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Start date: 2010 × DDC: 620 × Subject: Laser pulses × WGL Institute: MBI ×

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Now showing 1 - 3 of 3
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    Optimization of the energy deposition in glasses with temporally-shaped femtosecond laser pulses
    (Amsterdam [u.a.] : Elsevier, 2011) Mauclair, C.; Mishchik, K.; Mermillod-Blondin, A.; Rosenfeld, A.; Hertel, I.V.; Audouard, E.; Stoian, R.
    Bulk machining of glasses with femtosecond laser pulses enables the fabrication of embedded optical functions. Due to the nonlinear character of the laser-matter interaction, structural modifications can occur within the focal region. To reach a full control of the process, ways of controlling the deposition of the laser energy inside the material have to be unveiled. From static and time-resolved pictures of bulk-excitation of a-SiO2 and borosilicate glass, we show that particular laser temporal shapes such as picosecond sequences can better confine the energy deposition than the femtosecond sequence by reducing the propagation artifacts.
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    Valley control by linearly polarized laser pulses: example of WSe2
    (Washington, DC : OSA, 2022) Sharma, S.; Elliott, P.; Shallcross, S.
    Electrons at the band edges of materials are endowed with a valley index, a quantum number locating the band edge within the Brillouin zone. An important question is then how this index may be controlled by laser pulses, with current understanding that it couples exclusively via circularly polarized light. Employing both tight-binding and state-of-the-art time dependent density function theory, we show that on femtosecond time scales valley coupling is a much more general effect. We find that two time separated linearly polarized pulses allow almost complete control over valley excitation, with the pulse time difference and polarization vectors emerging as key parameters for valley control. Our findings highlight the possibility of controlling coherent electronic excitation by successive femtosecond laser pulses, and offer a route towards valleytronics in two-dimensional materials.
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    Compact intense extreme-ultraviolet source
    (Washington, DC : OSA, 2021) Major, Balázs; Ghafur, Omair; Kovács, Katalin; Varjú, Katalin; Tosa, Valer; Vrakking, Marc J. J.; Schütte, B.
    High-intensity laser pulses covering the ultraviolet to terahertz spectral regions are nowadays routinely generated in a large number of laboratories. In contrast, intense extreme-ultraviolet (XUV) pulses have only been demonstrated using a small number of sources including free-electron laser facilities [1-3] and long high-harmonic generation (HHG) beamlines [4-9]. Here we demonstrate a concept for a compact intense XUV source based on HHG that is focused to an intensity of $2 \times 10^{14}$ W/cm$^2$, with a potential increase up to $10^{17}$ W/cm$^2$ in the future. Our approach uses tight focusing of the near-infrared (NIR) driving laser and minimizes the XUV virtual source size by generating harmonics several Rayleigh lengths away from the NIR focus. Accordingly, the XUV pulses can be refocused to a small beam waist radius of 600 nm, enabling the absorption of up to four XUV photons by a single Ar atom in a setup that fits on a modest (2 m) laser table. Our concept represents a straightforward approach for the generation of intense XUV pulses in many laboratories, providing novel opportunities for XUV strong-field and nonlinear optics experiments, for XUV-pump XUV-probe spectroscopy and for the coherent diffractive imaging of nanoscale structures.