Line shapes observed in attosecond transient absorption spectra (ATAS) encode information on the phase of the optical dipole response. Understanding and controlling the phase evolution of interference fringes is among the fundamental goals of exploring coherent interaction. Here, we simulate the attosecond transient absorption in the near-infrared (NIR) dressing field by considering a three-level model in the adiabatic approximation. We find that the absorption line shape can be changed from Lorentzian to Fano to inverted Lorentzian and back again at two-photon dressed energy levels “ω ± 2ωι”, and line shapes evolve in half-cycle periodicity (T/2). Moreover, the direction of phase evolution of “ω ± 2ωι” is opposite, while the phases of “ω ± 2ωι” are roughly the same at certain delays with an interval of approximately a quarter-cycle periodicity (T/4). These results demonstrate that absorbance of two-photon dressed energy levels “ω ± 2ωι” can qualitatively map the AC Stark shift. These observations provide new insights into the control of spectral line shapes and open the way for the modulation of quantum optical interference in the laser-driven atom.
Laser induced air-plasma is a simple and convenient source to generate intense terahertz (THz) waves through the ionization of gaseous molecules. However, the lack of enhancement and efficient frequency modulation methods for this source hinders its widespread application. Recently, we have shown that the two crossed two-color air-plasmas can significantly increase the THz wave generation or select the required THz emissions under the suitable time delay between the two identical ones (the same intensities of the two-color lasers and the same relative phase between them). In the latest research, we change one of the input laser pulses to generate the two crossed air-plasmas from the twocolors (800 nm + 400 nm) to only the single 800 nm. Interestingly, unlike the results we reported in our previous paper, no spectral interference fringe is observed in the THz spectrum, suggesting that it exhibits no interference between THz waves radiated from single-color and two-color laser generated filaments. For THz waves radiated by single-color laser generated plasma, both the absorption and radiation are related to the plasma frequency. However, the THz waves generated from the two-color laser fields appear to be quite different from the single-color one, thus leading to the absence of spectral interference. Research into the underlying mechanisms will reveal more on the plasma-based THz technology, promising to increase the THz intensity yield and deepening our understanding of the ultrafast dynamics.
All-dielectric metasurfaces exhibit high damage thresholds and strong enhancement of the driving field, making them attractive platforms to Terahertz generation at the nanoscale. Here we report terahertz electric field from lithium niobate metasurface is enhanced by more than one order of magnitude compared to unpatterned samples. The enhanced terahertz are highly anisotropic with respect to the excitation polarization and are selective by the excitation wavelength due to its resonant features. By combining nanofabrication technology and ultrafast optics, our work paves the way for the design of new compact terahertz photonic devices that operate under high intensities and at short wavelengths.
We present an enhanced scheme of polarization-sensitive THz-ABCD which can provide about twice broader
bandwidth than the conventional method. In our experiment using a 26 fs laser pulse, compared with 0.3~40 THz in the
conventional scheme, bandwidth coverage from 0.3 to 80 THz has been achieved in the resolution-enhanced scheme. It
also should have to be noted the terahertz source may also restrict the detection bandwidth. Employing the polarizationsensitive
technology, the polarization in time domain, as well as the field amplitude, can be achieved with just one single
scan.
Angle-resolved photoelectron spectra of argon atoms by XUV attosecond pulses in the presence of a circularly polarized laser field are calculated to examine their dependence on the duration and the chirp of the attosecond pulses. From the calculated electron spectra, we show how to retrieve the duration and the chirp of the attosecond pulse using genetic algorithm. The method is expected to be used for
characterizing the attosecond pulses which are produced by polarization gating of few-cycle left- and right-circularly polarized infrared laser pulses.
Conference Committee Involvement (8)
Infrared, Millimeter-Wave, and Terahertz Technologies XII
12 October 2025 | Beijing, China
Infrared, Millimeter-Wave, and Terahertz Technologies XI
13 October 2024 | Nantong, Jiangsu, China
Infrared, Millimeter-Wave, and Terahertz Technologies X
15 October 2023 | Beijing, China
Infrared, Millimeter-Wave, and Terahertz Technologies IX
5 December 2022 | Online Only, China
Infrared, Millimeter-Wave, and Terahertz Technologies VIII
10 October 2021 | Nantong, JS, China
Infrared, Millimeter-Wave, and Terahertz Technologies VII
12 October 2020 | Online Only, China
Infrared, Millimeter-Wave, and Terahertz Technologies VI
21 October 2019 | Hangzhou, China
Infrared, Millimeter-Wave, and Terahertz Technologies V
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