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HF-3
HF-3 is dedicated to the generation of coherent, high-order harmonics from overdense relativistic plasmas driven by ultra-intense femtosecond laser pulses. By driving the process with 20-TW pulses from ATLAS, we recently demonstrated phase coherence of a series of high-order harmonics emerging from the plasma and resultant attosecond bunching of the emitted radiation. Driving the process with the few-cycle pulses from LWS-20 affords promise for intense isolated attosecond pulses for XUV-pump/XUV-probe spectroscopy. This is the main goal we pursue with this beamline. The beamline can be fed both with ATLAS-100 and with and LWS-20. A number of diagnostics, including time-of-flight electron and ion spectrometers, a grazing-incidence XUV spectrograph and various XUV detectors are routinely used in the investigations. Both solid and liquid materials are being used as targets. The optimization of the XUV generation relies on measuring the spectrum, efficiency, divergence, coherence and temporal structure under various conditions. The temporal characterization is pursued by second-order nonlinear autocorrelation. These measurements also constitute the first prototypical XUV-pump/XUV-probe type studies.
contact: G. Tsakirislink to the personal page of George Tsakiris, Y. Mikhailovalink to the personal page of Julia Mikhailova
Fig. 1. Plasma emits attosecond pulses: when a solid surface interacts with an intense laser pulse plasma, is formed that acts as a mirror reflecting the laser light. During this interaction the vacuum-plasma interface modifies the incident spectrum, generating a reflected pulse rich in harmonics. This can result in attosecond pulses as has been shown in 3D-PIC simulations(for details see: Geissler M., et al. New J. Phys. 9, 218(2007)). The propagation of the EM-fields outside the simulation box clearly shows that the laser pulse (fundamental frequency – red color) when filtered in a frequency range between the 5th and 10th harmonic gives rise to a train of attosecond pulses (blue color). (© sryk)
Fig. 1. Plasma emits attosecond pulses: when a solid surface interacts with an intense laser pulse plasma, is formed that acts as a mirror reflecting the laser light. During this interaction the vacuum-plasma interface modifies the incident spectrum, generating a reflected pulse rich in harmonics. This can result in attosecond pulses as has been shown in 3D-PIC simulations(for details see: Geissler M., et al. New J. Phys. 9, 218(2007)). The propagation of the EM-fields outside the simulation box clearly shows that the laser pulse (fundamental frequency – red color) when filtered in a frequency range between the 5th and 10th harmonic gives rise to a train of attosecond pulses (blue color). (© sryk)
Fig. 2. The temporal characterization of the harmonic emission from solid targets was accomplished using the Volume Autocorrelation (VAC) technique (a). The coarse VAC yielded the overall duration of the XUV pulse (b). A fine scan in contrast reveals the sub-femtosecond temporal structure within a laser cycle.
Fig. 2. The temporal characterization of the harmonic emission from solid targets was accomplished using the Volume Autocorrelation (VAC) technique (a). The coarse VAC yielded the overall duration of the XUV pulse (b). A fine scan in contrast reveals the sub-femtosecond temporal structure within a laser cycle.
Fig. 3. Schematic of the HF-3 beamline. (© rhoe)
Fig. 3. Schematic of the HF-3 beamline. (© rhoe)