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We model laser filamentation in ZnSe in the mid-infrared (Mid-IR, wavelengths λ = 4 and 6 μm) and the long-wavelength infrared (LWIR, λ = 8 and 10 μm) using carrier-resolved unidirectional pulse propagation equations (UPPE). We predict an unprecedented propagation regime at λ = 8 μm that supports light bullets, which are spatio-temporally non-spreading electromagnetic pulses. Furthermore, in contrast to the previous report in air in the mid-IR, we predict that LWIR light bullets in solids critically rely on plasma-mediated dispersion, which dynamically evolves during multiphoton and tunneling ionization as peak plasma densities reach ρ 6.6 ×10^18 cm-3 . Finally, the plasma-assisted light bullets propagate with sub-cycle pulse durations and peak intensities I = 1.1 ×10^12 W /cm^2 , making them useful for high-harmonic generation and attosecond pulse generation.
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Atmospheric effects on the laser-driven avalanche-based remote detection of radiation
The effect of realistic atmospheric conditions on mid-IR (λ = 3.9 µm) and long-wave-IR (λ = 10 µm) laser-induced avalanche breakdown for the remote detection of radioactive material is examined experimentally and with propagation simulations. Our short-range in-lab mid-IR laser experiments show a correlation between increasing turbulence level and a reduced number of breakdown sites associated with a reduction in the portion of the focal volume above the breakdown threshold. Simulations of propagation through turbulence are in excellent agreement with these measurements and provide code validation. We then simulate propagation through realistic atmospheric turbulence over a long range (0.1–1 km) in the long-wave-IR regime (λ = 10 µm). The avalanche threshold focal volume is found to be robust even in the presence of strong turbulence, only dropping by ∼50% over a propagation length of ∼0.6 km. We also experimentally assess the impact of aerosols on avalanche-based detection, finding that, while background counts increase, a useful signal is extractable even at aerosol concentrations 105times greater than what is typically observed in atmospheric conditions. Our results show promise for the long-range detection of radioactive sources under realistic atmospheric conditions.
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- Award ID(s):
- 2010511
- PAR ID:
- 10410494
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 48
- Issue:
- 9
- ISSN:
- 0146-9592; OPLEDP
- Format(s):
- Medium: X Size: Article No. 2480
- Size(s):
- Article No. 2480
- Sponsoring Org:
- National Science Foundation
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