Terahertz pulse generation by two-color laser fields with circular polarization
arXiv:2007.08191 · doi:10.1088/1367-2630/abb863
Abstract
We study the influence of the polarization states of femtosecond two-color pulses ionizing gases on the emitted terahertz radiation. A local-current model and plane-wave evaluations justify the previously-reported impact on the THz energy yield and an (almost) linearly-polarized THz field when using circularly-polarized laser harmonics. For such pump pulses, the THz yield is independent on the relative phase between the two colors. When the pump pulses have same helicity, the increase in the THz yield is associated to longer ionization sequences and higher electron transverse momenta acquired in the driving field. Reversely, for two color pulses with opposite helicity, the dramatic loss of THz power comes from destructive interferences driven by the highly symmetric response of the photocurrents lined up on the third harmonic of the fundamental pulse. While our experiments confirm an increased THz yield for circularly polarized pumps of same helicity, surprisingly, the emitted THz radiation is not linearly-polarized. This effect is explained by means of comprehensive 3D numerical simulations highlighting the role of the spatial alignment and non-collinear propagation of the two colors.
arXiv comment27 pages, 13 figures
References in corpus (11)
- Ultrashort filaments of light in weakly-ionized, optically-transparent media
- Tailoring THz radiation by controlling tunnel photoionization events in gases
- Boosting terahertz generation in laser-field ionized gases using a sawtooth wave shape
- Observation of Terahertz Radiation via the Two-Color Laser Scheme with Uncommon Frequency Ratios
- Short pulse generation and mode control of broadband terahertz quantum cascade lasers
- Spectral dynamics of THz pulses generated by two-color laser filaments in air: The role of Kerr nonlinearities and pump wavelength
- Sequential terahertz pulse generation by photoionization and coherent transition radiation in underdense relativistic plasmas
- Theory of terahertz emission from femtosecond-laser-induced micro-plasmas
- Sensitivity of propagation and energy deposition in femtosecond filamentation to the nonlinear refractive index
- Broadband terahertz emission from two-color fs-laser-induced microplasmas
- Boosting terahertz-radiation power with two-color circularly polarized midinfrared laser pulses