CN1715878A - Double light beam detection modulation device based on surface plasma wave sensing - Google Patents

Abstract

The invention discloses a dual-beam detection and modulation device based on surface plasma wave sensing. It has a laser, and the laser is divided into two polarized beams, the first beam and the second beam by optical components, which are incident on the prism. Au film is evaporated on the end surface of the prism, and a biological sensitive film is grown on the Au film. There is a flow cell for the sample to be tested, which generates total reflection on the end face of the prism, and the two beams of reflected light enter the first PD detector and the second PD detector respectively. The invention not only retains the characteristics of surface plasmon resonance (SPR) sensing technology, but also simplifies the angle adjustment mechanism because the double-beam SPR sensor does not require precise scanning incident angles, and avoids test errors caused by movable transmission parts , enhanced operability. Since the light intensity signals of the two beams are detected, a photodiode can be used instead of a spectrometer or an expensive CCD array, which can greatly reduce the complexity and manufacturing cost of the system, and is easy to design as a portable instrument.

Description

Dual-beam detection and modulation device based on surface plasmon wave sensing

technical field

The invention relates to biosensing technology and photoelectric detection technology, in particular to a dual-beam detection and modulation device based on surface plasma wave sensing.

Background technique

Generally, there are four detection and modulation methods for surface plasmon resonance (SPR):

1. Angle modulation Incidence of light with a fixed wavelength λ, change the incident angle θ of the incident light wave, under a certain measured refractive index, according to the equation $\sqrt{{\mathrm{\ϵ}}_{\mathrm{pr}}}\frac{\mathrm{\ω}}{c}\sin \mathrm{\θ}=\sqrt{\frac{{\widetilde{\mathrm{\ϵ}}}_1{\widetilde{\mathrm{\ϵ}}}_2}{{\widetilde{\mathrm{\ϵ}}}_1+{\widetilde{\mathrm{\ϵ}}}_2}}\left(\frac{\mathrm{\ω}}{c}\right),$ An incident angle θ can always be found to satisfy the resonance condition and produce surface plasmon resonance. When the refractive index of the measured sample changes, re-scan the incident angle to find the resonant incident angle, and establish the relationship between the resonant incident angle and the measured sample's refractive index. The detection resolution of the angle modulation method can reach 1×10 ^-7 deg RIU ^-1 (RIU is the refractive index unit).

2. Wavelength modulation is incident at a fixed incident angle θ, changing the wavelength λ of the incident light wave. According to Drude's dispersion model, for a prism-based SPR sensor, different incident light wavelengths correspond to different refractive indices ε _m of the metal and ε _pr of the prism. When the refractive index of the sample to be measured is constant, the wavelength of the incident light is scanned to satisfy the resonance condition, surface plasmon resonance is generated, and the relationship between the resonant incident light wavelength and the refractive index of the sample to be measured is established. The detection resolution of wavelength modulation is basically the same as that of angle modulation, which is more suitable for waveguide or optical fiber surface plasma detection schemes. Usually the incident light often uses a white light source, and the detection device uses a spectrometer or a CCD device.

3. Intensity modulation uses a fixed incident angle θ and a fixed incident wavelength λ to measure the change in light intensity when the refractive index changes, and establish the relationship between the transmitted light intensity and the refractive index. The intensity modulation detection method has a very simple structure and the price of the detection device is very low, but the stability of the system is poor, and it is impossible to distinguish whether the change of the detected light intensity signal is caused by the change of the refractive index or the error of the detection device. The anti-interference performance of the detection system Bad and low detection sensitivity.

4. Phase modulation first scans the incident angle θ to find the surface plasmon resonance incident angle when the refractive index of the sample to be measured is constant. At this time, the incident θ is fixed when the resonance is fixed, and then the resonance phase under this refractive index is measured. When the measured sample When the refractive index changes, the above process is repeated to establish the relationship between the resonance phase and the refractive index, and the refractive index of the sample to be measured can be obtained according to this relationship. Phase modulation is a detection method with great development potential. It has a good signal-to-noise ratio and high detection sensitivity. The disadvantage is that the detection device of the system is complicated, and it is difficult to realize the portability of the surface plasmon resonance sensing instrument.

Angle modulation, wavelength modulation and intensity modulation technologies are very mature, and these technologies have been widely used in surface plasmon resonance (SPR) sensing test instruments and designed monitoring and analysis systems. Although the angle adjustment method has high detection accuracy, it is not convenient for on-site on-line monitoring because the surface plasmon resonance angle modulation method requires a set of high-precision angle adjustment devices. The invention patent is a dual-beam detection and modulation technology based on the surface plasmon wave sensing principle proposed after systematic analysis and experimental research on the detection technology of the surface plasmon resonance sensor. The dual-beam detection modulation principle of the surface plasmon wave sensor is as follows: two fixed incident angles θ ₁ and θ ₂ are used for incident, and the two beams of light waves act on the interface between the metal Au film on the end face of the prism and the measured substance to generate reflection. A photodetector detects the reflected light intensity, establishes the relationship between the reflected light intensity of the two beams and the refractive index of the sample to be measured, and then the value of the refractive index of the sample to be measured can be obtained. The dual-beam detection modulation device does not need to scan the angle during the test, but only needs to adjust the angle of the incident light according to the calculated value before detection. In the double-beam detection system, the photodiode is used instead of the commonly used spectrometer or optical power meter as the reflected light signal detector, thus greatly simplifying the complexity of the system, reducing the manufacturing cost of the system, and meeting the high resolution of the detection system requirements.

Contents of the invention

The purpose of the present invention is to provide a dual-beam detection and modulation device based on surface plasmon wave sensing without reducing the resolution and test accuracy of the sensor.

It has a laser, and the laser is divided into two polarized beams, the first beam and the second beam by optical components, which are incident on the prism. Au film is evaporated on the end surface of the prism, and a biological sensitive film is grown on the Au film. There is a flow cell for the sample to be tested, which generates total reflection on the end face of the prism, and the two beams of reflected light enter the first PD detector and the second PD detector respectively.

The thickness of the Au film is 40-60 nm. The prism is an isosceles triangular prism of K9 glass.

The invention not only retains the characteristics of surface plasmon resonance (SPR) sensing technology, but also simplifies the angle adjustment mechanism because the double-beam SPR sensor does not require precise scanning incident angles, and avoids test errors caused by movable transmission parts , enhanced operability. Since the light intensity signals of the two beams are detected, a photodiode can be used instead of a spectrometer or an expensive CCD array, which can greatly reduce the complexity and manufacturing cost of the system, and is easy to design as a portable instrument.

Description of drawings

The accompanying drawing is a schematic structural diagram of a dual-beam detection and modulation device based on surface plasmon wave sensing. In the figure: laser 1, prism 2, optical component 3, first beam 4, second beam 5, first PD photodetector 6, second Two PD photodetectors 7 , a gold film 8 , a biomass sensitive film 9 , and a flow cell 10 for the sample to be measured.

Detailed ways

As shown in the figure, the dual-beam detection and modulation device based on surface plasmon wave sensing has a laser (laser diode) 1, which is divided into a first beam 4 by optical components (including beam collimator, polarizer and beam splitter) 3 1. The second light beam 5 and two beams of polarized light are incident on the prism 2, and an Au film 8 is evaporated on the end surface of the prism 2, and a biosensitive film 9 is grown on the Au film, and the biosensitive film 9 is provided with a flow cell for the sample to be measured 10. Total reflection occurs at the end face of the prism 2, and the two beams of reflected light enter the first PD detector 6 and the second PD detector 7 respectively. Au film 8 has a thickness of 40 to 60 nm. Prism 2 is an isosceles triangular prism of K9 glass.

Au film 8 of 40-60nm is vapor-deposited on the end face of the prism by magnetron sputtering, and a layer of biomass-sensitive film 9 is grown on the Au film, such as the antibody in immunoassay, etc., and the flow cell 10 containing the sample to be tested is placed in The upper surface of the Au film 8 . The laser 1 generates two beams of light through an optical component 3 including a collimator, a polarizer and a beam splitter, the first beam 4 and the second beam 5, and the two beams are respectively incident on the end face of the prism at an angle near the resonance angle - the interface between the Au film and the sample to be measured, the first PD photodetector 6 and the second PD photodetector 7 obtain the power values p(θ ₁ ) and p(θ ₂ ) of the two beams of reflected light. When the analyzed substance in the sample flow cell 10 is combined with the biosensitive film 9, the refractive index changes, and the power difference Δp=|p(θ ₁ )-p(θ ₂ )| of the two beams of reflected light is calculated at this time, The refractive index changes caused by the sample concentration change correspond to different Δp values respectively, and the relationship between Δp and the refractive index value of the measured sample is established, and the concentration value of the measured sample can be obtained through calibration of the relationship.

Claims (3)

1. double light beam detection modulation device based on surface plasma wave sensing, it is characterized in that, it has laser instrument (1), laser instrument is divided into first light beam (4), second light beam (5) two bundle polarized lights by optical module (3), incide prism (2), evaporation has Au film (8) on prism (2) end face, growth has bio-sensitive film (9) on the Au film, bio-sensitive film (9) is provided with sample flow cell (10), produce total reflection at prism (2) end face, two bundle reflected light enter into a PD detector (6), the 2nd PD detector (7) respectively.

2. a kind of double light beam detection modulation device based on surface plasma wave sensing according to claim 1 is characterized in that the thickness of described Au film (8) is 40～60nm.

3. a kind of double light beam detection modulation device based on surface plasma wave sensing according to claim 1 is characterized in that, described prism (2) is a K9 glass isoceles triangle prism.

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