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  • Using the autocorrelator, few-cycle laser pulses compressed by chirped mirrors were measured. The FWHM pulse duration is 4.3 fs with 0.37 mJ pulse energy.

    Autocorrelation trace (4.3 fs)Scanning Autocorrelator

    Inside XUV chamber

    Double mirrors focus both femtosecond IR pulse and attosecond XUV pulse to Ne gas target . Electron signal is measured by TOF while the delay is being scanned

    FEMTOPOWER (FemtoLaser) delivers 25 fs laser pulse of 1.5 mJ energy per pulse. Rep.rate is 3 kHz and center wavelength is 795 nm. Carrier envelope phase (CEP) is stabilized.`

    FEMTOPOWER laser

    Jaeuk Heo1,2 (허재욱), Byunghoon Kim2 (김병훈) and Done Eon Kim1,2 (김동언) 1Department of Physcis, POSTECH, 77 Cheongam-Ro, Nam-gu. Pohang. Gyeongbuk 37673, Republic of Korea

    2Max Planck Center for Attosecond Science, Max Planck POSTECH/KOTEA Res. Init., Pohang 37673, Republic of Korea

    showerpurple@Postech.ac.kr

    Ultrafast Dynamics in Attosecond Atomic Physics Beam-line at POSTECH

    Octave spanning spectrum (400~1000 nm) has been obtained by using Ne gas (3.5 bar) filled hollow core fiber. The output pulse energy is 0.57 mJ

    Nonlinear interaction of few-cycle laser with Ne gas (0.2 bar) results high-order harmonic radiation which converts the photon energy to XUV level.

    Ne gas cellHHG vacuum chamber

    Retrieved streaking signal for attosecond XUV pulse3 Analyzed result (500 as)

    ATAS scheme

    Rotating Wave Approximation (RWA) breaks down in high field, resulting in new feature of Counter Rotating Wave (CRW) effect.

    �̰� = 𝛥 0 0 0

    + 𝛺

    2

    0 1 1 0

    + 𝛺

    2

    0 𝑒−2𝑖𝜔𝑡

    𝑒−2𝑖𝜔𝑡 0

    (a)As ratio of Rabi frequency to the control field

    frequency ( 𝛺

    ω ) increases, the oscillating features

    become more prominent.

    (b) As the scaling increases, the oscillating effect ( 𝛺

    ω )

    diminishes considerably.

    Calculation results for difference pulse width (5.3 fs, 21.3 fs). For both cases, the field

    strength ( 𝛺

    ω ) is kept the

    same,

    Streaking with TOF scheme

    ∆ : detuning in frequency, Ω(=µ E) : the Rabi frequency, µ is the transition dipole moment, ω : transition frequency

    ‘2ω oscillation’ • ‘Autler-Townes splitting’ • ‘Asymmetric splitting’ can be seen.

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