Spatiotemporal characterization of single-order high harmonic pulses from time-compensated toroidal-grating monochromator

Abstract

Extreme ultraviolet (XUV) single-order high harmonic pulses with 10 6 photons/pulse were separated from multiple harmonic orders by a time-compensated toroidal-grating monochromator consisting of a pair of toroidal gratings. The first grating separates the harmonic order and the second one compensates for the pulse-front tilt. The center photon energies were tunable between 42 and 23 eV. The separated single harmonic pulses were spatially and temporally characterized as having a spot size of 58 ± 3 µm at the focus, with a shortest pulse duration of 47 ± 2 fs. The developed XUV light source is versatile for application to time-and space-resolved spectroscopy.

Femtosecond time-resolved photoelectron spectroscopy with a vacuum-ultraviolet photon source based on laser high-order harmonic generation

“…This comparably short pulse duration for monochromatized HHG VUV pulses makes our set up unique in a sense that, to the best of our knowledge, this is the shortest pulse duration measured so far with a monochromator based on a single grating. Shorter femtosecond pulses have been produced with pairs of multilayer optics (57,63,66) and pairs of gratings mounted in conical diffraction (55,56). Compared to other set ups based on conventional diffraction gratings (60) we produce shorter pulses because the grazing angle on the grating is comparably large and the distance of the HHG source to the grating is very short.…”

“…For ultrafast applications, time-resolved photoelectron spectroscopy (PES) (41) with pump-probe schemes where the sample is pumped with a laser pulse and probed with HHG pulses at a defined pump-probe delay has emerged as a powerful tool for the investigation of ultrafast dynamics in gas phase samples (42)(43)(44)(45)(46)(47) and on surfaces (48)(49)(50)(51)(52)(53)(54). A variety of set ups has been described to perform such experiments on gas phase samples (55)(56)(57)(58)(59)(60), on surfaces (61-64) or on both (65,66).…”

Pulse Compression of Phase-matched High Harmonic Pulses from a Time-Delay Compensated Monochromator

“…To select a single harmonic with the pulse duration preserved, a time-delay compensated monochromator (TDCM), consisting of a pair of gratings to compensate for the pulse-front tilt shown in Fig. 1, was proposed and has been experimentally and theoretically investigated [1][2][3][4] In TDCM, the first grating and the slit separate the harmonic orders and then the second grating corrects the pulse-front tilt introduced by the first grating.…”

“…Although we constructed a TDCM in the previous work and the pulse duration was compressed to 47 fs, there still remains a question that what limits the compressed pulse duration [4]. Especially, we are interested in the accuracy required for constructing the monochromator.…”

Design Study of Time-Preserving Grating Monochromators for Ultrashort Pulses in the Extreme-Ultraviolet and Soft X-Rays

“…The first grating is demanded to perform the spectral selection on an intermediate slit, and the second grating compensates for the pulse-front tilt of the monochromatic diffracted beam, giving an output pulse with ideally no tilt. Double-grating monochromators have demonstrated a temporal resolution higher than 10 fs [25][26][27][28]. The choice between the two configurations has to be performed as a trade-off between efficiency and simplicity, that are maximized in the single-grating design, and temporal resolution, that is maximized in the double-grating design.…”