28 research outputs found
Breathing solitary-pulse pairs in a linearly coupled system
It is shown that pairs of solitary pulses (SPs) in a linearly-coupled system
with opposite group-velocity dispersions form robust breathing bound states.
The system can be realized by temporal-modulation coupling of SPs with
different carrier frequencies propagating in the same medium, or by coupling of
SPs in a dual-core waveguide. Broad SP pairs are produced in a virtually exact
form by means of the variational approximation. Strong nonlinearity tends to
destroy the periodic evolution of the SP pairs.Comment: Optics Letters, in pres
Photonic quasicrystals for general purpose nonlinear optical frequency conversion
We present a general method for the design of 2-dimensional nonlinear
photonic quasicrystals that can be utilized for the simultaneous phase-matching
of arbitrary optical frequency-conversion processes. The proposed scheme--based
on the generalized dual-grid method that is used for constructing tiling models
of quasicrystals--gives complete design flexibility, removing any constraints
imposed by previous approaches. As an example we demonstrate the design of a
color fan--a nonlinear photonic quasicrystal whose input is a single wave at
frequency and whose output consists of the second, third, and fourth
harmonics of , each in a different spatial direction
Two-center Interferences in Photoionization of Dissociating H Molecule
We analyze two-center interference effects in the yields of ionization of a
dissociating hydrogen molecular ion by an ultrashort VUV laser pulse. To this
end, we performed numerical simulations of the time-dependent Schr\"odinger
equation for a H model ion interacting with two time-delayed laser
pulses. The scenario considered corresponds to a pump-probe scheme, in which
the first (pump) pulse excites the molecular ion to the first excited
dissociative state and the second (probe) pulse ionizes the electron as the ion
dissociates. The results of our numerical simulations for the ionization yield
as a function of the time delay between the two pulses exhibit characteristic
oscillations due to interferences between the partial electron waves emerging
from the two protons in the dissociating hydrogen molecular ion. We show that
the photon energy of the pump pulse should be in resonance with the transition and the pump pulse duration should not exceed 5 fs in
order to generate a well confined nuclear wavepacket. The spreading of the
nuclear wavepacket during the dissociation is found to cause a decrease of the
amplitudes of the oscillations as the time delay increases. We develop an
analytical model to fit the oscillations and show how dynamic information about
the nuclear wavepacket, namely velocity, mean internuclear distance and
spreading, can be retrieved from the oscillations. The predictions of the
analytical model are tested well against the results of our numerical
simulations
Two-center interferences in photoionization of a dissociating H2+ molecule
We analyze two-center interference effects in the yields of ionization of a dissociating hydrogen molecular ion by an ultrashort vuv laser pulse. To this end, we performed numerical simulations of the time-dependent Schrödinger equation for a H2+ model ion interacting with two time-delayed laser pulses. The scenario considered corresponds to a pump-probe scheme, in which the first (pump) pulse excites the molecular ion to the first excited dissociative state and the second (probe) pulse ionizes the electron as the ion dissociates. The results of our numerical simulations for the ionization yield as a function of the time delay between the two pulses exhibit characteristic oscillations due to interferences between the partial electron waves emerging from the two protons in the dissociating hydrogen molecular ion. We show that the photon energy of the pump pulse should be in resonance with the σg−σu transition and the pump pulse duration should not exceed 5 fs in order to generate a well-confined nuclear wave packet. The spreading of the nuclear wave packet during the dissociation is found to cause a decrease of the amplitudes of the oscillations as the time delay increases. We develop an analytical model to fit the oscillations and show how dynamic information about the nuclear wave packet, namely, velocity, mean internuclear distance, and spreading, can be retrieved from the oscillations. The predictions of the analytical model are tested well against the results of our numerical simulations