Development of a refractive plasma lens for focusing attosecond beams
Final Report Abstract
Attosecond science provides unique opportunities for the investigation of electron dynamics on extremely short timescales. For being able to perform pump-probe experiments, it is essential to focus attosecond pulses, which is a challenging task. Transmittive optics based on conventional materials cannot be used, because the pulses would experience a large chirp when propagating through these materials. Moreover, attosecond pulses are typically generated in the extreme-ultraviolet (XUV) or X-ray range of the electromagnetic spectrum, where conventional matter is highly absorbing. Reflective mirrors, which are typically used as an alternative to focus attosecond pulses, however, suffer from large reflection losses in these spectral regions. To overcome the afore-mentioned limitations, we have proposed and demonstrated the use of a plasma lens for focusing attosecond pulses. The plasma lens overcomes the limitations of conventional lenses: (i) By fully ionizing a hydrogen plasma, absorption of XUV light can be minimized. (ii) By exploiting refraction due to free electrons in the plasma, different focusing effects for different wavelengths of the broadband attosecond pulses (known as chromatic aberrations) can be substantially reduced. Moreover, this results in minimal stretching of attosecond pulses by the plasma lens. This project was performed in close collaboration with Prof. Jens Osterhoff and his successor Dr. Jonathan Christopher Wood at DESY, Hamburg, who developed a capillary discharge source that was used to generate a plasma with the required properties. The attosecond plasma lens experiments were performed at the Max-Born-Institut in Berlin. Focusing of attosecond pulses with photon energies centered at 20 eV and 80 eV was demonstrated. Furthermore, it was shown that the near-infrared (NIR) driving pulses, which were used to generate the attosecond pulses, were effectively defocused by the plasma lens. As a result, ultrathin metal filters, which are usually used to block the NIR pulses, may become unnecessary in the future. Consequently, the on-target power of attosecond pulses may be substantially enhanced, providing improved opportunities for the investigation of ultrafast electron dynamics.
Publications
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“Attosecond plasma lens”, peer-reviewed conference contribution at ATTO X in Lund, Sweden (2025)
E. Svirplys, H. Jones, G. Loisch, J. Thomas, M. Huck, O. Kornilov, J. M. Garland, J. C. Wood, M. J. J. Vrakking, J. Osterhoff & B. Schütte
