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12THz-O-3
Control of terahertz emission from long two-color filaments
P. Chizhov1, A. Ushakov1, V. Bukin1, S. Garnov1
1Prokhorov General Physics Institute of the Russian Academy of Sciences, Oscillations department, Moscow, Russian Federation
Terahertz generation in gas plasma created by two-color femtosecond laser pulses is attracting a lot of attention due to ability of high-energy laser pumping and broad spectrum of generated radiation [1]. However, this scheme is sensitive to mutual phase shift between harmonics [2]. For long filaments this phase difference is changing along the plasma channel leading to an off-axis peak in spatial THz distribution [3] and to possibility of waveform control by initial phase mismatch adjustment between harmonics [4].
We investigate experimentally THz generation in two-color femtosecond filaments with lengths up to 100 mm. For such lengths a strong influence of phase walk-off between harmonics along the plasma channel on terahertz emission is observed. It is demonstrated the possibility of THz pulse waveform and power control by simultaneous use of adjustment of the initial phase shift between harmonics and screening of a part of the THz radiation with a metallic iris diaphragm. We also demonstrate the spectral filtering by use of n-retarder screens for a distinct THz frequency or by use of axicon PTFE-lenses.
References
[1] X.-C. Zhang, A. Shkurinov, Y. Zhang, Nature Photonics 11 (1), 16 (2017).
[2] M. Kress, T. Loffler, S. Eden, M. Thomson and H. Roskos, Opt. Lett. 29 (10), 1120 (2004).
[3] Y. S. You, T. I. Oh, and K. Y. Kim, Phys. Rev. Lett. 109 (18), 183902 (2012).
[4] Z. Zhang, Y. Chen, M. Chen, Z. Zhang, J. Yu, Z. Sheng and J. Zhang, Phys. Rev. Lett. 117 (24), 243901 (2016).
