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Multi-octave, CEP-stable source for high-energy field synthesis

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Science Advances  14 Feb 2020:
Vol. 6, no. 7, eaax3408
DOI: 10.1126/sciadv.aax3408
  • Fig. 1 All-ytterbium frontend for high-average and peak power light transient generation.

    The setup is based on a Yb:YAG thin-disk amplifier, seeded by a Kerr-lens mode-locked thin-disk oscillator. The laser energy (1.8 mJ) is used to directly generate multi-octave, CEP-stable seed pulses. Thereafter, the broadband spectrum is divided into two channels: NIR channel spanning from 700 to 1400 nm and MIR channel covering 1600 to 2500 nm. Each channel is amplified in a single-stage OPCPA pumped by fundamental or second harmonic of the laser and compressed to its Fourier limit. The energy of few-cycle pulses can be increased by adding consecutive OPCPA stages in each channel. Coherent synthesis of the two few-cycle pulses results in generation of light transients. BS, beam splitter; CMs, chirped mirrors; PPLN, periodically poled lithium niobate.

  • Fig. 2 The laser specifications.

    (A) CEP-stable, multi-octave spectrum of seed pulses (red). Amplified spectra of NIR (orange) and MIR (brown) OPCPAs. Retrieved temporal intensity profile and phase of the compressed pulses in (B) NIR and (C) MIR channels. Inset: Measured (top) and retrieved (bottom) FROG spectrograms.

  • Fig. 3 Direct electric field detection.

    (A) Schematic of the linear absorption setup for generating and sampling the FID of water molecules. (B) EOS setup containing a 50-μm-thick BBO (type II) crystal and an ellipsometer. The MIR pulses are chopped at 2.5 kHz. The NIR beam after the delay line is collinearly combined with the MIR beam, and both are focused in the EOS crystal for sum-frequency generation. The generated sum-frequency signal spectrally overlaps and temporally interferes with the high-frequency components of the probe beam. Appropriate spectral filtering is used to enhance the EOS signal. The polarization rotation as a function of time delay is detected using an ellipsometer and read out using a lock-in amplifier. (C) Measured electric field of the MIR pulses in the absence (dark blue curve) and presence of water (light blue curve). Inset: Zoomed plot in a shorter temporal window. WGP, wire grid polarizer; SP, short-pass filter; LP, long-pass filter.

  • Fig. 4 Simulated millijoule light transient.

    Simulated amplified spectra in (A) NIR channel with 1.8 mJ of energy and (B) MIR channel with 2.2 mJ of energy and (C) their calculated synthesized waveform.

  • Table 1 Simulation parameters of the NIR channel.

    Lc, crystal thickness; Ep, input pump energy; Es, amplified signal energy; ωp, pump beam radius (FWHM); ωs, signal beam radius (FWHM).

    StageLc
    (mm)
    Ep
    (mJ)
    Es
    (mJ)
    ωp
    (mm)
    ωs
    (mm)
    Efficiency
    (%)
    2nd2.58.31.31.461.1615.1
    3rd1.06.01.81.281.029.8
  • Table 2 Simulation parameters of the MIR channel.

    StageLc
    (mm)
    Ep
    (mJ)
    Es
    (mJ)
    ωp
    (mm)
    ωs
    (mm)
    Efficiency
    (%)
    2nd2.08.91.31.631.5014.9
    3rd1.06.22.21.421.3413.9

Supplementary Materials

  • Supplementary Materials

    This PDF file includes:

    • Table S1. Simulation parameters of the NIR channel.
    • Table S2. Simulation parameters of the MIR channel.

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