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49THz-O-8
Angular distribution of THz radiation from clustered plasma and enhancing of THz emission intensity
N. Kuzechkin1,2, A. Balakin1,2, M. Dzhidzhoev1, V. Gordienko1, I. Ivanov1, T. Semenov3, A. Shkurinov1,2
1Lomonosov Moscow State University, Faculty of Physics & International Laser Centre, Moscow, Russian Federation
2Russian Academy of Sciences, Institute on Laser and Information Technologies, Branch of the FSRC "Crystallography and Photonics", Shatura, Russian Federation 3Russian Academy of Sciences, FSRC "Crystallography and Photonics", Moscow, Russian Federation
Interaction of intense laser pulses with the gas-cluster targets results in fairly efficient generation of terahertz radiation. Some studies of such generation were carried out in several experimental and theoretical works [1] - [5]. However the current state of the problem of THz generation in clustered plasma indicates the necessity of further studies for obtaining complete and detailed theoretical interpretation of the experimental effects presented in [1] - [4] and for enhancement of optical to THz conversion efficiency. For example, in [5], it was concluded on the basis of theoretical analysis, that low-frequency radiation from clustered plasma can aquire dipole character under certain conditions of cluster excitation, in contrast with quadrupole radiation observed in [1],[2],[4].
In this work we present the results of experimental studies of the generation of THz radiation during the interaction of intense laser pulses with cluster beams. The basic scheme of the experimental setup is described in detail in our previous paper [3], and for the present study this setup was supplemented by the special module to provide a possibility of measurement of the angular distribution of THz radiation power. Femtosecond laser radiation was focused on the cluster targets differing in size, concentration and internal atomic density of clusters constituting them. We used argon and freon (CF2O2) cluster beams. Parameters of the cluster beams were calculated by numerical simulation and indirectly confirmed in the experiment of Rayleigh scattering measurement.The effect of the polarization state of the laser pulse on the THz emission was studied. Under various experimental conditions, we performed measurements of the angular distribution of the THz radiation power in the horizontal plane. We have found that under certain conditions the polarization state of the exciting laser pulse can influence the efficiency of the generation of THz radiation, which was not observed in previous studies.
Figure 1 demonstrates the effect of laser polarization on THz emission from freon clusters. Also we observed that the THz radiation power from argon clusters at a distance of 13.5 mm below the nozzle edge is rather more than at a distance 1.5 mm away. The results of our numerical simulation has demonstrated that ratio between argon monomers, small and large clusters fractions significantly different at these two positions. We made an attempt of theoretical explanation of the phenomena described above.
This study was supported by RFBR Grant № 17-02-01217.
Laser polarization:
• circular
• linear
0 20 40 60 80 100 120 140 160
angle, degree
Fig. 1.
References
[1] T. Nagashima, H. Hirayama, K. Shibuya, M. Hangyo, M. Hashida, S. Tokita, and S. Sakabe. Terahertz pulse radiation from argon clusters irradiated with intense femtosecond laser pulses. Opt. Exp. 17, 8907 (2009).
[2] F. Jahangiri, M. Hashida, T. Nagashima, S. Tokita, M. Hangyo, and S. Sakabe. Intense terahertz emission from atomic cluster plasma produced by intense femtosecond laser pulses. Appl. Phys. Lett. 99, 261503 (2011).
[3] A.V. Balakin, M.S. Dzhidzhoev, V.M. Gordienko, M.N. Esaulkov, I.A. Zhvaniya, K.A. Ivanov, I.A. Kotelnikov, N.A. Kuzechkin, I.A. Ozheredov, V.Y. Panchenko, A.B. Savel'ev, M.B. Smimov, P.M. Solyankin, A.P. Shkurinov. Interaction of High-Intensity Femtosecond Radiation With Gas Cluster Beam: Effect of Pulse Duration on Joint Terahertz and X-Ray Emission. IEEE Trans. Terahertz Sci. Technol. 7, 79 (2017).
[4] F. Jahangiri, M. Hashida, S. Tokita, T. Nagashima, M. Hangyo, and S. Sakabe. Enhancing the energy of terahertz radiation from plasma produced by intense femtosecond laser pulses. Appl. Phys. Lett. 102, 191106 (2013).
[5] A.A. Frolov. Dipole Mechanism Generation of Terahertz Waves under Laser-Cluster Interaction. Plasma Phys. Rep. 44, 40 (2018).
