CN102411003B

CN102411003B - Sensing method of far-field optical fiber evanescent field

Info

Publication number: CN102411003B
Application number: CN201110209294.5A
Authority: CN
Inventors: 庄须叶; 罗吉; 姚军
Original assignee: Institute of Optics and Electronics of CAS
Current assignee: Institute of Optics and Electronics of CAS
Priority date: 2011-07-25
Filing date: 2011-07-25
Publication date: 2014-05-14
Anticipated expiration: 2031-07-25
Also published as: CN102411003A

Abstract

The invention discloses a sensing method for the evanescent field of far-field optical fiber. The micro-nano effect formed under the excitation of the evanescent field transfers the evanescent field energy in the near field to the far field, which enhances the detection range of the optical fiber evanescent field sensor, and improves the comprehensiveness and fidelity of the detection results when the optical fiber evanescent field sensor detects inhomogeneous media. , and improve the sensitivity of the sensor.

Description

The method for sensing of a kind of far field fiber evanescent field

Technical field

The invention belongs to optical fiber biochemical sensor technical field, relate to the optical fiber biochemical sensor for fields such as medical treatment detection, environmental monitoring and biochemical anti-terrorism inspections, be specifically related to a kind of evanescent field energy by near field and be induced to the detection method of the far field fiber evanescent field biochemical sensor detecting in far field.

Background technology

Fiber evanescent field sensor is the Fibre Optical Sensor of a kind of new function type of putting forward the eighties in last century, it utilizes the evanescent field energy that sensor fibre excites to interact with the measured matter within the scope of energy, cause the absorption of transmitting energy in optical fiber, reflect the specifying information of test substance by energy variation, as refractive index, concentration etc. realize sensing effect.According to different working environments and measurement object, far field and near field are divided, generally speaking, centered by field source, the region in three wavelength coverages, is commonly referred near field, also can be described as induction field; Centered by field source, radius is that three spatial dimensions outside wavelength are called far zone field, also can be described as radiation field.

When light transmits with the form of total reflection in optical fiber, can produce an energy field being penetrated in fibre cladding in the interface of fiber core layer and covering, this field energy is decayed rapidly along with the increasing apart from fiber core interface distance is far index, its penetration depth only has the size of a wavelength magnitude of incident light, is typical near-field energy.The energy far fieldization of the evanescent field near field can effectively be improved to the reach of fiber evanescent field sensor and measured matter, obtain more comprehensively information the effectively sensitivity of raising sensor of measured matter, therefore by the evanescent field energy far field near field, performance improvement and the Developing Extension to fiber evanescent field sensor has important practical significance.

Because evanescent field energy can only interact at the near-field region of several wavelength coverages and test substance, in the time that being detected, some special test substance there will be the incomplete situation of detection information.The measured matter being evenly distributed in solvent for solute can obtain more comprehensive detection information, but for solute test substance pockety in solvent, as suspension, emulsion etc., because near field reach can not show solute information pockety completely, cause fiber evanescent field sensor can not reflect the full detail of test substance, there is information distortion, detect error larger.According to document [in water conservancy, Shang Qinghai, Li Guibai, is suspended particle optical detection theory, HarBin Building University's journal, 2001,34 (1): 49-52] report, when suspension small volume, as 0.1mm ³in sample, the average of numbers of particles is 104, standard deviation is 100, numbers of particles in continuous sample has in average ± 2% difference, numbers of particles relative changing value is larger, while detection, can cause measuring error and information distortion significantly for such test substance with general fiber evanescent field sensor.Simultaneously, in the fibre cladding region of low-refraction, decay rapidly as the evanescent field energy near field, limited with the reach of test substance, and evanescent field energy a little less than, after sensing, very little being difficult to of the energy variation amount of optical fiber measures, and limited the raising of transducer sensitivity.

Summary of the invention

(1) goal of the invention

For solving the low problem of information distortion, detection sensitivity that in background technology, fiber evanescent field sensor exists, the object of the invention is to provide the method for sensing of a kind of novel far field fiber evanescent field.

(2) technical scheme

For achieving the above object, the invention provides micro-nano particle that a kind of utilization is suspended in sensor fibre surrounding by the method for sensing in the evanescent field far field near field, the method for far field of the present invention fiber evanescent field sensing, the step of described method is as follows:

Step S1: within sensor fibre sensitive segment is hung on to reaction tank, utilize micro-nano particle to modify measured object liquid, measured object liquid is fully mixed with micro-nano particle, obtain micro-nano particle and the well-mixed suspension of measured object liquid, and the suspension of micro-nano particle is distributed in measured object liquid;

Step S2: the measured object liquid that contains micro-nano particle is poured in the groove in reaction tank device, and micro-nano particle around sensor fibre sensitive segment, makes surrounding's formation micro-nano particle network array of the sensor fibre of fiber evanescent field by measured object liquid suspension;

Step S3: utilize the micro-nano effect of micro-nano particle that the evanescent field energy near field is delivered to far field.

(3) beneficial effect

This far field provided by the invention fiber evanescent field method for sensing, makes the evanescent field energy near field and the reach of test substance reach the far-field range of 4 μ m, can be wider react with more test substance.Can carry out comprehensive reliable detection to the fluid to be measured information that solute Distribution is inhomogeneous, solve the information distortion problem that traditional evanescent field method for sensing detects for the testing liquid of solute uneven distribution, and the sensitivity that has improved sensor.

Accompanying drawing explanation

Fig. 1 a is the perspective view of reaction tank.

Fig. 1 b is reaction tank structural front view.

Fig. 2 is the structural representation of the overall transducing part of invention.

Fig. 3 is the block diagram that micro-nano particle is modified measured object liquid.

Fig. 4 a to Fig. 4 d is that micro-nano particle is by evanescent field far field schematic diagram.

Fig. 5 is the field energy distribution plan of metal micro-nano particle.

Fig. 6 is the field energy distribution plan of the medium micro-nano particle of high index of refraction.

Embodiment

For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

1. be the perspective view of reaction tank as Fig. 1 a, the front view that Fig. 1 b is reaction tank, Fig. 1 a illustrates and comprises reaction tank 1, groove 2, semicircle cylindrical passageway 3 and reaction tank support portion 4; The step of introducing reaction tank making is below:

Process a groove 2 for holding measured object liquid in rectangular-shaped dimethyl silicone polymer (PDMS) reaction tank support portion 4, described groove 2 is semicircle cylindricality, sets a semicircle cylindrical passageway 3 at the two ends of groove 2; The radius of groove 2 is 0.5mm-10cm, and in the smaller semicircle cylindrical passageway 3 of semi-cylindrical groove 2 two ends radius of machinings, semicircle cylindrical passageway 3 radiuses are 0.3mm-0.5cm, and semicircle cylindrical passageway 3 is for placing sensor fibre 5.

Fig. 2 is the structural representation of the present invention's entirety transducing part, contains the sensor fibre 5 of covering shown in Fig. 2, removes the sensor fibre sensitive segment 6 of covering; The step of introducing fixing sensor fibre 5 is below:

Choose the sensor fibre 5 of a segment length at 40cm-80cm, one section of 10cm-30cm is wherein removed to covering as sensor fibre sensitive segment 6, sensor fibre sensitive segment 6 is hung on reaction tank 1, the two ends of sensor fibre 5 are placed in to semi-cylindrical passage 3 regions that radius is less, by bonding good to sensor fibre 5 and reaction tank support portion 4 use bonding agents, be integrally formed the detecting means of structure as Fig. 2 again.

2. as illustrating micro-nano particle, Fig. 3 modifies the step of measured object liquid, the liquid of measured object shown in it 7 and micro-nano particle 8; Within sensor fibre sensitive segment 6 is hung on to reaction tank 1, the step of utilizing micro-nano particle 8 to modify measured object liquid 7 is: the micro-nano particle 8 of making is put into the beaker that fills measured object liquid 7, stir, micro-nano particle 8 is fully mixed with measured object liquid 7, not there is not chemical reaction with micro-nano particle 8 in measured object liquid 7, obtain micro-nano particle 8 and the well-mixed suspension of measured

object liquid

7, and 8 suspensions of micro-nano particle are distributed in measured object liquid 7.

3. the measured object liquid 7 that contains micro-nano particle 8 obtaining is poured in the semi-cylindrical groove 2 in reaction tank 1, micro-nano particle 8 is suspended in around sensor fibre sensitive segment 6 by measured object liquid 7, makes surrounding's formation micro-nano particle network array of the sensor fibre of fiber evanescent field; As shown in Fig. 4 a to Fig. 4 d, be that micro-nano particle is by the signal in evanescent field far field, Fig. 4 a, Fig. 4 b are the schematic diagram that two kinds of micro-nano particles are suspended in sensor fibre sensitive segment 6, micro-nano particle 8 shown in Fig. 4 a, Fig. 4 b is divided into metal micro-nano particle 9 and medium micro-nano particle 10, metal micro-nano particle 9 is controlled at 0.01 λ-100 λ with the characteristic dimension of medium micro-nano particle 10, λ is the long wavelength of incident light source, the refractive index of medium micro-nano particle 10 is 0.8n-3n, and n is fiber core refractive index.Fig. 4 c is high refractive index medium particle scattering field energy distribution schematic diagram, and Fig. 4 d is the lower dipole vibration of single elliptical metal micro-nano Particle Field excitation field energy distribution schematic diagram.

Principle of work of the present invention is: of the present inventionly to the effect that by micro-nano particle 8, testing liquid 7 is modified, utilizing suspends is distributed in sensor fibre sensitive segment 6 micro-nano particle 8 around, near-field energy is passed to far field and carries out sensing.Micro-nano particle 8 can be divided into metal micro-nano particle 9 and 10 two kinds of modes of action of medium micro-nano particle by the micro-nano effect in near-field energy far field according to the difference of particle material used, specific as follows:

1) utilize metal micro-nano particle 9 that the evanescent field energy near field is delivered to far field

The characteristic dimension of metal micro-nano particle 9 used is controlled at 0.1 λ-10 λ, the long wavelength that λ is incident light source.Metal micro-nano particle 9 is distributed in around sensor fibre sensitive segment 6 by suspended pattern, because evanescent field excitation produces certain disturbance, has destroyed the electric neutrality of certain regional area in the plasma of metal micro-nano particle 9, cause electronics surplus.The electric field that excess electron produces, forces electronics certain part from the destroyed region of electric neutrality outwards to be moved, and the electronics of going out from this part, region is too much, produces reversed electric field, electronics is retracted but can not stop in time, again occurs superfluous.Said process constantly back and forth, formed the collective oscillation of a large amount of electronics in plasma.The metal micro-nano particle 9 that suspension is distributed in sensor fibre sensitive segment 6 forms after dipole vibration under the excitation of evanescent field, and the evanescent field energy near field is induced to far-field region.

2) utilize medium micro-nano particle 10 that the evanescent field energy near field is delivered to far field

The refractive index of used medium micro-nano particle 10 is 0.8n-3n, and n is fiber core refractive index, and characteristic dimension is controlled at 0.01 λ-100 λ, the long wavelength that λ is incident light source.Medium micro-nano particle 10 is suspended in the surrounding of sensor fibre sensitive segment 6, in the time that the size of incident wavelength and Jie's micro-nano plasmid 10 is comparable, there is relying on the resonance effects of shape, evanescent field is after the scattering of medium micro-nano particle 10, refraction, transmission effect, there is asymmetric distribution in field energy, therefore can utilize the effects such as the scattering of evanescent field energy on medium micro-nano particle, refraction, transmission by the far field that is delivered to of near-field energy.

Utilize metal micro-nano particle 9 and medium micro-nano particle 10 that the simulation example in the evanescent field energy far field near field is illustrated:

1) fiber core refractive index of sensor fibre 5 used is 1.4457, and radius is 8 μ m, optical source wavelength 1.55 μ m.Particle is elliposoidal nano Au particle, its DIELECTRIC CONSTANT ε _rfor-6.2403+0.54037i, the characteristic dimension of ellipsoidal particle is respectively two kinds of major axis 700nm, minor axis 200nm and major axis 1.5 μ m, minor axis 0.5 μ m, surrounding environment refractive index is 1.33, by random ellipsoid gold micro-nano particle sensor fibre sensitive segment 6 surroundings that are suspended in, ellipsoidal particle spacing be 200nm～500nm not etc., as Fig. 5 illustrates the distribution of metal micro-nano particle magnetic field z durection component field energy, can obtain fibre core evanescent field energy around and can be delivered to 4.5 μ m by 1 μ m, can realize the evanescent field energy near field is realized to far field.

2) fiber core refractive index of sensor fibre 5 used is 1.4457, and radius is 8 μ m, optical source wavelength 1.55 μ m.The refractive index of medium micro-nano particle 10 is 1.47, and radius is that the spherical medium micro-nano particle of 500nm, 200nm, 800nm and the distance of fibre core are respectively 100nm, 200nm, 300nm, and environment refractive index is 1.33.The energy profile of electric field z component as shown in Figure 6, the reach that can obtain evanescent field expands to 3 μ m by 1 initial μ m, can realize and the evanescent field energy near field is passed to far field carries out sensing, make test substance occur wider, more completely with more interaction, thereby make information that sensor surveys more comprehensively, fidelity and highly sensitive more.

The above; be only the embodiment in the present invention, but protection scope of the present invention is not limited to this, any people who is familiar with this technology is in the disclosed technical scope of the present invention; can understand conversion or the replacement expected, all should be encompassed in of the present invention comprise scope within.

Claims

1. A sensing method of far field optical fiber evanescent field, is characterized in that, sensing step comprises as follows:

Step S1: Suspend the sensitive section of the sensing fiber in the reaction tank, use micro-nano particles to modify the liquid under test, fully mix the liquid under test with the micro-nano particles, and obtain a suspension in which the micro-nano particles and the liquid under test are fully mixed Liquid, the liquid under test does not chemically react with the micro-nano particles, and makes the micro-nano particles suspend and distribute in the liquid under test;

Step S2: Pour the analyte liquid containing micro-nano particles into the groove in the reaction cell device, the micro-nano particles are suspended around the sensitive section of the sensing fiber through the analyte liquid, so that the sensing fiber of the optical fiber evanescent field A network array of micro-nano particles is formed around;

Step S3: using the micro-nano effect of the micro-nano particles to transfer the near-field evanescent field energy to the far-field, so that the range of action between the near-field evanescent field energy and the substance to be measured reaches the far-field range of 3 μm-4.5 μm.

2. the sensing method of the far-field optical fiber evanescent field as claimed in claim 1, is characterized in that, described reaction pool device manufacture step is as follows:

Step S11: Machining a groove on the support part of the cuboid polydimethylsiloxane reaction tank for containing the liquid to be tested, and setting a semi-cylindrical channel at both ends of the groove;

Step S12: The sensing optical fiber in the semi-cylindrical channel area is bonded to the supporting part of the reaction cell with an adhesive to form a sensing part of an integrated structure.

3 . The sensing method for the evanescent field of far-field optical fiber according to claim 1 , wherein the groove is semi-cylindrical, and the radius of the semi-cylindrical groove is 0.5mm-1cm.

4. The sensing method of far-field optical fiber evanescent field according to claim 2, characterized in that, the semi-cylindrical channel has a radius of 0.3mm-0.5mm and is used for placing the sensing optical fiber.

5. The sensing method for the evanescent field of far-field optical fiber according to claim 1, wherein the micro-nano particles include metal micro-nano particles and medium micro-nano particles.

6. The sensing method of far-field optical fiber evanescent field as claimed in claim 5, characterized in that, the characteristic size of the metal micro-nano particles and medium micro-nano particles is controlled at 0.01λ-100λ, and λ is the longest of the incident light source wavelength.

7. The sensing method of far-field optical fiber evanescent field according to claim 5, wherein the refractive index of the medium micro-nano particles is 0.8n-3n, and n is the core refractive index of the sensing optical fiber used.