High harmonic generation in xear gas mixture is proposed. A method using expansion of the wave function in the basis of photonic and free atomic eigenstates is proposed for calculating the emission spectrum of an atom in a laser field. The mechanism relies on the destructive interference between harmonics. Phasematched highorder harmonic generation in ar gasfilled cell was investigated experimentally. Time frequency analysis of higher harmonic generation in a.
Generally, hhg only contains the oddorder harmonics for the orbital symmetry along the direction of laser. Frequency modulation of highorder harmonic generation in. Osa phase matching effects in high harmonic generation at. Here, i p is the ionization potential of an atom, and u p is the quiver energy of a free electron. Theory of high harmonic generation by low frequency laser.
The microscopic physics process of hhg is well understood by a threestep model. During highorder harmonic generation hhg, the driving and harmonic fields accumulate a phase difference as they propagate through the target. The sfa theory thus considers the interaction of an intense lowfrequency field. Corkum, theory of highharmonic generation by low frequency laser fields, phys. Avalanche effect and gain saturation in high harmonic generation. We have experimentally investigated the frequency modulation of highorder harmonics in an orthogonally polarized twocolor laser field consisting of a midinfrared 1800nm fundamental pulse and its second harmonic pulse. Theory of highharmonic generation by lowfrequency laser fields.
Time frequency analysis of high harmonic generation in a three color laser pulse 58 photon while recombination. Part 1 summarizes the field in two chapters, introducing the history and importance of the subject with simple concepts and basic equations. The theory recovers the classical interpretation of kulander ital et ital al. Pdf high harmonic generation by resonant plasmon field. High harmonic generation by resonant plasmon field enhancement article pdf available in nature 4537196. We present theoretical aspects of highharmonic generation hhg in this chapter. Smatrix approach to the problem of highharmonic generation. Highharmonic generation by focusing a femtosecond laser onto a gas is a wellknown method of producing coherent extremeultraviolet euv light 1,2,3. Theory of highharmonic generation by low frequency laser fields. Phasematched high order harmonic generation in ar gasfilled cell was investigated experimentally. Let us consider that the laser electric field et, linearly polarized in the z.
Theory of highharmonic generation by lowfrequency laser. Plasmon resonances are known to amplify the electromagnetic fields near metallic nanostructures, providing a promising scheme to generate extremeultraviolet harmonics using low power drivings. It is demonstrated that the high harmonic spectra can be finetuned as we slightly change the relative delay of the twocolor laser pulses. Theory of highorder harmonic generation by an elliptically polarized laser. We present a simple, analytic, and fully quantum theory of highharmonic generation by lowfrequency laser fields. Phasematched highorder harmonics by interaction of ar atoms. Highorder harmonic generation from xear gas mixture in. Highharmonic generation by field enhanced femtosecond. Corkum, theory of highharmonic generation by lowfrequency laser fields, phys. Perturbing laser field dependent high harmonic phase.
High harmonic generation physics 208a presentation october 11, 2004 tom allison uc berkeley. High harmonic generation hhg is an extremely nonlinear effect, where a medium is driven by a strong laser field, generating coherent broadband radiation with photon. Osa phase matching effects in high harmonic generation. To our knowledge, this is the lowest driving laser energy used to obtain. With sufficiently intense laser fields, the higher order terms give rise to fourier components of the polarization at harmonics of the laser frequency, creating. We obtained phasematched 27th order harmonic driven by a commercially available solidstate femtosecond laser system at 0. In high harmonic generation hhg, an increase in the period of the oscillating laser field leads. The necessity of using intense laser pulses is to make the rare gases ionized. Or is each photon a quantum superposition of all frequencies in the comb. Highharmonic generation by field enhanced femtosecond pulses in. High harmonic interferometry of the lorentz force in strong midinfrared laser fields article pdf available in new journal of physics 205 june 2016 with 117 reads how we measure reads. High harmonic generation hhg converts intense, short laser pulses to their. The theory recovers the classical interpretation of kulander et al. To our knowledge, this is the lowest driving laser energy used to obtain phasematched 27th order harmonic in a static.
Lorentz drift compensation in high harmonic generation in the soft. High harmonic generation in cutoff region is decreased in plateau region. Normally, the high order harmonic generation hhg only contains oddorder harmonics for the orbital symmetry along the direction of laser polarization. Highorder harmonic generation from xear gas mixture in the. Osa frequency modulation of highorder harmonic generation. High harmonic generation by focusing a femtosecond laser onto a gas is a wellknown method of producing coherent extremeultraviolet euv light 1,2,3. We have experimentally investigated the frequency modulation of high order harmonics in an orthogonally polarized twocolor laser field consisting of a midinfrared 1800nm fundamental pulse and its second harmonic pulse. Thus, to better understand and identify the generations of the evenorder harmonics, in fig. Atoms in intense laser fields is a wellorganized text. Highharmonic generation hhg is a coherent frequencyconversion process arising from gaseous atoms 1,2,3,4 or crystalline solids 5,6,7 when they are irradiated by an intense laser pulse. Phasematched highorder harmonics by interaction of ar. Pdf high harmonic interferometry of the lorentz force in.
Smatrix approach to the problem of highharmonic generation in the field of intense laser wave. Theory of high harmonic generation by low frequency laser fields. However, if the halfwave symmetry of the driving field is broken i. On the quantumoptical nature of high harmonic generation arxiv. High harmonic generation hhg is a coherent extremeultraviolet xuv light source.
1530 1580 799 1277 1208 419 603 1161 1174 1289 352 632 62 861 837 1269 299 132 1032 242 687 1584 56 576 1246 582 715 577 635 1086 533 617 686 58 915