Post-Filament Intense Light Channels Formation During
Ultrashort Laser Pulses Propagation in Air
D V Sinitsyn1 , Yu E Geints2 , A A Ionin1 , D V Mokrousova1,3 , L V Seleznev1 , E S
Sunchugasheva1,3 , and A A Zemlyanov2
1
Quantum Radiophysics, Lebedev Physical Institute, 53, Leninski prospect, Moscow, Russia.
Contact Phone: +7(499)1358648
2
V.E. Zuev Institute of Atmospheric Optics, Siberian Branch RAS, 1, Academician Zuev square, Tomsk, Russia.
Contact Phone: +7(3822)492738
3
Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Russia.
Contact Phone: +7(495)4084554
Contact Email: [email protected]
High-power laser pulse propagates in transparent media in self-consistent regime known as filamentation [1]. After the termination of filamentation and plasma generation the laser pulse maintains its spatial
localization as elongated light structures, which are often referred to as the post-filament channels (PFCs).
These light channels possess sufficiently high intensity (∼1 TW/cm2 ) and lowered angular divergence in
comparison with the whole laser beam. The PFC can preserve millimeter-scale transverse sizes and high
intensity over kilometer-range distance that significantly increases a working area of high-power laser
operation [2]. The existence of such structure is sustained by competing processes of the self-focusing of
high intensity optical field inside a PFC and diffraction of peripheral beam areas surrounding the channel (energy reservoir) [2]. In this work, we partially answer the central question, whether a PFC like a
filament has some universal characteristics, which allows one to predict its spatial evolution regardless of
initial pulse parameters, and present experimental and numerical results that clearly show the influence
of radiation focusing and laser pulse energy on angular divergence and number of emerging PFCs. Experiments were carried out using 100 fs laser pulses at wavelength of 744 nm produced by Ti:Sa laser facility.
We discovered that the lowered angular divergence of PFC as compared to the whole beam is provided
by self-focusing via Kerr nonlinearity in the PFC area and is sustained by a specific spatial beam energy
profile exhibiting a system of concentric rings around each post-filament channel. PFC shows close to
linear growth of its size with the propagation distance, and its angular divergence decreases along with
pulse energy and focal distance growth. The minimum PFC divergence obtained in our experiments is
approximately 0.05 mrad for the loosest beam focusing (f = 295 cm) and pulse power tenfold higher than
the critical self-focusing power. The number of formed PFCs strongly depends on the beam focusing and
is higher for shorter focal distances.
Acknowledgements: The authors acknowledge the financial support by Russian Foundation for Basic Research (Grants: 14-28-02023, 14-02-00489, 14-22-02021), LPI Educational-Scientific Complex, and
Russian Science Foundation (Grants: 15-17-10001 16-17-10128).
References
[1] R W Boyd, S G Lukishova and Y R Shen (eds.), Self-focusing: Past and Present, Springer, Berlin
(2009)
[2] G Méchain, A Couairon, Y-B André, C D’Amico, M Franco, B Prade, S Tzortzakis, A Mysyrowicz
and R Sauerbrey, Appl. Phys. B 79, 379 (2004)