Light-induced states in attosecond transient absorption spectra of laser-dressed helium

Laser-dressed absorption in atomic helium is studied, both theoretically and experimentally, by transient absorption spectroscopy using isolated 400-as pulses centered at 22 eV and 12-fs near-infrared (NIR) pulses with 780-nm central wavelength. Multiple features in the helium singly excited bound-state spectrum are observed only when the NIR and attosecond pulses are overlapped in time. Theoretical analysis indicates that these light-induced structures (LISs) are the intermediate states in resonant, second-order processes that transfer population to multiple dipole forbidden states. The use of broadband, coherent extreme ultraviolet (XUV) radiation allows observation of these LISs without specifically tuning to a two-photon resonance, as would be required with narrowband XUV light. The strength and position of the LISs depend strongly on the NIR intensity and the pump-probe delay. © 2012 American Physical Society

Stabilizing the carrier-envelope phase of a 30 fs, 1 kHz, 6 mJ Ti: sapphire regenerative amplifier

Carrier-envelope phase stabilization of a two-stage chirped pulse amplifier laser system with regenerative amplification as the preamplifier is demonstrated with a 90 mrad rms error for a locking period of 4.5 h

Electric dipole oscillation in solids characterized by Fourier transform extreme ultraviolet attosecond spectroscopy

We characterized electronic dipole oscillations in chromium doped sapphire (Cr:Al2O3) using Fourier transform extreme ultraviolet attosecond spectroscopy (FTXUV) combined with an isolated attosecond pulse, which reveals the electric band-structure and dephasing process in solids

Electric dipole oscillation in solids characterized by Fourier transform extreme ultraviolet attosecond spectroscopy

We characterized electronic dipole oscillations in chromium doped sapphire (Cr:Al2O3) using Fourier transform extreme ultraviolet attosecond spectroscopy (FTXUV) combined with an isolated attosecond pulse, which reveals the electric band-structure and dephasing process in solids

Multi-petahertz electron interference in Cr:Al2O3 solid-state material

Signal processing in electronic devices is in the THz regime. Here the authors measure NIR lightwave-field-induced multiple dipole oscillations in Cr:Al2O3 in the time domain reaching PHz scale by using an isolated attosecond pulse and this method shows potential for higher speed signal processing

High-order Nonlinear Dipole Response Characterized by Extreme-Ultraviolet Ellipsometry

Polarization engineering and characterization of coherent high-frequency radiation are essential to investigate and control the symmetry properties of light–matter interaction phenomena at their most fundamental scales. This work demonstrates that polarization control and characterization of high-harmonic generation provides an excellent ellipsometry tool that can fully retrieve both the amplitude and phase of a strong-field-driven dipole response. The polarization control of high-harmonic generation is realized by a transient nonlinear dipole grating coherently induced by two noncollinear counterrotating laser fields.By adjusting the ellipticity of the two driving pulses simultaneously, the polarization state of every high-harmonic order can be tuned from linear to highly elliptical, and it is fully characterized through an energy-resolved extreme ultraviolet polarimeter. From the analysis of the polarization state, the ellipsometry indicated that both the amplitude and phase of the high-harmonic dipole scale rapidly with the driving laser field for higher-order harmonics, and, especially, for gases with a small ionization potential. Our experimental results were corroborated by theoretical simulations. Our findings revealed a novel high-harmonic ellipsometry technique that can be used for the next generation of high-harmonic spectroscopy and attosecond metrology studies because of its ability to provide single-digit attosecond accuracy.Our work also paves the way to precisely quantify the strong-field dynamics of fundamental processes associated with the transfer of energy and angular momentum between electron/spin systems and the symmetry-dependent properties of molecules and materials.Ministry of Science and Technology (109-2634-F-007-023, 109-2636-M-007-008); Ministry of Education; Japan Society for the Promotion of Science KAKENHI (JSPS) (19H02637, 20H05670); Ministerio de Ciencia e Innovación y Universidades (FIS2016-75652-P, PID2019-106910GB-I00, RYC-2017-22745); Junta de Castilla y León FEDER (SA287P18); Ministerio de Educación, Cultura y Deporte (FPU16/02591); H2020 European Research Council (ERC) (851201)