1,170 research outputs found
Electrons catch a terahertz wave: Far-infrared fi elds control ultrashort electron pulses
No full textPlasmon-enhanced extreme-ultraviolet light generation: Challenges and future perspectives
No full textWe present a study of plasmon-enhanced gas excitation and extreme-ultraviolet (EUV) light generation in bow-tie antennas and tapered hollow waveguides. The observed EUV emission corresponds to incoherent atomic and ionic fluorescence without any sign from coherent highharmonic generation
Generation and Bistability of a Waveguide Nanoplasma Observed by Enhanced Extreme-Ultraviolet Fluorescence
No full textWe present a study of the highly nonlinear optical excitation of noble gases in tapered hollow waveguides using few-femtosecond laser pulses. The local plasmonic field enhancement induces the generation of a nanometric plasma, resulting in incoherent extreme-ultraviolet fluorescence from optical transitions of neutral and ionized xenon, argon, and neon. Despite sufficient intensity in the waveguide, high-order harmonic generation is not observed. The fluorescent emission exhibits a strong bistability manifest as an intensity hysteresis, giving strong indications for multistep collisional excitations.Deutsche Forschungsgemeinschaft [DFG-ZUK 45/1, SFB 755
Femtosecond trimer quench in the unconventional charge-density-wave material 1 T ′ − TaTe 2
Full text linkUltrafast optical switching of materials properties promises future technological applications, enabled by fundamental insights about microscopic couplings and nonequilibrium phenomena. Transition-metal dichalcogenides (TMDCs) combine photosensitivity with strong correlations, furthering rich phase diagrams and enhanced tunability. The compound 1 T ′ − TaTe 2 exhibits an electronically and structurally unique set of charge density waves (CDWs), featuring an unusual increase in conductivity and amplitude modes of low prominence. Compared to other charge-ordered TMDCs, only very few studies addressed the ultrafast response of this material to optical excitation. In particular, the question whether such unconventional properties translate to unusual quench dynamics remains largely unresolved. Here, we investigate the structural dynamics in 1 T ′ − TaTe 2 by means of ultrafast nanobeam electron diffraction at an unprecedented repetition rate of 2 MHz . We reveal a strongly directional cooperative atomic motion during the one-dimensional quench of the low-temperature trimer lattice. These dynamics are completed within less than 500 fs , substantially faster than reported previously. In striking contrast, the periodic lattice distortion of the room-temperature phase is unusually robust against high-density electronic excitation. In conjunction with the known sensitivity of 1 T ′ − TaTe 2 to chemical doping, we thus expect the material to serve as a versatile platform for tunable structural control by optical stimuli. Published by the American Physical Society 2024Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/50110000165
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