Phase-locking of time-delayed attosecond XUV pulse pairs

Abstract

We present a setup for the generation of phase-locked attosecond extreme ultraviolet (XUV) pulse pairs. The attosecond pulse pairs are generated by high harmonic generation (HHG) driven by two phase-locked near-infrared (NIR) pulses that are produced using an actively stabilized Mach-Zehnder interferometer compatible with near-single cycle pulses. The attosecond XUV pulses can be delayed over a range of 400 fs with a sub-10-as delay jitter. We validate the precision and the accuracy of the setup by XUV optical interferometry and by retrieving the energies of Rydberg states of helium in an XUV pump–NIR probe photoelectron spectroscopy experiment.

Improved stabilization scheme for extreme ultraviolet quantum interference experiments

“…However, this approach does not stabilize phase fluctuations introduced in the harmonic generation process itself or the phase jitter introduced in the XUV beampath. The same applies to other demonstrated concepts stabilizing the pulse sequences on the fundamental wavelength [17,8,34]. In the tabletop-approach based on HHG in gases, this problem is usually not significant, since the phase jitter introduced between the pump and probe pulses can be kept small [18].…”

Attosecond Optical and Ramsey-Type Interferometry by Postgeneration Splitting of Harmonic Pulse

“…They focused these two replicas of the fundamental laser pulse into a xenon gas target to generate an XUV HH pulse pair, which was applied to time-domain Ramsey-type interferometry to achieve high-resolution spectroscopy. Recently, this time-domain Ramsey-type interferometry was applied to the Rydberg states of He atoms by Koll and coworkers [14]. Two replicas of phase-locked fundamental laser pulse can also be generated using an optical parametric amplifier (OPCPA) system seeded by a frequency-comb laser whose frequency is locked to an atomic clock.…”

“…However, if we divide an NIR pulse into two before highorder harmonics generation (HHG), the temporal separation between the resulting two XUV pulses cannot be sufficiently small, because the interference of the two NIR pulses causes a complex modulation of the XUV intensity. For example, the interference signal in [14] exhibits such modulations in the delay time range shorter than ~50 fs due to the interference of the NIR pulses and their pedestals. In addition, at the higher NIR intensity, the variations of the density and the density distribution in the nonlinear medium perturbed by the first NIR pulse for HHG cannot be revived before the arrival of the second NIR pulse for HHG.…”

“…Ultrafast Science focused XUV HH pulse pair spatially interfere and excite the target atoms by irradiating them with a tightly focused 3rd harmonic (TH) UV pulse. Thanks to the high-photon energy of the UV pulse, we can probe the population in the 1s2p ( 1 P) excited state by the photoionization, which cannot be induced by the NIR probe pulse adopted previously in other schemes [11,12,14]. By taking advantage of the postgeneration splitting of the HH pulse, we were able to observe that the fringes in the electron yield originating from the optical interference of the HH pulse pair with a period of ~200 as around Δt ctrl ≃ 0 seamlessly continued to the time-domain Ramsey-type fringes originating from the quantum interference around Δt ctrl ≥ 10 fs.…”

Modification of laser-induced state in atomic attosecond transient absorption by the XUV pulse pair

“…This timedependent modification interferes with the natural oscillations of atomic states, resulting in a richly characterized absorption spectrum. With the development (or the knowledge) of the attosecond laser technology, a pair of XUV attosecond pulses have been either generated in experiment [36] or proposed to be produced via spatiotemporal wavefront rotation induced by plasma in theory [37], which provides another degree of freedom to modify the process of electron motion. Such novel attosecond light source has been employed in the experiment.…”