CN101750280A - Whispering-gallery-mode fiber optic biosensor - Google Patents

Abstract

The invention discloses a whispering gallery mode optical fiber biosensor, which has at least one optical fiber and at least one micro-resonant cavity, and the whispering gallery mode optical fiber biosensor can couple the light in the optical fiber into the micro-resonant cavity and excite the whispering gallery mode , the optical fiber biosensor also has a substrate that can be inserted into the substance to be measured, the optical fiber is Y-shaped, one branch of the Y-shaped optical fiber is the light incident end that can be connected to the light source, and the other branch is the light output end that can be connected to the detector, Y The lower end of the Y-shaped optical fiber is fixed on the substrate and a reflector is fixed at the end thereof, and the micro-resonant cavity is fixed on the substrate and coupled with the lower end of the Y-shaped optical fiber. When the present invention is used, the light source and the detection instrument are located on the same side of the micro-resonator cavity, which is convenient for detection and movement, and realizes the real-time detection of the analyte to be measured without marking the detection object. The substrate of this optical fiber biosensor can also be inserted into the In this way, the detection is more convenient, safe and stable, and field detection can also be realized. At the same time, this technical solution can couple light waves into the micro-resonator cavity twice, so that the accuracy and sensitivity of this whispering gallery mode sensor can be further improved.

Description

Whispering gallery mode fiber optic biosensor

technical field

The invention relates to an optical fiber sensor, in particular to an optical fiber biosensor using a micro-resonant cavity.

Background technique

As shown in Figure 1, the whispering gallery mode optical fiber biosensor includes an optical fiber and a micro-resonant cavity that can generate optical resonance, such a micro-resonant cavity is generally a microsphere, a microdisk or a microring.

Taking the microsphere resonator as an example, the microsphere resonator is a spherical optical resonator with a radius ranging from several microns to hundreds of microns. Through continuous total reflection on the inner surface of the microsphere, the microsphere cavity confines the light near the equatorial plane and orbits along the great circle, which excites a unique whispering gallery mode (WGM or WG for short). Due to the effect of total reflection, the light field outside the sphere is an evanescent field, and this light wave is a non-propagating wave, so the light that leaks out of the microsphere is extremely weak, so it can confine the light in a small volume for a long time Therefore, microsphere resonators have attracted much attention for their ability to store energy in a small volume for a long time. Because of the extremely high quality factor (up to 10 ¹⁰ ) and the extremely small mode volume of the microsphere resonator, it has unique advantages in the research fields of nonlinear optics, cavity quantum electrodynamics, low-threshold lasers and quantum optics.

The microsphere resonator is used in the field of sensors, and mainly uses the sensitive response of the microsphere resonator itself or the interaction between itself and the outside world, such as changes in frequency or spectrum. Generally speaking, many external factors can affect it, such as changing the distance between the coupling device and the resonant cavity, or allowing the tiny object to approach the evanescent field outside the sphere to affect the mode of the resonant cavity; the internal method of affecting it is to change the cavity Internal optical path, such as the deformation of the sphere or the change of the refractive index, etc. Due to the role of the microsphere resonant cavity, the performance indicators such as the accuracy and sensitivity of the biosensor, temperature sensor and acceleration sensor are greatly improved, and even single molecular substances can be determined.

The application of microsphere resonators in biosensors is to cause small changes in eigenmodes through the interaction of external tiny particles near the surface of the microspheres with the evanescent field outside the sphere, so that the laser wavelength changes to produce observable effects. Usually tapered fiber coupling is used, and the most basic coupling method is prism coupling (as shown in Figure 2). When a beam of light reaches the interface from the glass, when i>ic, total reflection will occur. According to the derivation conclusion of electrodynamics, there is an evanescent field in the air medium. The microsphere is placed in the appropriate position of the evanescent field to match the eigenmode of the microsphere cavity, and the external light is coupled into the microsphere from the external propagating wave, and the whispering gallery mode is excited in the microsphere cavity . Now, tapered optical fibers are generally used to achieve high-efficiency coupling.

However, since the microsphere resonant cavity should be set in the middle section of the optical fiber, the two ends of the optical fiber are respectively connected with the light source and the detection instrument. On both sides, it is not conducive to detection and movement. The existing whispering gallery mode sensor cannot be made into a probe shape. Therefore, it cannot be directly inserted into the analyte to be measured, and it is difficult to realize real-time monitoring in the field, and it cannot be directly inserted into a small microcavity. (eg intravascular).

Contents of the invention

The technical problem to be solved by the present invention is to provide a fiber optic biosensor in whispering gallery mode, which can detect the analyte in real time without marking the detection object, and can also move the fiber optic biosensor in whispering gallery mode conveniently and safely. sensor.

In order to achieve the above object, the technical solution of the present invention is: a whispering gallery mode optical fiber biosensor, which has at least one optical fiber and at least one micro-resonant cavity, and the micro-resonant cavity can couple the light in the optical fiber into the micro-resonant cavity and excite In the whispering gallery mode, the optical fiber biosensor also has a substrate that can be inserted into the substance to be measured. The optical fiber is Y-shaped. One branch of the Y-shaped optical fiber is the light incident end that can be connected to the light source, and the other branch is the light that can be connected to the detector. At the output end, the lower end of the Y-shaped optical fiber is fixed on the substrate and a reflector is fixed at the end thereof, and the micro-resonant cavity is fixed on the substrate and coupled with the lower end of the Y-shaped optical fiber. Due to the Y-shaped optical fiber and the substrate that fixes one end of the optical fiber, the light source and the detection instrument are located on the same side of the micro-resonator cavity, which is convenient for detection and movement, and realizes real-time detection of the analyte to be measured without marking the detection object. The substrate of the optical fiber biosensor is inserted into the analyte to be tested, so that the detection is relatively convenient, safe and stable, and field detection can also be realized. At the same time, in this technical solution, since the light wave is reflected by the mirror, the light wave can be coupled into the micro-resonator twice, so that the accuracy and sensitivity of the whispering gallery mode sensor are further improved.

The Y-shaped optical fiber is composed of two optical fibers, and one end of the two optical fibers is connected to form the lower end of the Y-shaped optical fiber.

The substrate is in the shape of a metal probe, and a groove for placing an optical fiber is opened on the substrate, and the lower end of the Y-shaped optical fiber is arranged in the groove. The use of metal probe-like substrates makes it easier to insert the metal probes into the analyte to be measured, especially into the human body, and a protective connection can be set on the outside of the substrate and the optical fiber to prevent the substrate from slipping and increase stability.

A sensitive layer capable of reacting to the analyte is attached to the outside of the microresonator. The sensitive layer is antibody, antigen, cell, nucleic acid, protein or molecular imprinted substance. There is also a nano-metal layer between the micro-resonant cavity and the sensitive layer, and the nano-metal layer is plated on the micro-resonant cavity.

An optical fiber protective plate is arranged on the base plate, the protective plate is fastened with the groove part of the base plate and wraps the lower end of the Y-shaped optical fiber in it, and there are multiple through holes on the area opposite to the groove of the base plate on the protective plate. With a protective plate, the sensor is convenient for storage and prolongs its service life.

The number of Y-shaped optical fibers is one or more. The optical fiber is a tapered optical fiber.

Description of drawings

Fig. 1 is the prior art schematic diagram as the basis of the present invention;

Figure 2 is a schematic diagram of microsphere resonator coupling;

Fig. 3 is a schematic diagram of the present invention;

Fig. 4 is the schematic diagram of another kind of Y-shaped optical fiber;

5 is a schematic cross-sectional view of the substrate and the protective plate;

Fig. 6 is a kind of coupling figure of microresonator and optical fiber;

Fig. 7 is a schematic diagram of the application of the present invention.

Detailed ways

As shown in Figure 3, the optical fiber biosensor of the whispering gallery mode of the present invention has an optical fiber 1, a microresonator cavity 2 and a substrate 7, the optical fiber 1 is Y-shaped, and a branch of the Y-shaped optical fiber 1 is a light incident end 3 that can be connected to a light source , the other branch is the light emitting end 4 that can be connected to the detector, the lower end 5 of the Y-shaped optical fiber is fixed on the substrate 7 and a mirror 6 is fixed at the end, and the micro-resonator 2 is also fixed on the substrate 7 and the lower end of the Y-shaped optical fiber 5 coupling, and can excite the whispering gallery mode, and the optical fiber at the coupling point with the micro-resonator adopts a tapered optical fiber. The substrate 7 has certain mechanical strength and can be inserted into the analyte to be tested. Since the Y-shaped optical fiber 1 and the substrate 7 at one end of the fixed optical fiber are provided, the substrate of this optical fiber biosensor can be inserted into the analyte to be measured, and the reflector 6 at the lower end of the Y-shaped optical fiber can reflect the light entering from the optical fiber incident end 3 Back, at the output end 4 of the optical fiber, a detector can be used to detect the reflected light, and its application is shown in Figure 7. In this way, the light source and the detection instrument are located on the same side of the micro-resonator cavity, which is convenient for detection and movement, and realizes the real-time detection of the analyte to be tested without labeling the test object. The substrate of this optical fiber biosensor can be inserted into the analyte to be tested. In this way, the detection is more convenient, safe and stable, and field detection can also be realized. It is also convenient for storage and prolongs the service life.

As shown in Figure 4, the Y-shaped optical fiber is composed of two optical fibers, one end of the two optical fibers is connected to form the lower end 5 of the Y-shaped optical fiber, and the reflector 6 can reflect the incident light of one optical fiber to the other optical fiber.

As shown in Figures 3 and 5, the substrate 7 is a metal probe, and a groove 8 for placing an optical fiber is opened on the substrate 7, and the lower end 5 of the Y-shaped optical fiber is arranged in the groove 8. The protective plate 9 of optical fiber can also be set on the base plate 7, and this protective plate 9 is buckled with the groove 8 part of base plate 7 and wraps the lower end 5 of Y-shaped optical fiber wherein, on the protective plate 9 and the groove 8 of base plate 7 The opposite area has a plurality of through holes 10 . The use of metal probe-like substrates makes it easier to insert the metal probe into the analyte to be measured, especially into the human body, such as blood vessels and cerebral effusion. The protective plate protects the optical fiber on the metal probe, and the through hole opened on the protective plate allows the analyte to be measured to enter the groove of the metal probe and contact the micro-resonant cavity.

A sensitive layer capable of reacting to the analyte is attached to the outside of the microresonator 2, and the sensitive layer is an antibody, antigen, cell, nucleic acid, protein or molecular imprinted substance, and the sensitive layer is treated with anticoagulation. There is also a nano-metal layer between the micro-resonant cavity and the sensitive layer, the nano-metal layer is plated on the micro-resonant cavity, and the sensitive layer is attached to the nano-metal layer. The substance in the sensitive layer can be combined with the corresponding analyte to be determined, and the micro-resonant cavity combined with the analyte will change its spectral performance, and the sensor with the sensitive layer of a specific substance can detect the specific analyte. When there are many kinds of substances in the sensitive layer, the sensor can detect more than one kind of analyte.

The optical fiber usually has a cladding layer, and the cladding layer should be stripped at the coupling position with the microresonator 2 . As shown in FIG. 6 , in order to enhance the coupling effect of the microresonator 2 , the core of the optical fiber is corroded so that its diameter reaches 1-5 μm.

The mirror on the optical fiber can be made by plating metal on the optical fiber. The number of Y-shaped optical fibers is one or more.

Fig. 7 shows the application of the present invention, the light incident end 3 of the optical fiber biosensor of the present invention is connected with the light source 12, the light exit end 4 is connected with the detector 13, the present invention is placed in the solution to be tested 11, and the tested Analytes are detected.

Claims (10)

1. A fiber optic biosensor of a whispering gallery mode, comprising at least one optical fiber (1) and at least one microresonator (2), the optical fiber (1) can couple light into the microresonator (2) and excite an echo Wall mode, characterized in that: the optical fiber biosensor also has a substrate (7) that can be inserted into the analyte to be measured, the optical fiber is Y-shaped, and a branch (3) of the Y-shaped optical fiber is a light that can be connected to a light source The incident end, the other branch (4) is the light exit end that can be connected to the detector, the lower end of the Y-shaped optical fiber (5) is fixed on the substrate (7) and the optical fiber end is fixed with a reflector (6), and the microresonator (2 ) is fixed on the base plate (7) and coupled with the lower end (5) of the Y-shaped optical fiber. 2. The optical fiber biosensor according to claim 1, characterized in that: the Y-shaped optical fiber is composed of two optical fibers, and one end of the two optical fibers is connected to form the lower end (5) of the Y-shaped optical fiber. 3. The optical fiber biosensor according to claim 1 or 2, characterized in that: the substrate (7) is metal probe-shaped, the substrate (7) has a groove (8) for placing an optical fiber, and the Y The lower end (5) of the shaped optical fiber is arranged in the groove (8). 4. The optical fiber biosensor according to claim 3, characterized in that: a sensitive layer capable of reacting to the analyte is attached to the outside of the micro-resonator cavity (2). 5. The optical fiber biosensor according to claim 4, characterized in that: the sensitive layer is an antibody, antigen, cell, nucleic acid, protein or molecular imprinted substance. 6. The optical fiber biosensor according to claim 4, characterized in that: the sensitive layer is a combination of antibodies, antigens, cells, nucleic acids, proteins or molecular imprinted substances. 7. The optical fiber biosensor according to claim 5 or 6, characterized in that there is a nano-metal layer between the micro-resonator cavity and the sensitive layer, and the nano-metal layer is plated on the micro-resonator cavity (2). 8. The optical fiber biosensor according to claim 7, characterized in that: the substrate (7) is provided with a protective plate (9) for the optical fiber, and the protective plate (9) is partly in contact with the groove (8) of the substrate. The lower end (5) of the Y-shaped optical fiber is fastened and wrapped therein, and a plurality of through holes (10) are provided on the protection plate (9) opposite to the groove (8) of the base plate. 9. The optical fiber biosensor according to claim 8, characterized in that: the lower end (5) of the Y-shaped optical fiber is a tapered optical fiber, and the cross-section of the end of the lower end (5) of the Y-shaped optical fiber is circular. 10. The optical fiber biosensor according to claim 1, characterized in that: the mirror (6) fixed at the end of the Y-shaped optical fiber (5) is made of gold-plated or silver-plated film.

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