CN101419161A - Gas detecting method and gas sensor based on plane annular micro-cavity - Google Patents
Gas detecting method and gas sensor based on plane annular micro-cavity Download PDFInfo
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- CN101419161A CN101419161A CNA2008100796580A CN200810079658A CN101419161A CN 101419161 A CN101419161 A CN 101419161A CN A2008100796580 A CNA2008100796580 A CN A2008100796580A CN 200810079658 A CN200810079658 A CN 200810079658A CN 101419161 A CN101419161 A CN 101419161A
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Abstract
The invention relates to a gas detection method and a gas sensor based on planar annular microcavities. The method is mainly characterized in that two couplers consisting of the planar annular microcavities and biconical optical fibers are adopted, one is a gas detection coupler, and the other is a coupler in a vacuum environment. The gas detection method comprises the following steps: based on a principle that the absorption effect of evanescent wave on different gases changes the peak value of a transmitted spectrum, a transmitted spectrum of the gas detection coupler of gas to be detected and a transmitted spectrum of the coupler in the vacuum environment are utilized to contrast; and the detection of the variety and the concentration of the gas to be detected is realized through spectral changes of the transmitted spectrums. The gas sensor designed by the method has the advantages of short response time, relatively simple structure, extremely high sensitivity to virulent harmful gas with extremely low concentration and so on.
Description
One, technical field
The invention belongs to the method sensor of optical signal detecting gas, be based on the gas detection method and the gas sensor of plane annular micro-cavity specifically.
Two, background technology
Along with the development of development and progress of industry, particularly oil, coal, auto industry and the chemical industry of society, gaseous species, the quantity of discharging in life, industry are all increasing.Therefore, the detection to gas concentration and kind has great significance in producing, living.As the detection of colliery, mine to gas; Chemical workshops etc. are to the detection of harmful chemical gas; Test of indoor decoration harmful gas or the like.The gas of especially harmful severe toxicity, content very little in the air will cause huge injury even life-threatening to the person.For example: arsenic hydride is a kind of hypertoxic gas, and its concentration reaches 0.5 milligram hour in every cubic metres of air, will cause acute poisoning.Www.xinhuanet.com's Guizhou channel daily paper in July 7 is the hydrogen arsenide poisoning incident together: produce the little electrolytic zinc plant that the zinc amount has only several kilotons per year for one, and workman's PI surplus priority has 20 in the week age, wherein 3 people are dead because of all rescue measures proved ineffectual.Therefore, make highly sensitive gas sensor, particularly the sensor at harmful gas has great significance.
Gas detection method and sensor are divided into optical detection, semiconductor detection, solid electrolytic detection, Electrochemical Detection or the like.That optical detection has been compared with other several types is highly sensitive, response speed is fast, anti-tampering performance advantages of higher.The most important class of optical gas sensor is exactly the absorbing light spectral pattern.This type of sensor is based on famous " Bill-lambert " theorem, and gas concentration can be tried to achieve from the variable quantity that the discrepancy of light is exported.The medium more options ordinary optic fibre of sensing, special optical fiber or the like.For example: Chinese patent application a kind of gas concentration sensor that adopts nano micropore structure capable optical fiber that number has been 200410037099 patent disclosure, " be respectively equipped with glass optical fiber and nano optical fibers; one tunnel process lens enter glass optical fiber; another road light enters nano optical fibers through lens, and the other end of two optical fiber connects detector respectively." " optical fiber of the nano micropore structure capable that is adopted be a kind of inside be covered with nano level together with or the part together with micropore, can transmit light "; Chinese patent application a kind of fiber gas sensor that number has been 200510012344.5 patent disclosure, feature is " optical fiber in the described gas absorption cell and contrast optical fiber are the hollow light of microstructure "; Chinese patent application number is a kind of hollow photon crystal fiber gas sensor that discloses of 200610012988.9, and feature is " the leaded light air chamber adopts the hollow photon crystal optical fiber that has the ventilative micropore of micron order size on it ".
The detection of gas principle of the sensor all is based on the detection principle of direct absorption, has simple in structurely, is convenient to advantages of application.Difference is exactly to have adopted different absorbing mediums.Wayward absorption light path in the process of " Bill-lambert " theorem derivation gas concentration, when gas concentration to be measured was very low, this detection method is measure gas concentrations fast and accurately just.Therefore its detection is subjected to the restriction of gas concentration to be measured.The harmful hypertoxic gas of extremely low concentration then needs low concentration, high sensitivity, response fast.Therefore how extremely low concentration gas is detected the key that becomes detection by effective means.
Three, summary of the invention
The objective of the invention is on the basis that overcomes above-mentioned gas sensor deficiency, and design with provide that a kind of sensitivity is high, the response time is short, structure is relative simple, except that at the common harmful gas, the gas detection method and the gas sensor based on plane annular micro-cavity of high sensitivity arranged also for the extremely low hypertoxic harmful gas of concentration.
The present invention adopts following technical scheme to realize:
Gas detection method based on plane annular micro-cavity is characterized in that: the coupling mechanism that adopts two plane annular micro-cavities and biconical fiber to constitute, and one is the detected gas coupling mechanism, another is a coupling mechanism in the vacuum environment; This gas detection method is based on evanescent wave has changed the transmitted spectrum peak value to the absorption of gas with various principle, utilize that coupling mechanism institute transmitted spectrum compares in detected gas coupling mechanism institute's transmitted spectrum of gas to be detected and the vacuum environment, and realize detecting the kind and the concentration of gas to be measured by the two spectrum change.
Based on the gas detection sensor of plane annular micro-cavity, comprise optical fiber, generating laser, optical filter, beam splitter, absorption air chamber, vacuum room, photodetector and signal processor; It is characterized in that:
● described optical fiber is double-tapered fiber; A coupling mechanism that is made of plane annular micro-cavity and double-tapered fiber is respectively arranged in described absorption air chamber and the vacuum room, and the plane annular micro-cavity of coupling mechanism is positioned at the awl district of described double-tapered fiber; Coupling mechanism in the described absorption air chamber is the detected gas coupling mechanism, and the coupling mechanism in the vacuum room is a coupling mechanism in the vacuum environment;
● described absorption air chamber is made up of detected gas coupling mechanism and dustproof ventilating cover;
● described vacuum room is made up of coupling mechanism in the vacuum environment and vacuum (-tight) housing;
● described generating laser connects optical filter, connect the input end of beam splitter then, the output terminal of beam splitter is by single-mode fiber, and one the tunnel connects the double-tapered fiber input end of gas absorption chamber, the double-tapered fiber input end of the vacuum room that other one tunnel connection contrast signal is used; Absorb air chamber and be connected two photodetectors respectively by single-mode fiber, light signal is converted to electric signal and receives signal processing unit by two detectors with the double-tapered fiber output terminal of vacuum room.
The present invention has following advantage compared with the prior art:
1. the structure that adopts plane annular micro-cavity and double-tapered fiber coupling mechanism can realize highly sensitive probe gas as the core technology that detects.
2. the coupling process of coupling mechanism is to finish by the evanescent wave of surface both, thereby realizes detecting in real time, has saved the diffusion time of fiber gas sensor gas in the past, has improved response speed.
3. extensibility is strong, changes plane annular micro-cavity (mainly being diameter parameters) and light source at the test gas environment.Under particular surroundings, this sensor network can be set, thereby hold the CONCENTRATION DISTRIBUTION state of gas in detail.
Four, description of drawings
Fig. 1 and Fig. 2 are the structural representation of the present invention of two kinds of forms;
Fig. 3 is system and device figure of the present invention.
Among the figure: plane annular micro-cavity 1; Double-tapered fiber 2; Dustproof ventilating cover 3; Generating laser 4; Optical filter 5; Beam splitter 6; Absorb air chamber 7; Vacuum room 8; Photodetector 9; Signal processing circuit 10; Single-mode fiber 11.
Five, embodiment
Describe embodiments of the invention in detail below in conjunction with accompanying drawing.
The present invention is based on the gas sensor of plane annular micro-cavity and conical fiber structure, comprise optical fiber, generating laser 4, optical filter 5, beam splitter 6, absorb air chamber 7, vacuum room 8, photodetector 9 and signal processor 10;
● described optical fiber is double-tapered fiber; A coupling mechanism that is made of plane annular micro-cavity and double-tapered fiber is respectively arranged in described absorption air chamber and the vacuum room, and the plane annular micro-cavity of coupling mechanism is positioned at the awl district of described double-tapered fiber, as depicted in figs. 1 and 2.Coupling mechanism in the described absorption air chamber is the detected gas coupling mechanism, and the coupling mechanism in the vacuum room (8) is a coupling mechanism in the vacuum environment.
● described absorption air chamber is made up of detected gas coupling mechanism and dustproof ventilating cover.
● described vacuum room is made up of coupling mechanism in the vacuum environment and vacuum (-tight) housing.
● described generating laser connects optical filter, connect the input end of beam splitter then, the output terminal of beam splitter passes through the double-tapered fiber input end that single-mode fiber 11, a tunnel connects gas absorption chamber, the double-tapered fiber input end of the vacuum room that other one tunnel connection contrast signal is used; Absorb air chamber and be connected two photodetectors respectively by single-mode fiber, by two detectors light signal is converted to electric signal and receives signal processing unit, as shown in Figure 3 with the double-tapered fiber output terminal of vacuum room.
Core technology of the present invention is the coupling mechanism that constitutes with plane annular micro-cavity 1 and double-tapered fiber 2, and plane annular micro-cavity is positioned at the awl district of double-tapered fiber, and the two ends of double-tapered fiber connect the general single mode fiber of gas absorption chamber respectively.Be connected by optical fiber matching device (ring flange) between generating laser and optical fiber.Described double-tapered fiber can be used nano optical fibers, or photonic crystal fiber, or the coupling conical fiber etc., plane annular micro-cavity can be designed as the disk microcavity, as shown in Figure 1.Or be designed to the racetrack microcavity, as shown in Figure 2.
Described plane annular micro-cavity 1 utilizes modern MEMS process technology to form, and material is SiO
2, diameter is 60～200 μ m, is shaped as plane annular.The material of described double-tapered fiber 2 is SiO
2, utilize the oxyhydrogen flame machine, adopt molten daraf(reciprocal of farad) to make.The characteristics of the optical taper that molten daraf(reciprocal of farad) is made be the diameter of the covering of optical fiber and fibre core along fiber axis to all being tapered, can think generally that in whole awl district it is constant that the diameter ratio of covering and fibre core keeps.The tapered zone length of described double-tapered fiber is 200 μ m, and the most advanced and sophisticated fiber core radius of used conical fiber is 1 μ m, and cladding radius is 2.5 μ m, and cone angle is 11 when spending, and coupling efficiency is about 86%.The coupling mechanism of measure-alike plane annular micro-cavity 1 and double-tapered fiber 2 structures all is housed in described absorption air chamber 7 and the vacuum room 8.Both differences are to absorb the air chamber 7 outer ventilating covers 3 that prevent dust that are surrounded by, and allow test environment gas fully contact with coupling mechanism, and vacuum room 8 are vacuum environments of a sealing, and vacuum room 8 provides contrast signal for the coupling mechanism detection that is in the gas absorption cell.
Principle of work of the present invention
Plane annular micro-cavity is because its its specific structure and surface smoothness have the quality factor (10 of superelevation
8).When light transmits in conical fiber, because the existence of evanescent wave, and plane annular micro-cavity and conical fiber are with very little distance (0 μ m-2 μ m), when transmitting near plane annular micro-cavity, have optically-coupled and enter plane annular micro-cavity continuation propagation, and in plane annular micro-cavity, form resonance, be coupled into conical fiber by evanescent wave once more afterwards and transmit out.Because plane annular micro-cavity is responsive to auroral poles, the subtle change of incident light also can make the resonance peak of transmitted spectrum produce significant change.Therefore coupled structure is placed in the air chamber (perhaps gas absorption cell), when incident light passes through conical fiber, form with evanescent wave is coupled into plane annular micro-cavity, during through the fine pitch between conical fiber and the plane annular micro-cavity, because the gas in the test environment is different with vacuum, the kind of gas all can be carried out different absorptions by evanescent wave with concentration, thereby can influence the incident light that is coupled into plane annular micro-cavity, finally influences the resonance peak of transmitted spectrum.By with the contrast of vacuum room's transmitted spectrum resonance peak, can obtain the kind and the concentration of gas to be measured in the test environment.
When a beam intensity is I
0, wavelength is that the monochromatic light of λ incides in the air chamber, absorbs line or absorption band if the sample in the air chamber has at the λ place, and light can be decayed during by air chamber, and according to Beer-Lambert law, air chamber outgoing light intensity is:
I(λ)＝I
0(λ)exp(-αCl)
In the formula: I
0Be that wavelength is the light intensity of monochromatic light before entering air chamber of λ (λ); I (λ) is the light intensity of air chamber emergent light; C is the concentration of tested gas; α is the absorption coefficient of gas; L is the length (action length of light and gas) of air chamber.
Simultaneously, conical fiber has good coupling because of its special construction that has to light.
The job operation of common conical fiber has chemical corrosion method, polishing and molten daraf(reciprocal of farad).Conical fiber geometry and its transport property have following relation:
Wherein: l is a light cone length, and α is the light cone tapering, and a is the butt end radius of optical taper, and b is a tip radius.As seen under the situation that other parameters have been set, tip diameter is big more, and α is big more; The conical transition zone of optical fiber is short more, and promptly the more little relative cone angle of l value is just big more, and taper changes also just sharp-pointed more.
When placing this sensor after a certain specific environment, because gas absorption chamber 7 shells are dustproof ventilating covers 3, so the very fast whole air chamber (the air chamber gas concentration is identical with environmental gas concentration) that just can be full of uniformly of environmental gas.At this moment, open generating laser 4, regulate light source and make light source send the resonant condition that laser satisfies gas absorption chamber and vacuum room's midplane annular micro-cavity.Because coupling mechanism is to be made of plane annular micro-cavity 1 and conical fiber 2, when light wave satisfies the resonant condition of plane annular micro-cavity 1 in the conical fiber 2, propagate into plane annular micro-cavity 1 with the form of evanescent wave with regard to having a large amount of light waves.Wherein, evanescent wave is the ripple that propagate in a kind of near field.Therefore with in interior, coupling is just taken place the distance of having only plane annular micro-cavity fine 1 and taper light 2 at several microns.And the transmitted spectrum after the coupling very easily is affected.When having pair coupled wavelength to have the gas of absorption peak in the environment, obvious variation just takes place with the transmitted spectrum that is in the coupled structure 4 of vacuum room 8 in coupled structure in the gas absorption chamber 7.The gas of variable concentrations is to the difference that influences of coupled structure.Photodetector 9 is delivered to signal processing unit 10 by accepting different detectable signals, thereby finishes detection of gas.
Claims (5)
1, based on the gas detection method of plane annular micro-cavity, it is characterized in that: the coupling mechanism that adopts two plane annular micro-cavities (1) and biconical fiber (2) to constitute, one is the detected gas coupling mechanism, another is a coupling mechanism in the vacuum environment; This gas detection method is based on evanescent wave has changed the transmitted spectrum peak value to the absorption of gas with various principle, utilize that coupling mechanism institute transmitted spectrum compares in detected gas coupling mechanism institute's transmitted spectrum of gas to be detected and the vacuum environment, and realize detecting the kind and the concentration of gas to be measured by the two spectrum change.
2,, comprise optical fiber (2), generating laser (4), optical filter (5), beam splitter (6), absorb air chamber (7), vacuum room (8), photodetector (9) and signal processor (10) based on the gas detection sensor of plane annular micro-cavity; It is characterized in that:
● described optical fiber is double-tapered fiber; A coupling mechanism that is made of plane annular micro-cavity and double-tapered fiber is respectively arranged in described absorption air chamber and the vacuum room, and the plane annular micro-cavity of coupling mechanism is positioned at the awl district of described double-tapered fiber; Coupling mechanism in the described absorption air chamber is the detected gas coupling mechanism, and the coupling mechanism in the vacuum room is a coupling mechanism in the vacuum environment;
● described absorption air chamber is made up of detected gas coupling mechanism and dustproof ventilating cover (3);
● described vacuum room is made up of coupling mechanism in the vacuum environment and vacuum (-tight) housing;
● described generating laser connects optical filter, connect the input end of beam splitter then, the output terminal of beam splitter is by single-mode fiber (11), and one the tunnel connects the double-tapered fiber input end of gas absorption chamber, the double-tapered fiber input end of the vacuum room that other one tunnel connection contrast signal is used; Absorb air chamber and be connected two photodetectors respectively by single-mode fiber, light signal is converted to electric signal and receives unit, signal place by two detectors with the double-tapered fiber output terminal of vacuum room.
3, the gas detection sensor based on plane annular micro-cavity according to claim 2 is characterized in that: described double-tapered fiber is a nano optical fibers, perhaps is photonic crystal fiber.
4, the gas detection sensor based on plane annular micro-cavity according to claim 2 is characterized in that: described plane annular micro-cavity is the collar plate shape microcavity, perhaps is the racetrack microcavity.
5, the gas detection sensor based on plane annular micro-cavity according to claim 2 is characterized in that: the spacing of described coupling mechanism midplane annular micro-cavity and double-tapered fiber is 0～2um.
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| CN102023029A (en) * | 2010-11-22 | 2011-04-20 | 北京理工大学 | Miniature high-sensitivity optical fiber chemical sensor |
| CN101923052B (en) * | 2009-06-17 | 2011-12-07 | 中国科学院微电子研究所 | Infrared spectrum type MEMS gas sensor based on filter structure light splitting |
| CN104502314A (en) * | 2014-12-18 | 2015-04-08 | 杭州香侬科技有限公司 | Biochemical sensor for coupling optical microcavity molecule |
| CN104795720A (en) * | 2015-04-28 | 2015-07-22 | 杭州电子科技大学 | Beam conversion device based on optical micro-cavity regulation |
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| CN102023029A (en) * | 2010-11-22 | 2011-04-20 | 北京理工大学 | Miniature high-sensitivity optical fiber chemical sensor |
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| CN104502314A (en) * | 2014-12-18 | 2015-04-08 | 杭州香侬科技有限公司 | Biochemical sensor for coupling optical microcavity molecule |
| CN104795720A (en) * | 2015-04-28 | 2015-07-22 | 杭州电子科技大学 | Beam conversion device based on optical micro-cavity regulation |
| CN104795720B (en) * | 2015-04-28 | 2018-04-27 | 杭州电子科技大学 | A kind of beam switching device based on optical microcavity regulation and control |
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| CN110068533A (en) * | 2019-05-05 | 2019-07-30 | 中北大学 | A kind of sensor based on high Q optical microcavity evanscent field |
| CN111077080A (en) * | 2020-01-16 | 2020-04-28 | 华南师范大学 | Optical fiber Mach-Zehnder interference humidity sensor based on graphene oxide sensitization |
| CN112525858A (en) * | 2020-11-27 | 2021-03-19 | 中红外激光研究院(江苏)有限公司 | Gas sensor based on microcavity thermotropic ringing effect and gas concentration measuring method |
| CN113466994A (en) * | 2021-07-13 | 2021-10-01 | 中北大学 | Novel optical fiber coupler |
| CN113466994B (en) * | 2021-07-13 | 2022-07-05 | 中北大学 | Novel optical fiber coupler |
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