1. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Modeling propagation of femtosecond laser pulses in ionized gas media Valer TOSA National Intitute for R&D of Isotopic and Molecular Technology, Cluj-Napoca, ROMANIA

2. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 High-order harmonics Intense fs laser Gas jet atom electron Laser X-ray Signal process Soft X-ray spectrometer X-ray filter X-ray CCD X-ray CCD 80 90 100110 120 130 1251151059585 High-order harmonics ( Å ) H65H75H85H95 High order harmonics generation (HHG)

3. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Modeling laser field propagation:

4. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Model capabilities uses experimentally measured parameters (focusing conditions, pulse energy, duration) includes different focusing configurations (gaussian, supergaussian, truncated gaussian, bessel-gauss) may account for frequency chirp of the pulse CEP can be an input parameter additional time-frequency analysis (post-processing) Recent developments simultaneous propagation of two (three) fields including double (multiple) ionization to account for high intensity cases

5. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Example results (1)

6. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Example results (2)

7. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Example results (3)

8. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011

9. Propagation effect in time domain V. Tosa et al. PRA 71, 063807 PRA 71, 063808

10. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Propagation effect in frequency domain

11. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Coherent superposition of harmonic fields (1) Formation of far field from constructive interference of near fields V. Tosa et al, PRA 79, 043828 (2009)

12. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 (a) Harmonic near fields contributing to the attosecond pulse at t=−2T 0 and different r distances from the axis. (b) The normalized envelopes of the corresponding field intensities. Coherent superposition of harmonic fields (2) V. Tosa et al, PRA 79, 043828 (2009)

13. ELI-NP: The Way Ahead, Bucharest, 10-12 March 2011 Conclusions: - Propagation of laser pulses in gaseous ionizing media can be characterized by a numerical model - Two or more pulses can be described in simultaneous propagation - Measured quantities can be used as input - Methods to describe coherent field superposition are available - The above instruments could be used to model the process of coherent beam combining in ELI-NP Project (?)