6 results match your criteria: "University of Ottawa and National Research Council of Canada[Affiliation]"

Vectorizing the spatial structure of high-harmonic radiation from gas.

Nat Commun

May 2019

Department of Physics, University of Ottawa, 25 Templeton St., Ottawa, ON, K1N 6N5, Canada.

Strong field laser physics has primarily been concerned with controlling beams in time while keeping their spatial profiles invariant. In the case of high harmonic generation, the harmonic beam is the result of the coherent superposition of atomic dipole emissions. Therefore, fundamental beams can be tailored in space, and their spatial characteristics will be imparted onto the harmonics.

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Optical vortices, which carry orbital angular momentum (OAM), can be flexibly produced and measured with infrared and visible light. Their application is an important research topic for super-resolution imaging, optical communications and quantum optics. However, only a few methods can produce OAM beams in the extreme ultraviolet (XUV) or X-ray, and controlling the OAM on these beams remains challenging.

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Article Synopsis
  • The generation of attosecond pulses typically relies on using infrared wavelengths to access soft X-rays, but longer wavelengths reduce harmonic conversion efficiency, complicating conventional measurements.
  • In-situ measurement techniques have been developed to effectively analyze attosecond pulses, allowing for spatial and temporal characterization of pulses generated from 1.8 μm beams.
  • The study confirms theoretical models, revealing that each beamlet acts as an isolated attosecond pulse and maintains a consistent wavefront curvature across a range of photon energies, with potential scalability to soft X-rays.
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Transition between mechanisms of laser-induced field-free molecular orientation.

Phys Rev Lett

March 2014

Max-Planck Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany and J. R. Macdonald Laboratory, Physics Department, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506, USA.

The transition between two distinct mechanisms for the laser-induced field-free orientation of CO molecules is observed via measurements of orientation revival times and subsequent comparison to theoretical calculations. In the first mechanism, which we find responsible for the orientation of CO up to peak intensities of 8 × 10(13) W/cm(2), the molecules are impulsively oriented through the hyperpolarizability interaction. At higher intensities, asymmetric depletion through orientation-selective ionization is the dominant orienting mechanism.

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Probing polar molecules with high harmonic spectroscopy.

Phys Rev Lett

December 2012

Joint Attosecond Science Laboratory, University of Ottawa and National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada.

We bring the methodology of orienting polar molecules together with the phase sensitivity of high harmonic spectroscopy to experimentally compare the phase difference of attosecond bursts of radiation emitted upon electron recollision from different ends of a polar molecule. This phase difference has an impact on harmonics from aligned polar molecules, suppressing emission from the molecules parallel to the driving laser field while favoring the perpendicular ones. For oriented molecules, we measure the amplitude ratio of even to odd harmonics produced when intense light irradiates CO molecules and determine the degree of orientation and the phase difference of attosecond bursts using molecular frame ionization and recombination amplitudes.

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We produce oriented rotational wave packets in CO and measure their characteristics via high harmonic generation. The wave packet is created using an intense, femtosecond laser pulse and its second harmonic. A delayed 800 nm pulse probes the wave packet, generating even-order high harmonics that arise from the broken symmetry induced by the orientation dynamics.

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