We present the perfect waveform which, during a strong field interaction, generates maximum possible electron recollision energy for any given oscillation period, over 3 times as high that pure sinusoidal wave. This ideal has form of linear ramp with dc offset. A genetic algorithm was employed to find an optimized practically achievable composed longer wavelength field, provide offset, in addition higher frequency components. second is found be capable generating energies those while...

Quasi-free field-driven electron trajectories are a key element of strong-field dynamics. Upon recollision with the parent ion, energy transferred from field to may be released as attosecond duration XUV emission in process high harmonic generation (HHG). The conventional sinusoidal driver fields set limitations on maximum value this transfer, and it has been predicted that limit can significantly exceeded by an appropriately ramped-up cycleshape. Here, we present experimental realization...

We report observations and analysis of high harmonic generation driven by a superposition fields at 1290 nm 780 nm. These are not commensurate in frequency the leads to an increase yield mid-plateau harmonics more than two orders magnitude compared using field alone. Significant extension cut-off photon energy is seen even adding only small amount field. explained calculations performed strong approximation. Most importantly we find that enhancement found arise as consequence both increased...

Control over the polarization of an attosecond pulse train (APT) is demonstrated theoretically using orthogonally polarized two-color fields. The carrier envelope phase two pulses used as a control parameter to generate both APT with linear in nearly perpendicular planes or elliptically alternating helicity. By few-cycle driving laser fields isolated elliptical shown be generated after selecting cut-off region harmonic spectrum. mechanism explained terms classical trajectories.

We combine phase-locked femtosecond pulses with 1.5 µm, 1.0 µm and 0.5 wavelength to shape optical cycles experimentally realize the concept of "perfect wave for high harmonic generation". This has far-reaching implications attosecond spectroscopy.

Isolated attosecond pulses (IAP) generated by high-order harmonic generation are valuable tools that enable dynamics to be studied on the time scale. The applicability of these IAP would widened drastically increasing their energy. Here we analyze potential using multi-colour driving for temporally gating pulse process. We devise how this approach can with available high-energy kHz-repetition-rate Ytterbium-based laser amplifiers (delivering 180-fs, 1030-nm pulses). show theoretically...

We show how to optimize the process of high-order harmonic generation (HHG) by gating interaction using field gradient driving pulse. Since maximized gradients are efficiently generated self-steepening processes, we first present a generalized theory optical carrier-wave self-steepened (CSS) pulses. This goes beyond existing treatments, which only consider third-order nonlinearity, and has advantage describing pulses whose wave forms have range symmetry properties. Although fertile for...

We demonstrate a novel technique for an extension of the cut-off frequency in high-harmonic generation using shaped field, consisting two delayed pulses, identical all parameters except carrier envelope phase shift π. obtain high harmonics up to energy 5.5Up + Ip, surpassing conventional limit 3.17Up Ip. For intensities approaching threshold barrier suppression ionization, beyond which no are generated, this mechanism acquires practical importance as means overcome imposed by saturation....

We present the first measurement of vectorial response strongly dressed helium atoms probed by an attosecond pulse train (APT) polarised either parallel or perpendicular to dressing field polarisation. The transient absorption is as a function delay between APT and linearly 800 nm peak intensity . spans photon energy range 16–42 eV, covering ionisation (24.59 eV). With probing fields, we observe modulations with periods one half quarter period. When polarisation altered from respect large...

We outline a simple approach for determining plateau positions in harmonic spectra that demonstrates very clearly the requirement carrier–envelope phase and intensity stabilization IR laser pulse reliable attosecond production. Neglecting characteristics of will lead to large variations duration number sub-fs pulses produced via high harmonics cut-off windowing.

Abstract High‐order harmonic spectra are composed of a coherent sum half‐cycle emissions, the cut‐off energy which depend sensitively on different sub‐cycle portions driving laser field. By selecting correct focal geometry emissions can be preferentially selected over lower plateau through phase matching, such that they form macroscopic features in far‐field spectrum. The these cut‐offs then used to retrieve waveform processes formed and their applications, both for measuring generation...

Abstract In the article of L.E. Chipperfield et al. [Phys. Rev. Lett. 2009, 102, 063001], ideal waveform was presented that maximised recollision energy a strong-field driven electron. this paper we expound derivation perfect wave, as well more general for optimising electron trajectories which occurs some distance from place origin. The acts guide synthesises practical waveforms maximise energy, and so extend high-order harmonic cut-off to higher frequencies. Keywords: attosecondstrong...

We investigate high-order harmonic spectra from aligned diatomic molecules in intense driving fields whose components have orthogonal polarizations. focus on how the driving-field ellipticity influences structural interference patterns a macroscopic medium. In previous publication [Phys. Rev. A 88, 023404 (2013)] we shown that non-vanishing introduces an effective dynamic shift angle for which two-center maxima and minima occur, with regard to existing condition linearly polarized fields....

We present transient absorption spectra of an extreme ultraviolet attosecond pulse train in helium dressed by 800 nm laser field with intensity ranging from $2\times10^{12}$ W/cm$^2$ to $2\times10^{14}$ W/cm$^2$. The energy range probed spans 16-42 eV, straddling the first ionisation (24.59 eV). By changing relative polarisation dressing respect we observe a large change modulation reflecting vectorial response field. With parallel polarized and probing fields, significant modulations...

We realize a multicolor, multi-cycle combination of commonly CEP-locked three waves from single femtosecond OPA and report HHG driving with individual combined colors. Employing novel multicolor incommensurate-frequency waveform synthesizer we demonstrate previously theoretically predicted capability to enhance the cut-off position spectrum upscale XUV flux as compared single-color driving.

The paper reports on the observations and analysis of high harmonic generation driven by a superposition fields at 1290 nm 780 nm. These are not commensurate in frequency, as previous experiments leads to an increase yield mid-plateau harmonics more than two orders magnitude compared using field alone. Significant extension cut-off photon energy is seen even adding only small amount field.

We realize a multicolor, multi-cycle combination of commonly CEP-locked three waves from single femtosecond OPA driven by CEP -stable 7-mJ kHz Yb laser system and report HHG driving with individual combined colors.

It is well known that strong field processes, such as high order harmonic generation (HHG), depend upon the sub-optical cycle dynamics of strongly driven electrons. We will discuss some our recent work where electrons are examined using both theoretical and experimental approaches. Techniques for measuring electron from HHG spectrum identified control methods to optimise HHG, which may soon be used in practice, treated theoretically.

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation J. P. Marangos, S. Baker, Robinson, C. A. Haworth, Chirila, M. Lein, L. Chipperfield, W. G. Tisch; Probing Attosecond Dynamics by Laser Driven Electron Recollisions. AIP Conf. Proc. 7 November 2006; 869 (1): 303–311. https://doi.org/10.1063/1.2400661 Download citation file: Ris (Zotero) Reference Manager...