| 1. |
- Aktas, A., et al.
(författare)
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Diffractive photoproduction of rho mesons with large momentum transfer at HERA
- 2006
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 638:5-6, s. 422-431
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Tidskriftsartikel (refereegranskat)abstract
- The diffractive photoproduction of rho mesons, ep -> e rho Y, with large momentum transfer squared at the proton vertex, vertical bar t vertical bar, is studied with the H1 detector at HERA using an integrated luminosity of 20.1 pb(-1). The photon-proton centre of mass energy spans the range 75 < W < 95 GeV, the photon virtuality is restricted to Q(2) < 0.01 GeV2 and the mass My of the proton remnant is below 5 GeV. The t dependence of the cross section is measured for the range 1.5 < vertical bar t vertical bar < 10.0 GeV2 and is well described by a power law, d sigma/d vertical bar t vertical bar proportional to vertical bar t vertical bar(-n). The spin density matrix elements, which provide information on the helicity structure of the interaction, are extracted using measurements of angular distributions of the rho decay products. The data indicate a violation of s-channel helicity conservation, with contributions from both single and double helicity-flip being observed. The results are compared to the predictions of perturbative QCD models.
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| 2. |
- Jones, D. L., et al.
(författare)
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High dynamic range VLBI observations of NGC 6251
- 1986
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Ingår i: Astrophysical Journal. - Philadelphia, United States : Institute of Physics Publishing, Inc. - 0004-637X .- 1538-4357. ; 305:2, s. 684-697
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Riepl, J., et al.
(författare)
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Field-resolved high-order nonlinearities in a free-running terahertz quantum cascade laser
- 2022
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Ingår i: CLEO : Science and Innovations, S and I 2022 - Science and Innovations, S and I 2022. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- Two-dimensional terahertz strong-field spectroscopy reveals wave-mixing processes up to eighth order in a free-running quantum cascade laser, unravelling its sub-cycle gain dynamics and nonlinearities in a regime of negative absorption.
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| 4. |
- Riepl, J, et al.
(författare)
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Field-resolved high-order sub- cycle nonlinearities in a terahertz semiconductor laser
- 2021
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Ingår i: Light, science & applications. - : Springer Science and Business Media LLC. - 2047-7538. ; 10:1, s. 246-246
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Tidskriftsartikel (refereegranskat)abstract
- The exploitation of ultrafast electron dynamics in quantum cascade lasers (QCLs) holds enormous potential forintense, compact mode-locked terahertz (THz) sources, squeezed THz light, frequency mixers, and comb-basedmetrology systems. Yet the important sub-cycle dynamics have been notoriously difficult to access in operationalTHz QCLs. Here, we employ high-field THz pulses to perform the first ultrafast two-dimensional spectroscopy of afree-running THz QCL. Strong incoherent and coherent nonlinearities up to eight-wave mixing are detected belowand above the laser threshold. These data not only reveal extremely short gain recovery times of 2 ps at the laserthreshold, they also reflect the nonlinear polarization dynamics of the QCL laser transition for the first time, where wequantify the corresponding dephasing times between 0.9 and 1.5 ps with increasing bias currents. A density-matrixapproach reproducing the emergence of all nonlinearities and their ultrafast evolution, simultaneously, allows us tomap the coherently induced trajectory of the Bloch vector. The observed high-order multi-wave mixing nonlinearitiesbenefit from resonant enhancement in the absence of absorption losses and bear potential for a number of futureapplications, ranging from efficient intracavity frequency conversion, mode proliferation to passive mode locking.
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| 5. |
- Riepl, J., et al.
(författare)
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Sub-cycle high-order nonlinearities in a free-running terahertz semiconductor laser
- 2022
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Ingår i: The International Conference on Ultrafast Phenomena (UP) 2022. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- Field-resolved two-dimensional spectroscopy reveals the sub-cycle gain dynamics of a free-running terahertz quantum cascade laser and disentangles resonantly enhanced nonlinearities up to eight-wave mixing in a regime where gain replaces absorption.
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| 6. |
- Riepl, J., et al.
(författare)
-
Sub-cycle high-order nonlinearities in a terahertz quantum cascade laser
- 2022
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Ingår i: IRMMW-THz 2022 - 47th International Conference on Infrared, Millimeter and Terahertz Waves. - 2162-2027 .- 2162-2035. - 9781728194271 ; 2022-August
-
Konferensbidrag (refereegranskat)abstract
- Ultrafast electron dynamics in quantum cascade lasers hold enormous potential for the implementation of intense, compact mode-locked terahertz sources, squeezed terahertz light, frequency mixers, and comb-based metrology systems. Yet the important sub-cycle dynamics have been notoriously difficult to access in operational terahertz quantum cascade lasers. Here we show the first field-resolved two-dimensional terahertz spectroscopy of a free-running quantum cascade laser, revealing its sub-cycle gain dynamics and disentangling resonantly enhanced high-order nonlinearities up to eight-wave mixing in a regime of negative absorption.
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