Chromium/scandium multilayer mirrors for isolated attosecond pulses at 145  eV

Abstract

Recent advances in the development of attosecond soft x-ray sources toward photon wavelengths below 10 nm are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. We demonstrate that current attosecond experiments in the sub-200-eV range benefit from these improved optics. We present our achievements in utilizing ion-beam-deposited chromium/scandium (Cr/Sc) multilayer mirrors, optimized by tailored material dependent deposition and interface polishing, for the generation of single attosecond pulses from a high-harmonic cut-off spectrum at a central energy of 145 eV. Isolated attosecond pulses have been measured by soft x-ray-pump/NIR-probe electron streaking experiments and characterized using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG/CRAB). The results demonstrate that Cr/Sc multilayer mirrors can be used as efficient attosecond optics for reflecting 600-attosecond pulses at a photon energy of 145 eV, which is a prerequisite for present and future attosecond experiments in this energy range.

Propagation-enhanced generation of intense high-harmonic continua in the 100-eV spectral region

“…To understand the effects of propagation, we compare the results calculated for the 1.5 mm gas jet, the 5 cm cell, and 10 cm cell. Before calculating the intensity distribution, we spectrally filter the harmonic spectra in accordance with the theoretical transmission of the 300 nm Zr filter and the calculated reflectivity curve of the XUV mirror used in previous two-photon absorption experiments [7,42,43]. The multilayer XUV mirror provides a 11 eV (FWHM) band-pass filter at a photon energy of 115 eV, corresponding to the continuum spectral region.…”

Impact of B_4C co-sputtering on structure and optical performance of Cr/Sc multilayer X-ray mirrors

“…In general, crystallization is a serious issue since crystallites increase high spatial frequency interfacial roughness resulting in a poor reflectivity performance [14,15]. The impact is severe on optics requiring larger periodicities such as polarizers and broadband mirrors, essential to polarimetry and to shape attosecond pulses [16][17][18].…”

VUV and XUV reflectance of optically coated mirrors for selection of high harmonics

“…By employing transmissive beam filters, such as gas, glass, and metal filters, further suppression of the undesired harmonics and selection of appropriate harmonic may be realized [10,20], in addition to blocking out the co-propagating driving field used to generate the harmonics [21]. Hence through the use of multilayer coated mirrors in parallel with other beam filtration methods, such as transmissive solid and gas filters, significant harmonic isolation can be achieved.…”