Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTemporal characterization of long quantum-path high harmonics
306
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We measure for the first time the duration of long-quantum path EUV high harmonics produced in xenon gas. The long-quantum path contribution to the high-harmonic signal was carefully controlled by employing a two-colour driving laser field and a high-harmonic spatial selection in the far field, over a range of $18-25,eV$ in photon energy. To characterise the temporal profile of long quantum path high harmonics, we performed a second order volume autocorrelation ($2-IVAC$) via two EUV photon double ionization in argon. Our results show the production and characterisation of a train of EUV pulses from the long-path with pulse duration as short as $1.4,fs$. This measurement demonstrates that the long-quantum path emission can have enough flux for performing non-linear EUV experiments, and that the long trajectories enable a pulse duration short enough to support measurements with a temporal resolution below $2,fs$.
rate research
Read More
Relativistic surface high harmonics have been considered a unique source for the generation of intense isolated attosecond pulses in the extreme ultra-violet (XUV) and X-ray spectral range. However, its experimental realization is still a challenging task requiring identification of the optimum conditions for the generation of isolated attosecond pulses as well as their temporal characterization. Here, we demonstrate measurements in both directions. Particularly, we have made a first step towards the temporal characterization of the emitted XUV radiation by adapting the attosecond streak camera concept to identify the time domain characteristics of relativistic surface high harmonics. The results, supported by PIC simulations, set the upper limit for the averaged (over many shots) XUV duration to <6 fs, even when driven by not CEP controlled relativistic few-cycle optical pulses. Moreover, by measuring the dependence of the spectrum of the relativistic surface high harmonics on the carrier envelope phase (CEP) of the driving infrared laser field, we experimentally determined the optimum conditions for the generation of intense isolated attosecond pulses.
Electron backscattering is introduced as mechanism to enhance high-harmonic generation in solid-state like systems with broken translational symmetry. As a paradigmatic example we derive for a finite chain of $N$ atoms the harmonic cut-off through backscattering of electrons in the conduction band from the edges of the chain. We also demonstrate a maximum in the yield of the high harmonics from the conduction band if twice the quiver amplitude of the driven electrons equals the length of the chain. High-harmonic spectra as a function of photon energy are shown to be equivalent if the ratio of chain length to the wavelength of the light is kept constant. Our quantum results are corroborated by a (semi-)classical trajectory model with refined spatial properties required to describe dynamics with trajectories in the presence of broken translational symmetry.
The present work reports on the generation of short-pulse coherent extreme ultraviolet radiation of controlled polarization. The proposed strategy is based on high-order harmonics generated in pre-aligned molecules. Field-free molecular alignment produced by a short linearly-polarized infrared laser pulse is used to break the isotropy of a gas medium. Driving the aligned molecules by a circularly-polarized infrared pulse allows to transfer the anisotropy of the medium to the polarization of the generated harmonic light. The ellipticity of the latter is controlled by adjusting the angular distribution of the molecules at the time they interact with the driving pulse. Extreme ultraviolet radiation produced with high degree of ellipticity (close to circular) is demonstrated.
We present a method to distinguish the high harmonics generated in individual half-cycle of the driving laser pulse by mixing a weak ultraviolet pulse, enabling one to observe the cutoff of each half-cycle harmonic. We show that the detail information of the driving laser pulse, including the laser intensity, pulse duration and carrier-envelope phase, can be {it in situ} retrieved from the harmonic spectrogram. In addition, our results show that this method also distinguishes the half-cycle high harmonics for a pulse longer than 10 fs, suggesting a potential to extend the CEP measurement to the multi-cycle regime.
We report on the global temporal pulse characteristics of individual harmonics in an attosecond pulse train by means of photo-electron streaking in a strong low-frequency transient. The scheme allows direct retrieval of pulse durations and first order chirp of individual harmonics without the need of temporal scanning. The measurements were performed using an intense THz field generated by tilted phase front technique in LiNbO_3 . Pulse properties for harmonics of order 23, 25 and 27 show that the individual pulse durations and linear chirp are decreasing by the harmonic order.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
