CN109682795A - The method and device of thin film damage is differentiated based on the plasma ignition time - Google Patents
The method and device of thin film damage is differentiated based on the plasma ignition time Download PDFInfo
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Abstract
本发明公开了一种基于等离子体点燃时间判别薄膜损伤的方法及装置。解决了等离子体闪光法对薄膜损伤识别的误判问题，技术方案是：用至少三个探测器分别获取空气和薄膜等离子体闪光信号及入射激光信号，以后者为基准，得到空气和薄膜等离子体闪光点燃时间，准确分辨出空气和薄膜等离子体闪光，消除误判。实现步骤是分别采集基准和闪光信号；获取基准和闪光信号起始时刻；以基准和闪光信号起始时刻之差作为闪光点燃时间；建模计算闪光点燃时间；比较并得出损伤识别判据。本发明建立的点燃时间计算模型，可针对任意单层薄膜；装置结构简单，测量精度达0.1ns，能准确进行薄膜损伤识别，可靠性好。本发明应用于强激光作用下的光学薄膜损伤判别。
The invention discloses a method and a device for judging damage of thin films based on plasma ignition time. The problem of misjudgment of thin film damage identification by the plasma flash method is solved, and the technical scheme is as follows: at least three detectors are used to obtain the air and thin film plasma flash signals and incident laser signals respectively, and the latter is used as the benchmark to obtain the air and thin film plasma. Flash ignition time, accurately distinguish air and thin-film plasma flashes, and eliminate misjudgment. The realization steps are to collect the reference and the flash signal respectively; obtain the starting time of the reference and the flash signal; take the difference between the reference and the starting time of the flash signal as the flash ignition time; model and calculate the flash ignition time; compare and obtain the damage identification criterion. The ignition time calculation model established by the invention can be aimed at any single-layer film; the device has a simple structure, the measurement accuracy reaches 0.1 ns, and the film damage can be accurately identified, and the reliability is good. The invention is applied to the damage judgment of optical thin films under the action of strong laser.
Description
Technical field
The invention belongs to technical field of optical test, relate generally to the fault localization of film, it is specifically a kind of based on it is equal from
Daughter burning time differentiates the method and device of thin film damage, for the thin film damage identification under superlaser effect.
Background technique
The optical phenomena of film is just noticed early in the 17th century, after the 1930s, because of vacuum technique
Development provide prerequisite to the preparation of various optical thin films, even to this day, optical thin film has been greatly developed, optics
Seriation, sequencing and specialization are gradually moved towards in the production of film, and still, there are also many problems in the research of optical thin film
Need further to be solved, the existing level of optical thin film is not met by requirement in many work, needs to improve.In theory
On, not only the growth mechanism needs of film are got clear, and the optical theory of film, are especially applied to the optics reason of extremely short wave band
By also needing to be further improved and improve.In technique, people also lack effective means realization to the essence of thin-film deposition parameter
Really control, in this way, the growth of film just has a degree of randomness, the optical constant of film, the thickness of film and thin
The performance of film also just has a degree of unstability and blindness, everything all limits the raising of optical thin film quality.
For optical thin film itself, in addition to optical property needs to improve, absorb, scatter etc. except light loss need to reduce, its machine
Tool intensity, chemical stability and physical property require to be further improved.In laser system, the anti-laser intensity of optical thin film
Lower, this is one of sixty-four dollar question in optical thin film research.
The power of the anti-laser action ability of optical thin film commonly uses optical thin film laser damage threshold (LIDT) size to comment
The LIDT of valence, optical thin film is bigger, and anti-laser action ability is stronger, and the measurement of laser damage in thin films threshold value (LIDT) with it is thin
The judgement whether film damages, the two be it is inseparable, accurately to measure laser damage in thin films threshold value (LIDT), just must be accurate
Ground judges whether film is damaged.Therefore, the anti-laser action ability of optical thin film is studied, it just must Study of Laser film
Non-destructive tests.The method of differentiation thin film damage respectively has advantage and disadvantage at present: it is intuitive accurate that phasecontrast microscope method determines that damage has
Advantage, but it is expensive, it is relatively time-consuming, it is unable to the damage results of given amounts value；He-Ne light intensity scattering method is to miscellaneous in film
Matter, defect and working environment are very sensitive, and experimental error is relatively large.Photothermal deflection method is cleverer compared with phasecontrast microscope observation method
It is quick, but to test environment it is more demanding, and test build it is more complex；Acousto-optic method measurement sensitivity with higher, still
Noise is affected to its result, is easy to produce misjudgment phenomenon.Above-mentioned several method receives in laser film non-destructive tests
The extensive concern of optics worker, and also carrying out constantly studying at present.They are detected with different principles respectively
The damage from laser degree of film, has their own advantages, but also all have deficiency.So induced with laser thin film damage Study of recognition is one
The element task that item needs to adhere to for a long time, only non-destructive tests are reliable, and the accuracy of the LIDT measured could improve.
Traditional plasma flicker method differentiates that the schematic illustration of thin film damage is as shown in Figure 1.Light laser is successively by declining
It is focused near the film at detected sample sample platform after subtracting device, focusing system, beam splitter, if laser energy is more than the breakdown institute of film
The energy threshold needed, will generate plasma spark, if there is flash of light, be glistened and by detecting element acquisition by flashing signal
It is converted to electric signal and sends computer to, thus judge that film has damaged.In fact, laser in transmission process, works as incidence
When laser energy density is more than threshold of air breakdown, air plasma flash of light, this air plasma flash of light can be also generated
Film plasma spark will be interfered, cause detecting element can not the signal of resolved detection be air or film
Plasma spark signal and thin film damage misjudgment phenomenon occurs.This misjudgment phenomenon most directly influence result be exactly cause it is thin
The measurement inaccuracy of film laser damage threshold (LIDT), in turn, inaccurate LIDT value influences the anti-laser action energy of optical thin film
The evaluation of power.Thin film damage identification is accurately carried out, accurate laser damage in thin films threshold value (LIDT) value is obtained, to optical thin film
Anti- laser action ability is correctly evaluated, and this misjudgment phenomenon must be just eliminated.
Optical film technique is widely used in optics and photoelectron technical field, manufactures various optical instruments.Such as: it is high-precision
Spend detector, the very high computer chip of integrated level, accurate weapon system etc..Because the thickness of optical thin film is mostly in nanometer
To the micron order of magnitude, so the requirement of the links such as thin-film material, thin film preparation process and films test is all very high, for
For films test link, sixty-four dollar question is exactly the anti-laser ability of testing film, with traditional plasma flicker method
When identifying thin film damage, differed constantly as nanosecond order even more even if air and the plasma spark generated with film are lighted
It is small, also it can come wrong judgement and calculated result to the calibration tape of the anti-laser ability of film, currently, either phasecontrast microscope
Method, He-Ne light intensity scattering method, photothermal deflection method, acousto-optic method or traditional plasma flicker method, cannot all accurately identify air
It glistens with the plasma of film, the indistinguishable of the plasma flash of light of air and film directly results in traditional plasma flash of light
Method identifies the frequent erroneous judgement of thin film damage, influences the evaluation of the anti-laser action ability of optical thin film, therefore, conventional plasma therewith
Body flicker method is not used widely.
Summary of the invention
Present invention aims in view of the above shortcomings of the prior art, propose one kind can accurately carry out thin film damage knowledge
Other method and device that thin film damage is differentiated based on the plasma ignition time.
The present invention is a kind of method that thin film damage is differentiated based on the plasma ignition time, is comprised the following steps that
Step 1 is with different detector acquisition reference signals and flashing signal: being acquired respectively with different photodetectors
Incident laser signal, air and film plasmon flashing signal, simultaneously the synchronous feeding signal receiving device of all acquisition signals
Show respective signal waveform；
Step 2 obtains reference signal and flashing signal initial time: by signal receiving device incident laser signal,
Air and film plasma spark signal data are handled, and using incident laser signal as benchmark signal, obtain incident laser
Signal, air plasma flashing signal and the respective initial time of film plasma spark signal；
Step 3 is using reference signal and the difference of flashing signal initial time as plasma spark burning time: to enter
The difference of the initial time of laser signal and air plasma flashing signal is penetrated as air plasma flash of light burning time；With
The difference of the initial time of incident laser signal and film plasma spark signal is as film plasma spark burning time；
Step 4 modeling and calculating plasma flash of light burning time: lighting time modeling to air plasma flash of light,
Utilize the electron density n during air breakdowneThe change rate formula of t obtains air plasma flash of light burning time at any time
tb；Film plasma spark burning time is modeled, film plasma ignition time t is calculatedm；
Step 5 judgement: comparison air plasmon flash of light burning time tbWith film plasmon flash of light burning time
tm, work as tb=tmWhen, illustrate air and the flash of light of film plasmon while generating, this phenomenon occurrence probability very little；Work as tb≠tmWhen,
Air and the flash of light of film plasmon do not generate simultaneously, can accurately differentiate；
Step 6 damage identification technique criterion: work as tb< tmWhen, air plasma flash of light is glistened prior to film plasma
Occur, is to differentiate thin film damage signal with flashing signal below；Work as tb> tmWhen, film plasma spark prior to air etc. from
Son flash of light occurs, and is to differentiate thin film damage signal with front flashing signal, is sent into computer with the thin film damage signal determined
The non-destructive tests of film are participated in, more accurate thin film damage data are obtained.
The present invention or a kind of device that thin film damage is differentiated based on the plasma ignition time, are issued strong by laser
Laser passes through optical filter, attenuator, and nearby induces film breakdown by the film that focusing system focuses on detected sample sample platform
And plasma spark is generated, it is received and is glistened with detector, energy meter reads the reflected light energy of beam splitter in real time, and computer is
Operating console, which is characterized in that the detector is at least three, and two of them are respectively placed on horizontal plane along laser emitting
The bilateral symmetry position of direction flashing signal, left side are film plasma spark signal sensor, and right side is air plasma
Body flashing signal detector, the setting of another incident laser signal sensor are visited in condenser lens side, incident laser signal
Attenuator group, detector acquisition incident laser and plasma spark signal are equipped with before surveying device and are converted to electric signal, it is above
Signal synchronous transfer obtained by detector is to signal receiving device.
The present invention differentiates misjudgment phenomenon existing for thin film damage for traditional plasma flicker method, in traditional plasma
A kind of method and dress that thin film damage is differentiated based on the plasma ignition time is proposed on the basis of flicker method identification thin film damage
It sets.
Compared with prior art, technical advantage of the invention:
1, when traditional plasma flicker method identification thin film damage, the reason of because of detecting element setting, easily air and
The plasma spark that film generates is obscured and generates erroneous judgement, when light laser acts on film surface, air plasma flash of light
It can be generated with film plasma spark, in existing thin film damage determination method, all be not carried out the differentiation to the two,
The difference of the burning time of general air plasma flash of light and film plasma spark is nanosecond order, this is thin for high-precision
It is that cannot be neglected for the damaging judge of film.Present invention utilizes different detectors, targetedly obtain air plasma
Body flash of light and film plasma spark signal, by comparing the air plasma flash of light of nanosecond order and film plasma
The burning time of flash of light has carried out accurate resolution to air plasma flash of light and film plasma spark, has made thin film damage
It identifies more acurrate；
2, the present invention inhales during modeling and calculating air and film plasma spark burning time according to multi-photon
The computation model that theory of electrolytic dissociation establishes air plasmon body burning time is received and cascaded, is only joined with the laser action of incident laser
Number is related, and model is simple, and computational accuracy can calculate after air is breakdown under any laser action parameter role up to 0.001ns
Air plasma glisten burning time；According to film when breakdown the interaction principle of film and laser establish film etc.
The computation model of gas ions burning time, the present invention need not distinguish the material of film, thickness and preparation process, can be directed to any list
The plasma spark burning time of layer film directly calculates, and computational accuracy is up to 0.001ns.
3, the present invention is based on the plasma ignition times to differentiate that the device of thin film damage is improved in conventional apparatus
, induced with laser thin film damage identification device is improved, reliability, the accuracy of experimental result and data is ensure that, ensure that
The accuracy of LIDT value.Synchronous transfer is to oscillograph after the signal of all photodetector acquisitions is converted to electric signal, with incidence
Laser signal is benchmark signal, and air and film plasma spark signal initial time difference, respectively air and
Film plasma spark burning time has carried out accurate resolution to air plasma flash of light and film plasma spark.
Experimental provision structure of the present invention is simple, air ion body flash of light burning time and film plasma spark burning time measurement essence
Degree is all up 0.1ns.
Detailed description of the invention
Fig. 1 is conventional apparatus schematic illustration；
Fig. 2 is the device of the invention schematic illustration；
Fig. 3 is the technology of the present invention route map；
Fig. 4 is that present invention damage differentiates flow diagram；
Fig. 5 is air plasma of the present invention flash of light burning time simulation calculation curve graph；
Fig. 6 is film plasma spark burning time simulation calculation curve graph of the present invention.
Specific embodiment
With reference to the accompanying drawings and examples to the detailed description of the invention.
Embodiment 1
Thin film technique is a Disciplinary Frontiers of modern science and technology research, is widely used in detected with high accuracy device, is integrated
Spend very high computer chip, accurate weapon system etc..Such as in many of high energy strong laser system optical thin film element,
For these optical thin film elements, surface deposit optical film is not required nothing more than to improve light transmission quality, and it is required to have
Stronger anti-laser action ability.Therefore it needs to solve there are two realistic problem in this field: first is that how laser film is made
It is standby；Second is that whether being damaged under light laser effect, how damage identifies, anti-laser action energy for the film of preparation
How power is judged.And the anti-laser action ability of optical thin film is often evaluated with laser damage threshold (LIDT), it refers to optics
The energy density of incoming laser beam when film generation Critical Damage.The LIDT of optical thin film is bigger, resisting laser damage ability
Better.
It is exactly to cause the measurement of laser damage in thin films threshold value (LIDT) inaccurate that this misjudgment phenomenon, which most directly influences result,
Really, inaccurate LIDT value directly affects optical film product and quality and application, and it is anti-sharp also to influence optical thin film certainly
The evaluation of light action ability.
For this purpose, the present invention proposes a kind of side for differentiating thin film damage based on the plasma ignition time with innovation after study
Method comprises the following steps that referring to fig. 4
Step 1 is with different detector acquisition reference signals and flashing signal: being acquired respectively with different photodetectors
Incident laser signal, air and film plasmon flashing signal, simultaneously the synchronous feeding signal receiving device of all acquisition signals
Show respective signal waveform；Using incident laser signal as benchmark signal, the air plasma flashing signal of acquisition and film etc.
Gas ions flashing signal and reference signal are when the difference on start time is respectively that respective air plasma flash of light is lighted
Between and film plasma spark burning time.
Because incident laser, air and the flash of light of film plasmon belong to the optical signal of different spectral bands, this hair
It is bright to acquire incident laser signal, air and film plasmon flashing signal respectively using different photodetectors, all letters
It is number synchronous to be sent into signal receiving device and show respective signal waveform.
Step 2 obtains reference signal and flashing signal initial time: by signal receiving device incident laser signal,
Air and film plasma spark signal data are handled, and using incident laser signal as benchmark signal, obtain incident laser
Signal, air plasma flashing signal and the respective initial time of film plasma spark signal.In this example, use
Matlab software handles incident laser signal, air and film plasma spark signal data, by processing, respectively
The initial time of reference signal, air plasma flashing signal and film plasma spark signal is obtained.
Step 3 is using reference signal and the difference of flashing signal initial time as plasma spark burning time: to enter
The difference of the initial time of laser signal and air plasma flashing signal is penetrated as air plasma flash of light burning time；With
The difference of the initial time of incident laser signal and film plasma spark signal is as film plasma spark burning time.
In other words, incident laser signal and difference of the air plasma flashing signal on start time are air etc.
Gas ions flash of light burning time；Incident laser signal and difference of the film plasma spark signal on start time are film
Plasma spark burning time.
Step 4 modeling and calculating plasma flash of light burning time: air plasma flash of light burning time is carried out
Modeling, utilizes the electron density n during air breakdowneThe change rate formula of t obtains air plasma shining point at any time
Fire time tb；Film plasma spark burning time is modeled, film plasma ignition time t is calculatedm。
The present invention is during modeling and calculating air and film plasma spark burning time, according to Multiphoton Absorbtion
Establish the computation model of air plasmon body burning time with cascade theory of electrolytic dissociation, only with the laser action parameter of incident laser
Correlation, model is simple, and computational accuracy can calculate after air is breakdown under any laser action parameter role up to 0.001ns
Air plasma flash of light burning time；According to film when breakdown the interaction principle of film and laser establish film etc. from
The computation model of daughter burning time, the present invention need not distinguish the material of film, thickness and preparation process, can be directed to any single layer
The plasma spark burning time of film directly calculates, and computational accuracy is up to 0.001ns.
Step 5 judgement: comparison air plasmon flash of light burning time tbWith film plasmon flash of light burning time
tm, work as tb=tmWhen, illustrate air and the flash of light of film plasmon while generating, this phenomenon occurrence probability very little；Work as tb≠tmWhen,
Air and the flash of light of film plasmon do not generate simultaneously, can accurately differentiate.
Step 6 damage identification technique criterion: work as tb< tmWhen, air plasma flash of light is glistened prior to film plasma
Occur, is to differentiate thin film damage signal with flashing signal below；Work as tb> tmWhen, film plasma spark prior to air etc. from
Son flash of light occurs, and is to differentiate thin film damage signal with front flashing signal, is sent into computer with the thin film damage signal determined
The non-destructive tests of film are participated in, more accurate thin film damage data are obtained.
Referring to Fig. 3, technology path of the invention is to establish model when Irradiation of High optical thin film and calculate air etc.
Gas ions flash of light burning time and film plasma spark burning time pass through the actual value of both experimental provision tests.It is right
Theoretical calculation and experimental results are analyzed, and the technology criterion of thin film damage erroneous judgement is obtained.
The present invention different detector acquisition reference signals and flashing signal；Obtain reference signal and flashing signal starting
Moment；Obtain plasma spark burning time；Model simultaneously calculating plasma flash of light burning time；Judgement；Non-destructive tests skill
Art criterion completes the resolution of air and film plasma spark.
Embodiment 2
The method of thin film damage is differentiated with embodiment 1, to air etc. described in step 4 based on the plasma ignition time
Time modeling is lighted in gas ions flash of light, specifically
In formula, neFor the electron density during air breakdown, t is time, τpFor laser pulse width, E is incident laser energy
Amount, r are laser focal beam spot radius, and N is air molecule density, and k is the number of photons for ionizing an atom and needing while absorbing, σ
For the photon absorption cross sections of atom step, h=6.626 × 10-34For Planck's constant.Q is air coefficient, vmFor momentum of electron
Transfer collision frequency, c=3 × 108It (m/s) is the light velocity, λ is laser wavelength of incidence, and n=1.0003 is air refraction.
Theoretical foundation according to the present invention has: photonic absorption and cascade ionization when air is by laser breakdown.Multi-photon
Absorption process refers to an atom while absorbing k photon, and the gross energy of these photons is not less than the ionization potential of the atom, thus
Bring it about ionization.Electron avalanche or cascade ionization refer to that initiating electron obtains energy from the electric field of laser, when this energy is sufficiently large
When, and if atomic collision, atom excitation can be made to be ionized, so continuous collision.
The present invention establishes the calculating mould of air plasmon body burning time according to Multiphoton Absorbtion and cascade theory of electrolytic dissociation
Type, only related to the laser action parameter of incident laser, model is simple, can calculate air quilt under any laser action parameter role
Air plasma flash of light burning time after breakdown.
Embodiment 3
Method based on plasma ignition time differentiation thin film damage is dodged with embodiment 1-2 by air plasma
Luminous point combustion time model obtains electron density neThe curve of t variation at any time referring to Fig. 5, then chooses air quilt from the curve
Puncture moment point, it is electron density n at the time of air breakdown that selection principle, which is in the air of normal temperature and pressure,eEqual to 1013cm-3
At the time of corresponding, air is breakdown at this time, and air plasma is ignited.
The present invention acts on the breakdown mechanism of lower air to light laser and is studied, according to Multiphoton Absorbtion and cascade electricity
From the computation model that theory establishes air plasmon body burning time, computational accuracy is up to 0.001ns.
Embodiment 4
Method based on plasma ignition time differentiation thin film damage acquires incident laser signal with embodiment 1-3
Photodetector service band requires to be 800-1700nm；Acquire the photodetector operating wave of air plasmon flashing signal
Duan Yaoqiu is 400-1100nm；The photodetector service band for acquiring film plasmon flashing signal requires to be 150-
550nm。
Embodiment 5:
For method based on plasma ignition time differentiation thin film damage with embodiment 1-4, the present invention provides one specifically
The result of calculating:
N=2.7 × 10 are taken respectively in formula (1)19(cm-3), q=1021(cm-1s-1V-2), νm=3.9477 × 1013
(s-1), ν=1015(s-1), σ=10-16(cm-2), λ=1.064 × 10-6(m), τp=10-8(s), r=0.015 (cm).Normal
In the air of normal temperature and pressure, air breakdown at the time of, can be defined as electron density equal to 1013cm-3At the time of corresponding, air at this time
It is considered having punctured, air plasma has been ignited.If acting on light laser ENERGY E=82.4mJ, t is obtainedbCalculate knot
Fruit is as shown in figure 5, tbFor 1.856ns.
Film plasma spark burning time is modeled described in step 4, specifically
In formula, e, m, E, w, υe、tpThe quantity of electric charge, electron mass, laser field field strength, laser angular frequency, electronics is respectively indicated to touch
Hit frequency and pulsewidth；E=2P/ (c ε0), P, c, ε0Respectively indicate laser power density, the light velocity, dielectric constant；Nec、Ne、Ne0Point
It is not the electron density of breakdown critical value, the electron density of t moment and initiating electron density, vLIndicate the ionization of atom or molecule
Rate, ELFor vapor atomic or the ionization energy of molecule, then when film is breakdown, electron density N in steameCritical value must be reached
NecIf by tmReach Nec, the plasma ignition time is tm。
According to laser and material interaction principle, after strong laser irradiation to film surface, film surface a thin layer is first
It is heated to gasifying by laser, which continues to absorb incident laser energy, and temperature continues to rise, and its electricity known to saha equation
It is also improved from degree, plasma is formd when reaching a certain level.If from the increased process angle of electronics (ion) density
Illustrate the generation of plasma, how many pairs of ionization process of a small amount of free electron, breakdown threshold, film etc. on film surface
Gas ions flash of light burning time all has a great impact, referred to as initial free electrons.In the process that film surface gasification layer is formed
In, initial free electrons absorb laser energy by reverse drag anticline process, and electron density will increase, and electrons are constantly inhaled
Laser energy is received, continues ionization and goes down, reaches the gesture for forming snowslide afterwards to a certain degree, is i.e. film plasma spark is lighted.
It is the single layer Al of λ/4 with optical thickness2O3For film, if effect light laser wavelength X=1064nm, pulsewidth τp=
10ns, ENERGY E=82.4mJ, focal beam spot radius r=0.015cm can be obtained by formula (2), the point of film plasma spark
Fire time tmFor 7.843ns, as shown in Figure 6.
The present invention according to film the interaction principle of film and laser establishes film plasma ignition when breakdown when
Between computation model, it is not necessary to distinguish the material of film, thickness and preparation process, can for any single thin film plasma dodge
Light burning time directly calculates, and computational accuracy is up to 0.001ns.
Embodiment 6
The present invention or a kind of device that thin film damage is differentiated based on the plasma ignition time, with it is above-mentioned based on it is equal from
Based on daughter burning time differentiates the method for thin film damage, many devices for differentiating thin film damage can be designed or derive,
Here the apparatus structure that thin film damage is differentiated based on the plasma ignition time is provided.
Existing traditional plasma flicker method differentiates that the schematic illustration of thin film damage is as shown in Figure 1.Nd:YAG laser
The light laser that device issues nearby is induced after optical filter, attenuator by the film that focusing system focuses on detected sample sample platform
It punctures and plasma spark occurs, and energy meter reads the reflected light energy of beam splitter in real time, and computer is operating console.
Flashing signal, if there is flash of light, is converted to electric signal and sends meter to by unique detecting element for detecting flashing signal
Calculation machine, thus judges whether film damages.
In fact, laser in transmission process, when incident laser fluence is more than threshold of air breakdown, can also generate
Air plasma flash of light, will interfere film plasma spark, cause detecting element can not resolved detection
Signal is the plasma spark signal of air or film and thin film damage misjudgment phenomenon occurs.
Referring to Fig. 3 the burning time of air and film plasma spark can be calculated separately and measured in order to eliminate erroneous judgement
(tbAnd tm), the two is differentiated in time, keeps thin film damage identification more acurrate.In view of the above-mentioned problems, the present invention is specially set
Count it is a kind of based on the plasma ignition time differentiate thin film damage device specifically included laser along laser emitting direction
1, optical filter 2, attenuator 3, focusing system 4, beam splitter 5, detected sample sample platform 7, energy meter 6 are connected with beam splitter 5, focusing system
4 are made of at least two condenser lenses, and detector 9 is located at the side rear of 4 first lens of focusing system, pacify in flash of light two sides
Equipped with flash of light detector, all signals in 8 reception system of computer realize the control to whole device.
Detected sample is focused on after optical filter 2, attenuator 3, and by focusing system 4 by the light laser that laser 1 issues
Film at sample platform 7 nearby induces film breakdown and generates plasma spark, and energy meter 6 reads the anti-of beam splitter 5 in real time
Light energy is penetrated, computer 8 is operating console.Detector acquisition plasma spark signal is simultaneously converted to electric signal, referring to figure
2, detector of the invention is at least three, in this example, and detector is three, and two of them are respectively placed on horizontal plane along laser
The bilateral symmetry position of exit direction flashing signal, left side are film plasma spark signal sensor 13, and right side is air
Plasma spark signal sensor 10, another incident laser signal sensor 9 are arranged in first of focusing system thoroughly
Mirror side rear is equipped with attenuator group before being along laser direction of travel on horizontal plane before incident laser signal sensor 9, visit
Survey device 13 acquire film plasma spark signal, detector 10 acquire air plasma flashing signal, detector 9 acquire into
Laser signal is penetrated, all signals of acquisition are converted to electric signal, and signal synchronous transfer to signal obtained by three above detector connects
Receiving apparatus.Signal receiving device is oscillograph in this example, by all signal waveforms of 12 simultaneous display of oscillograph.The present invention utilizes three
A high speed free space photodetector replaces a common photodetector in conventional apparatus, eliminates the mistake of conventional apparatus
Sentence phenomenon, accurately identified whether film damages, provides guarantee to obtain accurate film LIDT value.
When traditional plasma flicker method identifies thin film damage, the reason of because of detecting element setting, easily air and thin
The plasma spark that film generates is obscured and generates erroneous judgement, when light laser acts on film surface, air plasma flash of light meeting
It is generated with film plasma spark, in existing thin film damage determination method, is all not carried out the differentiation to the two, one
As air plasma flash of light and film plasma spark burning time difference be nanosecond order, this is for nanometer scale height
It is that cannot be neglected for the damaging judge of precision film.Present invention utilizes different detectors, targetedly obtain air
Plasma spark and film plasma spark signal, by comparing the air plasma flash of light of nanosecond order and film etc.
The burning time of gas ions flash of light has carried out accurate resolution to air plasma flash of light and film plasma spark, has made thin
Membrane damage identification is more acurrate.
Experimental provision structure of the present invention is simple, and science research input needed for the photodetector used is few, and measurement accuracy can
Up to 0.1ns.The comprehensive sex expression of the present invention is that the integrated use of the professional relevant knowledge of more of light, mechanical, electrical and calculation etc., measurement skill
The integrated use of art and control technology and the integrated use of hardware and software co-design.The present invention is free using three high speeds
Space photodetector replaces a common photodetector in conventional apparatus, eliminates the misjudgment phenomenon of conventional apparatus, quasi-
It really identifies whether film damages, provides guarantee to obtain accurate film LIDT value.
Embodiment 7
Differentiate the method and device of thin film damage with embodiment 1-6 based on the plasma ignition time.Photoelectricity of the invention
Detector is at least three, this is most basic setting, as needed, can also add photodetector near flash of light, than
Such as four or more, or to improve precision, or adjust because of the adjustment of incident light source.
The attenuator group added before incident laser signal sensor in this example, attenuator group are within 10% by transmitance.
Attenuator group is combined by two optical filters and is constituted in this example, and the transmitance of the attenuator group of formation is 4%.Two optical filters it is saturating
The rate of mistake is respectively 20% and 20%.
Because incident laser energy is very big, in order to which effective protection incident laser detector avoids it from being damaged by light laser, enter
Attenuator group has been added before penetrating laser signal detector.
Embodiment 8
Differentiate the method and device of thin film damage with embodiment 1-7 based on the plasma ignition time.Acquire incident laser
9 service band of photodetector of signal requires to be 800-1700nm, and the rise time is less than 70ps；Air plasmon is acquired to dodge
10 service band of photodetector of optical signal requires to be 400-1100nm, and the rise time is less than 150ps；It is in vitro to acquire film etc.
13 service band of photodetector of sub- flashing signal requires to be 150-550nm, and the rise time is less than 5ns.The present invention is different
Detector acquisition reference signal and flashing signal；Obtain reference signal and flashing signal initial time；Obtain plasma sudden strain of a muscle
Light burning time, waveband selection is with strong points, and the rise time is able to satisfy signal acquisition requirement completely, ensure that measuring accuracy.
In this example attenuator group by transmitance be respectively 20% and 40% filter set at the transmitance of attenuator group is
8%.
Embodiment 9
Differentiate the method and device of thin film damage with embodiment 1-8 based on the plasma ignition time.In this example, letter is received
The oscillograph that number device uses, oscillograph at least need triple channel, and sample rate is no less than 10G sample/s, and bandwidth is not less than
300MHz, storage depth are not less than 20M sample.As long as receiving signal device to be able to satisfy while receiving three road signals and show,
Time interval between each sampled point is no more than 0.1ns, and the sampling precision of signal receiving device is higher, experiment test knot
Fruit error is smaller, and precision is higher.
In this example attenuator group by transmitance be respectively 10% and 20% filter set at the transmitance of attenuator group is
2%.
Embodiment 10
Differentiate the method and device of thin film damage with embodiment 1-9 based on the plasma ignition time.Present invention connection is each
The coaxial cable gauge size tolerance length of detector and signal receiving device must it is completely the same, in this example, use it is coaxial
Cable is SMA male connector to BNC male connector, 48 inches, guarantees synchronous transfer.
The more specifical example for combining method and apparatus is given below, the present invention is further described.
Embodiment 11
Differentiate the method and device of thin film damage with embodiment 1-10 based on the plasma ignition time.
The present invention differentiates in traditional plasma flicker method to be improved on thin film damage device basic, the principle of the present invention
Schematic diagram is as shown in Figure 2.The light laser that Nd:YAG laser 1 issues is gathered after optical filter 2, attenuator 3 by focusing system 4
Film of the coke at detected sample sample platform 7 nearby induces film and film surface air breakdown and plasma spark occurs, energy
Meter 6 reads the reflected light energy of beam splitter 5 in real time, and computer 8 is operating console.Detector 9 is the height of THORLABS production
Fast free space photodetector DET08CL/M, detector 10 are the high speed free space photodetector of THORLABS production
DET025AL/M, detector 13 are the high speed free space photodetector DET25K/M of THORLABS production, they are adopted respectively
Collection incident laser, air and film plasma spark signal are simultaneously converted to electric signal, and collected three road electric signal passes through
The identical SMA coaxial cable of THORLABS production, the RT01014 four-way oscillography produced by Rohde & Schwarz Representative Office
The output display of device 12, obtains the curve that signal voltage changes over time.Using Oringin software to incident laser signal, air
It is handled with film plasma spark signal data, has respectively obtained incident laser signal, the air as reference signal
The initial time of plasma spark signal and film plasma spark signal.Incident laser signal initial time is incident sharp
At the time of light reaches focus, on the basis of incident laser signal, the air plasma flashing signal and incident laser of acquisition are believed
Difference number on initial time is that air plasma glistens burning time tbMeasured value, film plasma spark signal with
Difference of the incident laser signal on initial time is film plasma spark burning time tmMeasured value.It is inhaled in conjunction with multi-photon
Receive and cascade the air plasma flash of light burning time t that theory of electrolytic dissociation Modeling Calculation obtainsbTheoretical value and laser and material
The film plasma spark burning time t that interaction theory Modeling Calculation obtainsmTheoretical value, judgement of concluding:
First determine whether air plasma flash of light burning time tbWith film plasma spark burning time tmWhether phase
Deng.Work as tb=tmWhen, illustrate air and the flash of light of film plasmon while generating, this phenomenon occurrence probability very little；Work as tb≠tm
When, air and the flash of light of film plasmon do not generate simultaneously, can accurately distinguish.
Judge which works as t as thin film damage signal is differentiated in two flashing signals againb< tmWhen, air plasma
Body flash of light is glistened prior to film plasma to be occurred, and the flashing signal generated after judgement is differentiation thin film damage signal；Work as tb> tm
When, film plasma spark glistens prior to air plasma to be occurred, and is believed with the flashing signal first generated for differentiation thin film damage
Number.The present invention obtains differentiating thin film damage signal, which is believed using the burning time of flashing signal as point of penetration
Number feeding computer participates in the non-destructive tests of film, obtains accurate thin film damage data.
Since incident laser energy is very big, in order to protect detector 9, attenuator group 11 is placed before it, is decayed in this example
Piece group at the transmitance of, attenuator group is 6% by the filter set that transmitance is respectively 20% and 30%.
Technical effect of the invention is explained again below by experiment and its result.
Embodiment 12
Differentiate the method and device of thin film damage with embodiment 1-11 based on the plasma ignition time.
In this example, the laser output wavelength of high power Nd:YAG solid state laser is 1064nm, and output energy is 5mJ-
235mJ is adjustable, and focal beam spot radius is 0.015cm, pulse width 10ns.Referring to fig. 2, the laboratory sample on sample stage 7 is light
Learn the single layer Al with a thickness of λ/42O3Film (central wavelength 1064nm), base material are diameter of phi 30mm, the K9 of thickness 2mm
Glass.In order to guarantee the stability of laser output energy, the input voltage of laser is remained unchanged in experiment.
Table 1 is that 10 groups of close incident laser energies act on lower air plasma flash of light burning time tbWith film plasma
Body flash of light burning time tmExperimental data, in this example, oscillograph 12 obtains three tunnels acquisition signal with 1 μ s sampling time, respectively
At the time of recording every road signal from scratch, i.e. CH1, CH2 and CH3, they respectively indicate incident laser signal, air and film
At the beginning of plasma flashing signal, i.e. initial time, then air plasma glistens burning time tbIt is that CH2 and CH1 are poor
Value, film plasma spark burning time tmFor CH3 and CH1 difference.Being obtained after 10 groups of experimental data average treatments, entering
Penetrate laser action light laser energy be 82.4mJ when, air plasma glisten burning time tbAverage value is about 2.7ns, film
Plasma spark burning time tmAverage value is about 7.8ns.Table 1 gives air plasma flash of light burning time tbWith it is thin
Film plasma spark burning time tmExperimental data.
1 t of tablebAnd tmExperimental data
Result verification
The air plasma flash of light burning time t being calculated respectively with theoretical modelingbWith film plasma spark
Burning time tmTheoretical value, and the air plasma flash of light burning time t of experiment testbIt is lighted with film plasma spark
Time tmMeasured value, list can obtain the relationship of the two, as shown in table 2.
2 theoretical calculation of table and experiment test tbAnd tmCompare
As shown in Table 2, no matter theoretical calculation or test is tested, t can be obtainedb< tmConclusion, and theoretical calculation and reality
The result that test tries meets preferably, illustrates to act on single layer Al when light laser2O3When film surface, air plasma dodges
Light occurs prior to film plasma spark, has clearly differentiated air and film plasma spark moment in time, determines
The flashing signal generated afterwards is to differentiate thin film damage signal, which is sent into the damage that computer participates in film
Wound identification, obtains accurate thin film damage data, and this invention removes differentiating thin film damage with traditional plasma flicker method
When caused by judge by accident.
The present invention can obtain high-precision flash of light burning time, moreover it is possible to distinguish to flash of light burning time.The present invention couple
Light laser acts on the breakdown mechanism of lower air and is studied, and establishes air according to Multiphoton Absorbtion and cascade theory of electrolytic dissociation
The computation model of plasmon body burning time, computational accuracy is up to 0.001ns.According to film film and laser when breakdown
Interaction principle establishes the computation model of film plasma ignition time, it is not necessary to distinguish the material of film, thickness and preparation
Technique can directly be calculated for the plasma spark burning time of any single thin film, and computational accuracy is also up to 0.001ns.
The present invention also demonstrates the feasibility of calculation method with experimental provision, has told air in time and film plasma dodges
Light burning time, the measurement accuracy of burning time is up to 0.1ns.For in the case where light laser acts on optical thin film whether damage
How wound, damage identify this realistic problem, improve the uncertainty of measurement LIDT according to the technical solution of the present invention, obtain
A kind of method and device that thin film damage is differentiated based on plasma ignition time that can accurately identify thin film damage.It is theoretical
Thin film damage identification can accurately be carried out by demonstrating the present invention with experiment, and computation model is simple, and computational accuracy is high, experimental provision
Structure is simple, and air and film plasma spark burning time measurement accuracy are high, good reliability.
In brief, the method and device disclosed by the invention that thin film damage is differentiated based on the plasma ignition time.Its
Technical solution is: with different detector acquisition reference signals and flashing signal；When obtaining reference signal and flashing signal starting
It carves；Obtain plasma spark burning time；Model simultaneously calculating plasma flash of light burning time；Judgement；Damage identification technique
Criterion completes the resolution of air and film plasma spark, works as tb< tmWhen, air plasma flash of light prior to film etc. from
Son flash of light occurs, and is to differentiate thin film damage signal with flashing signal below；Work as tb> tmWhen, film plasma spark is prior to sky
The flash of light of gas plasma occurs, and is to differentiate thin film damage signal with front flashing signal.The present invention is obtained using at least three detectors
Take air and film plasma spark signal and incident laser signal, on the basis of the latter, obtain air and film etc. from
Daughter flash of light burning time, air and film plasma spark are told with this in time, obtain differentiating thin film damage
Signal obtains a kind of side that thin film damage is differentiated based on the plasma ignition time to eliminate the misjudgment phenomenon of original device
Method and device.The invention proposes a kind of method and device that thin film damage is differentiated based on the plasma ignition time, its masters
Want advantage to have: establishing the computation model of air and film plasma spark burning time, can calculate any single thin film etc.
Gas ions flash of light burning time；Experimental provision structure is simple, and measurement accuracy is up to 0.1ns.Thin film damage knowledge can accurately be carried out
Not.Present invention is mainly applied to the damage differentiations of the optical thin film under light laser effect.
Claims (5)
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| CN116818285A (en) * | 2023-06-30 | 2023-09-29 | 西安工业大学 | Method and device for determining duration of air plasma flash |
| CN116839870A (en) * | 2023-06-30 | 2023-10-03 | 西安工业大学 | Method and device for determining flash duration of film plasma |
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| CN116818285A (en) * | 2023-06-30 | 2023-09-29 | 西安工业大学 | Method and device for determining duration of air plasma flash |
| CN116839870A (en) * | 2023-06-30 | 2023-10-03 | 西安工业大学 | Method and device for determining flash duration of film plasma |
| CN116818285B (en) * | 2023-06-30 | 2024-04-26 | 西安工业大学 | Method and device for determining duration of air plasma flash |
| CN116839870B (en) * | 2023-06-30 | 2024-04-26 | 西安工业大学 | Method and device for determining flash duration of film plasma |
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