CN100573066C - A kind of method of measuring attosecond pulse width - Google Patents

Abstract

A kind of method of measuring attosecond pulse width may further comprise the steps: 1) will be focused on the rare gas by the Shu Guang that closes that laser and chirped pulse constitute, form the photoelectron signal that comprises chirped pulse information through single photon ionization; 2) gather photoelectron signal, obtain photoelectron spectrum; 3) utilize the relation formula of photoelectron spectrum and chirped pulse that photoelectron spectrum is analyzed, obtain the pulsewidth of chirped pulse.The present invention sets up the direct relation between photoelectron spectrum and the chirped pulse, obtains the pulsewidth of chirped pulse by measuring light electronics spectrum width, and this scheme has been simplified measuring method, has avoided a large amount of The Fitting Calculation, and measurement result is accurate.

Description

A kind of method of measuring attosecond pulse width

Technical field

The present invention relates to a kind of method of measuring attosecond pulse width.

Background technology

Along with the development of ultrafast technology, intense laser pulse constantly shortens, and its pulsewidth has reached the photoperiod magnitude.This few-cycle laser pulse (about 5 femtoseconds) makes the more generation of short pulse that a new breakthrough arranged again with atomic interaction, has realized single chirped pulse.Chirped pulse can be realized the real-time measurement and the control of electron motion in atom and the molecule, thereby has attracted increasing concern in recent years.Single chirped pulse has been used to observe the evolutionary process of intratomic stratum nucleare, the generation of electron tunnel ionization and control higher hamonic wave.All these are used and all depended on single chirped pulse, and are therefore extremely important for the measurement of chirped pulse.

At present, the method for measurement chirped pulse roughly has following two kinds of schemes: (1) adopts autocorrelation technique; (2) adopt cross-correlation techniques.Wherein,, and, measure required non-linear phenomena and lack, still face many difficulties so use autocorrelation method to measure single chirped pulse in the extreme ultraviolet zone because the intensity of chirped pulse is lower.Using relevant interleaving techniques is the commonplace method of measuring single chirped pulse at present, this method uses femtosecond laser as the reference time, the pulsewidth that obtains chirped pulse with the energy jitter or the broadening of phase change by the match photoelectron spectrum, this method is very complicated, not only require a series of photoelectron spectrum, and need a large amount of The Fitting Calculation.Up to the present, the direct quantum relation between photoelectron spectrum and the single chirped pulse is not also set up.

Summary of the invention

The object of the present invention is to provide a kind of method of measuring attosecond pulse width, simple to operate, calculated amount is little, the measuring accuracy height.

A kind of method of measuring attosecond pulse width may further comprise the steps:

(4) will focus on the rare gas by the Shu Guang that closes that laser and chirped pulse constitute, form the photoelectron signal that comprises chirped pulse information through single photon ionization;

(5) gather photoelectron signal, obtain photoelectron spectrum;

(6) utilize the relation formula of photoelectron spectrum and chirped pulse that photoelectron spectrum is analyzed, obtain the pulsewidth of chirped pulse;

Described relation formula is specially: $\mathrm{\ΔE}=2\sqrt{8U_p{L}_0}\sin ({\mathrm{\ω}}_0{\mathrm{\τ}}_x/2)\≈\sqrt{8U_p{L}_0}{\mathrm{\ω}}_0{\mathrm{\τ}}_x,$ Formula adopts atomic unit, and wherein, Δ E is the photoelectron spectroscopy spectrum width, the ponderomotive force energy $U_p=\frac{e{E}^2}{4{{\mathrm{\ω}}_0}^2},$ E is the laser field amplitude, and e is an electron charge, ω ₀Be laser field angular frequency, τ _xBe attosecond pulse width, the zero energy L of electronics ₀=p-I ₀, p is the angular frequency of chirped pulse, I ₀Ionization energy for atom.

The present invention sets up the direct relation between photoelectron spectrum and the chirped pulse, obtains the pulsewidth of chirped pulse by measuring light electronics spectrum width.This scheme has been simplified measuring method, only needs to measure a photoelectron spectrum, has avoided The Fitting Calculation in addition, and measuring method is accurately simple more.

Description of drawings

Fig. 1 is a principle of the invention synoptic diagram;

Fig. 2 is photoelectron spectrum width and the attosecond pulse width graph of a relation and the photoelectron spectroscopy figure of example one correspondence, Fig. 2 (a) photoelectron spectrum width and attosecond pulse width graph of a relation, and Fig. 2 (b) is photoelectron spectroscopy figure;

Fig. 3 is spectrum width and Ah second's pulsewidth graph of a relation of example two correspondences.

Concrete embodiment

Fig. 1 is a principle of the invention synoptic diagram, and wherein dotted line is represented laser field, and solid line is represented chirped pulse, and the invention will be further described below in conjunction with example and accompanying drawing.

Example one

The rare gas that adopts is helium, and laser intensity is 8 * 10 ¹³Wcm ^-2, wavelength is 800nm.Chirped pulse intensity is 5 * 10 ¹²Wcm ^-2, (chirped pulse) angular frequency is 3.42a.u..Laser field changes into photoelectron signal by single photon ionization with chirped pulse, gathers the photoelectron spectrum that photoelectron signal obtains comprising chirped pulse information.Set up the accurate relation between photoelectron spectrum and the chirped pulse, shown in above-mentioned relation formula, what use in this formula is atomic unit, and wherein Δ E represents the spectrum width of photoelectron spectroscopy, the ponderomotive force energy $U_p=\frac{e{E}^2}{4{{\mathrm{\ω}}_0}^2},$ E is an electric field amplitude, ω ₀Be the angular frequency of laser field, e is an electron charge, τ _xBe the pulsewidth of chirped pulse, the zero energy L of electronics ₀=p-I ₀, p is the angular frequency of chirped pulse, I ₀Ionization energy for atom.In order to verify correctness of the present invention, use is simultaneously separated the time-dependent Schrodinger equation measurement and is used for recording the result relatively with the present invention, Fig. 2 is Ah second's energy spectrogram and photoelectron spectrum width and attosecond pulse width graph of a relation, wherein, Fig. 2 (a) is by separating the photoelectron spectrogram that time-dependent Schrodinger equation obtains, and dotted line among Fig. 2 (b) and solid line are respectively to obtain Ah second's pulsewidth and photoelectron spectrum width graph of a relation by the method for separating among time-dependent Schrodinger equation and the present invention.

The curve of representing with reference to solid line among the figure 2 (b) when measuring a certain photoelectron spectrum width, then can obtain corresponding attosecond pulse width by curve.Such as, measuring the photoelectron spectrum width in the experiment is 37.5eV, corresponding to C point among Fig. 2 (b), then reading Ah second's pulsewidth among the figure that can be obtained by relation formula is 300as.In order to check the accuracy of this method, we use by separating time-dependent Schrodinger equation and simulate and obtain the photoelectron spectrogram, shown in Fig. 2 (a), when spectrum width is 37.5eV (halfwidth of photoelectron spectrum), then corresponding to the spectrum width between 2 of A, the B shown in Fig. 2 (a), can draw by separating the time-dependent Schrodinger equation Simulation result, its corresponding chirped pulse is 300as.Hence one can see that, and it is goodish that the result that two kinds of diverse ways obtain meets, and the correctness of this method has been described.Compare and separate time-dependent Schrodinger equation, the present invention's operation is simpler, and calculated amount is littler.

Example two

The rare gas that adopts is helium, and laser intensity is 5 * 10 ¹³Wcm ^-2, wavelength is 1600nm, chirped pulse intensity is 5 * 10 ¹²Wcm ^-2, (chirped pulse) angular frequency is 3.42a.u.Laser field changes into photoelectron signal by single photon ionization with chirped pulse, and final photoelectron spectrum has been inherited the information of chirped pulse.Obtain the curve represented as solid line among Fig. 3 according to relation formula, dotted line among Fig. 3 and solid line are respectively photoelectron spectrogram and Ah second's pulsewidth and the photoelectron spectrum width graphs of a relation that is obtained by the method for separating among time-dependent Schrodinger equation and the present invention, the photoelectricity spectrum width that measures in experiment then can obtain corresponding attosecond pulse width by Fig. 3 curve.By contrast, two kinds of unanimities as a result that distinct methods obtains.

Claims (1)

1, a kind of method of measuring attosecond pulse width may further comprise the steps:

(1) will focus on rare gas by the Shu Guang that closes that laser and chirped pulse constitute, form the photoelectron signal that comprises chirped pulse information through single photon ionization;

(2) gather photoelectron signal, obtain photoelectron spectroscopy;

(3) utilize the relation formula of photoelectron spectroscopy and chirped pulse that photoelectron spectroscopy is analyzed, obtain the pulsewidth of chirped pulse;

Described relation formula is specially: $\mathrm{\ΔE}=2\sqrt{8U_p{L}_0}\sin ({\mathrm{\ω}}_0{\mathrm{\τ}}_x/2)\≈\sqrt{8U_p{L}_0}{\mathrm{\ω}}_0{\mathrm{\τ}}_x,$ Formula adopts atomic unit, and wherein, Δ E is the photoelectron spectroscopy spectrum width, the ponderomotive force energy $U_p=\frac{e{E}^2}{4{{\mathrm{\ω}}_0}^2},$ E is the laser field amplitude, and e is an electron charge, ω ₀Be laser field angular frequency, τ _xBe attosecond pulse width, the zero energy L of electronics ₀=p-I ₀, p is the angular frequency of chirped pulse, I ₀Ionization energy for atom.

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