48 research outputs found
Optimisation of Quantum Trajectories Driven by Strong-field Waveforms
Quasi-free field-driven electron trajectories are a key element of
strong-field dynamics. Upon recollision with the parent ion, the energy
transferred from the field to the electron may be released as attosecond
duration XUV emission in the process of high harmonic generation (HHG). The
conventional sinusoidal driver fields set limitations on the maximum value of
this energy transfer, and it has been predicted that this limit can be
significantly exceeded by an appropriately ramped-up cycleshape. Here, we
present an experimental realization of such cycle-shaped waveforms and
demonstrate control of the HHG process on the single-atom quantum level via
attosecond steering of the electron trajectories. With our optimized optical
cycles, we boost the field-ionization launching the electron trajectories,
increase the subsequent field-to-electron energy transfer, and reduce the
trajectory duration. We demonstrate, in realistic experimental conditions, two
orders of magnitude enhancement of the generated XUV flux together with an
increased spectral cutoff. This application, which is only one example of what
can be achieved with cycle-shaped high-field light-waves, has farreaching
implications for attosecond spectroscopy and molecular self-probing
20-fs 1.6-mJ pulses from a cw-diode-pumped single-stage 1-kHz Yb amplifier
200-fs 2.5-mJ pulses from a fiber-oscillator-seeded DPSS Yb:CaF2 MOPA are spectrally broadened in Ar and recompressed to 20 fs using a pair of LAK14 prisms. Multi-millijoule 12-fs pulses are feasible upon higher-order spectral phase correction. © 2010 Optical Society of America
Mid-infrared laser filaments in the atmosphere
Filamentation of ultrashort laser pulses in the atmosphere offers unique
opportunities for long-range transmission of high-power laser radiation and
standoff detection. With the critical power of self-focusing scaling as the
laser wavelength squared, the quest for longer-wavelength drivers, which would
radically increase the peak power and, hence, the laser energy in a single
filament, has been ongoing over two decades, during which time the available
laser sources limited filamentation experiments in the atmosphere to the
near-infrared and visible ranges. Here, we demonstrate filamentation of
ultrashort mid-infrared pulses in the atmosphere for the first time. We show
that, with the spectrum of a femtosecond laser driver centered at 3.9 um, right
at the edge of the atmospheric transmission window, radiation energies above 20
mJ and peak powers in excess of 200 GW can be transmitted through the
atmosphere in a single filament. Our studies reveal unique properties of
mid-infrared filaments, where the generation of powerful mid-infrared
supercontinuum is accompanied by unusual scenarios of optical harmonic
generation, giving rise to remarkably broad radiation spectra, stretching from
the visible to the mid-infrared
30-fs 1.6 mJ Pulses at a kHz repetition rate from a single stage DPSS Yb amplifier
200-fs 2.5-mJ pulses from a cw-diode-pumped Yb:CaF2 MOPA are spectrally broadened in Ar and recompressed to 30 fs at 980 nm using a prism pair. Multi-millijoule 12-fs pulses are feasible upon higher-order spectral phase correction. © 2010 Optical Society of America