نتایج جستجو برای: hhg
تعداد نتایج: 293 فیلتر نتایج به سال:
High-resolution imaging is an invaluable tool for understanding nanoscale systems. In particular, tabletop extreme ultraviolet (EUV) coherent diffractive imaging (CDI) techniques based on high harmonic generation (HHG) can combine femtosecond (fs) pulse durations with nanometer resolution and elemental-, spin-, electronicand magnetic-sensitivity, proving to be an ideal probe of complex nanostru...
In this study, we present a new multi-band image representation for improving AAM segmentation accuracy for illumination invariant face alignment. AAM is known to be very sensitive to the illumination variations. We have shown that edges, originating from object boundaries are far less susceptible to illumination changes. Here, we propose a contour selector which mostly collects contours origin...
Generating Carrier-Envelope-Phase Stabilized Few-Cycle Pulses from a Free-Electron Laser Oscillator.
We propose a scheme to generate carrier-envelope-phase (CEP) stabilized few-cycle optical pulses from a free-electron laser oscillator. The CEP stabilization is realized by the continuous injection of CEP-stabilized seed pulses from an external laser to the free-electron laser oscillator whose cavity length is perfectly synchronized to the electron bunch repetition. Operated at a midinfrared wa...
High-harmonic generation (HHG) traditionally combines ~100 near-infrared laser photons to generate bright, phase-matched, extreme ultraviolet beams when the emission from many atoms adds constructively. Here, we show that by guiding a mid-infrared femtosecond laser in a high-pressure gas, ultrahigh harmonics can be generated, up to orders greater than 5000, that emerge as a bright supercontinuu...
Since the discovery of high-order harmonic generation (HHG) in solids1–3, much effort has been devoted to understand its mechanism and both inter- intraband transitions are known be essential1–10. However, affected by electronic structure a solid, how they contribute nonlinear carrier HHG remains an open question. Here we use mid-infrared laser pulses study CdSe CdS quantum dots, where confinem...
We present an ab initio three-dimensional quantum study of the coherent control of high-order harmonic generation ~HHG! processes in intense pulsed laser fields by means of the genetic algorithm optimization of the laser-pulse amplitude and phase. Accurate time-dependent wavefunction and HHG power spectrum are obtained by the time-dependent generalized pseudospectral method and wavelet transfor...
Strong field high harmonic generation (HHG) can reveal the quantum structure of the source molecule. We calculate the effect of interference between the recombining photoelectron and the orbital from which it was field ionized in the single-active-electron standard picture of HHG in N2 and CO2. We compare our results for the highest occupied molecular orbitals (HOMO’s) to the predictions of a p...
High-order harmonic generation (HHG) from aligned molecules has provided a promising way to probe the molecular orbital with an Ångström resolution. This method, usually called molecular orbital tomography (MOT) replies on a simple assumption of the plane-wave approximation (PW), which has long been questioned due to that PW approximation is known to be valid in the keV energy region. However, ...
We present a theoretical investigation of carrier-wave Rabi flopping in real atoms by employing numerical simulations of high-order harmonic generation (HHG) in alkali species. Given the short HHG cutoff, related to the low saturation intensity, we concentrate on the features of the third harmonic of sodium (Na) and potassium (K) atoms. For pulse areas of 2π and Na atoms, a characteristic uniqu...
We report theoretical calculations of high-order harmonic generation (HHG) of Xe with the inclusion of multielectron effects and macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. By using the time-frequency analysis we show that the reshaping of the fundamental laser field is responsible for the continuum structure in the HHG spectra. We further suggest a met...
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