CN110319940A - The laser fiber interferometer diagnostic system of high-density plasma density measure - Google Patents
The laser fiber interferometer diagnostic system of high-density plasma density measure Download PDFInfo
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- CN110319940A CN110319940A CN201910730360.XA CN201910730360A CN110319940A CN 110319940 A CN110319940 A CN 110319940A CN 201910730360 A CN201910730360 A CN 201910730360A CN 110319940 A CN110319940 A CN 110319940A
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- 239000000835 fiber Substances 0.000 title claims abstract description 77
- 239000013307 optical fiber Substances 0.000 claims abstract description 15
- 230000003287 optical effect Effects 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- 230000001427 coherent effect Effects 0.000 claims description 10
- 238000012545 processing Methods 0.000 claims description 8
- 230000008878 coupling Effects 0.000 claims description 4
- 238000010168 coupling process Methods 0.000 claims description 4
- 238000005859 coupling reaction Methods 0.000 claims description 4
- 230000005622 photoelectricity Effects 0.000 claims description 4
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 15
- 238000005259 measurement Methods 0.000 abstract description 9
- 230000008569 process Effects 0.000 abstract description 6
- 238000010586 diagram Methods 0.000 description 7
- 238000001514 detection method Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 238000003745 diagnosis Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005305 interferometry Methods 0.000 description 2
- 241000931526 Acer campestre Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000001739 density measurement Methods 0.000 description 1
- 238000012631 diagnostic technique Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000010358 mechanical oscillation Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000009738 saturating Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/24—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by observing the transmission of wave or particle radiation through the material
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
- G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
- G01J2009/0226—Fibres
- G01J2009/023—Fibres of the integrated optical type
Abstract
The present invention provides a kind of laser fiber interferometer diagnostic systems of high-density plasma density measure, the laser fiber interferometer diagnostic system uses fiber coupler, reduce the use of optical platform and other optical devices in open beam system, and then structure is simple, it is at low cost.Also, the laser fiber interferometer diagnostic system utilizes the flexible and easy extended attribute of optical fiber, and photodetector can be made to be sufficiently apart from heating region to be measured, avoid influence of the electromagnetic interference to measurement of plasma generation process.
Description
Technical field
The present invention relates to plasma density diagnostic techniques fields, more specifically to a kind of high-density plasma
The laser fiber interferometer diagnostic system of density measure.
Background technique
Interferometry is very mature as the method for a kind of " non-invasive " measurement plasma density, interferometry
There are many kinds of types for the interferometer of measurement plasma density, can be roughly divided into two classes: spatial discrimination interferometer and time resolution
Interferometer.
Interferometer currently used for measuring plasma density is typically built for open beam system, i.e., in the system
Coherent light propagate in free space, mainly there are the devices such as reflecting mirror, beam splitter and detector.
But in many situations, the accurate recording that open interferometer plasma density develops is very difficult, special
When not being plasma density amplitude of variation very little, fringes shift is very small, this, which means that, needs interferometer in time scale
Upper highly stable, stable time scale need to be much larger than the time in research, for eliminating ambient noise, such as external support structure
Mechanical oscillation and beam propagation optical path in air-flow interference.In order to eliminate these interference, open beam-interferometer system is needed
It is fixed on the large-scale optical platform for eliminating vibration, or even also needs for optical path to be placed in and completely cut off in the pipeline of surrounding air.
Also, the laser for measuring high-density plasma is located at visible light and near infrared band, traditionally open
Beam-interferometer system using gas laser, if He-Ne laser carries out interference experiment, since laser wavelength broadening is main
Energy level slight change during laser excitation, i.e., closely related with the thermal noise of level system, traditional gas swashs
It is wider that the thermal noise of light device causes greatly the frequency (wavelength) of shoot laser to broaden very much, generally reaches 100MHz or more, Wu Fajin
Row homodyne measures plasma density, carries out to reduce the Fabry-Perot system that laser broadening needs additional increase accurate
Filtering.
In addition, the broadening requirement of laser source can be reduced using the technology that heterodyne method carries out plasma density measurement, but
It is to need to increase the very narrow acousto-optic modulator of frequency bandspread (general modulating frequency is 40MHz-80MHz, and broadening is less than 100Hz),
Reference light and light to be measured enter frequency mixer and are mixed, and carry out phase demodulating, the heterodyne scheme structure using I-Q phase discriminator
Complexity, it is expensive, and then cause the interferometer structure for measuring plasma density complicated and expensive.
Summary of the invention
In view of this, to solve the above problems, the present invention provides a kind of laser light of high-density plasma density measure
Fine interferometer diagnostic system, technical solution are as follows:
A kind of laser fiber interferometer diagnostic system of high-density plasma density measure, the laser fiber interferometer
Diagnostic system includes: laser, the first fiber coupler, attenuator, the first light power meter, the second light power meter, the second optical fiber
Coupler, first to third photodetector and signal processing apparatus；
Wherein, the laser is for exporting coherent laser；
First fiber coupler is used to the coherent laser beam splitting be signal beams and reference beam；
The signal beams are for passing sequentially through heating region, first light power meter and second light to be measured
Fine coupler；
The reference beam is for passing sequentially through the attenuator, second light power meter and second fiber coupling
Device；
Second fiber coupler is used to three road output ends being respectively connected to described first to third photodetector；
The signal processing apparatus is used to parse described first to third photodetector output voltage signal
To obtain the density parameter of the plasma to be measured；
Wherein, by the adjusting attenuator so that the light intensity of the signal beams into second fiber coupler
It is equal with the light intensity of the reference beam.
Preferably, in above-mentioned laser fiber interferometer diagnostic system, the laser is super-narrow line width laser；
The super-narrow line width laser from single mode optical fiber for exporting the coherent laser.
Preferably, in above-mentioned laser fiber interferometer diagnostic system, the line width of the super-narrow line width laser is less than
3kHz。
Preferably, in above-mentioned laser fiber interferometer diagnostic system, first fiber coupler is 2 × 2 optical fiber couplings
Clutch.
Preferably, in above-mentioned laser fiber interferometer diagnostic system, second fiber coupler is 3 × 3 optical fiber couplings
Clutch.
Preferably, in above-mentioned laser fiber interferometer diagnostic system, three road output ends of 3 × 3 fiber coupler
Three-way output signal differ 120 °.
Preferably, in above-mentioned laser fiber interferometer diagnostic system, described first to third photodetector is high speed
The InGaAs photodetector of low noise.
Preferably, in above-mentioned laser fiber interferometer diagnostic system, the laser fiber interferometer diagnostic system is also wrapped
It includes: collimation lens；
Wherein, the signal beams are after collimation lens processing, then pass sequentially through heating region to be measured, institute
State the first light power meter and second fiber coupler.
Compared to the prior art, what the present invention realized has the beneficial effect that
The laser fiber interferometer diagnostic system uses fiber coupler, reduces optical platform in open beam system
And the use of other optical devices, and then structure is simple, it is at low cost.
Also, the laser fiber interferometer diagnostic system utilizes the flexible and easy extended attribute of optical fiber, photoelectricity can be made to visit
It surveys device and is sufficiently apart from heating region to be measured, avoid influence of the electromagnetic interference to measurement of plasma generation process.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
The embodiment of invention for those of ordinary skill in the art without creative efforts, can also basis
The attached drawing of offer obtains other attached drawings.
Fig. 1 is a kind of laser fiber interferometer diagnosis of high-density plasma density measure provided in an embodiment of the present invention
The structural schematic diagram of system；
Fig. 2 is that the embodiment of the present invention provides the original electricity that laser interferometer provides when plasma density to be measured changes
Press signal schematic representation；
Fig. 3 is the phase difference schematic diagram that the embodiment of the present invention is calculated by phase difference formula；
Fig. 4 is the signal contrast schematic diagram of the laser of different line widths provided in an embodiment of the present invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
In order to make the foregoing objectives, features and advantages of the present invention clearer and more comprehensible, with reference to the accompanying drawing and specific real
Applying mode, the present invention is described in further detail.
With reference to Fig. 1, Fig. 1 is that a kind of laser fiber of high-density plasma density measure provided in an embodiment of the present invention is dry
The structural schematic diagram of interferometer diagnostic system.
The laser fiber interferometer diagnostic system includes: laser 11, the first fiber coupler 12, attenuator 13,
One light power meter 14, the second light power meter 15, at the second fiber coupler 16, first to third photodetector 17 and signal
Manage device 18；
Wherein, the laser 11 is for exporting coherent laser；
First fiber coupler 12 is used to the coherent laser beam splitting be signal beams and reference beam；
The signal beams are for passing sequentially through heating region 19 to be measured, first light power meter 14 and described the
Two fiber couplers 16；
The reference beam is for passing sequentially through the attenuator 13, second light power meter 15 and second optical fiber
Coupler 16；
Second fiber coupler 16 is used to three road output ends being respectively connected to described first to third photodetection
Device 17；
The signal processing apparatus 18 is used to carry out described first to third photodetector 17 output voltage signal
It parses to obtain the density parameter of the plasma to be measured；
Wherein, by adjust the attenuator 13 so that into second fiber coupler 16 the signal beams
Light intensity and the light intensity of the reference beam are equal.
In this embodiment, the output voltage signal of the photodetector and the power of light are directly proportional, and three photoelectricity are visited
The power for surveying device turns voltage coefficient can calibrate relative size in advance, pass through the output voltage to first to third photodetector
Signal carries out parsing and obtains interferometer phase difference Δ φ (t), and then obtains the string averag density of the plasma to be measured
Wherein, phase difference chord averag density meets following relationship:
First to output voltage signal P1, P2 and P3 and phase difference of third photodetector meets following relationship:
Wherein, λ is laser wavelength of incidence；
L is that electromagnetic wave penetrates plasma thickness；
reFor electronics classics radius 2.82 × 10-15m。
As shown in Figures 2 and 3, Fig. 2 provides laser when plasma density to be measured changes for the embodiment of the present invention and does
The raw voltage signals schematic diagram that interferometer provides, Fig. 3 are the phase difference that the embodiment of the present invention is calculated by phase difference formula
Schematic diagram, it is suitable with practical structures, that is, show the feasible of laser fiber interferometer diagnostic system measurement plasma density
Property.
Also, the laser fiber interferometer diagnostic system uses fiber coupler, reduces light in open beam system
The use of platform and other optical devices is learned, and then structure is simple, it is at low cost.
And the laser fiber interferometer diagnostic system utilizes the flexible and easy extended attribute of optical fiber, photoelectricity can be made to visit
It surveys device and is sufficiently apart from heating region to be measured, avoid influence of the electromagnetic interference to measurement of plasma generation process.
Further, it is based on the above embodiment of the present invention, the laser is super-narrow line width laser；
The super-narrow line width laser from single mode optical fiber for exporting the coherent laser.
The line width of the super-narrow line width laser is less than 3kHz.
In this embodiment, the optical fiber of optical path connection is all made of single mode optical fiber, and the wavelength of laser is 1550nm,
The loss of optical fiber is minimum under the wavelength, and with open beam system used in 532nm or 652nm laser compared with,
Detectivity is higher.
Also, Fig. 4 is referred to, Fig. 4 is the signal contrast schematic diagram of the laser of different line widths provided in an embodiment of the present invention,
The compare laser of 3MHz line width of super-narrow line width laser of the line width less than 3kHz possesses lower phase noise level, low
One multiple order of magnitude, i.e., possess higher resolution capability for variable density, this is also that the present invention obtains high s/n ratio density signal
Key.
Further, it is based on the above embodiment of the present invention, second fiber coupler is 3 × 3 fiber couplers.
The three-way output signal of three road output ends of 3 × 3 fiber coupler differs 120 °.
In this embodiment, phase difference detection is carried out using 3 × 3 fiber couplers, is the key that one of whole system, this
Invention is measured using homodyne, and traditional interferometer homodyne measurement can not judge variable density direction, therefore in the present invention
The orthogonal output of interference phase difference can be provided using 3 × 3 fiber couplers, it can at any time in section, determine phase difference
It is to increase or reduce, and solve the problems, such as that traditional homodyne measurement is low in zero phase attachment phase-detection precision, provides
Higher phase-detection precision.
Also, optical maser wavelength 1550nm is fallen in the wave-length coverage of photodetector, should because optical power reaches 30mW or more
Photodetector further reduced the complexity of system structure, 3 × 3 fiber couplers are by excellent without increasing enlarging function
Change, can make final minimum measurement density is about 1018m-3。
Further, it is based on the above embodiment of the present invention, first fiber coupler is 2 × 2 fiber couplers.
Further, it is based on the above embodiment of the present invention, described first to third photodetector is high-speed low-noise
InGaAs photodetector.
Further, the above embodiment of the present invention, the laser fiber interferometer diagnostic system are based on further include: collimation is saturating
Mirror；
Wherein, the signal beams are after collimation lens processing, then pass sequentially through heating region to be measured, institute
State the first light power meter and second fiber coupler.
To it, specifically a kind of hardware embodiment is illustrated below:
Wherein, the model UNL-1550-50-FC/APC-B-SM of the laser, line width are less than 3kHz.
Model 1310/1550-BWC-2 × 2 of 2 × 2 fiber coupler.
Model 1550-SSC-3 × 3 of 3 × 3 fiber coupler.
The model VOA of the attenuator.
First light power meter is identical with the model of second light power meter, is PM20CH.
Described first to third photodetector model it is identical, be DET01CFC/M.
The model SMF-28/FC-APC of the optical fiber.
The model PAF2-2C of the collimation lens.
Above to a kind of laser fiber interferometer diagnosis system of high-density plasma density measure provided by the present invention
System is described in detail, and used herein a specific example illustrates the principle and implementation of the invention, above
The explanation of embodiment is merely used to help understand method and its core concept of the invention；Meanwhile for the general skill of this field
Art personnel, according to the thought of the present invention, there will be changes in the specific implementation manner and application range, in conclusion this
Description should not be construed as limiting the invention.
It should be noted that all the embodiments in this specification are described in a progressive manner, each embodiment weight
Point explanation is the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other.
For the device disclosed in the embodiment, since it is corresponded to the methods disclosed in the examples, so being described relatively simple, phase
Place is closed referring to method part illustration.
It should also be noted that, herein, relational terms such as first and second and the like are used merely to one
Entity or operation are distinguished with another entity or operation, without necessarily requiring or implying between these entities or operation
There are any actual relationship or orders.Moreover, the terms "include", "comprise" or its any other variant are intended to contain
Lid non-exclusive inclusion, so that the element that the process, method, article or equipment including a series of elements is intrinsic,
It further include either the element intrinsic for these process, method, article or equipments.In the absence of more restrictions,
The element limited by sentence "including a ...", it is not excluded that in the process, method, article or equipment including the element
In there is also other identical elements.
The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention.
Various modifications to these embodiments will be readily apparent to those skilled in the art, as defined herein
General Principle can be realized in other embodiments without departing from the spirit or scope of the present invention.Therefore, of the invention
It is not intended to be limited to the embodiments shown herein, and is to fit to and the principles and novel features disclosed herein phase one
The widest scope of cause.
Claims (8)
1. a kind of laser fiber interferometer diagnostic system of high-density plasma density measure, which is characterized in that the laser
Fibre optic interferometer diagnostic system includes: laser, the first fiber coupler, attenuator, the first light power meter, the second optical power
Meter, the second fiber coupler, first to third photodetector and signal processing apparatus；
Wherein, the laser is for exporting coherent laser；
First fiber coupler is used to the coherent laser beam splitting be signal beams and reference beam；
The signal beams are for passing sequentially through heating region, first light power meter and the second optical fiber coupling to be measured
Clutch；
The reference beam is for passing sequentially through the attenuator, second light power meter and second fiber coupler；
Second fiber coupler is used to three road output ends being respectively connected to described first to third photodetector；
The signal processing apparatus is used to parse to obtain described first to third photodetector output voltage signal
Obtain the density parameter of the plasma to be measured；
Wherein, by the adjusting attenuator so that light intensity and institute into the signal beams of second fiber coupler
The light intensity for stating reference beam is equal.
2. laser fiber interferometer diagnostic system according to claim 1, which is characterized in that the laser is ultra-narrow line
Wide laser；
The super-narrow line width laser from single mode optical fiber for exporting the coherent laser.
3. laser fiber interferometer diagnostic system according to claim 2, which is characterized in that the super-narrow line width laser
Line width be less than 3kHz.
4. laser fiber interferometer diagnostic system according to claim 1, which is characterized in that first fiber coupler
For 2 × 2 fiber couplers.
5. laser fiber interferometer diagnostic system according to claim 1, which is characterized in that second fiber coupler
For 3 × 3 fiber couplers.
6. laser fiber interferometer diagnostic system according to claim 5, which is characterized in that 3 × 3 fiber coupler
Three road output ends three-way output signal differ 120 °.
7. laser fiber interferometer diagnostic system according to claim 1, which is characterized in that described first to third photoelectricity
Detector is the InGaAs photodetector of high-speed low-noise.
8. laser fiber interferometer diagnostic system according to claim 1, which is characterized in that the laser fiber interferometer
Diagnostic system further include: collimation lens；
Wherein, the signal beams are after collimation lens processing, then pass sequentially through heating region to be measured, described the
One light power meter and second fiber coupler.
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| CN201910730360.XA CN110319940A (en) | 2019-08-08 | 2019-08-08 | The laser fiber interferometer diagnostic system of high-density plasma density measure |
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| CN112013958A (en) * | 2020-07-21 | 2020-12-01 | 西安电子科技大学 | Spectrum measuring method, system, storage medium and high-frequency induction plasma |
| CN113567955A (en) * | 2021-07-07 | 2021-10-29 | 厦门大学 | Water body detection laser radar based on single-cavity double-working-wavelength FPI |
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