We numerically simulate the propagation of high-intensity laser pulses in helium to investigate the role of nonlinear effects in gas-cell high-harmonics experiments. An aperture located before the focusing lens is also included in the simulation. Numerical results for the radial fluence profile as a function of axial position, as well as for the spectral shift and ionization levels, agree with experimental observations. The simulations confirm that a significant Kerr effect is not required to generate the observed double focus in the fluence. The beam simulation also permits an investigation of high-harmonic phase matching. Most of the harmonic energy is seen to come from the forward portion of the laser pulse, whereas the latter portion gives rise to the incidental double laser focusing. Good phase matching for the harmonics arises in large measure from a balance between the linear phase delay of the neutral atoms and the Gouy shift, which is elongated and nearly linearized when the aperture is partially closed on the beam.

© 2008 Optical Society of America

1. J. C. Painter, M. Adams, N. Brimhall, E. Christensen, G. Giraud, N. Powers, M. Turner, M. Ware, and J. Peatross, "Direct observation of laser filamentation in high-order harmonic generation," Opt. Lett. 31, 3471-3473 (2006). [CrossRef] [PubMed]
2. N. Brimhall, J. C. Painter, N. Powers, G. Giraud, M. Turner, M. Ware, and J. Peatross, "Measured laser-beam evolution during high-order harmonic generation in a semi-infinite gas cell," Opt. Express 15, 1684-1689 (2007). [CrossRef] [PubMed]
3. V. Tosa and C. H. Nam, "Comment on ‘Direct observation of laser filamentation in high-order harmonic generation’," Opt. Lett. 32, 2707-2708 (2007). [CrossRef] [PubMed]
4. M. Turner, N. Brimhall, M. Ware, and J. Peatross, "Reply to comment on ‘Direct observation of laser filamentation in high-order harmonic generation’," Opt. Lett. 32, 2709-2710 (2007). [CrossRef]
5. A. Chiron, B. Lamouroux, R. Lange, J. F. Ripoche, M. Franco, B. Prade, G. Bonnaud, G. Riazuelo, and A. Mysyrowicz, "Numerical simulations of the nonlinear propagation of femtosecond optical pulses in gases," Eur. Phys. J. D 6, 383-396 (1999). [CrossRef]
6. S. Carusotto, E. Iacopini, E. Polacco, F. Scuri, G. Stefanini, and E. Zavattini, "Measurement of the Kerr constant of He, A, O2, H2, and D2," Nuovo Cimento 5D, 328-338 (1985). [CrossRef]
7. M. Ammosov, N. Delone, and V. Krainov, "Tunnel ionization of complex atoms and of atomic ions in an alternating electromagnetic field," Sov. Phys. JETP 64, 1191-1194 (1986).
8. S. L. Chin, S. A. Hosseini, W. Liu, Q. Luo, F. Theberge, N. Akozbek, A. Becker, V. P. Kandidov, O. G. Kosareva, and H. Schroeder, "The propagation of powerful femtosecond laser pulses in optical media: physics, applications, and new challenges," Can. J. Phys. 83, 863-905 (2005). [CrossRef]
9. H. T. Kim, I. J. Kim, V. Tosa, Y. S. Lee, and C. H. Nam, "High brightness harmonic generation at 13 nm using self-guided and chirped femtosecond laser pulses," Appl. Phys. B 78, 863-867 (2004). [CrossRef]
10. V. Tosa, E. Takahashi, Y. Nabekawa, and K. Midorikawa, "Generation of high-order harmonics in a self-guided beam," Phys. Rev. A 67, 063817 (2003). [CrossRef]
11. M. Lewenstein, P. Salieres, and A. L’Huillier, "Phase of the atomic polarization in high-order harmonic generation," Phys. Rev. A 62, 4747-4754 (1995). [CrossRef]
12. B. L. Henke, E. M. Gullikson, and J. C. Davis, Atomic Data and Nuclear Tables, (Academic, San Diego, 1993) Vol. 54; see http://henke.lbl.gov/optical constants/.
13. J. Sutherland, E. Christensen, N. Powers, S. Rhynard, P. Painter, and J. Peatross, "High harmonic generation in a semi-infinite gas cell," Opt. Express 12, 4430-4436 (2004). [CrossRef] [PubMed]
14. S. Kazamias, F. Weihe, D. Douillet, C. Valentin, T. Planchon, S. Sebban, G. Grillon, F. Auge, D. Hulin, and P. Balcou, "High order harmonic generation optimization with an apertured laser beam," Eur. Phys. J. D 21, 353-359 (2002). [CrossRef]

Appl. Phys. B

• H. T. Kim, I. J. Kim, V. Tosa, Y. S. Lee, and C. H. Nam, "High brightness harmonic generation at 13 nm using self-guided and chirped femtosecond laser pulses," Appl. Phys. B 78, 863-867 (2004). [CrossRef]

Can. J. Phys.

• S. L. Chin, S. A. Hosseini, W. Liu, Q. Luo, F. Theberge, N. Akozbek, A. Becker, V. P. Kandidov, O. G. Kosareva, and H. Schroeder, "The propagation of powerful femtosecond laser pulses in optical media: physics, applications, and new challenges," Can. J. Phys. 83, 863-905 (2005). [CrossRef]

Eur. Phys. J. D

• S. Kazamias, F. Weihe, D. Douillet, C. Valentin, T. Planchon, S. Sebban, G. Grillon, F. Auge, D. Hulin, and P. Balcou, "High order harmonic generation optimization with an apertured laser beam," Eur. Phys. J. D 21, 353-359 (2002). [CrossRef]
• A. Chiron, B. Lamouroux, R. Lange, J. F. Ripoche, M. Franco, B. Prade, G. Bonnaud, G. Riazuelo, and A. Mysyrowicz, "Numerical simulations of the nonlinear propagation of femtosecond optical pulses in gases," Eur. Phys. J. D 6, 383-396 (1999). [CrossRef]

Nuovo Cimento

• S. Carusotto, E. Iacopini, E. Polacco, F. Scuri, G. Stefanini, and E. Zavattini, "Measurement of the Kerr constant of He, A, O2, H2, and D2," Nuovo Cimento 5D, 328-338 (1985). [CrossRef]

Opt. Express

• N. Brimhall, J. C. Painter, N. Powers, G. Giraud, M. Turner, M. Ware, and J. Peatross, "Measured laser-beam evolution during high-order harmonic generation in a semi-infinite gas cell," Opt. Express 15, 1684-1689 (2007). [CrossRef] [PubMed]
• J. Sutherland, E. Christensen, N. Powers, S. Rhynard, P. Painter, and J. Peatross, "High harmonic generation in a semi-infinite gas cell," Opt. Express 12, 4430-4436 (2004). [CrossRef] [PubMed]

Opt. Lett.

• J. C. Painter, M. Adams, N. Brimhall, E. Christensen, G. Giraud, N. Powers, M. Turner, M. Ware, and J. Peatross, "Direct observation of laser filamentation in high-order harmonic generation," Opt. Lett. 31, 3471-3473 (2006). [CrossRef] [PubMed]
• V. Tosa and C. H. Nam, "Comment on ‘Direct observation of laser filamentation in high-order harmonic generation’," Opt. Lett. 32, 2707-2708 (2007). [CrossRef] [PubMed]
• M. Turner, N. Brimhall, M. Ware, and J. Peatross, "Reply to comment on ‘Direct observation of laser filamentation in high-order harmonic generation’," Opt. Lett. 32, 2709-2710 (2007). [CrossRef]

Phys. Rev. A

• V. Tosa, E. Takahashi, Y. Nabekawa, and K. Midorikawa, "Generation of high-order harmonics in a self-guided beam," Phys. Rev. A 67, 063817 (2003). [CrossRef]
• M. Lewenstein, P. Salieres, and A. L’Huillier, "Phase of the atomic polarization in high-order harmonic generation," Phys. Rev. A 62, 4747-4754 (1995). [CrossRef]

Sov. Phys. JETP

• M. Ammosov, N. Delone, and V. Krainov, "Tunnel ionization of complex atoms and of atomic ions in an alternating electromagnetic field," Sov. Phys. JETP 64, 1191-1194 (1986).

Other

• B. L. Henke, E. M. Gullikson, and J. C. Davis, Atomic Data and Nuclear Tables, (Academic, San Diego, 1993) Vol. 54; see http://henke.lbl.gov/optical constants/.

Click here to see a list of articles that cite this paper

Multimedia

Related Journal Articles

• Breakdown of the slowly varying envelope approximation in the self-focusing of ultrashort pulses (OL)
• Backward supercontinuum emission from a filament generated by ultrashort laser pulses in air (OL)
• Frequency-resolved optical gating and single-shot spectral measurements reveal fine structure in microstructure-fiber continuum (OL)
• Spectral shift of femtosecond pulses in nonlinear quadratic PPSLT Crystals (OE)
• Control of the collapse distance in atmospheric propagation (OE)

Related Conference Papers

• Optical light bullets in a pure Kerr medium
• First observation of discrete modulational instability in AlGaAs waveguide arrays
• Quantum computation with femtosecond photon echo
• Quantum computation with femtosecond photon echo
• Electron Density of the Femtosecond Optical Filament in Air
• Electron Density of the Femtosecond Optical Filament in Air
• Dispersive Wave Emission by Mid-IR Filaments in Solids