CN103278251B - Ultra-strong femto-second laser pulse population parameter in-situ measurement system and measuring method and application - Google Patents

Abstract

The invention discloses a kind of ultra-strong femto-second laser pulse population parameter in-situ measurement system and measuring method and application.The present invention's x-ray measurement ultra-strong femto-second laser pulse, the photoelectron spectroscopy obtained from a measurement just can derive all parameters of femto-second laser pulse: intensity, pulse temporal width, carrier-envelope phase, pulse shape etc.; It is a kind of method of physics, does not need to do any hypothesis; It is a kind of analytic method, does not need time discrimination measurement, data fitting and iterative computation.Measuring method of the present invention is an in-situ measuring method, and do not need to do any change to the state of femto-second laser pulse to be measured, measurement result directly reflects the physical interconnection between parameters, and in real time, fast, high precision; The range of laser intensity can reach 4-5 the order of magnitude, and the relative accuracy of method is better than 0.1% for laser intensity, is better than 1% for other parameters, can be widely applied in scientific experiment and engineering survey.

Description

Ultra-strong femto-second laser pulse population parameter in-situ measurement system and measuring method and application

Technical field

The invention belongs to superpower ultra-fast optical, be specifically related to a kind of ultra-strong femto-second laser pulse population parameter in-situ measurement system and measuring method and application.

Background technology

Various superpower, ultrashort laser pulse has been widely used in scientific experiment and engineering, as High-order Harmonic Generation, above threshold ionize, non-linear laser-electronics Compton scattering, lasing ion acceleration etc.For the measurement of laser frequency, there is comparatively ripe method at present, but for the in site measurement of the intensity (i.e. energy density) of ultra intense laser pulse, pulsewidth, the population parameter such as carrier-envelope phase and pulse strength Annual distribution, be one of sciences problems always.When laser pulse intensity is lower, the measurements such as detector, streak camera such as photodiode, photomultiplier, various silicon can be used.But when laser intensity reaches such as I > 10 ⁹w/cm ²time, measuring media can be destroyed by laser pulse, cannot directly measure.The way that what the way of current employing was more is with estimation, namely by measuring the gross energy of light pulse, then measures space distribution and the pulse temporal width of light pulse, thus calculates intensity level.Also by measuring atom or the ionization spectrum of high-valence state inert gas ion in electric field of strong laser, laser pulse intensity data can be extracted from the momentum of analytical electron or ion.The method error very large (even reaching several times of actual value) of the former estimation, the sensitivity very little with dynamic range (relevant with the ionization property of actuating medium) that the latter measures.In addition, the various parameters for the pulse of computation and measurement result individually measure with different measuring methods, different experimental provisions and different time, and measurements and calculations result is a kind of statistical value, with physical interconnection and the poor real of various parameter.In a word, how to measure the specifically careful time structure of these light pulses quickly and accurately, be a challenge of scientific circles always.

Summary of the invention

In order to solve a difficult problem for the accurate Quick Measurement of intense pulse laser, the present invention proposes a kind of ultra-strong femto-second laser pulse population parameter in-situ measurement system and measuring method and application, X-ray is adopted to strengthen ionization technique, accurately can obtain whole parameters of each femto-second laser pulse, comprise the intensity of pulse, pulsewidth, carrier-envelope phase and pulse intensity distribution.

One object of the present invention is to propose a kind of ultra-strong femto-second laser pulse population parameter in-situ measurement system.

Ultra-strong femto-second laser pulse population parameter in-situ measurement system of the present invention comprises: psec or subpicosecond laser pulse, spectroscope, separation vessel, Laser pulse compression unit, the first intert-gas atoms and the second gas atom, the first and second convergent mirrors, photoelectron spectrograph and optical path adjustment device; Wherein, psec or subpicosecond laser pulse are split into two bundle laser after spectroscope; Wherein a branch of High-order Harmonic Generation and X-ray directly exciting the first intert-gas atoms generation forward emitted after the first convergent mirror; X-ray and laser pulse filter out laser after separation vessel, and the X-ray of arrowband wherein becomes the very little light beam of diameter; Spectroscope divides the another beam of laser, and after entering Laser pulse compression unit, becomes the linearly polarized femto-second laser pulse that the cycle is to be measured less; , conllinear coaxial with X-ray through this pulse of optical path adjustment device mixes and transmits; Femto-second laser pulse focuses on through the second convergent mirror, jointly excites the second gas atom with X-ray, produces photoelectron, measures its energy distribution at the polarised direction photoelectron spectrograph of laser.

Optical path adjustment device comprises the first to the 3rd catoptron, and psec or subpicosecond laser pulse are split into two bundle laser after spectroscope; Wherein a branch of High-order Harmonic Generation and X-ray directly exciting the first intert-gas atoms generation forward emitted after the first convergent mirror; X-ray and laser pulse filter out laser after separation vessel, and the X-ray of arrowband wherein becomes the very little light beam of the diameter of vertical direction after the first catoptron; Spectroscope divides the another beam of laser, and enters Laser pulse compression unit after the second catoptron, becomes the linearly polarized femto-second laser pulse that the cycle is to be measured less of parallel direction; This pulse the 3rd catoptron place and X-ray in the vertical direction coaxial, conllinear mix and transmit.

Second gas atom is intert-gas atoms or hydrogen atom.

Psec (picosecond) ps or subpicosecond laser pulse produce femto-second laser pulse to be measured through Laser pulse compression unit, the present invention adopts and place beam splitter before Laser pulse compression unit, thus Ps Laser Pulse is divided into two bundles, a branch of being used for produces femtosecond laser to be measured, another bundle is used for producing X-ray, thus femto-second laser pulse to be measured and X-ray in the vertical direction coaxial, conllinear mix and transmit, common excited inert gas atom produces photoelectron, measures its energy distribution with photoelectron spectrograph.The present invention adopts system cleverly, and do not need to do any change to the state of femto-second laser pulse to be measured, measurement result directly reflects the physical interconnection between parameters, is a kind of in-situ measuring method.On the one hand, because the time width of the X-ray of Ps Laser Pulse generation is psec or subpicosecond magnitude, femtosecond (femtosecond) fs laser pulse synchronization easy and to be measured after light path control; On the other hand, require that the beam dimensions of X-ray is much smaller than femto-second laser pulse, and coaxial conllinear.Therefore, the duration of femto-second laser pulse, the Strength Changes of X-ray is very little, can think continuous print; And values for spatial distribution change very little (Single-Intensity) SI of femto-second laser pulse, the maximal value of its intensity and the peak I of laser pulse.

The electric-field carrier envelope Gaussian function of linearly polarized femto-second laser pulse represents:

$F\left(t\right)=\exp (-4\ln 2\·t^2/{\mathrm{\τ}}_L^2),---\left(1\right)$

Wherein t is time variable, τ _lfor pulse temporal width and halfwidth degree FWHM.Laser pulse electric field E _lchange (amplitude E ₀) can represent with following formula:

Wherein for laser pulse angular frequency, Φ is carrier-envelope phase.Similarly, X-ray pulse electric field E _xchange (constant amplitude is set to 1 simply) can represent with following formula:

Wherein for X-ray pulse angular frequency.

Therefore, as long as obtain intensity (i.e. peak power density) I, carrier-envelope phase Φ and Laser pulse time width (halfwidth FWHM) τ of femto-second laser pulse to be measured _l, just can obtain the full detail of femto-second laser pulse, (I, Φ, τ _l) be the population parameter of laser pulse.

From half classical mechanics viewpoint, photoelectronic energy W (t) jointly excited by X-ray and laser electric field, flown out in the polarised direction of t generation, laser is

$W\left(t\right)=W_0+2U_p{F}^2\left(t\right){\sin }^2({\mathrm{\ω}}_{L}t+\mathrm{\Φ})$

$+\sqrt{8U_p{W}_0}F\left(t\right)\sin ({\mathrm{\ω}}_{L}t+\mathrm{\Φ}).---\left(4\right)$

Wherein W ₀=ω _x-I _pfor photoelectronic just kinetic energy, and ω _xand I _pbe respectively the photon energy of arrowband X-ray pulse and the ionization energy of gas atom or molecule. for photoelectronic matter kinetic energy.

Photoelectron spectroscopy is the photoelectron number measured in unit energy, and power spectrum has obvious border, and becomes three peaks, becomes peak position W _a, W _band W _c, be arranged as W from small to large _a, W _cand W _b.On photoelectron spectroscopy n (W) respectively with W _a, W _band W _cthe half classical prophesy value W that position is corresponding ₁, W ₂and W ₃cannot measure, but when laser pulse parameters is known, half classical prophesy value power spectrum n can be calculated _c(W) one-tenth peak position is as W ₁, W ₂and W ₃, they respectively with W _a, W _band W _ccorrespondence, and three ratio ε can be calculated ₁, ε ₂and ε ₃:

${\mathrm{\ϵ}}_1=\frac{n\left(W_a\right)}{n_c\left(W_1\right)},---\left(5\right)$

${\mathrm{\ϵ}}_2=\frac{n\left(W_b\right)}{n_c\left(W_2\right)},---\left(6\right)$

${\mathrm{\ϵ}}_3=\frac{n\left(W_c\right)}{n_c\left(W_c\right)}.---\left(7\right)$

Research and a large amount of calculating show, for specific laser carrier-envelope phase Φ, ratio ε ₁, ε ₂and ε ₃along with the change of laser intensity is very little.Therefore, within the scope of very large laser intensity, ratio ε can be thought ₁, ε ₂and ε ₃substantially close.

Another object of the present invention is to propose a kind of ultra-strong femto-second laser pulse population parameter in-situ measuring method.

A kind of ultra-strong femto-second laser pulse population parameter in-situ measuring method of the present invention, comprises the following steps:

1) psec or subpicosecond laser pulse are split into two bundle laser after spectroscope, wherein a branch of High-order Harmonic Generation and X-ray directly exciting the first intert-gas atoms generation forward emitted after the first convergent mirror, X-ray and laser pulse filter out laser after separation vessel, the X-ray of arrowband wherein becomes the very little light beam of diameter, spectroscope divides the another beam of laser, enter Laser pulse compression unit, become the linearly polarized femto-second laser pulse that the cycle is to be measured less, the femto-second laser pulse to be measured through optical path adjustment device is coaxial with X-ray, conllinear mixing and transmission,

2) femto-second laser pulse and X-ray focus on through the second convergent mirror, jointly excite the second gas atom, produce photoelectron, measure its energy distribution, obtain photoelectron spectroscopy n (W) at the polarised direction photoelectron spectrograph of laser;

3) lock the carrier-envelope phase Φ of femto-second laser pulse, from the photoelectron spectroscopy n (W) that measurement obtains, determine three peak position W _a, W _band W _c, with the energy value W ' of half At The Height of these peak positions _i=0.5n (W _j) be similar to the half classical prophesy value power spectrum n replacing photoelectron spectroscopy _c(W) one-tenth peak position, and calculate photoelectronic momentum off-set value, $\mathrm{\Δ}{p}_i\≡\sqrt{2{W^{\′}}_i}-\sqrt{2W_0},$ They are substituted into following formula calculate:

$\mathrm{\Φ}=\frac{\mathrm{\π}\ln (-\mathrm{\Δ}{p}_1/\mathrm{\Δ}{p}_2)}{\ln (\mathrm{\Δ}{p}_2/\mathrm{\Δ}{p}_3)},$

From three, formula (8) left side numerical value and population parameter (I, Φ, the τ of femto-second laser pulse can be calculated _l) namely tentatively separate (I, Φ, τ _l) ₁, wherein, i ∈ (1,2,3), j ∈ (a, b, c);

4) with above-mentioned preliminary solution (I, Φ, τ _l) ₁for the photon energy of input parameter and known arrowband X-ray (uses angular frequency represent), calculate theoretical photoelectron spectroscopy n ' (W) with quantum mechanics method, and determine three peak value W from the photoelectron spectroscopy of this theory _a', W _b' and W _c', and calculate the one-tenth peak position W of half classical prophesy value " ₁, W " ₂with W " ₃, thus calculate three relevant ratio (ε of prophesy value classical to half ₁, ε ₂, ε ₃) ₁, wherein ε ₁=n ' (W " ₁)/n ' (W _a'), ε ₂=n ' (W " ₂)/n ' (W _b'), ε ₃=n ' (W " ₃)/n ' (W _c'), then according to these ratio, the photoelectron spectroscopy n (W) obtained from initial measurement reads half classical prophesy value n _c(W) one-tenth peak position W ₁, W ₂and W ₃, and calculate photoelectronic momentum off-set value, they are substituted into formula (8) again calculate, obtain exact solution (I, Φ, the τ of the population parameter of femto-second laser pulse _l).

The photoelectron spectroscopy n (W) that X-ray and laser pulse excite hydrogen atom or intert-gas atoms to produce, has obvious border, and becomes three peaks, becomes peak position W _a, W _band W _c.Half classical prophesy value n of photoelectron spectroscopy _c(W) cannot measure experimentally, but when laser pulse parameters is known, can n be calculated _c(W) one-tenth peak position is as W ₁, W ₂and W ₃, they respectively with W _a, W _band W _ccorrespondence, and three ratio ε can be calculated according to formula (5), (6) and (7) ₁, ε ₂and ε ₃.In step 3) in, approximate gets ε _i=0.5, half classical prophesy value power spectrum n nearly _c(W) one-tenth peak position substitutes into formula (8) and calculates, and is tentatively separated, then step 4) in carry out second step calculating, thus obtain more accurate ratio ε _i.Research and a large amount of calculating show, for specific laser carrier-envelope phase Φ, ratio ε ₁, ε ₂and ε ₃along with the change of laser intensity is very little.Therefore, within the scope of very large laser intensity, ratio ε can be thought ₁, ε ₂and ε ₃substantially close.

The present invention calculates by two steps and accurately measures laser pulse population parameter, measuring method is an in-situ measuring method, do not need to do any change to the state of femto-second laser pulse to be measured, measurement result directly reflects the physical interconnection between parameters, and in real time, fast, high precision.The range of laser intensity can reach 4-5 the order of magnitude, and the relative accuracy of method is better than 0.1% for laser intensity, is better than 1% for other parameters, can be widely applied in scientific experiment and engineering survey.

Another object of the present invention is that the high accuracy data proposing the femto-second laser pulse population parameter that above-mentioned in-situ measuring method obtains is for Calibration Experiment system, the purposes of the overall target of assessment fs-laser system.These high accuracy datas are significant in scientific research and practical application.

Advantage of the present invention:

(1) with the pulse of x-ray measurement ultra-strong femto-second laser;

(2) photoelectron spectroscopy obtained from a measurement just can derive all parameters of femto-second laser pulse: intensity, pulse temporal width, carrier-envelope phase, pulse shape etc.;

(3) it is a kind of method of physics, does not need to do any hypothesis;

(4) it is a kind of analytic method, does not need time discrimination measurement, data fitting and iterative computation;

(5) it have fast, high precision (the theoretical prophesy value of relative accuracy, be better than 0.1% for laser intensity, other parameters are better than 1%), method is simple, measurement dynamic range large (laser intensity measurement range reaches several order of magnitude).

Accompanying drawing explanation

Fig. 1 is the schematic diagram of ultra-strong femto-second laser pulse population parameter in-situ measurement system of the present invention;

Fig. 2 is the photoelectron spectroscopy n (W) that the X-ray of one embodiment of the present of invention and laser pulse excite hydrogen atom to produce;

Fig. 3 is the photoelectron spectroscopy n ' (W) of the theory calculated with quantum mechanics method of one embodiment of the present of invention.

Embodiment

Below in conjunction with accompanying drawing, by specific embodiment, set forth the present invention further.

As shown in Figure 1, the ultra-strong femto-second laser pulse population parameter in-situ measurement system of the present embodiment comprises: psec or subpicosecond laser pulse 1, spectroscope 2, separation vessel 5, Laser pulse compression unit 8, first intert-gas atoms 4 and the second gas atom 11, first and second convergent mirror the 3 and 10, first to the 3rd catoptron 6,7 and 9 and photoelectron spectrograph 12; Wherein, psec or subpicosecond laser pulse 1 are split into two bundle laser after spectroscope 2; Wherein a branch of High-order Harmonic Generation and X-ray directly exciting the first intert-gas atoms 4 of the first valve A outgoing to produce forward emitted after the first convergent mirror 3; X-ray and laser pulse filter out laser after separation vessel, and the X-ray of arrowband wherein becomes the very little light beam of the diameter in z direction after the first catoptron 6; Spectroscope 2 divides the another beam of laser, after the second catoptron 7, enter Laser pulse compression unit 8, becomes the linearly polarized femto-second laser pulse that the cycle is to be measured less of polarised direction x; This pulse is coaxial in z direction with X-ray at the 3rd catoptron 9 place, conllinear mixes and transmits; Femto-second laser pulse focuses on through the second convergent mirror 10, jointly excites the second gas atom 11 of the second valve B outgoing with X-ray, produces photoelectron, measures its energy distribution at the polarised direction photoelectron spectrograph 12 of laser.Wherein, separation vessel 5 adopts beryllium window or other suitable materials; Second gas atom 11 is hydrogen atom.

Fig. 2 is the photoelectron spectroscopy n (W) that the X-ray of the present embodiment and laser pulse excite hydrogen atom to produce.The duration of femto-second laser pulse, the Strength Changes of X-ray is very little, can think continuous print; And values for spatial distribution change very little (Single-Intensity) SI of femto-second laser pulse, the maximal value of its intensity and the peak I of laser pulse.Shown in calculating chart 2, the parameter of power spectrum is as follows: laser intensity I=10 ¹⁴w/cm ², wavelength 800nm, pulse width τ _l=7.5fs, Φ=0 °, X-ray photons energy 135eV.X-transmitted intensity is set to 10 simply ⁸w/cm ², there is no special consideration, because the photoelectron counting rate in photoelectron spectroscopy and unit energy becomes simple proportional relation with X-transmitted intensity.

The ultra-strong femto-second laser pulse population parameter in-situ measuring method of the present embodiment comprises the following steps:

1) psec or subpicosecond laser pulse 1 are split into two bundle laser after spectroscope 2; Wherein a branch of High-order Harmonic Generation and X-ray directly exciting the first intert-gas atoms 4 of the first valve A outgoing to produce forward emitted after the first convergent mirror 3; X-ray and laser pulse filter out laser after separation vessel, and the X-ray of arrowband wherein becomes the very little light beam of the diameter in z direction after the first catoptron 6; Spectroscope 2 divides the another beam of laser, after the second catoptron 7, enter Laser pulse compression unit 8, becomes the linearly polarized femto-second laser pulse that the cycle is to be measured less of polarised direction x; This pulse is coaxial in z direction with X-ray at the 3rd catoptron 9 place, conllinear mixes and transmits;

2) femto-second laser pulse second convergent mirror 10 focuses on, with X-ray through jointly exciting the second gas atom 11, producing photoelectron, measuring its energy distribution at the polarised direction photoelectron spectrograph of laser, obtain photoelectron spectroscopy n (W), as shown in Figure 2;

3) lock the carrier-envelope phase Φ of femto-second laser pulse, Φ=0 °, from the photoelectron spectroscopy n (W) as shown in Figure 2 that measurement obtains, determine three peak position W _a, W _band W _c, with the energy value W ' of half At The Height of these peak positions _i=0.5n (W _j) be similar to the half classical prophesy value power spectrum n replacing photoelectron spectroscopy _c(W) one-tenth peak position, and calculate photoelectronic momentum off-set value, they are substituted into following formula calculate:

$\mathrm{\Φ}=\frac{\mathrm{\π}\ln (-\mathrm{\Δ}{p}_1/\mathrm{\Δ}{p}_2)}{\ln (\mathrm{\Δ}{p}_2/\mathrm{\Δ}{p}_3)},$

From three, formula (8) left side numerical value and population parameter (I, Φ, the τ of femto-second laser pulse can be calculated _l) namely tentatively separate (I, Φ, τ _l) ₁==(0.981 × 10 ¹⁴w/cm ², 3.691 °, 7.599fs);

4) with above-mentioned preliminary solution (I, Φ, τ _l) ₁for the photon energy of input parameter and known arrowband X-ray, calculate theoretical photoelectron spectroscopy n ' (W) with quantum mechanics method, and determine three peak value W from the photoelectron spectroscopy of this theory _a', W _b' and W _c', and calculate half classical prophesy value power spectrum n ' _c(W) one-tenth peak position W " ₁, W " ₂with W " ₃, thus calculate three relevant ratio (ε of prophesy value classical to half ₁, ε ₂, ε ₃) ₁: obtain (ε ₁, ε ₂, ε ₃) ₁=(46.7%, 41.4%, 30.9%), ε ₁, ε ₂and ε ₃value be marked on figure, then according to these ratio, the photoelectron spectroscopy n (W) obtained from initial measurement reads half classical prophesy value n _c(W) one-tenth peak position W ₁, W ₂and W ₃, and calculate photoelectronic momentum off-set value thus,

they are substituted into formula (8) again calculate, obtain exact solution (I, Φ, the τ of the population parameter of femto-second laser pulse _l) ₂=(0.99918 × 10 ¹⁴w/cm ²,-0.862 °, 7.565fs).

The femto-second laser pulse population parameter that measuring method of the present invention obtains and original input parameter (1014W/cm2,0 °, 7.5fs) differ minimum, and relative error is (-0.082% ,-0.2%, 0.8%).Therefore, the relative value of the theoretical precision of this method, is better than 0.1% for laser intensity, and other parameters are better than 1%.The error of measurement result is determined by experimental system.

Above-described embodiment is not intended to limit the present invention, any those skilled in the art, and without departing from the spirit and scope of the present invention, can make various conversion and amendment, therefore protection scope of the present invention defined depending on right.

Claims (4)

1. a ultra-strong femto-second laser pulse population parameter in-situ measurement system, it is characterized in that, described in-situ measurement system comprises: psec or subpicosecond laser pulse (1), spectroscope (2), separation vessel (5), Laser pulse compression unit (8), the first intert-gas atoms (4) and the second gas atom (11), the first and second convergent mirrors (3 and 10), photoelectron spectrograph (12) and optical path adjustment device; Wherein, psec or subpicosecond laser pulse (1) are split into two bundle laser after spectroscope (2); Wherein a branch of X-ray directly exciting the first intert-gas atoms (4) to produce forward emitted after the first convergent mirror (3); X-ray and laser pulse filter out laser after separation vessel (5), and arrowband X-ray wherein becomes the very little light beam of diameter; Spectroscope (2) divides the another beam of laser, and after entering Laser pulse compression unit (8), becomes the linearly polarized femto-second laser pulse that the cycle is to be measured less; Through optical path adjustment device, described optical path adjustment device comprises the first to the 3rd catoptron (6,7 and 9), and psec or subpicosecond laser pulse (1) are split into two bundle laser after spectroscope (2); Wherein a branch of X-ray directly exciting the first intert-gas atoms (4) to produce forward emitted after the first convergent mirror (3); X-ray and laser pulse filter out laser after separation vessel (5), and the X-ray of arrowband wherein becomes the very little light beam of the diameter of vertical direction after the first catoptron (6); Spectroscope (2) divides the another beam of laser, and enters Laser pulse compression unit (8) after the second catoptron (7), becomes the linearly polarized femto-second laser pulse that the cycle is to be measured less of parallel direction; Femto-second laser pulse to be measured the 3rd catoptron (9) place and X-ray in the vertical direction coaxial, conllinear mix and transmit; Femto-second laser pulse focuses on through the second convergent mirror (10), jointly excites the second gas atom (11) with X-ray, produces photoelectron, measures its energy distribution at the polarised direction photoelectron spectrograph (12) of laser.

2. in-situ measurement system as claimed in claim 1, it is characterized in that, described second gas atom (11) is intert-gas atoms or hydrogen atom.

3. a ultra-strong femto-second laser pulse population parameter in-situ measuring method, is characterized in that in-situ measuring method comprises the following steps:

1) psec or subpicosecond laser pulse are split into two bundle laser after spectroscope, wherein a branch of High-order Harmonic Generation and X-ray directly exciting the first intert-gas atoms generation forward emitted after the first convergent mirror, X-ray and laser pulse filter out laser after separation vessel, the X-ray of arrowband wherein becomes the very little light beam of diameter, spectroscope divides the another beam of laser, enter Laser pulse compression unit, become the linearly polarized femto-second laser pulse that the cycle is to be measured less, the femto-second laser pulse to be measured through optical path adjustment device is coaxial with X-ray at the 3rd catoptron place, conllinear mixing and transmission,

2) femto-second laser pulse focuses on through the second convergent mirror, jointly excites the second gas atom with X-ray, produces photoelectron, measures its energy distribution, obtain photoelectron spectroscopy n (W) at the polarised direction photoelectron spectrograph of laser;

3) lock the carrier-envelope phase Φ of femto-second laser pulse, from the photoelectron spectroscopy n (W) that measurement obtains, determine three peak position W _a, W _band W _c, with the energy value W' of half At The Height of these peak positions _i=0.5n (W _j) be similar to the half classical prophesy value power spectrum n replacing photoelectron spectroscopy _c(W) one-tenth peak position, and calculate photoelectronic momentum off-set value, ${\mathrm{\Δp}}_i=\sqrt{{{2W}^{\′}}_i}-\sqrt{{2W}_0},$ They are substituted into following formula calculate:

$\mathrm{\Φ}=\frac{\mathrm{\π}1n(-{\mathrm{\Δp}}_1/{\mathrm{\Δp}}_2)}{1n({\mathrm{\Δp}}_2/{\mathrm{\Δp}}_3)},$

From three, formula (1) left side numerical value and calculate population parameter (I, Φ, the τ of femto-second laser pulse _l), namely tentatively separate (I, Φ, τ _l) ₁, wherein, i ∈ (1,2,3), j ∈ (a, b, c), I are the intensity of femto-second laser pulse, and Φ is the carrier-envelope phase of laser pulse, τ _lfor Laser pulse time width, U _pfor photoelectron matter kinetic energy, for laser angular frequency, W ₀for photoelectronic just kinetic energy;

4) with above-mentioned preliminary solution (I, Φ, τ _l) ₁for the photon energy of input parameter and known arrowband X-ray, calculate theoretical photoelectron spectroscopy n'(W with quantum mechanics method), and determine three peak value W from the photoelectron spectroscopy of this theory _a', W _b' and W _c', and calculate the one-tenth peak position W of half classical prophesy value " ₁, W " ₂and W " ₃, thus calculate three relevant ratio (ε of prophesy value classical to half ₁, ε ₂, ε ₃) ₁, wherein ε ₁=n'(W " ₁)/n'(W _a'), ε ₂=n'(W " ₂)/n'(W _b'), ε ₃=n'(W " ₃)/n'(W _c'), then according to these ratio, the photoelectron spectroscopy n (W) obtained from initial measurement reads half classical prophesy value n _c(W) one-tenth peak position W ₁, W ₂and W ₃, and calculate photoelectronic momentum off-set value, they are substituted into formula (1) again calculate, obtain exact solution (I, Φ, the τ of the population parameter of femto-second laser pulse _l).

4. the high accuracy data of femto-second laser pulse population parameter that obtains of in-situ measuring method according to claim 3 is for Calibration Experiment system, the purposes of the overall target of assessment fs-laser system.