| 1. |
- Houard, Aurélien, et al.
(författare)
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Laser-guided lightning
- 2023
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Ingår i: Nature Photonics. - : Springer Nature. - 1749-4885 .- 1749-4893. ; 17:3, s. 231-235
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Tidskriftsartikel (refereegranskat)abstract
- Lightning discharges between charged clouds and the Earth's surface are responsible for considerable damages and casualties. It is therefore important to develop better protection methods in addition to the traditional Franklin rod. Here we present the first demonstration that laser-induced filaments-formed in the sky by short and intense laser pulses-can guide lightning discharges over considerable distances. We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics. An experimental campaign was conducted on the Santis mountain in north-eastern Switzerland during the summer of 2021 with a high-repetition-rate terawatt laser. The guiding of an upward negative lightning leader over a distance of 50 m was recorded by two separate high-speed cameras. The guiding of negative lightning leaders by laser filaments was corroborated in three other instances by very-high-frequency interferometric measurements, and the number of X-ray bursts detected during guided lightning events greatly increased. Although this research field has been very active for more than 20 years, this is the first field-result that experimentally demonstrates lightning guided by lasers. This work paves the way for new atmospheric applications of ultrashort lasers and represents an important step forward in the development of a laser based lightning protection for airports, launchpads or large infrastructures. A terawatt laser filament is shown to be able to guide lightning over a distance of 50 m in field trials on the Santis mountain in the Swiss Alps.
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| 2. |
- Chen, Shihua, et al.
(författare)
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Compression of high-energy ultrashort laser pulses through an argon-filled tapered planar waveguide
- 2011
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 28:5, s. 1009-1012
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Tidskriftsartikel (refereegranskat)abstract
- We propose a hollow tapered planar waveguide for compression of high-energy ultrashort laser pulses. Direct measurements suggest that it seems to find a very good trade-off among the energy throughput, the beam focusability, and the pulse compressibility. With a Ti:sapphire laser pulse of 12.0 mJ and 40 fs, our experiment produces an output pulse of 9: 4 fs duration with energy 9: 1 mJ (transverse magnetic mode) or 10: 0 mJ (transverse electric mode) in argon, each exhibiting a nice spatial mode. To evaluate such a tapered waveguide, the linear wave propagation theory and the solution to its complex propagation constant are also presented. c 2011 Optical Society of America
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| 3. |
- Jarnac, Amelie, et al.
(författare)
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Compression of TW class laser pulses in a planar hollow waveguide for applications in strong-field physics
- 2014
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Ingår i: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 68:12
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate pulse post-compression of a TW class chirped pulse amplification laser employing a gas-filled planar hollow waveguide. A waveguide throughput of 80% is achieved for 50 mJ input pulse energy. Good focusability is found and after compression with chirped mirrors a pulse duration of sub-15 fs is measured in the beam center. Whereas a total energy efficiency of approximate to 70% should be achievable, our post-compressor currently delivers 20 mJ output pulse energy (approximate to 40% efficiency), mostly limited by apertures of chirped mirrors and vacuum windows. The viability of the planar hollow waveguide compression scheme for applications in strong-field physics is demonstrated by generating high-order harmonics in a pulsed Ar gas cell.
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| 4. |
- Liu, Yi, et al.
(författare)
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Laser without population inversion of nitrogen ions pumped by femtosecond pulses
- 2019
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Ingår i: CLEO : QELS_Fundamental Science, CLEO_QELS 2019 - QELS_Fundamental Science, CLEO_QELS 2019. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We attribute the mechanism of "lasing" action of nitrogen ions pumped by femtosecond IR pulses to a laser without inversion scheme. Numerical simulations reproduce well the temporal dynamics and pressure dependence of the emission.
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| 5. |
- Liu, Yi, et al.
(författare)
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Unexpected Sensitivity of Nitrogen Ions Superradiant Emission on Pump Laser Wavelength and Duration
- 2017
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Ingår i: Physical Review Letters. - 0031-9007. ; 119:20
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen molecules in ambient air exposed to an intense near-infrared femtosecond laser pulse give rise to cavity-free superradiant emission at 391.4 and 427.8 nm. An unexpected pulse duration-dependent cyclic variation of the superradiance intensity is observed when the central wavelength of the femtosecond pump laser pulse is finely tuned between 780 and 820 nm, and no signal occurs at the resonant wavelength of 782.8 nm (2ω782.8 nm=ω391.4 nm). On the basis of a semiclassical recollision model, we show that an interference of dipolar moments of excited ions created by electron recollisions explains this behavior.
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| 6. |
- Steinhauer, Stephan, et al.
(författare)
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Rydberg excitons in Cu2O microcrystals grown on a silicon platform
- 2020
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Ingår i: Communications Materials. - : Springer Nature. - 2662-4443. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- Cuprous oxide (Cu2O) is a semiconductor with large exciton binding energy and significant technological importance in applications such as photovoltaics and solar water splitting. It is also a superior material system for quantum optics that enabled the observation of intriguing phenomena, such as Rydberg excitons as solid-state analogue to highly-excited atomic states. Previous experiments related to excitonic properties focused on natural bulk crystals due to major difficulties in growing high-quality synthetic samples. Here, the growth of Cu2O microcrystals with excellent optical material quality and very low point defect levels is presented. A scalable thermal oxidation process is used that is ideally suited for integration on silicon, demonstrated by on-chip waveguide-coupled Cu2O microcrystals. Moreover, Rydberg excitons in site-controlled Cu2O microstructures are shown, relevant for applications in quantum photonics. This work paves the way for the wide-spread use of Cu2O in optoelectronics and for the development of novel device technologies. Cu2O is of great interest for its excitonic properties, yet challenges in its fabrication means that most experiments focus on naturally occurring samples. Here, scalable thermal oxidation is reported for the growth of Cu2O with low-defect content, allowing the observation of Rydberg excitons.
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| 7. |
- Versteegh, Marijn A. M., et al.
(författare)
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Giant Rydberg excitons in Cu2O probed by photoluminescence excitation spectroscopy
- 2021
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Ingår i: PHYSICAL REVIEW B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 104:24
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Tidskriftsartikel (refereegranskat)abstract
- Rydberg excitons are, with their ultrastrong mutual interactions, giant optical nonlinearities, and very high sensitivity to external fields, promising for applications in quantum sensing and nonlinear optics at the singlephoton level. To design quantum applications it is necessary to know how Rydberg excitons and other excited states relax to lower-lying exciton states. Here, we present photoluminescence excitation spectroscopy as a method to probe transition probabilities from various excitonic states in cuprous oxide. We show giant Rydberg excitons at T = 38 mK with principal quantum numbers up to n = 30, corresponding to a calculated diameter of 3 mu m.
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| 8. |
- Zhang, Xiang, et al.
(författare)
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Backward lasing of singly ionized nitrogen ions pumped by femtosecond laser pulses
- 2020
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Ingår i: Applied Physics B: Lasers and Optics. - : Springer Science and Business Media LLC. - 0946-2171. ; 126:3
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Tidskriftsartikel (refereegranskat)abstract
- We report on the observation of backward lasing at 391.4 nm of nitrogen ions pumped by linearly polarized intense femtosecond pulses at 800 nm. The strongly enhanced spectral intensity at 391.4 nm, as well as the amplification of an externally injected backward seeding pulse, confirm that the backward 391.4 nm signal is due to optical amplification in the nitrogen gas plasma. Compared to the forward emission at 391.4 nm, the optimal backward emission is achieved at a lower gas pressure around 10 mbar, which is due to asymmetry of the backward and forward directions rooted in the traveling excitation geometry. Comparison of the signals in pure nitrogen and air revealed a strong quenching effect of the oxygen molecules, preventing backward lasing action in ambient air.
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