| 1. |
- Bergé, Luc, et al.
(författare)
-
THz emissions by two-color filaments in air: Revisiting the wavelength scaling
- 2019
-
Ingår i: Optics InfoBase Conference Papers. - 2162-2701. ; Part F134-NLO 2019
-
Konferensbidrag (refereegranskat)abstract
- We report impressive growths in the terahertz energies supplied by air plasmas created by two-color laser pulses whose fundamental wavelength is increased. Comprehensive 3D simulations reveal the crucial role of the two-color relative phase.
|
|
| 2. |
- Bergé, Luc, et al.
(författare)
-
Wavelength scaling of THz emissions by two-color filaments in air
- 2019
-
Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019. ; June 2019
-
Konferensbidrag (refereegranskat)abstract
- Producing terahertz (THz) radiation by ultrashort laser pulses has become an active field of research because of its promising applications in, e.g., spectroscopy and medical imaging [1]. Efficient THz emitters can be obtained by focusing into air a two-color femtosecond light pulse, composed of fundamental (FH) and second (SH) harmonics, in order to create a plasma channel that acts as a frequency converter [2]. Recent studies [3,4] showed that increasing the pump wavelength enhances the THz energy. However, there is no consensus on the gain factors expected when pushing the FH wavelength, λ0, from the near-IR to the mid-IR range. Clerici et al. [3] reported THz energy yields scaling like λ20 in the range 0.8-1.8 μm. By contrast, according to the local-current model [2,4], the largest THz energy attained by two colors with π/2 relative phase should follow a scaling in λ20 only.
|
|
| 3. |
- Kaltenecker, K. J., et al.
(författare)
-
Plasmonic Resonances Affecting Terahertz Generation in Laser-Induced Gas-Plasmas
- 2018
-
Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - : Book Series: International Conference on Infrared Millimeter and Terahertz Waves. - 2162-2027 .- 2162-2035. ; 2018-September
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate that plasmonic resonances can be used to broaden the terahertz emission spectrum from two-color laser-driven gas-plasmas. This effect can be controlled by changing the polarization properties of elliptically shaped driving laser-pulses.
|
|
| 4. |
- Nguyen, Alisée, et al.
(författare)
-
Broadband terahertz radiation from two-color mid- and far-infrared laser filaments in air
- 2018
-
Ingår i: Physical Review A. - 2469-9934 .- 2469-9926. ; 97:6
-
Tidskriftsartikel (refereegranskat)abstract
- We study terahertz (THz) emission by two-color femtosecond filaments in air using pump wavelengths λ0 from 0.8 to 10.6 μm. Comprehensive three-dimensional numerical simulations show that tens-of-centimeter long filaments created by a 10.6-μm pump pulse can produce mJ energy yields and GV/m field strengths, while the laser-to-THz conversion efficiency exceeds the percent level. Changing temperature and humidity conditions reveals a surprisingly high stability of the THz spectra against different weather conditions. We also examine the role of many-body Coulomb effects on ionization. This additional plasma source promotes longer filaments that act as efficient THz emitters, despite enhanced plasma defocusing.
|
|
| 5. |
- Nguyen, Alisée, et al.
(författare)
-
Wavelength scaling of terahertz pulse energies delivered by two-color air plasmas
- 2019
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 44:6, s. 1488-1491
-
Tidskriftsartikel (refereegranskat)abstract
- We address the long-standing problem of anomalous growth observed in the terahertz (THz) energy yield from air plasmas created by two-color laser pulses, as the fundamental wavelength λ 0 is increased. Using two distinct optical parametric amplifiers (OPAs), we report THz energies scaling like λ α0 with large exponents 5.6 ≤ α ≤ 14.3, which departs from the growth in λ 20 expected from photocurrent theory. By means of comprehensive 3D simulations, we demonstrate that the changes in the laser beam size, pulse duration, and phase-matching conditions in the second-harmonic generation process when tuning the OPA’s carrier wavelength can lead to these high scaling powers. The value of the phase angle between the two colors reached at the exit of the doubling crystal turns out to be crucial and even explains non-monotonic behaviors in the measurements.
|
|
| 6. |
|
|
| 7. |
- Thiele, Illia, 1989, et al.
(författare)
-
Terahertz emission from laser-driven gas plasmas: A plasmonic point of view
- 2018
-
Ingår i: Optica. - 2334-2536. ; 5:12, s. 1617-1622
-
Tidskriftsartikel (refereegranskat)abstract
- We disclose an unanticipated link between plasmonics and nonlinear frequency down-conversion in laser-induced gas-plasmas. For two-color femtosecond pump pulses, a plasmonic resonance is shown to broaden the terahertz emission spectra significantly. We identify the resonance as a leaky mode, which contributes to the emission spectra whenever electrons are excited along a direction where the plasma size is smaller than the plasma wavelength. As a direct consequence, such resonances can be controlled by changing the polarization properties of elliptically shaped driving laser pulses. Both experimental results and 3D Maxwell consistent simulations confirm that a significant terahertz pulse shortening and spectral broadening can be achieved by exploiting the transverse driving laser beam shape as an additional degree of freedom.
|
|
