CN100414289C - Manufacturing method of sol-gel film air-sensitive sensor - Google Patents
Manufacturing method of sol-gel film air-sensitive sensor Download PDFInfo
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- CN100414289C CN100414289C CNB2005100254988A CN200510025498A CN100414289C CN 100414289 C CN100414289 C CN 100414289C CN B2005100254988 A CNB2005100254988 A CN B2005100254988A CN 200510025498 A CN200510025498 A CN 200510025498A CN 100414289 C CN100414289 C CN 100414289C
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- fiber grating
- refractive index
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Abstract
The present invention discloses a manufacturing method of a sol-gel film air-sensitive sensor, which has the manufacturing step and method: (1) the selection of fiber gratings; (2) the determination of filming thickness; (3) the cladding film coating of fiber gratings; (4) the preparation of multi-hole air-sensitive thin films; (5) the manufacture of sensing heads. The present invention provides the manufacturing method of a sol-gel film air-sensitive sensor which has the characteristics of miniaturization, high integration, telemetering and high sensitivity. The manufactured sensor applying to the method has very high sensibility to the tested air, and the measurement resolution of the film refractivity is as high as 10<-8>. The present invention which centralizes the structural advantages of the thin-film sensor and the fiber gratings can be widely applied to the photochemistry sensor.
Description
Technical field
The present invention relates to a kind of manufacture method of air-sensitive sensing head, especially a kind of manufacture method of film gas-sensitive sensing head.
Background technology
In recent years, sol-gel technique is to develop a kind of comparatively rapidly material preparation technology that can obtain to have various superior functions, be suitable for various specific (special) requirements, especially in the film preparation field, control, film have distinct advantages such as porous structure and specific surface area are big easily owing to mix, and make it cause that in the sensing material preparation field people pay attention to greatly.The optical thin film sensing head is compared with the block sensing head of traditional electricity type, and it has anti-electromagnetic interference (EMI), dynamic range is big, highly sensitive, response is fast characteristics; Do not electrically contact owing to have, it is particularly suitable for detecting inflammable, explosive gas.
Utilize the variation of all characteristics of light and matter interaction front and back optics,,, can realize the miniaturized device that the ratio of performance to price is high in conjunction with optical fiber technology, light integrated technology by advanced person's detection means.Long period fiber grating (long-period fiber grating, LPFG) be that photic fiber core refractive index changes optical fibre device, its cycle is far longer than the general optical fiber grating, scope from hundreds of microns to 1 millimeter, the tens of millimeters of grating length, the index modulation amplitude reaches 10
-4Or it is bigger.Since the nineteen ninety-five reported first since have be easy to make, advantages such as insertion loss is low, the backreflection loss is low, compact conformation, be widely used in optical fiber communication and sensing head field.
Because its cycle of LPFG is bigger, has coupling between modes in the same way.Produce coupling between the cladding mode of guided mode and transmission in the same way, the specific wavelength that satisfies phase-matching condition is coupled into covering by fibre core and propagates forward.Therefore, scattering loss is attenuated very soon, occurs a series of loss peak in the observed optical fiber transmission spectrum of output terminal.Identical with the Bragg fiber grating, LPFG is equally to changing the measured sensitivity of grating cycle or change fibre core, cladding index.Different with the Bragg fiber grating is, LPFG is especially responsive to the variations in refractive index of covering surrounding medium, and resolution can reach 10
-5, therefore can be used as environment refractive index sensing head.Aspect chemical sensitisation, be mainly used in solution concentration at present and measure.
Measure the concentration of glycol, salt, sugar juice with LPFG, the result shows that long period fiber grating not only can distinguish different chemical solutions according to the difference of refractive index, also can be used to monitor specific chemical solution concentration change, can be widely used in the petroleum industry.LPFG can also be used to detecting some aromatics in the kerosene raffinate, such as the content of benzene or dimethylbenzene.The minimum of xylene concentration is visited and is measured as 0.04% (volumetric concentration) in the binary heptane, corresponding to 6 * 10
-5Refractive index variable quantity, this detection resolution can be comparable with liquid chromatography(LC) instrument and ultraviolet spectrometer (UVS).
LPFG for above-mentioned use, usually fiber grating directly is immersed in the external agencys such as liquid, higher sensitivity is just arranged when having only the external environment condition refractive index to be less than or equal to the refractive index of fibre cladding under this condition, and this has just limited its application aspect chemical detection to a great extent.More than these all need LPFG is dipped in the chemical liquid, if can directly survey the concentration of object under test at LPFG outside plating one deck chemical-sensitive film, that will widen its range of application, bring bigger convenience.Especially if the sensitive thin film that plates has gas sensing property, then can be used as the gas sensing head.
Adopt Langmuir-Blodgeet technology (being called for short the LB technology) to control film thickness, at the nano level tricosenoic acid LB of optical fiber surface plating one deck film, thickness tens to hundreds of nm.Experimental result shows that the refractive index response characteristic of long period fiber grating obtains very big improvement, and has enlarged its sensing scope.When film thickness reached hundreds of nanometers, the centre wavelength of attenuation band and amplitude had very high susceptibility to the optical thickness of rete.But above-mentioned experimental work lacks the theoretical research to the optical sensitivity and the thickness relation of system, but these just to be the quick sensing head of phosgene design most important link.In addition, because organic (dyestuff) molecule has limited its detection to numerous gases to the specificity of gas molecule sensitivity; And, organic film molecule non-refractory, the therefore also application of incompatibility high temperature occasion.
Sol-gel technique makes it cause that in air-sensitive sensing material preparation field people pay attention to greatly because mix easily control, film have distinct advantages such as porous structure and specific surface area are big.And metal oxide semiconductor has the good quick characteristic of phosgene (refractive index that is film changes with extraneous atmosphere), as SnO
2Behind the contact reducibility gas, light transmission changes with ambient gas character and concentration, and the selectivity by doping metals atom, rare earth oxide enhancing sense film can realize the detection to specific gas and concentration, can adapt to various application scenario.Adopt sol-gel technique, with the metal oxide semiconductor thin film coated in the fiber grating cladding surface, not only can obtain the sensitivity of good optical air-sensitive, simultaneously, the modification of material, doping, the compound performance that can further improve air-sensitive film, thereby select this material to make sensitive thin film, have important universal significance.
The skew of long period fiber grating fibre core transmission spectrum loss peak centre wavelength, closely related with air-sensitive film optical parametric (refractive index and thickness) and fiber grating parameter (grating cycle, the amount of selling off, grating length).Select suitable rete optical parametric, can make the type sensing head to the Measurement Resolution of thin-film refractive index up to 10
-8Therefore, need a kind of novel thin film air-sensitive sensing head manufacture method.Use the sensing head of this method manufacturing, detected gas is had very high sensitivity,, be expected in the photochemistry sensing head, be widely used because it has concentrated the advantage of film-sensing head and optical fiber grating sensing head.
Summary of the invention
But the present invention is the manufacture method that the highly sensitive sol-gel film air-sensitive sensing head of a kind of miniaturization, high integrated remote measurement will be provided, use the sensing head of this method manufacturing, detected gas is had very high sensitivity, can be to the Measurement Resolution of thin-film refractive index up to 10
-8, it has concentrated the advantage of film-sensing head and optical fiber grating structure, can extensively use in the photochemistry sensing head.
Making step of the present invention and method are as follows:
1. selection fiber grating: selection cycle 100 μ m-400 μ m, the amount of selling off are 10
-4-10
-3, length is the fiber grating of 1cm-5cm;
2. determine fiber grating covering coating thickness, a. calculates the transmissivity T of setted wavelength fiber grating; B. describe to be defined as gradient and the sensing rete refractive index n of transmissivity T
3The refractive index sensitivity S of ratio absolute value of gradient
nAnd the diagram of block between Film Optics parameter refractive index and the thickness; C. make the sensitivity S of diagram of block
nLevel line is determined symbol S
nBe higher than 10
4The refractive index of the air-sensitive film of filming and the thickness range of film, choose thickness according to the refractive index of institute's coated film;
3. the fiber grating covering is filmed, and concrete grammar is: the fiber grating of strip of paper used for sealing is removed in a. ultrasonic cleaning, and cleaning fluid is followed successively by hydrochloric acid, sodium hydroxide solution and absolute ethyl alcohol; After cleaning end, use deionized water rinsing, place baking oven to dry; B. the preparing metal alkoxide solution places the flask of sealing, carries out the electric power stirring and reflux ageing under constant room temperature at last, the coating solution of acquisition homogeneous transparent under constant temperature; The fiber grating that c. will clean immerses and adopts czochralski method to prepare the colloidal sol-gel film coating liquid, and at the uniform velocity the vertical-lift fiber grating makes the fiber grating covering adsorb one deck colloidal sol outward, forms one deck liquid film, obtains gel mould through evaporation;
4. prepare the porous air-sensitive film, heat-treat through the fiber grating of filming above-mentioned, preparation porous air-sensitive film, concrete grammar is: the quartz ampoule that the fiber grating of filming is placed a sealing, put into tube type high-temperature furnace again and heat, heat up, insulation, slowly reduce to room temperature again, obtain to have porous structure, uniform sol gel air-sensitive film;
5. sensor head construction utilizes above-mentioned film coating optical fibre grating, adopts small tapered index lens, and promptly GRIN Lens keeps two GRIN Lens separated by a distance, is fixed on behind the collimation on the aluminum strip, constitutes sensing head.
The beneficial effect that the present invention is compared with prior art had is: colloidal sol-gel film is owing to its porosity height, and corresponding specific surface area is also very big, and susceptibility and responsiveness height to gas are particularly suitable for doing gas sensitive.When the LPG sensing head that will be coated with the metal oxide semiconductor film is exposed in the extraneous gas, the semiconductor surface energy state will change, and cause the minor alteration of thin-film refractive index, and then cause the obvious skew of transmission peaks.
Photochemistry film-sensing head is compared with the block sensing head of traditional electricity type, has anti-electromagnetic interference (EMI), dynamic range is big, highly sensitive, response is fast advantage; Do not electrically contact owing to have, it is particularly suitable for detecting inflammable, explosive gas.Particularly at petrochemical system, mine, occasions such as large power plant: need to detect oxygen, hydrocarbon, gases such as carbon monoxide adopt electric class sensing head not only not reach permissible accuracy, more seriously can cause security incident.And the chemical optical fibre film-sensing head that combines with optical fiber technology, it is good to have electrical insulation capability, transport information capacity is big, energy loss is low, good in anti-interference performance, and environmental suitability is strong, high temperature resistant, anticorrosion, in light weight, softness is good, can be along path transmitting optical signal, the low cost and other advantages of bending.
Therefore this sensing head that both are combined has excellent performance, can realize remote remote measurement, online in real time monitoring, and can make the high miniaturized device of the ratio of performance to price.This sensing head has been concentrated the advantage of film-sensing head and optical fiber sensor head, is expected to become the high sensitivity photochemistry sensing head of a new generation.
Description of drawings
Fig. 1 is film refractive index, the thickness scope of the sensitivity level line correspondence of drawing in the embodiment of the invention;
Fig. 2 is fiber grating CH
4Gas sensing head detection system figure.
Embodiment
The invention will be further described below in conjunction with drawings and Examples.
A kind of sol-gel film air-sensitive sensing head manufacture method of the present invention, making step and method that it is concrete are:
1. selection fiber grating
Selection cycle 100 μ m-400 μ m, the amount of selling off are 10
-4-10
-3, length is the fiber grating of 1cm-5cm, have make easily, characteristics that physical strength is high.
2. determine fiber grating covering coating thickness
According to triple clad (covering, thin layer and air layer) fiber grating model, set up the secular equation and the coupling mode equations of fiber grating sandwich layer mould, cladding mode.Given optical wavelength respectively by the secular equation of core mode and cladding mode, is tried to achieve the effective refractive index n of sandwich layer, cladding mode
Eff Co, n
Eff ClAfter, further try to achieve the coupling constant k between sandwich layer-sandwich layer, the sandwich layer-cladding mode
1v-11 Co-coAnd k
1v-11 Cl-co, substitution coupling mode equations is then found the solution the partial differential equation of given boundary condition, obtains the amplitude of core in fiber grating incident, outgoing place
With
, both square ratio be the transmissivity T of setted wavelength.
According to the aforementioned calculation method, depict the gradient and the sensing rete refractive index n that are defined as transmissivity T
3The refractive index sensitivity S of ratio absolute value of gradient
nAnd the diagram of block between Film Optics parameter refractive index and the thickness.
Above-mentioned diagram of block is made sensitivity S
nLevel line, can determine to meet and highly sensitively (choose S usually
nBe higher than 10
4) require the refractive index of the air-sensitive film of filming and the thickness range of film, choose thickness according to the refractive index of institute's coated film.
3. the fiber grating covering is filmed
A. the fiber grating of having removed strip of paper used for sealing is carried out ultrasonic cleaning, cleaning fluid is followed successively by certain density hydrochloric acid, sodium hydroxide solution and absolute ethyl alcohol.After cleaning end, use deionized water rinsing again, place baking oven to dry.
B. by certain molar concentration rate, the preparing metal alkoxide solution places the flask of sealing, carries out electric power and stir and reflux under constant temperature, and ageing reasonable time under constant room temperature at last obtains the coating solution of homogeneous transparent.
C. will immerse through the good fiber grating of cleaning, drying adopts czochralski method to prepare the sol gel film coating liquid, promote equably with certain speed, the fiber grating covering that relative motion is adsorbing one deck colloidal sol outward, forms one deck liquid film, and liquid film obtains gel mould through solvent and evaporation of water.
By the viscosity and the rate of pulling of control colloidal sol, can obtain the film of different-thickness.If need obtain thick film, then adopt the mode that repeatedly lifts.Between adjacent film for twice, need the oven dry of last time filming is handled.
4. heat-treat through the fiber grating of filming above-mentioned, preparation porous air-sensitive film, concrete grammar is: the fiber grating of filming is placed the quartz ampoule of a sealing, put into tube type high-temperature furnace again and heat.Control certain temperature rise rate, reach certain temperature after, the insulation appropriate time again with certain rate of temperature fall, is slowly reduced to room temperature.After heat treatment, can obtain to have porous structure, uniform sol gel air-sensitive film.
5. sensor head construction
Utilize above-mentioned film coating optical fibre grating, adopt small tapered index lens, promptly GRIN Lens keeps two GRIN Lens separated by a distance, is fixed on behind the collimation on the aluminum strip, constitutes sensing head.This structure has not only overcome problems such as temperature stability, anti-seismic performance be not good, because GRIN Lens matches with optical fiber, and Transmission Fibers and the directly welding of lens tail optical fiber have improved the stability that is coupled greatly simultaneously.
One of specific embodiments of the invention are:
1. the making of sensing head
(1) selects to sell off rate σ=2 * 10
-4, periods lambda=450 μ m, the fiber grating of length L=1.8cm;
(2) three-dimensional plot of drafting sensitivity and film refractive index, thickness, making sensitivity is 10
4Level line as follows, thereby in can be from Fig. 1 given zone, the film refractive index of selection and thickness.
(3) ethanolic solution of preparation stannous chloride and silicon dioxide colloid mixture.Electric power stirs and refluxed 2 hours under 80 ℃ of constant temperature, and ageing 24 hours under 30 ℃ of constant temperature again obtains the coating solution of homogeneous transparent.
(4) lift thin films, the rate of pulling is 12cm/min.Lift once more after the oven dry, after 5 times, become gel mould repeatedly through drying.Insert in the high temperature furnace, be incubated 30 minutes down, reduce to room temperature again, obtain heat treated film sample at 450 ℃.Through compare test, film refractive index, thickness in the drawings (1.54,635nm) near zone.
(5) utilize assembling sensing heads such as above-mentioned film coating optical fibre grating and GRIN Lens.
2. sensing head implementation
With fiber grating methane gas sensing head is example, illustrates that novel sensing head detects methane gas in mine.
The detection system structure as shown in Figure 2, the InGaAsP LED of 1.5 μ m is as detection light source.In order to carry out synchronous detection, LED by dutycycle be 50%, repetition frequency is the current impulse modulation of 110Hz, the input of modulating pulse simultaneously lock-in amplifier, lock-in amplifier amplifies the signal that comes from photodetector.Photodetector adopts the InGaAs PIN diode, and its wavelength coverage is 1～1.7 μ m, is suitable for the detection of 1.5 mum wavelength light.Make device constant temperature with attemperating unit, to eliminate the influence that light source and environmental temperature fluctuation are brought.
Sensing head is placed the air chamber of making by copper pipe.Air chamber has air intake opening, gas outlet and gauge outfit interface.Air intake opening is by the gas flow of noticeable degree notes people air chamber, and the gas outlet is connected to vacuum pump, and air chamber is vacuumized.Air chamber keeps constant temperature by attemperating unit.
When containing CH
4Gas when the air chamber, the centre wavelength of the attenuation peak of transmission spectrum will be drifted about, marked change also takes place near the transmitance of former centre wavelength simultaneously, the harmonic peak light signal enters photodetector, the size of detectable its light intensity, intensity variations is with CH
4Gas concentration increase and increase.The difference of intensity by relatively with vacuum the time, through differential ratio after, signal is delivered to warning circuit.In case CH
4Gas concentration exceeds the limiting concentration of permission, then triggers and reports to the police.
Claims (1)
1. sol-gel film air-sensitive sensing head manufacture method is characterized in that its method step is:
1) select fiber grating: selection cycle 100 μ m-400 μ m, the amount of selling off are 10
-4-10
-3, length is the fiber grating of 1cm-5cm;
2) determine fiber grating covering coating thickness, its concrete grammar is: a. calculates the transmissivity T of setted wavelength fiber grating; B. describe to be defined as gradient and the sensing rete refractive index n of transmissivity T
3The refractive index sensitivity S of ratio absolute value of gradient
nAnd the diagram of block between Film Optics parameter refractive index and the thickness; C. make the sensitivity S of diagram of block
nLevel line determines to meet S
nBe higher than 10
4The refractive index of the air-sensitive film of filming and the thickness range of film, choose thickness according to the refractive index of institute's coated film;
3) the fiber grating covering is filmed, and its concrete grammar is: the fiber grating of strip of paper used for sealing is removed in a. ultrasonic cleaning, and cleaning fluid is followed successively by hydrochloric acid, sodium hydroxide solution and absolute ethyl alcohol; After cleaning end, use deionized water rinsing, place baking oven to dry; B. the preparing metal alkoxide solution places the flask of sealing, carries out the electric power stirring and reflux ageing under constant room temperature at last, the coating solution of acquisition homogeneous transparent under constant temperature; The fiber grating that c. will clean immerses the so-gel film coating liquid that adopts the czochralski method preparation, and at the uniform velocity the vertical-lift fiber grating makes the fiber grating covering adsorb one deck colloidal sol outward, forms one deck liquid film, obtains gel mould through evaporation;
4) heat-treat through the fiber grating of filming above-mentioned, preparation porous air-sensitive film, concrete grammar is: the quartz ampoule that the fiber grating of filming is placed a sealing, putting into tube type high-temperature furnace again heats, heat up, room temperature is slowly reduced in insulation again, obtains to have porous structure, uniform sol gel air-sensitive film.
5) sensor head construction utilizes above-mentioned film coating optical fibre grating, adopts small tapered index lens, and promptly GRIN Lens keeps two GRIN Lens separated by a distance, is fixed on behind the collimation on the aluminum strip, constitutes sensing head.
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| CN101813654A (en) * | 2010-05-07 | 2010-08-25 | 上海交通大学 | Method for preparing ethanol sensitive material with fine graded porous structure |
| CN101871885A (en) * | 2010-06-08 | 2010-10-27 | 中国计量学院 | Manufacture method of tilted fiber grating hydrogen sensor based on optical catalytic oxidation |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2124473U (en) * | 1992-06-05 | 1992-12-09 | 机械电子工业部第二十三研究所 | Optical fibre type co detecting and alarm device |
| CN1391097A (en) * | 2002-02-08 | 2003-01-15 | 武汉理工大学 | Gas sensitive method and device for testing optical fibre |
| US20040173004A1 (en) * | 2003-03-05 | 2004-09-09 | Eblen John P. | Robust palladium based hydrogen sensor |
-
2005
- 2005-04-28 CN CNB2005100254988A patent/CN100414289C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2124473U (en) * | 1992-06-05 | 1992-12-09 | 机械电子工业部第二十三研究所 | Optical fibre type co detecting and alarm device |
| CN1391097A (en) * | 2002-02-08 | 2003-01-15 | 武汉理工大学 | Gas sensitive method and device for testing optical fibre |
| US20040173004A1 (en) * | 2003-03-05 | 2004-09-09 | Eblen John P. | Robust palladium based hydrogen sensor |
Non-Patent Citations (4)
| Title |
|---|
| Optical fiber long-period gratings withLangmuir-Blodgett thin-film overlays. Nicholas D. Ree, Stephen W. James, Ralph P. Tatam.OPTICS LETTERS,Vol.27 No.9. 2002 |
| Optical fiber long-period gratings withLangmuir-Blodgett thin-film overlays. Nicholas D. Ree, Stephen W. James, Ralph P. Tatam.OPTICS LETTERS,Vol.27 No.9. 2002 * |
| 关于镀有LB膜长周期光纤光栅的谐振波长的研究. 叶梅，冯仙群，叶虎年.应用光学，第25卷第5期. 2004 |
| 关于镀有LB膜长周期光纤光栅的谐振波长的研究. 叶梅，冯仙群，叶虎年.应用光学，第25卷第5期. 2004 * |
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