473 research outputs found
Field-cycle-resolved photoionization in solids
The Keldysh theory of photoionization in a solid dielectric is generalized to
the case of arbitrarily short driving pulses of arbitrary pulse shape. We
derive a closed-form solution for the nonadiabatic ionization rate in a
transparent solid with a periodic dispersion relation, which reveals ultrafast
ionization dynamics within the field cycle and recovers the key results of the
Keldysh theory in the appropriate limiting regimes.Comment: 4 pages, 2 figure
Main Elements of Logistics
Virtually lossless self-compression of 10-mJ 3.9-um sub-100 fs pulses in bulk YAG resulting in 9-mJ 33-fs pulses is reported. Generated peak power exceeds 250 GW which is suitable for filamentation in ambient air
CEP-stable Tunable THz-Emission Originating from Laser-Waveform-Controlled Sub-Cycle Plasma-Electron Bursts
We study THz-emission from a plasma driven by an incommensurate-frequency
two-colour laser field. A semi-classical transient electron current model is
derived from a fully quantum-mechanical description of the emission process in
terms of sub-cycle field-ionization followed by continuum-continuum electron
transitions. For the experiment, a CEP-locked laser and a near-degenerate
optical parametric amplifier are used to produce two-colour pulses that consist
of the fundamental and its near-half frequency. By choosing two incommensurate
frequencies, the frequency of the CEP-stable THz-emission can be continuously
tuned into the mid-IR range. This measured frequency dependence of the
THz-emission is found to be consistent with the semi-classical transient
electron current model, similar to the Brunel mechanism of harmonic generation
Power-scalable subcycle pulses from laser filaments
Compression of optical pulses to ultrashort pulse widths using methods of nonlinear optics is a well-established technology of modern laser science. Extending these methods to pulses with high peak powers, which become available due to the rapid progress of laser technologies, is, however, limited by the universal physical principles. With the ratio P/P(cr) of the peak power of an ultrashort laser pulse, P, to the critical power of self-focusing, P(cr), playing the role of the fundamental number-of-particles integral of motion of the nonlinear Schrödinger equation, keeping this ratio constant is a key principle for the power scaling of laser-induced filamentation. Here, we show, however, that, despite all the complexity of the underlying nonlinear physics, filamentation-assisted self-compression of ultrashort laser pulses in the regime of anomalous dispersion can be scaled within a broad range of peak powers against the principle of constant P/P(cr). We identify filamentation self-compression scaling strategies whereby subcycle field waveforms with almost constant pulse widths can be generated without a dramatic degradation of beam quality within a broad range of peak powers, varying from just a few to hundreds of P(cr)
Probing Ultra-Fast Dephasing via Entangled Photon Pairs
We demonstrate how the Hong-Ou-Mandel (HOM) interference with
polarization-entangled photons can be used to probe ultrafast dephasing. We can
infer the optical properties like the real and imaginary parts of the complex
susceptibility of the medium from changes in the position and the shape of the
HOM dip. From the shift of the HOM dip, we are able to measure 22 fs dephasing
time using a continuous-wave (CW) laser even with optical loss > 97%, while the
HOM dip visibility is maintained at 92.3~\% (which can be as high as 96.7%).
The experimental observations, which are explained in terms of a rigorous
theoretical model, demonstrate the utility of HOM interference in probing
ultrafast dephasing.Comment: 12 pages, 7 figure
Ultralow-power local laser control of the dimer density in alkali-metal vapors through photodesorption
Ultralow-power diode-laser radiation is employed to induce photodesorption of
cesium from a partially transparent thin-film cesium adsorbate on a solid
surface. Using resonant Raman spectroscopy, we demonstrate that this
photodesorption process enables an accurate local optical control of the
density of dimer molecules in alkali-metal vapors.Comment: 4 pages, 4 figure
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