Publications (6)3.4 Total impact
Article: Generation of narrow-bandwidth, tunable, coherent xuv radiation using high-order harmonic generation[show abstract] [hide abstract]
ABSTRACT: We theoretically demonstrate the generation of wavelength-tunable, narrow-bandwidth extreme-ultraviolet (xuv) radiation by high-order harmonic generation (HHG) driven by an orthogonally polarized two-color laser field, which is composed of a 10-fs, 1500-nm laser pulse and a 40-fs, 2400-nm laser pulse. By performing classical analysis, we reveal that the rapid change of electron wave-packet dynamics at a subcycle time scale confines high-order harmonic emission to a small spectral region, leading to the generation of narrow-bandwidth xuv radiation. Furthermore, the central wavelength of the xuv radiation can be continuously tuned over a wide range by changing either the peak intensity of the driver laser or the amplitude ratio between the two laser fields at different wavelengths. It is also verified that the use of driver pulses at longer wavelengths leads to a better spectral confinement of the xuv radiation.Phys. Rev. A. 03/2011; 83(3).
Article: Generation of an XUV supercontinuum by optimization of the angle between polarization planes of two linearly polarized pulses in a multicycle two-color laser field[show abstract] [hide abstract]
ABSTRACT: We theoretically investigate the high-order harmonic generation (HHG) in helium using a two-color laser field synthesized by an intense 25-fs laser pulse at 800 nm and a relatively weak ∼ 43-fs laser pulse at 1400 nm. When the polarization between the two pulses is arranged at an angle of ∼ 73 • , supercontinuum spectra are dramatically broadened to 180 eV, which is sufficient to support an isolated ∼73-as pulse without any phase compensation. The physical mechanisms behind the phenomenon are well explained in terms of quantum and classical analyses. Furthermore, in the long-pulse regime, this method of extending the supercontinuum spectrum shows the significant advantage over previous two-color HHG schemes.01/2010; 82.
Article: Generation of a coherent x ray in the water window region at 1 kHz repetition rate using a mid-infrared pump source.[show abstract] [hide abstract]
ABSTRACT: We demonstrate the generation of a coherent x ray in the water window region in a gas cell filled with neon gas using a wavelength-tunable mid-IR femtosecond laser operating at 1 kHz repetition rate. The cutoff energy and conversion efficiency of the water window x ray can be optimized by tuning gas pressure as well as the focal position.Optics Letters 07/2009; 34(11):1747-9. · 3.40 Impact Factor
Article: Unexpected breakdown of the simple man's model for strong-field photoionization in the high-energy recollision region[show abstract] [hide abstract]
ABSTRACT: We present experimental and theoretical evidence on the breakdown of the simple man's model in the high-energy recollision region by examining both the energy-resolved angular distribution of photoelectrons in above-threshold ionization and the spectrum of high-order harmonics generated in elliptically polarized driver fields. With the help of a semiclassical model calculation, we show that, surprisingly, even for the high-energy recollision electrons, their wave-packet dynamics can be influenced strongly by the Coulomb field.Phys. Rev. A. 85(2).
Article: Single attosecond pulse generation from aligned molecules using two-color polarization gating[show abstract] [hide abstract]
ABSTRACT: We theoretically investigate high-order harmonic generation from the diatomic molecules in an orthogonally polarized two-color few-cycle optical field by controlling the incident angle of the recolliding electron. We show that the combination of molecules and two-color polarization gating allows us to significantly suppress undesirable satellite pulses owing to the orientation dependence of high-order harmonic generation in mol-ecules, giving rise to the generation of single attosecond pulses.
Article: Phase-matched high-order harmonic generation in a gas cell with midinfrared femtosecond pulses[show abstract] [hide abstract]
ABSTRACT: We experimentally investigate the generation of high-order harmonics in a 4-mm-long gas cell using mid-infrared femtosecond pulses at various wavelengths of 1240 nm, 1500 nm, and 1800 nm. It is observed that the yield and cutoff energy of the generated high-order harmonics critically depend on focal position, gas pressure, and size of the input beam which can be controlled by an aperture placed in front of the focal lens. By optimizing the experimental parameters, we achieve a cutoff energy at 190 eV with the 1500 nm driving pulses, which is the highest for the three wavelengths chosen in our experiment.