RU2500993C1 - Spectrometer based on surface plasmon resonance - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: spectrometer comprises the following components serially arranged on one optical axis: a source of light emission with a continuous spectrum, a collimator, a polariser, a cylindrical lens or a cylindrical mirror, a device of disturbed full internal reflection with a reflecting element, a dispersing device, a focusing lens and a light-sensitive photomatrix installed in the lens focus.

EFFECT: possibility to produce a spectrum of surface plasmon resonance in a continuous optical range of wavelengths in real time mode and in increased sensitivity of a device.

6 cl, 6 dwg

Description

The invention relates to the field of optical instrumentation and can be used to create biosensors and biodetectors based on surface plasma resonance and for spectral analysis of a small amount of substance.

Surface plasma resonance is the phenomenon of surface excitation of plasmons by means of light. It occurs on the surface of metals subject to complete internal reflection. The term "surface plasma resonance" in the sense used in the present description refers to an optical phenomenon that allows the analysis of interactions in real time by recording the properties and changes in the properties of the test substance on a matrix consisting of a plate with a metal coating.

There are a number of technical solutions in the form of devices designed to obtain and study the spectrum of surface plasma resonance, for example, according to UK patent No. GB 2197065 A [1] and Korean patent No. KR 100856090 [2]. The disadvantage of the technical solutions presented in these patents is the inability to ensure simultaneous measurements at different wavelengths, which reduces the reliability of the study of the substance due to the insufficiently accurate spectral characteristics of the test substance.

Known technical solution in the form of a device according to German patent No. DE 102007021563 A1, which allows measurements for different wavelengths at a fixed angle [3]. However, measurements at a fixed angle do not allow to unambiguously restore the spectral characteristic of the test substance.

The closest technical solution, taken as a prototype, is a device for obtaining and studying the spectrum of surface plasma resonance described in the description of the patent of the Russian Federation No. 2170913 [4], containing a light source with a continuous spectrum, a collimator, a polarizer, two broken mirrors, a transparent vessel filled with liquid, with a bottom with a translucent metal film, and dispersing elements with photodiode arrays.

The disadvantage of this technical solution is the measurement on a small number of angles equal to the number of faces of the broken mirror, dispersing elements and photodiode arrays. This "does not allow to accurately restore the spectral characteristics of the test substance.

In addition, a common drawback of devices designed to obtain and study the spectrum of surface plasma resonance is that the sensitivity of modern biodetectors based on impaired total internal reflection is actually limited by thermal noise. When pumping fluid along a slide with an active layer, thermal fluctuations inevitably occur. The refractive index of water depends on temperature; therefore, fluctuations in the refractive index of the liquid under study arise and, as a result, fluctuations in the signal from the biodetector.

The technical problem solved in the present invention is to provide a surface plasma resonance spectrum in the continuous optical wavelength range in real time, which eliminates thermal noise and more accurately restores the spectral characteristics of the test substance, and, thus, significantly increase the sensitivity of the biodetector,

The solution of the technical problem is achieved by the fact that the presented spectrometer based on surface plasma resonance contains a continuous-spectrum light source, a collimator, a polarizer, a device for impaired total internal reflection with a reflecting element, a dispersing device and a focusing lens, which differs from the previous ones technical solution in that it additionally contains a photosensitive photomatrix installed in focus about a lens, and between the polarizer and the device of the impaired total internal reflection a cylindrical lens or cylindrical mirror is installed (to ensure light incidence in the required range of angles).

Additional options for the implementation of the spectrometer are possible, in which it is advisable to:

- device impaired total internal reflection is made in the form of a prism or half cylinder;

- the reflective element is made in the form of a dielectric plate with a metal coating;

- the reflective element is mounted on the hypotenuse plane of the prism;

- the reflective element is mounted on the flat surface of the half cylinder.

Thus, the introduction of a cylindrical lens into the design of the spectrometer device, the use of only one dispersing element, and the use of a photocell array instead of a set of photodiode arrays makes it possible to obtain a surface plasma resonance spectrum in the continuous optical wavelength range in real time, which eliminates thermal noise and more accurately restore the spectral characteristics of the test substance, and thus significantly increase the sensitivity l biodetector. The proposed technical solution is a spectrometer for obtaining a spectrum of surface plasma resonance in the continuous wavelength range in real time.

A brief list of drawings.

Figure 1 presents the General scheme of the spectrometer (top view).

Figure 2 presents the General scheme of the spectrometer (side view).

Figure 3 presents a diagram of a device of impaired total internal reflection.

Figure 4 presents a photograph of the installation (example of a specific implementation).

Figure 5 presents the image of the spectrum obtained from photomatrix.

Figure 6 presents a graph of the dependence of light reflection on the angle of incidence at a specific wavelength.

The spectrometer consists of a radiation source 1, a collimator 2, a rectangular diaphragm 3, a polarizer 4, a cylindrical lens 5 (to ensure light incidence in the required range of angles), a device for impaired total internal reflection, made in the form of a prism 6 with a reflective element in the form of a slide with a printed thin metal film 7, a dispersing device in the form of a diffraction grating 8, a focusing lens 9, photomatrix 10.

The spectrometer works as follows:

Light rays from a continuous-spectrum light source 1 pass through a collimator 2 with a rectangular diaphragm 3 and a polarizer 4. At the output of the collimator 2, the generated beam of light rays has a rectangular cross section of uniform intensity. After passing through the polarizer 4, the light rays become p-polarized, which is a prerequisite for the excitation of surface electromagnetic waves on a slide with a thin metal film 7. Depending on the diameter of the light beam and the diameter of the polarizer, the polarizer 4 can be placed on the optical axis of the light beam either inside the collimator, or between the collimator and the cylindrical lens 5. A beam of polarized light rays passes through a cylindrical lens 5, which focuses the beam of light rays along after it passes through the lateral face of prism 6 into a narrow strip on a slide with a thin metal film 7 located on the hypotenuse face of prism 6 of the device for impaired total internal reflection. A cylindrical lens 5 forms a converging beam of light with a continuous spectrum on the reflecting element of the device of the impaired total internal reflection in such a way that the necessary range of angles of incidence of light on the slide is provided. The reflected light is then laid out by the dispersing element and a focusing lens forms an image on the photomatrix, where each row of pixels corresponds to a certain wavelength, and to each column a certain angle of incidence. Thus, under the influence of a cylindrical lens 5, the incidence of a beam of light rays occurs in a certain range of angles, and each wavelength corresponds to its own resonant angle of incidence. Reflected from the slide with a thin metal film 7 on the hypotenous face of the prism 6 of the device for impaired total internal reflection, the beam of light rays exits through the second side face of the prism 6 and passes through the dispersing element in the form of a diffraction grating 8, whose strokes are parallel to the plane of incidence. Therefore, the beam of light rays is expanded along the wavelengths in the vertical direction. In the first diffraction order, a focusing lens 9 is located, in the focus of which a photomatrix 10 is located.

Due to this arrangement and such a geometry of the device elements, the incident light forms an image on a photomatrix, where each row of pixels corresponds to a certain wavelength, and to each column a certain angle of incidence of light. The proposed technical solution is structurally arranged so that during the measurement process the light spot on the slide remains stationary. This makes it possible to significantly increase the accuracy of measuring surface plasma resonance and, more importantly, detect its small changes. The image obtained from the photomatrix allows you to get a more accurate spectral characteristic of the test substance on the slide.

Figure 4 presents a General view of the installation mounted on an optical table of optomechanical components from Thorlabs. A Osram 12 V, 10 W halogen lamp was used as a light source 1 with a continuous spectral range. Collimator 2 was assembled from lenses with a focal length F1 = 30 mm (d = 25 mm), F2 = 35 mm (d = 25 mm), F3 = 80 mm (d = 50 mm), aperture 3-1 mm, polarizer 4 LPVIS. Then follows an adjustable rectangular diaphragm 3 with a rectangular hole with a height of h = 10 mm and a width of d = 5-50 mm. The screen 11 behind it allows you to adjust the diameter of the light beam from 0 to 10 mm. Reflected from the mirror 12, the light passes through a cylindrical lens 5, 25 mm high, 50 mm wide, focal length F = 100 mm.

The device of the impaired total internal reflection consists of a rectangular triangular prism 6 (hypotenuse face measuring 30 by 20 mm in VK7 glass), a cuvette and slide 7 made of borosilicate glass 0.4 mm thick with a 40 mm thick gold film. Prism with a cuvette mounted on a rotating table 13, which allows you to set the desired angle of incidence of light rays.

After the device of impaired total internal reflection, the light beam is reflected from the mirror 14 and an additional cylindrical lens 15 with f = 100 MM is sent to the diffraction grating 8 (600 lines / mm). In the first diffraction order, the 10 Tholabs DCC1545M camera with a 9 f = 25.4 mm lens is located. The exposure time of the photomatrix is set to 10-15 ms. The operating range is 600-900 nm. The lower boundary is due to weak plasma resonance at short wavelengths. The upper bound is the sensitivity range of the photomatrix.

Figure 5 shows the image obtained from the camera. The wavelength changes along the vertical axis, and the angle changes along the horizontal axis. The dark area corresponds to the disturbed total internal reflection. The graph in FIG. 6 is a horizontal slice of the photograph and is actually a graph of light reflection versus incidence angle at a specific wavelength.

The presented setup, a spectrometer based on surface plasma resonance, allows to obtain a surface plasma resonance spectrum in the continuous optical wavelength range in real time, as well as to get rid of thermal noise and more accurately restore the spectral characteristics of the test substance, and thus significantly increase the sensitivity biodetector.

The proposed device - a spectrometer based on surface plasma resonance for obtaining a spectrum of surface plasma resonance in the continuous wavelength range belongs to the field of optical instrumentation and can be used to create markerless biosensors and biodetectors based on surface plasma resonance or for spectral analysis of a small amount of substance.

This design of the proposed spectrometer may be applicable for recording changes in protein concentrations on a biosensor matrix, for example, using the BIAcore ™ system (Pharmacia Biosensor AB). Such a system can be used for molecular diagnostics. It will also make it possible to measure the chemical constants of association and dissociation between biomolecules. In addition, the device can be used to control and record the concentration of chemical and biochemical substances in various industrial processes that occur using biological material.

Thus, the new interconnection of the known elements of the spectrometer and the additionally introduced cylindrical lens and photomatrix makes it possible to obtain a technical result that is not obvious for such an addition, namely, to significantly increase the sensitivity of the biodetector due to the possibility of measuring the spectral characteristics of the analyte in the continuous frequency range in real time, which, in in turn, it virtually eliminates the effect of thermal noise.

Information sources:

1. Patent GB 2197065A, CL G01N 33/543, 1988.

2. Patent KR 100856090, cl. G01N 21/25, 2008.

3. Patent DE 102007021563 A1, cl. G01J 3/42, 2008.

4. RF patent No. 2170913, class. G01J 3/42, 2001.

Claims (6)

1. A spectrometer based on surface plasmon resonance, comprising a continuous-spectrum light source, a collimator, a polarizer, a device for impaired total internal reflection with a reflecting element, a dispersing device and a focusing lens, characterized in that it additionally contains a photosensitive a photomatrix installed in the focus of the lens, and between the polarizer and the device of the impaired total internal reflection is installed a cylindrical lens or a cylindrical mirror. 2. The spectrometer according to claim 1, characterized in that the device of the impaired total internal reflection is made in the form of a prism or half cylinder. 3. The spectrometer according to claim 1, characterized in that the reflective element is made in the form of a dielectric plate with a metal coating. 4. The spectrometer according to claims 1 and 2, characterized in that the dispersing device is made in the form of a diffraction grating. 5. The spectrometer according to claims 1 and 2, characterized in that the reflective element is mounted on the hypotenuse plane of the prism. 6. The spectrometer according to claims 1 and 2, characterized in that the reflective element is mounted on the flat surface of the half-cylinder.

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