1 research outputs found
High Harmonic Generation without Tunnel-Ionization
A new High Harmonic Generation (HHG) scheme, which doesn't rely on
Tunnel-Ionization as the ionization mechanism but rather on Single-Photon
Ionization, is theoretically proposed and numerically demonstrated. The scheme
uses two driver fields: an extreme-ultraviolet driver which induces the
ionization, and a circularly-polarized, co-rotating, two-color infrared driver
carried at a fundamental frequency and its second harmonic which induces the
recollision. Using Classical and time-dependent Schr\"odinger equation
simulations of a model Argon atom, we show that in this scheme ionization is
essentially decoupled from recollision. Releasing the process from being
Tunneling-dependent reduces its degree of nonlinearity, which offers new
capabilities in attosecond science, such as generation of High Harmonics from
highly-charged ions, or from specific deep core electronic levels. It is shown
that the emitted high harmonics involve the absorption of photons of one color
of the infrared driver, and the emission of photons of the second color. This
calls for future examination of the possible correlations between the emitted
high harmonics