AbstractNumerical solutions of time-dependent Schrödinger equations for one and two electron cyclic molecules H_{n}^{q+} exposed to intense bichromatic circularly polarized laser pulses of frequencies ω_{1} and ω_{2}, such that ω_{1}/ω_{2}=n_{1}/n_{2} (integer) produce circularly polarized high order harmonics with a cut-off recollision maximum energy at and greater than the linear polarization law (in atomic units) N_{m}ω_{1}=I_{p}+3.17U_{p}, where I_{p} is the ionization potential and U_{p}=(2E_{0})^{2}/4ω^{2} is the ponderomotive energy defined by the field E_{0} (intensity I=cE_{0}^{2}/8π) from each pulse and mean frequency ω=(ω_{1}+ω_{2})/2. An electron recollision model in a rotating frame at rotating frequency Δω=(ω_{1}+ω_{2})/2 predicts this simple result as a result of recollision dynamics in a combination of bichromatic circularly polarized pulses. The harmonic helicities and their intensities are shown to depend on compatible symmetries of the net pulse electric fields with that of the molecules. ReferenceA. Bandrauk, F. Mauger and KJ Yuan – Circularly polarized harmonic generation by intense bicircular laser pulses: Electron recollision dynamics and frequency dependent helicity – Journal of Physics B: Atomic, Molecular and Optical Physics 49, 23LT01 (2016) |