When an intense laser pulse ionizes the surface of a strong target, it produces plasma so thick that it is impenetrable to the laser, even if the target was initially transparent. This concentrates the laser energy even more in time and makes plasma mirrors a promising course for the generation of ever more extreme and shorter laser pulses.
This is accomplished notably through a preceding laser pulse which starts the plasma creation and growth. Varying the time delay after which the subsequent main driving pulse is fired lets the scientists control the nanometer-range density gradient on the plasma mirror surface.
Scientists at the LOA (Laboratoire dOptique Appliquée) in France have actually accomplished an advancement by successfully driving a plasma mirror at a rate of 1,000 shots per second in the relativistic program. This involves utilizing a laser field with such intensity that it triggers the plasma electrons to oscillate at nearly the speed of light.
For the first time, scientists succeeded at driving at a thousand shots per second a so-called plasma mirror in the relativistic regime, i.e. with a laser field so strong that tosses the plasma electrons backward and forward at nearly the speed of light. The feat was accomplished at the LOA (Laboratoire dOptique Appliquée) in France.
When an extreme laser pulse ionizes the surface of a strong target, it produces plasma so dense that it is impenetrable to the laser, even if the target was at first transparent. The laser now gets shown off this “plasma mirror.” In the relativistic routine, the mirror surface area no longer just is but sits stills driven to oscillate so quick that, through a procedure called relativistic surface high-harmonic generation (SHHG), it temporally compresses the lasers electro-magnetic field cycles. This concentrates the laser energy further in time and makes plasma mirrors a promising course for the generation of ever more extreme and shorter laser pulses.
Schematics of the speculative setup for SHHG and electron velocity on a kHz plasma mirror. Credit: Ultrafast Science
Their usage and great control does, nevertheless, place very high demands on the driving laser such as pristine spatiotemporal pulse quality and temporal contrast, as well as a big peak power of terawatts, i.e. thousands of gigawatts. This had actually only been achieved in single-shot experiments made with much larger lasers that run at ≤ 10 Hz repeating rate.
This is accomplished especially through a preceding laser pulse which starts the plasma creation and growth. Varying the time delay after which the subsequent main driving pulse is fired lets the scientists control the nanometer-range density gradient on the plasma mirror surface.
In a next action, the scientists plan to deal with refocusing the radiation reflected off the plasma mirror and target reaching record-high light strengths for light pulses shorter than a femtosecond.
Recommendation: “High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate” by Stefan Haessler, Marie Ouillé, Jaismeen Kaur, Maïmouna Bocoum, Frederik Böhle, Dan Levy, Louis Daniault, Aline Vernier, Jérôme Faure and Rodrigo Lopez-Martens, 28 June 2022, Ultrafast Science.DOI: 10.34133/ 2022/9893418.
This work was supported by the Agence Nationale put la Recherche (ANR-11-EQPX-005-ATTOLAB and ANR-14- CE32-0011-03 APERO), Investissements dAvenir Program LabEx PALM (ANR-10-LABX-0039-PALM), European Research Council (ERC FEMTOELEC 306708 and ERC ExCoMet 694596), Laserlab-Europe (H2020-EU.1.4.1.2. grant contract ID 654148), and Région Ile-de-France (SESAME 2012-ATTOLITE).
