We demonstrate efficient optical parametric amplification and generation in a gas-filled hollow-core fiber of near-infrared pulses, peaked at 1.4 microm wavelength, with 5 microJ energy and 45 fs duration at the fiber output. Numerical simulations confirm that the OPA is phase matched through excitation of higher-order fiber modes.

We demonstrate that multiple spectral-shearing interferometry increases the precision and accuracy of measurements of the spectral phase of a complex pulse (time-bandwidth product = 125) arising from self-phase modulation in a gas filled capillary. We verify that the measured interferometric phase is accurate to 0.1 rad across the full bandwidth by checking the consistency between the spectral phases of each individual shear measurement. The accuracy of extracting pulse parameters (group delay dispersion, pulse duration and peak intensity) for single shear measurements were verified to better than 10% by comparison with the multishear reconstruction. High order space-time coupling is quantified across a single transverse dimension, verifying the suitability of such pulses for use in strong field experiments.

Atomically thin MoS 2 nanosheets are of interest due to unique electronic, optical, and catalytic properties that are absent in the bulk material. Methods to prepare nanosheets from bulk material that facilitate studies of 2D-MoS 2 and the fabrication of useful devices have consequently assumed considerable importance. Here, we report the simultaneous exfoliation and stable dispersion of MoS 2 nanosheets in a liquid crystal. Exfoliation of bulk MoS 2 in mesogen-containing solutions produced stable dispersions of 2D-MoS 2 that retained suspension stability for several weeks. Solvent removal in cast films yielded nanocomposites of 2D-MoS 2 . Preservation of single-and few-sheet MoS 2 was confirmed utilizing UV−vis and Raman spectroscopy in the nematic and isotropic fluid states of the system and, remarkably, in the solid crystal as well. Importantly, the MoS 2 nanosheets remained welldispersed upon polymerization of the reactive mesogen to form a liquid crystal polymer. The ability to stably disperse 2D-MoS 2 in a structured fluid opens up new possibilities for studying anisotropic properties of MoS 2 and for exploiting such properties in responsive materials.

We study ionization of molecules by an intense laser field over a broad wavelength regime, ranging from 0.8 to 1.5 μm experimentally and from 0.6 to 10 μm theoretically. A reaction microscope is combined with an optical parametric amplifier to achieve ionization yields in the near-infrared wavelength regime. Calculations are done using the strong-field S-matrix theory and agreement is found between experiment and theory, showing that ionization of many molecules is suppressed compared to the ionization of atoms with identical ionization potentials at near-infrared wavelengths at around 0.8 μm, but not at longest wavelengths (10 μm). This is due to interference effects in the electron emission that are effective at low photoelectron energies but tend to average out at higher energies. We observe the transition between suppression and nonsuppression of molecular ionization in the near-infrared wavelength regime (1-5 μm).

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