Initiation of air ionization by ultrashort laser pulses: evidence for a role of metastable-state air molecules

0492634 - FZÚ 2019 RIV GB eng J - Článek v odborném periodiku
Bulgakov, Alexander - Mirza, M. Inam - Bulgakova, Nadezhda M. - Zhukov, Vladimir - Machulka, R. - Haderka, O. - Campbell, E.E.B. - Mocek, Tomáš
Initiation of air ionization by ultrashort laser pulses: evidence for a role of metastable-state air molecules.
Journal of Physics D-Applied Physics. Roč. 51, č. 25 (2018), s. 1-6, č. článku 25LT02. ISSN 0022-3727. E-ISSN 1361-6463
Grant CEP: GA MŠMT LO1602; GA ČR GA16-12960S; GA MŠMT EF15_006/0000674; GA MŠMT EF15_003/0000445
Grant ostatní: OP VVV - HiLASE-CoE(XE) CZ.02.1.01/0.0/0.0/15_006/0000674; OP VVV - BIATRI(XE) CZ.02.1.01/0.0/0.0/15_003/0000445
Institucionální podpora: RVO:68378271
Klíčová slova: femtosecond laser pulses * laser-induced air breakdown * multiphoton ionization * metastable-state molecules
Obor OECD: Optics (including laser optics and quantum optics)
Impakt faktor: 2.829, rok: 2018

Transmission measurements for femtosecond laser pulses focused in air with spectral analysis of emission from the focal region have been carried out for various pulse energies and air pressures. The air breakdown threshold and pulse attenuation due to plasma absorption arc evaluated and compared with calculations based on the multiphoton ionization model. The plasma absorption is found to depend on the pulse repetition rate and is considerably stronger at 1 kHz than at 1-10 Hz. This suggests that accumulation of metastable states of air molecules plays an important role in initiation of air breakdown, enhancing the ionization efficiency at high repetition rates. Possible channels of metastable-state-assisted air ionization and the role of the observed accumulation effect in laser material processing are discussed.
Trvalý link: http://hdl.handle.net/11104/0286084