Single-shot characterization of independent femtosecond extreme ultraviolet free electron and infrared laser pulses

Abstract

Two-color above threshold ionization of helium and xenon has been used to analyze the synchronization between individual pulses of the femtosecond extreme ultraviolet ͑XUV͒ free electron laser in Hamburg and an independent intense 120 fs mode-locked Ti:sapphire laser. Characteristic sidebands appear in the photoelectron spectra when the two pulses overlap spatially and temporally. The cross-correlation curve points to a 250 fs rms jitter between the two sources at the experiment. A more precise determination of the temporal fluctuation between the XUV and infrared pulses is obtained through the analysis of the single-shot sideband intensities.

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

“…In this second and current generation of the set up we perform HHG in a cell, focus the VUV radiation into the interaction region and use a magnetic bottle type time of flight electron spectrometer for PES. Side bands in the photoelectron spectra are used to determine the time resolution of the set up (68)(69)(70)(71)(72)(73)(74)(75)(76)(77)(78)(79).…”

A femtosecond X-ray/optical cross-correlator

“…So far, approaches like laser induced side band generation and streaking in vacuum ultraviolet photoemission from noble gases have been put forward to measure temporal overlap 32,27 . This can only be done using dedicated electron spectrometers under high vacuum conditions 27 and is limited by space charge effects.…”

“…1, the induced change of optical reflectivity was probed at an angle of incidence of 53° by delayed optical pulses at 800 nm or optionally 400 nm with a duration of 120 -150 fs (fwhm) delivered from an optical parametric amplifier system with 1 MHz repetition rate, electronically synchronized to the electron accelerator 32 . The optical pulse energies were detected in a reference path and after reflection with two fast photodiodes, allowing for transient reflectivity measurements pulse by pulse using a 2 GHz analog to digital converter (Acqiris) embedded into the distributed object oriented control system (DOOCS) 33 of FLASH.…”

Characterization of the FLASH XUV-FEL pulses by two-color photoionization experiments

“…Details of the two-color pump-probe set-up are given elsewhere [12,13]. Briefly, the XUV Free Electron Laser (FEL) and the optical laser beams were introduced into the vacuum chamber in a collinear geometry and intersected an effusive gas jet within the acceptance angle of a magnetic bottle electron spectrometer (MBES) (Fig.…”

“…Intensity and shape of these sidebands depend strongly on the temporal and spatial profiles of the two femtosecond pulses [7] and can therefore be utilized to characterize the XUV pulses [9,10]. Since the underlying physical processes are theoretically well understood [11], the method can even be applied and extended to the analysis of single-shot spectra allowing for each individual event to determine the time delay between both the XUV and the optical laser pulses [12].…”