CN109782508A - A kind of method of nonlinear effect amplification and detection electronics ultrafast process - Google Patents
A kind of method of nonlinear effect amplification and detection electronics ultrafast process Download PDFInfo
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- CN109782508A CN109782508A CN201811539628.3A CN201811539628A CN109782508A CN 109782508 A CN109782508 A CN 109782508A CN 201811539628 A CN201811539628 A CN 201811539628A CN 109782508 A CN109782508 A CN 109782508A
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Abstract
The invention belongs to photonic crystal non-linear modulation technical field, specially a kind of method of nonlinear effect amplification and detection electronics ultrafast process.The method of the present invention includes: the selected photonic crystal system comprising nonlinear material, choose the frequency of some low transmission rate, choose ultrashort pumping and signal pulse, pumping pulse time span is significantly less than the residence time of signal pulse in the photonic crystal, it is reached by control pumping pulse in certain specific times, to amplify non-linear modulation effect, and nonlinear material internal electron ultrafast process can be observed.Caused by transmissivity significant changes caused by the method for the present invention are a kind of new " dynamic modulation mechanism "；It is only pumped in specific time, which can destroy between transmitted field Impulses and High Order Impulsive " coherent subtraction ", be substantially increased so as to cause transmissivity.The method of the present invention all has universality, and composition, structural parameters united to material parameter, photonic crystal or multiple scattering system etc. are simultaneously insensitive.
Description
Technical field
The invention belongs to photonic crystal non-linear modulation technical fields, and in particular in photonic crystal or multiple scattering system system
The method amplified nonlinear effect and detect ultrafast process inside electronics.
Background technique
Photonic crystal is a kind of variation of dielectric periodicity, artificial with effect of dispersion abundant and photon band gap
The novel photonics material of manufacture, characteristic is with photonic band gap and photon band gap.When single-frequency incident light frequency falls in photon
When in band gap, light can not be by infinitely great photonic crystal, still, for the photonic crystal of limited size, even if single-frequency incident light
Frequency still suffers from certain transmissivity in photon band gap.In general, if photonic crystal very thin thickness, transmissivity is just
Can be higher, and as photonic crystal thickness increases, transmissivity can quickly reduce.The transmission with thickness reduce the reason of be due to
Caused by Bragg diffraction, exactly, gradually subtract firstly, Bragg diffraction causes original incident wave to be dispersed into all directions
Few, but this is not main cause, core reasons are that the scattered wave of multiple Bragg diffraction can form with original incident wave and " be concerned with
Cancellation " effect, so that " total propagated forward wave " substantially weakens, so that transmissivity declines to a great extent (meanwhile rear to scattered wave
Meeting " relevant to be added ", causes reflectivity increasingly stronger).Currently, the research heat of photonic crystal and nonlinear effect interaction
One of point direction, it is common that the photonic crystal for acting on nonlinear material composition based on pump light generates nonlinear effect, comes real
The variation of existing certain specific frequency transmissivities, so as to as various devices (switch, logic gate etc.) Lai Yingyong.Currently,
Whether pulse pump or lasting optical pumping, " photonic band gap and bandgap shifted " mechanism is the mechanism being widely recognized as, the mechanism
Core concept is that, since pump light changes the dielectric constant or magnetic conductivity of photonic crystal in advance, photonic crystal keeps this shape
State causes photonic band gap and the lasting drift of band gap, so that the transmissivity (reflectivity) of incident light be caused significant change occur.But
It is that, when the time of pumping pulse being significantly shorter than the residence time of signal pulse in the photonic crystal, above-mentioned mechanism is obviously certainly
It contradicts, because pumping pulse only changes photonic crystal within the extremely short time (residence time of relative signal pulse)
Matter must not believe that " photonic crystal energy band and the lasting drift of band gap " at all, in fact, there are also many phenomenons all with " photon
Crystal energy band and bandgap shifted " thought is conflicting.
Here just there are an important non-linear modulation new mechanism problem, the new mechanism and traditional " static energy band drift
After shifting, then experienced by signal light " thought it is entirely different, be a kind of mechanism of dynamic modulation.In fact, photonic crystal is
One special case of multiple scattering system system, various complicated or simple multiple scattering systems system, complication system are, for example, quasi-crystalline substance or unordered
System, simple such as simple Fabry-Perot-type cavity (F-P cavity) can be carried out similar Nonlinear Dynamic modulation.If energy
It is enough to pass through the announcement and utilization to the new mechanism, so that it may greatly improve people to photonic crystal or other multiple scattering systems system and
The deep understanding of Nonlinear Dynamic modulation.People can carry out accurately non-linear regulation according to the new mechanism, and can be with base
The new method of " nonlinear effect amplification " and " observing material internal electronic processes " is obtained in the new mechanism.More into one
Step can carry out a variety of device designs, such as nonlinear switching, logical device, memory cell, continuous frequency spectrum based on the new mechanism
Intensity modulated and the detection etc. of electronics femtosecond/Ah 's ultrafast process, to generate extensive practical value.
Summary of the invention
It is an object of the invention to design it is a kind of based on ultra-fast nonlinear dynamic modulation process nonlinear effect amplification and
Detect the new method of electronics ultrafast process.
The method of nonlinear effect amplification and detection electronics ultrafast process provided by the invention, the specific steps are as follows:
(i.e. multiple obstacles form for step 1, the preliminary selected photonic crystal system comprising nonlinear material or multiple scattering system system
Other systems).Introduce the weak very strong ultrashort pumping pulse of ultrashort signal pulse and relative intensity of relative intensity, the two intensity
At least one magnitude is differed, pumping pulse time span requires to be significantly less than signal pulse in photonic crystal or multiple scattering system system
In residence time, in general, signal pulse and the time span of pumping pulse are pulse center frequencies corresponding period
1.5-2.5 times (preferably 2 times).Two pulses reach photonic crystal or multiple scattering system system along different paths.Ultrashort pumping pulse
It is to change material dielectric constant or magnetic conductivity that is, within certain time for the non-linear of excitation material；
Step 2, the transmitted field for detecting and recording ultrashort signal pulse (or mirror field).In the transmitted field of time domain observation signal pulse
(or mirror field) is generally formed by multiple pulse combineds, this is because signal pulse is in photonic crystal or multiple scattering system system
By Multiple Scattering (being known as Bragg diffraction in the photonic crystal), they are divided into Impulses and " High Order Impulsive " by we,
Impulses are exactly remainder of the original signal pulse after scattering, and High Order Impulsive includes Second Order Impulsive, three rank pulses, etc.
Deng being since Multiple Scattering generates.Sometimes, each rank pulse has certain overlapping in time.By Fourier transform, obtain
Transmissivity (or reflectivity) of the signal pulse in some frequency.In no pumping pulse, photonic crystal or multiple scattering system are chosen
Unite some " low transmission rate (or antiradar reflectivity) " frequency as concern frequency；Observed low transmission rate (or low reflection
Rate), it is due to caused by Impulses and " coherent subtraction " of High Order Impulsive on a specific frequency；
Step 3 changes " time difference of signal pulse and pumping pulse arrival ", such as can be with " fixed signal pulse reaches light
The time of sub- crystal simultaneously constantly changes the time that pumping pulse reaches photonic crystal " Lai Shixian.As soon as every change time time difference,
It is a kind of determining experimental state, for each experimental state, all measures the transmitted field (or mirror field) of ultrashort signal pulse.It is logical
The change time difference is spent to realize multiple experimental states, by measuring transmitted field (or mirror field), obtains the signal under every kind of state
Pulse is in the transmissivity (or reflectivity) of frequency of interest, and final to obtain signal pulse (or anti-in the transmissivity of frequency of interest
Penetrate rate) curve of poor variation at any time, i.e. " transmissivity changes vs and pumps the time " curve.In the concern frequency of selection, observe
Transmissivity (or reflectivity) at any time poor variation and there are significant changes, i.e., in the section of certain specific time differences, transmissivity
(or reflectivity), which will appear, to be dramatically increased；
Here, caused by transmissivity (or reflectivity) significant changes observed are a kind of completely new " dynamic modulation mechanism ", with " biography
The non-linear modulation mechanism of system " is entirely different." traditional non-linear modulation mechanism " refers to " long burst pumping " (pumping arteries and veins
The time span of punching is greater than signal pulse residence time) or sustained wave the case where pumping, in this case, (or hold for a long time
It is continuous) nonlinear effect meeting " long-time " change photonic crystal or the dielectric constant or magnetic conductance of multiple scattering body system caused by pump light
Rate, the transmission spectrum (or reflecting spectrum) so as to cause photonic crystal or multiple scattering body system is drifted about, quick in certain frequencies
It will appear transmissivity (or reflectivity) significant changes if sensillary area domain (such as photonic crystal band side).But in completely new dynamic tune
In making mechanism, ultrashort pumping pulse is to change " moment " (being significantly shorter than the residence time of signal pulse in the photonic crystal)
The dielectric constant or magnetic conductivity of photonic crystal or multiple scattering body can not be explained with " frequency spectrum drift ", at this point, ultrashort pumping
Nonlinear effect caused by light only gives " electromagnetic field still resided in system " field to be added to an extra phase.Completely newly moving
It in state modulation scheme, is only pumped in specific time, which can destroy between transmitted field Impulses and High Order Impulsive
" coherent subtraction " the reason of (originally low transmission rate), be substantially increased so as to cause transmissivity.It is observed that: (i) single order arteries and veins
Punching is pumped before initially moving off system, and transmissivity is almost without significant change；(ii) just initially moved off in Impulses
It is pumped after system, transmissivity starts to occur significantly raised；(iii) when " when Impulses leave system completely just "
It is pumped, transmissivity reaches maximum value, is the main peak of entire curve；(iv) pumped behind, transmissivity compares maximum value
Start slowly decline, but when system is left in second order, three rank pulses, has corresponding small peak.These phenomenons can use " pump
Pu pulse causes resident field in systems that phase change occurs " it is explained to destroy " coherent subtraction "；
To Mr. Yu's assigned frequency, reach ultrashort pumping pulse gross energy needed for some transmissivity, than tradition non-linear modulation
The small nearly magnitude of total pump energy needed for mechanism (long burst pumping or sustained wave pumping) reaches identical transmissivity,
To prove, which has extremely strong nonlinear effect amplifying power；
In this step, due to being a dynamic modulation process, what incoming signal impulse sense was subject to is " photon a crystalline substance for variation
Body or multiple scattering system system ", that is, the photonic crystal or multiple scattering system system are one " nonconservative systems ", and light is in some frequency
Significant change may occur for rate gross energy.It is observed that: even if pulse signal is each in the case where ignoring absorption completely
The sum of the transmissivity of frequency and reflectivity have significantly greater than 1 or less than 1, i.e., the dynamic process can be realized efficiently " non-linear
Modulating light frequency ", and realized in certain bandwidth range, this is also a kind of mechanism of greatly enlarged nonlinear effect；
Step 4, due to the nonlinear change of dielectric constant or magnetic conductivity be due to nonlinear material inside electronic processes determine
, so, the process variable of electron system just will affect the curve of " nonlinear change vs time ".Such as: if Electron Relaxation
Time is very short, and after pump light stops, nonlinear change rapidly decays to zero, and if the relaxation time it is longer, it is non-linear
Variation will be compared with slow-decay.Change the process variable and pulse parameter of nonlinear material internal electron system, repeats to walk respectively
Rapid 1-3 obtains " transmissivity changes the vs pumping time " curve " in the case of different electron systems "；
Step 5, the curve that " in the case of different electron systems " are obtained based on step 4 observe curvilinear characteristic with system internal electron
The changing rule of plant process parameter.And as calibration, according to " curve actually obtained " come the anti-electronics pushed away inside system
Plant process parameter, to obtain the parameter information of ultrafast process inside electronics.
In the present invention, nonlinear material described in step 1, including but not limited to one or more three ranks (Ke Er) are non-thread
Property material, second nonlinear material and other can by external electromagnetic field regulate and control nonlinear materials；Photon described in step 1 is brilliant
Body, including the planform and structural parameters in various lattice types, lattice constant, packing ratio, single primitive unit cell；Institute in step 1
The other systems for the multiple obstacles composition stated, the system that including but not limited to signal pulse can be made to form multistage scattering effect,
It is also possible to very simple system, such as Fabry-Perot-type cavity (F-P cavity) etc.；Ultrashort signal pulse described in step 1 surpasses
Short pumping pulse includes but is not limited to Gaussian pulse, modulation Gaussian pulse isopulse form and different pulse temporal and frequency domain
Range, pulse strength isopulse parameter.
In the present invention, the electronic processes inside nonlinear material described in step 4 include but is not limited to two energy levels, three energy
Grade, four-level and electron excitation, decaying in energy band equal-electron system etc. be any can to influence material dielectric constant, magnetic conductivity
Internal electron process；The process variable of electron system described in step 4 include but is not limited to electronic processes response time and
In the relaxation time, it also can include but is not limited to the service life etc. of each energy level of electron system, these time scales include but is not limited to fly
The time scale of second or Ah's second-time.
In the present invention, curvilinear characteristic includes but is not limited to transmission maxima, transmissivity decline speed, small peak in step 5
Position and height etc. features.
In conclusion the method for the present invention includes: tentatively selected " photonic crystal system or multiple scattering comprising nonlinear material
System unites (other systems being made of multiple obstacles) ", the frequency of some low transmission rate (antiradar reflectivity) of the system is chosen, is selected
Take ultrashort pumping pulse and signal pulse, pumping pulse time span requires to be significantly less than signal pulse in the photonic crystal
Residence time is reached in certain specific times by control pumping pulse, such as " has begun the system of leaving in Impulses
It pumps afterwards ", signal pulse can be made to dramatically increase in the transmissivity (reflectivity) of selecting frequency, and " just complete in Impulses
When full outgoing " it carries out pumping transmissivity (reflectivity) can be made to reach some maximum value.
(1) this is a kind of new method for amplifying " non-linear modulation effect ".Transmissivity (reflectivity) significant changes its
Core mechanism is:
The low transmission rate (antiradar reflectivity) of (i) photonic crystal system or multiple scattering system system is generally due to direct outgoing wave and to dissipate
Caused by " coherent subtraction " of ejected wave；
Change in dielectric constant caused by the non-linear modulation of (ii) short time, and then cause " to still reside in photonic crystal
Field " phase changes；
(iii) pumped in certain specific times, which can substantially destroy original " coherent subtraction ".
So need to only continue very short time pumping can make transmissivity (reflectivity) significant changes.With traditional " long-time arteries and veins
Punching pumping " (pumping pulse time span is significantly greater than pulsed light residence time) or " sustained wave pumping " method is compared, Yao Shixian
" an equal amount of transmissivity (reflectivity) variation ", the pumping gross energy that this method needs can with low an order of magnitude, so, it is non-
The amplification effect of linear effect is obvious.
(2) simultaneously, which is a kind of new method for observing nonlinear material internal electron ultrafast process.Due to
Should during, transmissivity variation many curve characteristics (such as speed and width of the rise and fall of main peak and small peak), all according to
Rely the characteristic parameter of material nonlinearity, such as nonlinear relaxation time etc., that is, different nonlinear relaxation times can generate difference
Adjustment curve characteristic, and on the other hand, the nonlinear relaxation time of material is generally dependent on " the ultrafast mistake of electronics of material internal
Journey ", that is, we can observe the modulated transmittance graph of Nonlinear Dynamic and carry out the super of indirect observation material internal electronics
Fast process characteristic.
What the method for the present invention occurred either way has universality, to material parameter, photonic crystal or multiple scattering system
Composition, structural parameters of system etc. are simultaneously insensitive.
Detailed description of the invention
Fig. 1 is the operation schematic diagram that ultra-fast nonlinear dynamic modulation photonic crystal leads to transmissivity significant change.
Fig. 2 is photon crystal structure schematic diagram.
Fig. 3 is the in-field of signal pulse and pumping pulse.
Fig. 4 is the transmitted field of signal pulse.Wherein, when (a) is no pumping pulse, the transmitted field of signal pulse (b) is
The transmitted field of pump signal signal pulse when 98fs is reached.(note: fs, that is, femtosecond).
When Fig. 5 is no pumping pulse, transmission spectrum of the photonic crystal in transmitted field.Wherein, dotted line, imaginary point line are that photon is brilliant
The transmission spectrum of body Impulses and High Order Impulsive in transmitted field, solid line (include Impulses in total transmission field for photonic crystal
And High Order Impulsive) transmission spectrum.
Fig. 6 is under different pumping pulse arrival times, and signal pulse is in selected frequency f=3.735 × 1014Hz's is saturating
Penetrate rate change curve.
Fig. 7 is to carry out Fu to Impulses and High Order Impulsive in the case that pumping pulse reaches photonic crystal different time
In leaf transformation, obtain the multiple field amplitude in selected frequency, indicated respectively with solid arrow and dotted arrow.Abscissa is multiple field width
The real part of degree, ordinate are the imaginary part of multiple field amplitude.Angle between two vectors corresponds to the phase difference between them.Fig. 7
(a) -7 (f) respectively correspond pumping pulse arrival time as 0fs, 80fs, 92 fs, 98 fs, 120 fs, 198fs respectively.
Fig. 8 is the comparison of the transmission spectrum and reflectance spectrum under two kinds of mechanism.Wherein, (a) is in ultrashort pumping pulse arrival time
For in the case of 98fs (under this condition select frequency transmissivity reach maximum value), transmission spectrum (solid line) and reflectance spectrum (dotted line),
Due to being dynamic modulation mechanism, the sum of transmissivity and reflectivity may be greater than or less than 1；(b) it is based on traditional band offsets mechanism,
Continual and steady pumping is kept from 0fs to 200fs, the transmissivity of selected frequency can also be made to reach same raising amount, at this moment
Transmission spectrum (solid line) and reflectance spectrum (dotted line).The apparent difference of the two reflects entirely different modulation scheme.
Fig. 9 changes electronics in the service life of excitation level spontaneous decay, and observation " transmissivity changes vs and pumps the time " curve becomes
Change.Six lines represent the excitation level service life successively as T from top to bottom21=0.5fs, 1fs, 1.5fs, 2fs, the song of 2.5fs, 3fs
Line.
Specific embodiment
Illustrate a kind of nonlinear effect amplification based on Nonlinear Dynamic modulated process below by a specific example
With the new method of detection electronics ultrafast process.
1, Fig. 1 is a kind of operation schematic diagram of 2 D photon crystal logical device, we are realized in such a system based on non-
The nonlinear effect of linear dynamic modulated process is amplified and detection electronics ultrafast process.As shown in Figure 1, from external low-intensity
Signal pulse and high-intensitive pumping pulse reach photonic crystal from different light paths, and the two can be Gaussian modulation pulse, identical
Centre frequency 3.75 × 1014Hz and identical pulse time length 6fs(corresponds to the 2 of the period slightly larger than pulse center frequencies
Times).The optical path length of two pulses is adjustable, therefore can change the relative time that two pulses reach photonic crystal, " signal
The difference of pulse and pumping pulse arrival time " is Important Parameters of the invention.In this experiment, first assume unified time starting point
For " the sending time of signal pulse ", and the path length of signal pulse is set as a determining value, so that signal pulse arrives
Time up to photonic crystal is fixed as 28fs, changes " signal pulse and pumping by adjusting " arrival time of pumping pulse "
The difference of pulse arrival time ".
Fig. 2 is a two-dimensional photon crystal structure figure, and lattice constant is a=273nm.Black roundlet represents airport, dielectric
Constant is 1, radius 55nm, and blue baseplate material is poly styrene composite material, dielectric constant 2.5, third-order non-linear system
Number is 10-12cm2/ W, photonic crystal length is 40a, width 30a.In the photonic crystal, the residence time of signal pulse is about
60fs, much larger than the time span of pumping pulse, so meet that the present invention sets " time span of pumping pulse is significantly shorter than
Signal pulse residence time in the photonic crystal " condition.Assuming that nonlinear material is two energy level materials, pumping pulse can be electronics
From lower energy level (ground state) pumping to upper energy level, depending on the process variable of electron system in the service life of upper energy level, (such as electronics exists
The service life T of excitation level spontaneous decay21And the average time T2 etc. of electronic phase angle memory loss), these parameters can determine non-
The time of linear effect excitation and decaying.In detection electron system, we will change electronics in excitation level spontaneous decay
Service life T21, in other calculating, generally take T2=1fs, T21=2.8fs。
2, the time domain transmitted field of ultrashort signal pulse is recorded.Fig. 4 (a) shows the field of the transmitted pulse of " when no pumping pulse "
Figure, it has been found that transmitted pulse is made of multistage pulse, transmitted field is divided into Impulses and High Order Impulsive, Impulses are exactly
Original signal pulse " gradually weakens and directly through the remainder of photonic crystal " after scattering, High Order Impulsive (including two
Rank, three ranks, quadravalence isopulse) it is by being generated after Multiple Scattering, label 1 is the starting point of Impulses in fig. 4 (a),
Impulses and High Order Impulsive are line of demarcation with label 2, and second order, three ranks, quadravalence pulse are respectively line of demarcation with label 3,4,5.
When the transmissivity that pumping pulse arrival time is the selected frequency point of 98fs(reaches maximum value), time domain transmitted field is recorded as Fig. 4 (b),
The division of its each rank pulse and Fig. 4 (a) are consistent.Fig. 4 (a) and 4(b) compare, it is observed that when without pumping pulse and
When having pumping pulse, the temporal envelope of transmitted field is all almost consistent, and separating for each rank pulse is constant, so, each rank pulse is still
Intact definition.Fourier transformation and normalized are all carried out to Fig. 4 (a) transmitted field, so that it may obtain the reality in Fig. 5
Line, i.e., without photonic crystal transmission spectrum when pumping.It is also possible to carry out piecewise Fourier transformation and normalizing to Fig. 4 (a) transmitted field
Change processing, so that it may obtain the transmission spectrum of Impulses (dotted line) and High Order Impulsive (imaginary point line).From fig. 5, it can be seen that prohibiting
Region (low transmission region), although resultant field transmissivity (solid line) is lower, single order (dotted line) and high-order (imaginary point line) transmission
It composes not low, hence it is evident that, the low transmission rate of resultant field is as caused by coherent subtraction between Impulses and High Order Impulsive.It chooses low
Frequency f=3.735 × 10 of transmissivity14For Hz as concern frequency, transmissivity is about 12%.
3, constantly change pumping pulse and reach the time of photonic crystal, " signal pulse and pumping pulse reach to change
Time difference ", it is every to change primary, be just used as a basic experiment state, the transmitted field of signal pulse measured and recorded, by Fu
In leaf transformation obtain the transmissivity of selected frequency.Transmissivity is shown under the different pumping times with pumping arteries and veins in the curve of Fig. 6
The situation of change of arrival time is rushed, i.e. " transmissivity changes vs pumping pulse arrival time " curve.When pumping the time is 98fs
Transmissivity reaches maximum value, and the corresponding time is just the time that Impulses leave photonic crystal completely in Fig. 3.
4, from Fig. 6, it is observed that: (i) pumped that (pumping pulse is arrived before Impulses initially move off system
Up to the time before 86fs, the left side of label 1 in corresponding diagram), transmissivity is almost without significant change；(ii) rigid in Impulses
Just initially move off after photonic crystal and pumped (the pumping time between 86fs to 98fs, in corresponding diagram label 1 to 2 it
Between), transmissivity starts to occur significantly raised；(iii) when pumped " in Impulses system at once completely just " (pump
Time in 98fs, label 2 in corresponding diagram), transmissivity reaches maximum value, is the main peak of entire curve；(iv) carry out behind
Pumping, transmissivity start slowly to decline, but when second order, three rank pulses leave system completely, it is (corresponding to have corresponding small peak
The time 118fs and 155fs of label, label 3 and 4) in corresponding diagram.
In order to explain that " pumping pulse causes resident field in systems that phase change occurs " destruction " coherent subtraction " is
The reason of rate of penetrating greatly improves, we reach the photonic crystal time point the outgoing pulse in the case of no pumping and in pumping pulse
Not Wei 0fs, 80fs, 92 fs, 98 fs, 120 fs, 198fs when outgoing field Impulses and High Order Impulsive carry out Fourier's change
It changes, obtains the multiple field amplitude (containing real and imaginary parts) of concern frequency, and indicate on a complex plane, as shown in Figure 7.It is indicated by the solid line
Impulses answer field amplitude, and High Order Impulsive is represented by dashed line and answers field amplitude, angle reflection Impulses and height between two lines
The phase difference of multiple field amplitude between rank pulse.The feelings penetrated of signal pulse in the photonic crystal are not influenced compared to pumping pulse
Condition (as shown in Figure 7): (i) the case where being pumped before initially moving off system for Impulses, with the pumping time
Gradually to postpone, transmissivity can't be significantly increased, this is because pumping pulse has effect to Impulses and High Order Impulsive,
Both additional phase is obtained, as shown in Figure 7 (b), for pumping time 80fs, the angle of corresponding figure line is hardly
Become, this illustrates to determine that the phase difference of transmissivity size is almost unchanged, and coherent subtraction effect is constant, thus transmissivity will not be significant
It improves；(ii) pumped again after Impulses initially move off system, transmissivity will be significantly raised.This is because single order
The part that pulse has been moved off will not be influenced by pumping, so the extra phase that Impulses obtain reduces, and High Order Impulsive obtains
The extra phase obtained is almost unchanged.As shown in Fig. 7 (c), for pumping time 92fs, the angle of corresponding figure line becomes smaller, this says
Both bright phase difference becomes smaller, and coherent subtraction effect is destroyed, therefore transmissivity is significantly raised；(iii) when " proper in Impulses
When well leaving system completely (98fs) " it is pumped, transmissivity reaches maximum.This is because pumping pulse is to Impulses without work
With and act on entire High Order Impulsive and give its additional phase, as shown in Fig. 7 (d), in pumping time 98fs, Impulses
Figure line angle between High Order Impulsive reaches minimum value, and coherent subtraction effect is seriously damaged, so transmissivity is maximum；(iv)
It is pumped after 98fs, with the gradually postponement of pumping time, transmissivity starts slowly to decline than maximum value, but two
When system is left in rank, three rank pulses, corresponding small peak is had.In this period, pumping pulse, which acts only on, still remains in photon
Brilliant intracorporal High Order Impulsive field, the extra phase that High Order Impulsive obtains reduce, while Impulses are not acted on by pumping, such as
Fig. 7 (e) and (f) are shown, and by taking 120fs and 198fs as an example, the angle of two multiple field amplitudes becomes larger from minimum value, coherent phase
The effect that disappears gradually increases, and corresponds to the slow decline of transmissivity.The appearance reason of small peak be similar to top appearance, when by
The pulse of modulation is exactly whole rank, and the phase change of generation is most significant.
Above facts proved that the core reasons of the variation of transmissivity are: since " ultrashort nonlinear dielectric constant variation can make
There is a phase change at ' remaining in the light field in complex dielectrics system ' ", and " phase change can be destroyed originally
Existing coherent subtraction mechanism ", so that transmissivity be caused significantly to change.This is being modulated with traditional " long burst pumping "
There is the difference of essence in the mechanism of transmissivity.
5, ultrafast dynamic to reach same penetrance improvement effect compared with traditional " long burst pumping " mechanism
Pump energy needed for state modulation scheme wants much lower.Traditional " long burst pumping " mechanism, the action time of pumping are covered
Covered signal pulse entirely penetrates process, is to have experienced one " having changed dielectric constant " for signal pulse
System, the energy band of new system occur drift, so that the frequency in care obtains different transmissivities.The present invention, which uses, to be continued
Pumping pulse act on the identical photonic crystal of step 1, the duration do not entered also from signal pulse photonic crystal to
Signal field almost leaves photonic crystal, same available up to 58% transmissivity.But when we are new machine
The transmission spectrum made the transmission spectrum for reaching maximum transmission rate and reach same transmissivity under traditional mechanism compares, such as Fig. 9 institute
Show, hence it is evident that the two difference is huge, discloses the difference of their corresponding fundamental mechanisms.The gross energy pumped needed for new mechanism is
/ 6th of pump energy needed for traditional mechanism, this illustrates that new dynamic modulation mechanism has extremely strong nonlinear effect amplification energy
Power.
6, in step 1-4, due to being a dynamic modulation process, what incoming signal impulse sense was subject to is " a variation
Photonic crystal or multiple scattering system system ", that is, the photonic crystal or multiple scattering system system be one " nonconservative system ", light
Significant change may occur in some frequency gross energy.Detect and calculate pumping the time be 98fs when pulse center frequencies around
The sum of the transmissivity of each frequency and reflectivity, as shown in fig. 7,3.6 × 1014Hz to 3.9 × 1014Hz frequency separation, transmission
The sum of rate and reflectivity are significantly greater than 1, and 3.1 × 1014Hz to 3.5 × 1014Hz frequency separation, transmissivity and reflectivity it
Be significantly less than 1.So the dynamic process can efficiently realize " energy of Nonlinear Dynamic modulated signal light different frequency ",
And realized in certain bandwidth range, this is also a kind of amplification mechanism of nonlinear effect.
7, due to the nonlinear change of dielectric constant or magnetic conductivity be due to nonlinear material inside electronic processes determine
, so, the process variable of electron system just will affect the curve of " nonlinear change vs time ".Material it is non-linear be usually
As caused by light and electron system interaction, change electron energy level service life T21, " transmissivity variation vs pump can be changed significantly
Pu time " curvilinear characteristic.We take T21=0.5fs, 1fs, 1.5fs, 2fs, 2.5fs, 3fs keeps all other electron system
Parameter is constant, the method for repeating step 1-4, obtains their own " transmissivity changes the vs pumping time " curve.Fig. 9 is shown
" transmissivity changes vs and pumps the time " curve in the case of different electron systems.
8, by the feature of " transmissivity changes vs and pumps the time " curve, we can be with indirect detection electronics ultrafast process
Parameter, such as electronics is in the service life T of excitation level spontaneous decay21Equal parameters.It can be found that with T21Increase, " transmissivity
The variation of variation vs pumping time " curve is very significant and rich regularity compared to the time interval of only 0.5fs, for example,
The maximum value of transmissivity is with T21Increase and constantly increase, the maximum value of the transmissivity corresponding pumping time is with T21Increase and
Constantly in advance, the speed of transmissivity variation is with T21Increase and constantly increase.At this point, if with a unknown two-level energy system
Material manufactures the photonic crystal of same structure, by measuring its work figure line, can obtain its transmissivity maximum value and
The pace of change of corresponding pumping time and transmissivity, so as to estimate the time of the material spontaneous decay, and this is joined
Amount may be to be difficult to by directly observing.For example, can use Fig. 8 if the maximum value of transmissivity is 46% and estimate
The material electronics are counted out in the service life T of excitation level spontaneous decay21=2.25fs.Since the phenomenon has universality, can not only visit
The femtosecond process variable for surveying electronics can also be with electric in measurement system if higher frequency and shorter pulse are chosen in light pulse
Ah 's rank ultrafast process parameter of son.
The above-mentioned description to embodiment is for the ease of those of ordinary skill in the art it will be appreciated that and using invention.It is ripe
Knowing those skilled in the art obviously can be applied to it this General Principle illustrated by the simple modification to the present embodiment
In his embodiment without having to go through creative labor.Therefore, the present invention is not limited to the above embodiments, those skilled in the art's root
According to announcement of the invention, the improvement and modification that scope is made are not departed from, it is within the scope of the present invention.
Claims (5)
1. a kind of method of nonlinear effect amplification and detection electronics ultrafast process, which is characterized in that specific step is as follows:
Step 1, the preliminary selected photonic crystal system comprising nonlinear material or multiple scattering system system；It is weak to introduce relative intensity
The ultrashort pumping pulse of ultrashort signal pulse and relative intensity by force, the two intensity differ at least one magnitude, pumping pulse time
Length is significantly less than residence time of the signal pulse in photonic crystal or multiple scattering system system, and two pulses are arrived along different paths
It unites up to photonic crystal or multiple scattering system；Ultrashort pumping pulse is changed within certain time for the non-linear of excitation material
Become material dielectric constant or magnetic conductivity；
Step 2, the transmitted field for detecting and recording ultrashort signal pulse (or mirror field)；In the transmitted field of time domain observation signal pulse
(or mirror field) is formed by multiple pulse combineds, this is because signal pulse photonic crystal or multiple scattering system system in by
Caused by Multiple Scattering, they are divided into Impulses and " High Order Impulsive ", Impulses are exactly original signal pulse by scattering
Remainder afterwards, High Order Impulsive include Second Order Impulsive, three rank pulses, quadravalence pulse, etc., are since Multiple Scattering generates
's；By Fourier transform, signal pulse is obtained in the transmissivity (or reflectivity) of some frequency；In no pumping pulse, choosing
Take photonic crystal or multiple scattering system unite some " low transmission rate (or antiradar reflectivity) " frequency as concern frequency；It is observed
Low transmission rate (or antiradar reflectivity), be due to caused by Impulses and " coherent subtraction " of High Order Impulsive on a specific frequency
's；
Step 3 changes " time difference of signal pulse and pumping pulse arrival ", and time difference of every change is exactly to determine one kind
Experimental state measures the transmitted field (or mirror field) of ultrashort signal pulse for each experimental state respectively；When passing through change
Between difference realize multiple experimental states, by measuring transmitted field (or mirror field), obtain the signal pulse under every kind of state in institute
Pay close attention to the transmissivity (or reflectivity) of frequency, it is final obtain signal pulse frequency of interest transmissivity (or reflectivity) at any time
Between difference variation curve, i.e. " transmissivity change vs pump time " curve；In the concern frequency of selection, observe transmissivity (or
Reflectivity) at any time poor variation and there are significant changes, i.e., in the section of certain specific time differences, transmissivity (or reflectivity)
It will appear and dramatically increase；
Step 4, due to the nonlinear change of dielectric constant or magnetic conductivity be due to nonlinear material inside electronic processes determine
, the process variable of electron system just will affect the curve of " nonlinear change vs time "；Change nonlinear material internal electron
The process variable and pulse parameter of system, respectively repeat steps 1- step 3, obtain " the transmission " in the case of different electron systems "
Rate changes vs and pumps the time " curve；
Step 5, the curve that " in the case of different electron systems " are obtained based on step 4 observe curvilinear characteristic with system internal electron
The changing rule of plant process parameter, and as calibration, according to " curve actually obtained " come the anti-electronics pushed away inside system
Plant process parameter, to obtain the parameter information of ultrafast process inside electronics.
2. the method for nonlinear effect amplification and detection electronics ultrafast process according to claim 1, which is characterized in that step
In rapid 1, the nonlinear material be one or more third-order non-linear materials, second nonlinear material and other can be outer
The nonlinear material of electromagnetic field regulation；The photonic crystal includes various lattice types, lattice constant, packing ratio, single original
Planform and structural parameters intracellular；The multiple scattering system system, including signal pulse can be made to form multistage scattering effect
System, Fabry-Perot-type cavity (F-P cavity)；The ultrashort signal pulse, ultrashort pumping pulse include Gaussian pulse, modulation
Gaussian pulse is related to different pulse parameter: pulse temporal and frequency domain, pulse strength.
3. the method for nonlinear effect amplification and detection electronics ultrafast process according to claim 1 or 2, feature exist
In for the transmitted field of low transmission rate situation, being pumped in specific time, between Impulses and High Order Impulsive in step 3
" coherent subtraction " be effectively destroyed, be substantially increased so as to cause transmissivity, in which: (i) Impulses initially move off system it
Before pumped, transmissivity does not have significant change；(ii) pumped, transmitted after Impulses just initially move off system
Rate starts to occur significantly raised；(iii) pumped when " when Impulses leave system completely just ", transmissivity reaches most
Big value, is the main peak of entire curve；(iv) pumped behind, transmissivity starts slowly to decline than maximum value；In second order, three
When system is left in rank pulse, there is corresponding small peak；
To Mr. Yu's assigned frequency, reach ultrashort pumping pulse gross energy needed for some transmissivity, than traditional non-linear modulation machine
The small nearly magnitude of total pump energy needed for system reaches identical transmissivity illustrates that it has extremely strong amplification nonlinear effect
Ability；
Due to being a dynamic modulation process, what incoming signal impulse sense was subject to is " a photonic crystal or multiple scattering for variation
System system ", in some frequency gross energy significant change may occur for light；Even if in the case where ignoring absorption completely, pulse letter
Number it is significantly greater than 1 or less than 1 in the sum of the transmissivity of each frequency and reflectivity, i.e., the dynamic process is in certain bandwidth range
It can efficiently realize " non-linear modulation light frequency ".
4. the method for nonlinear effect amplification and detection electronics ultrafast process according to claim 3, which is characterized in that step
In rapid 4, the electronic processes inside the nonlinear material include in two energy levels, three-level, four-level and Energy band electron system
Any internal electron process that can influence material dielectric constant, magnetic conductivity such as electron excitation, decaying；The electron system
Process variable include electronic processes response time and relaxation time, the service life of each energy level of electron system, these time scales
Time scale including femtosecond or Ah's second-time.
5. the method for nonlinear effect amplification and detection electronics ultrafast process according to claim 1, which is characterized in that step
Curvilinear characteristic includes transmission maxima, transmissivity decline speed, the position of small peak and height in rapid 5.
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