Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
  • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
  • G01N21/7703—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides
  • G01N21/774—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides the reagent being on a grating or periodic structure
  • G01N21/7743—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides the reagent being on a grating or periodic structure the reagent-coated grating coupling light in or out of the waveguide
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
  • G01N21/03—Cuvette constructions
  • G01N2021/0385—Diffusing membrane; Semipermeable membrane

Definitions

• the present invention relates to a method for the selective detection of specific substances in a measurement sample by determining changes in the effective refractive index with a grating coupler according to the preamble of claim 1
• Lattice coupling is a known method for exciting a guided mode in an optical waveguide. If the diffraction grating is operated as an integrated optical sensor, the effective refractive index (in the grating area) changes as a result of the sensor experiment, i.e. for example as a result of the coupling of the specific substances to the chemo-sensitive waveguide. This change in the effective refractive index can be sensed in a variety of ways.
• WO 86 07149 US-A4,815, 843 describes a few of these possibilities, for example it is proposed to measure the intensity of an uncoupled diffraction order with a photodiode in order to determine effective changes in refractive index. This type of measurement has a small dynamic range and requires movable mechanics to adjust the coupling angle and is also sensitive to light intensity fluctuations that come from the light source.
• the grid- Coupling element should be able to be used in diagnostics as a disposable sensor chip ( 1 ) and must therefore be able to be manufactured very cheaply in terms of production technology, so that surface treatment of the end face of the grating coupling element is out of the question.
• sol-gel layers are used as wave-guiding films, which are always microporous. Microporous layers cause the sensor signal to drift due to water sorption and, because of their structure, are unsuitable for achieving extremely high refractive indices and thus increased sensitivity.
• a multidiffractive grating structure is defined in such a way that after the incidence of a coherent light beam on the multidiffractive grating structure, light beams diffracted such that the light beams diffracted directly at the multidiffractive grating structure are generated by the excitation decoupled light beams are separated angularly.
• the invention solves the problem of creating a method which allows the effective changes in refractive index to be sensed without the use of movable mechanics.
• an incident fan-shaped light field and an extensive homogeneous diffraction grating with weak coupling an incident converging wave leaves the grating as a diffracted diffracted wave; a guided mode leaves the grating approximatively as a plane wave when the coupling is weak
• a position-sensitive detector in a diffracted light field having a bright light spot in particular dependencies on movable mechanics, expensive optical surface treatments and fluctuations in light intensity are avoided.
• Figure 1 shows a measuring device for performing the method.
• Figure 2 shows a measuring device with a lens and an aperture.
• FIG. 3 shows a measuring device which, thanks to multiple mirroring of the beam path, has a compact structure.
• FIG. 4 shows a measuring device for a biochemical application including a cuvette.
• FIG. 5 shows an expanded measuring device which enables coupling in both directions of propagation and thus also the absolute measurement of the effective refractive index.
• a grating coupler 10 contains a substrate 2 (for example made of plastic or glass) and a porous or non-porous waveguiding film 3 connected therewith (made of Zr0 2 , Nb0 5 , Ti0 2 , Ta 2 0 5 or other high-density films, for example) materials with, for example, a refractive index above 2.0) as the waveguide 1 and a diffraction grating 4, with either the film 3 itself being selected chemically sensitive or this being provided with a chemically sensitive substance 14 (see FIG. 2) and the grating 4 at the upper or lower boundary surface of the waveguiding film 3 can be arranged.
• Vacuum coating methods are mainly used to produce highly refractive, non-porous, waveguiding films 3.
• a light beam 5 from a monochromatic light source (not shown), which is directed onto the grating 4, can be coupled in via the grating 4 or coupled out via the same grating 4, the coupling angle ⁇ - * being determined by the coupling equation
• N sine., ⁇ 1 ( ⁇ / ⁇ ) are given.
• N is the effective refractive index of the guided mode
• ⁇ - the coupling or decoupling angle
• 1 the associated diffraction order (+1 describes the coupling equation, -1 the coupling equation)
• ⁇ the wavelength
• ⁇ the grid period.
• a fan-shaped light field 6 in the plane of incidence is directed onto the grating 4, the focus of this fan-shaped light field 6 preferably being directly on the grating structure.
• the grating coupler 10 can also be illuminated with a small opening angle, angularly adjustable fan-shaped light field 6, without the position of the illuminated grating position shifting. This ensures a sufficiently high light intensity of the guided mode 16.
• the angular adjustment of the fan-shaped light field 6 can be carried out, for example, with the aid of an electromagnetic mirror, as used in the Philips video disk players, and a lens, in that the lens is arranged between the electromagnetic mirror and the grating coupler 10 such that the focus of an incident one is imaged on the electromagnetic mirror-focused fan-shaped light field through the lens onto the diffraction grating 4.
• an electromagnetic mirror as used in the Philips video disk players
• a lens in that the lens is arranged between the electromagnetic mirror and the grating coupler 10 such that the focus of an incident one is imaged on the electromagnetic mirror-focused fan-shaped light field through the lens onto the diffraction grating 4.
• a mirror rotation leads to an angular change in the fan-shaped light field 6 focused on the diffraction grating 4, but not to a shift in the position of the illuminated grating point.
• the guided mode 16 becomes longer Coupled out distance, which is also referred to as the coupling length, so that the decoupled Lichtfeider 17, 20 approximate plane waves (see Figures 2 and 3).
• These outcoupled light fields 17, 20 are thus inevitably offset laterally by the order of magnitude of the coupling length compared to the directly captured light fields 8, 9, 11.
• the weak coupling guarantees both spatial and spatial frequency separation of the coupled-out light fields 17, 20 from the directly diffracted light fields 8, 9, 11 Weak coupling is achieved, for example, by keeping the modulation of the diffraction grating 4 small.
• FIG. 2 there is a position-sensitive detector 7 in the area of a light field 9 of a diffraction order that is not coupled in or emitted by the grating.
• a light field 17 which is produced by the coupling of the guided mode 16 on the grating 4
• the coupling angle ⁇ -,... Changes according to the coupling equation, which results in a shift of the bright light spot 12 in the light field 9.
• This displacement of the light spot 12 can be registered with the position-sensitive detector 7.
• This type of registration is independent of fluctuations in the light intensity of the decoupled light field 17 and the directly diffracted light field 9.
• a position-sensitive detector such as, for example, the S3979 from Hamamatsu
• the intensity of a light spot can also be determined in addition to the position 12 and thus indirectly also the intensity of the guided mode 16 can be measured.
• a convex lens 18 is preferably placed between the diffraction grating 4 and the position-sensitive detector 7 such that the light field 17, which is approximately coupled out as a plane wave, is focused on the position-sensitive detector 7.
• the position-sensitive detector 7 is thus located in the focal plane of the lens 18. Since the directly diffracted light field 9 is radiated in a fan shape, this light field appears in the focal plane of the lens 18 as an unfocused light distribution and therefore does not impair the position determination of the focused and coupled-out light field 17 generated light spots 12.
• this aperture 19 is placed between the diffraction grating 4 and the lens 18, preferably in the immediate vicinity of the grating coupler 10, where the decoupled light field 17 is spatially separated from the directly diffracted light field 9 thanks to weak coupling, since the decoupled light field 17 radiates in a fan-shaped manner
• Light field 9 is always laterally offset by the order of magnitude of the coupling. It can thus be achieved with a diaphragm 19 that the light field 9 is at least partially blocked off without disturbing the decoupled light field 17.
• the position-sensitive detector 7 is placed in the directly transmitted or reflected light field 8, 11, the use of a diaphragm 19 is strongly recommended in order to avoid illuminating the position-sensitive detector 7 with the intensive, directly transmitted or reflected light field 8, 11 ( see Figure 3).
• the light beam paths are preferably at least partially protected from air turbulence and temperature fluctuations in the environment, so that the noise caused by these disturbances in the position of the light spot 12 is suppressed and consequently the resolving power of the measuring apparatus is improved.
• tubes or solid transparent media e.g. made of glass or plastic
• Transparent media with very low temperature and thermal expansion coefficients for example made of quartz or Zerodur, are preferably used.
• the extent of the measuring arrangement can be reduced by reflecting the light beam paths.
• mirrors 22 can be attached to the surface of a transparent body 21 having a small temperature or thermal expansion coefficient, which is placed between grating coupler 10 and position-sensitive detector 7 in such a way that the outcoupled light field 17, 20 moves in or out multiple reflection hits the position-sensitive detector 7.
• This body whose entry and exit surfaces relevant to the beam path are preferably provided with an anti-reflective layer 23, simultaneously protects the beam path against air turbulence.
• Chemosensitive waveguide and grating period must be configured such that the guided mode 16 does not experience any Bragg reflection during the measurement of the change in the effective refractive index. For example, this is achieved in that the light field 17 producing the bright light spot 12 does not leave the diffraction grating 4 vertically.
• the generation of a retroreflected mode causes interference.
• the retroreflected mode can also be coupled out approximately in the form of a plane wave and form a second light spot on the position-sensitive detector 7.
• the measuring method according to the invention is particularly interesting for bioanalytics.
• the detection of an immunochemical reaction may be mentioned as an example.
• FIG. 4 there is an antibody or antigen layer on the grid 4, which in this case corresponds to the chemo-sensitive substance 14.
• the Liquid measurement sample 13 with the antigen or antibody is injected into the cuvette 15 or drawn in via capillary action.
• the coupling of the two immunological partners causes a change in the effective refractive index and thus a shift in the light spot 12 on the position-sensitive detector 7.
• it is advantageous to use a cuvette with a cuvette depth of less than 500 ⁇ to use see Phil. Trans. R. Soc. Lond. B 316, 143-160 (1987)).
• the measuring principle can also be used for other binding-specific partners.
• the measuring principle can also be used in connection with a "competition assay” or “sandwich assay”.
• Binding-capable macromolecules or beads made of plastic (polystyrene, latex), high-index glass (Ti0 2 , LiNb0 3 , glass) or metal (gold, titanium, aluminum) are often used for signal amplification, which are also known in the literature as a 'refractive index label''are designated.
• These binding 'refractive index labels' can be bound reversibly as well as irreversibly and form a third reagent in addition to the immobilized binary substance 14 and the substance to be detected. It is also conceivable, for example, that the 'refractive index label' is located on the cell wall opposite the grid 4 and does not dissolve until the liquid measurement sample is drawn in.
• Other assays can also be performed with three reagents.
• the method according to the invention can also be used generally for the detection of reactions taking place on or in the chemo-sensitive waveguide 1 due to the specific substance.
• a change in refractive index can occur when an substrate is converted by an enzyme immobilized on the waveguiding film 3.
• the substrate forms the specific substance and the enzyme forms the chemo-sensitive substance 14.
• enzyme can also lead to the formation of an insoluble product which is deposited on the surface of the chemo-sensitive waveguide 1.
• the chemo-sensitive substance 14 consists, for example, of a membrane
• reactions taking place in or on the membrane can cause the distance of the membrane from the waveguiding film 3 or the structure or the thickness of this membrane to change due to the specific substance.
• This method represents an amplification mechanism so that small molecules to be detected can also cause major changes in the effective refractive index.
• the cuvette wall opposite the diffraction grating 4 should preferably consist of a material that is light-absorbing and / or has a reflection that is as small as possible in order to suppress disturbing reflections.
• the guided mode 16 relevant for the measurement should lie completely below the measurement sample 13, so that the guided mode 16 does not cross the boundary of the measurement sample 13 defined by the measurement sample 13 and chemo-sensitive waveguide 1 as a closed line.
• a deep refractive layer 2 ' between the substrate 2 and the waveguiding film 3 (see FIG. 4).
• This deep refractive layer 2 ' should possibly be structurable. If a microporous deep refractive layer 2 'is covered with a non-porous wave-guiding film 3, no water sorption can take place in the micropores of the deep refractive layer 2'.
• the proposed measurement setup can also be expanded in such a way that a mode 16 'is excited with a second fan-shaped light field 6' in the direction of propagation opposite to mode 16, as a result of this mode 16 ' Decoupling in the diffracted fan-shaped light field 9 'produces a bright light spot 12' and the change in the effective refractive index of this second mode 16 'is measured via the displacement of the light spot 12' with a second position-sensitive detector 7 '.
• the two fan-shaped light fields 6 and 6 ' can strike the grating 4 at the same time or in a multiplex process.
• the autocollimation angle can be calculated via the resonance incidence angle for mode excitation in the forward and backward directions, and the effective refractive index can thus be determined quantitatively. Since the coupling angle and the coupling angle are of the same magnitude for both directions of propagation and in the measuring device (see FIG. 1) the coupling angle o. *
• the change in the effective refractive index due to the incubation can be measured since the effective refractive index is recorded quantitatively.
• the autocollimation angle position is determined in each case from the two positions of the light spots 12 and 12 'on the corresponding position-sensitive detectors 7 and 7'. Minor angular repositioning errors when inserting the grating coupler 10 into the expanded measuring device thus play practically no role.
• the method according to the invention can be operated in a simple manner using an honor channel, since the measuring method represents a reflection method.
• several grids, grating strips or larger 2-dimensional grids can be used.
• the various lattice regions with different chemo-sensitive ones then become Substances 14 occupied.
• One of these channels can also be operated as a reference channel, for example.
• the bright light spot 12 in FIG. 1 corresponds to a dark spot 12 "and can be observed in the light fields 8, 9, 11 of the non-coupled diffraction orders, especially in the zeroth reflected diffraction order
• the absorptive waveguide 1 means that the coupled-in light can no longer decouple, but rather that the energy is consumed in the absorptive waveguide 1. This light is then missing in the diffraction orders that are not coupled in or emitted and thus produce the dark spot 12 "in the light fields 8, 9, 11.
• a strong coupling is advantageous here.
• the position-sensitive detector 7 must be designed such that the position of the dark spot 12 "can be registered. This type of registration can be carried out, for example, with a photo diode array.

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Plasma & Fusion (AREA)
• Health & Medical Sciences (AREA)
• Engineering & Computer Science (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Investigating Or Analysing Materials By The Use Of Chemical Reactions (AREA)

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• 1991
  • 1991-07-02 CH CH1954/91A patent/CH681920A5/de not_active IP Right Cessation
• 1992
  • 1992-06-19 WO PCT/CH1992/000117 patent/WO1993001487A1/de not_active Application Discontinuation
  • 1992-06-19 EP EP92912252A patent/EP0551456A1/de not_active Withdrawn
  • 1992-06-19 JP JP4511206A patent/JPH06500636A/ja active Pending

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