Synchronizing Terahertz Wave Generation with Attosecond Bursts

Zhang, Dongwen; Lü, Zhihui; Meng, Chao; Du, Xin; Zhou, Zhenhua; Zhao, Zengxiu; Yuan, Jianmin

doi:10.1103/physrevlett.109.243002

Cited by 81 publications

(68 citation statements)

References 36 publications

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“…So far, the evidence supports the photocurrent model, in that ionization of the medium is indispensable [13,14], yet the mechanism behind the generation of THz remains unclear. A lot of theoretical calculations have been carried out in the past ten years by solving the time-dependent Schrödinger equation (TDSE) [8,[15][16][17][18] to study the THz signals versus the phase between the two colors of the laser, the intensity of the fundamental and of the second harmonic [17][18][19]. These TDSE calculations have shown consistent results among the studies, but the underlying mechanism remains unclear.…”

Section: Introductionmentioning

confidence: 99%

“…These TDSE calculations have shown consistent results among the studies, but the underlying mechanism remains unclear. While it has been speculated that THz emission can be attributed to the continuum-continuum transition during laser-assisted soft collision of the ionized * zhaoyanz@phys.ksu.edu electron with the atomic core [16,19,20], there is no clear demonstration how this model works.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of THz generation through the asymmetry of photoelectron angular distributions

2017

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We analyze the mechanism of THz generation in a gas medium with intense two-color infrared lasers pulses. The dependence of the amplitude of THz emission on the relative phase between the fundamental color (800 nm) and its second harmonic (400 nm) is shown to be identical to the residual current as well as to the asymmetry of the above-threshold-ionization (ATI) photoelectrons along the left versus the right side of the linear polarization axis of the laser, thus confirming the validity of the semiclassical photocurrent model for the THz emission. We further analyze the even vs odd angular momentum distributions of the ATI electrons. The degree of overlap between the even-parity dominant electrons and the odd-parity dominant electrons within each ATI peak determines the strength of the THz emission, thus favoring the model that THz is generated through free-free transitions in the laser field. A model is also provided to obtain the same phase dependence as the four-wave mixing model.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of THz generation through the asymmetry of photoelectron angular distributions

2017

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“…As a representative case, THz emission in two-color laser fields has been investigated more intensively [14][15][16][17][21][22][23][24][25][26][27][28]. So far, more evidences support the model based on photocurrent as it is found ionization is indispensable [16], although the physics behind photocurrent formation needs to be explored carefully [29]. However, in view of the success of four-wave mixing model in applying to the THz detection through air-breakdown coherent detection scheme [18,30], the two models must be closely connected.…”

Section: Introductionmentioning

confidence: 99%

“…By connecting THz emission with high harmonic generation (HHG) in two-color laser pulses, the dynamics responsible for THz emission is attributed to the continuum-continuum transition during laser-assisted soft collision of the ionized electron with the atomic core, while the hard collision with the atomic core leads to HHG upon recombination [29,30].…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of terahertz generation from atoms and aligned molecules driven by two-color laser fields

et al. 2015

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We study the generation of terahertz radiation from atoms and molecules driven by an ultrashort fundamental laser and its second harmonic field by solving time-dependent Schrödinger equation (TDSE). The comparisons between one-, two-, and three-dimensional TDSE numerical simulations show that initial ionized wave-packet and its subsequent acceleration in the laser field and rescattering with long-range Coulomb potential play key roles. We also present the dependence of the optimum phase delay and yield of terahertz radiation on the laser intensity, wavelength, duration, and the ratio of two-color laser components. Terahertz wave generation from model hydrogen molecules are further investigated by comparing with high harmonic emission. It is found that the terahertz yield is following the alignment dependence of ionization rate, while the optimal two-color phase delays varies by a small amount when the alignment angle changes from 0 to 90 degrees, which reflects alignment dependence of attosecond electron dynamics. Finally we show that terahertz emission might be used to clarify the origin of interference in high harmonic generation from aligned molecules by coincidently measuring the angle-resolved THz yields.

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“…Recently, due to the development of two-color femtosecond air plasma THz-TDS [12][13][14], it has become possible to extend THz-TDS measurements on chalcogenide glasses [15] and water [16] up to 18 THz. Here we report the complex conductivities of ITO, AZO and GZO up to >18 THz covering the important crossover point where the scattering rate equals the frequency, 1 ωτ = , thus allowing precise determination of the scattering time τ .…”

Section: Introductionmentioning

confidence: 99%

Ultrabroadband terahertz conductivity of highly doped ZnO and ITO

Wang¹,

Zalkovskij²,

Iwaszczuk³

et al. 2015

Opt. Mater. Express

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Abstract:The broadband complex conductivities of transparent conducting oxides (TCO), namely aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO) and tin-doped indium oxide (ITO), were investigated by terahertz time domain spectroscopy (THz-TDS) in the frequency range from 0.5 to 18 THz using air plasma techniques, supplemented by the photoconductive antenna (PCA) method. The complex conductivities were accurately calculated using a thin film extraction algorithm and analyzed in terms of the Drude conductivity model. All the measured TCOs have a scattering time below 15 fs. We find that a phonon response must be included in the description of the broadband properties of AZO and GZO for an accurate extraction of the scattering time in these materials, which is strongly influenced by the zinc oxide phonon resonance tail even in the low frequency part of the spectrum. The conductivity of AZO is found to be more thickness dependent than GZO and ITO, indicating high importance of the surface states for electron dynamics in AZO. Finally, we measure the transmittance of the TCO films from 10 to 200 THz with Fourier transform infrared spectroscopy (FTIR) measurements, thus closing the gap between THz-TDS measurements (0.5-18 THz) and ellipsometry measurements (200-1000 THz). ©2015 Optical Society of America

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Synchronizing Terahertz Wave Generation with Attosecond Bursts

Cited by 81 publications

References 36 publications

Analysis of THz generation through the asymmetry of photoelectron angular distributions

Analysis of THz generation through the asymmetry of photoelectron angular distributions

Theoretical study of terahertz generation from atoms and aligned molecules driven by two-color laser fields

Ultrabroadband terahertz conductivity of highly doped ZnO and ITO

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