Vol. 39, issue 01, article # 3

Abstract:

The results of complex studies of filamentation of high-power femtosecond laser pulses in experiments where a localized air layer with a randomly inhomogeneous refractive index (artificial turbulent layer) is created at the beginning of the propagation path are discussed. It is shown that the technique of forced chaotic modulation (power stochastization) of a radiation beam, which initiates inhomogeneities in the transverse energy structure of laser radiation, causes the splitting of an original beam into many high-intensity light subbeams (channels) due to strong optical nonlinearity of the air medium. These channels are characterized by high intensity and stability along significant distances. The segmentation of the radiation by a turbulent layer multiply increases the number of high-intensity optical channels, which arise during propagation of a 2.5-cm beam of a Ti:Sapphire laser with a wavelength of 800 nm and power of up to 150 GW in air. The characteristic intensity of these optical channels is high enough for two-photon absorption in a volume of colored (rhodamine or uranine with a concentration of 0.4 g/l) water aerosol microparticles, created at the end of a 100-m optical path, which, in turn, almost doubles the fluorescence signal from the particles recorded by the lidar scheme. In addition, it was determined that a localized turbulent layer created at the beginning of an optical path enables a multiple enhancement of the efficiency of low-frequency (THz) electromagnetic radiation generation from laser filamentation region.

Keywords:

femtosecond laser pulse, turbulence, laser filamentation, plasma, aerosol, two-photon-excited fluorescence, angular distribution, THz radiation generation

References:

1. Self-focusing: Past and Present. Fundamentals and Prospects / R.W. Boyd, S.G. Lukishova, Y.R. Shen (eds.). New York: Springer-Verlag, 2009. 605 p. DOI: 10.1007/978-0-387-34727-1.
2. Couairon A., Myzyrowicz A. Femtosecond filamentation in transparent media // Phys. Reports. 2007. V. 441. P. 47–189. DOI: 10.1016/j.physrep.2006.12.005.
3. Bergé L., Skupin S., Nuter R., Kasparian J., Wolf J.-P. Ultrashort filaments of light in weakly-ionized, optically-transparent media // Rep. Prog. Phys. 2007. V. 70. P. 1633. DOI: 10.1088/0034-4885/70/10/R03.
4. Kandidov V.P., Shlenov S.A., Kosareva O.G. Filamentatsiya moshchnogo femtosekundnogo lazernogo izlucheniya // Kvant. elektron. 2009. V. 39, N 3. P. 205–228.
5. Chin S.L. Femtosecond Laser Filamentation. New York: Springer-Verlag, 2010. 130 p. DOI: 10.1007/978-1-4419-0688-5.
6. Chekalin S.V., Kandidov V.P. Ot samofokusirovki svetovyh puchkov – k filamentatsii lazernyh impul'sov // Uspekhi fiz. nauk. 2013. V. 183, N 2. P. 133–152.
7. Woste L., Wedekind C., Wille H., Rairoux P., Stein B., Nikolov S., Werner Ch., Niedermeier S., Schillinger H., Sauerbrey R. Femtosecond atmospheric lamp // Laser Optoelektron. 1997. V. 29. P. 51–53.
8. Kasparian J., Rodriguez M., Mejean G., Yu J., Salmon E., Wille H., Bourayou R., Frey S., Andre Y.-B., Mysyrowicz A., Sauerbrey R., Wolf J.-P., Wöste L. White-light filaments for atmospheric analysis // Science. 2003. V. 301. P. 61. DOI: 10.1126/science.1085020.
9. Daigle J.-F., Mejean G., Liu W., Theberge F., Xu H.L., Kamali Y., Bernhardt J., Azarm A., Sun Q., Mathieu P., Roy G., Simard J.-R., Chin S.L. Long range trace detection in aqueous aerosol using remote filament-induced breakdown spectroscopy // Appl. Phys. B. 2007. V. 87, N 4. P. 749–754. DOI: 10.1007/s00340-007-2642-6.
10. Bergé L., Kaltenecker K., Engelbrecht S., Nguyen A., Skupin S., Merlat L., Fischer B., Zhou B., Thiele I., Jepsen P.U. Terahertz spectroscopy from air plasmas created by two-color femtosecond laser pulses: The ALTESSE project // Europhys. Let. 2019. V. 126. P. 24001. DOI: 10.1209/0295-5075/126/24001.
11. Bai K., Gou Y., Peng X.-Y. Terahertz beam array generated by focusing two-color-laser pulses into air with a microlens array // AIP Advances. 2022. V. 12. P. 095113. DOI: 10.1063/5.0098771.
12. Méchain G., Couairon A., André Y.-B., D’Amico C., Franco M., Prade B., Tzortzakis S., Mysyrowicz A., Sauerbrey R. Long-range self-channeling of infrared laser pulses in air: A new propagation regime without ionization // Appl. Phys. B. 2004. V. 79, N 3. P. 379–382. DOI: 10.1007/s00340-004-1557-8.
13. Daigle J.-F., Kosareva O., Panov N., Wang T.-J., Hosseini S., Yuan S., Roy G., Chin S.L. Formation and evolution of intense, post-filamentation, ionization-free low divergence beams // Opt. Commun. 2011. V. 284, N 14. P. 3601–3606. DOI: 10.1016/j.optcom.2011.03.077.
14. Geints Yu.E., Ionin A.A., Mokrousova D.V., Seleznev L.V., Sinitsyn D.V., Sunchugasheva E.S., Zemlyanov A.A. High intensive light channel formation in the post-filamentation region of ultrashort laser pulses in air // J. Opt. 2016. V. 18. P. 095503. DOI: 10.1088/2040-8978/18/9/095503.
15. Apeksimov D.V., Geints Yu.E., Zemlynov A.A., Kabanov A.M., Oshlakov V.K., Petrov A.V., Matvienko G.G. Controlling TW-laser pulse long-range filamentation in air by a deformable mirror // Appl. Opt. 2018. V. 57, N 34. 10 p. DOI: 10.1364/AO.99.099999.
16. Apeksimov D.V., Bulygin A.D., Geints Yu.E., Kabanov A.M., Khoroshaeva E.E., Petrov A.V. Statistical parameters of femtosecond laser pulse post-filament propagation on 65 m air path with localized optical turbulence // J. Opt. Soc. Am. B. 2022. V. 39, N 12. P. 3237–3246. DOI: 10.1364/JOSAB.473298.
17. D’Amico C., Houard A., Franco M., Prade B., Mysyrowicz A., Couairon A., Tikhonchuk V.T. Conical Forward THz Emission from Femtosecond-Laser-Beam Filamentation in Air // Phys. Rev. Lett. 2007. V. 98. P. 235002. DOI: 10.1103/PHYSREVLETT.98.235002.
18. Clough B., Liu J., Zhang X.-C. All air-plasma terahertz spectroscopy // Opt. Lett. 2011. V. 36. P. 2399–2401. DOI: 10.1364/OL.36.002399.
19. Couairon A., Mysyrowicz A. Femtosecond filamentation in air. Progress in Ultrafast Intense Laser Science. Berlin, Heidelberg: Springer, 2006. V. I. P. 235–258.