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

Alexander V. Bulgakov; Inam Mirza; Nadezhda M Bulgakova; V P Zhukov; Radek Machulka; Ondřej Haderka; Eleanor E B Campbell; Tomas Mocek

doi:10.1088/1361-6463/aac56a

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

Alexander V. Bulgakov, Inam Mirza, Nadezhda M Bulgakova, V P Zhukov, Radek Machulka, Ondřej Haderka, Eleanor E B Campbell, Tomas Mocek

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Abstract / Description of output

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 are 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.

Original language	English
Article number	25LT02
Number of pages	6
Journal	Journal of Physics D: Applied Physics
Early online date	16 May 2018
DOIs	https://doi.org/10.1088/1361-6463/aac56a
Publication status	Published - 1 Jun 2018

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10.1088/1361-6463/aac56a

20180517 E Campbell JPhysD-116422_Revised_ManuscriptAccepted author manuscript, 733 KBLicence: Creative Commons: Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND)

http://iopscience.iop.org/article/10.1088/1361-6463/aac56a

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title = "Initiation of air ionization by ultrashort laser pulses: Evidence for a role of metastable-state air molecules",

abstract = "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 are 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.",

author = "Bulgakov, {Alexander V.} and Inam Mirza and Bulgakova, {Nadezhda M} and Zhukov, {V P} and Radek Machulka and Ond{\v r}ej Haderka and Campbell, {Eleanor E B} and Tomas Mocek",

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doi = "10.1088/1361-6463/aac56a",

language = "English",

journal = "Journal of Physics D: Applied Physics",

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T1 - Initiation of air ionization by ultrashort laser pulses: Evidence for a role of metastable-state air molecules

AU - Bulgakov, Alexander V.

AU - Mirza, Inam

AU - Bulgakova, Nadezhda M

AU - Zhukov, V P

AU - Machulka, Radek

AU - Haderka, Ondřej

AU - Campbell, Eleanor E B

AU - Mocek, Tomas

PY - 2018/6/1

Y1 - 2018/6/1

N2 - 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 are 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.

AB - 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 are 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.

U2 - 10.1088/1361-6463/aac56a

DO - 10.1088/1361-6463/aac56a

M3 - Article

SN - 0022-3727

JO - Journal of Physics D: Applied Physics

JF - Journal of Physics D: Applied Physics

M1 - 25LT02

ER -

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

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