| 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. |
- 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.
|
|
