M)th processing unit interval, the steps are identified, and the step signal is obtained, where M is a natural number ≤N , and 10≤M≤100.

每一个台阶信号，代表探测到了一个纳米颗粒，从而从识别出的台阶信号判断了纳米颗粒的有无。Each step signal represents the detection of a nanoparticle, so the presence or absence of nanoparticles can be judged from the identified step signal.

进一步，通过台阶信号得到纳米颗粒的大小信息，包括以下步骤：Further, obtaining the size information of the nanoparticles through the step signal includes the following steps:

a)根据台阶信号得到此时由纳米颗粒在波导表面引起的散射效率，散射效率等于台阶对应的探测光强下降功率除以探测光总功率；a) According to the step signal, the scattering efficiency caused by the nanoparticles on the surface of the waveguide is obtained, and the scattering efficiency is equal to the drop power of the probe light intensity corresponding to the step divided by the total power of the probe light;

b)然后根据散射效率的大小，在有限元仿真得到的标定数据上找到纳米颗粒的粒径范围，从而得到此时纳米颗粒的大小。b) Then, according to the size of the scattering efficiency, the particle size range of the nanoparticles is found on the calibration data obtained by the finite element simulation, so as to obtain the size of the nanoparticles at this time.

在步骤b)中，通过有限元仿真得到标定数据，包括以下步骤：In step b), the calibration data is obtained through finite element simulation, including the following steps:

i.首先将密集型波导、纳米颗粒以及基底的材料根据实际参数进行几何建模，同时定义材料的折射率和吸收系数；i. Firstly, the materials of dense waveguides, nanoparticles and substrates are geometrically modeled according to the actual parameters, and the refractive index and absorption coefficient of the materials are defined at the same time;

ii.对已经建立的几何模型进行网格划分；ii. Meshing the established geometric model;

iii.然后进行光场模拟，设置光场边界条件，通过求解麦克斯韦方程和电磁场微分方程得到不同大小的纳米颗粒在波导上引起的散射效率，从而得到纳米颗粒的大小的标定数据。本发明的优点：iii. Then carry out the light field simulation, set the boundary conditions of the light field, and obtain the scattering efficiency caused by nanoparticles of different sizes on the waveguide by solving the Maxwell equation and the differential equation of the electromagnetic field, so as to obtain the calibration data of the size of the nanoparticles. Advantages of the present invention:

本发明将单根波导以不产生耦合的条件下最大密度水平缠绕在基底的表面形成密集型波导，当附着在密集型波导表面的纳米颗粒位于波导模式的倏逝场范围内时，探测光被纳米颗粒散射或吸收，透射功率产生一个急剧下降的台阶信号，这个台阶信号编码了纳米颗粒的大小信息，计算机通过识别台阶信号判断纳米颗粒有无，并得到纳米颗粒的大小信息；本发明的密集型波导传感面积大，比直波导提高两个数量级；同时捕获效率高，时间响应快；能够探测的纳米颗粒的半径为100纳米的小球；另外TM偏振的波导模式的散射信号是TE偏振的30倍。In the present invention, a single waveguide is wound on the surface of the substrate at a maximum density level without coupling to form a dense waveguide. When the nanoparticles attached to the surface of the dense waveguide are located in the evanescent field range of the waveguide mode, the detection light is The nanoparticle scatters or absorbs, and the transmission power generates a sharply reduced step signal, which encodes the size information of the nanoparticle, and the computer judges the presence or absence of the nanoparticle by identifying the step signal, and obtains the size information of the nanoparticle; The sensing area of the waveguide is large, which is two orders of magnitude higher than that of the straight waveguide; at the same time, the capture efficiency is high and the time response is fast; the nanoparticles can be detected as small balls with a radius of 100 nanometers; in addition, the scattering signal of the TM-polarized waveguide mode is TE-polarized 30 times.

附图说明Description of drawings

图1为本发明的基于片上密集型波导的纳米颗粒传感器的一个实施例的示意图；1 is a schematic diagram of an embodiment of an on-chip dense waveguide-based nanoparticle sensor of the present invention;

图2为本发明的基于片上密集型波导的纳米颗粒传感器的一个实施例的密集型波导的电镜图；2 is an electron microscope image of a dense waveguide of an embodiment of the on-chip dense waveguide-based nanoparticle sensor of the present invention;

图3为本发明的基于片上密集型波导的纳米颗粒传感器的一个实施例的波导横磁模式和波导横电模式的强度图，其中，(a)为波导横磁TM模式的强度图，(b)为波导横电TE模式的强度图；3 is an intensity diagram of the waveguide transverse magnetic mode and the waveguide transverse electric mode of an embodiment of the on-chip dense waveguide-based nanoparticle sensor, wherein (a) is the intensity diagram of the waveguide transverse magnetic TM mode, (b) ) is the intensity map of the waveguide transverse electric TE mode;

图4为本发明的基于片上密集型波导的纳米颗粒传感方法的一个实施例得到的台阶信号的示意图；4 is a schematic diagram of a step signal obtained by an embodiment of the on-chip dense waveguide-based nanoparticle sensing method of the present invention;

图5为本发明的基于片上密集型波导的纳米颗粒传感器的一个实施例得到的密集型波导与直波导的纳米颗粒捕获效率对比图；FIG. 5 is a comparison diagram of the nanoparticle capture efficiency of the dense waveguide and the straight waveguide obtained by an embodiment of the on-chip dense waveguide-based nanoparticle sensor;

图6为本发明的基于片上密集型波导的纳米颗粒传感器的一个实施例得到的响应时间对比图，其中，(a)为密集型波导的响应时间图，(b)为直波导的响应时间图；6 is a response time comparison diagram obtained by an embodiment of the on-chip dense waveguide-based nanoparticle sensor of the present invention, wherein (a) is the response time diagram of the dense waveguide, and (b) is the response time diagram of the straight waveguide ;

图7为本发明的基于片上密集型波导的纳米颗粒传感器的一个实施例得到的台阶信号与纳米颗粒的大小的关系图，其中，(a)为实验测量得到不同大小的纳米颗粒在密集型波导上引起的台阶信号统计分布图，(b)给出了密集型波导对于纳米颗粒的大小测量的不确定度。FIG. 7 is a graph showing the relationship between the step signal and the size of nanoparticles obtained by an embodiment of the nanoparticle sensor based on the on-chip dense waveguide of the present invention, wherein (a) is the experimental measurement of nanoparticles of different sizes in the dense waveguide. Statistical distribution of the signal caused by the step on the top, (b) gives the uncertainty of the size measurement of the nanoparticles for the dense waveguide.

具体实施方式Detailed ways

下面结合附图，通过具体实施例，进一步阐述本发明。Below in conjunction with the accompanying drawings, the present invention will be further described through specific embodiments.

如图1所示，本实施例的基于片上密集型波导的纳米颗粒传感器包括：基底、单根波导、光源装置、第一和第二光纤波导耦合器3和4、光电探测器5、数据采集卡6和计算机；其中，光源装置包括激光器1和函数发生器2；单根波导以的条件下最大密度水平缠绕在基底的表面，缠绕形成的形状的曲率半径大于5μm，以降低光的损耗，从而在基底的表面形成密集型波导7；在单根波导的一端设置第一光纤波导耦合器3，在单根波导的另一端设置第二光纤波导耦合器4；光电探测器5连接至数据采集卡6；数据采集卡6连接至计算机。As shown in FIG. 1 , the on-chip dense waveguide-based nanoparticle sensor of this embodiment includes: a substrate, a single waveguide, a light source device, first and secondfiber waveguide couplers 3 and 4 , aphotodetector 5 , a data acquisition Card 6 and computer; wherein, the light source device includes a laser 1 and afunction generator 2; a single waveguide is wound on the surface of the substrate at the maximum density level under the condition, and the radius of curvature of the shape formed by the winding is greater than 5 μm to reduce the loss of light, Thus, a dense waveguide 7 is formed on the surface of the substrate; a firstfiber waveguide coupler 3 is set at one end of a single waveguide, and a second fiber waveguide coupler 4 is set at the other end of the single waveguide; thephotodetector 5 is connected to the data acquisition card 6; data acquisition card 6 is connected to the computer.

在本实施例中，单根波导以螺旋形水平缠绕在基底的表面，电镜图如图2所示；单根波导的横截面的宽度为500nm，高为220nm；基底采用形成在硅上的二氧化硅。In this embodiment, a single waveguide is horizontally wound on the surface of the substrate in a spiral shape, and the electron microscope image is shown in Fig. 2; the width of the cross section of the single waveguide is 500 nm and the height is 220 nm; Silicon oxide.

利用超声雾化器处理标准聚苯乙烯小球溶液产生单纳米颗粒，并利用微流泵将它沉积在密集型波导上，对应的流速设为10mL min^-1。利用一个低噪声光电探测器和数据采集卡监测波导的实时透射功率，数据采集卡的采样率是100kS/s。Single nanoparticles were produced by treating standard polystyrene bead solutions with an ultrasonic nebulizer, and deposited on dense waveguides using a microfluidic pump at a corresponding flow rate of 10 mL min^-1 . The real-time transmitted power of the waveguide is monitored using a low-noise photodetector and a data acquisition card with a sampling rate of 100kS/s.

如图3所示，TM偏振的波导模式的散射信号是TE偏振的30倍。As shown in Fig. 3, the scattering signal of the waveguide mode of TM polarization is 30 times higher than that of TE polarization.

如图4所示，半径为100nm的标准聚苯乙烯小球在沉积到波导过程中，经过波导后探测光的光强透射率的响应曲线。图4上的每一个台阶信号代表波导检测到了一个纳米颗粒。As shown in Figure 4, the response curve of the light intensity transmittance of probe light after passing through the waveguide during the deposition of standard polystyrene spheres with a radius of 100 nm into the waveguide. Each step signal in Figure 4 represents a nanoparticle detected by the waveguide.

如图5所示，当纳米颗粒的沉积范围为百微米量级时，密集型波导相比直波导在纳米颗粒的捕获效率上提高了两个量级。As shown in Figure 5, when the deposition range of nanoparticles is in the order of hundreds of microns, the dense waveguide improves the capture efficiency of nanoparticles by two orders of magnitude compared to the straight waveguide.

如图6所示，在相同的测试条件下，当纳米颗粒的沉积面积在30微米时，密集型波导的响应时间是直波导的5倍以上。As shown in Figure 6, under the same test conditions, when the deposition area of nanoparticles is 30 μm, the response time of the dense waveguide is more than 5 times that of the straight waveguide.

如图7(a)所示，当密集型波导检测不同半径的标准聚苯乙烯小球的时候，密集型波导检测得到的台阶信号会随着小球的尺寸的增加而增加。另外，由于波导模式的倏势场在波导面并不均匀，如图3所示，因此对于相同尺寸的纳米颗粒落在密集型波导横截面的不同位置时，引起的台阶信号(散射效率)的大小并不相同。图7(b)给出了纳米颗粒在波导上引起的散射效率与纳米颗粒的半径以及纳米颗粒落在密集型波导的横截面的位置之间的关系。对于TM模式的探测光，密集型波导在测量聚苯乙烯小球时的尺寸不确定度大约为10％。也就是说，当密集型波导检测到一个散射效率为1％的台阶信号，对应的纳米颗粒的半径为157.3±14.6nm。As shown in Fig. 7(a), when the dense waveguide detects standard polystyrene spheres with different radii, the step signal detected by the dense waveguide increases with the increase of the size of the sphere. In addition, since the potential field of the waveguide mode is not uniform on the waveguide surface, as shown in Fig. 3, when nanoparticles of the same size fall on different positions of the dense waveguide cross-section, the resulting step signal (scattering efficiency) has Sizes are not the same. Fig. 7(b) presents the relationship between the scattering efficiency induced by nanoparticles on the waveguide and the radius of the nanoparticles and the position where the nanoparticles fall on the cross-section of the dense waveguide. For the probe light in the TM mode, the dimensional uncertainty of the dense waveguide is about 10% when measuring polystyrene spheres. That is, when the dense waveguide detects a step signal with a scattering efficiency of 1%, the corresponding nanoparticle has a radius of 157.3±14.6 nm.

最后需要注意的是，公布实施例的目的在于帮助进一步理解本发明，但是本领域的技术人员可以理解：在不脱离本发明及所附的权利要求的精神和范围内，各种替换和修改都是可能的。因此，本发明不应局限于实施例所公开的内容，本发明要求保护的范围以权利要求书界定的范围为准。Finally, it should be noted that the purpose of publishing the embodiments is to help further understanding of the present invention, but those skilled in the art can understand that various replacements and modifications can be made without departing from the spirit and scope of the present invention and the appended claims. It is possible. Therefore, the present invention should not be limited to the contents disclosed in the embodiments, and the scope of protection of the present invention shall be subject to the scope defined by the claims.

Claims (4)

1. A nanoparticle sensing method based on-chip dense waveguides is characterized by comprising the following steps:

1) the light source device emits detection light which enters the dense waveguide through the first optical fiber waveguide coupler; after the transmission of the dense waveguide, the transmission light is received by the photoelectric detector through the second optical fiber waveguide coupler;

2) the photoelectric detector converts the optical signal into an electric signal and transmits the electric signal to the data acquisition card for analog-to-digital conversion and acquisition; then transmitting the data to a computer for mean value filtering processing and extracting a sensing signal;

3) when the nano particles attached to the surface of the dense waveguide are positioned in the evanescent field range of the waveguide mode of the dense waveguide, the probe light is scattered or absorbed by the nano particles, and the transmission power generates a step signal which sharply drops, wherein the step signal encodes the size information of the nano particles;

4) the computer identifies the step signal, and judges whether the nano-particles exist or not through the step signal, so as to further obtain the size information of the nano-particles:

a) dividing data in a time interval of data acquisition into a plurality of processing units, wherein in order to enable an algorithm to be free from the influence of a slowly varying signal caused by the environment when extracting a signal and simultaneously identify two step signals with a close time interval, the time area of the processing unit is 0.06 s-0.1 s;

b) calculating the difference between the average values of the (N-1) th processing unit and the (N +1) th processing unit before and after the calculation, wherein N is a natural number more than or equal to 10;

c) and identifying the step by comparing the obtained difference with the noise level of the signal in the interval of the (N-M) th processing unit and the (N + M) th processing unit, thereby obtaining a step signal, wherein M is a natural number less than or equal to N, and M is more than or equal to 10 and less than or equal to 100.

2. The sensing method of claim 1, wherein each step signal represents the detection of a nanoparticle, such that the presence or absence of a nanoparticle is determined from the identified step signals.

3. The sensing method of claim 1, wherein obtaining information on the size of the nanoparticle from the step signal comprises:

a) obtaining the scattering efficiency caused by the nano particles on the surface of the waveguide according to the step signal, wherein the scattering efficiency is equal to the detected light intensity reduction power corresponding to the step divided by the total power of the detected light;

b) then, according to the size of the scattering efficiency, the particle size range of the nano particles is found on calibration data obtained by finite element simulation, so that the size of the nano particles at the moment is obtained.

4. A sensing method according to claim 3, wherein in step b) calibration data is obtained by finite element simulation, comprising the steps of:

i. firstly, geometrically modeling the materials of the dense waveguide, the nano particles and the substrate according to actual parameters, and defining the refractive index and the absorption coefficient of the materials at the same time;

meshing the established geometric model;

and iii, performing light field simulation, setting light field boundary conditions, and solving Maxwell equations and electromagnetic field differential equations to obtain the scattering efficiency of the nano particles with different sizes on the waveguide, so as to obtain the calibration data of the sizes of the nano particles.

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