1. A high-integration surface plasma resonance sensor system is composed of a broadband light source (1), a sample cell (2), a metal film (3), a prism (4), a focusing lens (5), a photoelectric detector (6), a bias voltage circuit (7), a main control system (8), a photoelectric signal processing circuit (9) and a polaroid (10); when the system works, a sample is introduced into the sample cell (2), light emitted from the broadband light source (1) is adjusted into P polarized light through the polaroid (10), light beams are incident on the metal film (3) through the prism (4), and surface plasma waves are generated on the interface of the metal film (3) and an object to be measured; the system adjusts the wavelength or the incident angle of light emitted by the broadband light source (1), so that the surface plasma wave and the incident light generate a surface plasma resonance phenomenon under a certain condition; light beams reflected from the metal film (3) enter the photoelectric detector (6) through the prism (4) and the focusing lens, signals generated by the photoelectric detector (6) are input to the main control system (8) through the photoelectric signal processing circuit (9), the bias voltage circuit (7) provides fixed voltage for the main control system (8) so as to enable the main control system to work normally, bias voltage provided by the bias voltage circuit (7) for the photoelectric detector (6) is controlled by the main control system (8), and spectral response functions of the photoelectric detector (6) under different bias voltages are tested in advance and are obtained and stored in the main control system (8); the main control system (8) takes the signals and the spectral response function obtained from the photoelectric signal processing circuit (9) as input, the input is calculated through a reconstruction algorithm so as to reconstruct the reflection spectrum of the surface plasma resonance, and then the purpose of sensing detection is achieved through related theoretical analysis and calculation.

2. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the broadband light source (1) has the function of outputting continuous light in a visible light to near infrared band, the adjustable parameters of the broadband light source (1) can be any one of the angle of emitted light, the wavelength of the emitted light and the intensity of the emitted light, and the type of the broadband light source can be any one of a halogen tungsten lamp, a xenon lamp, an iodine lamp and a hydrogen lamp.

3. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the prism (4) is used as an optical coupling device and is made of a non-absorptive optical material with a high refractive index, and the prism (4) is in direct contact with the metal film (3).

4. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the material of the metal film (3) can be any one of gold, silver, copper and aluminum, the thickness of the metal film (3) is generally dozens of nanometers, the substance placed on the metal film (3) is a sample to be detected in the sample cell (2), and the metal film (3) is placed on the prism (4).

5. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the surface plasma resonance sensor of the system adopts a Kretchsmann structure consisting of a prism (4), a metal film (3) and an object to be detected, light emitted by a broadband light source (1) forms p-polarized light through a polaroid (10) and enters the prism (4) at a certain angle, the reflection and refraction occur at the interface of the prism (4) and the metal film, and by adjusting the wavelength or the incident angle of the light emitted by the broadband light source (1), so as to achieve a certain condition to enable the surface plasma wave and the incident light to generate the surface plasma resonance phenomenon, the reflected light enters the photoelectric detector (6) through the focusing lens (5), the resonance angle or the resonance wavelength of the surface plasma resonance is closely related to the property of the object to be measured on the surface of the metal film, information on the substance to be measured can be obtained by measuring the resonance angle or the resonance wavelength, and the detection method of the surface plasmon resonance sensor may be either an angle modulation type or a wavelength modulation type.

6. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the photoelectric detector (6) is used for detecting incident light, the photoelectric detector (6) can generate corresponding photocurrent under the irradiation of the incident light, signals are input into the main control system (8) through the photoelectric signal processing circuit (9), and the type of the photoelectric detector (6) can be any one of a PN junction type photodiode, a PIN junction type photodiode, an avalanche type photodiode or a single photon avalanche photodiode.

7. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the photoelectric signal processing circuit (9) is used for processing signals generated by the photoelectric detector (6) and inputting the signals into the main control system (8), and the photoelectric signal processing circuit (9) can be a circuit consisting of a transimpedance amplifier (TIA) and an analog-digital conversion circuit or a photon counting circuit.

8. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the bias voltage circuit (7) provides fixed bias voltage for the main control system (8) to enable the main control system to work normally, the bias voltage provided by the bias voltage circuit (7) for the photoelectric detector (6) is controlled by the main control system (8), spectral responses of the detector are different under the condition of different bias voltages, the photoelectric detector (6) can obtain a plurality of groups of effective data output from the photoelectric signal processing circuit (9) in a mode of combining different bias voltages, and the bias voltage circuit (7) has the function of converting input voltage (direct current or alternating current) into direct current voltage required by the work of the photoelectric detector (6).

9. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the main control system (8) stores spectral response function information of the photoelectric detector (6), the main control system (8) normalizes an input photocurrent value, parameters of the spectral response function comprise bias voltage, normalized current value and wavelength of the detector, the input of the main control system (8) comprises a spectral response function obtained through pre-testing and a signal output from the photoelectric signal processing circuit (9), the main control system (8) is used for correlating a plurality of groups of data obtained from the photoelectric signal processing circuit (9) with the spectral response function and carrying out calculation processing on the input through a reconstruction algorithm so as to reconstruct the spectral information, and the main control system (8) can obtain a fitting relation curve of a resonance angle or a resonance wavelength and certain properties of an object to be detected so as to detect related parameters of the object to be detected.

10. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: method for measuring the spectral response function of a photodetector (6): the bias voltage of the photoelectric detector (6) is fixed firstly, the adjustable light source can control the wavelength and the intensity of the emitted light, the light intensity of the emitted light of the adjustable light source is set to be fixed and unchanged, monochromatic light with fixed wavelength is emitted by the light source to irradiate the photoelectric detector (6), the system stores the tested photocurrent information into the main control system (8), then the wavelength of incident light is gradually changed within the detectable wavelength range of the system according to a certain step length, the photocurrent information generated by the detector is sequentially and continuously stored into the main control system (8), then the bias voltage of the detector is changed, the steps are repeatedly carried out, the photocurrent under the condition of different wavelengths is measured, and the bias voltage is also changed according to a certain step length.

11. The highly integrated surface plasmon resonance sensor system of claim 1, wherein: the micro spectrometer based on the spectrum reconstruction technology is composed of a photoelectric detector (6), a bias voltage circuit (7), a main control system (8) and a photoelectric signal processing circuit (9), wherein one purpose of the main control system (8) is to solve unknown quantity F (lambda) which represents spectral information of incident light and has parameters of light intensity and wavelength and known quantity R_j(λ) represents the photo-detector (6) at bias voltage V_jSpectral response function of time, F (lambda) R_j(λ) represents a bias voltage V_jAnd photocurrent I generated by the detector under the irradiation of incident light with wavelength lambda_jThe detectable wavelength range of the system is from λ_minTo lambda_maxThe incident light source contains light with different wavelengths and each monochromatic light with different wavelength in the detection range can generate photocurrent in the detector, so that the detector is biased at V_jPhotocurrent I generated during the time_jFor F (lambda) R in the wavelength range_j(lambda), i.e. the photocurrent generated by the detector is superimposed by light of each wavelength, and if the bias voltage adjusted by the photodetector (6) is m, m equations representing the photocurrent of the detector are listed as a set of equations, the variables of which include I_j、R_j(λ) and an unknown quantity F (λ); the main control system (8) obtains the photocurrent I through testing_jAnd a spectral response function R_jAnd (lambda) forming a linear equation system by the m equations, and finally solving F (lambda) by calculation processing to reconstruct the spectral information of the incident light.

(II) background of the invention

At present, most of detection instruments based on the surface plasma resonance technology at home and abroad have the defects of complex structure, large volume and high cost, so that the application of the detection instruments in the aspects of real-time analysis, field detection and the like is limited, and the miniaturization becomes a main direction for the development of the detection and analysis instruments; the surface plasmon resonance detection system needs to adopt a spectrometer with high resolution to improve the detection capability of the system, but the traditional high-performance spectrometer has larger size and high price, the miniaturization of the spectrometer is limited by factors such as the size of an optical element, the length of an optical path and the like, and the reduction of the size of the spectrometer brings corresponding performance reduction.

In recent years, spectrometers based on a spectrum reconstruction technology appear, and equipment utilizes algorithm processing and combines a machine learning technology; the technology can compensate the influence on the equipment performance caused by further miniaturization, which represents a way for realizing an ultra-compact high-performance spectrometer, and the spectrometer not only can utilize the technical progress of hardware, but also can utilize a new algorithm for processing, and can be widely applied to industrial and consumer electronic platforms.

In order to realize a detection system based on a surface plasmon resonance sensor with high performance, Wen-Kai Kuo et al uses a tunable band-pass filter (TTBF) as an absorption spectrum shift detector of the surface plasmon resonance sensor, and adjusts the central wavelength of the pass band of the TTBF by changing the incident angle, and this method can perform high-resolution sensing on the refractive index of the surface plasmon resonance sensor without using a high-performance spectrometer (Wen-Kai Kuo, et al, "Thin-film tunable bandpass filter for spectral shift detection in surface plasmon resonance sensors" OSA, 2019); shaoyonghong et al disclosed in 2012 "a detection system and a detection method based on surface plasmon resonance" (Chinese patent: CN201210406085.4), the system combines a spectral scanning technique and an angle detection technique, adopts a spectral filter on an array detector, and realizes small-angle high-precision continuous scanning by changing the surface plasmon resonance position through a spectrum; lotfiani et al proposed a new architecture of surface plasmon resonance sensors with electrical response, in which an Integrated thermionic Photodetector replaces the traditional spectrometer, the open circuit voltage of the metal-insulator-metal MIM junction is proportional to the refractive index of the analyte, and the electrical sensitivity is improved by introducing indium tin oxide as a blocking layer for the thermionic electrons above the electrodes (a. lotfiani, et al, "Miniaturized electronic SPR Sensor base on Integrated Planar Waveguide and MIM Hot-Electron photon spectrometer" IEEE, 2019); duo Yi et al propose a hybrid fiber sensor based on surface plasmon resonance and multimode interference (MMI), the surface plasmon resonance effect and MMI effect being excited simultaneously in a single sensor, the surface plasmon resonance signal and interference signal being separated using fast fourier transform and filtering algorithms, the hybrid sensor improving RI sensitivity (Duo Yi, et al, "interference detection arrays of a hybrid fiber sensor based on SPR and MMI" OSA 2020); the metal corrugation structure prepared by Chen-Chieh Yu et al is used for an ultra-sensitive plasma sensor, the metal corrugation can sense the surface plasma resonance wavelength and the refractive index matching effect, and the refraction measurement is carried out by measuring the transmission intensity of the substrate, and the system does not need a spectrometer (Chen-Chieh Yu, et al, the IEEE (2012).

The above invention has the following drawbacks and disadvantages: 1. the tunable optical filter is used as an absorption spectrum shift detector of the surface plasma resonance sensor, and an optical element needs to be manufactured separately, so that the manufacturing difficulty and cost of the system are increased, the absorption efficiency and sensitivity of the detector are reduced, and the size of the system is increased; 2. the method of combining the spectrum scanning and the angle detection technology not only needs to adopt a spectrum filter, increases the manufacturing difficulty of the system and reduces the sensitivity of the detector, but also needs to continuously control an array light source to obtain complete spectrum information, so that the real-time performance is poor, and a spectrometer with larger size needs to be adopted to obtain high performance; 3. although the system size can be reduced by simply adopting a method of replacing a spectrometer by a thermionic photoelectric detector, the system has lower spectral resolution, the manufacturing difficulty and cost are increased by adopting a method of introducing indium tin oxide, and the manufacturing cost is high; 4. the adoption of a mixed sensing mode of surface plasma resonance and multi-mode interference (MMI) can increase the manufacturing difficulty and cost of the system, and a complex algorithm is also needed to distinguish a surface plasma resonance signal and an interference signal, so that the design is complex, and the size of the system is larger by adopting a traditional spectrometer; 5. the method of the metal corrugated structure sensor is difficult to manufacture the metal corrugated structure, and the matching effect of the surface plasma resonance wavelength and the refractive index is high in requirement condition and complex in design.

In order to solve the problems, the invention discloses a high-integration surface plasma resonance sensor system which adopts a spectrum reconstruction technology to manufacture a spectrometer, a large number of different spectral response conditions can be obtained by combining different bias voltage through a single detector, a spectrometer can obtain a spectral response function with high sampling resolution, the bias voltage condition is adjusted to obtain a large number of effective data, spectral reconstruction is carried out through a reconstruction algorithm, an optical element is not required to be manufactured independently by the spectrometer, the detector is simple in design, and the requirement on the manufacturing process is not high, so that the spectrometer has the advantages of high resolution, low cost and microminiaturity, the problem that the miniaturization and the high performance of a detection system based on the surface plasma resonance technology are mutually contradictory is solved, the system meets the detection requirements of high sensitivity, on-site online and low cost, and the high-performance miniaturized detection system based on the surface plasma resonance sensor can be realized.

Incident light impinging on a semiconductor material is absorbed at a certain depth and generates electron-hole pairs, and the rate G of the generation of the electron-hole pairs at the surface of the PN junction upon which the incident light impinges depends on the incident light flux M, the wavelength λ of the incident light, the light absorption coefficient α of the material, and the distance y from the silicon surface, as shown in equation (1):

G(y)＝Mα(λ)exp-(α(λ)y) (1)

the penetration depth has a strong wavelength dependence, light with shorter wavelengths is absorbed near the surface, while light with longer wavelengths penetrates deeper into the semiconductor material until it is absorbed; due to the generation of electron-hole pairs, light irradiation to the PN junction generates a photocurrent, and the photocurrent caused by the light irradiation is shown in formula (2):

I_L＝-qAG(y)×(Ln+Xd+Lp) (2)

wherein A is the junction area of the PN junction, Xd is the barrier width, Lp and Ln are the hole and electron diffusion lengths respectively, and the photo-generated current of the photodetector depends on the incident light and the structural property of the PN junction; under the condition of no radiation effect, the characteristics of the photoelectric detector are the same as those of a common photoelectric diode, and the current equation of the external bias voltage is shown as the formula (3):

I₀for reverse saturation current, KT is the hot press equivalent and the value at room temperature is 26mev; when the photodetector is externally biased within a certain reverse voltage range, the generated current is extremely small and basically constant, the current is called dark current, the light generation current is much larger than the dark current, so the dark current is generally negligible, the reverse current flowing through the photodiode under light is generally called photocurrent of the photodiode, and as can be seen from the above equations (2) and (3), the current generated by the light radiation applied to the photodiode when the external bias voltage is V is shown as equation (4):

the spectral responsivity refers to the response capability of the photoelectric detector to monochromatic light, and a spectral response curve when the bias voltage is V can be obtained through a formula (4); potential barrier width X of PN junction_dThe formula is shown in (5) in relation to the external bias voltage V of the semiconductor:

N₀to reduce the concentration,. epsilon_sIs dielectric constant, V_biFor the built-in potential, it can be known through formulas (4) and (5) that the external bias voltage can affect the photocurrent generated by the photodetector and change the photocurrent represented by formulas (3) and (2), the external bias voltage mainly changes the photocurrent generated by illumination, and as the absolute value of the external negative voltage increases, the current generated by the photodetector correspondingly increases, i.e. the spectral responsivity increases; the monotonic relation between the spectral responsivity and the bias voltage is not simply in direct proportion, namely the spectral responsivity of the photoelectric detector under different bias voltages has specificity; the voltage is increased when the absolute value of the reverse bias voltage is small, the spectral responsivity change of the photoelectric detector is large, the voltage is increased when the absolute value of the reverse bias voltage is large, the spectral responsivity change of the photoelectric detector is small (tends to be saturated), and therefore the detector can have different spectral responsivities by adopting different bias voltages.

By measuring at a fixed position under the irradiation of incident light of a fixed wavelengthThe photocurrent generated by the photodetector under a fixed bias voltage is used for obtaining a spectral response function of the detector under a certain fixed bias voltage, the photocurrent needs to be normalized (the photocurrent value is compared with the incident light intensity value), and the external bias voltage value of the detector is V_jThe spectral response of R_j(λ)。

F (lambda) represents the spectral information of the incident light, and the parameters are light intensity and wavelength, and the incident light F (lambda) irradiates the photoelectric detector to detect, and the detector is biased at an external bias voltage V_jPhotocurrent I obtained by time measurement_jCan be expressed by equation (6):

bias voltage value V_jThe light intensity of incident light with wavelength of lambda is represented by F (lambda), under the working condition of lower than breakdown voltage, the photocurrent formed by the detector is in direct proportion to the light intensity, and the normalized current value of the spectral response function represents the proportionality coefficient of the photocurrent to the light intensity, so that F (lambda) R is obtained_j(λ) represents a bias voltage V_jAnd a photocurrent generated by the detector upon illumination by incident light having a wavelength λ, the wavelength range detectable by the spectrometer being from λ_minTo lambda_maxSo that the detector is biased at V_jPhotocurrent I generated in the case of (1)_jIs to F (lambda) R in the whole wavelength range_j(λ), equation (6) can also be written in discrete form, as expressed in equation (7):

I＝R×F (7)

wherein R represents the spectral response function matrix of the detector, and I is the photocurrent data matrix obtained by the test, so that the unknown target spectrum F can be reconstructed by solving equation (7), i.e. the reflection spectrum of the surface plasmon resonance is obtained.

The surface plasma resonance is a physical optical phenomenon generated on an interface of a metal film and a dielectric medium, p-polarized components of evanescent waves generated when light is totally reflected at the interface enter the metal film to interact with the metal film, excited surface plasma waves propagate along the surface of the metal film, the surface plasma resonance phenomenon can be generated under certain conditions, the energy of incident light can be converted into the energy of SPW, the energy of reflected light is reduced, a resonance absorption peak appears in a reflection spectrum, and the angle or wavelength of the incident light is called as the resonance angle or the resonance wavelength of the surface plasma resonance.

The Kretschmann prism structure is the most widely applied type of surface plasma resonance sensor, the Kretschmann structure comprises three mediums of a prism, metal and a sample, the Kretschmann prism structure covers a metal film with the thickness of dozens of nanometers, a substance to be detected is placed on the metal film, and the surface plasma resonance is excited by adjusting the incident angle or wavelength of incident light.

When light waves enter the interface of two media with different refractive indexes, light is reflected and refracted, an incident light electric vector in the direction vertical to the propagation direction can be decomposed into S polarized light (polarized light vertical to the incident surface) and P polarized light (polarized light parallel to the incident surface), and because the electric field of the S polarized light is parallel to the interface, electron movement is free from obstruction, surface plasma waves can not be excited, and the electric field of the P polarized light is vertical to the interface, so that the surface plasma resonance phenomenon can be generated under certain conditions.

When the P polarized light enters the interface of the prism and the metal film, the refractive index of the prism is larger than that of the metal film, and if the incident angle is larger than the critical angle, total reflection occurs; because the thickness of the metal film is dozens of nanometers and is smaller than the penetration depth of the evanescent wave, the evanescent wave exists at the interface of the metal film and the substance to be detected, and the evanescent wave has a wave vector component k in the direction parallel to the interface of the metal and the substance to be detected_xAs shown in equation (8):

where c is the speed of light, w is the angular frequency of the P-polarized light,ε₀is the dielectric constant of the prism, theta₀Is the angle of incidence of P-polarized light; under the incidence of P polarized light, a surface plasma wave is formed at the interface of the metal film and the substance to be measured, and the wave vector k of the surface plasma wave_spAs shown in formula (9):

wherein epsilon₁Is the dielectric constant, ε, of a metal film₂Is the dielectric constant of the substance to be measured; by varying the angle of incidence theta of P-polarized light₀And a wavelength λ such that k_x＝k_spUnder such conditions, the plasmon wave and evanescent wave on the metal surface are coupled to generate a surface plasmon resonance phenomenon, the reflected light intensity reaches a minimum value, the angle or wavelength of the incident light at this time is called as the resonance angle or resonance wavelength of the surface plasmon resonance, and the condition of the surface plasmon resonance is as shown in formula (10):

the resonance angle or the resonance wavelength of the surface plasma resonance is closely related to the property of an object to be detected on the surface of the metal film, the surface plasma resonance sensor is very sensitive to the refractive index of a medium attached to the surface of the metal film, when the object to be detected (generally, solution) is attached to the surface of the metal film, the refractive index of the surface of the metal film is changed, so that the resonance angle or the resonance wavelength of the surface plasma resonance is changed, the absorption spectrum of the surface plasma resonance is changed, a relation curve of the resonance wavelength or the resonance angle and the reflectivity can be obtained through experiments, and the information such as the concentration of the object to be detected is obtained through calculation and analysis according to related theories, so that the purpose of detection is.

Disclosure of the invention

The invention aims to provide a high-integration surface plasma resonance sensor system, and belongs to the technical field of photoelectric detection.

The high-integration surface plasma resonance sensor system consists of a broadband light source (1), a sample cell (2), a metal film (3), a prism (4), a focusing lens (5), a photoelectric detector (6), a bias voltage circuit (7), a main control system (8), a photoelectric signal processing circuit (9) and a polaroid (10); when the system works, a sample is introduced into the sample cell (2), light emitted from the broadband light source (1) is adjusted into P polarized light through the polaroid (10), light beams are incident on the metal film (3) through the prism (4), and surface plasma waves are generated on the interface of the metal film (3) and an object to be measured; the system adjusts the wavelength or the incident angle of light emitted by the broadband light source (1), so that the surface plasma wave and the incident light generate a surface plasma resonance phenomenon under a certain condition; light beams reflected from the metal film (3) enter the photoelectric detector (6) through the prism (4) and the focusing lens, signals generated by the photoelectric detector (6) are input to the main control system (8) through the photoelectric signal processing circuit (9), the bias voltage circuit (7) provides fixed voltage for the main control system (8) so as to enable the main control system to work normally, bias voltage provided by the bias voltage circuit (7) for the photoelectric detector (6) is controlled by the main control system (8), and spectral response functions of the photoelectric detector (6) under different bias voltages are tested in advance and are obtained and stored in the main control system (8); the main control system (8) takes the signals and the spectral response function obtained from the photoelectric signal processing circuit (9) as input, the input is calculated through a reconstruction algorithm so as to reconstruct the reflection spectrum of the surface plasma resonance, and then the purpose of sensing detection is achieved through related theoretical analysis and calculation.

The broadband light source (1) has the function of outputting continuous light in the visible light to near infrared bands, the adjustable parameters of the broadband light source (1) can be any one of the angle of emitted light, the wavelength of the emitted light and the intensity of the emitted light, and the type of the broadband light source can be any one of a halogen tungsten lamp, a xenon lamp, an iodine lamp and a hydrogen lamp.

The prism (4) functions as an optical coupling device, the prism is made of a non-absorptive optical material with a high refractive index, and the prism (4) is in direct contact with the metal film (3).

The material of the metal film (3) can be any one of gold, silver, copper and aluminum, the thickness of the metal film (3) is generally dozens of nanometers, the substance placed on the metal film (3) is a sample to be detected in the sample cell (2), and the metal film (3) is placed on the prism (4).

The surface plasma resonance sensor adopts a Kretchsmann structure consisting of a prism (4), a metal film (3) and an object to be detected, light emitted by a broadband light source (1) forms p-polarized light through a polaroid (10) and is incident into the prism (4) at a certain angle, the reflection and refraction occur at the interface of the prism (4) and the metal film, and by adjusting the wavelength or the incident angle of the light emitted by the broadband light source (1), so as to achieve a certain condition to enable the surface plasma wave and the incident light to generate the surface plasma resonance phenomenon, the reflected light enters the photoelectric detector (6) through the focusing lens (5), the resonance angle or the resonance wavelength of the surface plasma resonance is closely related to the property of the object to be measured on the surface of the metal film, information on the substance to be measured can be obtained by measuring the resonance angle or the resonance wavelength, and the detection method of the surface plasmon resonance sensor may be either an angle modulation type or a wavelength modulation type.

The photoelectric signal processing circuit (9) is used for processing the signal generated by the photoelectric detector (6) and inputting the processed signal into the main control system (8), and the photoelectric signal processing circuit (9) can be a circuit consisting of a trans-impedance amplifier (TIA) and an analog-digital conversion circuit or a photon counting circuit.

The photoelectric signal processing circuit (9) is used for processing the signal generated by the photoelectric detector (6) and inputting the processed signal into the main control system (8), and the photoelectric signal processing circuit (9) can be a circuit consisting of a trans-impedance amplifier (TIA) and an analog-digital conversion circuit or a photon counting circuit.

The bias voltage circuit (7) provides fixed bias voltage for the main control system (8) to enable the main control system to work normally, the bias voltage provided by the bias voltage circuit (7) for the photoelectric detector (6) is controlled by the main control system (8), the spectral responses of the detector are different under the condition of different bias voltages, the photoelectric detector (6) can obtain a plurality of groups of effective data output from the photoelectric signal processing circuit (9) in a mode of combining different bias voltages, and the bias voltage circuit (7) has the function of converting input voltage (direct current or alternating current) into direct current voltage required by the work of the photoelectric detector (6).

The main control system (8) stores spectral response function information of the photoelectric detector (6), the main control system (8) normalizes an input photocurrent value, parameters of the spectral response function comprise bias voltage, normalized current value and wavelength of the detector, the input of the main control system (8) comprises a spectral response function obtained through pre-testing and a signal output from the photoelectric signal processing circuit (9), the main control system (8) is used for correlating a plurality of groups of data obtained from the photoelectric signal processing circuit (9) with the spectral response function and carrying out calculation processing on the input through a reconstruction algorithm so as to reconstruct the spectral information, and the main control system (8) can obtain a fitting relation curve of a resonance angle or a resonance wavelength and certain properties of an object to be detected so as to detect related parameters of the object to be detected.

Method for measuring the spectral response function of a photodetector (6): the bias voltage of the photoelectric detector (6) is fixed firstly, the adjustable light source can control the wavelength and the intensity of the emitted light, the light intensity of the emitted light of the adjustable light source is set to be fixed and unchanged, monochromatic light with fixed wavelength is emitted by the light source to irradiate the photoelectric detector (6), the system stores the tested photocurrent information into the main control system (8), then the wavelength of incident light is gradually changed within the detectable wavelength range of the system according to a certain step length, the photocurrent information generated by the detector is sequentially and continuously stored into the main control system (8), then the bias voltage of the detector is changed, the steps are repeatedly carried out, the photocurrent under the condition of different wavelengths is measured, and the bias voltage is also changed according to a certain step length.

The micro spectrometer based on the spectrum reconstruction technology is composed of a photoelectric detector (6), a bias voltage circuit (7), a master control system (8) and a photoelectric signal processing circuit (9), wherein one purpose of the master control system (8) is to solve unknown quantity F (lambda) which represents spectral information of incident light and has parameters of light intensity and wavelength and known quantity R_j(λ) represents the photo-detector (6) at bias voltage V_jSpectral response function of time, F (lambda) R_j(λ) represents a bias voltage V_jAnd photocurrent I generated by the detector under the irradiation of incident light with wavelength lambda_jThe detectable wavelength range of the system is from λ_minTo lambda_maxThe incident light source contains light of different wavelengths and each has a different wavelength in the detection rangeThe monochromatic light can generate photocurrent at the detector, so that the detector is biased at V_jPhotocurrent I generated during the time_jFor F (lambda) R in the wavelength range_j(lambda), i.e. the photocurrent generated by the detector is superimposed by light of each wavelength, and if the bias voltage adjusted by the photodetector (6) is m, m equations representing the photocurrent of the detector are listed as a set of equations, the variables of which include I_j、R_j(λ) and an unknown quantity F (λ); the main control system (8) obtains the photocurrent I through testing_jAnd a spectral response function R_jAnd (lambda) forming a linear equation system by the m equations, and finally solving F (lambda) by calculation processing to reconstruct the spectral information of the incident light.

Compared with the prior art, the invention has the advantages that: the invention adopts the micro spectrometer based on the spectrum reconstruction technology, avoids the problems that the traditional spectrometer (such as an optical fiber spectrometer) is limited by factors such as optical components, optical path length and the like to be miniaturized and bring performance reduction, can obtain a large number of different spectrum response conditions by combining a single detector with different bias voltages so as to obtain a spectrum response function with high sampling resolution, and obtains a spectrum by calculating and processing the system through a reconstruction algorithm, so the spectrum reconstruction type spectrometer has the advantages of high resolution and microminiature, solves the problem that the miniaturization and high performance of a detection system based on a surface plasma resonance sensor are mutually contradictory, and can realize a high-performance portable detection system based on the surface plasma resonance sensor.

(IV) description of the drawings

Fig. 1 is a schematic diagram of a high-integration surface plasmon resonance sensor system, which is composed of a broadband light source (1), a sample cell (2), a metal film (3), a prism (4), a focusing lens (5), a photoelectric detector (6), a bias voltage circuit (7), a main control system (8), a photoelectric signal processing circuit (9) and a polarizing plate (10).

Fig. 2 is a schematic diagram of an embodiment of a system for detecting the concentration of a glucose solution based on a surface plasmon resonance sensor combined with a spectral reconstruction technique, and the system comprises a halogen tungsten lamp light source (1), a sample cell (2), a gold film (3), a prism (4), a focusing lens (5), a PN junction type photodiode (6), a bias voltage circuit (7), a main control system (8), a photoelectric signal processing circuit (9) and a polarizer (10).

(V) detailed description of the preferred embodiments

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described below in conjunction with the drawings in the embodiments of the present invention.

Fig. 2 shows an embodiment of a system for detecting the concentration of glucose solution based on a surface plasmon resonance sensor in combination with a spectrum reconstruction technique, which comprises a tungsten halogen lamp light source (1), a sample cell (2), a gold film (3), a prism (4), a focusing lens (5), a PN junction photodiode (6), a bias voltage circuit (7), a main control system (8), a photoelectric signal processing circuit (9), and a polarizer (10).

The detection mode of the surface plasma resonance sensor is a wavelength modulation type, an incident angle is fixed in an experiment to change incident wavelength parameters, a halogen tungsten lamp light source (360nm-2000nm) is used as a broadband light source, a metal thin film is made of gold materials, the metal thin film is stable in performance and not easy to oxidize and pollute, the thickness of the gold film (3) is 50nm, a detection system does not perform any chemical or biological modification on the gold film (3), a molecular sensitive film is not manufactured, and a substance to be detected is in direct contact with the surface of the gold film.

The method comprises the steps of adopting prepared glucose solutions with different concentrations as experiment samples, preparing glucose solutions with concentrations of 4%, 8%, 12%, 16%, 20%, 24% and 28%, wherein the refractive indexes corresponding to the glucose solutions with the concentrations from small to large are R1, R2, R3, R4, R5, R6 and R7 respectively, and the refractive indexes are increased along with the increase of the concentration of the glucose solution.

Firstly, glucose solutions of different concentrations are repeatedly measured by the same sensor device, and the glucose solutions are fed into the sample cell (2)Light emitted from a halogen tungsten lamp light source (1) is adjusted into P polarized light through a polarizing film (10), light beams are incident on a gold film (3) through refraction of a prism (4), surface plasma waves are generated on the gold film (3) and a glucose solution surface, light reflected from the prism (4) is incident on a PN junction type photodiode (6) through a focusing lens, signals generated by the PN junction type photodiode (6) are input to a main control system (8) through a photoelectric signal processing circuit (9), a bias voltage circuit (7) provides fixed bias voltage for the main control system (8), the bias voltage provided by the bias voltage circuit (7) for the PN junction type photodiode (6) is controlled by the main control system (8), and spectral response functions R of the PN junction type photodiode (6) under different bias voltages are controlled by the main control system (8)_j(lambda) is tested in advance and stored in a master control system (8), and the master control system (8) obtains a signal and a spectral response function R from the photoelectric signal processing circuit (9)_j(lambda) is used as an input, the spectral information is reconstructed by calculating the input through a reconstruction algorithm, the main control system (8) obtains a surface plasma resonance reflection spectrum, and then the relation between the resonance wavelength and the concentration of the glucose solution is obtained through repeated experiments and combined with a relevant theory and calculation analysis, so that the system can detect the concentration of the glucose solution according to the obtained resonance reflection spectrum.

The micro spectrometer based on the spectrum reconstruction technology is composed of a PN junction type photodiode (6), a bias voltage circuit (7), a main control system (8) and a photoelectric signal processing circuit (9), and a method for analyzing the micro spectrometer to obtain a resonance spectrum through the spectrum reconstruction technology is used below.

F (λ) represents spectral information of incident light, R_j(lambda) represents a PN junction type photodiode (6) biased at V_jSpectral response function of time, R_j(λ) the information expressed is that the detector has a wavelength of light λ and a bias voltage V_jTime-normalized current value, at bias voltage of V_jPhotocurrent I generated by time detector_jCan be expressed as F (lambda) R over a range of wavelengths_j(λ) i.e. the light of each wavelength in the incident light is superimposed on the photocurrent generated by the detector.

At a bias voltage of V_jIn the case of (1), R_j(lambda) the wavelength value to be collected is lambda₁、λ₂、...、λ_kAnd corresponding normalized current valuesWherein λ_min≤λ₁＜λ₂＜…＜λ_k≤λ_maxThe sampling frequency of the main control system (8) under each bias voltage is k, and the bias voltage set in the embodiment is V₁、V₂、V₃、V₄、V₅、V₆、V₇、V₈、V₉、V₁₀The system adjusts the bias voltage of the PN junction type photodiode (6) through a bias voltage circuit (7) to obtain a digital signal I of photocurrent_j(where j 1, 2.., 10), these signals are input to a master control system (14) and are additionally biased at a bias voltage V_jThe spectral response function of time is R_j(λ), a calculation processing formula obtained by integrating the data is as follows:

F(λ₁)R₁(λ₁)+F(λ₂)R₁(λ₂)+…+F(λ_k)R₁(λ_k)＝I₁

F(λ₁)R₂(λ₁)+F(λ₂)R₂(λ₂)+…+F(λ_k)R₂(λ_k)＝I₂

F(λ₁)R₃(λ₁)+F(λ₂)R₃(λ₂)+…+F(λ_k)R₃(λ_k)＝I₃

F(λ₁)R₄(λ₁)+F(λ₂)R₄(λ₂)+…+F(λ_k)R₄(λ_k)＝I₄

F(λ₁)R₅(λ₁)+F(λ₂)R₅(λ₂)+…+F(λ_k)R₅(λ_k)＝I₅

F(λ₁)R₆(λ₁)+F(λ₂)R₆(λ₂)+…+F(λ_k)R₆(λ_k)＝I₆

F(λ₁)R₇(λ₁)+F(λ₂)R₇(λ₂)+…+F(λ_k)R₇(λ_k)＝I₇

F(λ₁)R₈(λ₁)+F(λ₂)R₈(λ₂)+…+F(λ_k)R₈(λ_k)＝I₈

F(λ₁)R₉(λ₁)+F(λ₂)R₉(λ₂)+…+F(λ_k)R₉(λ_k)＝I₉

F(λ₁)R₁₀(λ₁)+F(λ₂)R₁₀(λ₂)+…+F(λ_k)R₁₀(λ_k)＝I₁₀

the above calculation processing formula can be expressed by a matrix, and the expression is as follows:

I＝R×F

where R is a 10 × K matrix representing the spectral response function, I is a 10 × 1 matrix representing the photocurrent information, and F is a K × 1 matrix representing the light source spectral information, where I and R are known quantity matrices and F is an unknown quantity.

The method is characterized in that the R matrix is required to be equal to the amplification matrix (R, I) in order to solve the linear equation set, the unique solution or the infinite solution exists, the R matrix is required to be equal to the amplification matrix (R, I) in order to enable the equation to exist the unique solution, the rank of the R matrix is required to be equal to the unknown number K, and therefore the value of the K is required to be selected according to the number of system detectors and the actual situation of bias voltage setting.

By making the system of linear equations have a unique solution through reasonable arrangement, the solution of the F matrix can be expressed as:

F＝R^-1×I

R^-1is an inverse matrix of R, which exists if the determinant of the matrix is not zero, and the row vectors of the R matrix are not linearly related due to the difference of spectral response functions between different detectors, i.e. the determinant of the R matrix is not zero, so R exists.

The linear system of equations is uniquely solved by selecting an appropriate value of k, the master control system (14) takes the photocurrent signal and the spectral response function as inputs, knowing the R matrix and the I matrix, and solves the inverse matrix R^-1The inverse matrix is multiplied by the matrix I to obtain an unknown matrix F, and a linear equation set consisting of 10 equations is obtained through calculation processing to obtain an unknown quantity F (lambda), namely, the reflection spectrum of the surface plasmon resonance is reconstructed.

The glucose solution with different concentrations needs to be repeatedly measured for two to three times, data is obtained by adopting a method of measuring for many times and taking an average value, reflection spectrums of surface plasmon resonance of the glucose solutions with different concentrations are obtained through measurement, and the refractive indexes of the glucose solutions with different concentrations are known in advance.

After the reflection spectrum is obtained, experimental data is required to be processed, firstly, the spectrum is smoothed and denoised through a main control system (8), because factors such as noise can bring large errors to a reflection spectral band causing surface plasma resonance, the spectrum is smoothed and denoised by adopting a Savitzky-Golay filtering method, the filtering method is a filtering method based on polynomial least square fitting in a time domain, and the maximum characteristic is that the shape and the width of a signal can be ensured to be unchanged while noise is filtered, and distribution characteristics such as a maximum value, a minimum value and a width can be reserved.

The procedure of Savitzky-Golay filtering is described below, assuming that the spectrum is divided into 2m +1 sample points, which constitute a single row of (2m +1) columns of the matrix X ═ X_-m,x_-m+1,…,x_-1,x₀,x₁,…,x_m-1,x_m) The data values represented by the sampling points represent wavelength values, and the data are fitted using a polynomial of degree K-1 as follows:

Y＝a₀+a₁X+a₂X²+…+a_k-1X^k-1

the equation constitutes (2m +1) linear equation sets, in order to make the equation set have solutions, it needs to satisfy (2m +1) > K, and the fitting parameter A is determined by least square fitting, and the equation is expressed as follows:

where e represents the error, the above equation can be expressed in matrix form as:

Y_(2m+1)×1＝X_(2m+1)×K·A_K×1+E_(2m+1)×1

the A matrix represents the coefficient values of the unknowns, where the least squares solution of ARepresented by the following formula:

the predicted value or the filtered value of the model of Y is solved by a Savitzky-Golay filtering algorithm and is expressed as the following formula:

and then calculating the position of a formant, wherein the position of the formant of the reflection spectrum needs to be calculated after noise is removed, a polynomial fitting method is adopted in an algorithm for calculating the position of the formant of surface plasma resonance, the position of the lowest point of the reflection spectrum is firstly found out, then, a plurality of points near the lowest point are fitted by utilizing polynomial least squares, and the position of the formant in the reflection spectrum is judged by analysis.

The relation between the glucose solution with different concentrations and the resonance peak wavelength is researched, namely the relation between the refractive index of the glucose solution and the resonance peak wavelength is researched, the relation between the refractive index of the glucose solution and the resonance peak wavelength is described by adopting a cubic polynomial fitting curve, and a fitting equation is expressed as the following formula:

y＝ax³+bx²+cx+d

wherein x is the refractive index of the glucose solution, y represents the resonance wavelength, a, b and c represent the coefficients of a fitting equation, d represents the constant term of the fitting equation, and the specific coefficients and constant terms can be obtained by fitting experimental data.

With the increase of the concentration of the glucose solution, namely with the continuous increase of the refractive index of the glucose solution, the resonance wavelength of the surface plasmon resonance is lengthened, and the full width at half maximum is also enlarged, the resonance peak of the surface plasmon resonance is red-shifted due to the increase of the concentration of the glucose, and the relational expression of the concentration of the glucose in the solution and the resonance wavelength is obtained through experiments.

The system obtains the reflection spectrum of surface plasma resonance through a micro spectrometer based on a spectrum reconstruction technology, and then performs experiments by using samples with different concentrations to obtain a relational expression of the resonance wavelength and the concentration of the glucose solution, so that the system can detect the concentration of the glucose solution by detecting the resonance peak position information of the surface plasma resonance reflection spectrum for the glucose solution with unknown concentration and performing calculation analysis according to the relational expression of the resonance wavelength and the concentration of the glucose solution.