CN109781709B - Optical amplification Raman spectrum detection system based on waveguide structure - Google Patents
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Abstract
The invention provides a light amplification Raman spectrum detection system based on a waveguide structure, which comprises a laser light source, a Raman probe unit, a sensing unit and a filtering unit, wherein the Raman probe unit is arranged on the laser light source; the laser light source is coupled with the input end of the sensing unit; the output end of the sensing unit is connected with the input end of the filtering unit; the Raman probe unit is arranged at the output end of the filtering unit; molecules to be detected are attached to the upper surface of the sensing unit; the whole Raman spectrum detection system is realized on a chip by using a waveguide structure, so that the miniaturization and the chip-based detection system are realized, the monitoring sensing unit adopts the waveguide structure consisting of a gain medium with a light amplification function and a surface enhanced Raman layer to amplify the monitored weak Raman signals, the filtering units with different microring sizes are adopted to filter and modulate the Raman optical signals with different wavelengths, the tunable filtering detection is realized, the whole device is convenient to carry and detect molecules to be detected, and the Raman optical signals with different wavelengths can be accurately detected.
Description
Technical Field
The invention relates to the technical field of molecular spectrum detection, in particular to a light amplification Raman spectrum detection system based on a waveguide structure.
Background
The spectrum reflects the characteristics of electronic transition, molecular vibration, rotation and the like of a substance, and molecular spectrum detection is an important technical means for qualitative and quantitative determination of the substance. Common spectrum analyzers are presented in the form of large (bench-top) analytical instruments, are expensive, large in size, complex to operate, high in requirements for use environments, and suitable for laboratories. The Raman scattering is caused by energy transfer caused by inelastic collision between light and molecules, scattered light has certain frequency change compared with incident light, the frequency change amount corresponds to the inherent vibration energy level of the molecules and is the 'fingerprint' of the molecules, the laser Raman scattering spectroscopy adopts single-wavelength laser to irradiate a measured object, the Raman scattering spectrum of the measured object is detected and analyzed to identify the fingerprint spectrum line of the measured molecule, qualitative and quantitative measurement is carried out, and the detection accuracy is high. The laser Raman scattering spectroscopy is a method which can realize trace, multi-species and rapid gas detection; most of the existing Raman spectrometersIs designed for on-site gas monitoring, and has the following two disadvantages: (I) the Raman scattering cross section is small, and the scattering signal is extremely weak (Rayleigh scattering-10)-6Multiple); in addition, the volume molarity of the gas is very low, and few molecules participate in scattering; meanwhile, the gas Raman scattering light is dispersed in a 4 pi space and is very difficult to collect; due to the factors, the utilization efficiency of light energy in gas Raman scattering measurement is low, the detection sensitivity is low, and the detection limit cannot meet the requirement of monitoring atmospheric pollution. Secondly, the large-scale Raman spectrometer has large volume, grating rotating parts and high requirements on the use environment, and is not suitable for field monitoring.
In recent years, the demand for rapid substance analysis on site in the fields of food, medicine, environmental protection, security inspection, explosion prevention and anti-terrorism is increasing; the new requirements lead the spectroscopic instruments to show the development trend of miniaturization and miniaturization. In recent years, the development of technologies such as cloud computing, big data and AI of the Internet brings a change to the mode of an analytical instrument; the front end of the instrument only needs data acquisition and a networking chip, and analysis can be completed by background cloud computing. Therefore, the intelligent system of the instrument can be integrated into a chip (chip set) with a small volume, and if the detection system can be further miniaturized and chipped, the spectrum instrument can be developed into a spectrum chip sensor and becomes the touch sense of the front end of the Internet of things. This is also a problem to be solved by the present application.
Disclosure of Invention
In view of the above, an object of the present invention is to provide an optical amplification raman spectrum detection system based on a waveguide structure, in which the entire raman spectrum detection system is implemented on a chip by using the waveguide structure, so as to realize miniaturization and chip-based detection system, a monitoring and sensing unit employs a waveguide structure composed of a gain medium with an optical amplification function and a surface enhanced raman layer to amplify a monitored weak raman signal, and employs filtering units with different micro-ring sizes to filter and modulate raman optical signals with different wavelengths, so as to implement tunable filtering detection.
The invention provides a light amplification Raman spectrum detection system based on a waveguide structure, which comprises a laser, a Raman probe unit, a sensing unit and a filtering unit, wherein the Raman probe unit is used for detecting Raman spectrum;
the laser is coupled with the input end of the sensing unit; the output end of the sensing unit is connected with the input end of the filtering unit; the Raman probe unit is arranged at the output end of the filtering unit; molecules to be detected are attached to the upper surface of the sensing unit;
the sensing unit includes: a waveguide structure layer and a surface enhanced Raman layer; the waveguide structure layer comprises a substrate and a waveguide layer; the waveguide layer is deposited on the upper surface of the substrate, and the refractive index of the waveguide layer is greater than that of the substrate; the surface enhanced Raman layer is formed on the upper surface of the guided wave layer and is used for enhancing a surface electromagnetic field, improving the Raman excitation efficiency of molecules to be detected and realizing a self-calibration function; the molecules to be detected are attached to the upper surface of the surface enhanced Raman layer.
Further, the guided wave layer is a strip waveguide; the laser is coupled and connected with the input end of the strip waveguide through a coupler; and the output end of the strip waveguide is connected with the input end of the filtering unit.
Further, the surface-enhanced raman layer is one of: a composite layer of the carbon nanotube film and the metal nanoparticles, and a composite layer of the graphene and the metal nanoparticles.
Further, the metal nanoparticles are one of: gold nanoparticles, silver nanoparticles, or gold-silver alloy nanoparticles.
Further, the filtering unit comprises N micro-ring resonators which are connected in sequence; the micro-ring resonator comprises a micro-ring waveguide, an input optical waveguide, a straight-through optical waveguide and a download optical waveguide; wherein N is more than or equal to 3; the radius sizes of the micro-ring waveguides of the N micro-ring resonators are different and are used for performing resonance filtering on Raman optical signals with different wavelengths;
the input optical waveguide of the 1 st micro-ring resonator is used as the input end of the filtering unit and is connected with the output end of the sensing unit; the through optical waveguides of the 1 st, 2 nd, … … th and N-1 st micro-ring resonators are connected with the input optical waveguides of the 2 nd, … … th and N-th micro-ring resonators;
and the micro-ring resonator download optical waveguide is connected with the Raman probe unit.
Further, the raman probe unit includes N single-point detectors, and the N single-point detectors are respectively connected to the downloaded optical waveguides of the N micro-ring resonators, and are configured to detect raman optical signals of various wavelengths.
Furthermore, the thickness of the wave guide layer is between 300nm and 600nm, the width of the wave guide layer is between 500nm and 900nm, and the material of the wave guide layer is silicon nitride.
Further, the thickness dimension of the substrate is larger than that of the wave guiding layer, the width dimension of the substrate is larger than that of the wave guiding layer, the length dimension of the substrate is larger than that of the wave guiding layer, and the substrate is made of silicon oxide.
The invention has the beneficial effects that: the whole Raman spectrum detection system is realized on a chip by using a waveguide structure, so that the miniaturization and the chip of the detection system are realized, the monitoring sensing unit adopts the waveguide structure consisting of a gain medium with a light amplification function and a surface enhanced Raman layer to amplify the monitored weak Raman signals, the filtering units with different micro-ring sizes are adopted to filter and modulate the Raman optical signals with different wavelengths, the tunable filtering detection is realized, the whole device has small volume, is convenient to carry and detect molecules to be detected, has low cost, and can accurately detect the Raman optical signals with different wavelengths.
Drawings
The invention is further described below with reference to the following figures and examples:
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic diagram of a sensing unit monitoring a molecule to be detected;
FIG. 3 is a schematic top view of a sensing unit;
fig. 4 is a schematic front view of a sensing unit.
FIG. 5 is a schematic diagram of a sensing unit of spherical metal nanoparticles;
FIG. 6 is a schematic diagram of a sensing unit of rod-shaped metal nanoparticles;
FIG. 7 is a schematic view of a waveguide structure layer;
FIG. 8 is a diagram of a single-mode guided mode optical field distribution of a slab waveguide (waveguide structure layer) calculated by numerical simulation;
FIG. 9 is a diagram of a bimodal guided-mode optical field distribution of a slab waveguide (waveguide structure layer);
FIG. 10 is a schematic illustration of local electric field enhancement;
FIG. 11 is a schematic diagram of a microring resonator;
fig. 12 shows the resonated optical wavelength information output from the filter unit.
Detailed Description
As shown in fig. 1, the optical amplification raman spectrum detection system based on the waveguide structure provided by the present invention includes a laser 1-1, a raman probe unit, a sensing unit 1-3 and a filtering unit; in fig. 1, 1-1 denotes a laser, 1-2 denotes a coupler, 1-3 denotes a sensing unit, 1-4, 1-5, 1-6 denotes micro-ring waveguides of 1 st, 2 nd, and nth micro-ring resonators, 1-7, 1-8, 1-9 denotes download optical waveguides of 1 st, 2 nd, and nth micro-ring resonators, respectively, and 1-10, 1-11, 1-12 denotes 1 st, 2 nd, and nth single-point detectors connected to the download optical waveguides of the 1 st, 2 nd, and nth micro-ring resonators, respectively.
The laser 1-1 is coupled with the input end of the sensing unit 1-3; the output end of the sensing unit is connected with the input end of the filtering unit; the Raman probe unit is arranged at the output end of the filtering unit; as shown in fig. 2, a molecule to be measured is attached to the upper surface of the sensing unit; the rectangles in FIG. 2 represent the sensing cells, 2-1 the molecules to be detected, λLDenotes the wavelength of the laser light, lambda, emitted by the laser 1-1RIndicating the wavelength of the raman light induced.
As shown in fig. 3 and 4, the sensing unit includes: a waveguide structure layer and a surface enhanced Raman layer; the waveguide structure layer comprises a substrate and a waveguide layer; the waveguide layer is deposited on the upper surface of the substrate, and the refractive index of the waveguide layer is greater than that of the substrate; the surface enhanced Raman layer is formed on the upper surface of the guided wave layer and is used for enhancing a surface electromagnetic field, improving the Raman excitation efficiency of molecules to be detected and realizing a self-calibration function; the molecules to be detected are attached to the upper surface of the surface enhanced Raman layer. Through the structure, the whole waveguide structure for the Raman spectrum detection system is realized on a chip, the miniaturization and the chip of the detection system are realized, the monitoring and sensing unit adopts the waveguide structure consisting of the gain medium with the light amplification function and the surface enhanced Raman layer to amplify the monitored weak Raman signals, the filtering unit is adopted to carry out filtering modulation on the Raman optical signals with different wavelengths, the tunable filtering detection is realized, the whole device is small in size, the carrying and the detection of molecules to be detected are convenient, the cost is low, and the Raman optical signals with different wavelengths can be accurately detected. In fig. 3 and 4, 1-3-1 denotes a waveguide structure layer, and 1-3-2 denotes a surface enhanced raman layer.
The guided wave layer is a strip waveguide; the laser is coupled and connected with the input end of the strip waveguide through a coupler; and the output end of the strip waveguide is connected with the input end of the filtering unit.
The surface-enhanced Raman layer is one of the following: a composite layer of the carbon nanotube film and the metal nanoparticles, and a composite layer of the graphene and the metal nanoparticles.
The metal nano-particles are one of the following: gold nanoparticles, silver nanoparticles, or gold-silver alloy nanoparticles. As shown in fig. 3, 5 and 6, the metal nanoparticles may be spherical, triangular, rod-like, or the like, and the distance between two adjacent particles is 10nm or less. The metal nano particles are used for realizing local surface Raman enhancement and are excited by evanescent waves of the waveguide. The carbon nanotube film and the graphene are used for realizing a self-calibration function. Specifically, due to the fact that the raman intensity of molecules to be measured with the same concentration has great fluctuation caused by substrate nonuniformity, manual operation of system test, fluctuation of instrument light sources and the like, quantitative analysis is difficult to achieve. Therefore, a composite layer of the carbon nano tube film and the metal nano particles or a composite layer of the graphene and the metal nano particles is used as a surface enhanced Raman layer, Raman information tested by a Raman detection system comprises a molecule to be tested and a characteristic peak of the graphene or the carbon nano tubes, and Raman intensity information of the molecule to be tested is calibrated by using the 2D characteristic peak intensity of the graphene or the carbon nano tubes, so that the fluctuation of the Raman intensity of the molecule to be tested caused by substrate nonuniformity, manual operation of system testing, instrument light source fluctuation and the like can be eliminated. This method of quantitative analysis, which is carried by the surface enhanced Raman layer, is called self-calibration function. Specifically, the preparation method of the composite layer of the carbon nanotube film and the metal nanoparticles comprises the following steps: adding a carbon nano tube film solution in the process of preparing the metal nano particles to obtain a carbon nano tube film metal nano particle compound I; and further adding a metal nanoparticle solution into the compound I according to a certain volume ratio to obtain a secondary compound of the carbon nanotube film and the metal nanoparticles. The secondary compound is a final compound layer of the carbon nano tube film and the metal nano particles, and has high sensitivity and a self-calibration function. Specifically, the preparation method of the graphene and metal nanoparticle composite layer comprises the following steps: the method comprises the steps of firstly evaporating a layer of metal film on the upper surface of a wave guide layer, then forming metal nano particles by an annealing method, transferring a layer of graphene, then annealing, evaporating a layer of metal nano film, and then annealing to finally obtain a nano particle/graphene/nano particle sandwich structure. The sandwich structure is a graphene and metal nanoparticle composite layer, and has high sensitivity and a self-calibration function. Fig. 3 shows that the metal nanoparticles are triangular, fig. 5 shows that the metal nanoparticles are spherical, and fig. 6 shows that the metal nanoparticles are rod-shaped.
The thickness of the wave guide layer is between 300nm and 600nm, the width of the wave guide layer is between 500nm and 900nm, and the material of the wave guide layer is silicon nitride.
The thickness dimension of the substrate is larger than that of the wave guide layer, the width dimension of the substrate is larger than that of the wave guide layer, the length dimension of the substrate is larger than that of the wave guide layer, and the substrate is made of silicon oxide.
The sensing unit mainly has three functions in the whole device, including functions of transmitting excitation light (laser emitted by a laser), transmitting molecular Raman light to be detected and amplifying the Raman light, and specifically comprises the following functions:
firstly, transmitting excitation light, evanescent wave excitation and transmitting molecular Raman light to be detected
Because of the Raman signalIn the spectral range of 532-676nm, the conventional soi (silicon on insulator) optical waveguide device operating in the communication band (1500nm) is not suitable, and the silicon nitride material is not absorbed in this band and belongs to the conventional silicon processing technology. Therefore, the substrate of the optical waveguide device in this patent is SiO2And the waveguide layer is Si3N4And cladding air have refractive indexes of 1.89 and 1, respectively, and the refractive index difference between the two is larger than that of Si and SiO in conventional SOI optical waveguide2(3.45 and 1.46) are smaller than half, the light is relatively weakly confined by the waveguide composed of them, and the condition of single-mode transmission in the waveguide is relatively loose.
The waveguide structure layer is used for a sensing part, (1) more than two modes are needed in the waveguide in order to ensure that the upper surface of the waveguide has evanescent waves; (2) to ensure the size, distribution and processing of the metallic nanostructures for localized light enhancement, the width of the waveguide needs to be sufficiently large. In order to solve the above two problems, in the stripe waveguide structure (waveguide structure layer) shown in fig. 7, the confinement of the optical field by the stripe waveguide is strong in the vertical direction, but is relatively weak in the horizontal direction. Fig. 8 is a single-mode guided-mode optical field distribution diagram of a slab waveguide (waveguide structure layer) calculated by numerical simulation. Fig. 9 is a diagram of a bimodal guided-mode optical field distribution of a slab waveguide (waveguide structure layer) with more mode field contact with the upper surface of the waveguide, and the bimodal condition is that the slab waveguide has a thickness (H) above 300nm and a width (W) above 500nm, and the larger the width, the more modes are allowed to exist. Further, in the realization of the whole system function under consideration, the thickness (H) of the strip waveguide needs to be set within 600nm and the width needs to be set within 900 nm.
Furthermore, the intensity of the Raman optical signal generated by the evanescent wave and the molecule to be detected is very weak, the metal nano structure can enhance the intensity of the Raman optical signal, and the enhancement coefficient reaches 107So that it is strong enough to perform filtering demodulation processing in the subsequent filtering unit. The surface plasmon is based on the collective oscillation effect of free electrons in metal under a photoelectric field. Because the energy gaps of d electrons and s electrons of two IB group metals of Ag and Au are large compared with those of transition metals, the two IB group metals are not easy to generate interband transition. As long asBy selecting an appropriate excitation light wavelength for these 2 metal systems, the energy of absorbed light can be prevented from being converted into heat or the like due to the occurrence of band-to-band transition, and thus a highly efficient SPR (surface plasmon resonance) scattering process tends to be realized. As shown in FIG. 10, assuming that the average electric field enhancement factor of the particle surface is g, then at E0Average local near field E of the surface of the metal particle under the incident fieldS＝gE0The Raman optical electric field thus generated has ER∝αRES∝αRgE0(αRPolarizability of molecules adsorbed on metal surfaces, ERRepresenting a raman optical electric field). Besides the incident field, the Raman light is enhanced by the metal particles by g '(the enhancement factor g' ≠ g because the Raman light is different from the incident light frequency), so that the enhanced Raman field intensity ER∝αRgg′E0I.e. intensity IR∝|αR|2|gg′|2I0，IRAnd I0The raman light intensity and the incident excitation light intensity are shown separately, and there are many shapes and structures of metal nanoparticles for enhancing the raman spectrum intensity as shown in fig. 3, 5 and 6, in which three sizes of metal nanoarrays functioning at one wavelength size (nanometer scale) are illustrated.
Further, the laser emits laser light, the laser light enters the sensing unit through the coupler, total reflection occurs in the sensing unit (when the light is transmitted in the waveguide structure layer, the total reflection occurs at the interface where the waveguide structure 1 is in contact with the air medium 2 when a certain transmission condition is met due to the refractive index difference between the waveguide structure 1 and the external air medium 2), the light wave is not totally reflected back into the medium 1 (waveguide structure layer) but penetrates into a very thin surface (about one wavelength) in the medium 2 (air) during the total reflection, and propagates for a short distance (wavelength magnitude) along the interface, and finally returns into the waveguide. This wave, which penetrates the surface of the medium 2, is called an evanescent wave, which decays exponentially in air, the amplitude of the evanescent wave decreasing very rapidly as the depth of penetration into the medium 2 increases, a depth which typically defines the amplitude decrease to 1/e of the amplitude at the interface as the penetration depth, which is about one wavelength. And at total reflection there is an evanescent wave in the medium 2, but it does not transfer energy into the medium 2. Calculations show that the average power flow of the evanescent wave in the vertical direction is zero, which indicates that the energy flowing into medium 2 from medium 1 and returning from medium 2 to medium 1 is equal. Surface raman enhancement: the evanescent wave and the gas molecules to be detected falling on the upper surface of the waveguide act to generate a weak Raman spectrum. The metal nano structure is processed on the upper surface of the waveguide, surface plasma resonance is generated to cause local electric field enhancement, so that the intensity of a Raman spectrum is enhanced, and the Raman spectrum returns to the waveguide and is transmitted to the filtering unit for filtering demodulation treatment.
Secondly, amplifying the Raman light
In this embodiment, the waveguide structure layer is formed by a gain medium having an amplification function, and the gain medium is implemented by a doping process, and specifically, the waveguide layer is made of a silicon nitride material, and first, the indirect energy band structure of silicon can be converted into discrete energy levels by using a silicon-based nanostructure and a quantization effect, so that the recombination efficiency is improved and the optical gain is increased. Such as: preparing silicon nitride by adopting Plasma Enhanced Chemical Vapor Deposition (PECVD) and ion implantation silicon ion technology, then annealing at high temperature to generate inlaid silicon nanocrystals in the silicon nitride, and generating light amplification under the excitation of laser, wherein the gain coefficient reaches 100 times per centimeter; secondly, special doping or ion implantation can be adopted to form energy levels or dislocation loops, energy levels are introduced, the energy levels are utilized to realize the radiation recombination of electron-hole pairs between the energy levels and sidebands or between the energy levels, the participation of phonons is avoided, the internal gain is effectively improved, and for example, the method for preparing Er through laser ablation3+A silicon nitride film co-doped with the silicon nanocrystals is used for manufacturing an optical waveguide structure on the basis, and a strong laser pulse light source of a 532nmYAG laser is used for pumping to enable the super-linear lasing output caused by Er3+ ions; thirdly, other processes can be adopted to prepare the wave guide layer by utilizing the silicon nitride material, so that the wave guide layer has the optical amplification effect.
Further, as shown in fig. 1, the filtering unit includes N micro-ring resonators connected in sequence; the micro-ring resonator comprises a micro-ring waveguide, an Input optical waveguide, a through optical waveguide and a Download optical waveguide, in the embodiment, the Input optical waveguide is connected with the through optical waveguide to form a through optical waveguide i, the through optical waveguide i is parallel to the Download optical waveguide, the micro-ring waveguide is arranged between the through optical waveguide and the Download optical waveguide and is respectively coupled with the through optical waveguide and the Download optical waveguide, as shown in fig. 11, the micro-ring waveguide, the Input optical waveguide, the through optical waveguide and the Download optical waveguide form an uplink and downlink filter, and the uplink and downlink filter is provided with four port Input ends (Input), a direct Output end (Output), a Download end (Download) and an upload end (Output). Wherein N is more than or equal to 3; the radius sizes of the micro-ring waveguides of the N micro-ring resonators are different and are used for performing resonance filtering on Raman optical signals with different wavelengths; in the embodiment, the N micro-ring resonators are sequentially connected in series, and a thermal modulation mechanism or an electric modulation mechanism is not needed for modulating the micro-ring waveguide, so that the whole device is simplified.
The input optical waveguide of the 1 st micro-ring resonator is used as the input end of the filtering unit and is connected with the output end of the sensing unit; the through optical waveguides of the 1 st, 2 nd, … … th and N-1 st micro-ring resonators are connected with the input optical waveguides of the 2 nd, … … th and N-th micro-ring resonators;
and the micro-ring resonator download optical waveguide is connected with the Raman probe unit.
The Raman probe unit comprises N single-point detectors, and the N single-point detectors are respectively connected with the downloaded optical waveguides of the N micro-ring resonators and used for detecting Raman optical signals with various wavelengths. As shown in fig. 11 and 12, the micro-ring resonators of different sizes of micro-rings calculated the wavelength of the filtered raman light based on the following formula:
wherein k is1And k2The amplitude coupling efficiency, t, of the micro-ring waveguide with the input optical waveguide and the drop optical waveguide, respectively1And t2Amplitude transmission efficiency of the micro-ring waveguide, the straight-through optical waveguide I and the down-loading optical waveguide respectively, alpha is an in-ring attenuation factor, and theta is equal to n eff2 π R/λ is the phase change around the ring for one revolution, R is the ring radius, neffλ is the wavelength of light in vacuum, which is the effective refractive index of the ring waveguide. λ in FIG. 12R1、λR2、……、λRkRespectively, the wavelengths of light resonated by the 1 st, 2 nd, … … th and k-th micro-ring resonators, Et1、Et2、Ei2、Ei1Respectively showing the amplitude of the straight-through optical waveguide I, the amplitude of the down-loading end of the down-loading optical waveguide, the amplitude of the incident light of the straight-through optical waveguide I, the amplitude of the up-loading end of the down-loading optical waveguide, k1 *And k2 *The amplitude coupling efficiency of the micro-ring waveguide with the straight-through optical waveguide I and the down-loading optical waveguide is respectively shown. The intensity in fig. 12 refers to the intensity of light.
When actually designing the radius size of each micro-ring waveguide, the radius size of each micro-ring waveguide can be calculated by the formula (1) backward extrapolation according to the known raman light wavelength of various molecules, and each micro-ring resonator is manufactured according to the calculated radius size of each micro-ring waveguide. The filtering unit adopts a micro-ring resonant cavity structure and has the following advantages: (1) the micro-ring resonance does not need a mirror surface or a grating to improve the optical feedback, so the process is simpler and easier to realize, and the micro-ring resonance is suitable for photonic device integration on a chip; (2) the micro-ring is a traveling wave resonant cavity and supports a degenerate mode with opposite transmission directions, so that optical paths of input light, transmitted light and reflected light are not overlapped, the transmission path of the light is easier to control, and the micro-ring is convenient to combine with other photonic elements.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.
Claims (4)
1. A light amplification Raman spectrum detection system based on a waveguide structure is characterized in that: the Raman probe comprises a laser, a Raman probe unit, a sensing unit and a filtering unit;
the laser is coupled with the input end of the sensing unit; the output end of the sensing unit is connected with the input end of the filtering unit; the Raman probe unit is arranged at the output end of the filtering unit; molecules to be detected are attached to the upper surface of the sensing unit;
the sensing unit includes: a waveguide structure layer and a surface enhanced Raman layer; the waveguide structure layer comprises a substrate and a waveguide layer; the waveguide layer is deposited on the upper surface of the substrate, and the refractive index of the waveguide layer is greater than that of the substrate; the surface enhanced Raman layer is formed on the upper surface of the guided wave layer and is used for enhancing a surface electromagnetic field, improving the Raman excitation efficiency of molecules to be detected and realizing a self-calibration function; molecules to be detected are attached to the upper surface of the surface enhanced Raman layer;
the guided wave layer is a strip waveguide; the laser is coupled and connected with the input end of the strip waveguide through a coupler; the output end of the strip waveguide is connected with the input end of the filtering unit;
the filtering unit comprises N micro-ring resonators which are connected in sequence; the micro-ring resonator comprises a micro-ring waveguide, an input optical waveguide, a straight-through optical waveguide and a download optical waveguide; wherein N is more than or equal to 3; the radius sizes of the micro-ring waveguides of the N micro-ring resonators are different and are used for performing resonance filtering on Raman optical signals with different wavelengths;
the input optical waveguide of the 1 st micro-ring resonator is used as the input end of the filtering unit and is connected with the output end of the sensing unit; the through optical waveguides of the 1 st, 2 nd, … … th and N-1 st micro-ring resonators are connected with the input optical waveguides of the 2 nd, … … th and N-th micro-ring resonators;
the micro-ring resonator download optical waveguide is connected with the Raman probe unit;
the surface-enhanced Raman layer is one of the following: a composite layer of a carbon nanotube film and metal nanoparticles, a composite layer of graphene and metal nanoparticles;
the thickness of the wave guide layer is between 300nm and 600nm, the width of the wave guide layer is between 500nm and 900nm, and the material of the wave guide layer is silicon nitride.
2. The waveguide structure-based optically amplified raman spectroscopy detection system of claim 1, wherein: the metal nano-particles are one of the following: gold nanoparticles, silver nanoparticles, or gold-silver alloy nanoparticles.
3. The waveguide structure-based optically amplified raman spectroscopy detection system of claim 2, wherein: the Raman probe unit comprises N single-point detectors, and the N single-point detectors are respectively connected with the downloaded optical waveguides of the N micro-ring resonators and used for detecting Raman optical signals with various wavelengths.
4. The waveguide structure-based optically amplified raman spectroscopy detection system of claim 3, wherein: the thickness dimension of the substrate is larger than that of the wave guide layer, the width dimension of the substrate is larger than that of the wave guide layer, the length dimension of the substrate is larger than that of the wave guide layer, and the substrate is made of silicon oxide.
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